ABSTRACTS
HSRC/WERC Joint Conference on the Environment 1996

D. Heil¹, Z.A. Samani², A. Hanson², and S. Hu², ¹Department of Agronomy and Horticulture, New Mexico State University, Las Cruces, NM, 88003, and ²Civil, Agricultural, and Geological Engineering Department, New Mexico State University, Las Cruces, NM, 88003

Chelate extraction using ethylenediaminetetraacetic acid (EDTA) and other chelates has been demonstrated to be an effective method of removal of Pb from many contaminated soils. However, column leaching of Pb from alkaline soils with EDTA has been problematic due to extremely low soil permeability. The purpose of this study was to determine the effect of the addition of KOH and Ca(Cl)₂ to K₂H₂EDTA extraction solution on Pb removal and hydraulic conductivity. A Pb-contaminated soil was sampled from an abandoned lead-acid battery recycling facility. Both batch shaker extractions and column leaching experiments were completed using 5 different EDTA extract solutions. Addition of Ca(Cl)₂ only to K₂H₂EDTA did not change the amount of Pb removed by batch extraction. Lead solubility was observed to decrease as pH was increased by the addition of KOH. The amount of time required to leach 6.0 l of extraction solution through the soil columns varied from 2 to 33 days. The addition of Ca(Cl)₂ and/or KOH resulted in increased soil hydraulic conductivity. However, Pb removal was diminished with the addition of Ca(Cl)₂ and KOH because of decreased Pb solubility and also a shorter residence time of the extract solution in the column. The hydraulic conductivity was related to residual calcium carbonate content, suggesting that dissolution of CaCO₃ and subsequent production of CO₂ gas in soil pores was partially responsible for the observed reductions in soil permeability.

Key words: remediation, lead, soil, EDTA.

Oral presentation in metals session.

2 • CHELATING EXTRACTION AND RECOVERY OF HEAVY METALS FOR REMEDIATION OF CONTAMINATED SOIL

A. Hong and W. Jiang, Department of Civil and Environmental Engineering, University of Utah, Salt Lake City, UT, 84112

The remediation of heavy-metals-contaminated soils by chelating extraction is of significant value to industrialized nations facing the problem that resulted from economic activities including agriculture, mining, and mineral processing. Although chelating agents have been tested and known to be capable of extracting heavy metals from contaminated media, the difficulty in recovering the valuable chelating agents for reuse has rendered the technology economically less attractive. A major focus of this paper is on the recovery of chelating agents for further reuse, thereby increasing the economical viability of this technology. In this paper, results of extraction and recovery of heavy metals from a contaminated soil using various chelating agents will be reported. The results will demonstrate that: 1) many chelating agents are capable of removing heavy metals including Pb, Cu, Cd, and Zn; 2) chelating agents and the extracted heavy metals can be separately recovered; and 3) the recovered chelating agents can be reused in subsequent extraction and recovery. The accumulative removal of heavy metals in four consecutive runs amounted to 90% of the total heavy metals in one contaminated soil.

Key words: heavy metal, soil remediation, chelating extraction, recovery.

Oral presentation in metals session.

3 • DEVELOPMENT OF NOVEL AND COST EFFECTIVE POLYMERIC CHELATORS FOR APPLICATIONS IN RADIOACTIVE ACTINIDE WASTE REMEDIATION

A.S. Gopalan¹, H. Jacobs¹, P. Stark¹, N. Koshti¹, G.D. Jarvinen², B. Smith², and T. Robison², ¹Department of Chemistry and Biochemistry, New Mexico State University, Las Cruces, NM, 88003, and ²Los Alamos National Laboratory, Los Alamos, NM, 87545

A major goal of our research program is to develop polymer-supported, ion-specific extraction systems for removing radioactive actinides and other hazardous metal ions from wastewaters. This project is part of a broader effort in our laboratory to develop novel and cost effective chelators that have the high selectivity and binding constants needed to remove actinide ions such as plutonium from soils and waste streams. Selected ligands from our ongoing research efforts are being attached into polymeric backbones to create novel chelating polymers. The resultant polymers can be either water soluble or water insoluble depending on the polymeric matrix being used to anchor the ligands. A number of water soluble chelating polymers have been synthesized in our laboratory by functionalization of commercially available polyallylamine and polyethyleneimine with various ligand moieties such as hydroxamates and carboxylates. The ability of these polymers to complex with representative metal ions to give soluble complexes under different pH conditions has been examined. Both the synthesis of some chelating polymers and the results of their preliminary evaluation will be presented.

Key words: chelating polymers, actinides, remediation, radioactive.

Oral presentation in metals session.

4 • BIOSORPTION OF CADMIUM, CHROMIUM, LEAD, AND ZINC BY BIOMASS OF MEDICAGO SATIVA (ALFALFA)

J.L. Gardea-Torresdey, K.J. Tiemann, J.H. Gonzalez, and O. Rodriguez, Department of Chemistry, The University of Texas at El Paso, El Paso, TX, 79968

Previous laboratory batch experiments of Medicago sativa (Alfalfa) indicated that the African shoots population had a excellent ability to bind copper(II) and nickel(II) ions from aqueous solution. Batch laboratory pH profile, time dependency, and capacity experiments were performed to determine the binding ability of the African shoots to cadmium(II), chromium(III), chromium(VI), lead(II), and zinc(II). Batch pH profile experiments for the mentioned ions indicated that the optimum pH for metal binding is approximately 5.0. Time dependency experiments for the metal ions showed that for all the metals studied, binding to the African alfalfa shoots occurred within 5 minutes. Binding capacity experiments revealed the following amounts of metal ions bound per gram of biomass: 7.1 mg Cd, 8.7 mg Cr(III), 43 mg Pb(II), and 4.7 mg Zn(II). However, no binding occurred for chromium(VI). Nearly all of the metals studied were recovered by treatment with 0.1 M HCl, with the exception of chromium(III). Column experiments were performed to study the binding of Cd(II), Cr(III), Cr(VI), Pb(II) and Zn(II) to silica-immobilized African alfalfa shoots under flow conditions. These experiments showed that the silica-immobilized African alfalfa shoots were effective for removing metal ions from solution, and over 90% of the bound Pb(II), Cu(II), Ni(II), and Zn(II), and over 70% Cd(II), were recovered after treatment with 4 bed volumes of 0.1 M HCl. The results from these studies will be useful for a novel phytoremediation technology to remove and recover heavy metal ions from aqueous solution.

Key words: phytoremediation, alfalfa, Medicago sativa, heavy metal binding.

Oral presentation in metals session.

5 • HEAVY METAL SPECIATION AND UPTAKE IN CRAYFISH AND TADPOLES

K. Bundy, D. Berzins, L. Millet, and P. Taverna, Department of Biomedical Engineering, Tulane University, New Orleans, LA, 70118

Heavy metal pollution can have direct influence upon the biota in fragile wetland ecosystems. Different species may be differentially impacted depending upon their feeding habits, how they metabolize toxic chemical forms, and which organs are most active in metal sequestration. The studies performed here are laboratory investigations aimed at examining the uptake and bioaccumulation of chromium and lead by crayfish and tadpoles. The chromium uptake studies involved exposing red swamp crayfish (Procambarus clarkii), a bottom feeder and an animal of commercial importance in Louisiana, to Cr⁺⁶ in the form of dissolved potassium dichromate for periods of 4 and 7 weeks at 0.3, 3.0, and 30 mg/l concentrations. Control crayfish (0 mg/l) were exposed to tap water for the same periods of time. After the exposure times were reached, hepatopancreas, gill, and abdominal muscle tissue samples were collected from the crayfish. Each tissue was examined for its content of the more toxic Cr⁺⁶ and less toxic Cr⁺³ forms. Extraction methods tailored specifically for each tissue were developed that provided good recovery of the metal with minimal valence state conversion. Analysis for total chromium content in tissue was done using atomic adsorption spectroscopy (AAS). The Cr⁺⁶ content was measured using differential pulse polarography (DPP). Polarography is an electrochemical method in which reduction occurs upon an electrode, causing a current that is proportional to the concentration of the substance being reduced. The potential at which the current is maximized (the half wave potential) is unique for each oxidation state of each metal. Trivalent chromium levels were derived by the difference between total chromium and hexavalent chromium levels. The data showed chat total chromium concentration in gill tissue increases with both exposure period and concentration level reaching a maximum of 50 ppm for the 30 ppm 7 week exposure. Although total chromium concentration rose, Cr⁺⁶ concentrations in gill tissue were found to remain relatively constant at about 1.5-3.0 ppm, independent of exposure period and concentration. The data suggest there must exist a physiological mechanism in the gills to reduce hexavalent chromium to the less dangerous trivalent form when its concentration reaches a certain level. The second series of bioaccumulation studies exposed tadpoles (Xenopus laevis), which are filter feeders, to water and sediment containing concentrations of lead comparable to those found at certain sites in Devil's Swamp, near Baton Rouge, LA. Known sediment concentrations of lead were prepared utilizing sorption curve measurements for lead onto kaolin clay. A linear relationship between sediment and soaking solution concentration was observed. Tadpoles were exposed to levels of 1X, 5X, and 10X multiples of actual Pb⁺² values found in Devil's swamp water and sediment. Exposure times of 3, 5, and 6 weeks were used. The concentrations of lead in the tadpoles were ascertained using differential pulse polarography (DPP). The data showed that there was substantial lead uptake with definite biological effects. The total lead uptake was 0.84, 3.04, and 4.25 ppm for control, 5X, and 10X concentrations, respectively, at 5 weeks. Body weights were reduced by 28%, and 45% for 5X and 10X concentrations, respectively, at 5 weeks compared to controls. Developmental retardation was also observed: The controls at 5 weeks were at development stages 60-64, while the 10X group was only in the 51-54 range. Uptake and bioaccumulation of lead was seen to increase with exposure time. For example, at the 5X exposure level the lead contents at 3, 5, and 6 weeks were 1.56, 3.04, and 3.83 ppm, respectively. In conclusion, these two studies have developed methodology for examining the consequences of chromium and lead pollution of crayfish and tadpoles, based on actual conditions found in polluted areas. Polarographic speciation studies can give further insight into how heavy metals are bioaccumulated and metabolized. It is important to examine the effects of heavy metals in order to better understand the complex ecology that exists in local Louisiana wetlands, as well as globally, as it is impacted by pollution.

Key words: polarography, bioaccumulation, metal, crayfish, tadpoles.

Oral presentation in metals session.

6 • SPECIATION STUDIES AND TOXICITY ASSESSMENT OF COMPLEX HEAVY METAL MIXTURES

K. Bundy and F. Mowat, Department of Biomedical Engineering, Tulane University, New Orleans, LA, 70118

Mixtures of hazardous pollutant substances present difficult environmental problems. There are several important broad issues to consider in this regard, primarily involving identification of the chemical species present and assessment of the potential toxicity of the mixtures themselves. These issues are in fact highly linked in that different chemical forms may substantially vary in toxicity. For example, trivalent chromium has a low order of toxicity, while hexavalent chromium is highly toxic. Therefore, speciation studies may be required to understand the potential hazards associated with the mixture. In addition, the toxicity of pollutants in a mixture may be more than additive, since synergistic interactions between two components in a mixture may make the mixture more toxic than predicted by summing the effects of each individual toxicant. In this research project, the complex mixture problem is being attacked using a combination of toxicity assays and electrochemical methods. Bioluminescent bacterial assays have been successfully used previously in determining the toxicity of aquatic samples, sediments, and soils. The bioassay is based on the reduction of light emitted by a nonpathogenic strain of bacteria upon exposure to a toxic sample. In this investigation, the Microtox^R system is being used to gauge the hazards of components in heavy metal mixtures using the light-emitting marine bacterium Vibrio fischeri. By sensing changes in light output due to the presence of various concentrations of toxicants, EC50 levels can be obtained. Instrumentation consists of a Microbics 500 Toxicity Analyzer integrated with an IBM PC PS2/Model 55 and associated Microtox^R Data Capture and Reporting Program Version 7.82 software. The Microtox^R bioassay is being used in conjunction with polarographic techniques to identify specific oxidation states of heavy metals. In the polarographic method, the potential of a mercury drop substrate is changed, and the substance of interest is electrochemically reduced at the substrate surface. The magnitude of the reduction current is proportional to the reactant's concentration, and the potential at which the reduction occurs uniquely identifies the substance responsible for the current. The solution in which this process occurs is termed the supporting electrolyte. Polarographic techniques are being used in this investigation to measure Pb(II), Cr(III), Cr(VI), Cu(II), Cd(II), and As(V) concentrations in water and sediments. In addition, this methodology (which usually is not used in a multi-element mode) has been extended to mixtures of toxic heavy metals, namely solutions containing Pb(II) and Cd(II), using a single supporting electrolyte technique that allows for simultaneous measurement of multiple ions. The toxicity of various solutions containing controlled amounts of heavy metal pollutants (Pb(II), Cr(VI), Cr(III), and Cd(II)) has been measured using the Microtox^R Chronic Test System assay. Of the solutions tested, lead was found to be the most toxic with an EC50 value of 1.02 mg/l after a 5 minute exposure. For the case of chromium, the hexavalent was more toxic than the trivalent form with an EC50 approximately three orders of magnitude lower. Cadmium displayed an EC50 value of 7.9 mg/l after a 5 minute exposure indicating a lesser toxicity hazard than lead but significantly more than that of chromium. Mixtures of various ions are being tested to determine if the toxicity of the mixture is predictable from that of the individual components, and to observe whether synergistic or antagonistic reactions occur. Using sorption curve measurements on a model clay (kaolin), these studies are being extended to test the toxicity of Pb(II)-, Cr(III)-, Cr(VI)-, Cu(Il)-, and As(V)-laden sediments. This research project encompasses an intensive effort to develop methods and technologies that will help to understand the chemistry and toxicity of water, sediments, and soils contaminated by mixed wastes. The ultimate goal of the project is to evaluate the performance of the combination polarographic and Microtox^R assay method and to ascertain their capability for use under field conditions.

Key words: Microtox^R, metal mixtures, speciation, polarography.

Oral presentation in metals session.

7 • BIOREMEDIATION IN THE GEL BARRIER USING IMMOBILIZED YEAST FOR HEAVY METAL REMOVAL

E. Wilkins, Department of Chemical Engineering, University of New Mexico, Albuquerque, NM, 87106

Cu²⁺, Cd²⁺, and Zn²⁺ (all as sulfates) were used as artificial pollutant heavy metal ions to study the biosorption capacity of Saccharomyces cerevisiae yeast. The immobilized yeasts (native yeast or caustic-treated yeast) could be reactivated and reused in a manner similar to ion exchange resins. No metal biosorption capacity decrease or biomass loss were found after seven cycles. Yeast biomass immobilized in the alginate gel reduced the quantity of heavy metal binding to the biomass, as compared to biosorption by native yeast, by about 10-25%. However, yeast treated with hot alkali enhanced its heavy metal biosorption capacity significantly. Base soluble biomass which may also have metal binding capacity was reconstituted by adding acid to adjust the pH to neutral. The effects of equilibrium concentration on the biosorption capacity could be described by the Langmuir and Freundlich adsorption isotherms. Both isotherms fitted all the experimental data well except the Langmuir isotherm for Zn²⁺. For the Freundlich isotherm, it was found to be preferable to use two different sets of model parameters for different concentration regions, rather than to use one set of parameters only. The concentration change point is around 1x10^-4 M (10, 4, and 6 mg/l for Cd²⁺, Cu²⁺, and Zn²⁺, respectively). The biosorption preference series is in the order of Cu²⁺ > Cd²⁺ > Zn²⁺. The heavy metal biosorption on the immobilized caustic-treated yeast was temperature independent at lower initial metal concentration, although the biosorption rate could be affected by temperature. The initial pH of the heavy metal solution affected the metal removal efficiency significantly owing to cation competition with the hydronium ion. Cu²⁺, Cd²⁺, and Zn²⁺ biosorption by immobilized caustic-treated yeast did not occur below pH 3, but increased rapidly above pH 3, and leveled off at pH 4. The biosorption capacity almost remained constant over rather wide pH range. Incorporation of the yeast inside or on the top of the gel barrier would not only enhance the barrier capability of retarding pollutant migrations, but also adding a bioremediation potential to these migrating substances.

Key words: bioremediation, yeast, heavy metal, gel barrier.

Oral presentation in metals session.

8 • UPTAKE OF METAL IONS FROM SOLUTION BY INACTIVATED CELLS OF SYNECHOCOCCUS PCC 7942 (CYANOBACTERIA)

J.L. Gardea-Torresdey¹, J.L. Arenas², R. Webb², K.J. Tiemann¹, and J.H. Gonzalez¹, ¹Department of Chemistry and ²Department of Biological Sciences, University of Texas at El Paso, El Paso, TX, 79968

Synechococcus PCC 7942 has the ability to grow under certain stressed conditions that would kill most other bacteria. Solutions of 0.05 mM, 0.1 mM, and 0.25 mM Cu²⁺ have been inoculated with synechococcus with the idea that this cyanobacteria may develop certain defense mechanisms allowing its survival in such stressed environments. Synechococcus also has the ability to grow in mass quantity under ideal conditions, providing usable biomass at a minimal effort. Using lyophilized biomass grown under normal conditions, synechococcus was tested for its potential to bind copper, lead, and nickel ions from solution. Batch experiments were performed to determine the optimum binding pH, time dependency, and metal binding capacities for copper(II), lead(II), and nickel(II), along with desorption of the metal bound. The biomass studied showed a high affinity for all metal ions as the pH increased from 2 to 6 with optimum binding occurring at pH 5. Time dependency studies showed that this cyanobacteria had rapid binding to all three metals. Capacity experiments showed that this cyanobacteria bound 11.3 mg of copper(II) per gram of biomass, 30.4 mg of lead(II) per gram of biomass, and 3.2 mg of nickel(II) per gram of biomass. More than 90% of copper(II), lead(II), and nickel(II) metal ions were recovered when treated with 0.1 M HCl. Future studies will be performed in order to determine whether metal ion binding occurs on the cell wall surface or if the biomass is internally binding the metal ions. Synechococcus can eventually be used as the source for a novel approach in using biosystems to remediate contaminants from solution and making those contaminants available to industry through an environmentally friendly biofiltration system.

Key words: Synechococcus, cyanobacteria, heavy metal binding, bioremediation, metal recovery.

Oral presentation in metals session.

9 • MICROBIAL REDUCTION OF URANIUM USING CELLULOSIC SUBSTRATES

M. Thombre¹, B.M. Thomson¹, and L.L. Barton², ¹Department of Civil Engineering, University of New Mexico, Albuquerque, NM, 87131, and ²Department of Biology, University of New Mexico, Albuquerque, NM, 87131

Previous work at the University of New Mexico and elsewhere has shown that sulfate-reducing bacteria are capable of reducing uranium from the VI oxidation state to the IV oxidation state (referred to in this paper as U(VI) and U(IV)). The principal significance is that while U(VI) species are soluble, U(IV) is quite insoluble. Uranium(VI) generally forms a pH-dependent suite of uranyl-carbonate complexes, UO₂CO₃º, UO₂(CO₃)₂^2-, and UO₂(CO₃)₃^4- in ground water solutions which, due to their non-ionic or anionic nature, are relative mobile in most soils. In contrast, U(IV) will precipitate from solution as uraninite (UO_2(s)), coffinite (USiO_4(s)), or similar mineral phases. This chemistry forms the basis of a proposed ground water remediation strategy in which microbial reduction would be used to remove uranium from solution. One such system would consist of a permeable barrier constructed in which ground water would flow through a zone of sulfate and nitrate reducing bacteria to achieve uranium precipitation from solution. Most U(VI) reduction work to date has focused on pure cultures of sulfate-reducing bacteria using low molecular weight organic acids as the substrate. These substrates are not practical for an actual application due to their high cost and the fact that they would be quickly degraded, thus providing a very short usable life for a remediation process. Furthermore, pure culture systems are virtually never suitable for field scale application due to the impossibility of preventing contamination and growth by other microbial species. This project investigated the ability of mixed microbial populations, grown on a variety of cellulosic substrates, to provide nitrate, sulfate, and, ultimately, U(VI) reduction. Initial experiments were conducted in batch systems using a microbial consortia collected from ground water at the Shiprock Uranium Mill Tailings Remedial Action (UMTRA) project site. Five different substrates were used: non-crystalline cellulose, alfalfa hay, wheat straw, sawdust, and soluble starch. A modified minimal salts solution was used as a growth medium. Sodium bicarbonate was incorporated as a buffer in place of phosphate to prevent U(VI)-phosphate precipitation. The chemical composition of each microcosm was followed with time. Precipitates from each system was collected and the precipitated U(IV) was determined to be UO_2(s). The batch studies were followed by a series of column studies in which alfalfa hay, wheat straw, and sawdust were mixed with coarse sand to simulate a permeable barrier. The feed solution had a chemical composition similar to that of ground water at the Shiprock site. The initial hydraulic residence time in each column was 1 day. Although good nitrate reduction was found, little sulfate and U(VI) reduction was measured. The hydraulic residence time was increased to 3 days after which good removal of both sulfate and soluble U(VI) was found. At the conclusion of the column studies, solids were collected from each and subjected to mineralogical analysis. UO_2(s) was the dominant form of uranium, consistent with the batch findings. The theoretical and practical implications of this study will be presented. The results support the proposed concept of a permeable barrier which relies upon mixed culture microbial reduction of nitrate, sulfate, and U(VI) to achieve remediation of contaminated ground water.

Key words: sulfate reduction, uranium reduction, permeable barriers.

Oral presentation in metals session.

10 • REMOVAL AND RECOVERY OF COPPER AND CADMIUM BY AEROBIC MICROBIAL CULTURES GROWN WITH BIOPOLYMER STIMULATORS

K. Fukushi and S. Ghosh, Civil & Environmental Engineering Department, The University of Utah, Salt Lake City, UT, 84112

Removal of copper and cadmium and their recovery by aerobic cultures were studied using control and test stock cultures developed in chemostat reactors. The control culture was grown on a glucose-mineral salts basal medium. Test cultures were grown on the basal medium that also included selected biochemicals to stimulate the synthesis of metal-removing biopolymers. Peptone, cysteine, and beta-glycerophosphate were selected to serve as precursors of metal-complexing biopolymers. These biochemicals were expected to enhance the production of the extracellular biopolymers with high concentrations of anionic sites. Copper and cadmium uptake kinetics were evaluated by exposing samples of control and test stock cultures to copper and cadmium solutions in batch reactors at an initial metal concentration of about 50 mg/l. A modified second-order metal uptake kinetic model incorporating a metal-biopolymer dissociation function was employed to predict the observed metal-uptake rates. The proposed kinetic model fit well to experimental data. Test cultures developed on biopolymer stimulators exhibited 10% to 140% higher metal uptake rates than that of the control culture. Copper and cadmium sequestered by polymeric entities were recovered with acid or sodium bicarbonate solution. Sodium bicarbonate solution recovered heavy metal at a reasonably high recovery efficiency (87-92%) without affecting cell viability.

Key words: copper, cadmium, biouptake, kinetics, recovery.

Oral presentation in metals session.

Program One
Wednesday, May 22, 1996
Metals · Tampico Room

11 • BIOREDUCTION OF HEXAVALENT CHROMIUM IN BATCH CULTURES USING INDIGENOUS SOIL MICROORGANISMS

J.L. Bader¹, G. Gonzalez¹, P.C. Goodell¹, S.D. Pillai², and A.S. Ali², ¹Department of Geological Sciences, University of Texas at El Paso, El Paso, TX, 79968, and ²Texas A&M University Research Center, Research and Extension Center, 1380 A&M Circle, El Paso, TX, 79927

Chromium exists in the environment in two oxidation states, +3 and +6, which have very different chemical and physical properties. Hexavalent chromium exists as the chromate anion and is much more mobile and toxic than Cr(III). Biological methods for Cr reduction would be potentially less expensive than the chemical methods currently used. Soil samples collected from a Superfund Site containing 26,000 mg kg^-1 total Cr were used in batch culture studies to determine if the indigenous microbial populations were capable of mediating the reduction of Cr(VI) to Cr(III). Cr(VI) concentrations in the soil solutions were reduced 35% (from 2,000 to 1,300 mg kg^-1) under long term enrichment conditions. Fungal populations capable of aerobic Cr(VI) reduction (from 2,000 to 1,600 mg l^-1) were isolated. When soils that were not heavily contaminated with Cr(VI) were used in batch cultures containing 1,000 mg l^-1 Cr(VI), concentrations were reduced by as much as 22% within 7 days. This data suggests that the genetic potential for chromate reduction may be present in soil microorganisms irrespective of whether they have any previous history of Cr(VI) exposure.

Key words: chromate, hexavalent chromium, bioreduction, bioremediation, Superfund.

Oral presentation in metals session.

12 • MOBILE CHROMATE TO IMMOBILE PRECIPITATE-SUBSURFACE REACTIVE WALL SCENARIOS

R.M. Powell¹ and R.W. Puls², ¹ManTech Environmental Research Services Corporation, R.S. Kerr Laboratory, P.O. Box 1198, Ada, OK, 74821-1198, and ²National Risk Management Research Laboratory, USEPA, P.O. Box 1198, Ada, OK, 74821-1198

Chromate (CrO₄^2-) is a toxic, carcinogenic, and highly mobile anionic contaminant that is found in many subsurface systems. It is not strongly adsorbed but is relatively easily reduced from Cr⁶⁺ to Cr³⁺. When reduced, the chromium becomes much less toxic and its mobility is diminished or eliminated by increased adsorption and the formation of hydroxide precipitates. Some aquifers have natural reduction capacity that is sufficient to lower the total chromate concentration, but this capacity may or may not be sufficient to protect sensitive receptors downgradient. Recently it has been shown that chromate can be reduced in the presence of metallic (i.e. zero-valence-state) iron. This results in a chromium-iron hydroxide solid solution, yielding extremely low Cr activity at the solid/aqueous interface. It has also been demonstrated that chlorinated hydrocarbons can undergo reductive dechlorination on iron surfaces. Iron-containing permeable reactive subsurface barriers have been proposed for intercepting and remediating plumes of both types. Iron is a relatively inexpensive and readily available element, making it a nearly ideal candidate for installation in such walls. There is also data, however, that indicates significant differences in the reactivities of various purities and formulations of iron, as well as the effects of the geochemical milieu on overall system reactivity. Numerous experiments have been performed evaluating chromate reduction by various iron forms and other metals under differing geochemical environments.

Key words: zero-valent iron, chromate, ground water remediation, geochemistry, subsurface reactive barriers.

Oral presentation in metals session.

13 • REMEDIATION OF CHROMATE-CONTAMINATED GROUND WATER USING ZERO-VALENT IRON: FIELD TEST AT USCG SUPPORT CENTER, ELIZABETH CITY, NORTH CAROLINA

R.W. Puls¹, C.J. Paul¹, and R.M. Powell², ¹National Risk Management Research Laboratory, USEPA, P.O. Box 1198, Ada, OK, 74820, and ²ManTech Environmental Research Services Corporation, P.O. Box 1198, Ada, OK, 74820

A field test was conducted near an old hard-chrome plating facility on the USCG Support Center near Elizabeth City, North Carolina, to evaluate the in situ remediation of ground water contaminated by hexavalent chromium. The remedial effectiveness of this innovative in situ technology was monitored over a one year period. The success of this small-scale test has prompted a full-scale implementation of the technology at the site for late spring 1996. (This is an abstract of a proposed presentation and does not necessarily reflect EPA policy.)

Key words: zero-valent iron, in situ reactive barrier walls, chromate, ground water remediation, geochemistry.

Oral presentation in metals session.

14 • CALCIUM AND MAGNESIUM INTERFERENCE STUDIES FOR THE BINDING OF HEAVY METAL IONS IN SOLUTION BY MEDICAGO SATIVA (ALFALFA)

J.L. Gardea-Torresdey, K.J. Tiemann, J.H. Gonzalez, and O. Rodriguez, Department of Chemistry, University of Texas at El Paso, El Paso, TX, 79968

Previous batch laboratory experiments performed to determine the potential ability of seven different varieties of Medicago sativa (Alfalfa ) revealed that the African shoots population was able to efficiently bind copper(II) and nickel(II) from aqueous solutions. Batch laboratory interference studies were performed with various calcium and magnesium concentrations (0.2 mM-0.2 M) in order to ascertain the effects of these ions on the heavy metal binding ability of African alfalfa shoots. Results from these studies have shown that calcium and magnesium did not greatly reduce the binding of cadmium(II), copper(II), lead(II), nickel(II), and zinc(II) to African alfalfa shoots. However, high concentrations of calcium and magnesium significantly reduced chromium(III) binding to African shoots. In addition, all these experiments were repeated maintaining the ionic strength constant and similar results were obtained. Further studies are being conducted in order to determine if the same effects can be seen under flow conditions with silica immobilized African alfalfa shoots. The information obtained from these studies will be useful for an innovative method of heavy metal ion removal and recovery from contaminated waters.

Key words: bioremediation, alfalfa, Medicago sativa, interference, heavy metal binding.

Oral presentation in metals session.

15 • THE EFFECT OF VEGETATION ON THE TRANSPORT OF HEAVY METAL IN A CONTAMINATED SOIL: A COLUMN STUDY

S.R. Burckhard¹, A.P. Schwab², and M.K. Banks¹, ¹Department of Civil Engineering, and ²Department of Agronomy, Kansas State University, Manhattan, KS, 66506

Vegetation grown in contaminated soils may provide various pathways for the transport of heavy metals, including preferential flow paths, chelation of metals by root exudates, adsorption/desorption, and precipitation/dissolution reactions. This column study, designed to simulate field conditions, investigates the changes in the soil's physical and chemical properties due to the presence of vegetation. Changes in the water content of the soil will be quantified as a function of time along with the growth of the plants' roots. Leachate will be collected and the heavy metal solution species will be quantified. The collected data will be used to assess the overall transport of heavy metal within and out of the vegetated contaminated soil system.

Key words: vegetation, heavy metal, transport, geochemistry.

Oral presentation in metals session.

16 • APPLICATIONS OF PERMEABLE BARRIER TECHNOLOGY TO GROUND WATER CONTAMINATION AT THE SHIPROCK, NM, UMTRA SITE

B.M. Thomson, E.J. Henry, and M. Thombre, Department of Civil Engineering, University of New Mexico, Albuquerque, NM, 87131

The Shiprock uranium mill tailings pile in far northwestern New Mexico consists of approximately 1.5 million tons of uranium mill tailings from an acid leach mill which operated from 1954 to 1968. Located on land owned by the Navajo Nation, it was one of the first tailings piles stabilized under the Uranium Mill Tailings Remedial Action (UMTRA) project. Stabilization activities were completed in 1986 and consisted principally of consolidating the tailings, contouring the pile to achieve good drainage, and covering the pile with a multi-layer cap to control infiltration of water, radon emanation, and surface erosion. No ground water protection or remediation measures were implemented other than limiting infiltration of water through the pile, although a significant ground water contamination plume exists in the flood plain adjacent to the San Juan River. The major contaminants at the Shiprock site include high concentrations of sulfate, nitrate, arsenic, and uranium. One alternative for remediation may be the use of a permeable barrier in the flood plain aquifer. As proposed for the Shiprock site, the permeable barrier would be a trench constructed in the flood plain that would be backfilled with a media that is permeable to ground water, but would intercept or degrade the pollutants. Work to date has focused on use of a mixed microbial population of sulfate- and nitrate-reducing organisms. These organisms would produce strongly reducing conditions which would result in precipitation of the metal contaminants (i.e., As(V) and U(VI)) in the barrier. One of the first considerations in designing a permeable barrier is developing an understanding of ground water flow at the site. Accordingly, a steady state numerical model of the ground water flow at the site was developed using the MODFLOW code developed by the U.S. Geological Survey. This model was calibrated using data collected at a suite of monitoring wells at the Shiprock site, and then used to simulate a variety of hydraulic alternatives. These alternatives included use of permeable barriers, use of a combination of impermeable and permeable barriers to achieve a "funnel and gate" effect, and manipulation of the hydraulic gradient in the flood plain through use of infiltration trenches to increase contaminant migration rates. A preliminary ranking system was developed to allow comparison of these alternatives which included length of the barriers, ground water velocities (and therefore aquifer flushing rates), and hydraulic gradient manipulation considerations.

Key words: ground water remediation, permeable barriers, modeling.

Oral presentation in metals session.

17 • AN ELECTROCHEMICAL APPROACH FOR INVESTIGATING CORROSION OF SMALL ARMS MUNITIONS IN FIRING RANGES

K. Bundy, M. Bricka, and A. Morales, Environmental Laboratory, U.S. Army Engineer Waterways Experiment Station, Vicksburg, MS, 39180-6199

Spent small arms munitions have been accumulating for decades at firing ranges operated by the DoD, law enforcement agencies, and commercial firms. Since 1) in many cases the used bullets are outdoors and subjected to weathering and other sources of moisture, 2) many munitions use lead alloys in their construction, and 3) the toxicity associated with lead is well documented, there is increasing concern that these accumulations represent a potential source of pollution to water and soil. To guide both assessments of the severity of this problem and potential remediation efforts at particular sites, it is necessary to quantify how rapidly bullets are actually corroding and to learn about the soil variables which foster electrochemical dissolution of munitions. The corrosion behavior of iron and steel alloys in soils is well known, due to the importance of this topic to the gas industry. Much less information is available about the performance of lead alloys in soil, however, and no prior studies have documented investigations of the rate of corrosion of bullets exposed to soil conditions. This research project was undertaken to start to remedy these deficiencies. The situation experienced by spent copper-jacketed lead bullets in soil suggests that both galvanic corrosion and crevice corrosion mechanisms can occur in certain circumstances. To allow these mechanisms to be potentially operative and to facilitate linear polarization measurements, in this study M16 bullets were sectioned longitudinally and an insulated copper wire was attached. The bullets were buried in a corrosion cell containing samples of soil taken from Louisiana army firing ranges. Four environmental conditions were investigated to simulate possible situations in which bullets could be exposed to moisture in the field: rain water, acid rain, sea water, and a 50% sea water/50% acid rain mixture. The soil moisture content was adjusted to either 15% or saturation using a Denver Instrument Co. IR-100 Moisture Analyzer. These conditions span a rather wide range of soil corrosive aggressiveness and allow the generality of the techniques used here to be assessed. The three electrode technique was used to measure the corrosion response of four samples for each moisture content/type condition listed above. Graphite rods were used for the counter electrodes, and a saturated calomel electrode was used as the reference. A specially constructed salt bridge was used to make the connection between the reference electrode and the soil environment. The electrochemical measurements themselves were conducted using a computer-controlled EG&G PARC Model 273A potentiostat and M270 and Headstart software packages. For accurate corrosion rate determinations in environments of high ohmic resistance such as soil, it is essential that the value of the electrical resistance R₀ of the soil be measured. This allows compensation for the soil resistance contribution to the nominal polarization resistance to be made. In this study the soil resistance was first determined by applying a potential pulse to the bullet and doing chronoamperometric monitoring. The polarization resistance (compensated for R₀ as described above), R_p, was then measured. Finally a potentiodynamic polarization curve measurement was taken. From the latter measurement, corrosion current I_c (a direct measure of the rate of corrosion) could be determined using Tafel extrapolation. The anodic and cathodic Tafel slopes, B_a and B_c respectively, were determined via the linear regression routine of a Quattro Pro for Windows software package. This allowed the corrosion current also to be estimated via the Stern-Geary equation: I_c = (1/(2.3 R_p))(B_aB_c)/(B_a + B_c). Corrosion potential E_c was available from these measurements and from the Headstart program. Corrosion currents of the bullets were observed to sensitively depend on environmental conditions. The rate of corrosion was found to increase with decreasing pH and increasing chloride and moisture contents. The chloride content was the most influential of these variables. High soil resistance and noble corrosion potential were found to be associated with low corrosion rates. This is an important result since both soil resistivity and potential can be readily measured under field conditions. These tests have demonstrated the validity and utility of employing electrochemical techniques to gain insight into the corrosion of small arms munitions in soil. Tests involving long-term exposure of bullets to these and other soil corrosion environments and measurements of resulting weight loss are ongoing. Comparison of these two types of measurements will allow the usefulness of electrochemical methods for predicting the corrosiveness of different soil and precipitation/moisture conditions to be determined. Eventually it is hoped that this work will lead to test methods to be used in the field which will allow the status of and hazards posed by corroding munitions in soil to be assessed. Acknowledgment: This paper is based upon research sponsored by the U.S. Army Corps of Engineers and the U.S. Army Environmental Center. Permission to publish this material was granted by the Chief of Engineers.

Key words: bullets, corrosion, soil, electrochemical techniques.

Oral presentation in metals session.

18 • THE TRANSPORT OF ZINC IN SOIL AS AFFECTED BY CITRATE

Y. He¹, A.P. Schwab², and M.K. Banks¹, ¹Department of Civil Engineering, and ²Department of Agronomy, Kansas State University, Manhattan, KS, 66506

Low molecular weight organic acids released by plant roots or soil microbes may affect the adsorption of heavy metals by soils, and thereby influence the fate and transport of heavy metals in soils. A soil column experiment was conducted to investigate the effect of citrate, an important organic ligand released by plant roots, on the movement of zinc in soil. Solutions with 750 mM Zn and varying concentrations of citrate ranging from 0 to 5,000 mM were pumped continuously through the columns at a flow rate of 0.16 ml min^-1. Column effluent was collected daily and measured for Zn, Fe, Ca, and citrate. Finally, the columns were cut to four sections, and a sequential extraction experiment was performed for each section in order to investigate zinc-retaining mechanisms, to assess the distribution of zinc in soil columns, and to obtain a mass balance of zinc. The results showed that zinc transport rate decreased, and the zinc-retaining capacity of soil increased with increasing citrate concentration. This may be due to the citrate serving as a substrate for soil microbes and the increase of biomass in soil-enhanced zinc-retaining capacity.

Key words: zinc, citrate, transport.

Oral presentation in metals session.

19 • A COMPUTER MODEL FOR REMOVAL OF LEAD FROM CONTAMINATED SOILS

Z.A. Samani, D. Heil, S. Hu, and A. Hanson, Civil Engineering Department, New Mexico State University, Las Cruces, NM, 88003

Lead contamination of soils is a common problem throughout the world. Laboratory batch test and bench scale experiments have shown that EDTA can be used to remove lead from contaminated soils. However, due to the high cost and laborious task associated with actual environmental remediation of a lead-contaminated soil, there is a need to be able to predict the outcome of a remediation process in advance in order to optimize the process and minimize the cost. This paper describes the development and validation of a computer model which can be used to simulate the removal of lead from a contaminated soil column using EDTA as the chelating agent. The model is able to simulate the lead removal from soil based on equilibrium as well as kinetic dissolution model. The comparison of the simulated results with actual lead concentrations both in effluent and soil shows that the model can predict the lead removal process with reasonable accuracy.

Key words: soil remediation, lead, modeling, environment.

Oral presentation in metals session.

20 • ON CONDUCTIVITY OF SOILS WITH PREFERENTIAL FLOW PATHS

J. Lin and R.S. Govindaraju, Department of Civil Engineering, Kansas State University, Manhattan, KS, 66502

Laboratory soil column experiments were conducted to study the distribution of preferential flow paths resulting from removal of colloidal size clay particles. These experiments studied the influence of clay (kaolinite) percentage in sand-clay mixtures and the effect of hydraulic gradients on pore evolution. Analysis of the effluent during the experiments indicated that clay particles were removed from the soil column, accompanied by an increase in porosity and hydraulic conductivity. Dye experiments were conducted on the same columns to stain the pathways where colloidal particle removal occurred. Pore formation was fairly uniform in some cases, while other cases showed distinct preferential flow path formation. A physically-based model was used to identify a dimensionless parameter, G, which expresses the ratio of detachment and deposition forces at any space-time location. A model, based on equivalent media theory, is proposed to describe the hydraulic conductivity of such soils. The theoretical expressions for conductivity and the relationship between G and the equivalent conductivity for such soils will be explored.

Key words: modeling, preferential flow, hydraulic conductivity, colloidal clay particle, equivalent media theory.

Oral presentation in metals session.

21 • MODELING HEAVY METAL MOVEMENT IN A ROOTED SOIL

P. Huizenga and J.C. Tracy, Northern Great Plains Water Resources Research Center, South Dakota State University, Brookings, SD, 57007

Prediction of the movement of heavy metals through a rooted soil requires an understanding of both the hydrogeology and geochemistry of a site. Current models describing the transport of dissolved constituents through a rooted soil have been developed and shown to provide reliable predictions. Geochemical models that predict equilibrium states for a heavy metal in a soil-water environment have also been developed and shown to be useful. However, incorporating a geochemical model into a soil-water transport model is impractical in many situations due to the highly non-linear behavior of geochemical models. An alternative to incorporating a full geochemical model into a solute transport model is to use an empirical model representation of the immobile and mobile phases of the heavy metal, which is calibrated using the geochemical model. Using this approach we developed an empirical model for lead using the MINTEQA2/PRODEFA2 geochemical assessment model for incorporation into a root-zone fate and transport model, BIOROOT.

Key words: heavy metal, vegetative remediation, adsorption.

Oral presentation in metals session.

22 • EFFECT OF VEGETATION ON CONTAMINANT TRANSPORT IN SURFACE FLOWS

R. Green¹, R.S. Govindaraju¹, L.E. Erickson¹, and L. Roig², ¹Departments of Chemical and Civil Engineering, Kansas State University, Manhattan, KS, 66506, and ²U.S. Army Corps of Engineers Waterways Experiment Station, 3909 Halls Ferry Road, Vicksburg, MS, 39180

It is well known that vegetation reduces contaminant transport in surface flows. The beneficial effects of grasses and trees will be reviewed with an emphasis on factors that can reduce or prevent the movement of heavy metals in mine tailings from being transported in surface flows associated with precipitation events. Available mathematical models for sediment transport in surface flows will be reviewed. Experimental and field data on contaminant transport in surface flows will be identified and evaluated.

Key words: surface water, metal, sediments, vegetation.

Oral presentation in metals session.

23 • UNSATURATED POROUS MEDIA FLOWS ABOUT NON-PARTICIPATING FRACTURES

S.R. Subia¹, M.S. Ingber¹, and M.J. Martinez², ¹Department of Mechanical Engineering, University of New Mexico, Albuquerque, NM, 8713 l, and ²Engineering Sciences Center, Sandia National Laboratories, Albuquerque, NM, 87185

Many of the flows observed in surface rock formations are unsaturated flows through a medium containing fractures. In cases where the fractures are small and non-connective one finds that flow may not even occur within the fractures themselves. Under these conditions the fractures do not participate in the background flow, but instead act as barriers which impede the flow in the underlying matrix. From a computational point of view, discrete modeling of these fractures in flow simulations is impractical not only because of the small size of the fractures, but also because the fractures represent singularities in the flow field. In general, the background flow through unsaturated porous media is highly nonlinear because of the strong dependence of the hydraulic conductivity on the suction head. For analytical studies, a two-parameter exponential model for the conductivity has been used in conjunction with a Kirchoff transformation to cast the nonlinear governing equation into a linear form which is more amenable to solution. In this research we analyze some simple problems using a boundary element numerical implementation of this transformation approach and attempt to characterize the influence of small non-connective fractures on the effective hydraulic conductivity of the medium.

Key words: fracture, unsaturated porous media flows.

Oral presentation in metals session.

Program One
Thursday, May 23, 1996
Munitions-Contaminated Soil · Tampico Room

24 • TNT BREAKTHROUGH CURVES FOR AQUIFER MATERIALS FROM THE LOUISIANA ARMY AMMUNITION PLANT, SHREVEPORT, LA

T.E. Myers and D.M. Townsend, U.S. Army Engineer Waterways Experiment Station, 3909 Halls Ferry Road, Vicksburg, MS, 39180

The Louisiana Army Ammunition Plant (LAAP) produced ammunition for World War II, the Korean Conflict, and the Vietnam Conflict. Some ground waters at LAAP contain as much as 10 mg/l of 2,4,6-trinitrotoluene (TNT). Ground water contamination with explosives at LAAP was caused by disposal of explosive-laden wastewaters into unlined surface impoundments. The potential for plume advancement off the LAAP boundaries is a major concern. TNT breakthrough curves (BTCs) for four aquifer materials from LAAP were obtained under steady flow conditions using packed columns 15.2 cm in length and 4.45 cm in diameter. Several TNT reductive transformation products (monoamino-dinitrotoluenes, diamino-nitrotoluenes, and azoxytoluenes) were also measured. An advection-dispersion model with linear equilibrium-controlled sorption and first-order decay was fit to the TNT BTCs. BTCs showed that TNT was highly mobile in all four aquifer materials. Analysis of sectioned columns showed no retention of TNT or TNT transformation products by the aquifer materials. Trace amounts of monoamino-dinitrotoluenes were eluted, but no diamino-nitrotoluenes or azytoluenes were eluted. In general, retardation by sorption was low, and disappearance (reductive transformation, irreversible sorption, etc.) was almost negligible. The TNT BTCs for LAAP aquifer materials are in sharp contrast to TNT BTCs obtained in previous studies of soils from Vicksburg, MS, in which reductive transformation to diamino-nitrotoluenes accounted for sixty percent of the TNT introduced to soil columns. The mobility difference for LAAP aquifer materials and Mississippi soils is hypothesized to be caused by differences in aquifer material or soil oxidation-reduction potential under saturated conditions.

Key words: trinitrotoluene, ground water, sorption, transformation, transport.

Oral presentation in munitions-contaminated soil session.

25 • PEROXONE TREATMENT OF EXPLOSIVES-CONTAMINATED GROUND WATERS

M.E. Zappi¹, J. Miller², E. Toro², R. Cerar³, and R. O'Donnell³, ¹Department of Chemical Engineering, Mississippi State University, Starkville, MS, and ²USAE Waterways Experiment Station, Vicksburg, MS, and ³U.S. Army Environmental Center, Edgewood Arsenal, MD

The U.S. Department of Defense has numerous sites that contain ground water that has been contaminated with explosive compounds due to past military activities. Current technology for remediation of these ground waters are activated carbon and UV-based chemical oxidation. Recent efforts within the Department of the Army research community has resulted in the development of peroxone oxidation for treating explosives-contaminated ground waters. Peroxone utilizes the reaction between ozone and hydrogen peroxide, which forms the hydroxyl radical, to destroy aqueous-based contaminants. This ozone-hydrogen peroxide reaction does not require ultraviolet light; thereby, it may be considered a "dark" oxidation process. Recently, our research team using bench-scale reactors compared the removal rates of TNT, RDX, HMX, and TNB obtained by various candidate advanced oxidation processes (including peroxone). These results indicated that peroxone was quite competitive in terms of the rate and completeness of contaminant removal to the other more traditional UV-based AOPs. Based on the positive bench results, a pilot-scale peroxone system was operated at Cornhusker AAP. Results of this effort indicated that an optimum ratio of hydrogen peroxide-ozone of 0.3 produced an effluent acceptable quality within 30 minutes of treatment. This presentation will summarize both the bench- and pilot-scale activities with particular emphasis placed on process optimization.

Key words: peroxone, explosives, ground water, process optimization.

Oral presentation in munitions-contaminated soil session.

26 • FEDERAL INTEGRATED BIOTREATMENT RESEARCH CONSORTIUM: FLASK TO FIELD

K.T. Preston, Army Corps of Engineers, Waterways Experiment Station, Vicksburg, MS, 39180

Composting is currently being considered, piloted, or demonstrated for use as a bioremediation technique for many types of contaminated soils. The current status of composting of explosives, heavy poly-aromatic hydrocarbons (PAHs), polychlorinated biphenyls (PCBs), and chlorinated solvents contaminated soils will be discussed. Relevant process principles involving microbial kinetics, mass and heat transfer, and energy balances will be developed and examined. From the completed investigations of explosive-contaminated soils a step-by-step bench-scale protocol has been written (in editing) to support the development of composting for other contaminants in the future based on earlier contaminated soils investigations. Overall outlook for composting will be discussed.

Key words: composting, bioremediation, explosives.

Oral presentation in munitions-contaminated soil session.

27 • SCREENING FOR REMOVAL OF TNT AND RDX BY SUBMERSED AND EMERGENT PLANT SPECIES FROM CONTAMINATED GROUND WATER

E.P.H. Best¹, M.E. Zappi², H.L. Fredrickson², S.L. Larson², S. Sprecher², and J. Miller², ¹AScI Corporation, 3402 Wisconsin Avenue, Suite #5, Vicksburg, MS, 39180, and ²U.S. Army Corps of Engineers, Waterways Experiment Station, Vicksburg, MS, 39180

The differential ability of aquatic plant species to remove TNT and RDX from explosives-contaminated ground water was investigated under laboratory conditions. Two screening experiments were performed, utilizing contaminated ground water from Department of Defense ammunitions plants (AAP). TNT and RDX concentrations from the Milan AAP were 2,200 and 3,000 µg l^-1, and at the Iowa AAP, 700 and 13,000 µg l^-1, respectively. In each experiment 10 plant species were incubated with ground water for 10 days. Water without plants or sediment, and water with autoclaved and unautoclaved sediment served as controls. The concentrations of the contaminants in the water were monitored regularly. All plant species significantly increased amount and rate of TNT removal over that in water alone. The most effective species were elodea, sago pondweed, Eurasian watermilfoil, stonewort, curlyleaf pondweed, waterstargrass, and reed canary grass. Removal curves were extrapolated to the EPA-mandated potable water level of 2 µg l^-1 to calculate the residence time requirements for TNT clean-up. Clean-up periods in the screening using MAAP ground water were 56 days for water without plants or sediment, 16 to 56 days for water with sediment, and 4 to 5 days for submersed plants at a density of 9 g fr wt l^-1. Here N amendment stimulated TNT removal. Clean-up periods in the Iowa AAP screening were 61 days for water without plants or sediment, 31 for water with sediment, and 2 to 49 days for water with submersed/emergent plants present. Correlation analysis indicated that TNT removal from water is plant-mediated, and that required residence time decreases with increasing plant biomass. Plant effects on RDX removal were more variable and an order of magnitude slower than in TNT. The most effective species were sago pondweed, Eurasian watermilfoil, parrotfeather, curlyleaf pondweed, reed canary grass, fox sedge, and common arrowhead. Estimates of predicted residence times for clean-up to 2 µg l^-1 in the MAAP study were 627 days for water without plants or sediment, and 50 to 297 days for water with plants. In the IAAP study, residence times for clean-up were 91 days for water without plants or sediment, 39 to 51 days for water for sediment, and 39 to 75 for water with plants. Correlation analysis indicated that RDX removal from water was not directly plant-mediated; however, the required residence time for this explosive increased with oxygen concentration in water. This suggests the potential involvement of facultative and/or obligate anaerobic microorganisms in RDX removal, or the existence of non-aerotolerant enzymes. Indications of reductive metabolic pathways of TNT were detected in incubation water and plant material.

Key words: ground water, explosives, phytoremediation, constructed wetlands.

Oral presentation in munitions-contaminated soil session.

28 • BIOREMEDIATION OF SOLID TNT PARTICLES IN A SOIL SLURRY REACTOR: MASS TRANSFER CONSIDERATIONS

P.C. Gilcrease, V.G. Murphy, and K.F. Reardon, Department of Chemical and Bioresource Engineering and Center for Environmental Toxicology and Technology, Colorado State University, Ft. Collins, CO, 80523

The bioremediation of 2,4,6-trinitrotoluene (TNT) contaminated soils is complicated by the fact that TNT is often present in the form of solid particles as large as 1 cm in diameter. Since biodegradation is an aqueous phase process, the dissolution of solid TNT particles can limit the overall treatment rate. Slurry-phase reactors can be used to enhance the biodegradation of solid TNT particles since dissolution rates are increased with agitation. The focus of this research was the effect of solid/liquid mass transfer on the slurry phase biotreatment of solid TNT particles. Special emphasis was placed on the effects of particles other than TNT. Soil slurry bioreactors contain up to 50 wt% solids, most of which are soil particles rather than TNT. Non-TNT solids (soil) can potentially affect the biodegradation of TNT solids in three ways: 1) changes in kLa due to slurry properties and TNT particle attrition, 2) biofilm resistances due to association of the biomass with the solid phase, and 3) sorption of TNT by other solids. In this study, the first two processes were investigated using idealized experimental systems; their importance in real soil slurry bioreactors is discussed. Results indicate that attrition of TNT particles can significantly increase the overall degradation rate.

Key words: trinitrotoluene, bioremediation, soil slurry bioreactor, mass transfer.

Oral presentation in munitions-contaminated soil session.

29 • PHYTOREMEDIATION OF TNT-CONTAMINATED WATER: BENCH-TOP FLOW THROUGH REACTOR STUDIES

V.F. Medina¹, S.C. McCutcheon², and N.L. Wolfe², ¹National Research Council and ²U.S. Environmental Protection Agency, USEPA-NERL, 960 College Station Road, Athens, GA, 30605

The degradation of trinitrotoluene (TNT) in water using plant enzymes was investigated. An integrated approach using batch experiments and continuous plug flow reactors was used. Kinetic parameters were investigated at different contaminant loading rates. Breakdown product accumulation and destruction were monitored. The experiments provided information for upscaling the process to create full-scale phytoremediation wetland reactors.

Key words: phytoremediation, trinitrotoluene, explosives, munitions, remediation.

Oral presentation in munitions-contaminated soil session.

Program Two
Tuesday, May 21, 1996
Chemical Technologies · Cozumel Room

30 • CARBON TETRACHLORIDE DECHLORINATION IN WATER USING BINARY METAL SYSTEMS

T. Boronina, I. Lagadic, and K.J. Klabunde, Department of Chemistry, Kansas State University, Manhattan, KS, 66506

Carbon tetrachloride dechlorination in water has been investigated in the presence of zinc nanoparticles and zinc particles doped with silver, palladium, and nickel. Gas chromatography, mass spectrometry, infrared spectroscopy, powder x-ray diffraction spectroscopy, and Atomic Force Microscopy (AFM) were used to follow the reaction progress. AFM studies of the zinc surface (Zn dust pressed in pellet at 7,000 psi) have demonstrated consecutive surface change during the carbon tetrachloride degradation. Before the reaction the surface "macrostructure" appeared to be quite regular and consisted of units 3-8 mm in diameter. In addition, there were particles about 100 nm in diameter on the top of each unit. Over the course of the reaction particle size on the top of the units increased and later further erosion of the units took place.

Key words: carbon tetrachloride, dechlorination, water, metal particles, Atomic Force Microscopy (AFM).

Oral presentation in chemical technologies session.

31 • DECHLORINATION OF TRICHLOROETHYLENE BY ZERO-VALENT METALS IN AQUEOUS ENVIRONMENTS

W. Li, K.J. Klabunde, T. Boronina, D. Zhang, and I. Lagadic, Department of Chemistry, Kansas State University, Manhattan, KS, 66506-3701

Electroactive metals, for example Zn, especially reactive forms such as cryo-Zn may participate in reductive dechlorination of chlorocarbons under neutral pH conditions. This can be useful when dealing with persistent ground water contaminants, in particular trichloroethylene (TCE). We have studied this process in some detail, and have found the major degradative products are the dichloroethene isomers, plus smaller yields of some other chlorinated hydrocarbons. The enhanced reactivity of Zn as promoted by other metals and bimetallic forms, and the multiple degradation pathways will be discussed. Investigation of morphological changes by Atomic Force Microscopy will also be reported.

Key words: trichloroethylene, trichloroethane, dichloroethene, dechlorination, reduction.

Oral presentation in chemical technologies session.

32 • DECHLORINATION OF CARBON TETRACHLORIDE WITH IRON: CARBON MASS BALANCE AND EFFECT OF OXYGEN ON DECHLORINATION PATHWAYS

B.R. Helland, P.J.J. Alvarez, and J.L. Schnoor, The University of Iowa, Iowa City, IA, 52242

Abiotic dechlorination of carbon tetrachloride (CCl₄) with zero-valent iron (Fe⁰) has been reported. Nevertheless, the chemistry of the iron surface and the effect of dissolved oxygen (DO), often present in ground water and industrial effluents, in determining dechlorination rates and products have not been well defined. Furthermore, a complete mass balance on carbon has proven elusive, prohibiting the determination of the ultimate fate of CCl₄. CCl₄ dechlorination with two distinctly different Fe⁰ materials was observed under three DO concentrations in continuously-mixed batch reactors. Reaction rates and products were monitored during the dechlorination reactions to investigate the interaction between different Fe⁰ surfaces, CCl₄, and DO. The primary identified products of CCl₄ dechlorination were CHCl₃, CH₂Cl₂, CO₂, and CO. An unidentified end product and at least one transient product were also observed, and efforts to identify and quantify these compounds continue in our laboratory. In addition, a small amount of chlorinated residue was found on the Fe surface. This residue contained a number of distinct compounds which were tentatively identified as short chain polychlorinated alkanes and alkenes. The mass balance on C₁compounds and the distribution of dechlorination products under the various reaction conditions employed are discussed. A significant difference in dechlorination rates between the two Fe substrates was observed. Both the surface area and chemical composition of the surface appear to be factors in the reactivity of the substrate. DO initially present in the reactors significantly influenced the dechlorination rates and the distribution of dechlorination products. The presence of DO apparently resulted in the oxidation of reaction intermediates, as indicated by the generation of more CO and CO₂ under initially oxic conditions. DO also oxidized the Fe surface, slowing the dechlorination process.

Key words: carbon tetrachloride, iron, dechlorination, oxygen, fate.

Oral presentation in chemical technologies session.

33 • CHLOROFORM TRANSFORMATION BY A METHANOGENIC CONSORTIUM UTILIZING ZERO-VALENT IRON AS ULTIMATE ELECTRON DONOR

L.J. Weathers, G.F. Parkin, and P.J.J. Alvarez, Department of Civil and Environmental Engineering, The University of Iowa, Iowa City, IA, 52242

Chloroform (CF) was rapidly transformed in methanogenic incubations fed zero-valent iron as the sole electron donor. Pseudo-first order rate constants were at least twenty times greater in incubations containing 40-mesh iron filings and methanogenic cell suspension compared to incubations containing iron and autoclaved cell suspension, iron and cell-free supernatant, and cell suspension only. An acetate-enriched, mixed, methanogenic culture was used as a source of cell suspension. Apparently, methane production was supported by water-derived hydrogen produced by anaerobic corrosion of the added iron. Replacing the N₂/CO₂ headspace in iron-free cell suspension bottles with H₂/CO₂ headspace increased rates of methanogenesis and CF transformation. Dichloromethane (DCM) was produced concurrent with CF degradation in iron-cell suspension incubations, but at less than equimolar amounts. Methane production in bottles containing iron and cell suspension decreased when amended with CF, indicating inhibition of methanogenesis by CF. Bromoethanesulfonate (BES), a methanogen-specific inhibitor, inhibited methanogenesis and CF transformation when added to cell suspension bottles with a H₂/CO₂headspace. BES also inhibited methanogenesis when added to iron-amended cell suspension with an initial N₂/CO₂ headspace. Vancomycin, an inhibitor of eubacteria, had no effect when added, discounting the potential involvement of homoacetogens. In column reactors with an influent CF concentration of about 1.5 mM, CF was nondetectable in the effluent of a column reactor packed with steel wool and seeded with methanogenic cell suspension, while the CF concentration in a similar column not seeded with methanogenic cell suspension averaged about 0.4 mM. These results suggest that methanogens can couple the anaerobic biocorrosion of elemental iron with the biodehalogenation of CF, and that this process is sustainable.

Key words: bioremediation, zero-valent iron, chloroform.

Oral presentation in chemical technologies session.

34 • DESTRUCTIVE ADSORPTION OF CHLOROCARBONS ON CALCIUM OXIDE

O. Koper, I. Lagadic, and K.J. Klabunde, Chemistry Department, Kansas State University, Manhattan, KS, 66506

The destructive adsorption of carbon tetrachloride and trichloroethylene on two types of calcium oxide was studied. The intrinsic differences between the nanoscale, autoclave-prepared calcium oxide (AP-CaO) and conventionally-prepared calcium oxide (CP-CaO), such as the number and the nature of hydroxyl groups on the surface, the morphology of the surface, and the particle size, were determined. Decomposition ability and the products were studied by various techniques, including gas chromatography, mass spectrometry, powder x-ray diffraction spectroscopy, elemental analysis and infrared spectroscopy. Infrared spectroscopy was also used to observe the interactions between the chlorocarbon and the oxide.

Key words: calcium oxide, chlorocarbon, decomposition.

Oral presentation in chemical technologies session.

35 • DESTRUCTIVE ADSORPTION OF 2-CHLOROETHYL ETHYL SULFIDE BY MAGNESIUM OXIDE

E.M. Lucas and K.J. Klabunde, Department of Chemistry, Kansas State University, Manhattan, KS, 66506

Studies were performed to look at the potential use of nanoscale MgO for the destructive adsorption of hazardous military compounds. Room temperature reactions were done with nanoscale MgO and 2-chloroethyl ethyl sulfide (a mustard gas mimic). Preliminary results indicate that dehydrochlorination of the 2-chloroethyl ethyl sulfide to produce ethyl thio ethene took place. Further studies include observation of reaction rates and carrying out kinetic analyses by using FT-IR, gas chromatography and UV-Vis.

Key words: nanoparticles, MgO, adsorption.

Oral presentation in chemical technologies session.

36 • EFFECT OF REDOX ENVIRONMENT ON OXIDATION OF PENTACHLOROPHENOL WITH MANGANESE OXIDE

R.A. Petrie¹, R.C. Sims¹, J.E. McLean¹, and P.R. Grossl², ¹Division of Environmental Engineering and Utah Water Research Laboratory, Utah State University, Logan, UT, 84322-4110, and ²Department of Plant Soils and Biometerology, Utah State University, Logan, UT, 84322-4820

The fate of pentachlorophenol (PCP) in the subsurface environment of the Libby, Montana, Superfund site is not well understood, especially with regard to reaction with subsurface manganese present at the site. Reduction-oxidation (redox) reactions are predicted to influence the fate, mobility, and interactions of PCP and inorganic soil minerals in subsurface environments. A potentiostat apparatus was designed and constructed to characterize the abiotic interactions of PCP on manganese oxide surfaces at specific ground water redox environments. The optimal redox potential and pH were determined for the oxidation of PCP at 11°C (ground water temperature). Based on experiments conducted at Utah State University (USU), oxidation of PCP is hypothesized to yield polymerized products with humic substances and mineral colloids. These reactions are hypothesized to lead to a reduction in mobility and toxicity, and an enhancement of PCP humification. Oxidation products of PCP and manganese were characterized using Infrared (IR) and Raman spectroscopy to elucidate the chemical composition and nature of polymerization of the reaction products. Results are being used to determine the reactivity of PCP with manganese as a function of the subsurface redox environment and to assist in interpretation of field scale results regarding PCP attenuation under natural or engineered conditions.

Key words: pentachlorophenol, redox, ground water, remediation, humification.

Oral presentation in chemical technologies session

37 • PHOTOCATALYTIC DEHALOGENATION OF CHLORINATED COMPOUNDS WITH 2-PROPANOL AND ACETONE AS SOLVENTS

N. Hollan¹, C. Finstad¹, R.G. Arnold¹, and E.A. Betterton², ¹Department of Chemical and Environmental Engineering, University of Arizona, Tucson, AZ, 85721, and ²Physical and Atmospheric Sciences, University of Arizona, Tucson, AZ, 85721

In the presence of ultraviolet light, carbon tetrachloride (CT) was rapidly degraded to chloroform and other unidentified products in a three-solvent system consisting of isopropanol, acetone, and water. This reaction has not been described previously. The reaction mechanism and kinetics were explored by altering the fractional composition of the three-solvent system or the concentration of the target compound and measuring the rate and products of dehalogenation reactions. Light was provided via an optical fiber and quantified using actinometry in order to determine process quantum efficiency. Half times for CT destruction less than 1.0 h were commonly observed. The principal wavelengths driving the photocatalytic reaction were 220 £ l £ 310 nm, within the absorbance spectrum of acetone. Use of sunlight for photocatalysis in this system is under investigation.

Key words: remediation, photocatalysis, dehalogenation.

Oral presentation in chemical technologies session.

38 • ACCELERATED PHOTODEGRADATION OF AROMATIC COMPOUNDS WITH HYDROGEN PEROXIDE IN AN EMBEDDED TITANIUM OXIDE REACTOR

Q. Yan, S. Kapila, and S. Kesari, Department of Chemistry and Center for Environmental Science and Technology, University of Missouri-Rolla, Rolla, MO, 65409-0010

The presence of synthetic organic contaminants in ground water systems is a matter of concern. A number of processes have been investigated for removal and degradation of these contaminants. Photodegradation offers a potential for a low cost and environmentally-benign remediation technology. In recent years, acceleration of the process has been investigated either through the use of homogeneous sensitizers or with heterogeneous semiconductor photocatalysts such as titanium oxide (TiO₂). The effectiveness of combining sensitizers and photocatalysts, however, had not been investigated and was the subject of the present study. The investigations were carried out with a flow-through reactor. The reactor consisted of two concentric tubes. The inner tube was made of fritted borosilicate glass. A tight-fitting UV transmitting fused silica tube served as the outer tube or envelope. A layer of TiO₂ (anatase crystalline form) was fused onto the borosilicate tube. Irradiation was provided with a xenon arc lamp. Aqueous solutions of selected contaminants (trichloroethylene, naphthalene, phenanthrene, trichlorophenol, and pentachlorophenol) were circulated through the reactors. Degradation efficiencies of contaminants were monitored at varied pH and hydrogen peroxide (H₂O₂) concentrations. Chemical analysis of treated solutions showed that measurable degradation occurred in all irradiation experiments. The highest degradation efficiencies were obtained under basic pH in the presence of H₂O₂.

Key words: photodegradation, embedded TiO₂, pentachlorophenol.

Oral presentation in chemical technologies session.

39 • DESTRUCTIVE ADSORPTION OF ENVIRONMENTAL TOXINS UTILIZING CALCIUM OXIDE AND TRANSITION METAL OXIDE-SUPPORTED CALCIUM OXIDE NANOPARTICLES

S. Decker and K.J. Klabunde, Department of Chemistry, Willard Hall, Kansas State University, Manhattan, KS, 66506-2502

The destruction of chemical models from several classes of environmental toxins has been investigated. The environmental toxins examined in this study were carbon tetrachloride, dimethyl methyl phosphonate, carbon disulfide, and carbonyl sulfide. Calcium oxide and transition metal oxide-supported calcium oxide nanoparticles synthesized via an aerogel method possess a much higher surface area than commercially-available calcium oxide. Due to this high surface area, the particles are capable of adsorbing and reacting with large amounts of toxins. Experimentally, the toxins are vaporized and pulsed over a bed of the particles where they readily adsorb and react with the calcium oxide to produce environmentally-benign products such as calcium chloride and carbon dioxide.

Key words: environmental toxins, destructive adsorption.

Oral presentation in chemical technologies session.

Program Two
Wednesday, May 22, 1996
Chemical Technologies · Cozumel Room

40 • USING FERRATE TO REMOVE HYDRAZINES FROM WASTE WATER

M.D. Johnson, B. Hornstein, and R. Wingo, Department of Chemistry and Biochemistry, New Mexico State University, Las Cruces, NM, 88003

Hydrazine and related compounds have been used for fuels in rocket propulsion systems. Similar compounds have also been used or produced in the textile dye industries. Treatment of wastewater streams from such industries remains a problem. In view of this, we have investigated the ability of ferrate, [FeO₄]^2-, to oxidize hydrazine and structurally similar compounds. Ferrate represents a new alternative treatment procedure for the rapid chemical oxidation of organic wastes which is safer than ozone or chlorine and has no undesirable side products, such as with permanganate. The aerobic ferrate oxidation of hydrazines produces molecular nitrogen and ferric hydroxide: [FeO₄]^2- + N₂H₄ (aq) --> N_2(g) + Fe(OH)_3(s). This reaction and others have been studied in detail and the results will be reported. Other potential uses for ferrate in waste treatment will be discussed. In order to provide a vehicle for the use of ferrate flow streams, we have begun exploration of trapping ferrate into a variety of matrices. The results of these preliminary studies will also be outlined.

Key words: remediation, wastewater, ground water.

Oral presentation in chemical technologies session.

41 • REVIEW OF THE GALVANIC STRIPPING PROCESS FOR USE IN TREATING OXIDIZED METAL WASTES

C.M. Chang, H. Gu, and T.J. O'Keefe, Graduate Center for Materials Research, University of Missouri-Rolla, Rolla, MO, 65409-1170

A new process which is applicable for the treatment of waste residues associated with the metals industry is currently being developed. The unique part of the technology is the use of solid metal reductants in organic solvent systems to spontaneously remove contained impurity ions. The engineering options, termed simultaneous or separate shipping, that can be used in a flow sheet design using the galvanic stripping process are described. In addition, the effects of various operating parameters on the efficiency of the process are described. Examples of the variables which influence the process kinetics include the type of metal or alloy uses, the impurity ion concentration, the chemical concentrations of the active organic and aqueous solutions, and their oxygen contents. Tentative flow sheets of how the process could be used in the treatment of iron-zinc neutral leach residue from an industrial operation are discussed.

Key words: solvent extraction, metallurgy, oxidized waste, iron, zinc.

Oral presentation in chemical technologies session.

42 • DEVELOPMENT OF POLAROGRAPHIC FIELD SENSORS FOR HEAVY METAL DETECTION

K. Bundy, D. Berzins, and P. Taverna, Department of Biomedical Engineering, Tulane University, New Orleans, LA, 70118

Environmental pollution is a problem in all industrialized countries, and heavy metal contamination of water and sediment is often of major concern. Monitoring of contaminant levels usually entails site sampling and, later, analysis in the laboratory. There is a pressing need, however, for accurate and sensitive methods to determine metallic concentrations at polluted field sites directly. Also, to most completely assess the impact of pollution, there is a need for methods to discern the specific chemical forms present at the site. Both needs can potentially be satisfied with field sensors based upon polarographic techniques. Polarography is an electrochemical method in which reduction occurs upon an electrode substrate. The magnitude of the associated current is proportional to the concentration of the substrate being reduced. The potential at which the current is maximized (the half-wave potential) is unique for each metal (and even for each oxidation state of the metal). Such polarographic apparatus can more easily be adapted to field use compared to other analytical techniques such as GFAAS or ICP-AES. The most difficult aspect of designing such an instrument appears to be the electrode substrate. The research project described here is aimed at demonstrating the feasibility of this field sensor concept. The experimental system consists of an EG&G M273 potentiostat (controlled by an IBM PS/2 computer) and EG&G M270 electrochemical analysis software. The measurements are conducted using the three electrode technique. A saturated calomel electrode serves as the reference; graphite rods are used for the working and counter electrodes. The three electrodes are placed in a cell containing a fluid appropriate for the analysis known as the supporting electrolyte. Our first experiments focused on determining which polarographic or voltammetric technique (cyclic, linear sweep, normal pulse, differential pulse, square wave, or sampled DC) produced the most reliable results using graphite electrodes to detect known Pb⁺² concentrations added to water. Cyclic voltammetry was observed to be the most promising. The simulated field test apparatus described above was then used to conduct cyclic voltammetric measurements of samples obtained from Bayou Trepagnier near Norco, Louisiana. The first set of experiments extracted lead (Pb⁺²) from spoil bank samples using methods that would be practical to implement in the field (room temperature acid digestion for 5 minutes in 0.15 M HCI) to leach out metal ions and filtering the liquid sample to free it of suspended particles. These specimens were also tested for metallic content using differential pulse polarographic methods used routinely in our laboratory for heavy metal analysis. Generally, good agreement was found between the laboratory and simulated field methods, and the results of each were well correlated with those of other studies that have previously monitored heavy metal concentration in the Bayou Trepagnier area. In a second series of experiments, assays were done for Pb⁺² content of water samples obtained from the Bayou Trepagnier site. Here the agreement between the field cyclic voltammetry and laboratory differential pulse polarography testing was more problematical due to greater difficulty in detecting the much lower lead levels in the water (compared to the spoil bank). This result indicated the need for improved field sensor electrode sensitivity. Further experiments were then conducted to see if the situation could be improved using graphite electrodes with increased surface area. The ratio of peak to total (i.e. peak plus hysteresis) current in cyclic voltammograms of Pb⁺² in water taken with graphite electrodes of various lengths scaled linearly with increasing surface areas over more than an order of magnitude. This observation provides optimism that this remote sensor concept can be adjusted to provide accurate measurements in situ for lead and other heavy metals, since graphite is available in a variety of porous and fibrous forms with high specific surface area. Besides sensing element optimization, a number of additional steps must be taken to develop a sensor that is practical for field use. A portable, battery-powered potentiostat compatible with a laptop computer (for measurement control, data acquisition, and data storage) must be available. A kit must be on hand containing reagents that can practically extract various heavy metals of interest from polluted samples at room temperature in reasonable time periods, syringe filters for separation of aqueous from particulate matter, and supporting electrolytes that can safely be handled while still providing adequate detection threshold sensitivity. Research aimed at developing these components is ongoing. In conclusion, heavy metal pollution assessment can be improved with the development of sensors which can be deployed in the field directly. This will allow easier identification of pollution "hot spots" and will minimize sample storage life concerns in speciation studies. Polarographic methods appear to be a promising basis for such sensors.

Key words: polarography, metal, field sensors, pollution monitoring.

Oral presentation in chemical technologies session.

Technology Transfer and Analytical Methods · Cozumel Room

43 • IMPROVED HYDROCARBON DETECTION

J.L. Bratton¹and W.L. Bratton², Applied Research Associates, Inc., ¹4300 San Mateo Blvd. N.E, Suite A220, Albuquerque, NM, 87110, and ²105A Waterman Road, South Royalton, VT, 05068

The rapid in situ delineation of hydrocarbon contamination has the potential for significantly reducing the total cost of remediating many thousands of contaminated sites. These cost reductions are possible because of the speed of the site characterization, the reduction in the number of laboratory samples required, the reduction in drilling waste which must be disposed of, a better definition of the contaminated zone, and the ability to monitor at a number of locations during remediation. This is possible with a new minimally invasive hydrocarbon detection device, the Fuel Fluorescence Detector (FFD). The FFD operates on fluorescence principles and is deployed in the tip of a Cone Penetrometer to make continuous measurements of the contamination as the probe is pushed into the ground. This paper will describe the FFD and show laboratory and field data gathered at contaminated sites.

Key words: site characterization, hydrocarbon detection, fluorescence, in situ measurements, cone penetrometer.

Oral presentation in technology transfer and analytical methods.

44 • IDENTIFICATION OF PENTACHLOROPHENOL IN ALLUVIAL SOILS UTILIZING IMMUNOASSAY FIELD METHODS, GRAND TETON NATIONAL PARK, WYOMING-A CASE STUDY

A.B. Flynn and M. Bell, The Roybal Corporation, 7600 E. Eastman, Suite 200, Denver, CO, 80231

Immunoassay (IA) field methods were utilized to identify the presence of pentachlorophenol (PCP) in alluvial soils. IA-supported field decisions were used to determine the limits of excavation during remediation of a former pole-dipping station, significantly decreasing the volume of hazardous waste generated for disposal. Semi-qualitative test results were obtained using IA methods in less than one hour. Immunoassay field tests were compared to analytical laboratory test results. One in 12 field samples indicated a false-positive test result. On-site testing decreased the potential for false negative confirmatory lab samples and reduced the amount of equipment time required for excavation and backfill of the contaminated area.

Key words: immunoassay, remediation, assessment, regulatory compliance.

Oral presentation in technology transfer and analytical methods session.

45 • POLLUTION PREVENTION AND MICROSCALE CHEMISTRY IN THE RESEARCH LABORATORY

M.D. Erickson, J.S. Alvarado, C.-S. Lu, F. Lemley, D.P. Peterson, J.F. Schneider, L.M. Shem, and J. Silzer, Argonne National Laboratory, 9700 S. Cass Avenue, Argonne, IL, 60439-4837

Pollution prevention (P²) has not been sufficiently addressed in the research laboratory. Although the amount of reagent used per experiment is often only a few milliliters, these small amounts can quickly add up, especially when they are aggregated across the entire research community. Effective P² will require operational or even fundamental changes in the techniques and methods employed. "End-of-pipe" recycling is not practical with small streams. Microscale chemistry is loosely defined as the application of chemical principles and apparatus at a scale much smaller than that currently employed by most bench chemists, reducing the volume of reagents and product by several orders of magnitude. "Green" chemistry is an umbrella term addressing waste minimization, P², solvent substitution, environmentally conscious manufacturing, maximum atom utilization, technologies for a sustainable future, environmental security, and industrial ecology. The primary focus of "green" chemistry over the past decade has been within the chemical industry; adoption at the laboratory scale has been slow. Green and microscale methods are increasingly necessary for the laboratory and research communities as regulations tighten, the cost of waste disposal escalates, and public scrutiny increases. The high potential for P² in the laboratory will be specifically illustrated with improvements in routine analytical techniques. Routine methods for environmental and waste samples analyses are quite prescriptive and often do not include the principles of waste minimization and P². Many methods require preparation of 100-fold or more excess sample for an instrumental determination. Many methods also use reagents which are not now considered "green." We have adapted the principles of microscale chemistry, along with other modern analytical approaches, to develop routine analytical methods that significantly reduce waste generation while they maintain acceptable analytical figures of merit and achieve cost savings through reduced reagent consumption and reduced labor costs.

he principles of P² and waste minimization were used to develop and test microscale adaptations to regulatory-approved analytical procedures for the analysis of Resource Conservation and Recovery Act (RCRA) elements in soil.
In a separate effort, we developed new procedures for preventing or minimizing primary and secondary waste generation in chemical laboratory operations for the analysis of polychlorinated biphenyls (PCBs).
In a third example, an integrated thermal desorption/gas chromatography/mass spectrometer (TD/GC/MS) system was investigated as an alternative to the customary solvent extraction, cleanup, and solvent elimination followed by GC/MS. Because solvents are eliminated from the analytical method, only the analyses of interest are extracted, other reagents are eliminated, and the process can be integrated into a single flow-through system.

Results will be reported, and the general significance of P² in the analytical laboratory will be discussed. The analytical applications are illustrative of potential changes achieved by incorporating P² principles into research and teaching laboratories. The overall importance of P² in the research and teaching laboratory will be discussed. P² in the science laboratory must be a part of our commitment to teach the next generation how to go about the business of science. This work supported by the U.S. Department of Energy, Assistant Secretary for Environmental Management, Office of Technology Development, under contract W-31-109-Eng-38. The submitted manuscript has been authored by a contractor of the U.S. Government under contract No. W-31-109-ENG-38. Accordingly, the U.S. Government retains a nonexclusive, royalty-free license to publish or reproduce the published form of this contribution, or allow others to do so, for U.S. Government purposes.

Key words: pollution prevention, green chemistry, microscale chemistry.

Oral presentation in technology transfer and analytical methods session.

Technology Transfer and Munitions-Contaminated Soils · Cozumel Room

46 • SOLIDIFICATION/STABILIZ-ATION OF METALS AND EXPLOSIVES IN SOIL

H. Craig¹, J. Wakeman², and M. Channell³, ¹U.S. Environmental Protection Agency Region 10, Oregon Operations Office, Portland, OR, 97204, ²Seattle District Corps of Engineers, 4735 E. Marginal Way, Seattle, WA, 98124-2255, and ³U.S. Army Corps of Engineers, Waterways Experiment Station, 3909 Halls Ferry Road, Vicksburg, MS, 39180-6199

Metals are often co-contaminants with explosives at munitions sites and may inhibit biological activity in soils. Metals toxicity and leachability could preclude the use of bioremediation technologies such as composting and slurry phase bioreactors. The current remediation approach for mixed metals and explosives in soil is incineration followed by solidification/stabilization (S/S). While this treatment train is effective, it is costly and requires the use of air pollution control equipment to capture metals air emissions during incineration. Direct S/S without incineration is a potentially cost effective treatment option. A S/S treatability study was conducted for soils from the Ammunition Demolition Activity (ADA) open burn/open detonation (OD/OD) area at the Umatilla Army Depot Activity, Hermiston, Oregon, Superfund site. The primary contaminants are metals such as lead (Pb); cadmium (Cd); nitroaromatics 2,4,6-trinitrotoluene (TNT) and 1,3,5-trinitrobenzene (TNB); and nitramines hexahydro-1,3,5-trinitro-1,3,5-triazine (RDX) and octahydro-1,3,5,7-tetranitro-1,3,5,7-tetrazacine (HMX). Various ratios of portland cement and fly ash were evaluated as inorganic binders, and granular activated carbon (GAC) as an organic binder. Leachability tests on the solidified matrix were conducted using the EPA Toxicity Characteristic Leach Procedure (TCLP) (EPA SW-846 Method 1311) and explosives laboratory analysis using high performance liquid chromatography (HPLC) (EPA SW-846 Method 8330). Results indicate an optimum S/S ratio of 30% concrete, 10% fly ash, and 5% GAC for Umatilla soils. Average TCLP leachate reductions were 99.6%, 96.9%, 99.96%, 96.4%, 97.1%, and 99.8% for Pb, Cd, TNT, TNB, RDX, and HMX, respectively. Leachate concentrations were below TCLP criteria for metals and below risk-based criteria for explosives. Based on treatability results, S/S was selected as the treatment technology for 20,000 cubic yards of ADA soils. The remedial action contractor will further evaluate treatment mixtures of cement, fly ash, and soluble silicates as inorganic binders, and GAC, organoclays, and rice hull ash as organic binders.

Key words: metal, explosives, trinitrotoluene, RDX, treatment technologies.

Oral presentation in technology transfer and munitions-contaminated soils session.

47 • FIELD DEMONSTRATION OF ON-SITE ANALYTICAL METHODS FOR TNT AND RDX IN GROUND WATER

H. Craig¹, G. Ferguson², A. Markos², A. Kusterbeck³, L. Shriver-Lake³, T. Jenkins⁴, and P. Thorne⁴, ¹U.S. Environmental Protection Agency Region 10, Oregon Operations Office, Portland, OR, 97204, ²Black & Veatch Special Projects Corporation, 1201 Pacific Avenue, Suite 1100, Tacoma, WA, 98402-4301, ³Naval Research Laboratory, Center for Bio/Molecular Science and Engineering, Code 6910, Washington, DC, 20375-5348, and ⁴U.S. Army Corps of Engineers, Cold Regions Research and Engineering Laboratory, Hanover, NH, 03755-1290

A field demonstration was conducted to assess the performance of eight commercially available and emerging colorimetric, immunoassay, and biosensor on-site analytical methods for explosives 2,4,6-trinitrotoluene (TNT) and hexahydro-1,3,5-trinitro-1,3,5-triazine (RDX) in ground water at the Umatilla Army Depot Activity, Hermiston, Oregon, and Naval Submarine Base, Bangor, Washington, Superfund sites. Ground water samples were analyzed by each of the on-site methods anal results compared to laboratory analysis using high performance liquid chromatography (HPLC) (EPA SW-846 Method 8330). The commercial methods evaluated include the D-TECH/EM Science TNT and RDX immunoassay test (EPA SW-846 Methods 4050 and 4051), the EnSys, Inc., TNT and RDX colorimetric test (EPA SW-846 Methods 8515 and 8510) with a solid phase extraction step, and the Ohmicron TNT immunoassay test. The emerging methods tested include the antibody-based Naval Research Laboratory (NRL) Continuous Flow Immunosensor (CFI) for TNT and RDX, and Fiber Optic Biosensor (FOB) for TNT. Precision and accuracy of the on-site methods were evaluated using Relative Percent Difference (RPD) and linear regression analysis. Over the range of conditions tested, colorimetric methods for TNT and RDX showed the highest accuracy of the commercially available methods, and the CFI showed the highest accuracy of the emerging methods for TNT and RDX. The colorimetric method was selected for routine ground water monitoring at the Umatilla Army Depot Activity site, and further field testing on the NRL CFI and FOB biosensors will continue at both Superfund sites. The primary use for these analytical methods would be for influent and effluent monitoring for granular activated carbon (GAC) ground water and leachate treatment systems, which are projected to operate for a period of 10 to 30 years.

Key words: explosives, trinitrotoluene, RDX, analytical methods, ground water.

Oral presentation in technology transfer and munitions-contaminated soils session.

48 • FIRST PRODUCTION-LEVEL BIOREMEDIATION OF EXPLOSIVES-CONTAMINATED SOIL IN THE U.S.

D.D. Emery and P.C. Faessler, Bioremediation Service, Inc., 12130 N.E. Ainsworth Circle, Suite 220, Portland, OR, 97220-9009

The first production-level bioremediation of explosives-contaminated soil in the U.S. is taking place at the Umatilla Army Depot Activity (UMDA) near Hermiston, Oregon. Soil from munitions washout lagoons contained high concentrations of TNT (2,4,6-trinitrotoluene) and RDX (hexahydro-1,3,5-trinitro-1,3,5-triazine), as well as HMX (octahydro-1,3,5,7-tetranitro-1,3,5,7-tetrazocine). In addition to these primary contaminants, laboratory tests were performed on Tetryl (N-2,4,6-tetranitro-N-methylaniline), 4ADNT (4-amino-2,6-dinitrotoluene), 2 ADNT (2-amino-4,6-dinitrotoluene), 2,4 DNT (2,4-dinitrotoluene), 2,6 DNT (2,6-dinitrotoluene), TNB (1,3,5-trinitrobenzene), DNB (1,3-dinitrobenzene) and NB (nitrobenzene) during the pilot-scale treatability tests. The established clean-up goal is 30 mg/kg each for TNT and RDX. Both field screening and EPA Method 8330 analyses are being performed. Treatment time on a 2,700 cubic yard batch (810 cubic yards of soil) is 10-12 days. A composting technique developed by the Army Environmental Center is being used at the site. Five compost amendments are being blended with the contaminated soil. Specialized soil fuming equipment mixes the compost for optimum biological action and homogeneity. Moisture and pH levels are closely monitored to ensure that thermophilic bacteria play a dominant role in the degradation process. Homogeneity of the compost mix ensures that all contaminants are rapidly degraded. Nearly 5,000 cubic yards of soil have been successfully treated, with more than 70% of all analyses indicating non-detectable levels of both TNT and RDX. The U.S. Army Corps of Engineers estimates that over $2.6 million is being saved using bioremediation at Umatilla.

Key words: bioremediation, explosives, munitions, trinitrotoluene, RDX.

Oral presentation in technology transfer and munitions-contaminated soils session.

Technology Transfer and Field Applications · Cozumel Room

49 • FIELD UP-SCALING OF PROCESSES ASSOCIATED WITH BEHAVIOR OF NONAQUEOUS PHASE WASTE CHEMICALS IN HETEROGENEOUS AQUIFERS

T.H. Illangasekare, Department of Civil, Environmental, and Architectural Engineering, University of Colorado at Boulder, Boulder, CO, 80309-0428

Remediation of aquifers contaminated with organic chemicals is a topic of public concern as well as of considerable scientific, engineering, and regulatory interest. In recent years, significant work has been done in basic research on remediation of waste sites that have been contaminated with both light and dense organic chemicals that are in nonaqueous phase. These technologies have been primarily developed and tested in small-scale experiments in the laboratory under idealized conditions. Field implementations have had limited success due to a number of factors which we have identified in our own ongoing research as well as by other investigators. These factors include complexities created by the natural soil heterogeneities in the field, chemicals which are in complex mixtures, complex physical, chemical, and biological interactions which change the pore characteristics, dissolution processes that are not very well understood, nonavailability of effective and cost-effective field characterization techniques, and limitations in the modeling tools that are used in the design and evaluation of the field remediation techniques, among others. This paper presents an overview of experimental and modeling research that is conducted at the University of Colorado that addresses the issue of up-scaling the laboratory-developed technologies of aquifer remediation to the field. The development of these up-scaling methodologies require the understanding of the effects of dimensionality of flow and transport and the role and effect of heterogeneities at various scales from soil pores to spill-site. The parameters that control the basic processes of flow, transport, entrapment, dissolution, and mobilization at various scales of interests have to be identified. Methods to determine these parameters at the field scale have to be developed. Research results that address the above issues as related to flow, entrapment, dissolution, surfactant enhanced dissolution, and thermal mobilization are presented. Possible use of tracer technologies for field parameter estimation are presented. A systematic procedure for application of the methods that have been developed in the laboratory to the field is discussed.

Key words: organic waste, up-scaling, parameter estimation, field characterization.

Oral presentation in technology transfer and field applications session.

50 • MINE RECLAMATION AND RESIDUAL WASTES

M.R. Deeker and J.E. Buckley, SCS Engineers, 10401 Holmes Road, Suite 400, Kansas City, MO

Power generation stations, metal and nonmetal processing facilities, and the cement industry will generate tens of thousands of tons of residual waste in 1996. Beneficial and sound environmental solutions to the final disposition of these residual wastes are becoming paramount to the industry and federal, state, and local regulatory agencies. One potential source for beneficial use of residual waste is the mining industry. The mining industry has a window of opportunity to convince state legislatures to allow the use of residual wastes for mine reclamation material, additives for control of acid mine drainage, underground mine stabilization, and numerous other activities that will benefit both the mining industry and the industry generating the waste. The main concerns that the mining industry will have to consider include regulatory requirements, knowledge of the chemical compatibility of the site and waste, detailed hydrogeologic characterization of the site under consideration, and efficient engineering methods for transportation, handling, placement, and environmental controls. The first issue to address is a comprehensive review of federal, state, and local regulations to determine what requirements must be met to use the residual waste as a reclamation material. Some states are aggressively working with industry for beneficial uses of residual wastes while other states consider all residual waste as either solid or hazardous waste with corresponding regulatory disposal requirements. Beneficial use of residual waste is not considered a remedy by federal regulators to all the issues associated with the waste. Next, a waste characterization of the material must be performed to identify and evaluate disposal methods for each specific waste material. Various field and laboratory testing methods can be used to evaluate the residual waste. Third, a hydrogeologic model of the mine area must be developed. The hydrogeologic model presents a site-specific characterization of geologic and hydrogeologic conditions. The model is then used to evaluate the effects the disposal activities will have on soils and ground water at the site. Finally, defining the transportation, handling, and placement of the residual wastes will require a combined effort from the industry generating the waste and the mining industry. The environmental controls will be dependent on the results of the waste characterization and hydrogeologic characterization performed.

Key words: residual, mine reclamation, beneficial use.

Oral presentation in technology transfer and field applications session.

51 • GRAY DAUN URANIUM MINE REMOVAL ACTION, SAN JUAN COUNTY, UTAH

D.L. Harber¹ and J.D. Egnew², ¹Manti-La Sal National Forest, 599 West Price River Drive, Price, UT, 84501, and ²Payette National Forest, P.O. Box 1026, McCall, ID, 83638

The Forest Service conducted a CERCLA removal action, with funding through the Federal Facilities Compliance Program, during the winter of 1993-1994 at the Gray Daun uranium/vanadium mine in San Juan County, Utah. Sidehill waste dumps had partially obstructed, and were being eroded by, a perennial stream. Radon was being emitted from the mine workings. Surface water transport of radionuclides from the dumps and immediate downgradient use of this water for culinary and agricultural purposes, along with high radon levels, prompted the removal action. Originally the plan was to move 600 cubic yards of waste rock back into the mine, seal 19 adits, and recontour and reclaim the surface of a 4-acre site. Placing the waste rock back in the mine was chosen as the method with the lowest cost that would mitigate the hazard and require no future maintenance. After the project began, approximately 6,000 cubic yards of additional waste rock was found to be covered by colluvium. Six additional adits were also found. The contract was modified to account for these changes. All of the waste rock was eventually placed inside the mine. Ventilation seals were placed in four of the adits where radon gas emissions were a problem. All but one of the adits were permanently closed using native rock and explosives. The remaining adit closure was designed to allow controlled access to one of two known locations of crocodile tracks in the Morrison formation.

Key words: uranium, radon, water quality, removal action.

Oral presentation on technology transfer and field applications session.

52 • ROLE OF CARBONATION IN LONG TERM PERFORMANCE OF CEMENTITIOUS WASTEFORMS

N. Gutierrez, S. Bin-Shafique, J.C. Walton, A. Tarquin, P. Sheeley, R. Smith, M. Rodriguez, and R. Andrade, Department of Civil Engineering, University of Texas at El Paso, El Paso, TX, 79968

One of the most widely used site remediation and waste disposal options is cement-based wasteforms. Despite this fact, a definition and quantification of processes controlling long-term performance are lacking. In the U.S., wastes are required by law to be placed in the unsaturated zone, but wasteform performance is evaluated using laboratory tests (TCLP, ANSI/ANS-16.1) which specify fully water-saturated conditions. These tests ignore the potentially important role of cement reaction with soil gases in influencing wasteform performance. The presented research represents a combined experimental and modeling program approach to evaluate the role of the carbon dioxide reactive component of soil gas on the long-term performance of cementitious wasteforms. A series of wasteforms were exposed to an accelerated environment for carbonation and then subjected to leaching tests in water and acetic acid. Results were analyzed by comparison of experimental data with the theoretical models of the leaching process. In addition, diffusion coefficients were determined by fitting of the data to the theoretical model considering a finite domain of the wasteform, and solubility diagrams for the different species were constructed from this data. The results indicate that carbonation increases the apparent diffusion coefficient for unreactive species while resulting in stronger chemical binding of metals through solid solution in calcite.

Key words: cementitious wasteforms, diffusion coefficient, carbonation.

Oral presentation in technology transfer and field applications session.

Program Two Thursday, May 23, 1996 Technology Transfer and Field Applications · Cozumel Room

53 • MANAGING THE PUMP-AND-TREAT END GAME

V.I. Terauds, Enhanced Solutions!, 616 Central S.E., Suite 219, Albuquerque, NM, 87102

Understanding the fate and transport of contaminants in the subsurface has received much attention as contaminant migration affects risk assessment and remedial design. However, understanding the subsurface changes and transformations that occur as a result of implementing ground water remedial actions has received much less attention, other than to say that ground water pump-and-treat does not perform as predicted and is typically not a remedial technology of choice to achieve aquifer cleanup. Recent research has focused on optimizing pump-and-treat, rather than looking at the micro-scale processes that limit significant contaminant mass removal regardless of optimal ground water flowpath design. In analogy to the extractive industries, the environmental remediation paradigm needs to shift such that the appropriate tools are used for the appropriate setting, driven by an appreciation of both macro- and micro-scale limitations on contaminant removal. In contrast to the extractive industries, the performance goals often exceed 99.9999 percent removal efficiencies without monetary incentive for extraction, but rather the goal of health and environmental risk management. This presentation focuses on outlining and understanding the different micro-scale physical, chemical, and biological processes affected by ground water pumping and their impact on creating reasonable performance objectives and life-cycle designs capable of achieving remedial success. Ground water pumping affects not only contaminant concentrations, but aquifer redox conditions, the availability of electron acceptors, precipitation/dissolution reactions, diffusion, and other subsurface processes. The well-known ground water pumping performance curves that reach asymptotic levels merely reflect that there is a remedial breakover point at which the concentration gradient stabilizes due to the increasing role of microprocesses. Accelerating the remedial breakover point and achieving the minimum concentration at which breakover occurs should be the goal of any ground water pump-and-treat system as this emphasizes maximum contaminant mass removal over time. The management of the asymptotic levels often means that ground water pump-and-treat systems continue to operate simply to satisfy political and permitting concerns. Instead, a proposed life-cycle design that uses subsurface process dynamics and incorporates naturally-occurring fate and transport processes is suggested. Tools and techniques will be discussed to manage risk and remedial performance in a way to optimize remedial resource allocation in terms of both time and cost.

Key words: environmental fate and transport, ground water remediation.

Oral presentation in technology transfer and field applications session.

54 • DESIGN CONSIDERATIONS OF VERTICAL VERSUS HORIZONTAL WELL CONFIGURATIONS FOR AIR SPARGING/SOIL VAPOR EXTRACTION REMEDIATION SYSTEMS

V.A. Mast¹ and K.E. Koerner², ¹School of Civil Engineering, Oklahoma State University, Stillwater, OK, 74075, and ²Koch Industries, Inc., Wichita, KS, 67201-2338

A number of factors are considered in designing an in situ air sparging (IAS) with associated soil vapor extraction (SVE) system for the remediation of soil and ground water contaminated with petroleum hydrocarbons. A system is designed, based upon established criteria, which will effectively meet state and federal remediation standards. One of the major decisions in an IAS/SVE system design is well configuration, specifically, the orientation of wells, vertical or horizontal. Tradition has dictated the use of vertical wells. However, horizontal wells are now being considered for both methods. Specifically, three questions are posed: 1. Should vertical or horizontal wells be used for air sparging? 2. Should vertical or horizontal wells be used for soil vapor extraction? 3. If a horizontal orientation is recommended, should a trench design or a directional drilled well be used? To answer these questions, one must consider the hierarchy of criteria to be used and driving factors analyzed.

Key words: innovative, air sparging, soil vapor extraction, directional drilling.

Oral presentation in technology transfer and field applications session.

55 • POLLUTION PREVENTION ASSESSMENTS FOR MARINE MAINTENANCE AND CONTAINER PRINTING INDUSTRIES

M. Erten-Unal¹, J.M. Marchello¹, H. Robinson¹, M. Burgess², and G. Aydlett², ¹Old Dominion University, Department of Civil & Environmental Engineering, KDH Room 133-A, Norfolk, VA, 23529-0241, and ²Industrial Waste Division, Hampton Roads Sanitation District, P.O. Box 5911, Virginia Beach, VA, 23455-0911

A unique working partnership (the Partnership) was formed between the Old Dominion University Department of Civil and Environmental Engineering (ODU) and Hampton Roads Sanitation District Industrial Waste Division (HRSD) to assess and recommend pollution prevention measures at no cost to small- and medium-sized industries in the Hampton Roads area of the Commonwealth of Virginia. The project provided two types of industries with direct on-site technical consultation on waste reduction, including elimination of solid and hazardous waste, wastewater discharges, and air emissions. The two industry types were marine maintenance and container printing industries. ODU provided on-site pollution prevention opportunity assessments for qualifying facilities in the selected industries. The purpose of the visits was to help the industry identify some easy-to-implement pollution prevention and recycling options and more comprehensive approaches to waste reduction. The findings and recommendations were outlined in a report including cost/benefit analyses on replacing processes and recovering waste streams. HRSD reviewed audits and reports and worked with facilities to carry out audit recommendations in a timely manner. Follow-up procedures included seeking opinions from participating facilities, generation of printed information targeting industry type, and workshops focusing on information sharing by industry type. The project supplemented and complemented existing pollution prevention programs by working with the Virginia Department of Environmental Quality and Office of Pollution Prevention to serve as an expansion of service to the local level and provided a readily available information exchange. Besides providing on-site pollution prevention assessments to local industries, the information gathered was further developed by the soliciting of input from additional area facilities during information exchange workshops. Industry-specific publications were produced as a result of these comprehensive efforts which greatly increased the impact of the individual assessments.

Key words: pollution prevention, marine maintenance, printers.

Oral presentation in technology transfer and field applications session.

Technology Transfer and Training · Cozumel Room

56 • SUPERFUND SCIENTISTS TEACH MINORITY HIGH SCHOOL STUDENTS SCIENTIFIC LITERACY AND CAREER DEVELOPMENT IN NOVEL YEAR-ROUND PROGRAM TIED TO SUPERFUND INVESTIGATIONS

L.R. Sherman, L. Claudio, and P.J. Landrigan, Mt. Sinai School of Medicine, Environmental Health Sciences Center, New York, NY, 10029

There is a need to improve scientific literacy among under-represented minority high school students in order to increase their access to, and participation in, environmental health careers. Recognizing that high school students are not adequately grounded in the environmental and biological sciences, and are ill-prepared in the methods, procedures, and concepts of carrying out environmental research, the program has designed the first year-round environmental health course for high school students-meshing high school faculty and administration with Superfund scientists. Students were taught jointly by faculty in the Mount Sinai Environmental Health Sciences Center and their own high school teachers. The curriculum established fundamental concepts in health and the effects of the man-made world on health and behavior-through lectures, seminars, library, and laboratory research. The year-round program culminated in a six-week, full-time summer internship with a Superfund Investigator on subjects such as: "Detection of PAB and 1-Hydroxypyrene in Urine of Military Personnel"; "Lead Toxicity: Relating Human Health Effects to Dose"; "The Transport of Polychlorinated Biphenyl Sediments in the Hudson River"; "Hormonal Activity of Chlorinated Hydrocarbons and Related Contaminants from New York Sediments." Through extramural support, students and faculty sailed on the sloop "Clearwater" and learned about the history and the ecology of the Hudson River.

Key words: minority, environmental health, scientific literacy, polychlorinated biphenyls, hydroxypyrene, lead.

Oral presentation in technology transfer and training session.

57 • RAD WORLD/TV EARTH ENVIRONMENTAL VIDEOS

B. Powell, Waste-management Education and Research Consortium, New Mexico State University, Las Cruces, NM, 88003

The strategy of the Department of Energy's Waste-management Education and Research Consortium (WERC) program in developing human resources in the EM/Waste-management field is complemented by parallel efforts to create and sustain interest in environmental science at the pre-college level. The TV EARTH program is an environmental science program aimed at creating and disseminating environmental science materials for grades 6-12 using computer animation and multimedia. The objective is to capture the interest of this age group with imaginative presentations, scripted and animated by middle, high school, and university students. Employing upper middle school/high school language and educational strategies, topics such as radioactive waste storage and underground imaging radar are demystified. All lessons are useful for environmental courses and are linked to DOE-sponsored environmental research. The presentation will highlight the third video, Rad World, featuring the Waste Isolation Pilot Plant (WIPP). The video, which is accompanied by a curriculum guide complete with activities and evaluation material, examines radiation by studying the operation of a Geiger counter, the meaning of the half-life of a radioactive isotope, and much more. The cast includes Alpha, Beta, and Gamma, three "rad" characters. A central topic is low-level radioactive waste-storage, involving information on the WIPP site. One exceptional feature is a high school student's 3-D computer animated travel through the tunnels of the WIPP site.

Key words: radioactive waste, environmental science, multimedia education, nuclear waste storage, hazardous waste storage.

Oral presentation in technology transfer and training session.

58 • NATIVE AMERICAN ENVIRONMENTAL ISSUES: PUEBLO SUPERFUND PROGRAM

C.M. Sanchez and T.L. Garcia, All Indian Pueblo Council/Pueblo Office of Environmental Protection, 3939 San Pedro N.E., Suite B, Albuquerque, NM, 87110

In 1991, the All Indian Pueblo Council (AIPC) entered into a Superfund Memorandum of Agreement with the U.S. Environmental Protection Agency (EPA) Region VI to create the Pueblo Office of Environmental Protection (POEP). Currently, the Superfund Program is the largest program at POEP and performs all technical work in-house. POEP Superfund Progress: The POEP Superfund Program is currently in the site assessment phase of the Superfund process. In Fiscal Year 1992, the POEP Superfund Program used aerial photos of the 19 Pueblos to determine the number of potential hazardous waste sites. There were an estimated 500 potential sites identified within the 19 Pueblos. Communication with each of the Pueblos has also identified potential hazardous waste sites for possible CERCLA investigation. In Fiscal Year 1993, 12 Preliminary Assessment (PA) reports were completed and one removal action was initiated at a heavy metal contaminated site. The removal action was conducted at the Wall Colmonoy Facility at Isleta Pueblo. In Fiscal Year 1994, 21 PA reports were completed and 2 Site Inspection (SI) reports were completed. During Fiscal Year 1995, the POEP Superfund Program completed 15 PA reports and 5 SI Reports. This Fiscal Year (1996), the Superfund Program will complete 10 PA reports and 8 SI Reports. The Program is also researching alternative solutions for addressing some of the potential hazardous waste sites. Tribal Issues: Because the 19 Pueblos are each sovereign nations and unique, there are several differences and gaps associated with the current CERCLA policies and EPA methodologies. The Superfund Hazard Ranking System (HRS) model does not currently take into account Indian religious and ceremonial aspects. For example, culturally significant plants, animals, and sacred areas are not considered in this model when investigating sites. The current process is also very lengthy and does not fit the Indian Pueblo culture very well. The POEP Superfund Program is working with EPA Region VI to make some considerations of site-specific situations when they arise. We are also looking at improving the Superfund Process to fit the Indian Pueblos in the long term. The AIPC and POEP are committed to promoting all environmental programs through EPA, State, or private partnership arrangements. The involvement of all entities in the State of New Mexico is vitally important to addressing and considering Pueblo environmental issues.

Key words: Native American environmental issues, Superfund.

Oral presentation in technology transfer and training session.

Program Three Tuesday, May 21, 1996 Organic Contaminants · Coronado Room

59 • OPTIMIZATION OF CONTAMINANT REMOVAL FOR HETEROGENEOUS SYSTEMS BY SOIL VENTING

D. Casey¹, J.C. Walton¹, C. Bailey¹, and D. LeMone², ¹Department of Civil Engineering and ²Department of Geological Sciences, University of Texas at El Paso, El Paso, TX, 79968

Parameters affecting the removal of a single volatile contaminant, such as TCE, from the vadose zone were modeled using a finite difference code. The code solves both the multiphase energy equation and the mass balance equations for air, water, and a contaminant. Components of the energy balance include: sensible heat, latent heat of vaporization of water and the contaminant, and vacuum evaporation. The relationship between the energy flux and mass fluxes of soil water and of the contaminant indicate how venting can be optimized to enhance removal efficiency. Soil temperature changes are more dependent on the latent heat effects of water and a contaminant than the sensible heat effects. Vacuum cooling at the well bore causes a localized increase in the concentration of the contaminant.

Key words: soil venting, remediation, soil vapor extraction.

Oral presentation in organic contaminants session.

60 • REMOVAL OF HYDROCARBONS FROM CONTAMINATED WATER USING AIR-SPARGED HYDROCYCLONE TECHNOLOGY

J.D. Miller and D. Lelinski, Department of Metallurgical Engineering, University of Utah, Salt Lake City, UT, 84112

The air-sparged hydrocyclone (ASH) technology offers the unique opportunity to achieve efficient removal of hydrocarbons from contaminated water at a high specific capacity. Such an opportunity exists because the ASH system generates a very large number of fine gas bubbles, and establishes intimate fluid dynamic contact of these bubbles with the contaminated water. As a consequence of the multiphase flow conditions in the ASH system, effective stripping of hydrocarbons from various contaminated water streams can be accomplished with a very short residence time (less than 1 second in the 2-inch diameter ASH unit). In other words, a specific processing capacity, of more than 100 times that of conventional air stripping technology, is possible with the advanced ASH technology. The effectiveness of the ASH system has been demonstrated through a number of experiments. Results from these tests shows that the ASH technology has been effective for the removal of aromatic hydrocarbons such as benzene, aliphatic hydrocarbons such as octane, and chlorinated hydrocarbons such as 1,2-dichloroethane, with the recovery between 97 and 99%. It should be noted that these volatile organic contaminants cover a wide range of systems in terms of the ease of contaminant removal from the water, with 1,2-dichloroethane being the most difficult to remove, while octane is the easiest to remove.

Key words: hydrocarbons, stripping, air-sparged hydrocyclone.

Oral presentation in organic contaminants session.

61 • MATHEMATICAL MODELS FOR BIODEGRADATION OF CHLORINATED SOLVENTS

X. Zhang, S.K. Banerji, and R.K. Bajpai, Department of Chemical Engineering, University of Missouri-Columbia, W2030 EBE, Columbia, MO, 65211

Complete mineralization of chlorinated solvents by microbial action has been demonstrated under aerobic as well as anaerobic conditions. In all the cases, it is believed that tile biodegradation is initiated by broad-specificity enzymes involved in metabolism of a primary substrate. Under aerobic conditions, some of tile primary carbon and energy substrates are methane, propane toluene, methanol, phenol, and ammonia; under anaerobic conditions, glucose, sucrose, acetate, propionate, isopropanol, methanol, and even natural organics act as carbon source. Published biochemical studies suggest that the limiting step is often the initial part of the biodegradation pathway within the microbial system. For aerobic systems, the limiting step is thought to be the reaction catalyzed by mono- and dioxygenases which are induced by most primary substrates, although some constitutive strains have been reported. Other critical features of the biodegradative pathway include: 1) activity losses of critical enzyme(s) through the action of metabolic byproducts, 2) energetic needs of contaminant biodegradation which must be met by catabolism of the primary substrates, 3 ) changes in metabolic patterns in mixed cultures found in nature depending on the availability of electron acceptors, and 4) the associated accumulation and disappearance of metabolic intermediates. Often, the contaminant pool itself consists of several chlorinated solvents with separate and interactive biochemical needs. The existing models address some of the issues mentioned above. However, their ability to successfully predict biological fate of chlorinated solvents in nature is severely limited due to the various missing elements. This paper will provide a comprehensive review of the existing mathematical models. Limiting step(s), inactivation of critical enzymes, recovery action, energetics, and a framework for multiple degradative pathways will be presented as a comprehensive model.

Key words: bioremediation, enzyme kinetics, electron acceptors, metabolism.

Oral presentation in organic contaminants session.

62 • SURFACTANT-ENHANCED TRANSPORT OF HYDROPHOBIC ORGANIC COMPOUNDS

H.M. Gaber, W.P. Inskeep, and J.M. Wraith, Department of Plant, Soil, and Environmental Sciences, Montana State University, Bozeman, MT, 59717

Many surfactants enhance the apparent water solubilities of hydrophobic organic compounds (HOCs) and may be useful in remediation of contaminated soils or aquifers. Several studies have shown that surfactants enhance the transport of HOCs by reducing the amount sorbed to soils, especially when surfactants are added with the HOC in the influent solution. However, remediation practices will generally involve application of surfactant after HOCs have "equilibrated" with potential sorbing phases. Consequently, the objective of this study was to compare the effectiveness of several surfactants for enhancing transport of four representative organic contaminants when surfactants were applied with the HOC or after the HOC was sorbed by the soil. Miscible displacement experiments were performed using a subsurface sandy loam soil (Creston, MT) under steady-state saturated flow conditions at a pore water velocity of xx cm hr^-1. The transport of ¹⁴C-labeled DDT, phenanthrene, pentachlorophenol (PCP), and 1,2,4-trichlorobenzene (TCB) was monitored in the absence and presence of four different surfactants (Triton X-100, Tween 80, lignosulfonic acid, and hexacyclodextrin) under conditions where the surfactants were added either with the HOC in the initial pulse solution, or after the HOC pulse was applied. In both cases, our results show that surfactants enhance the transport and recovery of HOCs. However, the recoveries of HOCs were much lower when surfactants were applied after HOC sorption than when surfactants were mixed with the HOC prior to application. Although our results support the use of surfactants for enhanced solubilization and subsequent transport of HOCs, the recovery of HOCs from a contaminated soil will likely be much lower than predicted based solely on partition coefficients of HOCs in the presence and absence of surfactant. Several factors such as desorption kinetics of aged contaminants, and ability of surfactants to access sorption domains may be important in determining the overall effectiveness of surfactant-based remediation technologies.

Key words: surfactants, transport, sorption, remediation, hydrophobic organic compounds.

Oral presentation in organic contaminants session.

63 • SOLVENT EXTRACTION FOR REMEDIATION OF SOILS AT WOOD TREATMENT SITES

Q. Yan¹, S. Kapila¹, A.F. Yanders², and A.A. Elseewi³, ¹Department of Chemistry and Center for Environmental Science and Technology, University of Missouri-Rolla, Rolla, MO, 65409-0010, ²College of Arts and Science, University of Missouri-Columbia, Columbia, MO, 65211, and ³Environmental Solutions Technologies, Inc., and Department of Soil Sciences, University of California-Riverside, Riverside, CA, 92507

In recently proposed regulatory guidelines (40CFR761), the United States Environmental Protection Agency allows remediation of polychlorinated biphenyl (PCB) contaminated sites with ambient temperature solvent extraction. This option holds promise for removal of organic contaminants at wood treatment sites. A study was undertaken to evaluate the effectiveness of solvent extraction coupled with photodegradation for removal and destruction of selected organic contaminants in soils from a wood treatment site. The process was evaluated through bench scale laboratory experiments and semi-pilot scale field experiments with one-half to two ton capacity batch extractors. A binary solvent mixture containing alkanes and butanol yielded the highest extraction efficiencies which ranged up to 95% for contaminants such as polynuclear aromatic hydrocarbons (PAHs), pentachlorophenols (PCPs), and polychlorinated dibenzo-p-dioxins (PCDDs). The contaminant bearing solvent was subjected to solar irradiation. Polychlorinated aromatics were readily degraded; e.g., half-life of octachloro dibenzo-p-dioxin was found to be less than 28 minutes. The residual PAHs in the solvent mixture were removed with activated carbon and the solvent was recycled for subsequent soil extractions.

Key words: solvent extraction, soil remediation, photodegradation.

Oral presentation in organic contaminants session.

64 • SURFACTANT-ENHANCED DISSOLUTION OF NONAQUEOUS PHASE LIQUIDS IN SANDY AQUIFER MATERIALS-EFFECTS OF DIMENSIONALITY AND SCALE

J.E. Ewing and T.H. Illangasekare, Department of Civil Engineering, University of Colorado at Boulder, Boulder, CO, 80309

Surfactants have been used for years in the petroleum industry for enhanced mobilization of oil from petroleum reservoirs. Because mobilization of nonaqueous phase liquid (NAPL) contaminants can exacerbate the problem by increasing the zone of contamination, mobilization can be undesirable. Surfactants can also be used to enhance the dissolution of NAPLs without mobilization. This enhanced dissolution can then be used to augment "pump-and-treat" remediation schemes by decreasing times for clean up. Prior experimental research on surfactant-enhanced dissolution has been confined to a small scale. The objective of this research is to investigate the effects of dimensionality and aquifer heterogeneities on surfactant-enhanced dissolution for both small and large scales. This paper presents the results from one- and two-dimensional surfactant-enhanced dissolution experiments. Mass transfer rate coefficient dependencies on porous media properties, Reynolds number, and NAPL saturation were determined for small column experiments. These results were compared with experiments conducted in a small two-dimensional dissolution cell and a pilot scale flume. Comparisons focused on the key parameters obtained from small experiments that are needed in modeling large scale behavior of surfactant-enhanced dissolution in heterogeneous porous media.

Key words: ground water, nonaqueous phase liquids, surfactants, dissolution, up-scaling.

Oral presentation in organic contaminants session.

Barriers and Transport · Coronado Room

65 • CONTAINMENT OF HEAVY METAL AND CHLORINATED ORGANIC SOLVENT CONTAMINATION USING SUBSURFACE BIOBARRIERS

G.A. James¹, B.K. Warwood¹, K. Horrigan¹, R. Hiebert², A.B. Cunningham¹, and J.W. Costerton¹, ¹Center for Biofilm Engineering, Montana State University, Bozeman, MT, 59717, and ²MSE, Inc., P.O. Box 4078, Butte, MT, 59702

The use of biobarriers, formed in situ by microbial biomass and extracellular products, to retard the migration of ground water contaminants was examined using sand-packed columns and pilot-scale Iysimeters. Biobarrier formation was accomplished by injection of a starved bacterial inoculum, followed by nutrient stimulation. Exposure of biobarriers established in columns to relevant concentrations of heavy metals (1 ppm strontium or cesium) or a chlorinated organic solvent (50-300 ppm carbon tetrachloride) did not have a deleterious effect on biobarrier integrity. The presence of microbial barriers reduced contaminant flux by 96-99%. Pilot scale Iysimeters were designed and manufactured to facilitate evaluation of biobarrier performance in a two-dimensional configuration. Injection ports for nutrient and bacterial addition were downstream from a constant head hydraulic flow reservoir. The hydraulic flow simulated ground water flow through a contaminated subsurface formation, while the injection ports simulated wells drilled down-gradient from a contaminated site. Lysimeter characterization studies using chloride tracers revealed flow heterogeneities (i.e., channeling), indicating simulation of a three-dimensional flow configuration. Following injection of starved bacteria and nutrient resuscitation, a consistent flow reduction of 90 to >99% was achieved over a 60 day period. Biobarriers formed in the Iysimeters have shown no ill effects due to the continuous presence of 1 ppm strontium. These results suggest the use of microbial barriers is a feasible technology for the containment of ground water contaminants. Furthermore, biological containment has the potential to be linked to contaminant biosequestration or biodegradation.

Key words: biobarrier, ground water ultramicrobacteria, bioremediation.

Oral presentation in barriers and transport session.

66 • BIOFILM BARRIERS IN SOIL

M. Dennis¹, J.P. Turner¹, J. Chase², L.A. Bulla², and Y.A. Osman², ¹Department of Civil & Architectural Engineering, University of Wyoming, Box 3295 University Station, Laramie, WY, 82071, and ²Department of Molecular Biology, University of Wyoming, Box 3354 University Station, Laramie, WY, 82071

A study was conducted to evaluate the feasibility of creating low-permeability waste containment barriers using soil treated with bacteria and appropriate nutrients to create a plugging biofilm. The study consisted of bench-scale laboratory tests to evaluate changes in soil hydraulic conductivity caused by the formation of biofilms. Sandy soils with initial hydraulic conductivities ranging from 10^-5 cm/sec to 10^-3 cm/sec were tested to determine whether a biofilm could be formed by the addition of bacteria and nutrient solution and, if so, to measure changes in hydraulic conductivity. Saturated hydraulic conductivities (k_sat) were measured using a flexible wall permeameter. Bacteria were mixed with the soil, followed by soil compaction to maximum dry density at optimum moisture content. The compacted specimen was then placed in a permeameter cell and permeated with a nutrient solution. Hydraulic conductivity measurements were made at various time intervals. Several bacterial strains were evaluated, including Klebsiella pneumoniae, Beijerinckia lacticogenes, and Beijerinckia indica. Significant reductions in k_sat, over several orders of magnitude, were observed for all bacterial strains. Initial hydraulic conductivity of the soil strongly influences the degree of plugging. Results of this study demonstrate that biofilm barriers may be a feasible technology for waste containment in soils with hydraulic conductivities one to two orders of magnitude greater than the EPA regulatory definition of "low permeability," which is 10^-7 cm/sec. Further research is necessary to evaluate biofilm barriers at a scale that is more representative of field conditions. Experience gained during this study has contributed to our knowledge of laboratory procedures required for testing soils treated with bacteria and nutrient solutions. For example, the traditional use of filter paper at the ends of hydraulic conductivity specimens treated with biofilm-producing bacteria results in extensive plugging of the filter paper, followed by plugging of the soil, which will not necessarily occur if the filter paper is not present. These and other experimental aspects of this study are presented and discussed.

Key words: biofilm, hydraulic conductivity, barriers, waste containment.

Oral presentation in barriers and transport session.

67 • THE EFFECT OF ULTRA PURE WATER FLUSHING ON BACTERIAL TRANSPORT IN NATURAL SEDIMENTS

T.A. Camesano and B.E. Logan, Department of Chemical and Environmental Engineering, The University of Arizona, Tucson, AZ, 85721

New methods of aquifer biorestoration may require the injection of microbes with the capability to degrade specific subsurface pollutants. Such schemes can only be effective, however, if methods are developed to increase bacterial transport over large distances, since bacteria will move only a few centimeters to a meter in an aquifer without assistance. One way to enhance transport is by increasing the electrostatic repulsive layer between the bacteria and the soil particles. Flushing the column with ultra pure water (very low ionic strength) will increase the electrostatic repulsive layer between the bacteria and the soil surface and reduce the frequency of attachment. Previous experiments using ultra-clean glass beads and quartz had shown that low ionic strength water could increase bacterial transport under these conditions. Using a filtration equation, we empirically determined a collision efficiency, a, for the bacteria in our columns, with a defined as the ratio of bacteria sticking to the soil grains to bacteria hitting the sediment. A significant decrease in a for bacteria injected into the columns was seen when columns were flushed with ultra pure water as compared to columns flushed with only artificial ground water. The collision efficiency decreased from 2.31 x 10^-2 (for AGW) to 4.74 x 10^-3 (for ultra pure water), as shown below for a 7-cm column. An a less than 10^-3 will permit bacteria to travel further than 10 m in a typical aquifer. Ultra pure water flushing appears to be an effective way of mobilizing biocolloids. This could be of great benefit as a remediation technique, since low ionic strength water is easily obtained and not hazardous to the subsurface environment. Effect of Ultra Pure Water Flushing on Bacterial Retention

Key words: bacteria, biocolloid, filtration, transport.

Oral presentation in barriers and transport session.

68 • INCREASING THE DIVERSION LENGTH OF CAPILLARY BARRIERS

R.E. Pease and J.C. Stormont, Civil Engineering Department, University of New Mexico, Albuquerque, NM, 87131

The diversion length of a capillary barrier is increased with the introduction of a well-sorted sand layer immediately above the fine/coarse interface. Various soils were evaluated as "transport layer" materials using numerical simulation. Infiltration and evapotranspiration were simulated for one year of an Albuquerque, NM, climate. The infiltration and evapotranspiration varied daily in the simulations with the use of a daily effective flux. The baseline simulation without a transport layer diverted moisture 5 m. The diversion length was increased to 37 m with the use of a construction sand layer, and a layer of 100-mesh sand did not allow any moisture to penetrate the barrier. The simulation results are consistent with the field test results of Stormont (Stormont, J.C., 1995. The performance of two capillary barriers during constant infiltration. Submitted to Annual ASCE Convention, San Diego, CA, 1995, October, 1995), which indicate an increase of capillary barrier diversion length with the introduction of a sand transport layer. A capillary barrier may be an inexpensive and stable alternative or addition to conventional cover systems for semi-arid regions.

Key words: capillary barrier, diversion length, landfill cover, numerical simulation.

Oral presentation in barriers and transport session.

Program Three Wednesday, May 22, 1996 Modeling and Transport · Coronado Room

69 • STOCHASTIC MODELING OF SOLUTE TRANSPORT IN A FRACTURED MEDIUM

M.J. Butler, V.R. Schaefer, and J.C. Tracy, Northern Great Plains Water Resources Research Center, South Dakota State University, Brookings, SD, 57007

A field study was conducted at the Sioux Falls, South Dakota, Runge Landfill to determine the effects of fractures on the hydraulic conductivity and solute transport potential of glacial till deposits. An infiltration trench system was constructed at the Runge site during the summer of 1993. Chloride tracer was injected into the trench system during the summer of 1995. Several wells within the trench system were periodically sampled providing information on the transport of the tracer. In addition, to compute the bulk hydraulic conductivity at the site, slug tests were conducted at each sampling well using the Hvorslev and Bouwer-Rice analysis methods. Estimates of the hydraulic conductivity and the results of the tracer study are then used to calibrate both deterministic and stochastic transport models. Model results are analyzed to determine which approach produces more reliable predictions of solute transport in a fractured clay till.

Key words: landfill, clay till, fractured media, stochastic transport.

Oral presentation in modeling and transport session.

70 • MODELING FATE AND TRANSPORT OF ATRAZINE IN THE SATURATED-UNSATURATED ZONE OF SOIL

P.K. Allepalli and R.S. Govindaraju, Department of Civil Engineering, 119 Seaton Hall, Kansas State University, Manhattan, KS, 66506

Atrazine (2-chloro-4-ethylamino-6-isopropylamine-s-triazine) is a widely used herbicide for selective control of broadleaf and grassy weeds, and has been detected in ground water. Experimental work in this area shows that the degradation of atrazine is dependent on the soil water content. Of specific interest to this study is the influence of fluctuating water tables on atrazine degradation. A 1-D finite-difference model has been developed to study saturated-unsaturated water movement and transport of atrazine with kinetic-nonlinear adsorption and water content-dependent degradation. The water movement and chemical transport have been decoupled, such that water fluxes are treated as being independent of the chemical concentrations. Model results of the fate and transport of atrazine for various physical scenarios will be presented.

Key words: atrazine, modeling, saturated-unsaturated, degradation.

Oral presentation in modeling and transport session.

71 • FIELD VALIDATION OF THE BACKWARD-IN-TIME ADVECTION DISPERSION THEORY

J.L. Wilson¹ and J. Liu², ¹Department of Earth and Environmental Science, New Mexico Institute of Mining and Technology, Socorro, NM, and ²Environmental Systems and Technology, Inc., Blacksburg, VA

We have recently developed a theory that can be used to locate the source of contamination captured by a pumping well. Accounting for advection, dispersion, linear-equilibrium sorption, aquifer heterogeneity, and regional natural recharge, the theory is based on the concept of travel time probability. This probability describes the time for a particle to travel from a source location to the pumping well, and can be directly computed by solving partial differential equations backwards-in-time, with a third type probability boundary condition at the pumping well. We apply a two-dimensional version of the theory, implemented numerically using the Laplace Transform Galerkin method, to the analysis of a recent tracer test conducted at the Borden Site, in Ontario, Canada (Linderfelt and Wilson, 1994). The test was designed to validate common conceptual models of pumping well capture zones. Tracers were injected at 15 locations upgradient of a pumping well. Their arrival in the well was observed with weekly concentration measurements. A single two-dimensional backward-in-time simulation was used to predict separate travel time probabilities for each injection site. These were compared to normalized experimental breakthrough curves, and arriving tracer mass was assigned to 11 of the injection locations. Tracer from four injection sites was predicted to miss the pumping well. The assignments of mass and source location, and the predicted tracer recovery, compare favorably with independent interpretations of the experiment which were based on multiple three-dimensional forward simulations (Linderfelt, 1994). Satisfactory performance of the method on the field test data supports its validation as a standard tool, and demonstrates its practical use.

Key words: backward-in-time simulation, advection dispersion, travel time probability.

Oral presentation in modeling and transport session.

Nonaqueous Phase Liquids · Coronado Room

72 • DIMENSIONALITY AND HETEROGENEOUS EFFECTS ON ENHANCED LNAPL RECOVERY USING HOT WATER FLOODING

K.O. Pytte and T.H. Illangasekare, Department of Civil, Environmental, and Architectural Engineering, University of Colorado at Boulder, Boulder, CO, 80309

Thermal processes, such as hot water flooding and steam injection, have essentially been used exclusively by the petroleum industry as a means of enhanced oil recovery (EOR) from petroleum reservoirs. Similar techniques also show promise as a remediation technique for the recovery of nonaqueous phase liquids (NAPLs) from contaminated soils in the subsurface. Previous laboratory studies have shown that an increase in temperature tends to markedly increase the mobilization and direct recovery of contaminants from soil samples. However, these studies have dealt only with one-dimensional, homogeneous systems or confined petroleum reservoirs. To determine the applicability of these techniques to unconfined aquifer remediation, heterogeneous and scaling issues have to be addressed. The objective of this research is to determine the effectiveness and feasibility of using hot water flooding to recover entrapped NAPLs under micro- and macroscale saturations at various scales and system complexities. The use of water flooding as a delivery mechanism for other remediation techniques was also investigated. This paper presents the results from NAPL mobilization experiments using various scales of interest. Using a vacuum pump oil as a lighter-than-water contaminant, the recovery efficiencies of various temperature hot water floods in homogeneous and heterogeneous systems were determined for soil column, small two-dimensional, and pilot-scale experiments. These efficiencies were compared to determine the practicality of this remediation technique in more realistic multi-dimensional and heterogeneous field systems. The flow paths of the hot water were also monitored to determine the usefulness of hot water flooding as a delivery mechanism for the different systems. In addition, theoretical analysis and modeling tools were used in an attempt to understand the scaling issues involved in the field implementation of this recovery scheme.

Key words: ground water, nonaqueous phase liquids, remediation, thermally-enhanced recovery, up-scaling.

Oral presentation in nonaqueous phase liquids session.

73 • FATE AND TRANSPORT OF RESIDUAL NAPLS UNDER FLUCTUATING WATER TABLE CONDITIONS

W. Han, L.N. Reddi, and M.K. Banks, Department of Civil Engineering, Seaton Hall, Kansas State University, Manhattan, KS, 66506

A mathematical model will be presented to simulate the fate and transport of lighter-than-water NAPLs (LNAPLs) both in saturated and vadose zones. LNAPLs usually stay above the water table and form large, continuous pools. As the water table fluctuates due to seasonal recharge and water pumping, a smear zone is formed as a result of LNAPL entrapment both below the water table and in the vadose zone. Characterization of the behavior of the LNAPLs in these two areas includes their transportation, volatilization, dissolution, and biodegradation. It is assumed that the movement of the water table with the LNAPL pool maintains a constant speed, and the range of the movement remains the same all the time. Equilibrium conditions are assumed to be reached before successive fluctuation of the water table. The movement of the pool recharges the ganglia which have been depleted by volatilization in the vadose zone, and by dissolution and biodegradation in the saturated zone. The size of ganglia is represented by a set of effective diameters. In the vadose zone, the Hamaker method is applied to calculate the mass loss of ganglia through volatilization and the change of their size distribution with time. An advection-dispersion equation which is modified to include ganglia dissolution and biodegradation is used to simulate the time-dependent process in 2-D saturated zone, where a constant rate of 1-D water flow is maintained. The mass loss of both ganglia and pools within the saturated zone is calculated . Through the model, it is possible to predict the ganglia size distribution both in the vadose and saturated zones before and after the water table movement, and the life time of LNAPLs.

Key words: dissolution, volatilization, lighter-than-water nonaqueous phase liquid ganglia, lighter-than-water nonaqueous phase liquid pool.

Oral presentation in nonaqueous phase liquids session.

74 • DNAPL MIGRATION IN A COMPLEX MULTI-AQUIFER SYSTEM

D.B. Stephens¹, J.A. Kelsey¹, M.A. Prieksat¹, M.G. Piepho¹, M.D. Ankeny¹, and C. Shan², ¹Daniel B. Stephens & Associates, Inc., 6020 Academy Road N.E., Suite 100, Albuquerque, NM, 87109, and ²Lawrence Berkeley Laboratory, Mail Stop 505, Berkeley, CA, 94720

A laboratory experiment was conducted to demonstrate the behavior of DNAPL (1,1,1-trichloroethane) in a complex aquifer system. The system simulated consists of two unconfined aquifers separated by a low permeable bedrock perching layer that contains a fracture. In contrast to previous work by other researchers of DNAPL migration in hydrostatic conditions, in this experiment, prior to and during the DNAPL release, ground water flow occurs from the upper to lower aquifer via the fracture. Although the experiment illustrates that DNAPL may migrate rapidly in narrow pathways, the observations were predicted rather well by a simplified analytical solution and a numerical simulation with the multi-phase flow and transport code TOUGH-2. With recharge to the lower aquifer occurring through the fracture, a DNAPL pool did not develop prior to its entry into the fracture.

Key words: nonaqueous phase liquids, transport modeling.

Oral presentation in nonaqueous phase liquids session.

Contaminant Fate and Transport · Coronado Room

75 • BENCH-SCALE INVESTIGATIONS ON VIBRATORY MOBILIZATION OF IMMISCIBLE LIQUID GANGLIA

L.N. Reddi, J. Nichols, and H. Wu, Department of Civil Engineering, Seaton Hall, Kansas State University, Manhattan, KS, 66506

The feasibility of vibratory mobilization of residual LNAPL (nonaqueous phase liquid lighter-than-water) ganglia was well established in previous studies by the principal author. In this presentation, results from bench-scale experiments will be reported to provide a practical understanding of the technology. The experiments were conducted using a probe-type vibrator to evaluate the changes in relative density of the soil-NAPL medium and the distribution of ganglia in the vibrated zone. In some experiments, the probe-type vibrator was housed in a 'vibroflot' to integrate the pumping mechanism and thereby to simulate the field implementation process. It was shown that the distribution of ganglia in the vibrated zone was governed not only by the relative density variation but also by the uniformity of flow gradients. Non-uniform flow rates in the zone around the vibroflot was shown to result in clean-up of some areas and in accumulation of ganglia (exceeding initial residual volumes) in other areas. The results from the experiments supported an integrated approach where the vibrator was augmented with a pumping mechanism yielding uniform and predictable flow gradients in the vibrated zone.

Key words: relative density, vibrations, lighter-than-water nonaqueous phase liquid ganglia.

Oral presentation in contaminant fate and transport session.

76 • THE BINDING OF ORGANIC CONTAMINANTS TO HUMIN

S.D. Kohl and J.A. Rice, Department of Chemistry & Biochemistry, South Dakota State University, Brookings, SD, 57007-0896

It has been recognized for some time that a significant fraction of most organic contaminants that are introduced into a soil or sediment become rapidly and irreversibly bound to humin fraction of naturally-occurring organic matter. The insolubility of humin in essentially any solvent has made the study of these "bound residues" difficult. The ability to fractionate humin into four components (extractable lipids, bound-humic acid, bound lipids, and mineral matter) using the methyl-isobutylketone partitioning procedure is providing new insights into the phenomenon of bound residue formation and the fate of anthropogenic organic compounds in neutral environments. Results will be presented describing the formation of bound residues in humin for a variety of anthropogenic organic compounds including atrazine, 2,4-D, DDT, PCBs, and PAHs from studies using ¹⁴C-labeled compounds. The distribution of the radioactivity among the components of humin will be compared and contrasted. Potential binding mechanisms will be discussed.

Key words: humin, bound residue, 2,4-D, atrazine, DDT, polycyclic aromatic hydrocarbons, polychlorinated biphenyls.

Oral presentation in contaminant fate and transport session.

77 • CONTAMINATED SOIL RECOVERY RATE OF A LEACHER COLLECTION SYSTEM

D.L. Rainey and P.-C. Yuan, Department of Technology & Industrial Arts, Jackson State University, Jackson, MS, 39217

Leachate is defined as any liquid, including any suspended components in the liquid, that has seeped, drained, or percolated through a collection system. Within the past few decades leachate collection systems have become valuable tools to scientists in the field of Environmental Engineering. Vertical column tests have caused collection systems to become even more advanced. They are used by researchers to serve in such capacities as laboratory models for simulating different types of transport in porous media.

These two experiments consisted of: 1. various tests to study the column contact time and superficial velocity of water, and 2. percolation of the tracer element, Benzoic Acid, through a sand-compacted column.

An interchangeable vertical column was constructed of piping material to serve as the testing apparatus. In the first phase, a measure of the column contact time and superficial velocity were attained by pouring one or two liters of water down the column and taking time measurements at different levels. In the second experiment two hundred milliliters of Benzoic Acid and one or two liters of water, depending on the size of the column, were poured down the column. Samples were then taken at designated levels. The test samples were then titrated to measure the amount of base it would take to neutralize the acid.

Key words: leachate, contaminated soil, recovery, reclamation, percolation.

Oral presentation in contaminant fate and transport session.

PCBs and Mohawk Nation Superfund Site · Coronado Room

78 • AN OVERVIEW OF SUPERFUND BASIC RESEARCH OF PCB POLLUTION OF THE MOHAWK NATION

B. Bush^1,2, A.C. Casey¹, E. Fitzgerald¹, and K. Jock³, ¹School of Public Health, State University of New York at Albany, Wadsworth Center, New York State Department of Health, Albany, NY, 12201-0509, ²e-mail: bbush@wadsworth. ph.albany.edu, and ³Environmental Division, St. Regis Mohawk Tribe, Hogansburg NY, 13655

There are four major sources of pollution near the power dam on the St. Lawrence River between Cornwall, Ontario, and Massena, NY. The Akwesasne Mohawk Nation straddles one international border between Canada and the United States and also three borders between Ontario, Quebec, and NY State, so that a total of five non-Mohawk governments are working with the Mohawks. One of the great challenges of this project has been learning, and teaching students, to work with an environmental task force drawn from the whole Mohawk Nation.

Ultra-trace congener-specific PCB analysis by gas chromatography with electron capture detection has allowed new important sources of PCB to be delineated. These have been plotted on a geographical information system (Mapinfo) so that contamination of water, sediment, soil, vegetables, fish, and seasonally-variable air pollution may be related to observed contamination of the blood and breast milk of Mohawks.

In 1995, contaminated river sediment bordering the General Motors foundry was dredged and dumped on land. Problems encountered, solved, and produced by this action will be discussed.

Key words: polychlorinated biphenyls, minority population, remediation.

Oral presentation in PCBs and Mohawk Nation Superfund site session.

79 • PHOTOCATALYTIC DEGRADATION OF PCBs IN AQUEOUS TiO₂ SUSPENSIONS

C.S. Hong, Y. Wang, I.W. Huang, and B. Bush, School of Public Health, State University of New York at Albany, Wadsworth Center, New York State Department of Health, Albany, NY, 12201-0509

A generator-column technique was used to prepare aqueous solutions of PCBs. The degradation of 2-chlorobiphenyl (2-CB), Aroclor 1248, Aroclor mixture (1221, 1016, 1254, and 1260), and St. Lawrence River water by simulated sunlight or sunlight has been investigated in the presence of aqueous suspensions of TiO₂. The effect of pH, TiO₂ concentration, humic acid, initial PCB concentration, and added oxidants (H₂O₂, KIO₄, K₂S₂O₈, and NaClO) have been studied. Biphenyl-2-ol, monochlorophenyl phenols, 2-chlorobenzaldehyde, 2-chloroacetophenone, benzoic acid, and 2-chlorobenzoic acid were formed as the principal intermediates. Formate and acetate were formed as products during the latter stages of photooxidation. The kinetics of the disappearance of 2-chlorobiphenyl, formation and decomposition of intermediates, and CO₂ evolution were also investigated. The degradation of 2-CB followed pseudo-first order kinetics. The photocatalytic pathway of 2-CB is likely to involve an attack of OH radicals on the phenyl ring. After addition of OH radicals to the aromatic ring, the ring opens, and CO₂ is ultimately evolved via many oxidation steps. Complete mineralization of 2-CB to CO₂ was observed with the addition of H₂O₂.

Key words: photocatalysis, polychlorinated biphenyls, TiO₂, remediation.

Oral presentation in PCBs and Mohawk Nation Superfund site session.

80 • SUPERCRITICAL FLUID TECHNOLOGY FOR PCB/PAH-CONTAMINATED SOIL REMEDIATION

L.L. Tavlarides, P. Chen, W. Zheu, J. Zhang, and G. Anitescu, Chemical Engineering and Material Sciences Department, Syracuse University, Syracuse, NY, 13244

A supercritical fluid process to remediate PCB- and PCB/PAH-contaminated soils/sediments consisting of supercritical CO₂-cosolvent extraction followed by supercritical water oxidation (SCWO) of the soil/sediment extract is proposed. Supportive studies include laboratory scale extractions, laboratory scale water oxidations, and bench scale extractions. Surrogate laboratory spiked samples and native contaminated St. Lawrence and Hudson River sediments have been investigated. SCWO experiments with 4-monochlorobiphenyl/methanol are in progress to determine destruction efficiencies and reaction kinetics. Solubility studies are also in progress for SC-W₂/cosolvent-PAH systems to define suitable systems for PAH and PCB extractions. The proposed process, conditions of operation, and current results will be discussed.

Key words: supercritical, polychlorinated biphenyls, polycyclic aromatic hydrocarbons.

Oral presentation in PCBs and Mohawk Nation Superfund site session.

81 • APPLICATION OF REMEDIAL TECHNOLOGIES AT THE MOHAWK NATION SUPERFUND SITE

R.J. Scrudato, Environmental Research Center, Room 319, Piez Hall, SUNY at Oswego, Oswego, NY, 13126

A summary of the remedial technologies being used and considered for the General Motors National Priority List site located near Massena, NY, will be discussed in light of PCB/sediment partitioning, volatility, solubility, and anaerobic biodegradability. The majority of the PCBs associated with the Massena area sediments are concentrated in the finer grained, organic fractions. On drying at ambient temperatures, these sediments lose up to 25% of the total PCB concentration through volatilization, and volatile losses correlate well with dehydration of the sediments. Advanced oxidative processes (AOP) including photodegradation and an electrochemical peroxidation have been used to degrade more than 90% of the PCBs in sediment slurries. AOP destruction correlates with PCB solubility as evidenced by relative congener susceptibility to degradation. Although it is evident that PCB-contaminated sediments collected from the Massena area have experienced anaerobic degradation, this process is slow and limited.

Key words: remediation, bioremediation, polychlorinated biphenyls, electrochemical.

Oral presentation in PCBs and Mohawk Nation Superfund site session.

Program Three Thursday, May 23, 1996 Risk Assessment · Coronado Room

82 • DEVELOPMENT & IMPLEMENTATION OF A HIGH MOUNTAIN DESERT ECOLOGICAL RISK ASSESSMENT

M.E. Maly¹ and C. Marsh², ¹U.S. Army Environmental Center, ATTN: SFIM-AEC-IRB, Aberdeen, MD, 21010-5401, and ²Rust Environment & Infrastructure, 743 Horizon Court, Grand Junction, CO, 81506

In compliance with both the Comprehensive Environmental Response, Compensation, and Liability Act (CERCLA) and the Resource Conservation and Recovery Act (RCRA), an installation-wide Ecological Risk Assessment (ERA) was developed, planned, and implemented at the Tooele Army Depot in central Utah. Tooele's installation restoration program is conducted under both CERCLA and RCRA due to its National Priorities Listing and the issuance of a RCRA Corrective Action Permit by the State of Utah. Both laws require that clean-ups be protective of both human health and the environment.

Tooele's unique high western, semi-arid climate and predominantly terrestrial ecosystem had to be carefully molded into a conceptual plan for implementation of the ERA. At the start of the project in 1993, very little regulatory guidance and no Army guidance was available to help scope the study which was to evaluate the risk posed by 54 sites under investigation at the 24,732 acre facility. The Army worked closely with the U.S. Environmental Protection Agency Region VIII Ecological Technical Assistance Group (ETAG) to determine the proper approach and depth of study.

This paper describes the unique Tooele environment which had to be taken into consideration during the planning process, the partnering with the regulators to achieve an approved work plan, the ERA's scope, and the resulting findings, conclusions, and recommendations. In particular, the talk will focus on how the assessment and measurement endpoints were selected after review of the site ecology, including consideration of major food chains, key species, and potentially-occurring threatened and endangered species.

Key words: ecological risk assessment, installation restoration.

Oral presentation in risk assessment session.

83 • ESTROGENIC AND PROGESTAGENIC SCREENING OF POLLUTANTS IN VITRO USING ENDOMETRIAL AND BREAST CANCER CELL LINES

J. Garey and M.S. Wolff, Department of Obstetrics, Gynecology, and Reproductive Science and Department of Community Medicine, Mt. Sinai School of Medicine, New York, NY, 10019

A variety of waste products commonly found as contaminants of waterways have been discovered to act as sex hormone analogues. In this investigation we have analyzed organochlorines, trace elements, plasticizers, and PCB congeners for estrogenic or antiestrogenic and progestagenic or antiprogestagenic activities using in vitro screening. The endometrial cancer cell line, Ishikawa Var-1 (estrogenic), and the breast cancer cell line, T47D (progestagenic), enabled us to detect hormonal activity with increased production of alkaline phosphatase as a colorimetric endpoint. Estrogenic activity was detected among many compounds, including the organochlorines kepone, 1-hydroxychlordene, endosulphan, and o,p'-DDT, and the plasticizer bisphenol A. Confirmation of hormonal activity was achieved through the addition of a pure antihormone to the test substances. To date, no antiestrogenic, progestagenic, or antiprogestagenic activities have been detected among contaminants tested. Ultimately, these screening systems will be used to evaluate sediment extracts from the Hudson River bight. We hope to predict hormonal activity of typical pollutant mixtures and thus provide useful information for remediation efforts.

Key words: hormonal activity, organochlorines, plasticizers, polychlorinated biphenyls.

Oral presentation in risk assessment session.

84 • UPTAKE OF TRICHLOROETHYLENE BY EDIBLE GARDEN PLANTS

W. Schnabel, A. Dietz, J. Burken, J.L. Schnoor, and P.J.J. Alvarez, Department of Civil and Environmental Engineering, University of Iowa, Iowa City, IA, 52242-1527

Edible garden plants (carrots, spinach, and tomatoes) were grown to maturity inside continuous air-flow bioreactors, and were regularly irrigated with synthetic ground water containing ¹⁴C-labeled TCE at two dose levels (approximately 560 mg/l for high dose and 140 mg/l for low dose reactors). Following TCE exposure for 31 to 106 days, different plant tissues and bioreactor compartments were analyzed for the ¹⁴C label. Samples were analyzed by combustion with a Biological Oxidizer followed by liquid scintillation counting. Samples were also analyzed for total TCE and for the potential presence of TCE metabolites using Purge & Trap Gas Chromatography. Both aerobic and anaerobic potential transformation products were included in the analysis. Radiolabel recoveries ranged from about 50% for low-dose reactors to about 70% for high-dose reactors. Most of the recovered ¹⁴C label volatilized (74% to 95%) and was found in the Orbo^R tubes that were used to capture the air exiting the reactors. A portion of the recovered label (5%-25%) was found sorbed to the soil. Although the percentage of the recovered ¹⁴C label found in plant material was relatively small (1% to 2%), the concentration of ¹⁴C label in edible plant tissue was higher than in the surrounding soil. On a wet weight basis, accumulation factors (TCE concentration in edible tissue divided by TCE concentration in surrounding soil) ranged from 2.6 in the high dose tomato reactors to 32 in the low dose spinach reactors. If the radiolabel found by combustion of plants were TCE, the concentrations in edible tissue would range from 152 ppb for the high-dosed tomatoes to 580 ppb for the high-dosed spinach. However, neither TCE nor its commonly reported transformation products were detected by Purge & Trap GC-MS. Furthermore, the ¹⁴C label found in plant tissue could not be extracted into the organic solvent CS₂ or into the inorganic solvent 10N H₂SO₄. This suggests that TCE was taken up, transformed, and bound to the plant material. Further research into the chemistry and toxicology of this bound residue would provide insight into the health effects associated with consumption of TCE-exposed plants. Research in this area could also forward the use of phytoremediation as a viable alternative for the clean up of TCE spills.

Key words: phytoremediation, vegetative uptake, bound residue.

Oral presentation in risk assessment session.

85 • CREATION OF THE ARMY'S BIOLOGICAL TECHNICAL ASSISTANCE GROUP: A HELP GROUP FOR ECOLOGICAL RISK ASSESSMENTS

M.E. Maly, U.S. Army Environmental Center, ATTN: SFIM-AEC-IRB, Aberdeen Proving Ground, MD, 21010-5401

To assist Army environmental project managers cope with new and complex issues surrounding Ecological Risk Assessments (ERAs), the U.S. Army Environmental Center (USAEC), in cooporation with several other Army organizations, established a Biological Technical Assistance Group (BTAG). The Army saw the need for a BTAG because the importance of ERAs had greatly increased over the last few years in clean-up programs being conducted under both CERCLA and RCRA Corrective Action.

Unlike the human health risk assessment, for which numerous guidance documents were available to help project managers focus on protecting human health, neither the regulatory agencies nor the Army had published much specific guidance on conducting ERAs back in the early to mid-1990's. In 1990, the EPA established BTAGs at each of their ten regional offices to help their remedial project managers cope with this quickly evolving requirement. In 1993, the USAEC recognized the Army's need for a similar assistance group and began organizing the Army's own BTAG. The Army BTAG has now been operating for two years, meeting on a monthly basis to assist restoration project personnel at both active and closing installations.

This paper will follow the creation of the BTAG in 1993, outline how the group functions and describe where the BTAG hopes to be in the years to come. Specific examples will be provided describing how the BTAG has assisted Army project personnel at numerous installations across the country.

Key words: ecological risk assessment, Army, restoration.

Oral presentation in risk assessment session.

86 • PERCEPTIONS OF ENVIRONMENTAL RISK IN THREE COMMUNITIES OF EL PASO, TEXAS

T. Byrd and J. VanDerslice, University of Texas-Houston School of Public Health at El Paso, 901 Education Bldg., UTEP, El Paso, TX, 79968

Perceptions of environmental risk were explored in three communities of El Paso, Texas, through a series of focus groups and a door-to-door survey of 300 residents. Included in the survey were questions about a) knowledge of environmental risks and the perceived level of risk, b) sources of information and source credibility, and c) general attitudes about risk, locus of control, and the government's ability to protect the population. The three communities, each of different SES, were compared for differences in risk perceptions, knowledge, and attitudes. In general, many respondents had no knowledge of many of the environmental risks mentioned. Perceived risk to self and family was consistently lower than perceived risk to the community as a whole, especially for risks that might be considered behavioral in nature. Surprisingly, only a small proportion of respondents were even aware of local and national environmental agencies. The media was by far the most common source of environmental risk information. These results demonstrate a clear need for improved environmental risk communication along the U.S.-Mexico border.

Key words: risk perception, risk communication, U.S.-Mexico border.

Oral presentation in risk assessment session.

87 • ARSENIC RISK AND REGULATION

B.P. Sullivan, Los Alamos Technical Associates Inc., 2400 Louisiana Blvd. N.E., Suite Building 1, Suite 400, Albuquerque, NM, 87110

On the basis of carcinogenic potency estimates developed by EPA and its prevalence in the environment relative to other natural and man-made carcinogens, arsenic (As) can arguably be considered one of the most serious environmental threats to human health. However, when considered across regulatory programs and environmental media, environmental standards for As are highly inconsistent in terms of levels of allowed risk. In particular, even though EPA estimates suggest that as many as 64 million household residents in the U.S. may be exposed to potentially health-threatening levels of arsenic in drinking water, the federal Safe Drinking Water Act (SDWA) mandates a Maximum Contaminant Level (MCL) for As that permits a carcinogenic risk level fully 1,000 times greater than that associated with the MCLs established for other known human carcinogens. The anomalous manner in which As is regulated as an environmental carcinogen can be directly attributed to its dual nature as a naturally-occurring element and a widespread industrial contaminant. The MCL for As is scheduled for reassessment, and depending on the outcome of that effort, as many as 13,000 public water treatment systems could experience a significant economic impact. This paper presents an overview of the scientific literature concerning As toxicology, epidemiology, and water treatment technology that will be considered by EPA during revision of the existing SDWA standard for As. The manner in which the As MCL is revised may also affect how it is regulated in other environmental media, as well as the way in which human health risks posed by other environmental carcinogens are both perceived and regulated in the future. These broader implications of the impending reassessment of environmental As are also discussed.

Key words: arsenic, environmental risk, water treatment.

Oral presentation in risk assessment session.

Program Four Tuesday, May 21, 1996 Analytical Methods · Santa Fe Room

88 • A SIMPLE INEXPENSIVE ASSAY FOR TOXIC CHEMICALS USING A BACTERIUM AS THE INDICATOR ORGANISM

J.L. Botsford¹, T. Hillaker¹, V. Homer², M. Gonzalez³, M. Benavidez³, F. Pacheco³, W. Steen³, O. Lucero⁴, and M. Mathews⁴, ¹Department of Biology, New Mexico State University, Las Cruces, NM, 88003, ²Fort Sumner High School, ³New Mexico State University, and ⁴students, Gadsden High School and Las Cruces High School

A simple test for toxic chemicals has been developed. The soil bacterium Rhizobium meliloti is combined with the toxic chemical. A tetrazolium dye, MTT (3-[4,5-Dimethylthiazol-2-yl]2,5-diphenyl-tetrazolium bromide) is added. The bacterium can reduce this dye causing the optical absorbance to increase dramatically. The increase can be determined with a simple spectrophotometer. Toxic chemicals and minerals inhibit the reduction of the dye. The assay has been compared with published results of tests using the Microtoxä, a microbiological test for toxic compounds using a bioluminescent marine bacterium. The assay offers another method to determine the toxicity of compounds, a method that is simple, rapid, and inexpensive.

Key words: toxic chemicals, assay, student involvement, bioremediation.

Oral presentation in analytical methods session.

89 • FLUORESCENT SILICA COLLOIDS FOR STUDYING CONTAMINANT TRANSPORT IN GROUND WATER

H.E. Nuttall^1,2, D. Smith¹, W. Whittenburg¹, and P. Reimus³, ¹Department of Chemical and Nuclear Engineering, University of New Mexico, Albuquerque, NM 87133, ²e-mail: nuttall@unm.edu, and ³Los Alamos National Laboratory

Understanding and quantifying the movement of contaminated ground water is an important but currently very costly step in DOE's remediation programs. The use of fluorescent dyed silica colloids to quantify ground water travel times and major flow paths is a new and innovative contribution to hydrology. Silica colloids are environmentally safe since most soils are composed primarily of quarts (silica) and feldspars. When injected into a ground water system, colloids will provide critical information on the maximum contaminant velocities. Colloids unlike tracer solutes will travel primarily through the major flow paths and be rejected from the smaller micro pores by both size and charge exclusion. These properties cause colloids to travel at the rate of the fastest moving contaminants.

In laboratory experiments, we showed that silica colloids migrate freely through soils, quarts packing, core columns, and natural fractures. The very low microsphere concentrations of fluorescent colloids were measured using a flow cytometer as the analytical tool. In recent tests at Los Alamos National Laboratory, colloids were shown to travel through fractures much faster than a conservative tracer such as bromide. We have also modeled in 3D the transport of colloids through natural fractures and compared the results to the experimental data. We are currently planning field experiments using these unique fluorescent silica colloids at an UMTRA site.

Key words: ground water, tracers, colloids, contaminate, soil.

Oral presentation in analytical methods session.

90 • MATERIAL CLASSIFICATION OF NONAQUEOUS PHASE LIQUID FROM 3D IMAGING DATA

H. Tahani¹, R.L. Peyton², S.H. Anderson², and C. Gantzer³, ¹Campus Computing, ²Department of Civil Engineering, and ³School of Natural Resources, University of Missouri-Columbia, Columbia, MO, 65211

Volume visualization has emerged as a promising field in the study of hazardous chemicals. Using a series of X-ray computed tomography (CT) images, volume data were constructed for simulation of hazardous chemical transport in heterogeneous soil cores. The volume data were also used to evaluate the spatial distribution of nonaqueous phase liquid (NAPL) in sand. To display and/or analyze the chemical concentration in the volume data, the images before the injection of the chemical are subtracted from the images subsequent to the injection of the chemical. At present, there has been no direct classification of chemicals in a volume data.

Material classification is the key step in creating images from volume data. Good classification techniques, based on properties of the objects and characteristics of the CT images, not only create good visual effects for displaying the volume data on the 2D computer screen, but also improve the accuracy of the measurement of displayed objects. In this paper, a new classification algorithm based on pattern recognition techniques is proposed for displaying volume data for NAPL using a sequential series of CT images of a sand core. As a result of this classification process, more accurate measurements, evaluation, and analysis can be done.

Key words: nonaqueous phase liquids, CT imaging, volume data, classification.

Oral presentation in analytical methods session.

91 • DEVELOPMENT OF AN INSTRUMENTAL FRACTIONATION AND QUANTITATION SCHEME FOR SELECTED POLYNUCLEAR AROMATIC HYDROCARBONS PRESENT IN EXTRACTS FROM WOOD-PRESERVING WASTE

K. Washburn, H. Huebner, S. Safe, and K.C. Donnelly, Faculty of Toxicology, Texas A&M University, College Station, TX, 77843-4463

The polynuclear aromatic hydrocarbons (PNAs) are components of wood-preserving waste (WPW) which are known to contain multiple classes of organic and inorganic compounds. PNAs remain potent environmental contaminants because of their high carbon content and low vapor pressure which result in stability.

Identification and quantitation of individual PNAs and classes of PNAs is a preliminary step in a assessing risk and addressing potential remediation of WPW. Ag⁺ from AgNO₃ interacts with the conjugated P electrons of PNAs, allowing for a chromatographic separation based on differing degrees of conjugation. A high-volume, low-pressure (HVLP) chromatographic system with a 2-meter, high-bore AgNO₃/silica-packed column (in-house) and a Waters 600 HPLC system in tandem with a tunable (200-800 nm) photodiode-array detector (Waters 996) offers a comprehensive instrumental package capable of separating PNAs by degree of aromaticity and identifying and quantifying individual components.

The system described was used to separate and quantify 115 individual PNAs from a complex WPW-extract. Sub-fractions collected included 2-ring, 3-ring, 4-ring, and 5- and >5-ring. This data can later be used to determine potential interaction of PNAs by class and establish the contribution of each to the toxicity of the whole. The data generated will allow comprehensive risk assessment based on constituent PNAs. While the first separation was very tedious, later separations can be tailored to collect specific fractions of interest. This research is supported by NIEHS P42ESO4917.

Key words: polynuclear aromatic hydrocarbons, polycyclic aromatic hydrocarbons, separation, detection.

Oral presentation in analytical methods session.

92 • DEVELOPMENT OF AN IN SITU INSTRUMENTATION BUNDLE FOR MONITORING AIR INJECTION REMEDIATION TECHNOLOGIES

C.K. Baldwin, B.L. Hall, and R.R. Dupont, Utah Water Research Laboratory, Utah State University, Logan, UT, 84322-8200

The advent of the use of air injection remediation technologies such as air sparging and in-well aeration has highlighted a need for monitoring techniques which allow evaluation of remediation mechanisms in the subsurface. With this need in mind, an instrumentation bundle suitable for use in both the saturated and vadose zones was developed for monitoring subsurface conditions during air injection. The configuration and application of the bundle for real-time site monitoring during active remediation is described. The bundle provides information on dissolved oxygen and ground water displacement for use in defining the volume of influence of air injection systems. Also available is information on changes in hydrocarbon and oxygen concentrations and pressure gradients in the vadose zone. Laboratory testing protocols used for sensor evaluation are included along with results gathered during field testing of an in situ air sparging system

Key words: air sparging, monitoring, remediation, in-well aeration, dissolved oxygen.

Oral presentation in analytical methods session.

93 • ELECTROCHEMICAL SENSORS FOR REMOTE MONITORING OF INORGANIC AND ORGANIC CONTAMINANTS

J. Wang¹, N. Foster¹, P. Farias¹, J. Lu¹, D. Larson¹, and K. Olsen², ¹Department of Chemistry and Biochemistry, New Mexico State University, Las Cruces, NM, 88003, and ²Battelle PNL, Richland, WA, 99352

Submersible electrochemical sensors have been developed for remote monitoring of inorganic and organic pollutants. Such in situ operation offers rapid warning against sudden contamination and feedback during remediation activities. The new device is based on a novel 3-electrode housing and connected to a 50-ft long shielded cable (via environmentally-sealed connectors). Highly sensitive potentiometric stripping analysis is employed for the detection of trace metals, while amperometric biosensing at enzyme electrodes is used for monitoring phenolic and peroxide contaminants. Field demonstrations will be discussed, along with future prospects.

This work was supported by the U.S. DOE through the WERC program.

Key words: electrochemical sensors, remote monitoring, site characterization.

Oral presentation in analytical methods session.

94 • INFRARED PYROMETRY FOR WASTE CHARACTERIZATION

J.A. Macy, New Mexico State University, Department of Mechanical Engineering, Box 30001, Department 3450, Las Cruces, NM, 88003-0001

The research presented shows the development and application of two numerical methodologies for thermal waste characterization. A historical perspective of hazardous and nuclear waste production and storage in the Department of Energy complex is presented to provide motivation for thermal waste characterization. Specifically, the Hanford plutonium production plant with its underground storage tanks (USTs), containing hazardous and nuclear wastes, is examined. The objective of the research is the development of a methodology by which heat sources in the USTs can be remotely located and identified either for remediation purposes or for robotic path planning. The methodology is used in the broader context of the Multi-sensor Analysis Program for Environmental Restoration (MAPER) project developed at New Mexico State University by Dr. Edward Hensel. The MAPER analyses utilize data collected from many different sensors as well as historical site information to fully characterize a waste site in a hybrid fashion. A problem statement is established based upon the restrictions of UST robotic capabilities and basic infrared (IR) pyrometer operation. The two numerical methods are developed as ANSI C routines. One routine is designed to provide real-time information to the robot operator about the UST interior, while the other routine is designed to calculate an estimated temperature distribution using a weighted least-squares methodology after a data survey. The estimated temperature distribution provides a higher resolution image of the UST surface, as compared to the measured temperature distribution, so individual heat sources may be located. A mock UST designed by Sandia National Laboratories and New Mexico State University was built to provide a test bed for data collection. Many data surveys from the mock UST were collected using a robotic arm and sensor head assembly. Two of the data sets are graphically presented to show the positions of known heat sources and their thermal responses. The results of the two analyses on the data sets are graphically presented to illustrate the correlation between known heat sources and estimated thermal targets. Based upon the correlation between the targets and the known sources, it is easy to conclude that the IR analysis is capable of locating and presenting bounding boxes for thermal objects in a underground storage tank.

Key words: underground storage tank, infrared pyrometry, waste characterization.

Oral presentation in analytical methods session.

95 • ATOMIC FORCE MICROSCOPY (AFM) IMAGING OF DESTRUCTIVE ADSORBENT PARTICLE SURFACE MORPHOLOGY

I. Lagadic, S. Decker, T. Boronina, O. Koper, C. Mohs, and K.J. Klabunde, Chemistry Department, Kansas State University, Manhattan, KS, 66506

Atomic Force Microscopy (AFM) experiments were carried out on both metal oxide (CaO, MgO) and metal (zinc) particles used as destructive agents for chlorocarbons such as CCl₄. AFM provides information about the sample surface morphology and enables us to compare this surface morphology before and after reaction with CCl₄.

For both CaO and MgO, two types of metal oxide nanoparticles were observed: aerogel-prepared (AP) and conventionally-prepared (CP). The CP sample surface shows large particles (~40 nm) slightly elongated in shape while AP sample surface exhibits aggregates, varying in size from 60 to 100 nm, made up with small spherical particles (~20 nm). After exposure to a low CCl₄ pressure (10 torr) for 5 minutes at 450°C, the CP sample surface displays wide flat areas, which are presumed to be CaCl₂.2H₂O layers, while particles are still visible on AP sample surface allowing for further reaction. CaO and MgO reactivities were also compared for CP samples. The surface morphologies after CCl₄ decomposition suggest that the active sites involve the whole CP-CaO surface while they only involve the CP-MgO particle edges. Transition metal oxide-coated MO (M = Ca, Mg) nanoparticles were also investigated by AFM.

The AFM study of zinc particles shows a drastic surface morphology modification after reaction with CCl₄ in aqueous solution as the tube-like zinc particles seem to be "eroded." This investigation is still underway.

Key words: Atomic Force Microscopy (AFM), metal oxide, metal, chlorocarbon, decomposition, destructive adsorption.

Oral presentation in analytical methods session.

96 • USE OF X-RAY ABSORPTION NEAR-EDGE STRUCTURE TO DETECT BIOLOGICAL REDUCTION OF CHROMIUM(VI)

S.J. Rothenburger¹, R.R. Chianelli², M. Modrick³, M. Sansone¹, and B. DeVries¹, ¹Exxon Research and Engineering Co., Annadale, NJ, 08801, ²Chemistry Department, University of Texas at El Paso, El Paso, TX, 79968-5748, and ³Exxon Research and Engineering Co., Florham Park, NJ, 07932

Metals contamination in soil and wastewater is a current problem at refineries and other production sites. Bioremediation of metals using indigenous microorganisms offers an in situ, low cost alternative to ex situ treatment. We have identified a bacterium that chemically reduces hexavalent chromium to trivalent chromium under anaerobic conditions. The organism, a sulfate-reducing Desulfotomaculatum species, produces hydrogen sulfide which chemically reduces hexavalent chromium. This activity was confirmed by XANES analysis of untreated and microbially-treated soil containing 6,400 ppm total chromium as determined by IPS. The organism is tolerant of chromium concentrations of at least 6,400 ppm, and the XANES analysis clearly demonstrated the disappearance of any detectable hexavalent chromium from the soil matrix in less than 120 days.

Key words: biological reduction, chromium(VI), XANES.

Oral presentation in analytical methods session.

97 • USE OF TRACERS FOR THE CHARACTERIZATION OF SCALE-DEPENDENT SUBSURFACE PROPERTIES: INITIAL EVALUATION

G.R. Barth, T.H. Illangasekare, and H. Rajaram, Department of Civil, Environmental, and Architectural Engineering, University of Colorado at Boulder, Boulder, CO, 80309-0428

A great deal of the work done towards the development of effective parameters has focused on analysis techniques for adapting parameters determined from a small-scale to a field-scale system. These techniques suffer from the inherent limitations of developing conclusions about regional or grid-scale flow based on a limited number of smaller-scale, isolated measurements. A conservative tracer injected into heterogeneous media will, however, be affected by all the heterogeneities encountered in the existing flow-fields between the site of injection and extraction. Instead of attempting to develop a stochastic method of applying small-scale results, a tracer test provides a direct measurement of the heterogeneous system. Tracers have potential as a method of evaluating aquifer characteristics on the same scale at which modeling parameters are required. A series of tracer tests were performed to assess the ability of tracers to function as a tool for determining effective field scale parameters. The main objective for this initial stage was the development of quantitative methods to interpret breakthrough curves. For the first step, repeatability and sensitivity to modifications in the flow-field were evaluated. The tests were performed in a large, two-dimensional tank with a heterogeneous packing. The flow-field was modified by macroscale entrapment of an LNAPL. Additional tests were performed in the large tank with a variety of heterogeneous packing before and after entrapment of contaminants. At the same time a number of small scale tests were performed to obtain a direct comparison between the results of the tracer test and other methods of determining effective parameters.

Key words: effective parameters, tracers, scaling.

Oral presentation in analytical methods session.

Program Four Wednesday, May 22, 1996 Bioremediation · Santa Fe Room

98 • FACTORS INFLUENCING THE MICROBIAL METABOLISM OF PAH IN SOILS

L.M. Carmichael¹ and F.K. Pfaender², ¹Ciba-Geigy Corporation, 410 Swing Road, P.O. Box 18300, Greensboro, NC, 27419-8300, and ²The University of North Carolina at Chapel Hill, CB#7400, Chapel Hill, NC, 27599-7400

Bioremediation is a feasible technology for removing polycyclic aromatic hydrocarbons (PAH) from soils, but the low water solubilities of PAH and their tendency to associate with organic matter may limit their metabolism by microorganisms. This project investigated the microbial metabolism of several [¹⁴C]-PAH (phenanthrene, pyrene, benz(a)anthracene, chrysene, and benzo(a)pyrene) in five soils with differing physical characteristics and differing previous exposure histories to PAH. The primary biotic fate of [¹⁴C]-PAH was mineralization; production of non-mineral metabolites and incorporation of [¹⁴C]-PAH into cellular biomass were minimal (together accounting for 7 to 10% of the added [¹⁴C]-PAH). All [¹⁴C]-PAH, with the exception of [¹⁴C]-benzo(a)pyrene, were readily mineralized in the contaminated soils (9 to 60% of the added [¹⁴C]-PAH). The remaining [¹⁴C]-PAH was associated with the soils, most of which was ethyl acetate-extractable. The fraction of [¹⁴C]-PAH that was mineralized, ethyl acetate-extractable from the soil or remaining in the soil after extraction, was usually not related to most characteristics of PAH (solubility and octanol water partition coefficient) soils (fraction of organic carbon and the extent of native PAH contamination) or estimates of microbial biomass (general heterotrophic microorganisms and PAH-degrading microorganisms). The fate of [¹⁴C]-PAH was, however, consistently related to the fraction of silt and clay in the soils. Soils with larger fractions of silt and clay tended to have lower extents of mineralization, lower overall recovery efficiencies, a smaller fraction of [¹⁴C]-PAH that was ethyl acetate-extractable from the soil, and a larger fraction of [¹⁴C]-PAH remaining in the soil after extraction than those soils with a smaller fraction of silt and clay. This suggests that interaction of PAH with small soil particles may limit their metabolism by microorganisms.

Key words: polycyclic aromatic hydrocarbons, bioremediation, bioavailability.

Oral presentation in bioremediation session.

99 • AQUEOUS SYSTEM REMEDIATION OF ORGANOHALIDE POLLUTANTS BY THE UTILIZATION OF AQUATIC ORGANISMS

V.P. Hershberger, Groundwater Technology, Inc., 2501 Yale Boulevard, S.E., Suite #204, Albuquerque, NM, 87106

Wildlife toxicological research substantially documents the bioaccumulation of organohalide pollutants in aquatic organism tissues. Bioaccumulation levels of organohalide pollutants such as PCBs and DDTr in fish tissues, for example, may range from thousands to millions of times greater than those levels which exist in the ambient aquatic environment. Given this pollutant-concentrating phenomenon, the author proposes the use of fish and other aquatic organisms to filter, concentrate, and remove bioaccumulable contaminants from polluted aqueous systems. Harnessing bioaccumulation for the removal of bioaccumulable contaminants involves the harvesting and subsequent restocking of hardy macroscopic aquatic organisms which bioaccumulate high contaminant levels in relatively short periods of time. Studies document that contaminant-resistant fish adapted to organohalide polluted environments can function in more highly polluted environments and also bioaccumulate higher contaminant concentrations in tissues than identical unadapted species.

Recent environmental microbiological literature documents successes in the microbial mediated destruction of the otherwise recalcitrant organohalide pollutants such as PCBs and DDTr. Given these research breakthroughs, the author is proposing and testing the hypothesis that the biodegradation of recalcitrant organohalide contaminants could be further facilitated if concentrated in fish or other aquatic organism tissues. Nitrogen, phosphorous, potassium, amino acids, lipids, and other microbial growth factors occur in abundance in fish tissues, thus enhancing the bioavailability of the pollutants to the degrading microbes. Therefore, the bioaccumulator organisms used to remove organohalide contaminants from a polluted aqueous system could then be composted with specialized microbes to destroy those normally recalcitrant contaminants.

This research develops possible low-energy applications, including primary or secondary treatment of extracted ground water, wastewater treatment augmentation, supplemental wetlands treatment, and natural aquatic environments restoration.

Key words: ecological engineering, bioremediation, aquaculture, bioaccumulation.

Oral presentation in bioremediation session.

100 • BIOREMEDIATION ENHANCEMENT BY PHYSICOCHEMICAL PRETREATMENT

M. Moo-Young, W.A. Anderson, J.M. Scharer, I. van Kamenade, and M. Mehrvar, Department of Chemical Engineering, University of Waterloo, Waterloo, Ontario, Canada N2L3G1

Substantial reduction in overall processing time can be realized by integrated physicochemical pretreatment of xenobiotic contaminants with subsequent biological mineralization of the resulting intermediates. In case studies, it is found that chemical preoxidation of phenanthrene with peroxymonosulfate (Oxone), and photocatalytic preoxidation of tetrahydrofuran, dioxane, chlorobenzoic acid, and phenol, may significantly overcome the technoeconomic limitations of stand-alone bioremediation strategies.

Key words: bioremediation, xenobiotics, pre-oxidation.

Oral presentation in bioremediation session.

101 • EVALUATION OF SULFUR-BASED AUTOTROPHIC DENITRIFICATION

D.G. Lampe and T.C. Zhang, Department of Civil Engineering, University of Nebraska-Lincoln at Omaha Campus, Omaha, NE, 68182-0178

Nitrate contamination of ground and surface waters has become an increasingly serious problem in the U.S. This research project is mainly concerned with evaluation of sulfur-based autotrophic denitrification processes (SBADP), which employ Thiobacillus denitrificans to reduce nitrate to nitrogen gas using elemental sulfur as the electron donor, carbon dioxide as carbon source for growth, and nitrate as the electron acceptor.

The objectives of this study are: (1) to test and evaluate the SBADP for above-ground treatment of nitrate-contaminated water using lab-scale upflow anaerobic fixed-bed reactors; and (2) to conduct kinetic studies on in situ remediation of nitrate-contaminated ground water with the SBADP using anaerobic batch reactors.

A 3.4 liter continuously-stirred tank reactor (CSTR) with gas collection utilizes thiosulfate as the electron donor and has served as a seed source for the batch reactors and fixed-bed reactors. Four upflow anaerobic fixed-bed reactors are constructed from 2.5 in. I. D. acrylic column. The empty bed reactor volume is 1.53 liters and the granular sulfur and limestone media working volume is 1.11 liters.

Start-up of the column reactors began with a series of inoculations from the CSTR mixed liquor; quasi-steady-state conditions were achieved after four weeks. Under quasi-steady-state conditions, the influent concentrations were 33 mg NO₃^--N/1, the loading rate was 75 mg NO₃^--N/1/d, and the average HRT was 16.75 hours. Four columns with sulfur:limestone ratios of 1:3, 1:1, 3:1, and sulfur only, revealed nitrate reductions of 76%, 97%, 99%, and 52%, respectively. The HRT of column reactors will be shortened to be 8, 2, and 0.5 hrs., and the performance will be further evaluated.

Soil-elemental sulfur anaerobic batch tests are designed to generate information on kinetics of in situ remediation of nitrate-contaminated ground water using the SBADP. The experimental results obtained from the CSTR and batch reactors demonstrated that sulfate concentration, nitrite, pH, and DO concentrations in the reactors are key parameters affecting the performance of the CSTR or batch reactors. SO₄^2- is produced and pH decreases during the denitrification process. The denitrification will be seriously inhibited at high concentration of sulfate (> 5,000 mg/l) and low pH (about 5.6 to 6.0).

Preliminary results for sulfur-based autotrophic denitrification have been promising. Further research will provide a clearer picture of performance in the existing bench-scale systems. Long term goals include application of this technology to pilot-scale systems in the quest for feasible denitrification alternatives.

Key words: nitrate, autotrophic denitrification, ground water, bioremediation, sulfur.

Oral presentation in bioremediation session.

102 • TREATMENT OF TRICHLOROETHENE (TCE) WITH A FLUIDIZED-BED BIOREACTOR

R.L . Segar, Jr., and S.A. Vivek, Department of Civil Engineering. University of Missouri-Columbia, Columbia, MO, 65211

Many types of bench-scale bioreactors have met limited success with the treatment of trichloroethene (TCE) contaminated water. This research project used a fluidized-bed biofilm reactor (FBBR) to obtain cometabolism of TCE by microorganisms grown on phenol. The intended application of the reactor is primarily for treatment of ground water extracted during aquifer remediation.

The FBBR provided a high level of microbial activity and avoided the plugging problems associated with packed-bed reactors. Experiments were conducted to determine the removal of TCE for various phenol loading rates and pulsed-feeding techniques. High levels of phenol feeding inhibited TCE degradation, and phenol was not completely removed. Low levels of phenol feeding did not sustain TCE removal over time. A phenol to TCE mass ratio of 50:1 provided 70-80% removal of 0.1 mg/l TCE at an EBCT of 3 minutes. Phenol was not detected in the reactor effluent at those conditions. The kinetic performance was extraordinary compared to earlier bioreactor studies and the process holds promise as an alternative to air-stripping and granular activated carbon. Higher removals of TCE could be obtained with the FBBR in field conditions where the reactor height may be extended.

Key words: biofilm, fluidized-bed, trichloroethene, phenol, ground water remediation.

Oral presentation in bioremediation session.

103 • ANAEROBIC BIODEGRADATION OF TOLUENE IN A PLUG-FLOW DIGESTER

T. Liu, K. Fukushi, and S. Ghosh, Department of Civil and Environmental Engineering, The University of Utah, Salt Lake City, UT, 84112

Toluene is an important organic constituent of gasoline; it is widely used for the synthesis of industrial chemicals and pesticides. However, toluene and its oxidation products are carcinogenic and neurotoxic; it is also classified as a priority pollutant by the United States Environmental Protection Agency. Due to inadequate treatment techniques and/or indiscriminate disposal on the land, and surface and ground waters, toluene is causing serious pollution problems in many places, including the U.S.-Mexican border area. Leakage from underground storage tanks and pipelines, accidental spills, and leaching landfills are the major resources of toluene entering streams, soil, sediments, and ground water.

This paper presents the application of a continuous-flow, mesophilic 35ºC anaerobic plugflow digester for cometabolic degradation of toluene by an anaerobic microbial consortium with conventional liquid and solid pollutants serving as the major carbon sources. The results of this research showed that sequential acidogenic and methanogenic fermentation occurring in the plugflow reactor can stabilize and detoxify mixed conventional and hazardous, liquid and solid wastes with simultaneous production of a methane-rich (79%) fuel gas. The plug-flow digester removed 95% of the toluene in the liquid phase with a simultaneous total COD reduction of 96% at an hydraulic retention time (HRT) of approximately 13 days and an organic loading rate of 0.81 kg COD/m³-day. The concentration of toluene in the effluent was 2 mg/l compared with an influent concentration of 50 mg/l. The amount of toluene released to the confined gas phase was about 2.6% of the toluene loading to the digester. The gas phase toluene is readily oxidized to CO₂ and water during combustion of this fuel gas. The plug-flow digester showed good performance in terms of removal efficiency and degradation rate of toluene and conventional organic substrates.

A kinetic model derived from the Monod equation was utilized to describe cometabolic toluene degradation. A model applicable to intermediate concentrations of toluene was used to fit toluene degradation profiles in the plug-flow digester. It was assumed that cometabolism of toluene did not support cell growth. The kinetic parameters of half-velocity constant (K_s) and the maximum rate of toluene utilization (C) were estimated by applying a nonlinear regression to steady-state toluene concentration profiles. Values of K_s and C were 12.2 mg/l and 6.2 mg/l-day, respectively. This model enabled quantitative prediction of toluene degradation in an anaerobic plug-flow reactor. The plug-flow digester continuously charged with cometabolic substrates with a COD of 11,000 mg/l exhibited better performance than that of other systems.

Key words: biodegradation, cometabolism, toluene, plug-flow.

Oral presentation in bioremediation session.

104 • RELATIONSHIP BETWEEN AEROBIC BIODEGRADATION RATES, CHEMICAL STRUCTURE, AND SOIL TYPE FOR SELECTED PETROLEUM HYDROCARBONS

W.J. Doucette¹, J. Yuan¹, B. Bugbee², A. Ravipaty¹, and R.R. Dupont¹, ¹Utah Water Research Laboratory and ²Crop Physiology Laboratory, Utah State University, Logan, UT, 84322

Despite its importance in environmental fate assessments, quantitative information describing the biodegradation of individual petroleum hydrocarbons in soils is often lacking. In addition, biodegradation rates reported for specific chemicals often vary dramatically from one study to another. In many cases it's difficult to determine if the differences are due to variables associated with soil type, such as moisture, nutrients, and oxygen level, or to differences in the technique used to measure biodegradation. Biodegradation rates are typically determined by directly measuring the disappearance of the chemical of interest over time or indirectly by measuring evolved CO₂ or O₂ consumption. Indirect respirometric methods are generally simpler, quicker, and cheaper than direct methods and are often used to quantify biodegradation at field sites. We measured aerobic biodegradation rates for 16 individual aliphatic and aromatic petroleum hydrocarbons in four soils using respirometry. The biodegradation of petroleum fuel mixtures was also examined using the same technique. The relationships between biodegradation rates, chemical structure, and soil type will be described.

Key words: alkanes, aromatics, microcosm, respirometry.

Oral presentation in bioremediation session.

105 • INFLUENCE OF MOISTURE CONTENT ON BIOREMEDIATION OF ORGANIC CONTAMINANTS IN THE SUBSOIL

B. Liu¹, M.K. Banks¹, A.P. Schwab², and L. Schuckman¹, ¹Department of Civil Engineering and ²Department of Agronomy, Kansas State University, Manhattan, KS, 66506

Hazardous organic chemicals, especially petroleum hydrocarbons, are major contaminants of soil and ground water. Bioremediation of organic contaminants has been studied with great interest recently by environmental scientists. However, uncertainties remain concerning its effectiveness for certain compounds, including petroleum hydrocarbons, and factors influencing the rate and extent of degradation in certain environments. One of the most important factors affecting bioremediation is moisture content. Optimal moisture content for microorganisms in the soil may accelerate degradation significantly. In this research, jet fuel was used as the contaminant. Clay soil was collected at 1 meter depth from the North Agronomy Farm, Manhattan, KS. Biodegradation of jet fuel in the clay soil with five different moisture contents was investigated at 25°C and 4ºC. Microorganisms in the contaminated soil were counted using plate counts. The range of optimal moisture contents was estimated based on literature values. Moisture contents from 18% (g water/g wet soil) to 25% (g water/g wet soil) showed relatively high degradation rates. Degradation rates at room temperature and 4°C were compared. The five chemicals in the mixture were also identified, and p-xylene and decane were degraded most readily.

Key words: bioremediation, petroleum hydrocarbons, microorganisms, subsoil, degradation.

Oral presentation in bioremediation session.

106 • BIOREMEDIATION BACTERIA TO PROTECT PLANTS FROM PENTACHLOROPHENOL TOXICITY IN SOIL

W.F. Pfender, Plant Pathology Department, Kansas State University, Manhattan, KS, 66506-5502

Growth of plants in contaminated surface soils can be beneficial in remediating polluted sites, by plant and/or associated microbial metabolism of pollutants, and by stabilization of polluted soil against erosion. However, phytotoxicity and plant bioconcentration of some pollutants can interfere with successful vegetative site restoration. We found that Pseudomonas strain SR3, when applied to seeds of proso millet (Panicum miliaceum L.), protected the growing plants from phytotoxicity of pentachlorophenol (PCP) in the soil during a 4-week growth-chamber study. Untreated plants in the contaminated soil grew very poorly, whereas in soil receiving the bacteria-treated seed, plants grew well and PCP was reduced from 175 ppm to 3 ppm. When bacteria were mixed thoroughly into the soil at 5 X 10⁶ cfu/g, in the absence of plants, PCP was likewise reduced from 175 to 5 ppm. PCP in soil with non-inoculated plants remained approximately at the initial level (165 ppm extractable PCP). Roots without applied bacteria concentrated PCP from the soil into root tissue to a ratio of 13:1 (final root concentration: initial soil concentration, both in ppm by weight), whereas the bacteria-treated roots concentrated PCP at a ratio of 0.09:1.

Key words: pentachlorophenol, vegetative remediation, plants, bioremediation, soil, bacteria.

Oral presentation in bioremediation session.

Bioremediation and Volatile Compounds · Santa Fe Room

107 • DESIGN OF CLOSED CHAMBERS FOR MEASURING PHYTOREMEDIATION: OPTIMIZING PLANT GROWTH AND CHEMICAL MASS BALANCE

B. Bugbee¹ and W.J. Doucette², ¹Crop Physiology Laboratory and ²Utah Water Research Laboratory, Utah State University, Logan, UT, 84322

The potential value of phytoremediation has been demonstrated in both laboratory and field settings, but rigorously quantifying its effectiveness has been difficult, especially for volatile organic chemicals. Sealed growth chambers are necessary to quantitatively determine the fate of volatile organics in plant/soil systems. However, chamber design is often a compromise between optimum plant growth and chemical mass balance. Low humidities are necessary to promote normal transpiration rates in sealed chambers, but procedures for obtaining low humidity increase the difficulty of recovering volatile organic compounds. Vigorous plant growth is closely associated with large fluxes of water vapor in transpiration This water vapor can be condensed and removed from the chamber, but rapid air flow rates through the chamber are necessary to prevent the unnatural accumulation of volatile organic compounds in the chamber air. High flow rates mean that large, efficient traps are necessary to recover volatiles form the air stream. Large soil containers are also necessary to simulate the root-zone oxygen and water conditions in the field. Unfortunately, increased soil volume increases the difficulty in obtaining a good mass balance in the soil compartment. Cost-effective options for simulating the field environment, optimizing plant growth. and obtaining mass balance of volatile organic compounds will be discussed.

Key words: humidity, transpiration rates, volatile organic compounds, root-zone oxygen.

Oral presentation in bioremediation and volatile compounds session.

108 • EXPERIMENTAL AND MODELING STUDIES OF THE FATE OF TRICHLOROETHYLENE IN A CHAMBER IN THE PRESENCE OF ALFALFA PLANTS

N. Muralidharan¹, N.K. Russell², L.C. Davis³, and L.E. Erickson¹, Departments of ¹Chemical Engineering, ²Chemistry, and ³Biochemistry, Kansas State University, Manhattan, KS, 66506

Experiments were performed in a laboratory chamber to investigate the influence of alfalfa plants on the fate of trichloroethylene (TCE) which is being fed at a concentration of 200 ml/l in the entering ground water. The dimensions of the chamber are 180 cm in axial length, 35 cm in depth, and 10 cm in width. Concentrations of TCE in the aqueous phase were measured using gas chromatographic headspace analysis technique. FT-IR instrumentation was employed to monitor the evapotranspirational fluxes of TCE from the soil to the headspace of the chamber. Modeling the fate of TCE in this chamber was also attempted simultaneously. Models assuming non-equilibrium partitioning between gas, water, and solid phases were compared to equilibrium based models. Non-equilibrium transport was modeled as a diffusional mass transfer resistance across a film separating the corresponding phases. The boundary condition at the surface was modified to account for free gas phase diffusion of the volatile TCE contaminant to the headspace of the chamber. The simulation results are being compared with experimental data on the fate of TCE.

Key words: volatile organics, headspace, non-equilibrium phenomenon, mass transfer.

Oral presentation in bioremediation and volatile compounds session.

109 • THE EFFECT OF SOIL WETTING AND DRYING PROCESSES ON THE TRANSPORT BEHAVIOR OF VOLATILE ORGANIC COMPOUNDS IN UNSATURATED POROUS MEDIA

I.Y. Padilla, M.H. Conklin, and T.C.-J. Yeh, Department of Hydrology and Water Resources, University of Arizona, Tucson, AZ, 85721

Many organic contaminants present in subsurface environments are volatile and slightly soluble in water. Transport of these vapors and solutes through the vadose zone may result in long-term contamination of ground water resources and human exposure to these chemicals through contact, inhalation, and/or oral consumption. The transport behavior of volatile organic compounds (VOCs) in unsaturated porous media has been investigated at different water contents. More specifically, this study has identified the effects of wetting and drying (hysteretic) processes on dispersive and mass transfer transport mechanisms. Transport experiments were conducted by passing a finite pulse of non-reactive chemicals and trichloroethylene (TCE) through a column packed with silica sand under different water contents and wetting and drying conditions. Chemical concentrations at the outlet of the column were monitored and the breakthrough data was simulated using a numerical transport model. Mass transfer coefficients for TCE and dispersivity values for a silica sand have been determined for each of the experimental conditions imposed.

This work enhances our understanding of VOCs transport in subsurface environments and improves our ability to predict the fate and transport of organic contaminants under variable water-saturated conditions. Ultimately, this research will improve our ability to assess and select effective clean-up strategies for many hazardous waste sites and minimize exposure of these pollutant to humans and ecosystems.

Key words: transport, unsaturated, volatile organic compounds, hysteresis, vadose.

Oral presentation in bioremediation and volatile compounds session.

110 • COMPARISON OF FIELD AND LABORATORY METHODS FOR VOCS AND MAJOR GASES IN SOIL VAPOR

J.R. Forbes, R. Schmidt-Petersen, B. Casadevall, and D. Reaber, Daniel B. Stephens & Associates, Inc., 6020 Academy N.E., Albuquerque, NM, 87109, e-mail: dbstephens@rt66.com

Soil gas sampling and analysis have become increasingly important during environmental site investigations. In addition to the well-known use of shallow soil vapor surveys to locate potential contaminant source areas, variations in the composition of soil gas samples collected from deeper depths can often provide important clues regarding the nature and extent of volatile subsurface contaminants. Deep soil gas data are particularly helpful in understanding the vadose zone hydrologic process underlying sites where organic compounds have been released or buried, such as liquid hydrocarbon spill sites and landfills. We have installed several dozen permanent multi-port soil gas (MPSG) monitor wells of unique design at sites in Arizona and New Mexico to characterize the distribution of volatile organic compounds (VOCs) and major gases in soil vapor with depth. Each MPSG well is installed within a single borehole and allows soil gas samples to be drawn from multiple discrete depth intervals in the vadose zone. If desired, the MPSG well can be coupled with a standard ground water monitor well to permit sampling of the underlying ground water. This allows for direct comparison of ground-water quality with that of the overlying soil vapor.

Soil gas samples collected in evacuated stainless-steel SUMMA^R canisters were submitted to the laboratory for VOC analysis by GC/MS using EPA Method TO-14. In addition, the concentrations of major gases (carbon dioxide, oxygen, methane, nitrogen, and hydrogen) were determined in the laboratory by gas chromatography/thermal conductivity detection (GC/TCD). The difficulty and expense of obtaining reliable laboratory data for soil gas samples led us to explore the possibility of determining soil gas concentrations in the field using portable instruments. A Landtec GA-90 multi-gas monitor was used to determine the concentrations of CO₂, CH₄, and O₂. In general, the field and laboratory results compared very well when the GA-90 instrument was calibrated frequently using calibration gases that span the concentration range of interest. The presence of high concentrations (>100 ppmv) of fuel hydrocarbons in some soil vapor samples was found to interfere with the methane detector, however, causing erroneously high methane readings.

A Brùel & Kjær Model 1302 photo-acoustic multi-gas monitor was used to determine the soil gas concentrations of trichloroethene (TCE) and tetrachloroethene (PCE) in the field. These results were compared with VOC concentrations determined in the laboratory using Method TO-14. TCE concentrations in soil gas ranged from the sub-ppm level to the volume percent level, a range of over 5 orders of magnitude. For TCE at concentrations above about 1 ppmv, the two data sets compared remarkably well, with an R² value of about 0.9. The correlation for PCE was not as good. The results of this study indicate that high quality soil gas data can be obtained using existing field instruments in less time and at far lower cost than the equivalent laboratory analyses, provided that the primary VOCs in the soil vapor are known from previous analyses.

Key words: soil gas, trichloroethene, landfill, vadose.

Oral presentation in bioremediation and volatile compounds session.

Program Four Thursday, May 23, 1996 Phytoremediation · Santa Fe Room

111 • PHYTOREMEDIATION AT HAZARDOUS WASTE SITES

J. Burken, A. Dietz, J. Jordahl, W. Schnabel, P. Thompson, L.A. Licht, P.J.J. Alvarez, and J.L. Schnoor¹, Department of Civil and Environmental Research, 116 Engineering Research Facility, The University of Iowa. Iowa City, IA, 52242, ¹e-mail: jschnoor@cgrer.uiowa.edu

Phytoremediation is the use of vegetation for in situ treatment of hazardous wastes. It is a form of ecological engineering that has proven effective and relatively inexpensive at several pilot- and full-scale sites. Plants have shown the ability to withstand greater concentrations of organic pollutants than most microorganisms, and they can take up chemicals quickly and convert them to less toxic metabolites. In addition, they stimulate the degradation of organic chemicals in the rhizosphere by the release of root exudates, enzymes, and the build-up of organic carbon in the soil. In this summary paper, recent research results will be presented on pilot- and full-scale applications using hybrid poplar trees at hazardous waste sites for atrazine, 2,4,6-trinitrotoluene (TNT), trichloroethylene (TCE), and BTEX compounds (benzene, toluene, ethylbenzene, and xylenes). Key findings include the importance of direct plant uptake for organics with intermediate octanol-water partition coefficients (log K_ow = 1.0-3.5), the metabolism of some organics in leaf and stem tissue, the release of VOCs through leaf tissue to the atmosphere, and the creation of "bound-residue" in the plant based on ¹⁴C-label studies.

Key words: phytoremediation, hazardous waste, bioremediation, contaminated soil, ground water.

Oral presentation in phytoremediation session.

112 • REMEDIATION OF PESTICIDE WASTES USING RHIZOSPHERE MICROORGANISMS

T.A. Anderson, E.L. Kruger, and J.R. Coats, Pesticide Toxicology Laboratory, Iowa State University, Ames, IA, 50011-3140

Many agrochemical dealerships have experienced soil and water contamination problems from normal operating procedures and accidents during the last 40 years. In most instances, the costs associated with current cleanup technologies preclude their use at these facilities. However, phytoremediation may provide a more economical approach if vegetation can survive on these sites and encourage microbial proliferation and degradation.

We have demonstrated that the degradation of atrazine, metolachlor, and trifluralin was significantly greater in rhizosphere soils from Kochia scoparia than in nonvegetated soils. In addition, mineralization of ¹⁴C-atrazine in a mixture of atrazine and metolachlor (50 µg/g each) was significantly greater in Kochia scoparia rhizosphere soils than nonvegetated soils. In both studies, soils were collected from retail agrochemical dealer sites.

We have also screened rhizosphere soils from several other plant species for their ability to mineralize atrazine or metolachlor at concentrations typical of point-source contamination (50 mg/g). In addition, we have tested the germination and survivability of various plants in contaminated soil. Both of these tests are attempts to find plants more amenable for use in phytoremediation.

Key words: rhizosphere, phytoremediation, atrazine, vegetation, degradation.

Oral presentation in phytoremediation session.

113 • VARIATION IN ROOT GROWTH AMONG FOUR SORGHUM VARIETIES GROWN IN SOIL CONTAMINATED WITH PETROLEUM HYDROCARBONS

P.A. Kulakow¹, Z. Chen², K. Rathbone¹, A.P. Schwab¹, M.K. Banks², and P.J. Bramel-Cox¹, Departments of ¹Agronomy and ²Civil Engineering, Kansas State University, Manhattan, KS, 66506-5501

Variation among genotypes in root growth may contribute to variation in the ability of plants to enhance degradation of petroleum hydrocarbons, a process called phytoremediation. Four varieties of grain sorghum, Sorghum bicolor (L.) Moench, were compared in a greenhouse experiment using three soils: uncontaminated soil, soil contaminated with 0.25% crude oil, and soil contaminated with 0.25% synthetic diesel. Root length density and root surface area were estimated at the fifth leaf and boot growth stages. Variation in root parameters among the varieties was determined for each soil type and compared with the degradation of soil contaminants. Understanding of the role of root growth in enhancing the degradation of petroleum hydrocarbons will aid in selection of species and varieties for use in phytoremediation.

Key words: phytoremediation, root growth, petroleum hydrocarbons, sorghum, genetic variation.

Oral presentation in phytoremediation session.

114 • DETECTION OF AGRONOMIC AND BIOREMEDIATION VARIABILITIES BETWEEN ALFALFA CLONES GROWN IN CRUDE-OIL CONTAMINATED SOILS

Z. Chen¹, A.P. Schwab², M.K. Banks¹, C.C. Wiltse³, and W.L. Rooney³, Departments of ¹Civil Engineering and ²Agronomy, Kansas State University, Manhattan, KS, 66506, and ³Department of Soil and Crop Science Texas A&M University, College Station, TX, 77843

Phytoremediation may be an economical way to remediate crude-oil contaminated soils. Studies indicate that alfalfa (Medicago sativa, L.) is effective at enhancing degradation of organic chemicals in soils (Schwab and Banks, 1994). Due to the highly heterozygous nature of alfalfa, it is likely that variability exists between cultivars, or plants within a cultivar, for agronomic performance in contaminated soil. If variability does exist, it should be possible to improve plant performance for agronomic and phytoremediation characteristics. The objectives of the study were: (1) to determine if variability exists between alfalfa genotypes for agronomic performance in crude-oil contaminated soil, (2) to compare the performance of clonally-replicated genotypes in uncontaminated versus crude-oil contaminated soil, and (3) to assess the bioremediation potential of alfalfa genotypes. Twenty cloned genotypes from the alfalfa cultivar 'Riley' were transplanted into 2% (w/w) crude-oil contaminated soil. A number of agronomic parameters were measured throughout the experiment, including forage yield, plant height, and maturity. After one year, differences existed between genotypes for total forage yield (P<0.05), maturity at harvest (P<0.001), and plant height (P<0.01). Eight of the 20 genotypes were also grown in uncontaminated soil. After one year, the forage yield in contaminated soil was 32% of the same clones grown in uncontaminated soil. Clones grown in contaminated soil were less mature and shorter than when they were grown in uncontaminated soil. While overall agronomic performance is reduced in contaminated soil, enough variability exists between genotypes to develop alfalfa populations adapted for growth in contaminated soil. In addition, differences in bioremediation efficiency of these cloned genotypes may exist and may be enhanced after a period of time.

Key words: phytoremediation, alfalfa genotype, agronomic performance.

Oral presentation in phytoremediation session.

115 • USE OF BIOMARKERS TO ASSESS PHYTOREMEDIATION OF PETROLEUM-CONTAMINATED SOILS

E.X. Wang, M.K. Banks, and A.P. Schwab, Departments of Agronomy and Civil Engineering, Kansas State University, Manhattan, KS, 66506-5501

Accurately quantifying biodegradation losses in the field are often complicated by spatial variability, dilution, leaching, and volatilization. To better evaluate biodegradation rates, compositional changes of hydrocarbons are monitored through column chromatography to determine class distributions. The relative distribution of saturates, aromatics, and polar compounds change as biodegradation progresses. Target compounds (e.g., hopane, methyldibenzothiophenes, and methylchrysenes) in saturate and aromatic fractions are determined by GC/FID and GC/MS. As biomarkers or "fingerprints," these compounds are present in contaminated soils at relatively high concentrations and are subject to little interference from evaporative weathering. Therefore, they are distinctively used to indicate the occurrence of microbial degradation of oils. Contaminated soil samples from different soil types, plant treatments, and biodegradation stages are measured over periods of phytoremediation.

Key words: class distribution, dibenzothiophenes, chrysenes, hopane, biodegradation, GC/MS.

Oral presentation in phytoremediation session.

116 • PHYTOREMEDIATION OF PETROLEUM CONTAMINATED SOIL-A FIELD ASSESSMENT

M.K. Banks¹, A.P. Schwab², and R.S. Govindaraju¹, ¹Department of Civil Engineering and ²Department of Agronomy, Kansas State University, Manhattan, KS, 66506

Greenhouse studies have indicated that vegetative remediation is a feasible method for clean-up of surface soil contaminated with petroleum products. However, field demonstrations are important to exhibit this new technology to the industrial community. In this project, several petroleum-contaminated field sites have been chosen in collaboration with three industrial partners. These sites have been thoroughly characterized for chemical properties, physical properties, and initial contaminant concentrations. A variety of plant species have been established on the sites, including warm and cool season grasses and legumes. Soil analyses for the target compounds over time indicate that the interaction between plants and rhizosphere microflora significantly enhances remediation of the contaminated soils. Continued monitoring will allow us to assess the efficiency and applicability of this remediation approach.

Key words: bioremediation, phytoremediation, plants, contaminant, soil, ground water.

Oral presentation in phytoremediation session.

Posters · Taos, Las Cruces, and Yucatan Rooms and Pre-Convention Area

1 • INNOVATIVE TECHNOLOGIES FOR THE REMEDIATION OF SOIL AND GROUND WATER FROM THE DEPARTMENT OF ENERGY, OFFICE OF TECHNOLOGY SYSTEMS

V.M. Ceci¹ and S.P. Mathur², ¹BDM Federal, Suite 400, 555 Quince Orchard Road, Gaithersburg, MD, 20878, and ²U.S. Department of Energy, Office of Technology Systems, Cloverleaf Building, 19901 Germantown Road, Germantown, MD, 20874

For over fifty years, the Department of Energy (DOE) or its predecessor agencies have designed, manufactured, and tested nuclear weapons for national defense. Production, testing, and decommissioning of these weapons has resulted in the contamination of vast tracts of property. Today, DOE is responsible for waste management and remediation of more than 100 contaminated installations in 36 states and territories. This includes 3,700 sites occupying 26,000 acres, with hazardous- or radioactive-contaminated surface and ground water, soil, or structures requiring remediation. This number continues to grow as new sites are defined. There are approximately 500 surplus facilities awaiting decontamination and decommissioning and approximately 5,000 peripheral properties (business and residences) that have soil contaminated with uranium tailings.

As a result of past disposal practices, numerous DOE facilities exhibit contaminant plumes emanating from waste disposal areas. It is currently estimated that over 600 billion gallons of ground water contaminated with radioactive and/or hazardous wastes exist within the DOE complex. Heavy metals, radionuclides, volatile organic compounds (VOCs), and DNAPLs (dense nonaqueous phase liquids) are estimated to contaminate over 200 million cubic yards of soil. In addition, over 25 contaminant plumes extend off DOE sites, and two major drinking water aquifers are threatened (Ogallala with volatile organic compounds, and Miami Aquifer with uranium). Current technologies are costly and often ineffective for the characterization (especially for DNAPLs) and cleanup of soils and ground water, or to prevent further migration.

The immediate challenge, therefore, is to develop a cost-effective, environmentally-sound approach to cleaning up these contaminated soils and waters. The approach should significantly reduce the volume of contaminated material that requires special handling, packaging, and costly disposal, or if possible, remediate the site in situ.

To that end, five major remediation and waste management problem areas within the DOE complex have been targeted for action on the basis of risk, prevalence, or need for technology development to meet environmental requirements and regulations. Termed "Focus Areas," the Office of Environmental Management (EM), Office of Science and Technology (OST) has initiated the Landfill Stabilization Focus Area (LSFA) and the Contaminant Plumes Containment and Remediation Focus Area (PFA) for the development and deployment of safer, more cost-effective and efficient technologies which satisfy DOE site needs. These focus areas are structured to meet demands in five technology areas: assessment, treatment, containment, stabilization, and retrieval.

Remediation technologies under development by DOE include physical, chemical, and biological treatment, barrier technology, electrokinetics, stream stripping, and in situ vitrification, among others.

This poster session will outline the research currently underway by presenting an overview of the site needs, technology development activities, some of the more mature technologies ready for implementation, and accomplishments made.

Key words: remediation, innovative, technology, DOE.

Poster presentation.

2 • HEAVY METAL REMOVAL AND RECOVERY BY COMBINED PHYTOREMEDIATION AND ANAEROBIC FERMENTATION

Z.A. Samani¹, K. Fukushi², and S. Ghosh², ¹Civil Engineering Department, New Mexico State University, Las Cruces, NM, 88003, and ²Civil & Environmental Engineering Department, The University of Utah, Salt Lake City, UT, 84112

The release of hazardous heavy metals into soil, surface water, and ground water is a major concern. Heavy metal contamination is caused by various industrial activities including the mining, metallurgical, and electroplating industries. Recent research at the University of Utah has shown that microbial biopolymers derived from special bacterial cultures can be very effective in binding heavy metals. These special cultures were developed in the presence of selected biochemical stimulants. Heavy metal removals up to 130% of the dry cell weight were obtained with Cd, Cu, Pb, and Ag. The observed biopolymeric binding capacity is significantly higher than that of activated carbon and other conventional metal-removing media. It is possible to immobilize these special bacterial cells and biopolymers on solid substrates. Photosynthetic materials such as wheat and barley straws were found to remove Pb and Cr up to two percent of the dry weight of straw.

The objective of the research presented here was to examine the technical feasibility of removing heavy metals from contaminated waters using a straw-packed biofilter. Bacterial cells and biopolymers developed in the presence of the stimulants mentioned above are immobilized on solid particles of straw packed into the biofilter. These biofilters act as fixed-film sequential batch reactors (FFSBR) that are used to sequester heavy metals from metal-containing influents. Metals complexed by the biofilter media are eluted with organic acid mixtures obtained from a separate acidogenic reactor operated with fresh or spent straw from the FFSBR. Metals are leached out of the biofilters and recovered as esters of organic acids. Heavy metals are recovered from the leachate by chemical precipitation or by methane fermentation of the organic acid esters with sulfide precipitation.

Key words: heavy metal, phytoremediation, acid fermentation.

Poster presentation.

3 • DNAPL MIGRATION THROUGH A MULTI-AQUIFER AND FRACTURED AQUITARD SYSTEM

D.B. Stephens, M.A. Prieksat, J.A. Kelsey, and M.D. Ankeny, Daniel B. Stephens and Associates, 6020 Academy Road, N.E., Suite 100, Albuquerque, NM, 87109

DNAPL can quickly travel through fractured aquitards when hydrodynamic conditions exist. The flow of DNAPL through the fracture is often driven primarily by hydraulic head with density differences being a secondary component. Laboratory experiments demonstrated the flow of trichloroethane (TCA) through a system consisting of an upper unconfined aquifer and a lower partially-saturated aquifer. These aquifers were separated by a fractured aquitard, across which ground water flow was downward. This process is presented through a series of still photos and a video. The visual results show rapid transport of TCA through the fracture, and the observations were predicted rather well with a multiphase computer code.

Key words: dense nonaqueous phase liquids, fracture, aquitard.

Poster presentation.

4 • ELECTROKINETIC REMEDIATION OF SOIL CONTAMINATED WITH OILFIELD BRINE

C.E. Davis and T.M. Harris, Departments of Chemical Engineering and Chemistry, University of Tulsa, 600 S. College Avenue, Tulsa, OK, 74104

The contamination of soil with brine (salt water) is a common environmental problem associated with the onshore production of oil. The use of electrokinetic remediation to remove sodium chloride from soil was investigated. Experiments were conducted in a test cell that features a "well" containing a stainless steel wire mesh electrode at either end. Experiments involved both real contaminated soil samples and synthetic samples prepared from sand and bentonite and saturated with sodium chloride. During an experiment, distilled water was added incrementally to the cell, and that which accumulated in each well was removed and analyzed. The removal of both chloride ion and sodium ion from the soil was enhanced at the anode well by the application of an applied potential. The addition of calcium sulfate to the soil eliminated the plugging off of soil porosity resulting from pH changes that occurred in the vicinity of both electrodes.

Key words: soil, brine contamination, petroleum, production, electrokinetic remediation.

Poster presentation.

5 • WASTE WATER TREATMENT USING FERRATE TO REMEDIATE AQUEOUS AZODYES

M.D. Johnson, B. Hornstein, and R. Wingo, Department of Chemistry and Biochemistry, New Mexico State University, Las Cruces, NM, 88003

Ferrate represents a new alternative treatment procedure for the rapid chemical oxidation of organic wastes which is safer than ozone or chlorine and has no undesirable side products, such as with permanganate. The aerobic ferrate oxidation of organic compounds produces ferric hydroxide as the sole reduction product.

[FeO₄]^2- --> Fe(OH)_{3 (s)}

This reaction with a variety of organic dyes has been studied in detail and the results will be reported.

Key words: remediation, wastewater, ground water.

Poster presentation.

6 • CONTAMINANT MONITORING OF RODENTS AT A RADIOACTIVE WASTE BURIAL SITE, LOS ALAMOS NATIONAL LABORATORY

J. Biggs, K. Bennett, and P.R. Fresquez, Los Alamos National Laboratory, Mail Stop M887, Los Alamos, NM, 87545

Small mammals were sampled at two waste burial sites (1 and 2) at Los Alamos National Laboratory and a control site (Site 3) to identify radionuclides that are present within surface and subsurface soils at waste burial sites, to compare the amount of radionuclide uptake by small mammals at waste burial sites to a control site, and to identify the primary mode of contamination to small mammals, either through surface contact or ingestion/inhalation. Three composite samples of at least five animals per sample were collected at each site. Pelts and carcasses of each animal were separated and analyzed independently. Samples were analyzed for ²⁴¹Am, ⁹⁰Sr, ²³⁸Pu, ²³⁹Pu, total U, and gamma spectroscopy (including ¹³⁷Cs). Significantly higher (parametric t-test at p=0.05) levels of total U, ²⁴¹Am, ²³⁸Pu, ²³⁹Pu, and ⁴⁰K were detected in pelts as compared to the carcasses of small mammals at TA-54. Concentrations of other measured radionuclides in carcasses were nearly equal to or exceeded the mean concentrations in the pelts. Our results show higher concentrations in pelts compared to carcasses, which is similar to what has been found at waste burial/contaminated sites outside of Los Alamos National Laboratory. Site 1 had significantly higher (alpha=0.05, P=0.0095) total U concentrations in carcasses than Sites 2 and 3. Site 2 had significantly higher (alpha=0.05, P=0.0195) ²³⁹Pu concentrations in carcasses than either Site 1 or Site 3. A significant difference in ⁹⁰Sr concentration existed between Sites 1 and 2 (alpha=0.05, P=0.0681) and concentrations of 40K at Site 1 were significantly different from Site 3.

Key words: small mammals, radionuclides, contaminant, carcasses.

Poster presentation.

7 • CONTAMINANT MONITORING OF BIOTA DOWNSTREAM OF A RADIOACTIVE LIQUID WASTE TREATMENT FACILITY, LOS ALAMOS NATIONAL LABORATORY

K. Bennett, J. Biggs, and P.R. Fresquez, Los Alamos National Laboratory, Mail Stop M887, Los Alamos, NM, 87545

Small mammals, plants, and sediments were sampled at one upstream location (Site 1) and two downstream locations (Site 2 and Site 3) from a radioactive liquid waste treatment facility at Los Alamos National Laboratory, Los Alamos County, New Mexico. The purpose of the sampling was to identify radionuclides potentially present, to quantitatively estimate and compare the amount of radionuclide uptake at specific locations (Site 2 and Site 3) within a canyon system (Mortandad Canyon) to an upstream site (Site 1), and to identify the primary mode (inhalation/ingestion or surface contact) of contamination to small mammals. Three composite samples of at least five animals per sample were collected at each site. Pelts and carcasses of the animals were separated and analyzed independently. In addition, three composite samples were also collected for plants and sediments at each site. Samples were analyzed for ²⁴¹Am, ⁹⁰Sr, ²³⁸Pu, ²³⁹Pu, and total U. With the exception of total U, all mean radionuclide concentrations in small mammal carcasses and sediments were significantly higher at Site 2 than Site 1 or Site 3. No differences were detected in the mean radionuclide concentration of plant samples between sites. However, some radionuclide concentrations found at all three sites were higher than regional background. No differences were found between mean carcass radionuclide concentrations and mean pelt radionuclide concentrations, indicating that the modes of contamination (ingestion/inhalation and surface contact) may be equally occurring.

Key words: rodents, plants, sediments, radionuclide concentrations

Poster presentation.

8 • DEVELOPMENT OF POLYHYDROXAMATE CHELATORS FOR APPLICATIONS TO ACTINIDE REMEDIATION

W.C. Bisset¹, O. Zincircioglu¹, P.H. Smith², and A.S. Gopalan¹, ¹Department of Chemistry and Biochemistry, New Mexico State University, Las Cruces, NM, 88003, and ²Los Alamos National Laboratory, Los Alamos, NM, 87545

The goal of our program is to develop cost-effective chelators for the specific complexation and subsequent removal of actinide ions from soils and waste waters. In this context, we have synthesized and evaluated the metal ion binding properties of a number of new polyhydroxamate chelating agents. The synthesis and binding properties of some polyhydroxamates having the ligand moieties preorganized around a benzene spacer group has been recently disclosed (Gopalan et al., in Separations of Elements, Plenum, NY, 1995). This study has now been extended to acyclic polyhydroxamates, having a diamine backbone. Simple synthetic strategies towards a number of these new and modified polyhydroxamates as well as the results of their preliminary binding studies with metal ions including thorium, iron, uranyl, and lanthanum will be reported. The goals are to understand the potential cooperativity between the ligand moieties appended to a diamine spacer group in this class of chelators with respect to metal ion binding and to develop analogs having higher actinide affinities and selectivities .

Key words: polyhydroxamate chelators, actinides, remediation, selectivity.

Poster presentation.

9 • DEVELOPMENT OF TAILORED BIOFILTER FOR REMOVAL OF HEAVY METALS

Z.A. Samani¹ and S. Ghosh², ¹Civil Engineering Department, New Mexico State University, Las Cruces, NM, 88003, and ²Department of Civil and Environmental Engineering, University of Utah, Salt Lake City, UT, 84102

The release of hazardous heavy metals into soil, surface water, and ground water is a major concern. Heavy metal contamination is caused by various industrial activities including the mining, metallurgical, and electroplating industries. Recent research at University of Utah has shown that specially-grown biopolymers can be very effective in binding heavy metals. In this research, heavy metal removal of up to 130% of the dry cell weight was observed. This binding efficiency is significantly higher than activated carbon. A number of photosynthetic materials may also be used to remove heavy metals. Recent research at New Mexico State University has shown that wheat and barley straw can remove heavy metals up to two percent of the dry weight of straw. This paper describes a novel approach by combining the two techniques to produce a bacteria-tailored straw for a more efficient and economical removal of heavy metals from contaminated water.

Key words: heavy metal, bioremoval, phytoremediation, environment.

Poster presentation.

10 • CS-137 CONTAMINATION MEASUREMENTS OF TECHA RIVER BANK TERRITORY IN BRODOKALMAK SETTLEMENT

A.V. Chesnokov¹, A.P. Govorun¹, V.I. Liksonov¹, S.B. Scherbak¹, M.V. Ivanitskaya², and L.N. Isaeva², ¹RECOM Ltd, str. Schukinskaya, 12-1, Moscow, 123182, RUSSIA, and ²Rosgidromet, str. Vitebskaya, 15, Chelyabinsk, 454048, RUSSIA

The Cs-137 contamination mapping (with a scale of 1:2,000) of 1 sq km Techa river bank territory inside the settlement Brodokalmak is carried out. The electron maps of Cs-137 contamination distribution of bank landscape are created. Measuring collimated scintillated detector technique was used for Cs-137 stock measurements. This method allows for the determination of total Cs-137 stock and thickness of soil layer containing more than 80% of total stock in-site. The RKG-09N device was used for these measurements.

It was shown that Cs-137 contamination has a very heterogeneous character and the stock means achieve 10⁷ Bq/m² at some places. The comparison between the above-mentioned technique and traditional probe method was carried out at specially selected places. The gamma spectrometer laboratory data have shown a good agreement with site data. Additionally the probes were investigated to determine the surface soil Sr-90 activity. It was shown that the Cs-137 contamination correlates with the Sr-90 contamination within the bank territory of separate settlement. The total Cs-137 stock contained at the investigated territory is near 6.6x10¹¹ Bq. The estimation of total Sr-90 stock here is near 2.2x10¹¹ Bq.

Key words: Cs-137 contamination, gamma radiation, beta radiation, mapping, collimated scintillated detector, probe method.

Poster presentation.

11 • GAMMA LOCATOR TO DETERMINE SPECTRUM CHARACTERISTICS OF QUANTUM FLUX

A.V. Chesnokov, A.A. Gulyaev, S.M. Ignatov, V.N. Potapov, and L.I. Urutskoev, RECOM LTD, str. Schukinskaya, 12-1, Moscow, 123182, RUSSIA

The gamma-locator for contamination survey inside the premises connected with the nuclear production is developed.

The device consists of the detector head and the remote control unit connected with a cable (>100 m). The detector head (500x500x400 mmxmmxmm, with weight near 40 kg) is the collimated scintillated gamma detector installed at the scanning unit. The gamma detector is placed into the lead shielding with a collimator having an entrance angle near 10º. The detector head is supplied by TV camera and laser distance device.

The remote control unit provides operation and processing of the acquiring information.

A gamma detector is based on a system of scintillator CsI(T1) and Si photodiode. The detector energy resolution (it's near 9% for the radiation of Cs-137) provides the identification of gamma-radiating isotopes such as Co-57, Cs-137, K-40, Co-60, I-131, and Eu-154. The gamma locator threshold of determination is 250 Bq/cm² for 10 cm³ scintillator and Cs-137 radiation.

The system allows for measurement of the effective surface activity density (for Cs-137 radiation) of all premise surfaces and reconstruction of the exposed dose rate distribution within the volume of investigated space.

Key words: contamination survey, gamma radiation, collimated scintillated detector, scintillator, photodiode.

Poster presentation.

12 • ESTIMATION OF GEOCHEMICAL BACKGROUND LEVELS FOR ENVIRONMENTAL STUDIES USING EXISTING DATA SOURCES

F. Luo, J.M. Barker, and C.E. Chapin, New Mexico Bureau of Mines and Mineral Resources, New Mexico Tech, 801 Leroy Place, Socorro, NM, 87801-4796

Calculation of geochemical background levels for use in environmental mitigation is always a problem. One of the major impediments is the disparate data available in widely-scattered source materials. A central database that can accept data in any form and that can be easily reorganized at will is a tool that greatly reduces the adverse effects of disparate data.

The New Mexico Bureau of Mines and Mineral Resources, under contract with the U.S. Bureau of Mines via their Hispanic Association of Colleges and Universities (HACU) program, has developed a database, the Generalized Data System (GDS), capable of handling disparate environmental and other data. The GDS can handle any data, but the initial project is oriented toward environmental activities at mining sites.

Various data at or near the Kelly lead-zinc mining district, near the town of Magdalena in west-central New Mexico, were entered into a customized version of the Paradox relational database used at the core of GDS. Approximately 2,600 data points were used to calculate various background levels using standard statistical techniques.

The GDS is unique because it is structured to allow easy forming, deleting, merging, or dividing of data fields. This is a critical feature, not found in other databases, that allows rapid, efficient organization of disparate data. These data have formats and other attributes that cannot be entirely anticipated in pre-defined data fields. Rather, data fields must be defined "on the fly" during data entry as unexpected data formats appear. The GDS supplies this capability as its primary design feature.

Key words: background, database, environment, geochemical, mining.

Poster presentation.

13 • ULTRASOUND-MODIFIED CUPRIC ION ADSORPTION ON IRON (III) FLOCS

H. Campos¹ and P.E. Wheat², ¹Environmental Technology Program, University of Northern Iowa, Cedar Falls, IA, 50614-0421, and ²Department of Industrial Technology, University of Northern Iowa, Cedar Falls, IA, 50614-0178

A model system to investigate the ability of intense ultrasound to enhance the removal of potentially hazardous metallic ions from aqueous solution via modified iron hydroxide adsorption/coprecipitation has been conducted. The experimental data indicates that ultrasonic disruption of pre-formed ferric hydroxide flocs can modify the removal efficiency of metallic ions from aqueous solution. The methodology is effective over copper to iron molar concentration ratios ranging from 10-30% and pHs of 7.5-9.5.

Key words: ultrasound, iron (III) hydroxide, co-precipitation, adsorption, pH.

Poster presentation.

14 • EVALUATING THE BIOACCUMULATION OF HEAVY METALS AND ORGANICS IN AN AQUATIC ENVIRONMENT

J.L. Regens, K.H. Watanabe, D.G. Hodges, K. Johnson, and C.M. Swalm, Energy Spatial Analysis Research Laboratory, Tulane University Medical Center, 1430 Tulane Avenue SL-1, New Orleans, LA, 70112-2699

The improper storage, use, or disposal of hazardous substances, especially heavy metals and chlorinated hydrocarbons, can contaminate an array of environmental receptors ranging from soils, surface water, and sediments to ground water. Such contamination may result in health or ecological risks depending on the specific contaminants-of-concern, their concentrations, and the existence of active pathways for exposure for human or ecological receptors. As a result, growing concern about the efficacy of remediation technologies underscores the need for valid, reliable data emphasizing risk-based site assessments to delineate the dynamics of pollutant transport and fate. This poster presents the results of an ongoing study that examines bioremediation and bioaccumulation of heavy metals and organics in Devil's Swamp, Louisiana. Primary contaminants-of-concern include arsenic, cadmium, chromium, lead, mercury, hexachlorobenzene, and hexachlorobutadiene. Contaminant concentrations in water, sediment, and fish specimens will be presented based on historical records collected as part of the EPA Superfund listing process as well as data collected from 1994-1995.

Key words: environmental fate and transport, site assessment, remediation.

Poster presentation.

15 • IMMOBILIZATION OF INDUSTRIAL WASTE IN CEMENT MATRIX

I. Plecaš and A. Peric, Institute of Nuclear Sciences "Vinca," P.O. Box 522, 11001 Belgrade, YUGOSLAVIA

Results are presented of a series of experimental tests performed to determine the influence of matrix characteristics on the leaching mechanism of copper aluminum oxychloride immobilized into cement matrices. The objective of this research was to investigate the leaching mechanism of copper as a constituent of copper aluminum oxychloride ("CAOX").

Key words: immobilization, cement, leaching rate, diffusion, cumulative fraction.

Poster presentation.

16 • THE UPTAKE OF STRONTIUM BY CHAMISA (CHRYSOTHAMNUS NAUSEOSUS) SHRUB PLANTS GROWING OVER A FORMER LIQUID WASTE DISPOSAL SITE AT LOS ALAMOS NATIONAL LABORATORY

P.R. Fresquez, T.S. Foxx, and L. Naranjo, Jr., Environmental Assessments and Resource Evaluations Group (ESH-20), Environment, Safety, and Health Division, MS M887, Los Alamos National Laboratory, Los Alamos, NM, 87545

Chamisa (Chrysothamnus nauseosus) shrub plants growing over a former lanthanum (40 h half-life) and strontium (⁹⁰Sr) (28 y half-life) contaminated liquid waste disposal site (structures were excavated, removed, and backfilled in 1963) in Bayo Canyon at Los Alamos National Laboratory (LANL) were collected and analyzed for ⁹⁰Sr. Surface soil samples (0- to 2-inch depth) were also collected from below (understory) and between (interspace) shrub canopies. Chamisa plants growing over the site contained significantly higher concentrations of ⁹⁰Sr than a control plant-one plant, in particular, contained 90,500 pCi ⁹⁰Sr g^-1 ash in top-growth material. Similarly, soil surface samples collected underneath (avg. = 115 pCi g^-1) and between (avg. = 14 pCi g^-1) plants contained ⁹⁰Sr above regional upper limit background (0.82 pCi g^-1) and LANL screening action soil levels (5.90 pCi g^-1); this probably occurred as a result of chamisa plant leaf fall contaminating the soil understory area followed by water and/or winds moving ⁹⁰Sr to the soil interspace areas. Although some soil-surface migration of ⁹⁰Sr has occurred, the level of ⁹⁰Sr in sediments collected downgradient of the site at the Bayo Canyon/New Mexico State Road 4 intersection (0.10 pCi g^-1) was still within the regional upper limit background sediment concentration (0.87 pCi g^-1).

Key words: radionuclides, ⁹⁰Sr, vegetation, contamination, transport.

Poster presentation.

17 • ENVIRONMENTAL PROGRAM AT JACKSON STATE UNIVERSITY

P.-C. Yuan, Hazardous Material Management Program, Jackson State University, Jackson, MS, 39217

Jackson State University is one of the Historically Black Colleges and Universities (HBCU) in the South. The School of Science and Technology includes seven different departments. The Hazardous Material Management program started in 1988 under the Department of Technology and Industrial Arts. In 1994 the Institute of Higher Learning approved the master degree for Hazardous Materials Management. In the Biology department, the school offers the master degree and the only approved Ph.D. degree in Environmental Science in Mississippi since 1990. Recently, the Department of Technology and Industrial Arts received a $1.5 million grant from the National Institute of Health for the next five years as a environmental training center for minorities, Indian Tribes, and the general public. Training courses emphasize lead abatement, hazardous waste work at hazardous waste site at different levels, such as worker, trainer, supervisor, and technician.

Key words: minority, training, hazardous material, lead abatement.

Poster presentation.

18 • MICROBIAL POPULATION DYNAMICS AND BIODEGRADATION KINETICS OF ORGANIC POLLUTANT MIXTURES

J.D. Rogers¹, N.M. DuTeau², S.J. Chacko¹, and K.F. Reardon¹, Departments of ¹Chemical and Bioresource Engineering and ²Microbiology, Colorado State University, Fort Collins, CO, 80523-1370

Contamination of ground water and soil is most often a mixture of pollutants, and these mixtures are transformed by mixtures of microorganisms. However, few quantitative studies of biodegradation kinetics have addressed these complex mixture aspects. The goal of the work presented in this poster is to measure changes in both the chemical and microbial concentrations during mixed culture-mixed pollutant biodegradation.

A simple two-species microbial system was chosen as the first test of our methods. Pseudomonas putida F1 and P. sp. JS150 are capable of growth on various aromatic hydrocarbons; however, P. sp. JS150 has a wider substrate range that includes chlorobenzene. Species-specific genetic markers were developed for both organisms. These markers were used to develop and test several molecular techniques for quantitation of the population of each species in biodegradation experiments. Conventional differential plating techniques were used as a validation for each method screened. Mathematical modeling was used to determine the relationships between the composition of the microbial and pollutant mixtures and to describe the interactions between the two species. The population dynamics of the mixed microbial population was found to be related to the changes in the composition of the pollutant mixture, and interaction between the two species was apparent. These results suggest that single species/single pollutant biodegradation kinetics are not readily extended to more complex systems.

Key words: biodegradation, mixtures, kinetics, populations.

Poster presentation.

19 • ASSESSMENT OF BRINE CONTAMINATION OF SURFACE WATERS AND SOIL USING ION-SELECTIVE ELECTRODES

R. Yates¹, T.M. Harris², and K. Sublette¹, ¹Department of Chemical Engineering and ²Department of Chemistry, University of Tulsa, 600 S. College Avenue, Tulsa, OK, 74104

The contamination of soil, surface waters, and ground water is a common environmental problem associated with handling and disposal of brine in oil field operations. The primary components of this salt contamination may be quantified by more than one analytical method; however, the use of direct potentiometry with ion-selective electrodes is most attractive because it is reasonably accurate, fast, and may even be used in the field. In this study, a series of pond water samples and extracts from brine-contaminated soils were analyzed using a sodium ion electrode and a "hardness" electrode, and the results were compared with those obtained by atomic absorption spectrophotometry. Also, chloride measurements made using a chloride electrode were compared to those obtained with an amperometric technique.

Key words: soil, surface water, salt contamination, analysis, ion-selective electrodes, oil field operations.

Poster presentation.

20 • CORRELATION OF SURFACE WATER QUALITY AND OIL PRODUCTION IN THE TALLGRASS PRAIRIE PRESERVE

R. Yates¹, K. Sublette¹, T. Harris², and B. Tapp³, ¹Department of Chemical Engineering, ²Department of Chemistry, and ³Department of Geosciences, University of Tulsa, 600 S. College Avenue, Tulsa, OK, 74104

The contamination of soil with salt is a common environmental problem associated with handling and disposal of brine co-produced with petroleum. The salt is relatively mobile, and thus may pose a threat to nearby surface waters. There are over 100 ponds within the Tallgrass Prairie Preserve, a 40,000 acre preserve operated by The Nature Conservancy. Oil and gas have been produced from shallow reservoirs beneath this area for over 80 years. Damage to vegetation (and subsequent erosion) is evident at several production sites. The objective of this study was to correlate the chemical composition of the water in each of the ponds with production sites and the surrounding topography.

Key words: surface water, salt contamination, oil production, Tallgrass Prairie Preserve.

Poster presentation.

21 • RDX AND HMX SORPTION IN THIN DISK SOIL COLUMNS

D.M. Townsend¹, T.E. Myers¹, and D.D. Adrian², ¹U.S. Army Engineer Waterways Experiment Station, 3909 Halls Ferry Road, Vicksburg, MS, 39180-6199, and ²Louisiana State University, Baron Rouge, LA, 70803

Subsurface contamination by 2,3,5-trinitro-1,3,5-triazine (RDX) and oxyhydro-1,3,5,7-tetranitro-1,3,5,7-tetrazocine (HMX) has prompted remediation and containment efforts at many Army installations. Contaminant transport modeling, a time- and cost-effective tool for comparing various remediation alternatives, is hampered by lack of information on the significance of RDX and HMX disappearance and sorption in soils.

This study was conducted to estimate RDX and HMX disappearance and sorption parameters from breakthrough curves (BTCs) for three soils-a silt loam, a clay-rich soil, and Ottawa sand. Thin disk soil columns (0.32 cm soil length) were used to obtain RDX and HMX BTCs. Effluent RDX and HMX concentrations were analyzed as a function of pore volumes eluted.

The thin disk columns produced approximately symmetrical RDX and HMX BTCs for each soil. The BTCs were modeled assuming complete-mix, first-order disappearance, and linear equilibrium sorption. This model produced excellent curve fits, with only slight discrepancies between the model and the observed data. Good mass balances were observed for each soil for both RDX (102.0 to 105.0 percent) and HMX (101.6 to 110.2 percent).

Both RDX and HMX tended to sorb weakly to the soils used in this study. Linear equilibrium distribution coefficients (K_d) for RDX ranged from 1.35 to 5.7 l/kg. Linear equilibrium distribution coefficients for HMX ranged from 1.45 to 8.5 l/kg. Mass balance analysis indicated that disappearance (transformation, irreversible sorption, etc.) of RDX and HMX was negligible in this study.

Key words: RDX, HMX, ground water, sorption, transport.

Poster presentation.

22 • PHYTOREMEDIATION OF LEAD-CONTAMINATED SOILS BY NATIVE SPECKS AT AN ABANDONED MINE SITE IN UTAH

S.P. Klassen, J.E. McLean, P.R. Grossl, and R.C. Sims, Utah Water Research Laboratory, Utah State University, Logan, UT, 84322-8200

Heavy metal uptake by native vegetation was investigated at an abandoned mine site contaminated with high levels of Pb, Zn, and Cd. Two tree and one sedge species were identified as possible hyperaccumulators of lead at this site. Hydroponics and soil column studies are currently in progress to further examine the accumulation of lead in these species. A comparison of different populations of seedlings will be made to determine if mine site populations are distinct with respect to lead tolerance and accumulation. The potential for phytoremediation of lead-contaminated sites is examined.

Key words: phytoremediation, lead, mine soils, trees, sedge.

Poster presentation.

23 • EFFECT OF POPLAR RHIZOSPHERE ON MICROBIAL POPULATIONS THAT DEGRADE PRIORITY POLLUTANTS

L. Foster, M.E. Vermace, and P.J.J. Alvarez, The University of Iowa, Department of Civil & Environmental Engineering, Iowa City, IA, 52242

Phytoremediation, the use of plants to remove environmental pollutants from contaminated sites, holds great promise as a low-cost remedial approach. Indeed, the ability of poplar (Populus spp) trees to enhance site remediation is well documented. Nevertheless, the rational development of this remedial technique is limited by our incomplete understanding of the specific remediation mechanisms. While poplars have been shown to remove pollutants by vegetative uptake and in-plant degradation, very little is known about the effect that the poplar roots have on microbial degradation activity and diversity. The purpose of this project was to investigate the relative abundance of indigenous microorganisms in the poplar rhizosphere that are capable of degrading priority pollutants.

Microbial populations from the root zone of 7-year-old poplar trees were characterized by concentration and catabolic capacity. The concentrations of total heterotrophs, denitrifiers, pseudomonads, BTX degraders, and atrazine degraders were determined using appropriate Most Probable Number (MPN) techniques. For each of these phenotypes, the MPN concentrations in three rhizosphere soil samples were compared to those in three surrounding (control) soil samples. The tested soils (collected from a depth of about 150 cm) had prior exposure to nitrate, but no known prior exposure to BTX or atrazine. Whether MPN differences were significant was evaluated statistically using Student's T-test. Rhizosphere and surrounding soils were also examined for microbial diversity. This analysis consisted of quantifying the number of (different) colony types, based on the morphology of microbial colonies grown on agar plates.

The number of colony types (NCT) grown on agar plates were similar for rhizosphere (NCT were 6, 7, and 5) and surrounding soils (NCT were 6, 2, and 10), indicating that the diversity of culturable heterotrophs was similar for both soils. Nevertheless, the concentrations of all types of organisms investigated were significantly higher in the rhizosphere than in the surrounding soils. For total heterotrophs, the differences were significant at the 95% level. For pseudomonads, denitrifiers, and BTX degraders, the difference was significant at the 90% level. When the abundance of individual phenotypes is expressed as a fraction of the total heterotrophs, the relative concentrations of pseudomonads and BTX degraders in the rhizosphere are also greater than in surrounding soils at the 90% significance level. In addition, only one of the six soil samples (i.e., a rhizosphere sample) exhibited atrazine degradation activity. These results suggest that the root zone may exert preferential selection for desirable phenotypes. Apparently, the poplar rhizosphere constitutes an enhanced growth environment for a wide variety of beneficial microorganisms.

To further explore the mechanisms by which the poplar rhizosphere enhances microbial biodegradation activity, poplar root exudates were tested as inducers of toluene dioxygenase (TDO) in Pseudomonas putida F1 (PpF1). TDO is an environmentally-relevant enzyme because of its ability to degrade numerous priority pollutants, including benzene, toluene, and trichloroethylene (TCE). Preliminary ELISA results indicate that an as yet undetermined component(s) of poplar root exudates induces TDO in PpF1.

In summary, this work suggests that poplar root exudates might enhance the viability of beneficial microorganisms and enhance natural bioremediation processes. The proliferation of desirable phenotypes in the root zone would be conducive to enhanced contaminant removal rates, and thus, reduced duration (and cost) of site remediation.

Key words: atrazine, BTX, biodegradation, rhizosphere, root exudates, toluene dioxygenase.

Poster presentation.

24 • TRACER TESTS FOR EVALUATING AIR SPARGING AND IN-WELL AERATION TREATMENT SYSTEMS

J.S. Berkey, W.J. Doucette, and R.R. Dupont, Utah Water Research Laboratory, Utah State University, Logan, UT, 84322-8200

Tracer tests are being conducted in support of an upcoming field project designed to evaluate the effectiveness of air sparging and in-well aeration for remediation of a gasoline-contaminated site. Laboratory simulations of the treatment systems are being performed in porous media, filled stainless steel tanks with clean and contaminated water. The utility of several tracers, including sulfur hexafluoride, helium, bromide, and fluorescein, for the evaluation of flow patterns, flow rates, and volumes of influence will be investigated. Bromide and dye tracers will be monitored in the saturated zone, while sulfur hexafluoride and helium will be monitored in both the saturated and unsaturated zones. Results from the laboratory studies will be used to compare the performance of various tracer substances, compare the hydraulic effects of the air sparging and in-well aeration systems, and optimize experimental design for the field scale tracer tests.

Key words: tracers, ground water remediation, air injection, in-well aeration, air sparging.

Poster presentation.

25 • LABORATORY EVALUATION OF OXYGEN TRANSFER RATES AND TRANSFER EFFICIENCIES OF AIR SPARGING AND IN-WELL AERATION

S. Miller, Utah Water Research Laboratory, Utah State University, Logan, UT, 84322-8200

Two methods for the introduction of oxygen into an aqueous environment were evaluated in a laboratory setting: air sparging and in-well aeration. Air sparging is a remediation technique in which air is introduced directly into a formation to produce air/soil contact and stripping of contaminants. In-well aeration provides a technique for the movement and air stripping of contaminated ground water through the action of an air-lift pump inside the well head. These two air-injection methods were examined in a clean water system. Measurements were taken to determine the effect each transfer method had on the distribution and mass transfer rate of oxygen in laboratory-scale systems. The ASCE standard method for oxygen transfer rate determinations in a clean water system was the experimental method employed in the study. This is the initial portion of a larger HSRC-funded project in which oxygen transfer in saturated soils in laboratory and field-scale systems will be examined. For comparability with the field study, laboratory-scale air flow rates were scaled from those used in the field portion of the project. Lab oxygen transfer rates and transfer efficiency results from the two air-injection systems will be presented and contrasted, and extension of these findings to field-scale applications will be made in this poster presentation.

Key words: air sparging, ground water remediation, oxygen transfer, lab-scale systems, dissolved oxygen, oxygen transfer, in-well aeration.

Poster presentation.

26 • BIODEGRADATION OF CHELATING AGENTS USED FOR METAL REMOVAL FROM CONTAMINATED SOILS

T. Regmi¹, S.K. Banerji¹, and A. Hong², ¹Department of Civil Engineering, University of Missouri, Columbia, MO, 65211, and ²Department of Civil Engineering, University of Utah, Salt Lake City, UT, 84112

Effectiveness of chelating extraction for removal of metals from contaminated soils has been investigated by many researchers. The results have shown that this method can effectively extract metals from soil-water phase and precipitate them out in form of hydroxides and hydroxy-carbonates while the chelators can be reused.

The chelating compounds used for heavy metals extraction from contaminated soils are organic compounds and are subject to biodegradation under field conditions. During the chelating extraction with recycling of chelating agents, naturally-occurring microorganisms in the soil can essentially develop an enzymatic system capable of metabolizing these chelating compounds, thereby reducing the amount present in the solution for successive reuse.

Six chelating compounds have been selected for studying chelating extraction of contaminated soils. At this time the biodegradabilities of three of these compounds have been evaluated. These compounds are Ethylenediaminetetraacetate (EDTA), 2,6-Pyridinedicarboxylic acid (PDA), and S-Carboxymethyl-L-Cysteine (SCMC).

EDTA was degraded up to 2 mM equally with and without soil exhibiting strong inhibition at higher concentrations. Biodegradation rates for EDTA have been determined to be very low

PDA was metabolized by acclimated mixed culture as a sole source of carbon and energy equally with and without soil. PDA was completely eliminated from solution at concentrations up to 6 mM within 36 hours, showing no inhibition at these high concentrations.

SCMC has also been found to be degraded by acclimated mixed culture. The data generated will be used to determine kinetic parameters for degradation of these compounds.

Key words: soil remediation, chelating agents, chelating extraction, biodegradation, enzymatic inhibition.

Poster presentation.

27 • TREATMENT OF WOOD PRESERVATIVE-CONTAMINATED SOILS AS AFFECTED BY ELECTRON ACCEPTOR ADDITION

K.C. Nieman, R.C. Sims, R.A. Petrie, and J.L. Sims, Division of Environmental Engineering and Utah Water Research Laboratory, Utah State University, Logan, UT, 84322-4110

Two wood preservative-contaminated soils from two Superfund sites, containing polycyclic aromatic hydrocarbons (PAH) and pentachlorophenol (PCP), were treated using oxygen as the electron acceptor and oxygen plus manganese as electron acceptors. Poisoned controls were used to evaluate the roles of biotic versus abiotic reactions. Differences among treatments were measured by determining specific parent compounds and biotransformation intermediates. Indicator compounds were measured in: (1) water soluble extracts for evaluation of chemical leaching, and (2) solvent extracts for evaluation of soil-associated chemicals. In addition, the Microtoxä assay was used to evaluate water soluble (leachate) toxicity. Effectiveness and economics with regard to treating wood preservative-contaminated soil by addition of manganese were evaluated.

Key words: bioremediation, wood preservative, land treatment, polycyclic aromatic hydrocarbons, pentachlorophenol.

Poster presentation.

28 • A BATCH REACTOR FOR CONTROL OF Eh, pH, AND TEMPERATURE OF SUBSURFACE AQUEOUS SYSTEMS

R.A. Petrie¹, R.C. Sims¹, and P.R. Grossl², ¹Division of Environmental Engineering and Utah Water Research Laboratory, Utah State University, Logan, UT, 84322-4110, and ²Department of Plant Soils and Biometerology, Utah State University, Logan, UT, 84322-4820

Oxidation-reduction (redox) reactions influence the fate, transport, and transformation of organic chemicals in subsurface environments. Lack of availability and complex operation of reactors that are available regarding the simulation of the subsurface environment at a particular site with regard to redox, pH, and temperature present significant constraints to current attempts to understand subsurface reactions and to develop remediation management decisions.

This poster presents the design and operation of a simple bench-scale batch reactor that is used to control redox potential, pH, and temperature of an aqueous subsurface system. The reactor can be used to maintain environmental conditions for evaluation of intrinsic remediation or can be used to adjust environmental conditions to a new steady state for evaluation of the effect of engineered remediation on a subsurface system, as well as to evaluate requirements for chemical addition to adjust subsurface environments to different environmental values. The reactor can operate over a wide range of redox potential values, from -400 mV to +400 mV, and pH values. Parameters can also be controlled for small incremental changes. The redox potential can be controlled within 1-2 mV, pH within 0.05-0.1 unit, and temperature within 0.1°C for weeks or months. Results for the reactions and fate of subsurface minerals and pentachlorophenol at different redox and pH values will be presented.

Key words: redox, pH, reactor.

Poster presentation.

29 • HEAVY METALS REMOVAL FROM CONTAMINATED WATER SOLUTIONS

Z. Lewandowski, F. Roe, and M.T. Fernandez, Center for Biofilm Engineering, Montana State University, Bozeman, MT, 59717

As a result of an ongoing project, we have developed a novel technology which has potential for removal and recovery of heavy metals from dilute aqueous solutions. Our technology includes three consecutive processes: metal preconcentration, metal stripping, and metal recovery. In the first step the metals are bound to biopolymers from dilute solutions. In the second step the metals are desorbed by shifting chemical equilibrium to form concentrated solutions. In the third step the metals are recovered from the concentrated solution by electroplating. The second and third steps can be accomplished simultaneously. In effect the biopolymer is regenerated and the metals are removed and recovered in metallic form that is easy to handle and is not toxic. The regenerated biopolymer is recycled to the process and used many times. Additionally, the metals can be removed selectively, by selective electroplating. This is a major advantage in cases where a metal of high market or strategic value is recovered from a mixture with other metals.

Metal preconcentration was studied in detail using absorption of metals by alginate gel beads. Mixtures of copper and zinc ions in solutions with pH ranging from 2.6-5.4 were tested. Binding group density of alginate gel, and binding stability constants of the respective metals in solution were calculated from experimental data. Using these parameters a new model was developed to predict the equilibrium concentrations of copper, zinc, and hydrogen ions in the presence of alginate gel beads. The experimental data closely fit the extended Langmuir model allowing binding group density and stability constants to be determined. The equilibrium concentrations of each species predicted by the new model agree well with experimental concentrations.

Key words: heavy metal, water, metal recovery, metal stripping, metal preconcentration.

Poster presentation.

30 • ASSESSMENT OF NATURAL ATTENUATION OF HEXAVALENT CHROMIUM IN GROUND WATER: USCG SUPPORT CENTER, ELIZABETH CITY, NORTH CAROLINA

R.W. Puls and C.J. Paul, National Risk Management Research Laboratory, USEPA, P.O. Box 1198, Ada, OK, 74820

The natural attenuation of hexavalent chromium has been evaluated at a field site near Elizabeth City, North Carolina, to provide guidance on this type of site assessment for remedial decision-makers. Laboratory and field test methods are presented together with results for this particular site. Geochemical indicators important for assessment of natural attenuation are listed and discussed. The importance of site characterization is emphasized to support "natural attenuation" as a remedial alternative or as a complement to other remedial measures.

(This is an abstract of a proposed presentation and does not necessarily reflect EPA policy.)

Key words: natural attenuation, chromium, chromate, ground water remediation, site assessment, site characterization.

Poster presentation.

31 • CELLS ON FOAM AND FIBER

R. Clyde, Clyde Engineering, P.O. Box 740644, New Orleans, LA, 70174

When a steel screen is put around foam, it is made heavier so it can be fluidized. Cells grow on the foam.

When the bacterium Zymomonas mobilis is put on Tyvek fiber, toxic metals such as lead and chromium can be removed from wastewater in two seconds.

When a rotary biological contactor is run half full and a light shone in the top, the light hits a thin moving film. In other photo reactors, colored or turbid solution blocks the light.

Ethanol can be produced from sugar in 15 minutes.

Corrugated fibers can be used. Old cardboard boxes are readily available. Calcium magnesium acetate, a non corrosive road deicer, can be made with cells on rotating fibers.

Key words: fiber, foam, metal, reactor.

Poster presentation.

32 • BIOAVAILABILITY AND RISK ASSESSMENT OF CONTAMINATED SOIL USING AQUEOUS AND SOLVENT EXTRACTION

N. Bordelon, H. Huebner, K. Washburn, L. He, K.W. Brown, and K.C. Donnelly, Department of Veterinary Anatomy and Public Health, Texas A&M University, College Station, TX, 77843-4458

Contaminated media at Superfund sites typically consist of complex mixtures of organic and inorganic chemicals. While a site may host a limited number of inorganic chemicals, literally thousands of organic chemicals may be present. These mixtures are difficult to characterize, both analytically and toxicologically, especially the complex mixtures of polycyclic aromatic hydrocarbons (PAHs). The current approach to risk assessment assumes that all contaminants are available for human uptake. EPA protocol uses solvent extraction to remove chemicals from the soil as a basis for estimating risk to the human population. However, contaminants that can be recovered with a solvent extract may not represent chemicals that pose a threat to human health via leaching or absorption. Chemicals that are tightly bound to the soil are unlikely to migrate to ground water. A system using aqueous extraction provides a more realistic picture of the threat contaminated soils pose to the human population. A preliminary study was conducted with coal tar-contaminated soil spiked with benzo(a)pyrene (BaP), a known animal carcinogen, and trinitrotoluene (TNT). Samples were extracted with methylene chloride (MeCl₂) or water titrated to pH 2 and pH 7. The samples were tested for genotoxicity using Salmonella typhimurium strain TA98 with and without metabolic activation. Chemical analysis demonstrated 100% recovery of the solvent extract and up to 36% and 42% recovery for aqueous extraction at pH 2 and pH 7, respectively. In performing a risk assessment based on chemical analysis, all samples exceeded 1E-6; however, the risk associated with the solvent extract (2.23E-5) was almost one order of magnitude higher than the aqueous extract (pH 2: 3.15E-6 and pH 7: 5.21E-6). These results differ from those obtained through bioassay-based risk assessment. The aqueous extract at pH 7 was genotoxic with a specific activity of 98 net revertants, followed by solvent extract (41 revertants) and aqueous extract at pH 2 (13 revertants). The results indicate that aqueous extraction provides a complementary tool to solvent extraction in performing risk assessments, as well as for remediation assessment. Aqueous extraction takes into consideration the bioavailability of contaminants in the soil giving a more accurate estimate of what contaminants are of major concern.

(This research was supported by NIEHS Grant No. P42ES04917.)

Key words: aqueous extraction, solvent extraction, risk assessment, bioavailability.

Poster presentation.

33 • SOIL SORPTION AND PAH SOLUBILITY ENHANCEMENT USING SURFACTANTS

J. Lay, S.K. Banerji, and R.K. Bajpai, Department of Civil Engineering, University of Missouri-Columbia, E3502 EBE, Columbia, MO, 65211

Synthetic surfactants have been successfully shown to enhance hydrophobic organic compound (HOC) bioavailability by increasing the HOC aqueous solubility. HOC solubility is greatly enhanced when the bulk solution surfactant concentration is above the CMC. Sorption of surfactant onto soils, though, results in a decrease of available surfactant for micellar solubilization of HOCs. The balance between surfactant sorption onto soils, HOC incorporation in surfactant micelles, and HOC sorption on soil depends upon a number of factors, including the surfactant type and concentration, the nature of the soil, the temperature, and the nature of the HOC.

In this study, three nonionic surfactants (Tween 80, Triton X-100, and Triton X-165), one anionic surfactant, and a cosolvent (methanol) have been used to enhance the solubilization of PAHs and PCP. Other variables used in testing include five soils (including an aged soil), two soil slurry concentrations (10% and 20% w/w), and three temperatures (15°, 25º, and 35ºC).

Adsorption isotherms and PAH/PCP solubility enhancement characteristics have been evaluated. Relationships between the soil organic content, surfactant partition coefficients, and octanol/water partition coefficients have been quantified in an effort to describe the solubility enhancements in soil slurries.

Key words: isotherms, adsorption equilibrium, aged soil.

Poster presentation.

34 • BIODEGRADATION OF SEVERAL SOLUBILITY ENHANCES BY ACTIVATED SLUDGE AND AN ENRICHED CULTURE

J. Gu, S.K. Banerji, and R.K. Bajpai, Department of Chemical Engineering, University of Missouri-Columbia, W2030 EBE, Columbia, MO, 65211

Use of solubility enhances such as surfactants and cosolvents has often been proposed to increase the rate of biodegradation of sorbed hydrophobic organic chemicals. Bioremediation engineers are thus faced with the questions of microbial toxicity and metabolization of the solubility enhances by microorganisms. In this study, three commercial nonionic surfactants (Tween 80, Triton X-100, and Triton X-165) and one cosolvent (methanol) have been evaluated for their effects on microbial growth and their biodegradation. Laboratory-cultivated activated sludge starting from the local Municipal Waste Treatment Plant and an enriched culture isolated from contaminated soil from a wood-treatment site were grown in baffled shake-flasks in the presence of different concentrations of the solubility enhances. Cell growth as well as surfactant concentrations were monitored. The results of these studies will be presented. These results are intended for use as a guideline for scale-up of soil-slurry reactors.

Key words: biodegradation, surfactants, methanol, Tween 80, Triton.

Poster presentation.

35 • AN EXPERIMENTAL INVESTIGATION OF THE VOLATILIZATION OF BINARY NONAQUEOUS PHASE LIQUID MIXTURES IN UNSATURATED POROUS MEDIA

C. Gaither and L.M. Abriola, Department of Environmental and Water Resources Engineering, University of Michigan, Suite 181 EWRE Building, Ann Arbor, MI, 48109-2125

In this research, the volatilization of nonaqueous phase liquid (NAPL) residuals entrapped in unsaturated sandy porous media is investigated. The compounds studied are representative of those NAPLs commonly found at many contaminated ground water sites. These organic contaminants pose a known human health risk, either through ingestion or exposure to contaminated vapors. This research investigation is designed to provide information on NAPL volatilization rates, which will facilitate more accurate exposure assessment and more accurate predictions of soil vapor extraction remediation performance.

NAPL contaminants are often released to the subsurface as mixtures of organic compounds. In this work, experiments are designed to study volatilization of binary NAPL mixtures. This study follows previous investigations in our laboratory into the volatilization of single component NAPLs in unsaturated sandy media. Binary mixtures were created from the compounds styrene, toluene, and tetrachloroethylene. Residual water and NAPL mixture saturations were emplaced in one-dimensional columns, packed with Wagner sand. Volatilization of the NAPL mixtures was then observed using prepurified nitrogen as the carrier gas at pore velocities approximating field soil vapor extraction operations. The influence of variations in both carrier gas flowrate and NAPL mixture composition on volatilization mass transfer was explored. In addition, carrier gas flow interruptions were used to examine mass transfer rate limitations associated with long-term removal.

Contaminant vapor phase effluent concentration measurements during initial volatilization and later periods of concentration decline are used to evaluate the utility of Raoult's law to predict volatilization behavior. The applicability of a modified Sherwood correlation (Wilkins et al., 1995) developed for NAPL-vapor phase mass transfer in single component systems is also evaluated in the context of binary mixtures.

Funding for this research is provided by the National Institute of Environmental Health Sciences under Grant #ES04911.

Key words: nonaqueous phase liquids, volatilization, unsaturated zone transport.

Poster presentation.

36 • IMPROVED RECOVERY OF HEAVY METALS AND CHELATING AGENTS FOLLOWING EXTRACTION FROM CONTAMINATED SOIL

A. Hong and C. Li, Department of Civil and Environmental Engineering, University of Utah, Salt Lake City, UT, 84112

The use of chelating agents in extracting heavy metals from contaminated soil is seen as a remediation technique. Although strong metal-complexing chelating agents have higher extraction and, therefore, remediation potential, they are more difficult to recover and reuse. Chelating agents having moderate strength in metals complexation were found to be more amenable to their subsequent recovery and reuse. In order to make full use of the strong chelating agent such as EDTA, improved recovery technique must be available. This paper will focus on those strongest chelating agents and will report efforts and results in their recovery and reuse.

Key words: heavy metal, soil remediation, chelating extraction, recovery.

Poster presentation.

37 • EXPERIMENTAL OBSERVATION OF TETRACHLOROETHENE TRANSPORT BEHAVIOR IN AN UNSATURATED SAND COLUMN

C. Yu and M.H. Conklin, Department of Hydrology and Water Resources, The University of Arizona, Tucson, AZ, 85721

Transport of tetrachloroethene (PCE) through variably saturated sand was studied in an intermediate-scale (1.05 m length and 0.1 m diameter) stainless steel column. This column was packed with silica sand and instrumented with 10 gas sampling probes, 10 water sampling probes, 10 tensiometers, 10 gas ports, and 10 sets of TDR (Time Domain Reflectometry) probes. Key questions addressed by this research were 1) is mass transfer of PCE between liquid and gas phases rate limited? 2) can hysteretic hydraulic properties be neglected in describing transport of dissolved PCE through the column? 3) is the transport behavior of PCE independent of initial flow (or water content) conditions? and 4) can a simple steady-state model be used to simulate PCE transport under transient flow conditions?

Key words: vadose zone, transport, tetrachloroethene, scale.

Poster presentation.

38 • ADSORPTION OF ORGANIC POLLUTANT MOLECULES TO MINERAL SURFACES

N.E. Takach and K. Meredith, Department of Chemistry, University of Tulsa, Tulsa, OK, 74104

A preliminary investigation was conducted on the suitability of the dynamic Wilhelmy plate technique for examining the adsorption of different classes of organic pollutant molecules to the surfaces of mineral thin sections. Plates (thin sections) made both from marble and from quartzite were examined and 1,4-dinitrobenzene represented the first class of pollutant studied: nitroaromatics. Plates of each mineral type were completely immersed in toluene solutions of 1,4-dinitrobenzene for varying periods of time before they were passed into and out of aqueous phases during the Wilhelmy experiments. Magnitudes and changes in adhesion tensions were used to quantify the strength and persistence of adsorption.

Key words: nitroaromatics, adsorption, mineral surfaces, organic pollutants, Wilhelmy technique.

Poster presentation.

39 • OPTIMIZING TNT DESTRUCTION IN CONTAMINATED WATER AND SOIL BY FENTON OXIDATION

M. Arienzo, S.D. Comfort, P.J. Shea, and Z.M. Li, Department of Agronomy, University of Nebraska, Lincoln, NE, 68583-0915

The Fenton reagent (H₂O₂ and Fe²⁺) represents one of the simplest and most effective oxidation technologies available for remediating munitions-contaminated soil and water. Previous research on Fenton oxidation using FeSO₄ and H₂O₂ has shown that destruction of recalcitrant organics is optimum at pH 3.0, but can also be efficient at higher pH in the presence of iron-complexing ligands. To improve the process of TNT destruction in water, ferrous oxalate (FeOx) was substituted for FeSO₄ and used in combination with H₂O₂ to initiate Fenton oxidation. The effects of FeOx concentration and pH were determined. TNT destruction time was 20 min to 2 h, depending on the amount of iron present. These high destruction rates may be explained in part by the continuous source of Fe²⁺ provided by the iron (II)-oxalate. Adjusting solution pH had little effect on reaction kinetics. This may be due to an acidifying effect of FeOx + H₂O₂ on the TNT solution, since pH decreased to 3.0 within minutes of initiating the reaction. The effects of FeOx + H₂O₂ in TNT-contaminated soil slurries will be reported. Preliminary results indicate that use of FeOx may increase the efficiency of TNT destruction in contaminated water and soil.

Key words: trinitrotoluene, Fenton oxidation, remediation.

Poster presentation.

40 • FENTON OXIDATION OF TNT IN SOIL SLURRIES AS INFLUENCED BY TEMPERATURE, DISSOLVED ORGANIC MATTER, AND CLAY MINERALS

Z.M. Li¹, P.J. Shea¹, S.D. Comfort¹, T.C. Zhang², and L.E. Erickson³, ¹Department of Agronomy, University of Nebraska, Lincoln, NE, 68583-0915, ²Department of Civil Engineering, University of Nebraska, Omaha, NE, 68182-0178, and ³Department of Chemical Engineering, Kansas State University, Manhattan, KS, 66506-2502

TNT-contaminated soil and water is an environmental problem at sites where munitions were formerly manufactured, stored, or demilitarized. Our previous research demonstrated that Fenton oxidation effectively destroyed TNT in aqueous extracts of contaminated soil. However, direct application of the Fenton technique to destroy TNT in a soil slurry system would be more efficient and likely more cost-effective. Experiments were conducted to determine Fenton oxidation of TNT in soil slurries. The effects of temperature, dissolved organic matter (DOM), and clay minerals on oxidation efficiency were also determined. Results indicate that Fenton oxidation can effectively destroy TNT in a soil slurry containing 4,875 mg TNT kg^-1 (1:5 w/v soil:H₂O); this process was more efficient at 45ºC than 23ºC. DOM (humic and fulvic acids) had little effect on the total amount of TNT destroyed within 24 h, although a possible catalytic effect of fulvic acid was observed. Montmorillonite and kaolinite differed in their effects on TNT oxidation. Adding a small amount of montmorillonite (0.1-1% w/v) appeared to catalyze TNT destruction in solution, but as the amount of clay was increased (>1% w/v), adsorption of TNT slowed the process. Kaolinite exhibited minimal adsorption of TNT, but slowed TNT oxidation, possibly by quenching reactive free radicals at the mineral surface. Data were fitted to a two-compartment model to predict TNT destruction by Fenton oxidation in soil slurries.

Key words: trinitrotoluene, Fenton oxidation, dissolved organic matter, clay minerals, remediation.

Poster presentation.

41 • SIMULATION OF WASTE-GENERATING CHARACTERISTICS DURING START--UP OF A REACTOR NETWORK UNDER NONISOTHERMAL CONDITIONS

B.B. Patel and L.T. Fan, Department of Chemical Engineering, Kansas State University, Manhattan, KS, 66506

During start-up of a large-scale reactor network, a large amount of an off-spec product is often generated; such a product does not meet the product specifications and thus should be regarded as waste to be treated or reprocessed. Moreover, if a hazardous or toxic component is contained in the product, its accumulation during start-up poses environmental or health risk. Naturally, it is highly desirable that the generation and accumulation of the off-spec product be minimized. To devise an optimal strategy or strategies for accomplishing this requires understanding of the process network's transient behavior for various modes of start-up.

For illustration, the transient and waste-generating characteristics during start-up of a system comprising three continuous-stirred tank reactors connected in series are examined in the present study. Four modes of start-up are considered under nonisothermal conditions involving several simultaneous and/or sequential chemical reactions of different orders.

Key words: start-up, reactor network, hazardous waste, off-spec product.

Poster presentation.

42 • CADMIUM, COPPER, AND ZINC ACCUMULATION IN TRANSGENIC AND NON-TRANSGENIC TOBACCO PLANTS

N.A. Yancey¹, J.E. McLean¹, R.C. Sims¹, P. Kotrba², M. Mackova², T. Macek³, W. Scouten⁴, A Singh-Cundy⁵, and M. Truksa⁶, ¹Utah Water Research Laboratory, Utah State University, Logan, UT, 84322-8200, ²Department of Biochemistry and Microbiology, Faculty of Food and Biochemical Technology, Institute of Chemical Technology, Technicka 3, CZ-166 28 Prague 6, CZECH REPUBLIC, ³Department of Plant Tissue Cultures, Institute of Organic Chemistry and Biochemistry, Academy of Sciences of the Czech Republic, Flemingovo n. 2, CZ-166 10 Prague 6, CZECH REPUBLIC, ⁴Biotechnology, Utah State University, Logan, UT, 84322-4700, ⁵Biology, Utah State University, Logan, UT, 84322-5305, and ⁶Department of Plant Physiology and Botany, Gregor Mendel University of Agriculture, Zemedelska 1, 61300 Brno, CZECH REPUBLIC

Phytoremediation or the use of plants to ameliorate sites contaminated with inorganic and organic wastes is an increasingly interesting area of research. Plants growing near mining sites or smelter operations or near naturally-occurring metal-containing soils have developed rare characteristics that allow these plants to either exclude metal from plant tissue or absorb large amounts of metals into the plant biomass. Plants that accumulate zinc, copper, or cadmium in levels exceeding 10,000, 1,000, or 100 mg metal/kg biomass, respectively, in the above-the-ground portion of the plant are considered to be hyperaccumulators. By growing these hyperaccumulators on metal-contaminated sites, the metals can be transferred from the soil into plant tissue, thus concentrating metals into a form that is easily disposed of. Many of these naturally-occurring hyperaccumulators, however, produce very little biomass and thus are not suitable for use in phytoremediation technologies.

Recent development in biotechnology and genetic engineering have found certain proteins in animals, yeasts, and fungi called metallothioneins (MTs) which bind a variety of metals very effectively. Through genetic engineering, molecular coding techniques were used to design unique gene constructs encoding proteins with high affinity for certain metals. These constructs are being used to transform tobacco plants with a commercially-available plasmid. Preliminary research has investigated the metal tolerance and accumulation of the bacteria E. coli as a host for the MTs. Results indicated an increased tolerance to metal rich environments by bacteria containing the MT protein. Transgenic tobacco seeds germinated on media spiked with zinc also showed increased tolerance to the zinc when compared to non-transgenic tobacco seedlings.

Accumulation of cadmium, copper, and zinc by transgenic and non-transgenic tobacco plants in hydroponics is being investigated. Tobacco plants have played important roles in genetic engineering techniques as they lend themselves well to genetic research. In addition, the plants produce significant amounts of biomass which enhances their usefulness in phytoremediation technologies. Further optimization studies will be conducted to investigate the accumulation of metals from soils contaminated with cadmium, copper, and zinc by transgenic and non-transgenic tobacco plants.

Key words: phytoremediation, hyperaccumulator, tobacco, metallothionein.

Poster presentation.

43 • IDENTIFYING GROUND WATER THREATS FROM IMPROPERLY ABANDONED BOREHOLES

R.F. Kubichek¹, J.C. Cupal², S. Choi, B. Qiu, J.D. Burke, and M. Morris, Electrical Engineering Department, University of Wyoming, Laramie, WY, 82071-3295, e-mail: ¹kubichek@uwyo.edu, ²jcupal@uwyo.edu

Plugged and abandoned oil and gas wells represent a little understood threat to fresh-water aquifers. Improperly plugged boreholes provide an easy path for fluid communication between subsurface formations. In such cases, an aquifer can become contaminated with oil, gas, or dissolved solids such as selenium and salt from adjacent rock layers. Proper abandonment procedures dictate installation of cement plugs within the borehole to seal off fresh-water aquifers and protect water quality. Unfortunately, following these procedures is quite expensive, and many wells may be closed illegally using a single cement plug at the surface. Only a small percentage of wells are closed under the supervision of federal or local inspectors, and it is currently impossible to estimate what fraction of abandoned wells require mitigation. Environmental and law enforcement agencies can verify the proper placement of downhole cement plugs only by re-drilling the well-an expensive and risky operation.

This paper describes a research effort to develop acoustical methods for sensing plug locations. The proposed technique uses sonic pulse propagation along the casing or borehole wall, combined with computer modeling and advanced signal processing techniques, to determine the depth of coherent cement plugs in an abandoned well. Preliminary results using a full-scale horizontal borehole mockup are presented, including hardware test setups, modeling and data analysis, and signal processing results.

Key words: plug detection, well abandonment, aquifer.

Poster presentation.

44 • CONTAMINANTS MINERALIZATION USING ACTIVATED CARBON-AOPs SYSTEM

P. Lo and A. Hong, Department of Civil and Environmental Engineering, University of Utah, Salt Lake City, UT, 84112

Activated carbon adsorption is widely used in contaminants removal application. Both granular activated carbon (GAC) and powered activated carbon (PAC) are used for removal of a wide variety of organic compounds from contaminated ground water, industrial waste streams, and biological effluents. It is a developed technology that is able to remove soluble organic compounds and toxic substances. Typical activated carbon contactors require the removal of spent carbon, regeneration, and/or addition of new carbon. The procedure may be cumbersome and less economical. This paper will focus on the regeneration of spent activated carbon using Advanced Oxidation Processes (AOPs). We have employed AOPs involving chemical oxidants, ozone (O₃), and hydrogen peroxide (H₂O₂) to mineralize contaminants that are adsorbed and accumulated on the activated carbon surface. Results have shown that AOPs are a viable technology for the regeneration of activated carbon. The technology is capable of extending the service lifetime of activated carbon, hence increasing the economic value.

Key words: activated carbon, adsorption, AOPs, regeneration.

Poster presentation.

45 • KINETICS AND MECHANISM OF DEGRADATION OF HAZARDOUS CONTAMINANTS USING OZONE AND HYDROGEN PEROXIDE

V. Capps and A. Hong, Department of Civil and Environmental Engineering, University of Utah, Salt Lake City, UT, 84112

Treatment of hazardous contaminants utilizing ozone in the presence of hydrogen peroxide has shown great potential for complete destruction of recalcitrant compounds. However, the kinetics and mechanisms of degradation are often complex and involve a series of free radical reactions. In an attempt to optimize the ozone/peroxide system for use in the remediation process, test contaminants are used to model relevant system parameters, such as pH, contaminant concentration, and ozone and peroxide dosage. This paper will focus on the use of test contaminants to verify a proposed kinetic model for the ozone/peroxide system.

Key words: AOPs, kinetics, mechanism, contaminant, remediation.

Poster presentation.

46 • METABOLISM OF TNT ASSOCIATED WITH ROOTS OF HIGHER PLANTS

L.C. Davis and N.C. Chou, Department of Biochemistry, Kansas State University, Manhattan, KS, 66506

Trinitrotoluene (TNT) is a common contaminant in ordnance facilities throughout the central U.S. Former disposal practices led to accumulations of relatively high concentrations of this low solubility compound. The contamination is generally widely dispersed and in some locations it is leaching toward ground water. Recent reports (c.f. van Beelen and Burris, 1995, Environ Toxicol and Chem 14:2115-2123) have indicated that nitroreductase enzymes found in sediments of streams or ponds may reduce TNT to different aminodinitrotoluenes and/or further reduced materials. The same or similar reductase activity has been reported to be associated with aquatic plants (Schnoor et al., 1995, Environ Sci Technol 29:318A-323A).

We conducted a survey of several genera of higher plants growing hydroponically to determine whether nitroreductase activity might be associated with the roots of these plants. The main analytical tool has been HPLC to monitor disappearance of TNT and appearance of metabolites. A Hamilton PRP-1 column was used with 65% acetonitrile, 1 mM KOH. Scanned spectra were obtained for some of the eluted peaks but it proved difficult to reliably identify compounds by their uV spectral characteristics.

Most plants that we tested showed relatively similar rates of TNT disappearance when expressed on a root fresh weight basis. Monocots examined included sorghum, maize, papyrus, and cattails. Dicots included soybean, alfalfa, sunflower, pumpkin, tomato, amaranthus, poplar, and tamarix.

When intact plants were incubated in a solution of 50 mg/l TNT plus 1 mM phosphate buffer pH 6.8, at a ratio of near 1 g root tissue per 50 ml solution, there was nearly complete loss of TNT within 24 hours. Initially a more polar metabolite, believed to be aminodinitrotoluene, appeared. At later times a still more polar metabolite peak was observed, at the same time that the heights of all peaks diminished. Activity was decreased several fold by separating roots from the plant and even more by freezing roots overnight.

During the short exposure times studied here, a few days, plants were not obviously injured when phosphate buffer was provided. Tamarix was treated repeatedly with a lower concentration of TNT (10 mg/l) without apparent injury. In contrast, a water plant, milfoil, was rapidly killed at this same concentration and disintegrated within 2 days. An earlier study with yellow nutsedge (Palazzo and Leggett, J Environ Qual 15:49-52) found severe inhibition of plant growth at TNT concentrations as low as 5 mg/l, but in that case the ratio of root to solution was very small, and the authors replenished the TNT after 3 weeks. In that study high concentrations of metabolites were found within the root systems (including rhizomes and tubers) of the plants after 42 days. We did not examine plants for accumulation of metabolites, because no isotopic tracers were used and the accumulation time was relatively short. Disappearance of TNT and metabolites from solution suggests that there was in fact uptake into the plants.

Key words: bioremediation, trinitrotoluene, water, plants.

Poster presentation.

47 • MEASURING CONTAMINANT FLUX THROUGH PLANTS BY FOURIER TRANSFORM INFRARED (FT-IR) SPECTROMETRY

V.D. Makepeace¹, L.C. Davis², J. Dana³, K. Selk², K. Smith³, R.M. Hammaker¹, W.G. Fateley¹, and L.E. Erickson³, Departments of ¹Chemistry, ²Biochemistry, and ³Chemical Engineering, Kansas State University, Manhattan, KS, 66506

Plant-based bioremediation depends on the ability of plants to survive in the presence of contaminants, to metabolize or exclude contaminants, and to provide nutrient supplementation to microbes that can accelerate contaminant degradation. Plants facilitate transport of contaminants by drawing water from soil. Rates of water use may commonly exceed 1 cm per day (100,000 l/ha/day) during the summer. This water usage in turn could lead to intermedia transfer of volatile contaminants and exposure of plants to high concentrations of the contaminants that are relatively nonvolatile and that are also partially excluded by the plant root system.

Fourier transform infrared spectrometry (FT-IR), with a long path length extractive instrument (Gasmet, by Temet Instruments) allows detection of many common volatile materials at levels below 1 ppm (v/v). We examined the movement of common soluble, volatile gasoline constituents through two species of woody plants, hybrid poplars (Populus deltoides x nigra) and salt-cedar (Tamarix parviflora). Both species are rapidly growing, water consumptive, and drought-resistant. In each case 1% deuterated water was used to provide an FT-IR detectable marker for the rate of transpiration through the plants. Contaminants were supplied to the root system in a closed flask with an equilibrated headspace. The top portion of the plants was enclosed in a 78.5 l closed chamber from which air was drawn by a pump through the FT-IR instrument at about 1 l/min. Refrigerated coils condensed water, allowing accumulation of contaminant above the relative water concentration in the chamber. The need to supply CO₂ (from room air) for photosynthesis limited the maximum concentration ratio that could be achieved.

Contaminants tested included benzene, toluene, ethyl benzene, meta-xylene, 1,2,4-trimethyl benzene, cyclohexene, n-pentane, ethyl ether, n-propyl ether, and t-butyl methyl ether. Most aliphatic hydrocarbon constituents of gasoline were not water soluble to sufficiently high concentration for study. A wide range of octanol-water partition coefficients is represented by the series chosen here, from about log K_ow 0.8 to 3.4. According to the work of Briggs et al. (Pestic Sci 13:495-504) these K_ow values span a range of transpiration stream concentration factors (TSCF) from about 0.3 to 0.8, with the highest TSCF for compounds like benzene and toluene.

Ethyl benzene, xylene, and trimethyl benzene (least polar) were often toxic to the plants at the initial concentration of ~1 mM. Other compounds were tolerated at levels up to 2 mM in the aqueous phase surrounding the root system. The three least polar compounds, which also have unfavorable TSCF values, were difficult to detect in the gas phase surrounding the plant tops. Other compounds were detectable at levels related to water usage and TSCF. We conclude that volatile contaminants can move through plants, much like nonvolatile pesticides of varying polarity. Studies of chlorinated hydrocarbons will be reported elsewhere.

Key words: gasoline, Fourier transform infrared spectrometry, bioremediation, ground water, transpiration.

Poster presentation.

48 • EVALUATION OF TOXICITY OF TRICHLOROETHYLENE FOR STERILE-GROWN PLANTS

S.B. Ryu¹, L.C. Davis¹, J. Dana¹, K. Selk¹, and L.E. Erickson², Departments of ¹Biochemistry and ²Chemical Engineering, Kansas State University, Manhattan, KS, 66506

Plants have the potential to remediate a number of toxic compounds but there is very little literature on the ability of plants to tolerate high levels of common solvents. If plants are to be used for clean-up of compounds such as trichloroethylene (TCE), the first requirement is that they be able to survive in its presence. Studies of the transport of a number of compounds through plants indicate that they can tolerate exposure of their root systems to a 1 mM aqueous concentration. Compounds that were tolerated for at least 24 hours by one or more species included trichloroethylene, trichloroethane, chloroform, dichloromethane, and carbon tetrachloride. These studies were done with relatively large plants of alfalfa (Medicago sativa), hybrid poplars (Populus deltiodes x nigra), and saltcedars (Tamarix parviflora).

Studies were done to measure the damage induced by exposure of entire plants to comparable concentrations of a representative contaminant. Soybean seedlings were exposed to levels of TCE up to 2 mM in the gas phase surrounding the entire plant. Severe damage was evident at 0.5 mM as shown by electrolyte leakage. Plants were killed at higher concentrations.

Tobacco plants, regenerated from callus, and growing aseptically on agar medium, were tested with levels of TCE ranging up to 100 mM. No visual evidence of damage was observed and the plants remained healthy for a week. There was no significant decrease of TCE levels in the gas phase between two and seven days, suggesting that the plants did not rapidly metabolize TCE. However, observable metabolism is highly dependent on mass/volume ratios unless isotopic tracers are used. With intact plants in sealed containers, depletion of CO₂ becomes a problem unless there is a regulated source of CO₂ or large volume containers are used.

Key words: plants, trichloroethylene, toxicity, bioremediation.

Poster presentation.

49 • MOBILIZATION AND TRANSPORT OF DEPLETED URANIUM FROM SURFACE SYSTEMS

P.N. Graham and C.L. Tiller, Environmental Engineering, Georgia Institute of Technology, Atlanta, GA, 30332-0512

Depleted uranium (DU) is a by-product of uranium enrichment for nuclear power generation and is used extensively in military applications. As a result of the testing of DU penetrators at U.S. Army sites such as Yuma Proving Grounds and Aberdeen Proving Grounds, DU can potentially be distributed in the environment and contaminate surface systems. Since DU is a toxic heavy metal, having the potential for affecting human health and ecosystems, there is a need to understand and predict the transport and fate of DU in the environment. A model combining chemical speciation and physical transport calculations was developed to provide a tool for assessing the potential for long-range transport of DU through runoff and surface waters. The mobilization of DU from a site of surface contamination is initially controlled by the corrosive oxidation of the elemental uranium. In oxygenated water, oxidation occurs rapidly and is unlikely to limit transport, except perhaps in arid environments. In reduced waters, however, initial mobilization of DU can be the rate-limiting step. In a stream modeled under a variety of conditions of pH, redox potential, and concentrations of dissolved inorganic carbon, the rate and extent of transport of DU was largely determined by whether it existed primarily as insoluble uraninite (UO_2(s)) or as mobile uranyl hydroxides and uranyl carbonates. The potential for transport of DU is also significantly affected by the availability and characteristics of sorbent phases such as clay minerals, iron oxyhydroxides, and organic matter. For example, a model of the potential for transport of DU during infiltration suggests that the extent of transport can vary by as much as an order of magnitude depending on soil characteristics.

Key words: depleted uranium, transport, surface water.

Poster presentation.

50 • RESEARCH, DEVELOPMENT, AND DEMONSTRATION (RD&D) PERMIT PROCESS FOR THE TREATMENT OF RADIOACTIVE/HAZARDOUS WASTE

B.I. Krogfuss¹, F.A. Walker², and L.C. Weers³, ¹Kaiser-Hill, U.S. Department of Energy, P.O. Box 928, Golden, CO, 80402-0928, ²RMRS, U.S. DOE, P.O. Box 928, Golden, CO, 80402-0928, and ³Colorado Department of Public Health and Environment, HWMWD-SWIM-B2, 4300 Cherry Creek Drive South, Denver, CO, 80222-1530

Rocky Flats Environmental Technology Site (RFETS) obtained an RD&D permit for microencapsulation of mixed waste. RD&D permits require slightly different permitting strategy than obtaining a full RCRA Part B permit. This paper outlines permitting strategies and streamlining strategies for RD&D permits.

Key words: RD&D permit, RCRA, polymer microencapsulation, radioactive waste, hazardous waste, nuclear waste storage, mixed waste, LDR treatment.

Poster presentation.

51 • EFFECTS OF FERTILIZATION RATES ON PHYTOREMEDIATION OF PETROLEUM-CONTAMINATED SOILS

S.L. Lewis¹, M.K. Banks¹, and A.P. Schwab², Departments of ¹Civil Engineering and ²Agronomy, Kansas State University, Manhattan, KS, 66506

In order to determine the optimal nutrient levels for maximum petroleum degradation using phytoremediation, four different fertilization rates will be tested in a greenhouse experiment using a C4 plant, bermuda grass (Cynodon dactylon), a C3 plant, tall fescue (Festuca arundinacea), and an unplanted control. Fertilization rates will be based on the soil C:N ratio for plant requirements as well as microbial needs. This study will indicate the importance of nutrient availability for maximizing phytoremediation rates of petroleum-contaminated soils.

Key words: phytoremediation, nutrients requirements, fertilization rates.

Poster presentation.

52 • AN ASSESSMENT OF MICROBIAL CHANGES DURING PHYTOREMEDIATION

S.D. Pekarek, J. Keller, M.K. Banks, and A.P. Schwab, Kansas State University, Manhattan, KS, 66506

Phytoremediation is the use of plants to enhance bioremediation of polluted soil. Microbial degradation is an important dissipation mechanism during this process. Data from a greenhouse study designed to evaluate changes in microbial numbers and communities will be presented. Results from this study will help assess the microbial contribution to phytoremediation of petroleum-contaminated soil.

Key words: phytoremediation, microorganisms, petroleum contamination, soil, degradation.

Poster presentation.

53 • DETERMINATION OF TOTAL PETROLEUM HYDROCARBONS IN CONTAMINATED SOIL

J. Su and A.P. Schwab, Department of Agronomy, Kansas State University, Manhattan, KS, 66506

Soxhlet extraction is the standard method in the determination of total petroleum hydrocarbons (TPH) in soil, and the soil is kept at field moisture to avoid losses of volatile constituents. However, the soil remains static in the soxhlet extractor which limits the exposure of soil surfaces to the solvent. Subsampling errors increase in moist soils because they are difficult to homogenize, and hydrophobic solvents lose efficiency in moist soils even when drying agents such as sodium sulfate are employed. We compared the efficiency of TPH extraction using shaking versus soxhlet, field moist versus dry soil, and three different solvents. Extraction of moist soils by either shaking or soxhlet yield slightly lower TPH concentrations and much higher variability compared to extraction of dry soil. Soxhlet and shaking resulted in the same soil TPH concentrations if the shaking involved three or more successive extractions with clean solvent. Shaking moist soils with hydrophilic solvents (e.g., acetone) was more efficient than hydrophobic solvents (e.g., methylene chloride) for the first extraction, but the TPH removed after three extractions was independent of solvent. We conclude that shaking dry soils yields the same concentrations as soxhlet extraction but many more soils can be processed using shaking.

Key words: total petroleum hydrocarbons (TPH), soil, shaking soxhlet.

Poster presentation.

54 • EFFECT OF PLANT EXUDATES ON THE BIOREMEDIATION OF SYNTHETIC DIESEL FUEL

K. Rathbone, A.P. Schwab, and M.K. Banks, Kansas State University, Manhattan, KS, 66506

Increased root surface area and plant exudates output are implied to promote microbial activity in the rhizosphere. Different species of sorghum are being studied based on their exudate production to increase bioremediation of synthetic diesel fuel. Four types of sorghum with differing amounts of exudate release were planted in a sandy loam soil contaminated with 0.25% synthetic diesel fuel. Three time periods were used for take down of samples; 5 leaf stage, flowering, and maturation. Microbial activity, plant uptake, and the soil degradation of diesel fuel will be presented and discussed. Results from this study will help assess important root characteristics for plants during phytoremediation.

Key words: bioremediation, exudates, rhizosphere, diesel fuel, plants.

Poster presentation.

55 • THE IMPACT OF VEGETATION ON HEAVY METAL MOVEMENT

D. Zhu¹, A.P. Schwab¹, M.K. Banks², and E.X. Wang², ¹Department of Agronomy, and ²Department of Civil Engineering, Kansas State University, Manhattan, KS, 66502

The establishment of vegetation in mining areas is a primary method to minimize metal contamination through wind erosion, runoff, and infiltration. Plants may decrease heavy metal leaching by plant uptake, stimulating microbial immobilization of metals in the rhizosphere, and decreasing water flow. However, organic compounds, especially organic acids exuded by plants and microbes, may increase heavy metal solubility. Also, channels created by the plant root system may greatly increase metal movement through preferential flow. We evaluated the effects of a warm-season grass and cool-season grass on the leaching of Zn, Cd, and Pb from mine tailings. The leaching experiment was conducted under unsaturated conditions using multilayered columns. Metals leached were monitored for 10 months, and total mass of leached metal was calculated. The subsoil in the columns will be extracted and the heavy metals in the plant biomass will be analyzed after the leaching experiment is concluded. These lab results will provide us with important information concerning the use of vegetation for mining site remediation.

Key words: heavy metal, phytoremediation, leaching, column, ground water.

Poster presentation.

56 • THE EFFECT OF FLUCTUATING WATER LEVELS ON BIODEGRADATION OF NAPLS IN SOIL

L. Schuckman, M.K. Banks, and L.N. Reddi, Civil Engineering Department, Kansas State University, Manhattan, KS, 66506

Multi-layer soil columns were constructed and contaminated with NAPLs to determine optimal bioremediation strategies for the remediation of discontinuous contaminated soil. A detailed examination of these columns will yield information about the soil physical and chemical properties, zone of accumulation, microbial characteristics, flow of nutrients, and biodegradation of target compounds.

Key words: nonaqueous phase liquids, bioremediation, ground water, soil.

Poster presentation.

57 • BIODEGRADATION KINETICS OF CARBON TETRACHLORIDE, PERCHLOROETHYLENE, AND 1,1,1-TRICHLOROETHANE WHEN PRESENT IN MIXTURES

D.T. Adamson and G.F. Parkin, 125 Engineering Research Facility, The University of Iowa, Iowa City, IA, 52242

The effect of mixtures of chlorinated aliphatics on biotransformation of the individual compound is being investigated using methanogenic enrichment cultures. Carbon tetrachloride (CT), perchloroethylene (PCE), and 1,1,1-trichloroethane (TCA) are known to be degraded anaerobically through reductive dechlorination. Cultures are fed acetate as a carbon and energy source and then exposed to various combinations and concentrations of these compounds. Disappearance of parent compounds and appearance of transformation products is measured using gas chromatography. Biodegradation kinetics are determined using pseudo-first-order rate expression ("biomass-corrected"). Rate constants for the individual compounds when present alone and in mixtures are compared in order to assess the relative effects of each. Methane production and acetate utilization are also measured to determine the impact of exposure to mixtures on methanogenesis. Initial results indicate that the presence of a mixture significantly reduces the rate of degradation of the individual compound. With unacclimated cultures, CT is degraded most rapidly, followed by TCA and PCE. The presence of the mixture reduces acetate utilization and methane production significantly when compared with exposure to an individual compound. Attempts are also being made to develop acclimated enrichment cultures by initially adding low concentrations of the compounds and gradually increasing the concentration over time. Rate constants obtained from the acclimated culture will then be compared to those for the unacclimated culture. These results should be helpful in developing remediation strategies for sites contaminated with mixtures of chlorinated compounds.

Key words: bioremediation, mixtures, chlorinated aliphatics.

Poster presentation.

58 • SEQUENTIAL TRANSFORMATION OF CARBON TETRACHLORIDE, PERCHLOROETHYLENE, AND 1,1,1-TRICHLOROETHANE USING METHANOGENIC AND METHANOTROPHIC CONDITIONS

S.J. Christ and G.F. Parkin, 125 Engineering Research Facility The University of Iowa, Iowa City, IA, 52242

Sequential, methanogenic-methanotrophic biofilm reactors are being employed to study the biodegradation of carbon tetrachloride (CT), perchloroethylene (PCE), and 1,1,1-trichloroethane (TCA). Two sequential, glass-bead reactor systems were seeded with an acetate enrichment culture (first column) and a methanotrophic enrichment culture (second) column. One system is fed PCE while the other is fed a mixture of CT, PCE, and TCA. A third sequential reactor system consists of an anaerobic column filled with steel wool and seeded with an acetate enrichment culture, followed by a glass-bead column seeded with a methanotrophic enrichment culture. This column is fed a mixture of CT, PCE, and TCE. It is hypothesized that the methanogens in the first reactor will transform (by reductive dechlorination) the highly chlorinated CT, PCE, and TCA into lesser chlorinated compounds such as dichIoromethane, dichloroethylene, and dichloroethane, which will in turn be mineralized by the methanotrophs in the second column. Acetate will be fed to the glass-bead columns while the H₂ produced from the anaerobic corrosion of the Fe⁰ in the steel-wool column will serve as the energy source for the methanogens. Influent concentrations of these compounds will be gradually increased over time to investigate the capacity of these systems to degrade, and hopefully mineralize, the target compounds and their expected metabolites (e.g., chloroform and dichloromethane from CT; trichloroethylene from PCE; 1,1-dichloroethane from TCE; etc.). Initial concentration is 1 mM for each compound.

Key words: sequential bioremediation, methanogens, methanotrophs, chlorinated aliphatics.

Poster presentation.

59 • NICKEL UPTAKE BY THE HYPERACCUMULATOR STREPTHANTHUS POLYGALOIDES GROWN ON SERPENTINE AND CALCAREOUS SOILS

J.L. Cramer and P.R. Grossl, Department of Plants, Soils, and Biometeorology, Utah State University, Logan, UT, 84322-4820

The need to discover less costly means of remediating metal-contaminated land has led to an ever-growing interest in phytoremediation. We are growing the nickel hyperaccumulator Strepthanthus polygaloides in contaminated soils to determine the amount of nickel accumulated in the roots, shoots, and leaves. The two soils used in this study are a serpentine soil from California and a calcareous soil from Utah that was spiked with 3,000 ppm nickel. No nickel was added to the serpentine soil, which has an inherent total nickel concentration of approximately 3,000 ppm. Based on previous studies, it is predicted that Strepthanthus polygaloides should accumulate nickel to a concentration of 9,000 ppm in its leaves. This is nine times the level required for recognition as a hyperaccumulator. To the soil we will add either nitrate (NO₃^--N) or ammonia (NH₄⁺-N) to examine if these amendments will enhance nickel accumulation beyond predicted values. With this information new techniques of remediating metal-contaminated land using Strepthanthus polygaloides can be developed.

Key words: strepthanthus polygaloides, hyperaccumulator, nickel.

Poster presentation.

60 • MINERALIZATION OF PENTACHLOROPHENOL IN SOIL BY WHITE-ROT FUNGI IN THE PRESENCE OF SURFACTANTS

R.A. Doughten¹, W.P. Inskeep¹, and C.G. Johnston², ¹Department of Plant, Soil, and Environmental Sciences, Montana State University, Bozeman, MT, 59717, and ²Mycotech Corporation, Butte, MT, 59702

Pentachlorophenol is a common and persistent contaminant of soils at wood-preserving facilities. White-rot fungi have been identified as possessing enzyme systems capable of degrading PCP; however, degradation may be limited by contaminant sorption to soils. Surfactants can be used to minimize this limitation by increasing the bioavailability of sorbed hydrophobic molecules in soils. A non-Phanerochaete white-rot fungi, identified as Mycotech strain "F600," was evaluated for its ability to degrade ¹⁴C-PCP applied to a sterile agricultural soil amended with five surfactants (lignosulfonic acid, sodium salt; lignosulfonic acid, sodium salt, acetate; hydroxypropyl-b-cyclodextrin; Tween 80; Triton X-100). Each surfactant was applied to the contaminated soil at 25 mg g^-1 soil, concentrations similar to soil organic matter content. Mineralization was measured as the amount of ¹⁴CO₂ recovered from soil columns flushed with air; fungal activity was estimated from respiration rates measured by titrating trap solutions with standardized acid. In four weeks, 36% of the applied PCP was mineralized in the Tween 80 treatment whereas 23% of the applied PCP was mineralized in the non-surfactant control. In addition, the initial mineralization rate in the presence of Tween 80 was significantly higher than other treatments. The other four surfactants decreased PCP mineralization or were similar to the control. Fungal activity (total respiration) over the same time period was not significantly different among surfactant treatments. The use of surfactants, such as Tween 80, in combination with white-rot fungi may represent a strategy for the bioremediation of residual PCP in contaminated soils.

Key words: surfactants, degradation, white-rot fungi, pentachlorophenol.

Poster presentation.

61 • RELATIONSHIP BETWEEN BIOLOGICAL AND CHEMICAL GROUND WATER DATA AT A URANIUM MILL TAILINGS SITE

H.A. Noskin¹, K. Choudhury², and L.L. Barton², ¹Los Alamos National Laboratory, Los Alamos NM, 87545, and ²Department of Biology, University of New Mexico, Albuquerque, NM, 87131-1091

Analysis of chemical and bacteriological data obtained from ground water studies from the Gunnison, Colorado, uranium mill tailings site was performed in three parts: (i) analysis of bacteriological data from pristine wells and from wells in the plume region; (ii) analysis of chemical or environmental data from these well sites; and (iii) modeling of the ground water data with the bacteriological data. Correlations and significance levels were determined using SAS analysis. Of the 66 environmental variables for these wells, 24 were useful to provide differences between the wells. The relationships among all the variables were clustered as groups, and pair comparisons of the variables for positive and negative correlations were performed. Information will be presented to indicate the method most useful to determine correlations between environmental and bacterial characterization of ground water.

Key words: ground water quality, uranium sites, environmental correlations.

Poster presentation.

62 • APPLICATION OF BIOSENSORS BASED ON NATIVE FLUORESCENCE

D.W. Morrison¹, L.L. Barton¹, R.F. Cifuentes², and W.C. Lindemann², ¹Department of Biology, University of New Mexico, Albuquerque, NM, 87131-1091, and ²Department of Agronomy, New Mexico State University, Las Cruces, NM, 88003-8001

The monitoring of bacteria in the environment is often required to assess specific bioremediation processes. An approach that we have employed is to use fluorescence to detect molecules that serve as signatures for specific bacteria and to employ dyes for staining of bacteria present. The data presented here indicate that fluorescence can be used in the quantitation of methane-producing bacteria and sulfate-reducing bacteria by detecting specific molecules for each of these physiological types of bacteria. Additionally, chelator molecules specific for metals that are produced by various types of bacteria can also be measured by fluorescence. This would be important to predict in situ activities of these bacteria. Finally, selective strains discriminate between live and dead bacteria through the type of fluorescence produced. Each of these molecules has a specific wavelength for excitation and emission, thereby providing a basis for identifying bacteria or bacterial activities in the environment.

Key words: fluorescence, biosensor, bacterial identification.

Poster presentation.

63 • STRATIFICATION OF SOIL CHEMICAL PROPERTIES IN REVEGETATED CHAT

G.M. Pierzynski¹, J. Xie¹, and M.R. Norland², ¹Department of Agronomy, Kansas State University, Manhattan, KS, 66506, and ²U.S. Bureau of Mines, 5629 Minnehaha Ave. South, Minneapolis, MN, 55417

Vegetative remediation of large areas of zinc/lead mine spoils is an increasingly popular option given the economic restraints that are often associated with remediation activities. Little is known about the long-term effects of vegetation on the stratification of soil chemical properties in revegetated chat. A field study was initiated in 1990 comparing various sources and rates of organic wastes as soil amendments for revegetating chat. Zinc phytotoxicity and poor soil physical properties were the most limiting factors in establishing plant growth. The use of cattle manure at 90 Mg/ha was the most successful amendment with no growth occurring on unamended chat. Soil samples were collected from 0 to 7.5 cm by 2.5 cm increments in 1996 from plots receiving 90 Mg/ha cattle manure and from the control plots. Total metal analysis of these samples indicated that Zn and Cd concentrations were significantly lower at 0-2.5 cm for vegetated plots compared to unvegetated plots with the opposite being true for Mn. At this same depth there were no significant differences in metal concentrations for Cr, Cu, Fe, Ni, and Pb. Generally, vegetation had no effect on metal concentrations below 2.5 cm with the exception of Pb which was significantly higher with vegetation compared to no vegetation at 2.5-5.0 and 5.0-7.5 cm. Additional samples will be collected to a great depth and analyzed for organic C, pH, and total and bioavailable metal concentrations

Key words: zinc, lead, vegetation, remediation, mining.

Poster presentation.

64 • PHOTOCATALYTIC REDUCTIVE DEHALOGENATION OF TRICHLOROETHYLENE AND CARBON TETRACHLORIDE USING OPTICAL FIBERS COATED WITH TiO₂-CoTSP

S.B. Gogosha¹, R.G. Arnold¹, and E.A. Betterton², ¹Department of Chemical and Environmental Engineering, University of Arizona, Tucson, AZ, 85721, and ²Department of Atmospheric Sciences, University of Arizona, Tucson, AZ, 85721

Heterogeneous photocatalysis on the surface of metal-oxide semiconductors such as TiO₂ has been widely used for the decomposition of chlorinated organics in water. The hybrid semiconductor-macrocycle catalyst TiO₂-cobalt tetrasulfophthalocyanine (TiO₂-CoTSP) promotes the reductive dehalogenation of bromoform (CHBr₃) under anaerobic conditions. In previous work, coated TiO₂ particles were suspended in the reactors. The nature of these suspensions prevented light from penetrating into the reaction mixture and decreased the effectiveness of the system. Also, removal of the particles from the water was difficult, a liability for potential field applications. Attachment of TiO₂-CoTSP to the surface of an optical fiber is proposed as a solution to these problems. This research explores the feasibility of using a coated optical fiber to provide both the light source to induce the photocatalytic properties of the TiO₂-CoTSP and a surface to support the photocatalyst. Different techniques for coating the fiber with TiO₂ and attaching CoTSP were studied. Reductive dehalogenation of TCE and carbon tetrachloride was carried out using both the modified and unmodified fibers. The quantum efficiencies of the two systems were compared to each other and to published data.

Key words: reductive dehalogenation, remediation, aquifer, optical fiber, titanium dioxide.

Poster presentation.

65 • STRATEGIES FOR CONDITIONING OF SPENT RADIATION SOURCES IN CUBA

J.C. Benitez, N. Garcia, M. Salgado, and L. Jova, Center for Radiation Protection and Hygiene, 14 No. 308, Miramrar, P.O. Box 6195, Ciudad Habana, CUBA

Responsibility for the development of a national strategy for the management of radioactive wastes in Cuba lies in the Center for Radiation Protection and Hygiene. The current research program includes (1) improvement of radioactive waste management in Cuba, (2) remodeling of the Cuban RadWaste Treatment Plant, and (3) development and implementation of adequate methods for conditioning spent radiation sources.

This paper describes the main considerations and facts taken into account for the design and implementation of a set of procedures with all technical, administrative, protective, and practical details for conditioning spent radiation sources in Cuba.

Key words: radioactive waste management, spent radiation sources, conditioning.

Poster presentation.

66 • THERMAL TREATMENT OF INDUSTRIAL-PRODUCED ACIDIC METAL CHLORIDE HAZARDOUS WASTE

D. Knappe, Colorado Department of Public Health and Environment, Hazardous Materials and Waste Management Division, 4300 Cherry Creek Drive South, Denver, CO, 80222-1530

A State RCRA Research, Development, and Demonstration (RD&D) permit was prepared for a research facility to the mining, mineral, and chemical industries. The permit specified operating conditions for the thermal treatment of acidic metal chloride waste. The acidic metal chloride waste is produced industrially and is characterized as a hazardous waste under the Colorado Hazardous Waste Regulations. The specific reaction occurring in the thermal reactor involves the pyrohydrolysis of hazardous waste. The pyrohydrolysis reaction utilizes heat, water, and a low amount of oxygen to cause a chemical and physical separation in the waste. Expected byproducts of the reaction include a nonhazardous byproduct and hydrochloric acid. If successful, the pilot-scale plant will be built full-scale at industrial facilities handling acidic metal chloride waste so that the hydrochloric acid can be recycled back into the industrial process. The effectiveness of the thermal treatment system, including the emission control design, and process controls will be evaluated under the conditions and requirements of the State RCRA RD&D permit.

Key words: thermal treatment, chemical and material processing, hazardous waste, RD&D permit, waste minimization.

Poster presentation.

67 • DNA BIOSENSOR FOR MONITORING HYDRAZINE COMPOUNDS

J. Wang, X. Cai, G. Rivas, and M. Flair, Department of Chemistry and Biochemistry, New Mexico State University, Las Cruces, NM, 88003

Nucleic acids offer the environmental chemist a powerful tool in the recognition and monitoring of many important pollutants. This poster will report on a new DNA biosensor for the detection of hydrazine compounds. The sensor relies on monitoring changes in the intrinsic response of the surface-confined DNA resulting from its interaction with hydrazine compounds, and requires no label or indicator. Short reaction times are sufficient for monitoring ppb levels of different hydrazines.

This work was supported by the U.S. DOE through the WERC program.

Key words: hydrazines, DNA, sensor.

Poster presentation.

68 • ASSURING QUALITY MODEL USAGE, EXPERIMENTAL VALIDATION, AND EXTRAPOLATION TO FIELD SITES

J.C. Tracy and V.R. Schaefer, Northern Great Plains Water Resources Research Center, South Dakota State University, Brookings, SD, 57007

The effective use of a model for aiding in the design of a soil-water remediation system requires an understanding of the reliability and limits of the modeling approach. To assure the quality of modeling predictions requires that the significant modeling processes are validated using the results of highly-controlled experiments. However, the actual model use is typically in a field setting with a limited amount of site characterization data available for model calibration. A discussion of the procedures that should be followed for validation of modeling processes and the usage of the validated model in a field setting is presented. Methods for assessing the reliability of the modeling approach and the uncertainty of applying the model in a field setting are also addressed.

Key words: quality assurance, model validation, model usage.

Poster presentation.

69 • EXPERIMENTAL VERIFICATION OF REVISED FIRAC

P.R. Smith, E. Hensel, I. Leslie, and C. Ricketts, Mechanical Engineering Department, New Mexico State University, Las Cruces, NM, 88003

The objective of this project was to carry out experimental studies of fires within the ventilation system of a model nuclear facility in order to validate the gas dynamic module and the heat transfer module of the FIRAC fire simulation code developed by Los Alamos National Laboratory. The version of FIRAC to be verified was one which successfully ran on CRAY computers, but revised to operate on personal computers. The experiments necessary to evaluate the various modules of the code were accomplished in the Large Scale Flow Facility at New Mexico State University. This facility is a large-scale model which contains all the elements, such as blowers, dampers, and High Efficiency Particulate Air (HEPA) filters that are found in typical ventilation systems of nuclear facilities. Several experiments were performed and the initial conditions were input into FIRAC in order to check the simulated results against the experimental results. The comparison of results indicated that the code predicts the general behavior of the gas dynamic and heat transfer occurring within the experimental ventilation during a fire fairly well. In addition to the experiments performed at New Mexico State University, the code is also being used to simulate a fire within a German nuclear reactor building. This experiment was carried out by the personnel of Kernforschungszentrum of Karlsruhe, Germany, at a decommissioned reactor building located in Karlstein, Germany. The simulated results agree closely with the actual results.

Key words: FIRAC, nuclear, ventilation, fires, gas dynamic module.

Poster presentation.

70 • MODELING OF HEAVY METAL TRANSPORT AND SOIL EROSION IN SURFACE RUNOFF

S.R. Ramireddygari¹, R.S. Govindaraju¹, and L.E. Erickson², ¹Department of Civil Engineering and ²Department of Chemical Engineering Kansas State University, Manhattan, KS, 66506

A physically-based model was developed for rainfall, runoff, erosion, and solute transport processes on land surfaces under time-varying rainfall events. Kinematic wave approximation was used to describe the overland flow dynamics. Erosion equation was represented as a first-order reaction with the reaction rate being represented by soil erodibility. The solute transport equations were based on a convective-dispersive model that incorporates rate-limited mass transfer through a laminar boundary layer at the soil surface/runoff water interface. The model has been validated using the data available in literature. Results for the erosion and solute transport processes were validated separately. Experiments are planned for complete model validation.

Key words: modeling, heavy metal transport, soil erosion, overland flow.

Poster presentation.

71 • GAS-DRIVEN HYDROFRACTURE AT WIPP

W. Gerstle, Department of Civil Engineering, University of New Mexico, Albuquerque, NM, 87131

This presentation reports on continuing research in the simulation of gas-driven hydrofracture at the Waste Isolation Pilot Plant (WIPP). The simulations employ analytical, computer, and physical models. Several advances have been made in our understanding of the hypothesized formation of a horizontal, circular hydrofracture several kilometers in radius. The fracture is hypothesized to develop in an anhydrite layer. The hypothesized hydrofracture could form in response to waste gases generated as brine comes into contact with the waste. The possibility is investigated that after growing horizontally within the anhydrite layer, the crack could break out of this layer and propagate upward into the halite at an inclined angle of around 45º above horizontal. This scenario is studied using analytical methods and a finite element program capable of simulating linear elastic cracks. Results of physical models also will be presented.

Key words: Waste Isolation Pilot Plant, hydrofracture, nuclear waste management.

Poster presentation.

72 • FAST NEUTRON THERMALIZATION AND CAPTURE GAMMA-RAY GENERATION IN SOILS

R.E. Faw, S.L. Shue, and J.K. Shultis, Nuclear Engineering Department, Kansas State University, Manhattan, KS, 66506-2503

This is a report of progress on an investigation of the feasibility of using prompt-neutron, capture gamma-ray, neutron activation analysis (PGNAA) to determine the vertical concentration profiles of contaminants in soil. The report, in particular, deals with the phase of the investigation pertaining to neutron transport and thermalization in soil, the capture of neutrons in contaminants such as heavy metals, and the transport of resulting gamma rays to radiation measurement systems above the soil. A second phase of the research deals with the inference of contaminant concentrations from measured gamma-ray energy spectra.

Soil characteristics most affecting neutron transport and thermalization are porosity and free-water content. Nominal characteristics, representative of many soils, were found to be a porosity of 50% and a value of 0.2 for the ratio of the free water mass in the soil to the mineral mass, resulting in an in situ density of 1.61 g/cm³. Soil extremes were characterized by a dry porous soil of density 1.18 g/cm³ and a wet dense soil of density 2.09 g/cm³.

Most neutron capture takes place after the neutron has slowed to conditions of thermal equilibrium in the soil. It was found to be possible to determine effective neutron capture cross sections, so that only the spatial variation of the thermal-neutron flux density need be determined for different irradiation geometries and soil conditions. The product of the flux density and the capture cross section determines the capture gamma ray production rate per unit soil volume per unit contaminant concentration. This results in very great savings in data storage and manipulation requirements for those making use of PGNAA technology. Using both Monte Carlo and discrete ordinates methods, such profiles have been calculated and are illustrated. Methods were developed for computing capture gamma-ray transport in the soil and representative energy spectra are illustrated for selected contaminants and concentration profiles.

New applications of PGNAA technology are addressed in the report. Special attention is given to extensions permitting the imaging of three-dimensional artifacts buried in the soil. Two-dimensional images of buried drums of hazardous waste, generated using Monte Carlo radiation transport calculations, are presented in the report and methods for three-dimensional imaging are discussed.

Key words: soil, contaminant, neutron capture gamma-ray.

Poster presentation.

73 • INTERPRETATION OF NEUTRON-CAPTURE GAMMA-RAY DATA TO DETERMINE SOIL CONTAMINANT PROFILES

J.K. Shultis, F.A. Khan, and R.E. Faw, Department of Nuclear Engineering, Kansas State University, Manhattan, KS, 66506-2503

Neutron irradiation of soil and measurement of the subsequent capture gamma photons at the soil surface is a potentially powerful method for in situ determination of vertical concentration profiles of many elemental contaminants. For a particular contaminant, the intensity c_i of the capture photon with the i-th energy, i = 1,...N, at a point detector located at or above the soil surface is given by an equation where u(x) is the concentration of the contaminant at depth x and K_i(x) is a known kernel appropriate to the neutron source and detector used. The inversion of this Fredholm integral equation for u(x) is notoriously difficult especially since the number N of measurable capture photons with different energies is usually small, typically 3 to 10.

The capabilities and limitations of two different inversion techniques are presented for the soil contamination problem. The first inversion method, linear regularization (LR), approximates the integral equations by a set of (underdetermined) algebraic equations of the form of an equation where u_j is the unknown contaminant concentration at M (> N) discrete soil depths. Several methods for calculating the matrix elements R_ij from the kernels K_i(x) are presented. The solution of these algebraic equations can then be obtained by imposing additional constraints such as a variety of smoothness conditions.

The second inversion method, the Backus-Gilbert (BG) technique, seeks a continuous solution û(x) of Eq. (1) that maximizes the resolution of changes in u(x) subject to a numerical stability constraint. This method has the advantage of explicitly depending directly on the measurement errors of the c_i, and although computationally more expensive than the LR method, produces estimates of u(x) that are always non-negative.

Results of applying these two inversion methods and their variants to benchmark test cases are presented. In particular, the sensitivities of the inversion methods to measurement errors, the number and energies of the capture gamma photons, detector geometry, concentration profile shapes, soil composition, and model approximations are discussed.

Key words: neutron capture, soil data inversion.

Poster presentation.

74 • METALS SOIL POLLUTION AND VEGETATIVE REMEDIATION USING POPLAR TREES AT TWO HEAVY METAL-CONTAMINATED SITES

W. Hse¹, C. Just², and J.L. Schnoor³, Rooms ¹125, ²120, and ³116, Engineering Research Facility, The University of Iowa, Iowa City, IA, 52242

Heavy metal-contaminated soils with arsenic (As), cadmium (Cd), lead (Pb), and zinc (Zn) from two different Superfund sites at Dearing, Kansas, and Whitewood, South Dakota, were monitored and compared. Poplar trees were planted at both sites to stabilize soils and limit vertical migration of leachate to the ground water. The southeast Kansas site, an abandoned smelter, has one of the largest concentrations of lead and zinc in the soil that has ever been reported for a hazardous waste site. Whitewood Creek site is the result of many years of mine tailings processing and contains appreciable arsenic, up to 8,000 mg/kg in hot spots.

The suitability of deep-planted hybrid poplar trees as a vegetative remediation strategy for both heavy metal-contaminated sites has been investigated and compared. An additional objective was to investigate the influence of poplar cultivar and soil amendments on poplar tree survival and growth.

This study has resulted in 1) a practical case study of vegetative remediation at two extremely contaminated sites, 2) a comparison of heavy metals uptake by vegetation for testing models of biogeochemistry, and 3) a surface coordination chemical model that relates soil chemistry to biouptake.

Key words: mine waste remediation, vegetative remediation, poplar trees in metals soil, soil chemistry.

Poster presentation.

75 • CLEAN-UP PROCEDURES FOR WASTE WATERS WHICH FLOW FROM REFINERIES AND OTHER CHEMICAL COMPANIES

V. Calamaz and G. Calamaz, Romanian Waters Authority, Str. serg Gh. Mateescu nr. 10, bloc 6, ap. 25, 2000 PLOIESTI Jud. PRAHOVA, ROMANIA

Romanian Water Authority-Ploiesti administrates the confined in the Prahova District. These waters are over 300 km. The main rivers are Prahova and Teleajen.

Prahova Country is well known as a beautiful tourist area, which contains all the relief forms: mountains, hills, and plains. This district is recognized also as an important industrial zone, represented by chemical and petrochemical industry.

Besides a lot of advantages, this industry still has many bad effects like water pollution. I work in the field of water quality and I am responsible for this.

The Prahova and Teleajen rivers were known until a short time ago to have a very high pollution concentration, especially with petroleum products and ash of iron, coming from the great refineries and the chemical combinate.

These rivers are different now. And this is possible because of my ideas, which are practiced on these channels with flowing waste water from the big polluting companies.

The recovery of these petroleum products is done with the installations designed by me.

The leaks are confined between 80-120 mg/l. Fixing in seria (after one) of these installations, the petroleum products concentration became 2-4 mg/l. From the chemical combinate, which are made of chemical products, the iron ash confined in the waste water which is spilled, is confined between 1,200-1,600 mg/l. Using this recovery device, the final concentration is 30-60 mg/l. We used this opportunity to aerate the water.

If everyone thinks with more responsibility of the people around him, we will be a thousand times better off and more beautiful.

A motion picture with all these discoveries will be presented.

Key words: surface water clean up.

Poster presentation.

76 • EFFECTS OF PRESSURE VARIATION ON TRANSPORT OF VOLATILE NONAQUEOUS PHASE WASTE CHEMICAL VAPOR IN HETEROGENEOUS FORMATIONS

E.M. Johnson¹, T.H. Illangasekare¹, N.D. Rosenberg², and L.H. Auer², ¹Department of Civil Engineering, University of Colorado at Boulder, Boulder, CO, 80309, and ²Los Alamos National Laboratory, Los Alamos, NM

Understanding the transport of volatile organic chemicals in the vapor phase in unsaturated soils is of basic importance in the development and implementation of a number of remediation technologies such as passive vapor extraction, enhanced vapor recovery, soil vapor extraction, aeration, and big-venting. In these schemes, the pressure gradients in the gaseous phases are used to move the vapor through the soil. External pressure (or vacuum) is applied to create the driving gradients. In some vadose zone contamination situations the cyclic variations of atmospheric pressure (barometric pumping) that is enhanced through the use of boreholes or found naturally have been found to mobilize and transmit the vapor phase to the ground surface. It is our hypothesis that the soil heterogeneities play a significant role in the way these pressures are transmitted and how the vapor phase gets mobilized. Existing literature on the subject suggests that very little is known on the effects of heterogeneities on contaminated gas flow through the vadose zone.

The objective of the research presented in this paper is to understand and quantify the mobilization and movement of volatile organics in the heterogeneous vadose zone as a result of barometric pumping. An experimental facility consisting of a stainless steel column fitted with sampling ports to extract air samples was developed. A pool of test chemical (TCA) was placed in the bottom of the column and small cyclic pressure fluctuations were applied at the soil surface at the top of the column in order to mimic the barometric pressure changes. Extracted air samples were tested using a GC/FID to determine the dynamic variation of vapor concentrations along the column. Experiments were conducted with different heterogeneous packing configurations. The experimental results are used to parameterize the hydrodynamic dispersion and effects of cyclic pumping on VOCs in the vadose zone. The experimental results and analysis on how the information generated in the column can be used in the field in the design and implementation of remediation technologies are presented.

Key words: remediation, cyclic pumping, SVE, vadose zone, heterogeneities.

Poster presentation.

77 • SPREADING OF DENSE NONAQUEOUS PHASE LIQUIDS IN RANDOMLY HETEROGENEOUS AQUIFERS: EXPERIMENTS ON MULTIPLE REALIZATIONS

R. Compos, T.H. Illangasekare,and H. Rajaram, Department of Civil, Environmental, and Architectural Engineering, University of Colorado, Boulder, CO, 80309

A significant fraction of nonaqueous phase fluids remains entrapped in the spread-zone of heterogeneous aquifers, long after the spill. In our past research we have shown that in spill experiments with structured heterogeneities, saturations within the region of entrapment varied from residual to almost full saturation. Estimation of the highly variable saturation field is of value in the context of remediation design. Initial DNAPL spill experiments in a large two-dimensional tank packed to represent a random heterogeneity demonstrated that pore-scale fingering played a critical role in the movement and final entrapment distribution of the chemical. This final entrapment distribution exhibited a random pattern. To avoid the generation of a large amount of waste and to allow for the possibility of conducting a number of experiments, a smaller glass-lined tank with the dimensions 4 ft x 3 ft was constructed. Spill simulations were conducted on randomly-generated heterogeneous packing configurations. Packing used in each spill simulation represented a realization of the same stochastic parameters of the random field. A dual-gamma system was used to determine the final entrapment distribution of the DNAPL. In this paper, we present the results of these multiple realization experiments. The data is analyzed to determine the stochastic parameters of the random entrapment distribution. This data is expected to be used in the validation of a macro-scale network model that can be used to predict the distribution of DNAPLs in heterogeneous formations.

Key words: organic waste, dense nonaqueous phase liquid entrapment, effective parameters, remediation design.

Poster presentation.

78 • CHARACTERIZING AQUIFER HETEROGENEITY USING HYDRAULIC AND TRACER TESTS: EXPERIMENTAL AND COMPUTATIONAL STUDIES

H.-C. Chao, H. Rajaram, and T.H. Illangasekare, Department of Civil, Environmental, and Architectural Engineering, University of Colorado, Boulder, CO, 80309-0428

It is well established that heterogeneities in aquifer properties have an important influence on field-scale contaminant transport, both for miscible and immiscible contaminants. The detailed characterization of aquifer heterogeneity, such as those accomplished at the Borden and Cape Cod sites, among others, is relatively time-consuming and expensive. An alternative approach is to determine statistical parameters characterizing the heterogeneity distribution using indirect methods such as forced-gradient pressure tests and tracer tests. In such an approach, careful attention must be given to a host of scale issues. For instance, a tracer test over a scale comparable to or smaller than the characteristic scale of variability will not yield much information on the heterogeneity. Therefore, it is possible that a successful approach should involve tracer tests on several scales.

In this investigation, we present experimental and computational studies examining the use of tracer tests for characterizing aquifer heterogeneity. The experimental studies involve pressure and tracer tests conducted in an 8'x4' laboratory tank, packed with soils in a randomly heterogeneous configuration. The random hydraulic conductivity distribution was generated using a computer algorithm. Natural gradient and forced-gradient tests were conducted in the test aquifer, and the data are used to estimate the mean, variance, and correlation scales of the hydraulic conductivity distribution. The reliability of the estimates is investigated via computational experiments on multiple realizations of the random field with the same statistical parameters as in the laboratory tank. Implications for the use of these tests at the field-scale are discussed.

Key words: aquifer heterogeneity, effective parameters, contaminant transport, remediation design.

Poster presentation.

79 • REDUCTIVE DECHLORINATION OF CARBON TETRACHLORIDE USING ZERO-VALENT METALLIC ELECTRODES

Z. Liu¹, R.G. Arnold¹, and E.A. Betterton², ¹Department of Chemical and Environmental Engineering and ²Department of Atmospheric Sciences, University of Arizona, Tucson, AZ, 85721

An electrochemical batch reactor was set up to investigate the dechlorination of carbon tetrachloride (CT). Various zero-valent metallic foils were used as the cathodic electrodes, and platinized platinum foil was the counter electrode. At the cathodic electrode, CT was reduced to chloroform, dichloromethane, and eventually to methane. Ethylene, ethane, propane, etc., were identified as byproducts during the dechlorination process indicating that free-radical reactions are among the chemical conversions at the cathode surface. Reaction rate was first-order in CT and depended on electrode materials, cathodic potential, surface area of the cathode, and pH. At a cathodic potential of -1.0V (vs. SHE) and pH 7.0, nickel was the most reactive of the electrodes tested (k = 9.0 min^-1.m^-2; Ni>Co>Cu>Fe>AI). When the working electrode was comprised of copper, 85% of the CT converted yielded products that were completely dehalogenated. More negative cathodic potentials produced higher reaction rates until mass transfer limits were encountered at E£-1.4V (vs. SHE). A model was developed to describe the kinetics of CT degradation.

Key words: reductive dehalogenation, remediation, ground water, elemental metals.

Poster presentation.

80 • A COMBINED PLASTICITY/DAMAGE MODEL FOR CREEP OF ROCK SALT

Z. Chen, M.L. Wang, and T. Lu, University of New Mexico, Engineering Research, Albuquerque, NM, 87131

Natural salt deposits are considered a desirable host rock for permanent disposal of radioactive waste because the creep response of rock salt allows the closure of the disposal room, leading to eventual encapsulation of the radioactive waste and minimizing the possibility of leakage and contamination to the environment. An attempt is made in this project to formulate a constitutive model to describe the creep mechanisms of rock salt. To meet safety and regulatory requirements, the long-term performance of bedded salt deposit must be predicted with a high degree of confidence. However, it is impossible to obtain the long-term performance result from tests. It is only possible to predict the long-term performance based on its short-term performance result. A constitutive model derived from the short-term performance is constructed to fulfill this requirement. Since the failure of materials is considered, the tertiary stage of creep process must be included. As observed from micro- and macro-experiments, the transition between the secondary and tertiary stages of rock salt creep is characterized by localized damage. The reduction in net loading area under constant creep load will result in the acceleration of damage and final dynamic crack growth. In order to predict the complete creep process in a continuum sense, a combined rate-dependent plasticity/damage model is developed in this project. The experimental data are used to verify the model in the uniaxial stress state and triaxial stress state.

Key words: rock salt, creep, radioactive waste.

Poster presentation.

81 • MECHANISMS GOVERNING THE REMOVAL OF WASTE FROM A WASTE REPOSITORY CAUSED BY EXPLORATORY DRILLING

M.L. Wang, X.M. Chen, M.A. Starnes, and J. Berglund, University of New Mexico, Albuquerque, NM, 87131

This report describes the theoretical basis of the GASFLOW computer code which was written to calculate the quantity of radioactive material brought to the surface from a radioactive waste disposal facility due to an inadvertent drilling intrusion. The GASFLOW computer code determines the amount of material removed by gas blowout (several other release mechanisms are reported by NMERI [Berglund, 1993]). The GASFLOW computer code was written specifically for the computations required for the performance assessment of the Waste Isolation Pilot Project (WIPP) but with due care can be used for the prediction of gas emission in coal mines also. The final product of decomposed and compacted transuranic waste is currently unknown. As a result, waste surrogate materials are needed to study the mechanical properties of the decomposed waste. This report outlines the mechanical properties of three surrogate materials developed with different percentages of crushed salt, clay, and silica sand.

Key words: GASFLOW, radioactive waste, drilling.

Poster presentation.

82 • ADAPTIVE CONTROL OF CONSTRAINED ROBOTIC SYSTEMS FOR WASTE MANAGEMENT APPLICATIONS

R. Colbaugh and G. Gallegos, Department of Mechanical Engineering, New Mexico State University, Las Cruces, NM, 88003

The U.S. Department of Energy is presently involved in a comprehensive program of environmental restoration and waste management (ER&WM), and has identified robotics as a major technology to be utilized in this waste management effort. In particular, robotic handling of hazardous waste has been targeted as an essential element in the solution of many ER&WM problems of national importance. Included among these problems are the remediation of waste storage tanks, the retrieval and repackaging of buried waste, the minimization of waste produced, the decontamination and decommissioning of inactive DOE facilities, and the handling and inspection of waste within repositories. The rationales for using robotic systems in these waste management operations are many, and include the desire to remove humans from hazardous environments, to reduce the cost of the operations, and to increase the speed with which the operations can be performed. Unfortunately, experience with the application of robotic systems to the handling of hazardous waste is quite limited in the U.S. The majority of robots in operation today are fixed-base manipulators performing simple, repetitive tasks in highly structured surroundings with no direct interaction with the environment. This is in contrast to the waste handling applications mentioned above, which will require both robotic arms and mobile robots to perform complex tasks involving significant interaction with their environment and which will demand that these complex tasks be completed despite considerable uncertainty regarding the system and its environment.

One of the more challenging aspects of robotic waste handling is the problem of controlling the robotic system in a satisfactory manner. Contributing to the difficulty of this control problem is the inherent difficulty of accurately and robustly controlling robotic systems in the presence of measurement and model uncertainty. It is well-known that control schemes which require precise knowledge of the complete system model to provide good performance suffer from many serious limitations. Additionally, it is usually unrealistic to assume that the entire system state can be accurately measured and used for feedback; indeed, although high-precision sensors are available for measuring the configuration of robotic systems, rate measurements are typically either contaminated with noise or not available at all. These facts provide much motivation for developing control methods which can be successfully implemented despite model and state uncertainties. Note that this challenging problem becomes even more difficult when the motion of the system is constrained in some way.

Previous studies of robotic waste management have clearly demonstrated that successful implementation of robotic systems for hazardous waste handling will require that these systems be capable of performing complex tasks while subjected to holonomic or nonholonomic (nonintegrable) constraints on the system kinematics. Consider, for example, tasks such as cutting, grinding, swiping, or mechanical assembly, which require a robot manipulator to come into contact with its environment. Such tasks restrict the motion of the manipulator end-effector, thereby imposing a set of holonomic constraints on the manipulator kinematics. As a consequence, the constrained robotic system evolves on a submanifold of the original (unconstrained) configuration space. The control problem in this case becomes one of controlling the motion on the reduced configuration space while simultaneously regulating the constraint forces which result from the interaction between the end-effector and the environment. This problem has received much attention during the past decade, and numerous results have been obtained. Here we simply note that the model is precisely known and that the entire system state is measurable. Observe that these assumptions are not satisfied in most robotic waste handling applications. Robotic systems with nonholonomic constraints on the kinematics are also quite common. For instance, these constraints arise in systems with rolling contact, such as wheeled mobile robots and multifingered robotic hands, and in systems for which the dynamics admit a symmetry, such as robots operating in failure mode. Most of the work reported to date on controlling nonholonomic robotic systems has focused on the steering or trajectory generation problem in which the system velocities are considered to be the control inputs, and the mechanical system dynamics are ignored. Work at the dynamic control level, where the control inputs are those actually produced by the system actuators and the system model contains the mechanical system dynamics, has been more limited. Moreover, virtually all of the control strategies proposed to date have been developed by assuming perfect knowledge of the system model and state. Recall that these assumptions are not appropriate for most robotic waste handling tasks.

This paper considers the problem of controlling holonomic and nonholonomic robotic systems performing waste management operations in the presence of measurements and model uncertainty, and presents a class of adaptive controllers as a solution to this problem. The proposed control strategies provide simply and robust solutions to a number of important robotic system control problems, including position/force stabilization of holonomically constrained robots, equilibrium manifold stabilization of systems with nonholonomic constraints, and equilibrium point stabilization of nonholonomic systems. All of the schemes are computationally efficient, are implementable without system dynamic model or rate information, and ensure uniform boundedness of all signals and accurate motion control. Computer simulation results are provided to complement the theoretical developments.

Key words: robotic systems, waste management, holonomic constraints.

Poster presentation.

83 • ADSORPTION OF COPPER IONS FROM SOLUTION BY HEAVY METAL STRESSED-LARREA TRIDENTATA (CREOSOTE BUSH) BIOMASS

J.L. Gardea-Torresdey, J. Bibb, K.J. Tiemann, J.H. Gonzalez, and J.L. Arenas, Department of Chemistry, The University of Texas at El Paso, El Paso, TX, 79968

Larrea tridentata (creosote bush) were found naturally growing in heavy metal-contaminated soils. Samples of Larrea tridentata were collected from six different locations to study their ability to bind copper ions from solution. Samples from the same locations were either oven dried at 90°C or lyophilized in order to determine differences in drying conditions. Batch laboratory experiments were conducted with the leaves of Larrea tridentata in order to determine pH profiles, time dependency, and total copper binding capacity. It was determined by the pH profile experiments that the optimum copper binding pH was between 5 and 6. A maximum adsorption of copper ions was observed within five minutes of reaction time for most of the biomass collected from the various sites. The copper binding capacity experiments showed that one gram of biomass can bind as much as 23.7 mg and as low as 13.4 mg of copper. The capacity to bind copper ions by the biomasses varied according to the location of the sample site. These differences in capacities correlate with the distances from the collection site to the possible contamination source. The closer the sample to the possible source, the greater the copper binding capacity. Future studies will include batch laboratory experiments for copper binding by the roots and stems from the various locations, as well as binding abilities for other metals.

Key words: Larrea tridentata, phytoremediation, copper, metal binding.

Poster presentation.

84 • STRONG OXIDANTS FOR ORGANIC WASTE DESTRUCTION FROM OXIDATION OF MANGANESE HYDROXIDE

D.K. Cha and S.-M. Park, Department of Chemistry, University of New Mexico, Albuquerque, NM, 87131

The electrochemical oxidation of manganese hydroxide has been studied in 0.10 M KOH solutions at manganese electrodes employing a variety of electrochemical techniques in an effort to obtain strong oxidants including manganese oxyhydroxide, manganese dioxide, and permanganate, which are proposed to be used for destruction of organic wastes, and to elucidate mechanisms involved therein. The charge transfer process was shown to be affected by the film formed on the electrode surface during redox processes. Electrode potentials for redox processes between manganese hydroxide and higher valence oxides, as well as the manganese metal, have been assigned. Strong oxidants such as manganese oxyhydroxide, manganese dioxide, and permanganate were easily obtained by the oxidation of manganese hydroxide. Diffusion coefficients and an exchange rate constant for redox processes are also reported.

Key words: oxidation, manganese hydroxide, organic waste.

Poster presentation.

85 • NEW APPROACHES FOR ELEMENTAL SPECIATION STUDIES

J.A. Caruso, Department of Chemistry, University of Cincinnati, P.O. Box 210172, Cincinnati, OH, 45221-0172

Plasma source mass spectrometry (plasma MS) is a state-of-the-art technique for ultra-trace level elemental analyses. Coupled with the ability to determine selected isotopes and to perform multielement analysis, it is rapidly becoming a major analytical technique. Since this is also an element-specific technique, it has high potential for selective chromatographic detection to obtain speciation information along with the total trace element profile. The coupling of different chromatographic methods with plasma source mass spectrometry provides selectivity necessary and analyses at levels less than or equal to sub-ng to sub-pg amounts.

Low-volume and low-flow chromatographic methods favor the plasma experiment and allow structural, as well as quantitative, information. Gas or supercritical fluid chromatography are low-flow, low-volume methods and provide levels of detection in the pg to sub-pg range. Recently we have been exploring glow discharges for GC detection. The rf glow discharge operates at low powers and can utilize helium or argon gases. The GD sufficiently ionizes the sample for MS detection at low levels. It also provides structural information at the same levels. A further departure is to utilize low-pressure helium ICP-MS for elemental speciation studies. The LP-ICP provides detection levels similar to the helium glow discharge and also provides structural information. These two plasma types will be compared and contrasted for their potential as detectors for elemental speciation studies.

Key words: plasma source mass spectrometry, elemental speciation, chromatographic detection.

Poster presentation.

86 • BIOLOGICAL AND CHEMICAL NITRATE REMOVAL USING AUTOTROPHIC DENITRIFIERS AND ZERO-VALENT IRON

B.A. Till¹, L.J. Weathers², and P.J.J. Alvarez¹, ¹The University of Iowa, Department of Civil and Environmental Engineering, Iowa City, IA, 52242, and ²University of Maine, Department of Civil and Environmental Engineering, Orono, ME, 04469

Nitrate is a priority pollutant due to its potential to cause methemoglobinemia (i.e., blue baby syndrome). There is also circumstantial evidence linking ingestion of nitrate to gastric cancer and birth defects. Nitrate contamination is a major water quality problem in agricultural regions. In Iowa, 1 million tons of nitrogen are applied each year, and several public water supplies (~ 60) and private wells (>1,000) exceed the drinking water standard (45 mg/l as NO3^- or 10 mg/l as N). While numerous physical-chemical and biological processes have been developed to remove nitrate from water, many of these processes are marginally cost-effective and/or have detrimental side-effects on water quality. Consequently, there is a need to explore novel alternatives to remove nitrate from water and wastewaters. This project investigated the feasibility of combining a novel chemical process (reductive treatment with zero-valent iron, Fe°) with a biological process (denitrification with autotrophic, hydrogen-utilizing denitrifiers).

Abiotic nitrate removal by various Fe° sources was investigated in batch (235 ml) serum bottles capped with Mininert^R valves. Iron powder (Aldrich Chemical Co.) exhibited faster rates for both nitrate removal and (water-derived) H₂ production as compared to Fe° filings. This was attributed to the higher specific surface area available for reaction in the Fe° powder. The more reactive Fe° powder, however, had an apparent toxic effect on bacteria. Thus, chemoautotrophic denitrifiers had a much higher beneficial effect when combined with Fe° filings than with Fe° powder. For microbial seeds, we used both axenic cultures of Thiosphera pantotropha (ATCC35512) and Paracoccus denitrificans (ATCC17741), and mixed cultures of indigenous aquifer denitrifiers that had been enriched with H₂ and nitrate.

To demonstrate that Fe° was serving as the ultimate electron donor and energy source for biological denitrification, we used a dual-flask apparatus similar to that used by Lacy Daniels to demonstrate "Bacterial Methanogenesis and Growth from CO₂ with Elemental Iron as the Sole Source of Electrons" (Science, v. 237, pp. 509-511, 1987). Two 250 ml Erlenmeyer flasks were fused at the top with glass tubing. An opening was made on the side of each flask for sample addition or removal. One of the flasks contained 10 g of Fe° and 100 ml of water, and the other flask contained 100 ml of mineral media with nitrate (40 mg/l as N). The flasks were purged with N₂/CO₂ (80:20, v/v) following inoculation with P. denitrificans. This setup permitted the diffusion of water-derived H₂ from the Fe°-containing flask through the connecting glass tubing to the seeded flask while avoiding potential microbial inhibition by iron species. Nitrate was removed below detection limits within 5 days in this apparatus. No nitrate removal or microbial growth was observed in control runs, lacking either Fe° or inoculum.

In summary, proof of concept was obtained that Fe° can reduce nitrate abiotically, and that this process can be enhanced by the presence of autotrophic denitrifiers. Specifically, Fe° can reduce water to H₂, which is utilized as an electron donor by autotrophic denitrifiers to reduce nitrate to harmless N₂. The high diffusivity of H₂ and the relatively low production of soluble microbial products by autotrophs suggest the feasibility of using autotrophic denitrifiers Fe° to remove nitrate from drinking water, either in ex situ reactors or in situ reactive filters for contaminated ground water.

Key words: autotrophic denitrification, hydrogen, iron, nitrate.

Poster presentation.

87 • DETERMINATION OF THE CONTENT OF HAZARDOUS HEAVY METALS IN LARREA TRIDENTATA (CREOSOTE BUSH) FOUND NATURALLY GROWING IN CONTAMINATED SOILS

J.L. Gardea-Torresdey, S. Arteaga, K.J. Tiemann, J. Bibb, and J.H. Gonzalez, Department of Chemistry, The University of Texas at El Paso, El Paso, TX, 79968

The content of copper, lead, cadmium, and nickel in tissues of Larrea tridentata (creosote bush) found naturally growing in a contaminated area was determined by Atomic Absorption Spectroscopy. The area was divided into six sections, and each section was studied individually. Separate analyses were performed for the Larrea roots, stems, leaves, as well as for the soils in which the plants grew. Lead concentrations in roots, leaves, and stems were 650 mg/kg, 150 mg/kg, and 110 mg/kg, respectively, while copper concentrations were 953 mg/kg, 493 mg/kg, and 370 mg/kg, respectively. In contrast, cadmium concentrations were lower and varied from 30 mg/kg in the roots, 37 mg/kg in the leaves, and 10 mg/kg in the stems. The content of nickel determined in Larrea ranged from 27 mg/kg in the roots, 23 mg/kg in the leaves, and 10 mg/kg in the stems. The soil concentrations where Larrea grew were high for lead and copper, 5,067 mg/kg, and 4,933 mg/kg, respectively. In contrast, lower concentrations were found in the soil for cadmium and nickel, 117 mg/kg and 17 mg/kg, respectively. The heavy metal content of the soils indicates the degree of pollution in the area. As it was expected, those sections which contained higher levels of heavy metals in the soil also showed to have higher heavy metal uptake by the various parts of Larrea tridentata. These data demonstrate Larrea tridentata's ability to uptake copper and lead, and to some extent cadmium and nickel, from heavy metal-contaminated soils. Analyses of other heavy metals will also be examined.

Key words: Atomic Absorption Spectroscopy, heavy hazardous metals, pollution, Larrea tridentata, environmental analyses.

Poster presentation.

88 • MODELING THE ROLE OF MICROORGANISMS IN THE MOVEMENT OF LEAD IN UNSATURATED REGION

K.V. Nedunuri, R.S. Govindaraju, and L.E. Erickson, Kansas State University, Manhattan, KS, 66502

Movement of lead through the vadose zone of soil is influenced by the presence of organic matter and microorganisms. Among the different microbial species that exist in the soil rhizosphere, algae is known to accumulate heavy metals significantly. The metal uptake by algae arises from two processes: a rapid passive uptake due to surface binding on the cell walls, and a subsequent slow active uptake due to transport of metal to the interior of the cell. The passive uptake of lead is modeled as an instantaneous reaction, while the active uptake is modeled as a complex kinetic reaction. Monod's model is used to describe the growth kinetics of the algal species. Organic matter serves as the substrate for the algae. The effect of adsorption of lead, under different growth conditions of algae in the vadose zone, is studied through model simulations.

Key words: vadose zone, modeling, microorganisms, heavy metal uptake, adsorption kinetics.

Poster presentation.

89 • NATURAL BIOVENTING REMEDIATION FROM TIDAL WAVE ACTION AT A FIELD SITE

D.H. Kampbell, National Risk Management Research Laboratory, U.S. EPA, Ada, OK, 74820

A remediation research study has been implemented at a jet fuel spill site on an island airport. The fracture of a buried pipeline resulted in a fuel spill several years ago exceeding 100,000 gallons. The site hydrogeology is a fragmented coral matrix with fresh water overlying more dense salt water. Water table fluctuations of two feet occur once every twelve hours from tidal action. The research approach being pursued is to pump off free-floating fuel and use a natural bioventing process caused by tide oscillations to remediate the site. Initial soil gas measurements have determined that oxygen in the vadose zone increased as the tide drops and carbon dioxide, along with methane, increased as the tide rises.

Key words: jet fuel, tide action, bioventing.

Poster presentation.

90 • CHARACTERIZATION OF PARA AND META PCB-DECHLORINATING ANAEROBIC COMMUNITIES BY 16S rRNA GENES

To determine if changes in dechlorinating activity reflected changes in microbial structure, we compared the distribution of 16S rRNA genes in PCB dechlorinating consortia. Community DNAs were purified from a para-(#7) and a meta-(#10) consortium. 16S rRNA genes were PCR amplified with two primers based on conserved regions of eubacterial 16S rRNA genes. PCR amplified 16S rRNA genes (1.5 kb size) were cloned into PCR II vector (39 kb size) using TA Cloning Kit (Invitrogen). Clones were screened for inserts by X-gal complementation and direct-colony PCR. The 15 kb inserts were verified as 16S rDNAs by hybridization with 32p labeled rDNA probes. Twenty-three-para and twenty-five-meta clones were digested with Rsa I and Eco RI in combination to generate RFLP patterns. Based on the restriction patterns, clones were sorted into 12 operational taxonomic units (OTUs). The most abundant OTU was significantly different between the para and meta communities suggesting changes in community structure.

Supported in part by the R2D2 program of the Great Lakes and Mid-Atlantic Hazardous Substance Research Center, and partly by grants received from NIGMS (NIH) to SKD.

Key words: OTUs, 16S rDNA, polychlorinated biphenyls dechlorination.

Poster presentation.

91 • AIR-SPARGED HYDROCYCLONE TECHNOLOGY FOR ENVIRONMENT APPLICATIONS

Y. Yi, Advanced Processing Technologies, Inc., P.O. Box 58131, Salt Lake City, UT, 84158-0131

There are a wide variety of radioactive, toxic, heavy metal, oil, VOC, and DNAPL contaminants in the ground waters and soils at a variety of government and/or industrial facilities. Clean-up of these contaminants is a difficult task. First, it is a great challenge to remove each individual contaminant by an individual technology. Second, many sites are contaminated by multicontaminants, not a single compound at each site. To decontaminate a site containing multicontaminants, a combination of different types of technologies/equipment is needed. This practice significantly raises the cost in decontamination process and causes a complexity and difficulty of the process as compared with a single technology for a single application which is already a difficult task.

In view of the above situations, Advanced Processing Technologies, Inc. (API) is developing a differential separation concept, i.e., using one key technology to process/remove different contaminants step-by-step through proper engineering and circuit design. The successful development of such a technology/circuit will significantly reduce the complexity, capital equipment cost, and operation cost during the decontamination process. The technology in consideration is the air-sparged hydrocyclone technology which currently is protected by six U.S. patents and many foreign filings. Application of the technology in environmental fields has been under the development by APT during the past several years, and the technology has been demonstrated to have diversified functions to remove different contaminants from different streams. This may provide a unique opportunity and offer a strong potential for the removal of heavy metals, VOCs, oil, DNAPLs, and others from contaminated soil and ground water through a differential removal process.

Key words: air-sparged hydrocyclone technology, multicontaminants.

Poster presentation.

92 • BIOLOGICAL TREATMENT OF AIR STREAMS CONTAMINATED WITH ORGANIC VAPORS

F.G. Edwards¹, N.N. Khandan¹, and J.M. Phalen², ¹Civil Engineering Department 3CE, New Mexico State University, P.O. Box 30001, Las Cruces, NM, 88003, and ²Sandia National Laboratories, Environmental Restoration Technologies Department, Albuquerque, NM, 87185

The clean-up of soils contaminated with organic chemicals, such as fuels or solvents, is often accomplished by soil venting. The subsequently contaminated air is typically treated when pumped through granular activated carbon (GAC), which adsorbs the contaminants from the air. When the adsorptive capacity of the GAC is exhausted, the carbon can be reactivated and the pollutant oxidized using thermal processes, which are expensive. An innovative method of reactivating the carbon and oxidizing the pollutant is to use microbes which utilize the pollutant as a food source. The goal of this research is to determine if a three-phase, fluidized, up-flow bioreactor is a viable treatment method for treating air-streams which are contaminated with organics; and to define design and operational parameters of the bioreactor.

Initial studies consisted of theoretical process modeling to define the transfer of the contaminant from the gas phase, transfer of oxygen to the liquid phase, uptake of oxygen by the microbes, adsorption of the contaminant by the activated carbon, and utilization of the contaminant by the microbes.

Bench-scale studies were undertaken to determine the range of velocities required to fluidize the GAC (using various combinations of water and air), to determine the adsorptive capacity of the GAC versus contaminant concentration for each pollutant, and to develop a microbial population which can utilize each of the pollutants. Further bench-scale studies have been undertaken to determine the BOD of the pollutants, to determine the rate of utilization of the contaminant by the microbes, and to determine the rate of increase in the microbial population. In addition, bench-scale studies were conducted to determine the parameters of the theoretical model.

Current research has validated and fine-tuned the proposed model using pilot-scale reactors and three organic chemicals. Removal efficiencies for the three chemicals tested range up to 95%. It is intended to validated field conditions using a pilot-scale reactor, which will be located at Sandia National Laboratories Mixed Waste Landfill.

Key words: activated carbon, airlift bioreactor, airstreams, BETX, biological treatment, modeling, organic vapors.

Poster presentation.

93 • ULTRASONIC ENHANCEMENT FOR IN SITU REMEDIATION OF CONTAMINATED SOIL

H.J. Fernandez and D. Hanesian, New Jersey Institute of Technology, CEES Building, 138 Warren Street, Newark, NJ, 07102

The objective of the present study is to use ultrasonic energy as an enhancing technique for in situ remediation of organic contaminants. Ultrasonic waves will be coupled with soil fracturing techniques to desorbed contaminants from the low permeability formations. It is believed that doubling the detoxification rate may be possible. This would cut the treatment time in half, thus realizing a significant savings in labor and operational costs. A portion of these savings will be offset by the capital cost of the ultrasound generators and the power requirements, but these are anticipated to be modest. It is expected that the coupling of ultrasound with the proven process of soil fracturing will yield positive, enhanced results.

Key words: ultrasound, soil fracturing, enhancement.

Poster presentation.

94 • NOVEL CHOLINE ESTERASE-BASED SENSOR FOR MONITORING OF ORGANOPHOSPHORUS POLLUTANTS

E. Wilkins, A.L. Ghindilis, and P. Atanasov, Chemical & Nuclear Engineering Department, University of New Mexico, Albuquerque, NM, 87131

Organophosphorus compounds are significant major environmental pollutants due to their intensive use as pesticides. Potentiometric electrodes based on detection of choline esterase inhibition by analytes has been developed. The detection of choline esterase activity is based on the novel principal of molecular transduction. Immobilized peroxidase acting as the molecular transducer catalyzes the electroreduction of hydrogen peroxide by direct (mediatorless) electron transfer. The sensing element consists of a carbon-based electrode containing an assembly of co-immobilized enzymes: choline esterase, choline oxidase, and peroxidase. The enzymes catalyze a sequence of reactions.

Two of these reactions result in the formation of hydrogen peroxide and lead to a change of the electrode potential. The potential shifts towards equilibrium H₂O₂/H₂O potential due to a third reaction catalyzed by peroxidase. The rate of the potential change is proportional to the activity of choline esterase.

The sensing elements development involved screening of different carbon-based electrode materials, modification of electrode surface, and testing of different types of chemical immobilization. For electrode material selection, a number of different carbon-based compounds were screened and tested. These involved carbon fiber, felt and matt, graphite materials, and some highly dispersed carbon materials.

The immobilization of enzymes was conducted utilizing commercially-available materials. The effect of electrochemical pretreatment of these materials was also studied. Different techniques of enzyme immobilization were used for sensing element fabrication, and the results were compared. Immobilization techniques were based on physical sorption and chemical binding of enzyme amino groups to modified and unmodified carbon surface.

Butyryl choline sensitive three-enzyme electrode has been developed employing highly dispersed carbon as an electrode material. Immobilization procedure is based on physical adsorption of peroxidase and co-immobilization of choline oxidase and choline esterase by glutaraldehyde technique. The electrode remains 100% active during one month storage at 4ºC. The procedure for measuring the electrode activity requires 2-3 min.

Incubation of the electrode in a solution containing organophosphorus pesticide trichlorfon for 10 min. results in notable decrease of electrode activity. This allows determination of sub-micromolar concentration of pesticide.

The application of the biosensor described above is associated with the monitoring of the organophosphorus pesticide pollutants in sampled soils, streams, and ground and waste waters. One of the most important preventive measures in this case is to rapidly determine the source of the pollutant and the magnitude of threat from on-site measurements.

Key words: sensor, organophosphorus compounds, choline esterase, enzyme.

Poster presentation.

95 • POLYMER GEL AS A BARRIER FOR GROUND OIL SPILL CONTAINMENT

J.C. Miller and E. Wilkins, Department of Chemical & Nuclear Engineering, University of New Mexico, Albuquerque, NM, 87131

Testing and development of technology to contain ground chemical and oil spills continues as a result of local and national concerns. These concerns arise from increased environmental awareness, directed toward the preservation of water quality and the restoration of contaminated surface and ground waters. Preventing petroleum slop oil and sludges and other waste fluids from leaching into the surrounding subsurface environment has become a growing concern. Contaminants can migrate to aquifers, thereby risking contamination of city drinking water, as well as rural aquifers. Contaminants in subsurface water also pose threats to agricultural activities, rapidly migrating higher up the food chain from plants. One possible solution is to employ a polymer gel as an impervious barrier between the contaminants and adjacent soil and ground water. The barrier can prevent leakage from accidents during transport, leaking from storage tanks, accidental discharges, etc.

Chemical dump sites as well as oil spills occurring in off-shore drilling may contaminate the shoreline several feet below the surface after preliminary clean-up has been accomplished. Since New Mexico does not have seas or large rivers in which oil spills might occur, this work will concentrate exclusively on containment of ground oil spills or chemical leakage from old or illegal dump sites. Further, in New Mexico there are many thousands of abandoned mines, mine dumps, and mill tailings ponds. Every one of these has the potential to become a hazard to human activities and to the environment. This class of problem is typical of those existing regionally, nationally, and even internationally.

The primary objective of this work is to develop a viscous polymeric gel to act as a sponge to absorb chemical leakage, i.e., effluent from industries and dump sites, and contain oil which has seeped into the ground from a spill of a leaking tank, or from oil transportation. The barrier will be formed by injection into the ground of ungelled and (hence low viscosity) polymer, which will then gel in controlled fashion. Injection of low viscosity fluid significantly reduces operating costs. This study developed several promising polymer gels and concentrated on the study of PAA gel cross-linked by different cross-linking agents. It was found that the gelation time can be easily controlled by the ungelled solution pH. The polymer gel barrier can decrease the permeability of sites significantly, to the order of 10^-8 to 10^-9 cm/s, which is much lower than the criterion for an ideal barrier. However the diffusivities of small molecules, in the polymer gel, such as dissolved petroleum hydrocarbon components is not much lower than in water. Even though over 95% of gel components are water, the cross-linked gel structure should retard diffusion more than water.

Key words: polymer gel, oil spill, water, agriculture.

Poster presentation.

96 • DEVELOPING A SITE-WIDE HAZARDOUS WASTE MINIMIZATION PROGRAM

R. Railan, Office of Cost and Performance Analysis (EM-15), U.S. Department of Energy, Washington, DC, 20585

The U.S. Environmental Protection Agency announced in March 1990, that in order to protect the nation's ground water, waste containing 25 toxic organic chemicals are now subject to safeguards of federal hazardous waste regulations. These chemicals are known to have contaminated ground water at hazardous waste sites.

The new rule increased the quality of non-wastewaters waste by 1.8 million metric tons per year. Additionally, 700 metric tons of wastewater was also affected. Much of that volume, however, is already managed in wastewater treatment tanks approved under the Clean Water Act.

With this rule 17,000 additional generators were to be affected including a variety of industries. As a result approximately 200 surface impoundments currently used to dispose of the waste also will be regulated under RCRA for the first time.

Estimated total costs of compliance range from $650 to $800 million a year.

Disposal of hazardous waste generated by the Department of Energy (DOE) will cost us, DOE and the taxpayers, millions of dollars every year. Substantial costs include environmental compliance, disposal, and liability. We have reacted to this problem by prescribing many remedies to try to solve it, i.e., HW treatment and reclamation facilities, and recycling and recovery facilities.

There is a need to develop a strong and cost-effective site-wide hazardous waste minimization program across the DOE complex, by taking the following steps: (1) define the program scope and objectives, (2) obtain and demonstrate top management support, (3) establish a HAZMIN (hazardous waste minimization) working group, (4) conduct a HAZMIN survey, (5) develop and implement a HAZMIN management plan, (6) develop Department's commitment to the HAZMIN program, (7) implement selected HAZMIN projects, and (8) track progress and reevaluate program scope and objectives.

Key words: waste minimization.

Poster presentation.

97 • NAVAJO NATION-BASED, CROWNPOINT INSTITUTE OF TECHNOLOGY'S ENVIRONMENTAL TECHNOLOGY PROGRAM

S. Chischilly, Crownpoint Institute of Technology, Crownpoint, NM, 87313-0849

The Crownpoint Institute of Technology (CIT), located on the Navajo (Diné) Nation, is currently developing an Environmental Technology program scheduled to begin in fall semester 1996. This program will allow post-high school Native American students to become skilled in environmental sampling techniques, data collection, and long term monitoring via hands-on field training, classroom presentation, and through cooperative agreements with tribal programs, businesses, industry, and other educational institutions on and off the Navajo Nation. Areas of study will focus on technical courses to meet the needs of tribal environmental programs, environmentally-oriented businesses, and natural-resource production or extraction companies throughout the Navajo Nation and southwestern United States.

Courses include Native American environmental remediation/restoration perspectives, hazardous materials, environmental regulations, asbestos and lead abatement, mining safety, HAZWOPER, introduction to radiation, solid waste management, emergency response, technical mapping, bioremediation, and an internship program. Graduates will be able to apply their knowledge in positions which do not necessarily require a four-year degree, but do require thorough environmental sampling knowledge, with an understanding of environmental laws, and the ability to communicate findings accurately.

Key words: Native American, environmental technology, Navajo Nation.

Poster presentation in Native American session.

98 • HERS: A CENTER FOR RESEARCH, EDUCATION, AND COMMUNICATION

W.M. Griswold¹, G.L. Godfrey¹, S.C. Grant², and P.T. Yazzie¹, ¹Haskell Indian Nations University, Department of Natural and Social Sciences, Lawrence, KS, 66046, and ²Great Plains/Rocky Mountain Hazardous Substance Research Center, Kansas State University, Manhattan, KS, 66506-2502

The Haskell Environmental Research Studies Center (HERS), located at Haskell Indian Nations University, Lawrence, Kansas, was created as a center for environmental research, education, and communication for Native American colleges, universities, and tribes. HERS, in conjunction with the Great Plains/Rocky Mountain Hazardous Substance Research Center (HSRC), administers the Native American and Other Minority Institutions (NAOMI) program. NAOMI was created to increase the involvement of minority educational institutions in research, training, and technology transfer activities. NAOMI will begin funding its first training program in May 1996. The program's goal is to create a HACH training center at Sinte Gleska University, Rosebud, South Dakota, and is a joint project between SGU and Navajo Community College, Shiprock, New Mexico. NAOMI is also continuing to coordinate a Summer Cooperative Research Program. This program matches NAOMI faculty and students with HSRC-funded research projects at other universities. Another primary element of the NAOMI program is a seminar series that provides education on hazardous substances and related environmental issues. HERS distributes the seminars through the use of videotapes and satellite downlinks. NAOMI links research, training, technology transfer, and education activities through the publication of a bimonthly newsletter, Earth Medicine, which reports on HERS and NAOMI activities to Native American colleges and universities, tribal offices, HSRC members, environmental firms, and EPA regional offices. HERS also coordinated a two-week environmental technology workshop for Native American and other minority students during summer 1995. HERS has also established a relationship with Boeing Commercial Airplane Group to provide an internship program for Haskell Indian Nations University faculty and students.

Key words: Native American, research, technology transfer.

Poster presentation in Native American session.

99 • ENVIRONMENTAL CONCERNS ON THE OSAGE RESERVATION

J.O. Bear, Haskell Indian Nations University, Division of Natural Sciences, 155 Indian Avenue, Box 1227, Lawrence, KS, 66046-4800, e-mail: jbear@hsrv.nass.haskell.edu

The Osage Indian Reservation, containing 1.5 million acres, is located in northeastern Oklahoma. Extensive oil production occurring over more than a 100-year period has brought forth hydrocarbon and heavy metal contamination of soil and water environs.

Key words: hydrocarbon contamination, ground water, pollution prevention.

Poster presentation in Native American session.

100 • NAVAJO STUDENTS MONITOR A LOCAL URANIUM-MILL TAILINGS SITE

C. Brown¹, M. Mitchell¹, W. Pierce¹, B. Tsosie², and S.C. Semken¹, ¹Navajo Dryland Environments Laboratory, Navajo Community College, Shiprock, NM, 87420-0580, e-mail: ndel@crystal.ncc.cc.nm.us, and ²Department of Earth and Environmental Sciences, New Mexico Institute of Mining and Technology, Socorro, NM, 87801

Navajo geoscience students are actively involved in the long-term monitoring of ground water quality at an abandoned uranium-mill tailings (UMTRA) site in the Diné (Navajo) Nation community of Shiprock. Ground-water contamination by suspected mill effluents and extreme proximity to the San Juan River, a major surface-water resource, render this a site of great environmental concern to the U.S. Department of Energy (DOE) and the Navajo Nation government, which share jurisdiction. Supported by a research grant from the DOE through the Waste-management Education and Research Consortium (WERC) and University of New Mexico, the students have received training in health and safety protocols, water-table measurement, ground water sampling, and geochemical analysis. Their work includes collection and interpretation of hydrogeological data that are used by DOE and Navajo agencies to guide ongoing remediation efforts at the site, and by WERC university partners to support postgraduate research. The students also participate in local community-awareness activities related to the project and its environmental consequences, and receive academic credit.

Key words: environmental education, uranium, remediation, Navajo.

Poster presentation in Native American session.

101 • MONITORING AND MINIMIZING AIR POLLUTANTS FROM PAINTS USED AT TURTLE MOUNTAIN MANUFACTURING COMPANY, BELCOURT, ND

C. Disrud and J. Desjarlais, Turtle Mountain Community College, Belcourt, ND, 58316-0340

Turtle Mountain Manufacturing Company (TMMC) is a metal-fabrication manufacturer located on the Turtle Mountain Indian Reservation. Its primary customer is the Department of Defense, which requires Chemical Agent coatings on contracted products such as water tanks and trailers that were used in "Desert Storm." The problem is that hazardous pollutants such as chloromethane or benzene may be emitted into the atmosphere by the venting system, but TMMC does not have the trained personnel nor the equipment to measure them. TMMC therefore does not have a procedure for air pollution control, and neither does the Turtle Mountain Band of Chippewa Indians.

Key words: Native American, chemical, source reduction.

Poster presentation in Native American session.

102 • AIR QUALITY AND RESPIRATORY HEALTH OF SHIPROCK (NAVAJO NATION) RESIDENTS: PRELIMINARY STUDIES OF METEOROLOGICAL AND HEALTH DATA

D. ManyCattle and R. Srivastava, Navajo Dryland Environments Laboratory, Navajo Community College, Shiprock, NM, 87420-0580, e-mail: ndel@crystal.ncc.cc.nm.us

Respiratory illness is a significant problem among Native Americans, and is a major cause of mortality. This is also true on the Navajo Nation in general and more so in the Shiprock area of the Navajo Nation. We suspect that ambient and indoor air qualities have a role in this, specifically in terms of particulate concentrations and the unique location of Shiprock in the San Juan River valley. As a part of a long-term study on respiratory health and air quality (indoor and ambient), we have initialized preliminary work on studying wind patterns and fuel use for cooking and home heating. These preliminary results will be presented. Health data, if accumulated and analyzed by May, will also be shared.

Key words: air quality, respiratory health, Navajo.

Poster presentation in Native American session.

103 • EARTH SYSTEMS AND NAVAJO PEDAGOGY

S.C. Semken¹ and F. Morgan², ¹Navajo Dryland Environments Laboratory and ²Center for Diné Studies, Navajo Community College, Shiprock, NM, 87420-0580, e-mail: ndel@crystal.ncc.cc.nm.us

Introductory geoscience at Navajo Community College, which is operated by and serves an exclusively Native American community, is taught using an Earth systems framework, wherein Earth materials, processes, and history are interpreted as the result of interacting solid-Earth (endogenic) and fluid-Earth (exogenic) processes. This pedagogy has first-order parallels in the Diné (Navajo) philosophy of nature, which attributes Hózhó or balance in the surface environment to processes of renewal driven by interactions between Nohosdzáán (Earth environment) and Yádilhil (sky environment). Second-order parallels between Diné models of equilibrium and perturbation and Euro-American models such as Le Châtelier's principle can be employed to teach geochemical cycles and processes such as weathering and metamorphism. Diné cultural content is to be reinforced through local field study and the use of appropriate cultural and linguistic references. The parallel use of Diné and Euro-American scientific concepts at Navajo Community College is intended to reinforce student understanding of, and to stimulate thinking and discussion of, ethnogeological concepts that have long been known to traditional Diné culture.

Key words: Navajo, education, Earth systems, geoscience.

Poster presentation in Native American session.

104 • DEVELOPMENT OF ENVIRONMENTAL TECHNOLOGY CURRICULUM FOR NATIVE AMERICAN COLLEGES

K. Topper¹, M. Gilfillan², F. Morgan³, R. Srivastava³, R. Walker¹, and S.D. Wolf³, ¹Mesa State College, Grand Junction, CO, 81501, ²RUST Geotech, Grand Junction, CO, 81502-5504, and ³Navajo Dryland Environments Laboratory, Navajo Community College, Shiprock, NM, 87420-0580

There have been very few efforts to develop Environmental Technology curricula for Native American community colleges, despite a history of environmental pollution and related problems on Native American lands. This project, funded by National Science Foundation ATE DUE grant #9454633, is developing a comprehensive curriculum package that specifically addresses American Indian environmental pollution problems. A significant portion of this project is focused upon incorporation of American Indian cultural values within this technologically-oriented field. A workshop was held at Crownpoint Institute of Technology to initiate the cultural inclusion, followed by a questionnaire and further development by the authors. This presentation will provide an overview of this project and results obtained to date. We encourage input from any interested people.

Key words: Native American culture, environmental technology.

Poster presentation in Native American session.

105 • COMMUNITY WORKSHOPS IN NAVICULTURE, TRADITIONAL PLANNING, AGRICULTURE, AND COMMUNITY ENVIRONMENTAL PLANNING WITHIN THE SHIPROCK AREA OF THE NAVAJO NATION

S.D. Wolf, Navajo Dryland Environments Laboratory, Navajo Community College, Shiprock, NM, 87420-0580, e-mail: ndel@crystal.ncc.cc.nm.us

This presentation will comprise summaries of: the goals behind the various workshops, the information presented, and the outcomes of the workshops. In addition, newsletters, questionnaires, and other information will be available.

The Naviculture workshop focused on philosophies and techniques which encourage planning for, and managing, natural resources to meet human needs with low-impact, low-cost methods. The Traditional Planning workshop discussed the difficulties in bringing together Western and traditional Navajo planning and problem-solving. Agriculture workshops were conducted to define collaborative agricultural projects within the Shiprock community. The Community Environmental Planning workshop provided a basic overview of the planning process, environmental considerations in planning, and hands-on exercises in some of the fundamentals of planning.

Key words: environmental planning, community, agriculture, Navajo.

Poster presentation in Native American session.

106 • NAOMI SEMINAR PROGRAM: EXPLORING NATIVE ENVIRONMENTAL ISSUES THROUGH VIDEO COMMUNICATION

P.T. Yazzie¹, W.M. Griswold¹, G.L. Godfrey¹, and S.C. Grant², ¹Haskell Indian Nations University, Department of Natural and Social Sciences, Lawrence, KS, 66046, and ²Great Plains/Rocky Mountain Hazardous Substance Research Center, Kansas State University, Manhattan, KS, 66506-2502

The Haskell Environmental Research Studies Center (HERS), located at Haskell Indian Nations University (HINU), Lawrence, Kansas, was created as a center for environmental research, education, and communication for Native American colleges, universities, and tribes. HERS, in conjunction with the Great Plains/Rocky Mountain Hazardous Substance Research Center (HSRC), administers the Native American and Other Minority Institutions (NAOMI) program. NAOMI was created to increase the involvement of minority educational institutions in research, training, and technology-transfer activities concerning hazardous substances. One of the primary elements of NAOMI is a seminar program that provides public education on hazardous substances and related environmental issues. HERS distributes the seminars through the use of videotapes and satellite downlinks. The seminar series targets students and faculty from minority institutions and mainstream institutions, tribal leaders and professionals, and the general public. Speakers for the seminar series include Native American professionals working in environmental fields with Native American tribes, environmental professionals, and faculty associated with the HSRC consortium. The seminar series includes issues such as the use of natural resources and the effects of that use on tribal life, pollution prevention, comparison of Native and Western views of nature, and a "Gathering for the Earth." The latter was part of the 25th anniversary of Earth Day in Washington, DC. In April 1996, HERS will sponsor the first satellite uplink from the HINU campus focusing on water quality, landfills, the ramifications of using traditional Native American lands for military purposes, and the effects of mining activities on tribal life.

Key words: Native American, research, technology transfer.

Poster presentation in Native American session.

107 • EFFECT OF PNEUMATIC FRACTURING ON AN EXISTING STRUCTURE

I. Nelson, M. Canino, and J.R. Schuring, Pneumatic Fracturing Research Group, Hazardous Substance Management Research Center, Department of Civil and Environmental Engineering, New Jersey Institute of Technology, Newark, NJ, 07102

Pneumatic fracturing is a technique used to enhance various environmental remediation technologies. It is particularly effective at sites with low ground permeability. Often such sites are located in urban areas adjacent to, or even within, existing structures. There is concern as to the potential structural effect caused by pneumatic fracturing adjacent to existing structures.

The current poster outlines a research study on an existing structure, the former Midland-Ross site in Highland Park, NJ. An injection well was placed within an abandoned warehouse. Limited data, including strain measurements, were taken during fracture. As part of study, an attempt also was made to create a structural model of the steel frame and masonry building. The project attempts to bracket the numerous uncertainties involved and to correlate the numerical and experimental results. Hopefully, broader implications to other structures would follow

Key words: pneumatic fracturing, structural modeling.

Poster presentation in R2D2 session.

108 • POTENTIAL OPTIONS & MANUFACTURING CHANGES FOR ETHYL ETHER IN SUPPORT OF POLLUTION PREVENTION

I.B. Zimmer, Emission Reduction Research Center, New Jersey Institute of Technology, University Heights, Newark, NJ, 07102-1982

This project focuses on replacing or eliminating the use of ethyl ether in Department of Defense systems (e.g., weapon systems, ammunition manufacturing, propellant manufacturing, and processing). An analysis of the processes using ethyl ether, a search for substitutions, and a review of modern techniques are central to this project. The results and procedures form the basis for broader application and chemical change. All conclusions and recommendations require laboratory verification.

Key words: ether, solvent, extraction, peroxide, volatile.

Poster presentation in R2D2 session.

109 • PNEUMATIC FRACTURING COMPUTER MODEL

B.M. Sielski and J.R. Schuring, New Jersey Institute of Technology, Center for Environmental Engineering and Science, 138 Warren Street, Newark, NJ, 07102

Pneumatic fracturing technology is now receiving considerable industrial attention since it addresses a problem which has plagued environmental clean-up efforts to date, i.e., remediation of low permeability geologic formations. Now that pneumatic fracturing is commercialized, there is an increasing need for a comprehensive computer model to aid in analysis. The computer model will be useful in deciding whether a site is a potential candidate for the technology. Presently, these decisions are made by informal comparisons with empirical data from past projects. The model will be programmed using Microsoft Visual Basic and have a Windows interactive interface.

The computer model will quantitatively compare geological properties and confirm applicability for a particular site. Once it is established that pneumatic fracturing is appropriate for a site, the model will be applied to preliminary design and estimation of parameters such as well spacing, injection pressure, and fracture interval. It could also be used to estimate the degree of enhancement of formation permeability and mass removal rate which may be expected. The user can investigate four principal model components: site screening, fracture propagation, fracture flow and transport, and supplemental injection.

Key words: pneumatic fracturing, computer model, VBasic.

Poster presentation in R2D2 session.

110 • INVESTIGATION INTO FRACTURE BEHAVIOR AND LONGEVITY OF PNEUMATICALLY-FRACTURED FINE-GRAINED FORMATIONS

H.A. Hall, J.R. Schuring, and T.M. Boland, New Jersey Institute of Technology, Center for Environmental Engineering and Science, 138 Warren Street, Newark, NJ, 07102

Pneumatic fracturing is an enhancement technology for in situ remediation of hazardous waste sites. It is most effective in improving the rate and efficiency of cleanup of low permeability formations when integrated with primary remediation technologies such as extraction, thermal treatment, and bioremediation. Changes in fracture aperture, or thickness, will significantly affect permeability rates reflecting changes in remediation efficiency.

This study investigated the effect of volume changes in fine-grained soil formations and their effect on pneumatically-induced fractures. A number of formation properties (i.e., physical, chemical, and mineralogical properties) and environmental conditions (e.g., moisture, pore fluid composition, surcharge pressure) were identified which affect fracture aperture.

Laboratory tests were first performed with control devices to investigate idealized fracture flow under linear and radial flow geometries. The experiments were then expanded to study volume changes in a natural soil which contained an artificial discrete fracture. A laboratory device termed a horizontal infiltrometer was developed to induce and control volume changes with moisture as the major variable.

A new concept of a "secondary active zone" was introduced which describes the zone of increased activity along the fracture boundary soils. A classification model was developed for assessing volume change potential using soil properties. The model also presents potential treatment alternatives including hydraulic control, chemical stabilization, and fracture propping.

Future work includes modeling changes in fracture aperture over time in low permeability soils using one-dimensional consolidation theory. Additional laboratory bench-scale tests will be performed with a variety of soil types and environmental conditions. The predicted volume changes will then be correlated with the experimental results and applied to a field case study.

Key words: clay, fracture, volume change, remediation.

Poster presentation in R2D2 session.

111 • USE OF IN SITU OZONATION FOR THE REMEDIATION OF CONTAMINATED SOILS

D. Cole, S. Masten, and S. Davies, Department of Civil and Environmental Engineering, Michigan State University, East Lansing, MI, 48824

Chemical oxidation may be used to overcome the limitations imposed by the low aqueous solubility of polycyclic aromatic hydrocarbons (PAHs) on their rates of biodegradation and dissolution. The objective of this study is to evaluate the effectiveness of using ozone for chemical oxidation of PAHs in soils from sites contaminated with jet fuel at Wurtsmith Air Force Base. The degradation of ozone in the soil, the effects of organic matter on ozone stability, and the effect of ozonation on the microbial community in the soil were investigated.

Key words: ozone, soil remediation, oxidation processes, hydrocarbons.

Poster presentation in R2D2 session.

112 • EFFECTS OF LAKE/AQUIFER INTERACTIONS ON THE BIOTRANSFORMATION OF CHLORINATED SOLVENTS DISCHARGING TO THE LAKE

S.M. Dean and N.D. Katopodes, Department of Civil and Environmental Engineering, University of Michigan, Ann Arbor, MI, 48109-2125

Contamination of ground water by chlorinated solvents is widespread and has been in the forefront of public and regulatory concern for the last decade. As a result, considerably research efforts, both in the laboratory and in the field, have addressed the potential for using biological processes to degrade these pollutants via in situ, or on site, bioremediation technologies. Natural attenuation has been observed to be responsible for removal or partial transformation of both chlorinated and non-chlorinated organic contaminants. At several sites, naturally-occurring reductive dechlorination has been found to be responsible for the transformation of trichloroethylene (TCE) to lesser chlorinated intermediates, such as c- and t-dichloroethylene (DCE) and vinyl chloride (VC), and to ethylene. Since contaminated aquifers can become oxygenated near ground water/lake interfaces, concerns have been raised with respect to surface water contamination by VC. At a National Priority List site near St. Joseph, Michigan, sequential geoprobe samples taken in the immediate vicinity of Lake Michigan suggest that lake water may be recirculating through the aquifer. In the current study, a modeling approach addresses the fate of TCE and its lesser chlorinated transformation products at this anaerobic/aerobic interface. The modeling effort describes and predicts the fate of the chlorinated solvents at and near the interface, taking into account ground water flow rates and microbial degradation rates, as well as the oxygenating effects from wave action and lake water intrusion near the shore line. Possible causes of lake water recirculation through the aquifer are investigated.

Key words: chlorinated solvents, lake, aquifer, biotransformation.

Poster presentation in R2D2 session.

113 • EFFECT OF ELECTRON DONOR AND ELECTRON ACCEPTOR CONCENTRATIONS ON REDUCTIVE DECHLORINATION RATES OF TCE AT A SULFIDOGENIC GROUND WATER/SURFACE WATER INTERFACE

J.M. Lendvay and P. Adriaens, Environmental and Water Resources Engineering, The University of Michigan, Ann Arbor, MI, 48109-2125

Iron- and sulfate-reduction have been shown to be the predominant terminal electron-accepting processes at the interface between a trichloroethene (TCE) contaminated aquifer and Lake Michigan at the St. Joseph, Michigan, NPL site. Our current research is aimed at evaluating the effect of electron donor and acceptor concentrations on sulfate-reduction and reductive dechlorination rates of TCE under sulfate-reducing conditions at this interface.

Batch microcosms consisting of sediment and ground water from the ground water/surface water interface are amended with 1.0 mM TCE in addition to an energy source and electron acceptor. Concentrations of energy source and electron acceptor are varied to evaluate resulting kinetic effects on the reductive dechlorination of TCE. Specifically, this study utilizes lactate as an energy source (0.2 mM to 2.0 mM) while sulfate concentrations are maintained in excess. Similarly, sulfate concentrations are varied between 0.2 mM and 2.0 mM while maintaining lactate concentration in excess. This experimental approach simulates in situ subsurface conditions as soluble sulfate concentrations range from 0.2 mM to 1.25 mM, and available electron equivalents of COD are in the mg/kg (sediment) range. Additionally, soluble hydrogen gas is measured to evaluate the transition to hydrogen as an election donor. Preliminary results have shown reductive dechlorination of tetrachloroethene (PCE) to vinyl chloride (VC) under sulfidogenic conditions using sediment and ground water from this same ground water/surface water interface.

Key words: sulfate reduction, reductive dechlorination, bioremediation.

Poster presentation in R2D2 session.

114 • SORPTION OF PHENANTHRENE BY NATURAL AND SYNTHETIC ORGANIC MATRICES

E.J. LeBoeuf, W. Huang, and W.J. Weber, Jr., Department of Civil and Environmental Engineering, The University of Michigan, Ann Arbor, MI, 48109-2125

It has long been recognized that the natural organic matrices (NOM) of soils, sediments, and aquifer materials play a major role in the fate and transport of organic contaminants in subsurface systems. Processes involving the slow sorption of organic solutes onto and into these matrices and subsequent hysteretic desorption from them are believed to be principally responsible for the failure of conventional pump-and-treat remediation technologies. Although a clear understanding of the characteristics of natural organic matrices has not yet been achieved, increasing evidence indicates the presence of two primary domains, one consisting of a relatively labile, swollen, rubber-like phase, and the other a resistant, condensed, glass-like phase, similar to the rubbery and glassy thermodynamic states of synthetic organic polymers. In this study, sorption of phenanthrene on natural and synthetic organic matrices was conducted to ascertain the influence each of these domains has on sorption capacity and linearity.

Our hypothesis contends that soil organic matrices (SOM) are composed of components of each of these domains, and that the rubbery-like domain is primarily responsible for the partitioning behavior evidence by linear isotherms, with the more condensed SOM largely controlling the adsorption behavior evidenced by nonlinear isotherms. This hypothesis is further supported by the dual-mode sorption behavior of synthetic organic polymers. The dual-mode model assumes the presence of a partitioning domain and a Langmuir adsorption domain within a glassy polymer. However, as a glassy polymer transcends to a more rubbery state through swelling or increased temperature, the Langmuir adsorption sites are replaced by a larger partitioning domain, ultimately resulting in a completely rubbery polymer, leaving only a partitioning domain and completely linear isotherm behavior.

The hypothesis was tested by sorbing phenanthrene in aqueous suspensions of natural and synthetic organic matrices at 5ºC and 25ºC. Natural sorbents included a soil humic acid, two kerogens from shales, and two coals. Synthetic sorbents included a number of poly(methacrylates) exhibiting a range of glassy to rubbery thermodynamic states.

Results of this study support our hypothesis. As expected, the rubbery poly(methacrylates) showed linear isotherms at all temperatures, while the more glassy polymers showed highly nonlinear behavior at the lower temperature, and decreased nonlinearity at the higher temperature. Swollen humic acids in aqueous solution behaved similarly to rubbery polymers, exhibiting almost pure partitioning at both temperatures, whereas the more condensed kerogens and coals are significantly more nonlinear, exhibiting a larger Langmuir adsorption domain at the lower temperature compared to the higher temperature.

Key words: sorption, remediation, soil, aquifer.

Poster presentation in R2D2 session.

115 • FOURIER TRANSFORM INFRARED SPECTROSCOPIC AND ELLIPSOMETRIC STUDIES OF EXOPOLYSACCHARIDE AND BIOFILM ATTACHMENT ON SILICA

D.A. Buttry¹, S.J. Clay¹, J.P. Turner², and L.A. Bulla³, ¹Department of Chemistry, ²Department of Civil Engineering, and ³Department of Molecular Biology, University of Wyoming, Laramie, WY, 82070

Biofilms are being investigated as a potential barrier to hazardous materials. These biofilms are comprised of microcolonies containing bacteria and exopolysaccharides (EPS). This EPS is thought to mediate adhesion of the bacteria to minerals surfaces. With this biofilm, an initially porous soil matrix can become very impermeable, effectively producing a barrier. In this study, Fourier transform infrared spectroscopy (FTIR) and ellipsometry were used to monitor the growth rate and attachment of a Beijerinckia indica biofilm to a silicon dioxide (quartz) substrate. By monitoring absorption bands previously attributed to exopolysaccharides, the accumulation of the EPS on the silicon dioxide substrate could be studied. In conjunction with the FTIR measurements, ellipsometry was used to determine the thicknesses of the biofilm and EPS.

Key words: biofilm, exopolysaccharides, bacterial adhesion.

Poster presentation in R2D2 session.

116 • PROPOSED STUDIES IN SURFACTANT-ENHANCED BIOREMEDIATION OF ORGANIC CONTAMINANTS

J.A. Mitzel, R.A. Doughten, R.E. Macur, H.M. Gaber, and W.P. Inskeep, Plant, Soil, and Environmental Sciences Department, Montana State University, Bozeman, MT, 59717

The bioavailability of nonpolar organic compounds (NOCs) in soils will influence the rate at which bioremediation will occur. The use of surfactants to enhance the apparent bioavailability is currently being reviewed to determine if this is a viable method for bioremediation of sites contaminated with NOCs. Presently, we are conducting research on the use of surfactants for enhancing biodegradation and transport of NOCs in soils. To date, we have found limited success enhancing biodegradation rates, but show dramatic increases in surfactant-enhanced solute transport. Our future research will concentrate on the influence of surfactant chemistry on the enhanced solubility of NOCs such as phenanthrene and pentachlorophenol, and the subsequent biodegradation of these compounds. The effect of nonaqueous-phase liquids (NAPLs) on surfactant-enhanced bioremediation and the effect of known phenanthrene degraders on sites containing NAPLs will also be studied. The information gained from this future research will help provide information concerning remediation strategies using surfactants.

Key words: bioremediation, bioavailability, nonaqueous phase liquids, nonpolar organic compounds.

Poster presentation in R2D2 session.

117 • FENTON OXIDATION TO REMEDIATE RDX-CONTAMINATED WATER AND SOIL

E.L. Bier, S.D. Comfort, and P.J. Shea, Department of Agronomy, University of Nebraska, Lincoln, NE, 68583-0915

Some soils at the former Nebraska Ordnance Plant (NOP) and other military installations are highly contaminated with cyclonite (RDX) as a result of past waste management practices. Since RDX is mobile in soil and recalcitrant at high concentrations, these sites may require remediation to reduce potential health and environmental hazards resulting from contamination of water supplies. Conventional treatment by incineration is very costly and often creates strong public opposition. We propose an alternative treatment using the Fenton reagent (Fe²⁺ + H₂O₂) to remediate RDX-contaminated water and soil. Treating an aqueous solution of RDX (35 mg l^-1) with the Fenton reagent resulted in complete RDX destruction within 24 h. Mass balance experiments with ¹⁴C-RDX indicated 75 to 85% was lost as ¹⁴CO₂, while 10% was lost as volatile ¹⁴C organic compounds. After 24 h of Fenton oxidation, end products include NH₄⁺, NO₃^-, and formic acid. An additional ¹⁴C degradation product found in solution is being isolated for identification. Results from Fenton oxidation of RDX-contaminated soil from the NOP site will also be reported.

Key words: RDX, Fenton oxidation, remediation.

Poster presentation in R2D2 session.

118 • OVERVIEW OF KANSAS EPA EPSCoR PROJECTS

R. Peat and A.P. Schwab, Kansas State University, Agronomy Department, Throckmorton Hall, Manhattan, KS, 66506

The Experimental Program to Stimulate Competitive Research (EPSCoR) is a program for states under-funded in the national research arena. Kansas EPA-funded EPSCoR projects are a focused effort to enhance bioremediation research by giving young scientists the opportunity to become part of a state-wide team. The universities involved in this team effort are Kansas State University, the University of Kansas, and Wichita State University.

This poster presentation will provide an overview of three Kansas EPA EPSCoR projects. These projects examine (1) the bioremediation of petroleum hydrocarbons in the subsurface environment, (2) the use of vegetation to stabilize and remediate sites contaminated with heavy metals, and (3) the role of methanotrophic bacteria in remediation of surface aquatic environments.

Key words: bioremediation, EPSCoR, heavy metal, hydrocarbons, ground water quality, surface water quality, soil.

Poster presentation in R2D2 session.

119 • THE EFFECTS OF THE RHIZOSPHERE ON THE OXIDATION STATE OF CHROMIUM IN SLUDGE-AMENDED SOILS

C.T. Henderson, M.K. Banks, and A.P. Schwab, Kansas State University, Manhattan, KS, 66502

The effect of plant root interactions with chromium sludge-amended soils on the mobility of chromium will be assessed to quantify the change in oxidation state and distribution of chromium in the soil profile. Effects of pH and soil and rooting depth will be determined. This study will evaluate the effectiveness of using plant roots to change the oxidation state of chromium in contaminated surface soil.

Key words: chromium, mobility, adsorption, contamination, soil, heavy metal.

Poster presentation in R2D2 session.

120 • COMETABOLISM OF TRICHLOROETHENE (TCE) IN FLUIDIZED-BED BIOREACTORS

R.L. Segar, Jr., S.A. Vivek, K. Leung, P. Kalia, K.L. Bauman, and J.R. Foeller, Department of Civil Engineering, University of Missouri-Columbia, Columbia, MO, 65211

The development of fluidized-bed bioreactors (FBBRs) for the treatment of water contaminated with chlorinated solvents offers a promising alternative to existing treatment technologies. The objectives of this research are to develop two different fluidized-bed reactors, a conventional single-pass reactor and an innovative draft-tube reactor, for the removal of trichloroethene (TCE) from ground water and to understand how the design of each reactor type affects the TCE removal. Phenol was selected as the growth substrate for activated sludge microorganisms because it induces enzymes with the ability to cometabolize TCE and its daughter products.

Experiments with the conventional reactor have focused on the effect of TCE loading, phenol loading, detention time, and pulsed feeding techniques. Preliminary studies included fluidization studies with various filter sand types and grades, aeration studies with a downflow-bubble-contactor, conductivity tracer studies, TCE abiotic loss rate studies, and batch TCE degradation studies. Results of these studies are being used to develop a basic design approach for cometabolizing bioreactors and a detailed, non-steady-state model of biofilm reactors fed multi-component mixtures of toxic organics.

Sand was selected as the attached media for the conventional FBBR, which had dimensions of approximately 5 cm diameter and 100 cm of bed depth. At a flow rate of 0.8 l/min, the continuous-flow TCE removals indicated that the proper level of phenol feeding was essential for obtaining high TCE removal. A phenol to TCE mass ratio of 50:1 provided 70-80% removal of 0.1 mg/l TCE at an EBCT of 3 minutes. Phenol was not detected in the reactor effluent at those conditions. Subsequent studies with TCE-amended ground water addressed means to improve TCE removal by increasing the reactor length, using denser media, and optimizing the phenol feeding rate. The performance of the FBBR for TCE removal was superior to other types of biological reactors reported in the literature.

Key words: biofilm, fluidized-bed, trichloroethene, phenol, ground water remediation.

Poster presentation in R2D2 session.

121 • MIXING AND AGITATION IN SLURRY REACTORS FOR BIOREMEDIATION

M. Farraro, R.K. Bajpai¹, G.W. Preckshot, and S.K. Banerji, University of Missouri-Columbia, W2030 EBE, Columbia, MO, 65211, ¹e-mail: chenrkb@showme.missouri.edu

Slurry bioreactors for environmental restoration have particles of sizes from microns to several millimeters, difficult suspension characteristics, low to moderate mass transfer needs, long-term operation, and tight economical constraints. This presentation will deal with a review of the state-of-the-art for mixing and agitation of slurries for bioremediation niche. The correlations relating power supply, agitation, and mass transfer will be summarized and compared. Soil applications will be explored, and missing information will be identified.

Key words: mass transfer, design, scale-up, soil, biorestoration.

Poster presentation in R2D2 session.

122 • THE INFLUENCE OF PHOSPHORUS ON CHEMICAL AND MINERALOGICAL PROPERTIES OF A ZINC/LEAD SMELTER SLAG

M. Lambert¹ and G.M. Pierzynski², ¹Department of Geology and ²Department of Agronomy, Kansas State University, Manhattan, KS, 66506

For many years, zinc and lead ore from the Tri-State region was processed in a smelter near the village of Dearing, in Montgomery County, southeastern Kansas. Although the smelter is no longer in operation, remediation of the slag produced as a waste product by the smelter is a matter of ongoing environmental concern. X-ray diffractometry was used to determine the mineralogical composition of untreated slag and slag to which phosphate was added in the form of fertilizer. The most noticeable difference between the two is that orthoclase (potassium feldspar) and potassium lead phosphate that is present in the untreated slag is absent or present in reduced quantities in the treated slag. Pyromorphite (lead orthophosphate) is present in both, and lead released by the dissolution of the potassium lead phosphate may be precipitating as additional pyromorphite.

Key words: Tri-State region, zinc ore, lead ore, slag, potassium lead phosphate, pyromorphite.

Poster presentation in R2D2 session.

123 • COMPUTER SIMULATION OF THE EFFECT OF VEGETATIVE REMEDIATION OF SOILS-PROPOSED WORK

W. Guinn, B. Hankley, L.E. Erickson, R.S. Govindaraju, and G.M. Pierzynski, Kansas State University, Manhattan, KS, 66506

This work will be in support of the Vegetative Interceptor Zones for Containment of Heavy Metal Pollutants project. One of the goals of this project is the development of a physically based model of surface movement of heavy metals in the presence of vegetation/interceptor strips. The main goal of this work is the development of a tool which would be useful to civil and chemical engineers in studying the transport of heavy metals. This tool would use mathematical models developed by Dr. Govindaraju and others. The mathematical model would be verified using field data developed by Dr. Pierzynski and others. One initial step is to take a look at what graphical simulations have already been developed and what kind of interfaces have been used. Potential users of this tool will be asked for help in developing requirements to be used in writing specifications, including preferred platform. User friendliness will be emphasized for easy use. Key areas of modeling include surface and subsurface modeling such as 2-D overland (water) flow, 2-D soil erosion (sediment), and 2-D heavy metal transport (solute). Initial work will start simulation in one horizontal direction. Ultimately, the simulation will provide top, side, and 3-D views with user-provided inputs for such variables as: field slope, crop (soil cover), rate of rainfall, duration of rainfall, size of raindrop, impact action of rain, distance between buffer strips, size of sediment, subsurface loss (infiltration), size of watershed, and type of soil. Outputs of the simulation would be heavy metal concentrations and locations.

Key words: computer simulation, vegetative remediation, soil, heavy metal.

Poster presentation in R2D2 session.

124 • SOIL FLUSHING OF HEXACHLOROBENZENE USING SURFACTANT AND COLLOIDAL GAS APHRONS IN A TWO-DIMENSIONAL SYSTEM

M.L. Smith, Hazardous Substance Research Center, Louisiana State University, Baton Rouge, LA, 70803

In situ soil flushing with surfactant solution, an enhanced pump-and-treat process, were examined in this study. The study employed water, surfactant solution, and colloidal gas aphron suspensions as discrete carriers for the contaminant. Colloidal gas aphron suspensions were generated using the surfactant solution. The target contaminant was hexachlorobenzene (HCB). The removal efficiency and mobilization of the contaminant were investigated using a two-dimensional cell containing either a homogeneous, contaminated sand bed or an uncontaminated sand bed with a contaminated soil core. A few different types of surfactants were used in the study. The system attempted to model conditions possibly encountered at hazardous waste sites when flushing with water and/or surfactants to better predict performance in the field.

Key words: soil washing, soil flushing, surfactants, colloidal gas aphron, remediation.

Poster presentation in R2D2 session.

125 • DETERMINING SOIL CONTAMINANTS USING NEUTRON ACTIVATION AND GAMMA-RAY SPECTROSCOPY

J. Monzon and D. Heckathorn, TRIGA Mark II Nuclear Reactor Facility, Kansas State University, Manhattan, KS, 66506

Soil samples were obtained from mining sites in Kansas and Montana. Soil contaminants were investigated through the use of neutron activation and gamma-ray spectroscopy. The spectroscopy results obtained from these results were compared with spectroscopy results from chemical standards, which were prepared at Kansas State University. A comparison between the count rates of the soil samples and the chemical standards was conducted to provide quantitative results. This comparison led to a better understanding of the types and concentrations of contaminants in the soil samples.

Key words: neutron activation, gamma-ray spectroscopy, soil contaminants.

Poster presentation in R2D2 session.

126 • CONSTRUCTION OF CHLOROBIPHENYL DEGRADATION PATHWAY IN GRAM + BACTERIUM RHODOCOCCUS ERTHREUS STRAIN NY05

R.R. Helton Coll, T.V. Tsoi, J.F. Quensen III, and J.M. Tiedje, NSF Center for Microbial Ecology, Michigan State University, East Lansing, MI, 48824

Biphenyl-degrading Gram + bacteria Rhodococcus erythreus strain NY05 is able to co-metabolize a wide range of PCB congeners yielding corresponding chlorobenzoates. That makes this organism an attractive model for construction of PCB-degradative recombinant pathways in order to obtain bacteria growing on PCBs.

We have constructed shuttle vehicle pRT1, which stably maintains in both Gram - bacteria and R. erythreus, and confers host cells resistance to tetracycline. Using pRT1 plasmid as a cloning vector, we have constructed recombinant plasmid pRHD carrying Arthrobacter globiformis fcbABCD operon controlling hydrolytic para-dechlorination of chlorobenzoates. Plasmid pRHD was transferred into R. erythreus NY05 using electrotransformation.

Expression of fcbABCD operon currently is under investigation.

Key words: polychlorinated biphenyls, Rhodococcus, degradation, shuttle vector, gene-cloning.

Poster presentation in R2D2 session.

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ABSTRACTS HSRC/WERC Joint Conference on the Environment 1996

Program One Tuesday, May 21, 1996 Metals · Tampico Room

1 • REMEDIATION OF LEAD CONTAMINATED SOIL WITH EDTA: BATCH AND COLUMN STUDIES

2 • CHELATING EXTRACTION AND RECOVERY OF HEAVY METALS FOR REMEDIATION OF CONTAMINATED SOIL

3 • DEVELOPMENT OF NOVEL AND COST EFFECTIVE POLYMERIC CHELATORS FOR APPLICATIONS IN RADIOACTIVE ACTINIDE WASTE REMEDIATION

4 • BIOSORPTION OF CADMIUM, CHROMIUM, LEAD, AND ZINC BY BIOMASS OF MEDICAGO SATIVA (ALFALFA)

5 • HEAVY METAL SPECIATION AND UPTAKE IN CRAYFISH AND TADPOLES

6 • SPECIATION STUDIES AND TOXICITY ASSESSMENT OF COMPLEX HEAVY METAL MIXTURES

7 • BIOREMEDIATION IN THE GEL BARRIER USING IMMOBILIZED YEAST FOR HEAVY METAL REMOVAL

8 • UPTAKE OF METAL IONS FROM SOLUTION BY INACTIVATED CELLS OF SYNECHOCOCCUS PCC 7942 (CYANOBACTERIA)

9 • MICROBIAL REDUCTION OF URANIUM USING CELLULOSIC SUBSTRATES

10 • REMOVAL AND RECOVERY OF COPPER AND CADMIUM BY AEROBIC MICROBIAL CULTURES GROWN WITH BIOPOLYMER STIMULATORS

Program One Wednesday, May 22, 1996 Metals · Tampico Room

11 • BIOREDUCTION OF HEXAVALENT CHROMIUM IN BATCH CULTURES USING INDIGENOUS SOIL MICROORGANISMS

12 • MOBILE CHROMATE TO IMMOBILE PRECIPITATE-SUBSURFACE REACTIVE WALL SCENARIOS

13 • REMEDIATION OF CHROMATE-CONTAMINATED GROUND WATER USING ZERO-VALENT IRON: FIELD TEST AT USCG SUPPORT CENTER, ELIZABETH CITY, NORTH CAROLINA

14 • CALCIUM AND MAGNESIUM INTERFERENCE STUDIES FOR THE BINDING OF HEAVY METAL IONS IN SOLUTION BY MEDICAGO SATIVA (ALFALFA)

15 • THE EFFECT OF VEGETATION ON THE TRANSPORT OF HEAVY METAL IN A CONTAMINATED SOIL: A COLUMN STUDY

16 • APPLICATIONS OF PERMEABLE BARRIER TECHNOLOGY TO GROUND WATER CONTAMINATION AT THE SHIPROCK, NM, UMTRA SITE

17 • AN ELECTROCHEMICAL APPROACH FOR INVESTIGATING CORROSION OF SMALL ARMS MUNITIONS IN FIRING RANGES

18 • THE TRANSPORT OF ZINC IN SOIL AS AFFECTED BY CITRATE

19 • A COMPUTER MODEL FOR REMOVAL OF LEAD FROM CONTAMINATED SOILS

20 • ON CONDUCTIVITY OF SOILS WITH PREFERENTIAL FLOW PATHS

21 • MODELING HEAVY METAL MOVEMENT IN A ROOTED SOIL

22 • EFFECT OF VEGETATION ON CONTAMINANT TRANSPORT IN SURFACE FLOWS

23 • UNSATURATED POROUS MEDIA FLOWS ABOUT NON-PARTICIPATING FRACTURES

Program One Thursday, May 23, 1996 Munitions-Contaminated Soil · Tampico Room

24 • TNT BREAKTHROUGH CURVES FOR AQUIFER MATERIALS FROM THE LOUISIANA ARMY AMMUNITION PLANT, SHREVEPORT, LA

25 • PEROXONE TREATMENT OF EXPLOSIVES-CONTAMINATED GROUND WATERS

26 • FEDERAL INTEGRATED BIOTREATMENT RESEARCH CONSORTIUM: FLASK TO FIELD

27 • SCREENING FOR REMOVAL OF TNT AND RDX BY SUBMERSED AND EMERGENT PLANT SPECIES FROM CONTAMINATED GROUND WATER

28 • BIOREMEDIATION OF SOLID TNT PARTICLES IN A SOIL SLURRY REACTOR: MASS TRANSFER CONSIDERATIONS

29 • PHYTOREMEDIATION OF TNT-CONTAMINATED WATER: BENCH-TOP FLOW THROUGH REACTOR STUDIES

Program Two Tuesday, May 21, 1996 Chemical Technologies · Cozumel Room

30 • CARBON TETRACHLORIDE DECHLORINATION IN WATER USING BINARY METAL SYSTEMS

31 • DECHLORINATION OF TRICHLOROETHYLENE BY ZERO-VALENT METALS IN AQUEOUS ENVIRONMENTS

32 • DECHLORINATION OF CARBON TETRACHLORIDE WITH IRON: CARBON MASS BALANCE AND EFFECT OF OXYGEN ON DECHLORINATION PATHWAYS

33 • CHLOROFORM TRANSFORMATION BY A METHANOGENIC CONSORTIUM UTILIZING ZERO-VALENT IRON AS ULTIMATE ELECTRON DONOR

34 • DESTRUCTIVE ADSORPTION OF CHLOROCARBONS ON CALCIUM OXIDE

35 • DESTRUCTIVE ADSORPTION OF 2-CHLOROETHYL ETHYL SULFIDE BY MAGNESIUM OXIDE

36 • EFFECT OF REDOX ENVIRONMENT ON OXIDATION OF PENTACHLOROPHENOL WITH MANGANESE OXIDE

37 • PHOTOCATALYTIC DEHALOGENATION OF CHLORINATED COMPOUNDS WITH 2-PROPANOL AND ACETONE AS SOLVENTS

38 • ACCELERATED PHOTODEGRADATION OF AROMATIC COMPOUNDS WITH HYDROGEN PEROXIDE IN AN EMBEDDED TITANIUM OXIDE REACTOR

39 • DESTRUCTIVE ADSORPTION OF ENVIRONMENTAL TOXINS UTILIZING CALCIUM OXIDE AND TRANSITION METAL OXIDE-SUPPORTED CALCIUM OXIDE NANOPARTICLES

Program Two Wednesday, May 22, 1996 Chemical Technologies · Cozumel Room

40 • USING FERRATE TO REMOVE HYDRAZINES FROM WASTE WATER

41 • REVIEW OF THE GALVANIC STRIPPING PROCESS FOR USE IN TREATING OXIDIZED METAL WASTES

42 • DEVELOPMENT OF POLAROGRAPHIC FIELD SENSORS FOR HEAVY METAL DETECTION

Technology Transfer and Analytical Methods · Cozumel Room

43 • IMPROVED HYDROCARBON DETECTION

44 • IDENTIFICATION OF PENTACHLOROPHENOL IN ALLUVIAL SOILS UTILIZING IMMUNOASSAY FIELD METHODS, GRAND TETON NATIONAL PARK, WYOMING-A CASE STUDY

45 • POLLUTION PREVENTION AND MICROSCALE CHEMISTRY IN THE RESEARCH LABORATORY

Technology Transfer and Munitions-Contaminated Soils · Cozumel Room

46 • SOLIDIFICATION/STABILIZ-ATION OF METALS AND EXPLOSIVES IN SOIL

47 • FIELD DEMONSTRATION OF ON-SITE ANALYTICAL METHODS FOR TNT AND RDX IN GROUND WATER

48 • FIRST PRODUCTION-LEVEL BIOREMEDIATION OF EXPLOSIVES-CONTAMINATED SOIL IN THE U.S.

Technology Transfer and Field Applications · Cozumel Room

49 • FIELD UP-SCALING OF PROCESSES ASSOCIATED WITH BEHAVIOR OF NONAQUEOUS PHASE WASTE CHEMICALS IN HETEROGENEOUS AQUIFERS

50 • MINE RECLAMATION AND RESIDUAL WASTES

51 • GRAY DAUN URANIUM MINE REMOVAL ACTION, SAN JUAN COUNTY, UTAH

52 • ROLE OF CARBONATION IN LONG TERM PERFORMANCE OF CEMENTITIOUS WASTEFORMS

Program Two Thursday, May 23, 1996 Technology Transfer and Field Applications · Cozumel Room

53 • MANAGING THE PUMP-AND-TREAT END GAME

54 • DESIGN CONSIDERATIONS OF VERTICAL VERSUS HORIZONTAL WELL CONFIGURATIONS FOR AIR SPARGING/SOIL VAPOR EXTRACTION REMEDIATION SYSTEMS

55 • POLLUTION PREVENTION ASSESSMENTS FOR MARINE MAINTENANCE AND CONTAINER PRINTING INDUSTRIES

Technology Transfer and Training · Cozumel Room

56 • SUPERFUND SCIENTISTS TEACH MINORITY HIGH SCHOOL STUDENTS SCIENTIFIC LITERACY AND CAREER DEVELOPMENT IN NOVEL YEAR-ROUND PROGRAM TIED TO SUPERFUND INVESTIGATIONS

57 • RAD WORLD/TV EARTH ENVIRONMENTAL VIDEOS

58 • NATIVE AMERICAN ENVIRONMENTAL ISSUES: PUEBLO SUPERFUND PROGRAM

Program Three Tuesday, May 21, 1996 Organic Contaminants · Coronado Room

59 • OPTIMIZATION OF CONTAMINANT REMOVAL FOR HETEROGENEOUS SYSTEMS BY SOIL VENTING

60 • REMOVAL OF HYDROCARBONS FROM CONTAMINATED WATER USING AIR-SPARGED HYDROCYCLONE TECHNOLOGY

61 • MATHEMATICAL MODELS FOR BIODEGRADATION OF CHLORINATED SOLVENTS

62 • SURFACTANT-ENHANCED TRANSPORT OF HYDROPHOBIC ORGANIC COMPOUNDS

63 • SOLVENT EXTRACTION FOR REMEDIATION OF SOILS AT WOOD TREATMENT SITES

64 • SURFACTANT-ENHANCED DISSOLUTION OF NONAQUEOUS PHASE LIQUIDS IN SANDY AQUIFER MATERIALS-EFFECTS OF DIMENSIONALITY AND SCALE

Barriers and Transport · Coronado Room

65 • CONTAINMENT OF HEAVY METAL AND CHLORINATED ORGANIC SOLVENT CONTAMINATION USING SUBSURFACE BIOBARRIERS

66 • BIOFILM BARRIERS IN SOIL

67 • THE EFFECT OF ULTRA PURE WATER FLUSHING ON BACTERIAL TRANSPORT IN NATURAL SEDIMENTS

ABSTRACTS
HSRC/WERC Joint Conference on the Environment 1996

Program One
Tuesday, May 21, 1996
Metals · Tampico Room

Program One
Wednesday, May 22, 1996
Metals · Tampico Room

Program One
Thursday, May 23, 1996
Munitions-Contaminated Soil · Tampico Room

Program Two
Tuesday, May 21, 1996
Chemical Technologies · Cozumel Room

Program Two
Wednesday, May 22, 1996
Chemical Technologies · Cozumel Room

79 • PHOTOCATALYTIC DEGRADATION OF PCBs IN AQUEOUS TiO₂ SUSPENSIONS