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/stabi

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

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