A WATER BALANCE MODEL OVER SOILS WITH SPATIALLY VARYING INFILTRATION PROPERTIES

A water balance study was conducted at an agricultural and a pristine site on the Konza Prairie research area. The hydrologic variables of interest were precipitation, surface runoff, evapotranspiration, infiltration and soil water content. Surface infiltration properties were measured at 40 locations over each site. Spatial variability of these properties was incorporated into compution of areally averaged infiltration rates. The water budget model was used to predict average soil water contents. These were compared with measured values for model evaluation.

Keyword(s): infiltration, spatial variability.

Poster presentation.

The use of vegetation at waste sites is a logical approach to improving microbial degradation of xenobiotics by overcoming some of the inherent limitations to biological cleanup approaches such as low microbial populations or inadequate microbial activity. Plants are known to influence soil microorganisms in positive ways by exuding organic substances into the root zone and providing a microhabitat conducive to proliferation. Previous research has demonstrated that rhizosphere soils or microorganisms isolated from rhizosphere soils often exhibit accelerated rates of xenobiotic metabolism, suggesting that plants might be valuable as a cost-effective approach for biological remediation of waste sites.

An area where cost-effective approaches to remediation are in particular need is retail agrochemical dealer sites. Many of these dealerships have experienced soil and water contamination problems from normal operating procedures and accidents during the last 40 years. In most instances, the costs associated with current cleanup technologies preclude their use at these facilities.

A potential limitation to using vegetation exists at these sites because of the presence of mixtures of herbicide contaminants at concentrations several-fold above the field application rate. Nonetheless, herbicide-tolerant and herbicide-resistant plants, including kochia (Kochia scoparia), barnyardgrass (Echinochloa crus-galli) and pigweed (Amaranthus retroflexus) routinely inhabit these environments. Previously, we demonstrated that the degradation of atrazine, metolachlor and trifluralin was significantly greater in rhizosphere soils from Kochia scoparia than in nonvegetated soils. In addition, mineralization of 14C- atrazine in a mixture of atrazine and metolachlor (50 mg/g each) was significantly greater in Kochia scoparia rhizosphere soils than nonvegetated soils. In both studies, soils were collected from retail agrochemical dealer sites where mixtures of herbicides were present in the soil at concentrations several-fold above the field application rate. In addition, rhizosphere soils from other plant species were tested for their ability to mineralize atrazine or metolachlor at concentrations typical of point-source contamination (50 mg/g). Several rhizosphere soils tested positive for 14C-atrazine mineralization (³ 8.5%) including lambsquarters (Chenopodium berlandieri), foxtail barley (Hordeum jubatum), witchgrass (Panicum capillare), catnip (Nepeta cataria) and musk thistle (Carduus nutans). These results suggest that plants might be managed at pesticide- contaminated sites to help facilitate microbial degradation of wastes in soils.

Keyword(s): rhizosphere, bioremediation, atrazine, vegetation.

Poster presentation.

Soil hydraulic properties are needed for modeling water movement in soils. Past attempts at relating hydraulic properties to easily measurable quantities like pore size distribution have relied on empirical and semi-empirical relationships. This study proposes to use Artificial Neural Networks (ANNs) for predicting soil hydraulic properties (hydraulic conductivity, saturated water content and the alpha parameter of Gardner's relationship) from percentages of sand, silt and clay and bulks density of the soil. The backpropagation algorithm is used for this purpose. The performance of ANNs will be compared with some existing models.

Keyword(s): soil hydraulic properties, particle size distribution, neural networks, backpropagation algorithm.

Oral presentation in environmental assessment and decision making session.

The presence of vegetation has been demonstrated to increase the biodegradation of several classes of organic compounds. Polycyclic aromatic hydrocarbons (PAHs) are highly recalcitrant and hydrophobic contaminants. Once incorporated into the soil, biodegradation seems to be the most effective means of remediation. Laboratory experiments were conducted to evaluate the mineralization of PAHs (pyrene and phenanthrene) in the rhizosphere due to cometabolism and assess their fate in the rhizosphere of several species of grasses and legumes. The mechanism of cometabolism was tested by adding phenanthrene to soil containing 14C-pyrene. The cometabolic environment induced due to phenanthrene resulted in an increased generation of 14CO2 especially in the rhizosphere soil with organic acids. The dissipation of 14C- phenanthrene in various rhizosphere soils was assessed for mineralization, volatilization and residual 14C in soil. Mineralization was significantly greater in the warm season grasses, sorghum (Sorghum bicolor L.), bermuda grass (Cynodon dactylon L.) and the legume soybean (Glycene max L.) compared to soil from alfalfa (Medicago sativa L.) which did not differ from control soil. It was found that a large portion of the biodegraded 14C- phenanthrene was incorporated into soil organic matter either as microbial biomass or degradation products.

Keyword(s): biodegradation, PAH, rhizosphere, cometabolism.

Poster presentation.

A common environmental problem associated with the pumping and refining of crude oil is contamination of soil with petroleum products. Vegetation may play an important role in the biodegradation of petroleum contaminants in soil. The establishment of vegetation may be an economical, effective, low maintenance approach to remediation and stabilization. The use of plants for remediation may be especially well-suited for soils contaminated to depths of less than 2 meters. In this project, several petroleum contaminated field sites have been chosen in collaboration with industrial partners. These sites have been thoroughly characterized for chemical properties, physical properties and initial TPH concentrations. A variety of plant species have been established on two of the sites. Soil analyses for target compounds over time will be reported. Results from this study will allow us to assess the efficiency and applicability of this remediation method.

Keyword(s): bioremediation, vegetation, petroleum, biodegradation, rhizosphere.

Poster presentation.

The design of a “washing” process for the removal and recovery of toxic metals from contaminated soil requires in-depth knowledge of the speciation of the metals. In addition to being present in their original forms (e.g. oxides particulates emitted by a smelter), the contaminating metals may come to be associated with a variety of solid phases commonly present in the soil. A sequential chemical extraction procedure has been used to characterize lead and cadmium speciation in soil collected in the vicinity of a zinc smelter that was in operation for 70 years.

Keyword(s): soil, lead, cadmium, speciation.

Poster presentation.

The Waste-Management Education and Research Consortium (WERC) was formed four years ago for the purpose of developing human and technological resources that can address issues related to the environment and the management of waste. For the past four years, WERC has supported development of innovative technologies proposed by researchers from the academic institutions, in partnership with researchers from national laboratories and industrial partners. Researchers from four universities in New Mexico have teamed with Sandia National Laboratories, Los Alamos National Laboratory and industrial partners to develop over 50 advanced technologies. Several of these have moved to field application. One such project is the development of a unique system that detects and provides a 3-D display of buried waste from sites. This system is now in the commercial stage and assists industrial and national laboratories such that remediation can proceed in a safe and economical manner. Another project involves application of bioremediation and other chemical techniques to the Uranium Mill Tailings Remediation Act project of the U.S. Department of Energy (DOE). A third project in partnership is a Petroleum Organizational in the process of application of a technique using tailored zeolites to absorb organic contaminance from ground water. This system is under application at refinery and production operations. Another major application uses advanced monitoring technologies to totally monitor the soil, air, water, humans, flora and fauna around a nuclear repository.

These are just examples of some of the technologies developed by the partnership. We have gone beyond the theoretical or the laboratory stages and are now at applications stages contributing to the safety and cleanup of our environment at government and industrial sites. In addition to the technological impact, these are making a real contribution to the education of students who are involved in the development. Students gain real life experience which can assist them in their careers as environmental professionals. This paper will describe advanced technologicies as well as the system that has led to the successful application of technologies.

Keyword(s): remediation, site applications, advanced technologies.

Oral presentation in technology transfer session.

Poor waste management practices at munitions production facilities have contaminated surrounding soil and water with hazardous materials, particularly TNT (2,4,6-trinitrotoluene) and cyclonite (RDX, hexahydro-1,3,5-trinitro-1,3,5-triazine). Remediating these contaminated sites is necessary to ensure public safety. Soil cleanup by the conventional technique of incineration, however, is very expensive and often unacceptable to the public. Cost- effective and environmentally acceptable remediation treatments are needed. We determined the efficiency of an abiotic oxidative treatment (Fenton oxidation) and a reduction treatment (metal reduction) for remediating RDX-contaminated soil.

Oxidation experiments evaluated the effects of H2O2, Fe2+, and initial RDX concentrations, UV light, and contaminated soil extracts on rates of RDX transformation and mineralization. Treating an aqueous solution of 20 mg 14C-RDX L-1 in the dark with Fenton reagent (1% H202 and 80 mg Fe2+ L-1) resulted in complete removal of RDX within 24 h. This coincided with 70 to 85% RDX mineralization. Similar results were found with aqueous extracts of RDX- contaminated soil. UV light enhanced both RDX transformation and mineralization rates. The metal reduction experiments were performed with elemental Zn or Fe in aqueous solutions of RDX, contaminated soil extracts and soil-slurries. Treating 40 mg L-1 14C-RDX with Zn (5:1 solution:metal ratio) resulted in complete destruction of RDX within 2 h. Higher transformation rates were generally observed at lower pH. Iron was also effective in reducing RDX in solution. Mineralization of RDX by Zn reduction was not observed. The metal reduction treatment was also effective in removing RDX from contaminated-soil extracts and soil-slurries. These results indicate that both abiotic oxidative and reductive treatments can effectively remediate RDX-contaminated soil and water.

Keyword(s): munitions, RDX, cyclonite, Fenton oxidation, remediation, metal reduction.

Poster presentation.

By virtue of their large surface area and high sorption potential, fine clay particles adsorb significant quantities of subsurface contaminants and may be considered particulate contaminants. Understanding the mobility of these particulate contaminants in porous media is essential to predict the contaminant transport in ground water. In a geoenvironmental engineering context, the mobility of the fine particles has recently been viewed as desirable in subsurface remediation. The stability of these particles depends on both physical and chemical effects induced through pore water flow. The combined effect of dynamics and composition of pore fluid may significantly alter the permeability and transport characteristics of the porous media. In this study, various hydraulic gradients were considered in a theoretical analysis to account for the effect of pore fluid dynamics on the mobility of the contaminants. Pore fluid characteristics such as ionic strength and valency were considered in the analysis by accounting for London-van der Walls attractive forces and electrical double-layer attractive or repulsive forces. The study addresses the interaction of forces at a microscopic level acting on individual clusters of particles to assess the significance of the two effects. Finally, the significance of the fine particle stability is assessed in light of the standard transport mechanisms (advection and diffusion).

Keyword(s): particulate contaminants, pore fluid, permeability, porous media, transport mechanism.

Oral presentation in fate and transport session.

An investigation of the chemical composition of mining and smelter wastes and the composition's effect on the bioavailability of lead, as predicted by geochemical modeling, will be presented. Chemical sequential extraction was used to quantify the different types of chemical bonding in the samples. X-ray analysis of the samples and their sand, silt and clay fractions was also performed. The results from these laboratory investigations were compared with geochemical modeling. Modeling predictions and laboratory results were similar.

Keyword(s): mining wastes, characterization, sequential extraction.

Oral presentation in heavy metals session.

New fuels and pollution solutions can be realized with cells on rotating fibers. Fibers have high area and when Celite is entrapped in the fibers, even more area is provided. Zymomonas can ferment glucose to ethanol in 15 minutes, and a recombinant version can ferment pentose sugars.

Zymomonas on Tyvek fiber removes lead from wastewater in two seconds. Some people think all bacteria are poisonous, but in Brazil scientists have found it to be therapeutic. Dried grain from a Zymomonas fermentation is generally recognized as safe (GRAS) for animal feed. Several large cities are over the limit for lead in drinking water. Other metals can be removed also.

Calcium magnesium acetate, a non- corrosive road deicer is made with cells on rotating fibers. Salt causes millions of dollars damage to roads and bridges. Inexpensive raw material such as cheese whey and corn steep liquor can be used. When a rotary biological contactor is run half full and a light shone in the top, the light hits a thin moving film. In other photo reactors, colored solution blocks the light. Light can degrade chlorine compounds and produce hydrogen, a non-polluting fuel. Rapid increase of CO2 threatens the very existence of mankind. Titania entrapped in the fiber increases the rate of the reaction. In a horizontal RBC, hydrogen has an easy exit, just like CO2 has an easy exit when fermenting sugar to alcohol.

White rot fungus grows on fibers like old cardboard boxes to degrade chlorine compounds, azo dyes and TNT. The corrugations entrap air which is necessary for growth of the fungi when buried in soil.

Keyword(s): ethanol, lead, deicer, hydrogen.

Poster presentation.

The investigation of past operational and disposal practices at federal facilities and formerly used defense sites (FUDS) has dramatically increased in the past several years. The manufacture, load, assembly and pack (LAP), demilitarization, washout operations, and open burn/open detonation (OB/OD) of ordnance and explosives has resulted in contamination of soils with munitions residues. The primary constituents are nitroaromatic and nitramine organic compounds, and heavy metals. A number of sites have soil contamination remaining where waste disposal practices were discontinued 20 to 50 years ago. In conjunction with site investigations, biological treatment studies have been undertaken to evaluate the potential for full scale remediation of organic contaminants. This paper evaluates the results of 15 bioremediation treatability studies conducted at eight sites for explosives contaminated soils, and discusses the full scale remedial implementation status. Five basic types of biological treatment processes have been evaluated, including: (1) composting, (2) anaerobic bioslurry, (3) aerobic bioslurry, (4) white rot fungus treatment, and (5) solid phase treatment. Representative bench and pilot scale studies were conducted using site-specific munitions residues to determine the ability to meet preliminary remediation goals (PRGs) or cleanup levels, and to identify issues related to scale-up of the technologies.

Composting has been selected as the full scale remedial action treatment remedy at two National Priority List (NPL) sites: (1) Umatilla Army Depot Activity, Hermiston, Oregon, for 15,000 tons of soil contaminated with TNT (2,4,6-trinitrotoluene), RDX (hexahydro-1,3,5-trinitro-1,3,5-triazine) and HMX (octahydro-1,3,5,7-tetranitro-1,3,5,7- tetrazocine), and (2) U.S. Naval Submarine Base, Bangor, Washington, for 2,200 tons of TNT-contaminated soils. Pilot scale composting treatability studies have demonstrated the ability to achieve risk- based cleanup levels of 30 to 33 parts per million (ppm) for TNT and 9 to 30 ppm for RDX after 40 days of treatment, with a destruction and removal efficiency (DRE) of greater than 99.0%. Feasibility Study (FS) estimates of treatment costs range from $206 to $766 per ton for quantities of 1,200 to 30,000 tons, 40% to 50% less than on- site incineration. In the past, all NPL sites with explosives contamination have used incineration as the selected treatment technology. Actual costs for biotreatment will be refined during full scale remediation.

Keyword(s): explosives, munitions, ordnance, bioremediation, biological treatment.

Oral presentation in technology transfer session.

Disagreement often exists between degradation rate constants obtained from batch degradation experiments and leaching experiments. Although degradation can be quantified successfully in a batch-type experiment, no satisfactory method exists for this purpose in a leaching experiment, apart from curve-fitting. During leaching, the simultaneous occurrence of sorption, dispersion and convection confounds the duration for which true degradation takes place within the soil. A correct description of the true degradation opportunity time is needed for computing the degradation rate constant in this case. We have used statistical moments to show that when degradation follows first-order kinetics, the time of degradation is an adjusted convection time (ACT). It is defined as the harmonic mean of m1/R and the convection time (L/v), where m1 is the first moment, R is the retardation factor, L is the length of soil column, and v is the pore water velocity. The adjustment in the convection time scale is a direct result of both dispersion and degradation occurring simultaneously in soil. We show that these two processes tend to slightly reduce the true convection time for the leaching event. Therefore, the ACT is smaller than L/v when both dispersion and degradation occur. We have tested our result by generating artificial breakthrough curves with known first-order degradation rate constants and then successfully estimating the rate constant from the breakthrough curve by using our approach. We have outlined a detailed procedure to estimate the degradation rate constant from the information generated in a typical leaching experiment.

Keyword(s): degradation, breakthrough curve, moment, travel time, convection time.

Poster presentation.

Chlorinated organic compounds are a hazard to the environment and to humans. Although many of these compounds are generated by nature, there has been concern about the effect of manmade chlorinated compounds on the environment. This recent concern has spurred research investigating environmentally benign disposal methods for these chemicals. Previous research has shown that nanometer sized calcium oxide particles are effective in destroying some simple compounds of hazardous concern. It has also been shown that magnesium oxide will also destroy some of these chemicals and that iron coated magnesium oxide shows an enhanced reactivity relative to uncoated magnesium oxide. Typically the transition metal loading is 1-5% of the molar amount of the magnesium oxide substrate.

The purpose of the current research is to see if the same enhanced reactivity occurs with CaO particles which are less expensive to manufacture. This research investigates the effect of nickel, copper and zinc coatings on the ability of calcium oxide particles to destructively adsorb carbon tetrachloride. Carbon tetrachloride was chosen as a model compound because its reaction with CaO is simple and easy to monitor. The products of the reaction are simply calcium chloride and carbon dioxide.

Preliminary results show that nickel coated calcium oxide has an enhanced reactivity relative to uncoated calcium oxide. It has also been observed that the particles may exhibit a “catalytic” reactivity rather than stoichiometric and, therefore, may be extremely useful in the degradation of harmful chlorinated organic compounds.

Keyword(s): destructive adsorption, chlorinated organics.

Oral presentation in chemical destruction session.

This research was undertaken to simplify the selection of the least-cost treatment option for treating waters contaminated with synthetic organic chemicals (SOCs). Five aqueous treatment processes were considered: air stripping, liquid-phase adsorption, steam stripping, biofilm reactor, and combined biodegradation and adsorption (bio-adsorption). Because off gases from air stripping towers are frequently regulated, four off-gas treatment processes also were considered: gas- phase adsorption (both on- and off-site regeneration), thermal incineration and catalytic oxidation. Mathematical process performance and cost models were developed for each process. The least-cost design for each process was identified for a set of typical contaminated waters, and the results were synthesized to create generalizations concerning process selection based on fundamental process variables.

For example, the cost of treating air stripper off gases was found to be primarily a function of a compound's adsorbability, volatility, flow rate and influent concentration. A set of diagrams was created to identify the least-cost off-gas treatment for a given set of conditions.

For aqueous processes, the least-cost air stripping tower design changed when off- gas treatment was added. A methodology for comparing the costs of air stripping with off-gas treatment and liquid-phase adsorption was created in the form of a process selection diagram. The comparison methodology is based upon physical parameters of the target chemical.

In considering bio-adsorption, it offered longer bed lives than adsorption alone in nearly every case, though the degree of improvement varies. Diagrams were created to identify cases where bio- adsorption is particularly economical. Situations were identified where a biofilm reactor and where steam stripping may be economically viable. Heuristics concerning when processes-in-series are valuable were also developed. As discussed, tools and generalizations were created to aid engineers in making intelligent decisions concerning preliminary treatment process selection, with the overall goal of better, cost-effective designs and more rapid selection.

Keyword(s): organic chemicals, treatment, remediation, heuristics.

Oral presentation in environmental assessment and decision making session.

The practical application of chemical analyses begins with a request for the analysis and concludes with provision of the requested analytical data. The key to successful execution of this activity is timely, professional communication between the requester and the analyst. Often chemical analyses are not satisfactorily executed, either because the requester failed to give adequate instructions or because the analyst simply “did what he/she was told.” The request for and the conduct of an analysis represent a contract for the procurement of a product (information about the sample); if both parties recognize and abide by this contractual relationship, the process generally proceeds smoothly. Note that the “customer” and “analyst” may be the same person, especially in a university research environment; these same issues hold even in this single-person interaction. Chemical analysis is traditionally defined as the determination of what is in the sample and how much of that constituent is present. More rigorously, we also need to know if the analysis was conducted correctly and we need documentation. In short, we need quality control. Before a chemical analysis begins, it is important to establish the data quality objectives: What are we looking for, and how much error can we tolerate? This presentation will provide a practical tutorial on how to get chemical analyses done properly and cost-effectively.

Suggestions will be provided for improving the quality of the analytical product through the requester-analyst interface.

This work was supported by the U.S. Department of Energy, Assistant Secretary for Environmental Management, under contract W-31-l09-Eng-38. The submitted manuscript has been authored by a contractor of the U.S. Government under contract No. W- 31-109-ENG-35. 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.

Keyword(s): chemical analysis, analysis.

Oral presentation in conducting HSRC research session.

Various technologies are currently being investigated to remediate aquifers contaminated with organic chemicals that are in the from of non-aqueous phase liquids (NAPLs). After a spill, NAPLs remain entrapped in the soil for long periods of time, thus acting as a source of contamination. The possible use of surfactants as a way of enhancing dissolution and thus depleting the source is under study. In our ongoing research we have demonstrated the importance of heterogeneity in the transport and entrapment distribution of NAPLs in aquifers. We have identified two modes of entrapment, namely microscale entrapment at the pore scale and macro-scale entrapment that is produced by the larger heterogeneities of the aquifer. We have investigated the effects of relative permeability and dimensionality on the dissolution of these chemicals, both under micro- and macroscale entrapment. This paper presents the results from a study where we have investigated the process of enhance dissolution under macro- and microscale entrapment. These results will be used to develop and validate models that can be used to design and evaluate field remediation schemes that use surfactants. A series of two-dimensional experiments were conducted to investigate the dissolution of non-aqueous phase liquids (NAPLs). Experiments were conducted for NAPLs at both residual saturations and under macroscale entrapment conditions. Aqueous phase samples were collected downgradient of the source, and the dissolved NAPL concentrations were measured by gas chromatography. The breakthrough curves were analyzed to determine the overall mass transfer coefficients. The mass transfer coefficients were used to investigate the effects of entrapment saturations and the dimensionality of flow on enhanced dissolution. The experimental design, results and data analysis are presented. Conclusions on the use of these results for the design of large pilot-scale, enhanced- dissolution experiments to study scale effects are presented.

Keyword(s): ground water, NAPL, dissolution, surfactants, heterogeneities.

Oral presentation in non-aqueous phase liquids session.

Scrap tires represent a major environmental problem. It is estimated that approximately 2.5 million tons of scrap tires are generated each year in North America. Most of these materials are discarded and have found little use through reclamation. The reclaimed rubber and other materials are not suitable for production of tires or other durable rubber goods. As a result, most of the scrap tires accumulate in dumps and create hazards for infestation, water pollution and fire.

Automobile tires are composed of carbon black reinforced rubber. Typical composition of tires is 62% styrene butadiene copolymer rubber, 31% carbon black, and other materials, such as extender oils, sulfur, zinc oxide and stearic acid, which are present in smaller amounts. Potential reuse of the polymeric contents of tires has received considerable attention. Processes have been evaluated for production of goods such as construction fillers; however, fillers and other reclamation applications have shown relatively small economic potential. Another process of interest is the pyrolysis of tires to produce liquid hydrocarbons and gases with high calorific values. Pyrolysis yields solid char residues which generally contain higher amounts of elemental carbon than the original tires. Most studies on conversion of tire char to activated carbon rely on further pyrolysis at 600-850 C under nitrogen atmosphere followed by activation with acid for reaction with superheated steam. All of the processes are energy intensive. An alternative low energy conversion process has been evaluated in our laboratory. The process is based on a counterflow oxidative technique. The technique utilizes a flame front which propagates in a direction counter to the oxygen flow. The results obtained show that, under optimal conditions, the process yields carbon with adsorptive characteristic similar to those of commercially available activated carbons. Breakthrough curves for toluene, phenol and aniline were found to be comparable to those obtained with commercial carbons. Similarly, comparable adsorptive capacities were obtained for polychlorinated biphenyls (PCBs) in mineral oils.

One of the major concerns for scrap tire derived carbon is the presence of leachable materials. Initial results of the U.S. EPA extraction procedure and soxhlet extraction are very encouraging and show that the material is essentially free of leachable chemicals.

Keyword(s): scrap tires, carbon, counterflow oxidation.

Oral presentation in pollution prevention/waste minimization.

Ground water is an important source of water for much of the United States. Contamination from agricultural pesticides presents a serious problem. Fluctuating water tables may increase microbial degradation of these contaminants by: (1) optimization of moisture content, (2) increased transport of the contaminant to the microbes, and (3) increased transport of soil organic matter to the area. This research is investigating the effects of a fluctuating water table on microbial degradation of pesticides. Multiple soil columns are being used in this experiment. We expect to observe increased pesticide degradation with a fluctuating water table.

Keyword(s): pesticide, microorganism, degradation.

Poster presentation.

The performance of the in-well air sparging process has been examined for cleaning up a site contaminated with a mixture of non- aqueous phase liquids (NAPLs). The process remediates in situ a contaminated aquifer by combining chemical, physical and biological processes. A blower at the top of the well induces upward motion of air and water in the well, thereby creating a circulatory flow pattern in the aquifer. The flow of water in the aquifer has been modeled as a potential flow between the sources and sinks.

Biodegradation may be enhanced by installing a packed-bed bioreactor within the well casing. Since oxygen-enriched water flows out of the bioreactor into the aquifer at the upper screened segment of the well, biodegradation is also enhanced in the aquifer. The results of simulation demonstrate that the compositions of the NAPLs in the aquifer vary with time and that the size of the packed-bed bioreactor influences the pathway through which the contaminants are removed from the aquifer. As a general rule, however, biodegradation plays a more dominant role in removing the less soluble contaminants.

Keyword(s): aquifer, biodegradation, modeling, air sparging.

Oral presentation in non-aqueous phase liquids session.

Several different varieties of alfalfa plant tissues were tested for their potential to uptake copper ions from solution. Batch experiments were performed to determine the pH profiles, time dependency, capacity of copper uptake, and desorption of the metal bound. Also optimal drying conditions (oven/lyophilized) as well as buffering effects were examined. Differences in roots and shoots were examined to determine the uptake properties of seven alfalfa varieties (germplasms). Protein analysis and crude fiber content was determined for all biomasses studied. Most of the biomasses studied showed a high affinity for copper ions as the pH increased from 2 to 6 with optimum copper binding around pH 5.0. Time dependency experiments for copper binding showed a very rapid absorption of the copper ions by the various alfalfa species. Binding capacity experiments for copper binding showed that the capacities of the shoots is very similar, with african and ladak germplasms being the highest.

Binding capacities for the roots also showed to be similar with malone germplasm as the highest. Overall, the shoots have higher binding capacity than the roots. More than 90% recovery of the copper bound to the various species by treatment with 0.1 M HCl. This innovative technology has great potential for the removal and recovery of heavy metal ions from contaminated waters.

Keyword(s): bioremediation, alfalfa, Medicago sativa, copper, metal binding.

Oral presentation in phytoremediation session.

In this study, we used the Canadian sphagnum peat moss, humic acid and humin (extracted from the peat moss) to investigate the copper binding properties of the different biomasses. Batch pH profile experiments indicated that the adsorption of Cu was pH dependent. At pH 4.0 and pH 5.0, 99% of copper was bound by all three samples (peat moss, humic acids and humin) under our experimental conditions. Time dependency and capacities of adsorption showed that humic substances extracted from sphagnum peat moss had better metal binding properties. A high percentage of the bound copper was released by acid treatment. This corroborates that humic substances coming from peatland were an ideal media to adsorb heavy metal ions from contaminated water. It is believed that carboxyl groups are primarily involved in copper ion binding. Experiments are underway in our laboratory to determine the possible role of carboxyl groups in copper binding. These experiments consist of chemical modification of the carboxyl groups. Description of these experiments will be presented at the conference.

Keyword(s): sphagnum, peat moss, copper, uptake, humic substances.

Poster presentation.

Different varieties of Medicago sativa (Alfalfa) were exposed to nickel concentrations to determine their metal binding capabilities. The Alfalfa samples were divided into roots and shoots for experimental purposes. Studies to determine the pH profile for nickel binding were conducted. These experiments indicated that the metal binding to the biomass was better between pH 5 and pH 6, showing above 80% bound. We also determined that between pH 2 and pH 3 the binding of nickel was very low. This may suggest that if the process is reversed nickel could be recovered from the plant cells. Time dependency experiments for nickel binding as well as binding capacity results would be presented at the conference. In addition, studies to determine the reversibility on the nickel binding as well as binding capacities for various Alfalfa varieties will be discussed.

Keyword(s): bioremediation, alfalfa, Medicago sativa, nickel, metal binding.

Poster presentation.

Inactivated copper-sensible and copper- tolerant strains of Mucor rouxii cultured in the presence and also absence of the metal were tested for their potential to uptake copper ions from solution. Batch experiments were performed to determine the pH profile, time dependency, binding capacity and reversibility on the binding. Biomasses studied showed a high affinity for copper ions at pH 5, and the highest capacity for Cu(II) uptake was exhibited by a tolerant strain grown in the presence of copper. Approximately 100% stripping or removal of the copper absorbed was obtained when the metal was extracted by treatment with 0.1 M HCl.

These preliminary findings suggest that the presence of copper in the media allows development of chemical functional groups (most likely carboxyl groups) on the fungal cell walls. This phenomenon can have useful applications for metal removal from contaminated water.

Keyword(s): Mucor rouxii, copper binding, bioremediation.

Oral presentation in bioremediation session.

Organotin compounds are used as fungicides and antifouling agents which are incorporated into paints for use in sea vessels. These compounds have been found to be a threat to the environment. Method development for the determination of tin by Zeeman GFAAS was studied. Different matrix modifiers were evaluated including NH4H2PO4/Mg(NO3)2 which produced the optimum tin signal. The effect of acids such as HNO3 and HCl on the tin signal was investigated. The analytical method developed in our investigation was used to determine tin content in marine sediment from La Paz, Baja California Sur, Mexico.

Keyword(s): tin, method development, marine environment.

Poster presentation.

Growth of a Pseudomonas fluorescens species has been demonstrated with TNT as the sole nitrogen source and acetate as the carbon source. While only 10% of the transformed TNT was accounted for by HPLC analysis, growth measurements indicate that a significant amount of the TNT nitrogen present was converted to biomass. 2-amino-4,6-dinitrotoluene was identified as a dead end metabolite. Picric acid and trinitrobenzene were also identified as intermediates and may be part of the nitrogen use pathway. The use of TNT as a nitrogen source may lead to ring cleavage and mineralization, since growth has also been observed with TNT as the sole nitrogen and carbon source.

Keyword(s): trinitrotoluene, bioremediation.

Oral presentation in bioremediation session.

A model was developed to assist in determining the fate and transport anticipated during remediation of trinitrotoluene (TNT) contaminated soils. The model is physically based to incorporate biological, physical, chemical and environmental factors in predicting the degradation fate of trinitrotoluene (TNT). Model applications range from contaminant sources such as abandoned mines, waste heap piles, munitions industrial waste water lagoons, military bombing ranges, and weapons maintenance and disposal operations.

Keyword(s): remediation, model, TNT, munitions, wastes.

Movement of chemicals on land surfaces due to shallow overland flow of infiltration excess rain water poses a potential environmental hazard to receiving waters downstream. Such problems are abundant in the chat-contaminated soils of southeast Kansas. Surface water travels two to three orders of magnitude faster than subsurface flow and is sometimes responsible for removing substantial amounts of chemicals which are initially mixed in shallow soils. A physically-based mathematical model will be presented to represent this mode of contaminant movement, with emphasis on overland flows in regions neighboring streams. Some modeling results will be presented and future applications will be discussed.

Keyword(s): surface water, contaminant transport.

Poster presentation.

During the summer of 1994, an agricultural and a pristine site within the Konza prairie research area were identified to study the spatial structure of the surface infiltration properties. About 40 surface locations were selected for sampling over 10 m by 10 m areas at each of the two sites. The spatial locations were designed to obtain a balanced support for variogram computations. The Guelph Permeameter was used for the determination of soil properties. The infiltration properties examined were the saturated hydraulic conductivity, the matrix flux potential, sorptivity and the alpha parameter. These properties were analyzed using geostatistical tools. Even though the individual plots appeared homogeneous, the hydraulic properties (specially saturated hydraulic conductivity) exhibited very wide variability. Correlation lengths of these properties were found to be in the order of meters. The utility of such analysis in our understanding and modeling of field scale behavior of subsurface water will be investigated.

Keyword(s): infiltration, spatial variability, geostatistics.

Poster presentation.

Determining the efficacy of treatment effects by replicated field trials is truly confounded by the presence of spatial variability in most field soils. It is not possible to construct two field sites which are perfectly alike with respect to their soil properties and initial contaminant concentrations. When the treatments involve vegetative remediation strategies, this problem is further aggravated by the additional uncertainty introduced by factors like root density. Geostatistics provides us a powerful mathematical tool for designing, analyzing and comparing treatment effects. It has been demonstrated that inclusion of information on covariance structure of spatially varying quantities (in this case contaminant concentrations) increases the statistical power of hypothesis tests. Some applications of geostatistics to actual design and implementation of field sites will be presented.

Keyword(s): spatial variability, hypothesis testing, geostatistics.

Oral presentation in environmental assessment and decision making session.

Macropores can be significant paths of flow in the vadose zone and can transport water and chemicals at velocities much faster than predicted with conventional solute transport models. At the Rocky Flats Environmental Technology Site in Golden, Colorado, plutonium-contaminated oil leaked from deteriorated drums and was subsequently airlifted by winds and deposited on soils in a cast and south east- trending plume. Macropores have been shown to occur at that site and must be considered in a model predicting the fate of Pu-238-239. While macropore models exist, few studies have calibrated using field data. This study was conducted to determine the feasibility of using a 2-D finite element macropore model at that site to predict the fate of Pu-238-239.

A well-defined system will be used to determine the feasibility of modeling macropores and to calibrate the model. Presently, a column is being manually packed with sieved soil into a 80 cm long and 30 cm diameter column. A macropore will then be created in the column. The sample will be tested under a variety of rainfall rates and boundary conditions. Field samples will also be used to evaluate the model. Two undisturbed soil columns (35 cm by 50 cm) were excavated from a structured clay soil near Boulder Creek. A rain simulator, which consisted of hypodermic needles attached to the bottom of a short cylinder, applied water at 6 cm/hr. A 49 cell grid sampling device collected the outflow. Tensiometers showed that no flow occurred until the sample was fully saturated. Most of the flow occurred within two grid cells, and conservative tracers exhibited breakthrough at 0.5 pore volumes which suggest some type of macropore flow.

Keyword(s): macropore, model calibration, radio active waste, vadose zone modeling.

Oral presentation in fate and transport session.

The Haskell Environmental Research Studies Center (HERS), located at Haskell Indian Nations University (HINU) has joined with the Great Plains-Rocky Mountain Hazardous Substance Research Center (GP-RM HSRC) to administer the Native American and Other Minority Institutions Program (NAOMI). The NAOMI Program was funded to involve minority educational institutions in research, training and technology transfer. The HERS Center currently administers several programs. One primary element of the NAOMI Program is a Seminar Series which provides public education on hazardous substances and related environmental issues. Seminars are disseminated by the mailing of videotapes or through satellite downlinks. The NAOMI Program has been able to provide funding for several individuals from participating institutions to attend the Tenth Annual Conference on Hazardous Waste Research in Manhattan, Kansas, during May 23-24. In addition, NAOMI was able to match five scholars from Native American and other minority academic institutions with HSRC researchers through the Summer Cooperation Program. HERS Staff, in association with the U.S. Department of Agriculture, worked to coordinate a program which was part of the twenty-fifth anniversary celebration of Earth Day in Washington, DC. The program brought together tribal leaders, elders and scientists in a panel discussion of global change issues. HERS also received funds from the Department of Defense to provide certified training to students from Tribal Community Colleges. This workshop is part of an on- going curriculum development project. The first workshop under this program is tentatively scheduled for June 18-30, 1995, at Haskell Indian Nations University. The HERS Staff is hoping to provide training for forty participants. HERS has been able to act as an information clearing house by sending grant solicitations to participating institutions where applicable. NAOMI Seminar videotapes are available for use in the library of Kansas State University and can be obtained nationwide through interlibrary loan.

Keyword(s): Native American, minority, research, technology transfer, hazardous substances.

Poster presentation.

Organic ligands may affect the adsorption of heavy metals to soil by the formation of complexes. Batch adsorption experiments were conducted to determine the effect of citrate on the adsorption of zinc to soil. At concentrations ranging from 0 to 1500 mmol L-1, the adsorption of zinc by a soil under constant pH was measured in the presence of citrate of 0 to 10000 mmol L-1. It was found that the adsorption of citrate by soil was independent of zinc concentration, but the adsorption of zinc by soil was dependent on citrate concentration. Zinc adsorption increased with increasing citrate concentration up to 3000 mmol L-1; zinc adsorption decreased with increasing citrate concentration beyond 3000 mmol L-1. The adsorption of the zinc-citrate complex was ligandlike at this pH, and the increase or decrease of zinc adsorption was due to the formation of the zinc-citrate complex.

Keyword(s): adsorption, heavy metal, organic ligand, ligandlike complex.

Oral presentation in heavy metals session.

Bioremediation, the process of microorganisms controlling and degrading contaminants, is one of the fastest growing hazardous waste cleanup alternatives. Fourier transform infrared (FT-IR) spectrometry is used to monitor the uptake and degradation of volatile organic compounds (VOCs) in contaminated ground water. Previous studies, using FT-IR spectrometry to monitor, suggest that toluene was degraded by adapted alfalfa plants and/or their associated microorganisms. A plant chamber was designed to model contaminated ground water flow. Alfalfa was planted in a 90 cm x 40 cm x 35 cm chamber. 200 mL/L of trichloroethylene (TCE) spiked ground water was continually fed into one half of the chamber. The other half of the chamber received 100 mL/L each of 1,1,1- trichloroethane (TCA) and chloroform (CHCl3). Present studies include monitoring 1,1,1-trichloroethane, chloroform and trichloroethylene from a population of adapted plants. The gas phase above the plants in the chamber at various growing stages was monitored for accumulation and depletion of contaminants. Also headspace gas samples of the inlet and outlet wells of the plant chamber were measured. The transpiration rate of individual plants was successfully monitored using deuterium as an internal standard in contaminated ground water. Studies suggest very little contaminant was taken up from the flow of water through individual plants. Also a mass balance of the alfalfa plants and the plant chamber is being determined. The concentrations of the contaminants and their by-products in the alfalfa plants are being measured. The FT-IR spectrometer can quickly and efficiently monitor the effects of plant bioremediation.

Keyword(s): FT-IR, bioremediation, volatile organic compounds (VOCs).

Oral presentation in phytoremediation session.

The United States Department of Defense (DoD) has literally thousands of sites that have been contaminated from past military activities. The cost of remediating these sites using existing technologies, such as activated carbon, will be astronomical. Advanced oxidation processes (AOPs) have promise because they effect on-site destruction of the contaminants. However, AOPs must be optimized for treatment, because without increased process optimization AOPs could result in costs similar to that of activated carbon. AOPs are by definition those oxidation processes that utilize the hydroxyl radical ( OH) as one of the (or the) primary contaminant oxidation mechanisms. Since the hydroxyl radical is an unstable chemical species, AOPs must be designed to produce the radical on-site through a variety of photolytic (illuminated) and/or chemical reactions (dark).

To optimize AOPs and reduce remediation costs, the mechanistic workings of various AOPs must be understood. The kinetics of AOP systems are complex. The rates of contaminant removal and reaction orders often change according to the water matrix and oxidant concentrations. Maximum rates of treatment have occasionally been observed for certain oxidant concentrations and ratios. We have developed a kinetic model and used the model to derive a rate expression that describes the OH radical concentration given a set of operating conditions. The model explains well some of the observed complex dependence behaviors of AOPs, with the following expression: This model and derived expression is useful for process optimization. In its final form, this paper will present experimental results of process optimization for hazardous waste treatment. Kinetic constants of contaminant degradation will be presented as a function of test parameters such as pH, O3 and H2O2 concentrations and ratios, contaminant concentration, water characteristics including hardness, carbonate content, alkalinity, and radical scavenger concentration. A major emphasis of this paper will be to test the mechanism proposed for AOPs. The kinetic results will be used to validate or modify the proposed AOP kinetic model. Limitations of the model will be identified. Optimal operating conditions and recommendations for hazardous waste treatment will be made according to the experimentally validated kinetic model.

Keyword(s): advanced oxidation processes, contaminants degradation, remediation, optimization.

Oral presentation in chemical destruction session.

Heavy metal contamination of soil is a common problem encountered at many hazardous waste sites. Lead, chromium, cadmium, copper, zinc and mercury are among the most frequently observed metal contaminants. They are present at elevated concentrations at many National Priority List sites. Heavy metals are toxic to people and pose a great risk for safe ground water supply. Once released into the soil matrix, most heavy metals are strongly retained and their adverse effects can last for a long time. Chelating extraction of heavy metals from contaminated soils has recently been seen as a treatment method. However, results from our laboratories show that, in order to recover the heavy metals and reclaim the chelating agents, only suitable chelating agents should be used for this application. The structure and electronic configuration of a chelating agent are important to its metal- complexing ability, speciation, selectivity, biodegradability, toxicity and transportability. The molecular connectivity index model which can encode the structural and electronic information of a chelate is seen as a useful tool to predict the said properties and aid in the selection of useful chelating agents for extractive removal of heavy metals from contaminated soils. The previous findings of various researchers have provided a simple method of encoding the essential information concerning a molecule into terms which can be employed in a linear equation; the latter is employed to validate or reject any or all variables. The approach is based on the assumption that there is, within the structural formula, sufficient information such that a useful index based upon non-empirical counts of atoms can be calculated. The technique has been found useful for correlating molecular structures with properties such as molar refraction, polarizability, water solubility, chromatographic retention data, orientation of ring substitution, phenol toxicity to fathead minnows, antimicrobial action of phenyl- propylethers, flavor and taste threshold, and many others. Relevant properties of the metals can be included in the LFER providing a basis for developing a “designer” chelator. New methods for selection of variables and regression diagnostics have been employed.

In its final form, this paper will present the results of using the molecular connectivity index model to correlate the metal- complexing ability of a large number of chelating agents with their molecular structure. The developed model will be useful for predicting metal complexation for other agents for which the complexing constants are unavailable. The limitations of this model will be identified. This paper will also present the experimental results of heavy metal extraction from soil using a few selected chelating agents. The removal of metals including cadmium, copper, lead and zinc has been studied under different pH, soil suspension, total chelator concentration, total carbonate concentration, and age conditions and will be presented. In particular, the selectivity and subsequent recovery of heavy metals will be emphasized.

Keyword(s): structure-activity, metal, soil, chelator, contamination, remediation.

Oral presentation in heavy metals session.

The environmental fate and biological effects of methyl-tertiary-butyl ether (MTBE) is of concern because, among other factors, it is highly soluble in water, and potential ground water contaminations may occur through accidental exposures and spills. The effect of MTBE on the hexadecane mineralization by natural consortia of hydrocarbon degrading microorganisms was investigated using radiorespirometric techniques. We found that MTBE increased oxygen consumption but that concentrations approaching 1.8 mg/l inhibited the hexadecane mineralization potential of consortia found in a variety of soils by up to 50%. These results indicate that MTBE can be metabolized in the environment but that toxicity may adversely affect overall biodegradation of hydrocarbon constituents of liquid fuel.

Keyword(s): MTBE, hexadecane, radiorespirometry.

Oral presentation in bioremediation session.

Each year approximately 285 million scrap tires are added to stockpiles, landfills or illegal dumps across the United States. The Environmental Protection Agency (EPA) estimates that the present size of the scrap tire problem is 2 to 3 billion tires. The existing tire piles pose fire and health hazards. There is a large number of tires being accumulated in rural areas. For example, Cloud County, a rural county in Kansas, has a tire pile consisting of approximately 573,000 mixed car, truck and tractor tires. Under current state law in Kansas, these tires must be shredded before storing in landfills. Introduction of scrap tire rubber into roads has the potential for reducing this waste problem. The feasibility of using larger rubber chunks from shredded tires as aggregates in cold-mixes for road construction was investigated in a study conducted at Kansas State University under the sponsorship of Kansas Department of Transportation (KDOT). The research was directed toward development of a chunk rubber asphalt concrete (CRAC) mix design for low volume road construction using local aggregate, shredded tire rubber chunks and cationic emulsion (CMS-1). Various parameters of cold mix as well as inclusion of fly ash following KDOT's practice of using Type C fly ash in cold mix were studied. Low Marshall stability and high flow values were obtained for asphalt mixes with CMS-1 emulsion. A medium-curing cutback was also experimented in the cold mix. A set of mixes using different combinations of chunk rubber content, emulsion content and fly ash amount were tested. Based on the Marshall stability results, some of these mixes appeared to be suitable as binder courses or stabilized drainable bases for low volume roads. Marshall stability results of mixes with 10% Type C fly ash showed optimum CMS-1 emulsion contents of 6.8, 7.3 and 7.8% for 2, 4 and 6% rubber, respectively. The Marshall stability values decreased for increasing rubber contents. The target Marshall stability value of a suitable cold mix at 110 F was required to be 500 Ibs. A mix with 10% Type C fly ash, 2% rubber and 6% CMS-1 emulsion showed an average Marshall stability value of 420 Ibs. Higher stability values are expected if the maximum aggregate size in the mix is increased. If 20 Ibs of chunk rubber equivalent is produced per tire, then a one mile long and 24-ft wide low volume road with a 4-in thick base built with this mix can incorporate approximately 5,360 tires. This application can minimize the scrap-tire waste problems of rural communities.

Keyword(s): chunk rubber, cold-mix, scrap tires, low-volume road, mix design.

Oral presentation in pollution prevention/waste minimization.

Environmental hazards are posed by the presence of 2,4,6-trinitrotoluene (TNT) and its degradates in munitions-contaminated soils. TNT sorption and bound residue formation must be characterized accurately to predict TNT transport and fate in soils. We found TNT sorption was concentration dependent and nonlinear for concentrations between 80 mM and 300 mM L-1. Sorption did not approach equilibrium even after 168 d. Consequently, predictions regarding transport and fate of TNT made on 24 h equilibration and linear adsorption may not be accurate. Particularly critical are TNT interactions with the top several centimeters of soil, which are highly contaminated at the sampling site. TNT sorption was determined in the presence and absence of solid phase TNT. We observed TNT adsorption continued to increase until the end of the experiment (168 d). Adsorption was rapid and 35 and 38% of the total 14C (added as 14C-TNT) was adsorbed within 0.5 h in both soils (with and without solid phase TNT). After 168 d, 79% of 14C was adsorbed by soils with solid phase TNT versus 93% for soils without solid phase TNT. The readily available (CaCl2-extractable) and potentially available (acetonitrile-extractable) pools of adsorbed TNT decreased rapidly with time. The 14C-activity continued to increase in the organic fractions (fulvic acid and humic acid) and a higher percentage of 14C was found in fulvic acid than in the humic acid fraction. Approximately one-half of the total 14C was irreversibly bound, and only a very small amount was released when treated with strong alkali (10% KOH in methanol) and strong acid (1N HCI in methanol). Our observations indicate that bound residue formation constitutes a significant route of detoxification in soil.

Keyword(s): TNT, bound residue, sorption.

Poster presentation.

Volatile organic chemicals present at Superfund sites preferentially partition into the soil gas and may be available for microbial degradation. A simple mass transfer model for biodegradation for volatile substrates is developed for the aerobic decomposition of aromatic and aliphatic hydrocarbons. The mass transfer analysis calculates diffusive fluxes from soil gas through water and membrane films and into the cell. The model predicts an extreme sensitivity of potential biodegradation rates to the air-water partition coefficients of the compounds. Aromatic hydrocarbons are removed rapidly while the aliphatic hydrocarbons are much slower by orders of magnitude. Furthermore, oxygen transfer is likely to limit aromatic hydrocarbon degradation rates. The model presents results that cast doubt on the practicality of using methane or propane for the cometabolic destruction of trichloroethylene in a gas phase bioreactor. Toluene as a primary substrate has better mass transfer characteristics to achieve more efficient trichloroethylene degradation. Hence, in sites where these contaminants coexist, bioremediation could be improved. The model is extended further to examine the influence of water potential on transport and transformation rates within microbial biofilms present in unsaturated soils. Water potential has multiple effects on overall VOC removal through the thickness of the biofilm, the molecular diffusivity of substrates through the biofilm, and microbial physiology.

Funding for this work was provided by the National Institute of Environmental Health Sciences Superfund grant 3P42 ES04705-08.

Keyword(s): VOC, biodegradation, unsaturated soil, biofilms.

Poster presentation.

The effect of five different soil gas oxygen concentrations on the rates of degradation of pentachlorophenol (PCP) and polycyclic aromatic hydrocarbons (PAHs) was investigated by conducting a laboratory evaluation of field contaminated samples. The soil used in this evaluation was taken from the Champion International Superfund Site in Libby, Montana. Radiolabeled PCP and pyrene were spiked onto the soil, and mineralization was measured. In addition, the fate of the contaminants in soil was determined by conducting a chemical mass balance on 14C that included volatilized, solvent-extractable, and non-solvent extractable fractions. Results are applicable to the design and management of prepared- bed bioreactors treating wood preservative- contaminated soil.

Keyword(s): bioremediation, prepared-bed bioreactor, oxygen tension, contaminated soil.

Oral presentation in bioremediation session.

The goal of this project is to understand factors which promote or retard biomass accumulation in porous media with an intent to apply such understanding toward beneficial manipulation of permeability and mass transport properties. Creation of subsurface biobarriers by selectively plugging permeable strata with microbial biomass is being explored as a means of reducing migration of ground water contaminants from hazardous water sites. Likewise, impermeable biobarriers may serve as a means of prohibiting subsurface dissolved oxygen transport to sites producing acid mine drainage. However fundamental questions must be answered in order to properly establish both the technical feasibility and methodology for applying biobarrier technology. Such questions include: 1) are biobarriers an effective means of plugging high permeability zones?, if so, 2) what length of formation flow path can be plugged?, 3) how long will they persist?, 4) can aerobic conditions be created and sustained, and 5) once developed, what are the residual permeability and mass transport capacity? Research results which address these questions will be reported in this paper. Cylindrical columns (6” diameter x 36” length), constructed by MSE Inc. were treated with epoxy polymers to prevent water channeling along the walls and filled with sand. Initial permeability of these columns was in the range of 10-14 darcy. Two pore volumes of Ultramicrobacteria (UMB), derived from an environmental strain of Klebsiella spp., were introduced into the columns at a concentration of 1.0 x 106 cells/ml, followed immediately by two pore volumes of citrate nutrient. Permeabilities at all levels sharply declined after two days and continued until column permeability was 5% of its original value.

Keyword(s): ground water quality, permeability reduction, bioremediation, selective plugging.

Oral presentation in fate and transport session.

The water quantity and quality of two adjacent agricultural watersheds were compared. The stream draining one watershed was farmed to the edge of the stream (unbuffered) and the stream draining the other watershed was “buffered” with 9 m (4 rows) of poplar trees on each side. The buffer was designed as a living filter to reduce agricultural non-point source pollution.

The pattern of nitrate concentration in the outflow of the watersheds in 1994 was similar to 1993; the buffered watershed consistently had lower nitrate levels. The nitrate concentration in the tile lines feeding each stream closely paralleled watershed outlet concentrations, showing that the tile line flow must be intercepted to fully control water quality at this site. Ground water nitrate levels in piezometer transects through the buffer showed generally low levels of nitrate, with a trend of decreasing nitrate concentration across the buffer from the field to the stream.

A section of the buffer which has been in place for 7 years was excavated to determine the distribution of macronutrients, rnicronutrients and carbon in the trees (leaves, stem, roots) and in the soil to a depth of 1.8 m. In addition, preliminary data was collected to determine the impact of the poplar buffer on rhizosphere microbial populations potentially important to bioremediation. Increased populations of heterotrophic and denitrifying organisms relative to the surrounding soil were observed in the rhizosphere of poplar.

Keyword(s): nitrate, non-point source, phytoremediation.

Poster presentation.

Losses of fuel hydrocarbon contaminants and geochemical evidence were obtained in a shallow sandy aquifer downgradient from a gasoline station operation at Patrick Air Force Base in Florida. Aerobic respiration, denitrification, ferric iron reduction, sulfate reduction and methanogenesis patterns were measured in relationship to the dissolved fuel constituents benzene, toluene, ethylbenzene and xylene (BTEX). Aerobic respiration and methanogenesis accounted for the greatest mass of BTEX mineralization. Calculated first order biodegradation rate constant was 0.014 week-1 for the dissolved BTEX. Based on stoichiometry of benzene oxidation reactions, the ground water at the site had an assimilative capacity to degrade the highest detected dissolved BTEX level of 7.3 mg/liter before the plume would migrate 370 meters from the source area.

Keyword(s): intrinsic bioremediation, BTEX, rate constant, stoichiometry

Oral presentation in bioremediation session.

Significant amounts of freons, predominantly CFC-11 (trichlorofluoromethane), are trapped over long periods in polyurethane foams. These foams are one of the most widely used forms of plastic with varied applications. Polyurethane and polystyrene form the bulk of polymeric foams for which freons have been used as the foaming agents. Initial concentrations of freons in such foams are in the 20-30% range.

Results of a survey of freon residues in polyurethane foam revealed that, in the absence of free exchange with air, these foams effectively retain freon for long periods of time. Polyurethane foam samples from 15 year old refrigerators were found to contain freon at concentrations ranging from 15-20% w/w. These concentrations clearly indicate that polyurethane represents a large, long-term source of freon in the environment.

To estimate the long-term release of freon, an experimental release model has been developed. The model takes into account such parameters as polymer film thickness, temperature and photoinduced degradation of polyurethane foam. The model has been validated with experimental results. The results show that the release of freon from a polymeric foam is dependent on permeability across the polymer film. The permeability is dependent on environmental parameters to which the foams are exposed. The most pertinent of these are temperature and exposure to sunlight. To monitor the effects of these parameters, a series of weathering experiments were undertaken. A QUV accelerated weathering tester was used for simulation of the damage to the polymer structure from exposure to the elements. Some of the foam samples were also aged under natural sun light. Freon content of foam was determined periodically. The determinations were carried out by extracting freon with methanol and injecting methanol solution into a calibrated gas chromatograph-mass spectrometer (GC-MS). Studies showed that freon release from foams is accelerated by exposure to near UV region of the solar radiation and an increase in temperature. The rate of release of freon from foam was found to be significantly higher at temperatures greater than 70 C. The release was found to follow first order kinetics with respect to time and temperature.

Keyword(s): freon, polyurethane foam, experimental model.

Oral presentation in environmental assessment and decision making session.

The term “Community Involvement” is the environmental catch phrase of the 90's. The commitment to keeping communities involved in the process of cleaning up hazardous waste sites has been important since the early 80's with the “lessons learned” at Love Canal, the canal that seeped huge quantities of poisonous chemicals onto a community in the City of Niagara Falls, New York.

The Superfund Program, under the jurisdiction of the Environmental Protection Agency (EPA), is committed to the timely and efficient identification and cleanup of hazardous materials spills and contaminated sites, with the ultimate goal of protecting human health.

For years, communities with culturally diverse populations have felt the lack of involvement and active participation in the decision making process for cleanup alternatives at hazardous waste sites. This presentation will look at various communication tools and will highlight research on three Superfund sites with culturally diverse populations where the community involvement process really worked.

Implementation of the community involvement process consists of developing innovative approaches with the affected communities to ensure that the communities regard specific approaches as “meaningful participation.”

Keyword(s): community involvement, culturally diverse, Superfund.

Oral presentation in community involvement session.

As the Great Plains-Rocky Mountain Hazardous Substance Research Center celebrates its 10th anniversary of its annual conferences with the theme, “10 Years of Progress: Solving Old Problems and Preventing New Ones,” this paper presents industry perspective on environmental management history and shows how Corporate America is responding to regulatory challenges and public pressure. This paper consists of three parts. The first part deals with a brief regulatory history particularly relative to U.S. Environmental Protection Agency's approach on end-of- pipe controls vs. pollution prevention. The role of Emergency Planning and Community-Right-to-Know Act and Toxics Release Inventories in moving the environmental management direction towards pollution prevention is highlighted. The second part of this paper presents “Environmental Management Continuum” (Continuum) describing how the regulated industry has responded to the evolving regulations. Different phases of the Continuum including denial, avoidance, compliance and pro-action are illustrated. A discussion on how the environment has become a strategic issue (rather than just a compliance problem) for Corporate America is presented.

Finally, this paper presents a 10-step approach to achieving environmental excellence, the final stage in the Continuum. Examples of industry leaders that are successfully applying elements of this approach are provided.

Keyword(s): regulations, pollution prevention, environmental management, environmental excellence.

Oral presentation in technology transfer session.

The objective of this research is to investigate the impact of vegetation—fescue (Festuca arundinacea)—on the fate of carcinogenic and recalcitrant benzo(a)pyrene in soil. The effect of vegetation will be evaluated by determining the distribution of 14C among soil, plant tissue, leachate and CO2 evolved in planted and unplanted soils using plant growth chambers during a 6-month experiment. These data will be analyzed to ascertain if there are differences between vegetated and non-vegetated soils with regard to leaching, degradation, plant uptake and mineralization of the 14C-benzo(a)pyrene. The beneficial effects of vegetation planted in soil contaminated by benzo(a)pyrene is anticipated.

Keyword(s): vegetation, benzo(a)pyrene, soil, plant, rhizosphere.

Oral presentation in phytoremediation session.

Past disposal practices at munitions production facilities have resulted in numerous acres of soil contaminated with nitroaromatics, particularly 2,4,6- trinitrotoluene (TNT). TNT and its degradates are toxic to biota, and contaminated soils need to be remediated to ensure environmental quality and safety. We previously demonstrated that Fenton oxidation effectively destroyed and mineralized TNT in both pure solution and aqueous extracts of TNT-contaminated soil. Our objectives were to develop practical approaches for remediating TNT- contaminated soils by Fenton oxidation. This was accomplished by proposing three possible remediation schemes. The first considered combining soil washing of TNT- contaminated soils with Fenton oxidation of wash waters. Using this approach, we determined the effects of temperature and humic and fulvic acids on efficiency of TNT removal and destruction. Secondly, we proposed combining soil washing with phytoremediation and determined the phytoxicity of the washed soil to tall fescue (Festuca arundinacea) germination and early development. The third approach considered direct Fenton oxidation of contaminated soil-slurries. Results indicated that aqueous soil washing can effectively reduce CH3CN-extractable TNT concentrations but large H20 volumes are required to meet EPA's remediation goal (17.2 mg TNT kg-1). The volume of H20 required can be reduced if wash water temperature is increased. Fenton oxidation of TNT in contaminated wash water was also demonstrated with greater than 90% mineralization achieved. Addition of humic and fulvic acids to aqueous TNT did not greatly alter the efficiency of destruction and indicates that Fenton oxidation could be effective on a variety of aqueous soil extracts. We also demonstrated that direct Fenton oxidation of soil slurries removed TNT from solution and produced extractable soil concentrations below remediation goals. These results indicate that when Fenton oxidation is combined with soil washing, phytoremediation, or used directly on soil- slurries, it is an effective abiotic remediation treatment for TNT-contaminated soils.

Keyword(s): munitions, TNT, Fenton oxidation, remediation.

Poster presentation.

Due to the chemical spills, leaking underground storage tanks, landfills and other pollution sources, soil and ground water are commonly polluted by hazardous organic chemicals. The interface between a clay subsoil and overlying sandy soil is a zone of high concentration of contaminants, water, organic carbon, soil nutrients and microorganisms. A study to investigate optimal bioremediation methods for clean-up of contaminated textural interfaces is being conducted. In the first step of the study, multi-layer soil columns will be constructed and contaminated with PAHs. Relationships between bioremediation and microbial nutrients, water table levels, fluctuation of water level, and type of the soil will be investigated in the columns. For assessing the relationship, physical, chemical, and microbial properties of soil and column effluent, flow of nutrients and PAHs, the degradation rate will be measured. In the second step of the study, a pilot scale microcosm will be constructed. It will include experiments to survey the multi-dimensional nature of the fate and transport of organic contaminants at the interface, and biodegradation variables will be optimized. To make use of the interfacial biokinetics observed in the column experiments and predict the effectiveness of bioremediation under similar in situ conditions, a mathematical model will be developed, which will focus on evaluating fate and transport of organic contaminants as a result of bioremediation at textural interfaces between coarse and fine soils. The model formulation accounts for the fate and transport of discontinuous immiscible phase in terms of biodegradation variables.

Keyword(s): bioremediation, microorganisms, polyaromatic hydrocarbons, NAPLs, ground water. Poster presentation.

Destructive adsorption of chlorocarbons on nanoscale calcium oxide particles has been successful in laboratory scale experiments. For effective implementation of nanotechnology, studies are being carried out at the bench scale level for these reactions. For experimental convenience, the reaction between CCl4 and CaO is considered as a representative reaction. The first phase of the work involved the determination of optimum parameters that affect the surface area of the activated particles. The particles were heated under a constant supply of nitrogen. Rate of heating, duration of heating, temperature, flow rate of nitrogen, and particle size were found to be the important factors.

The second phase of the work involves design and fabrication of the reactor assembly system and study of the adsorption reaction. A batch of 50 gms of the activated CaO particles can be treated in the fixed-bed reactor. Nitrogen is employed as a carrier gas for the CCl4 vapors. Temperature of reaction, duration of reaction, pressure inside the reactor, surface area of CaO, particle size, and the flow rate of the gas mixture are important parameters that govern the extent of conversion of CaO particles.

Keyword(s): destructive adsorption, nanotechnology, chlorocarbons.

Oral presentation in chemical destruction session.

Many numerical models developed to describe the two phase flow of hazardous organic liquids in the subsurface requires the capillary pressure saturation relationship as an input parameter. Due to the lack of data, a variety of techniques are used in multiflow flow models for estimation of capillary pressure saturation relationship for the liquids and conditions prevailing at hazardous waste sites. Furthermore these estimations are limited mostly to drainage curves neglecting the hysteresis effect. This paper present a new and rapid method to obtain the capillary pressure saturation relationship using a flexible wall permiameter and a continuous flow pump. The advantages of this method include eliminating artificially large pores between the sample container and porous medium, achieving complete initial saturation as the sample can be tested at elevated pressures, and obtaining complete drainage and imbibition curves in 4 to 5 days. The porous medium used was a crushed and sieved industrial silica sand with a mean grain size of 0.41 cm. The drainage and imbibition capillary pressure saturation relationships were first obtained for a water/air system. Water was withdrawn at a rate of 1 cc/h using a continuous flow pump from the initially saturated sample through the bottom porous plate. At the same time the non-wetting fluid (air) was allowed to enter from the top of the sample. The differential pressure between the non- wetting phase at the top and the wetting phase at the bottom was recorded at 100 second intervals using a pressure transducer and a data acquisition system. At residual saturation the direction of the pump was reversed to obtain the imbibition curve. The porosity of the sample and the pump rate was used to calculate the saturation corresponding to pressure measurements. The same sample was then tested for a water/p-xylene system. P-xylene was allowed to enter from the top of sample as the non-wetting fluid, instead of air, while water was withdrawn from the bottom of the sample. The drainage and imbibition capillary pressure relationships for the water/air and water/p-xylene systems will be presented.

Keyword(s): capillary pressure saturation relationship, porous medium, two phase systems.

Oral presentation in non-aqueous phase liquids session.

Soils at the former Nebraska Ordnance Plant (NOP) are grossly contaminated with TNT (2,4,6-trinitrotoluene). We found that this TNT-contaminated soil contains a variety of Pseudomonads. Our objective was to determine the potential of a single microbial species (Pseudomonas savastanoi) to degrade and mineralize TNT. All experiments were performed in Pseudomonas minimal medium (PMM) containing TNT (60 to 65 mg L-1) as the sole C source. Cells were prepared as inocula by growing to approximately mid-log phase in PMM (with glucose) for 9.5 h. Cells were then washed twice with saline and suspended in PMM (TNT sole C source). The inoculum was added to a concurrent set of experimental units containing PMM with either labeled (14C-TNT) or unlabeled TNT. Unlabeled medium was used for chemical (TNT, aminodinitrotoluenes, NO2 and NO3) and viable cell count determinations; samples were taken every 5 to 10 d for 72 d. Daily emissions of 14CO2 and 14C-volatiles were determined from labeled medium. Results indicate that 14CO2 emissions mimic viable cell populations with highest emissions within 24 h after inoculation. When we reinoculated the medium with a second and third inoculum (day 36 and 55), 14CO2 production was similar to the first inoculum. Inoculating the medium with killed cells did not produce 14CO2. Although 14CO2 production was related to cell density, overall mineralization was limited and less than 1% of total 14C applied. Chemical analysis revealed TNT concentrations declined to approximately 5 mg TNT L-1 within 72 d; the largest decrease in TNT concentration occurred within 24 h after inoculation. The production of aminodinitrotoluene was minimal and can not solely account for the loss of TNT. We also observed a steadily increasing NO2 concentration with time. These results indicate that Pseudomonas savastanoi can readily degrade but may have a limited potential to mineralize TNT.

Keyword(s): TNT, degradation, mineralization.

Poster presentation.

Many projects underway in Kansas involve application of geophysical and geological methods to a variety of environmental questions and problems associated with salt dissolution. The Permian salts are present in the shallow subsurface of the central and southern parts of Kansas. Environmental problems differ in scale from large-scale salt water contamination of entire aquifers, to localized dissolution collapse features. Causation is a combination of natural processes and anthropogenic activities (e.g., irrigation and oil field activities). An underutilized application of the workstation is color image transformation and treatment of the transformed wireline log data as “seismic” traces for the purposes of processing, interpretation and display. Such a transform can combine data from porosity, gamma and density tools generating a color coded “crossplot log” for each well. A well-designed color transformation of wireline log data from multiple wells maximizes both spatial and compositional information content and provides a readily interpretable image of the subsurface geology. The transformed image, in either 2-D or 3-D, can be treated on the workstation as “seismic” data, easing the data handling burdens through use of computerized techniques designed for interpretation of seismic data.

Various geophysical methods are also used to image the geology of the shallow subsurface (0-100 m). These methods include high-resolution seismic reflection (2- D and 3-D) vertical seismic profiling, and ground penetrating radar, and are used in conjunction with a computerized interpretation system. The system allows efficient, detailed and integrated study to be performed at these sites. Examples from throughout Kansas are used to illustrate the utility of using the computer workstation to perform integrated studies of environmental problems.

Keyword(s): computer workstations, environmental geology, Permian salts, seismic data.

Poster presentation.

The significance of risk assessment is the fact that the financial resources allocated for remediation and environmental services depend on the magnitude—real or perceived—of the environmental risk. This attitude is very important in the middle European countries where a privatization process of former state companies has been underway for about five years. Before privatization can occur it is necessary to remediate any damages caused during the former so called “state care” period. Damages have occurred, for example, due to improper storage and handling of fuels, improper storage of industrial chemicals, and improper waste disposal practices. In this situation, a knowledge of risk assessment procedures has become an integral part of hydrogeological consulting practice. However, there are many cases where the damage assessments appear to be in error due to problems associated with the choice of the risk assessment criteria, both environmental and economic. The different risk assessment procedures, criteria and outcomes are demonstrated using several case histories. In concluding, the necessity to introduce additional criteria in the risk assessment procedures is stressed.

Keyword(s): risk assessment, economics, criteria, soil pollution, ground water pollution.

Oral presentation in environmental assessment and decision making session.

The mobilization of discrete ganglia, formed by the residual entrapment of NAPL (non- aqueous phase liquids) in the soil, is of utmost importance in subsurface remediation. This paper utilizes a network modeling approach to address the stability of ganglia of various dimensions and to come up with probabilities of mobilization, stagnation and break-up of individual ganglia. A random allocation of pore-sizes and connecting pore-throats is carried out, and the stability of a given ganglion is studied by using a mobilization criteria at each of the nodes it occupies. The approach takes into account spatial and temporal changes in capillary number during pumping due to changes in pumping velocities and accelerations. It also takes into account the changes in capillary number due to possible changes in pore structure. The model is used to study the effect of a number of random pore-size and pore-throat allocations of a given pore-size distribution, on a single ganglion. Using these results, the mobilization and stagnation probabilities are determined. Results from column and micromodel experiments are used to assess the usefulness of network modeling in evaluating the fate and transport of NAPL ganglia.

Keyword(s): NAPL, network modeling, mobilization, stagnation probabilities.

Oral presentation in non-aqueous phase liquids session.

Contamination of ground water and soil is most often a mixture of pollutants, yet most quantitative studies of biodegradation either focus on one compound or describe the mixture as a single concentration (e.g., TOC). Information can be obtained from these approaches but they do not allow prediction of the fate of a single pollutant in the mixture or extrapolation of results to different mixtures.

As an initial step in the study of the biodegradation of organic pollutant mixtures, the biodegradation of benzene, toluene and phenol by Pseudomonas putida F1 has been measured and modeled. Each of these compounds can serve as the sole source of carbon and energy for this microorganism, and the initial step in the metabolism of each is catalyzed by toluene dioxygenase. Batch cultivation experiments were performed and the measurements of cell and pollutant concentration used to test different models of mixed pollutant biodegradation. In addition, toxicity tests have been conducted to verify the effectiveness of biodegradation. Experiments are currently underway to measure levels of toluene dioxygenase activity during biodegradation of different mixtures with the goal of relating these levels to the pollutant removal rates.

Keyword(s): biodegradation, mixtures, kinetics, toluene dioxygenase.

Poster presentation.

Di- and Trinitrotoluenes (DNT and TNT) are contaminants in waste streams from the manufacture of high explosives; dinitrotoluene is also a high-volume intermediate in the production of polyurethane plastics. These sources have resulted in soil contamination at weapons manufacturing sites and chemical plants as well as bombing ranges and blast sites. DNT is a potent carcinogen for which the EPA has established stringent ambient water quality standards. Because of their high toxicity to microorganisms, the nitrotoluene wastes are considered hard to treat; ppm-level residues in the intake water can upset the operation of biological treatment systems. Early studies with Jimson weed (Datura innoxia) in suspension culture at LANL indicated that the plant cells can remove TNT from solution. Our subsequent research at NMSU has shown that the removal mechanism is not just adsorption to the cell surface, but that the plant cells actively internalize the TNT and break it down rapidly into a variety of biotransformation products. Investigation of the metabolic fate of TNT in Datura species and in Lycopersicon peruvianum, a wild tomato species, has shown that reduction of nitro groups produces aminodinitro- and diaminonitrotoluenes; oxidation of the methyl group and denitration or deamination result in aminobenzyl alcohols, aminobenzaldehydes and aminobenzoic acids. The plant cell cultures can tolerate TNT concentrations up to 200 ppm and reduce the TNT to low ppm levels within 24 hours. Studies with whole plants of Datura innoxia, Datura quercifolia, and Lycopersicon peruvianum in soils contaminated with 14C-labeled TNT at levels up to 1000 ppm have shown that the plants take TNT up from the soil and accumulate 14C-labeled material to concentrations exceeding the soil levels of TNT up to ten- fold. Analysis of plant extracts shows that most of the stored radioactivity is in the form of the TNT metabolites identified in the cell culture work. These results show that uptake, biotransformation and accumulation by growing plants can be used as an approach to bioremediate soils contaminated with nitrated toluenes. Plant cells in batch culture or whole plants in hydroponic culture or as components of constructed wetlands could be used to bioremediate nitrotoluene-containing waste water.

Keyword(s): DNT, TNT, bioremediation, plants.

Oral presentation in phytoremediation session.

Alfalfa plants were grown in sandy silt soil (silt<10%) in a laboratory chamber with two channels, each with dimensions 35 cm in depth, 1.8 m in axial length, and 10 cm in width. The daily water feeding operation to the growing plants was accomplished by introducing either pure distilled water or water contaminated with organics of interest. Experiments were conducted to investigate the influence of these alfalfa plants in bioremediating soil and ground water contaminated with 1,1,1- trichloroethane (TCA) and trichloroethylene (TCE). From July '93 to October '93, TCA and TCE were fed at 50 and 200 mL/L, respectively. The contaminants were introduced into the channel that had been previously fed with phenol at 500 mg/L. The fate of these volatile chlorinated compounds in the saturated zone was monitored using the gas chromatographic headspace analysis technique. Methane at a concentration of about 14 mg/L was observed in the saturated zone of the channel. Measurements of the gas phase samples in the enclosed chamber using FT- IR indicated the presence of TCA and small quantities of TCE. No intermediates of biodegradation were observed during the gas phase measurements. After subsequently washing out the contaminants for 2 months, TCA and TCE were reintroduced into the plant growth chamber. One channel was fed with TCA and chloroform in the entering ground water at a concentration of 100 mL/L of water; the other channel was fed with TCE at a concentration of 200 mL/L of water. Daily phenol additions in the second case were accomplished through recharging wells. The results obtained from this study were compared to earlier experiments with TCA and TCE as contaminants where phenol had been previously fed into the channel as the inflow contaminated ground water. Recent studies indicate the presence of some biodegradation intermediates and the absence of methane in the ground water samples; however, using FT-IR, no intermediates were detected in the gas phase. The fate of these chlorinated compounds was also monitored for nearly two months in the absence of alfalfa plants.

Keyword(s): vegetation, volatile chlorinated compounds, headspace analysis, ground water.

Oral presentation in phytoremediation session.

The energetic utilization of untreated biomass results in solid waste streams in the form of wood ash. Despite the fact that biomass utilization is environmentally advantageous, because of a steep decrease in the contribution to the greenhouse effect, the wood ash produced from biomass heating systems may well pose an environmental hazard. This is due to the fact that biomass concentrates some heavy metals like cadmium and lead, which result mostly from the utilization of fossil energy sources.

The content of heavy metals decides to a large extent the fate of the resulting waste streams. If the contamination reaches high levels, a recycling of the wood ash into agriculture is made impossible. This is disadvantageous for two reasons: first, the disposal of wood ash becomes cost intensive and further diminishes the chances of biomass utilization in economic terms; second, nutrient substances like calcium, potassium and phosphor, which are also contained in wood and which make this kind of material potentially valuable for fertilizing purposes, are lost and have to be replaced by virgin raw materials.

Substantial investigations in Austria have revealed that a large amount of the wood ash generated by energetic utilization can be recycled to agricultural use. The base of these investigations was a rigorous balance of the process of heat generation by biomass. This resulted in a clear picture of the ways heavy metals, especially cadmium, take through biomass heating systems. On the base of these findings, new technological solutions are envisaged that reduce the waste flow, increase the amount of wood ash utilized in agriculture, and decrease the overall hazard which biomass heating systems pose to the environment. A detailed review of these results will be given in the presentation.

Keyword(s): wood ash, cadmium, lead, energetic biomass utilization.

Oral presentation in pollution prevention/waste minimization.

In recent years, researchers have focused on modeling of multicomponent reactive transport and developed models to study the mobility of potentially toxic heavy metals in the subsurface. However, the research so far has been concentrated on ground water regime of the soil. In our study, a mathematical model for understanding the fate of a typical heavy metal (zinc) in unsaturated soil will be developed. The entire modeling activity will comprise of three phases. During the first phase, a geochemical model to describe the soil heavy metal interactions will be developed. In the second phase, a solute transport model will be developed and linked with the unsaturated flow model which includes plant uptake. The final phase involves the sequential solution of the transport and geochemical models. Local equilibrium assumption (LEA) will be adopted, so that the transport and geochemical models can be decoupled while solving for heavy metal transport. The model will be used to simulate heavy metal movement through unsaturated soil at the laboratory column scale. The study will provide insight on movement of heavy metals in chat- contaminated fields of Southeast Kansas.

Keyword(s): heavy metal, geochemistry, solute transport, mathematical model, unsaturated flow, remediation.

Oral presentation in heavy metals session.

Some of the most common releases of organic chemicals in the environment, i.e. gasoline and jet fuel, do not consist of a single component, but are NAPLs composed of many water-immiscible and partially miscible organic fluids. In a non- homogeneous subsurface environment, physical heterogeneities may immobilize NAPLs, creating regions of macro-scale entrapment. Dissolution of soluble components from these immobile NAPL source zones creates long term water quality concerns.

Two-dimensional dissolution experiments were conducted in both a 10 meter long vertical flume and a smaller horizontal dissolution cell. The experiments simulated the simplified physical environment of a coarse gravel heterogeneity in a finer sand matrix. A synthetic gasoline mixture consisting of 90% cyclohexane and 10% benzene was entrapped in the gravel heterogeneity. The down gradient aqueous benzene concentrations were measured along a line of samplers perpendicular to the direction of water flow. The aqueous concentrations decreased as the lateral distance from the NAPL source increased and as the experiment progressed. The experiments were modeled using MODFLOW and a modified version of MT3D. The aqueous flow field was modeled using MODFLOW, accounting for the entrapped NAPL using aqueous relative permeability correction. The dissolution of the benzene and the transport of the aqueous phase benzene solute was modeled using MT3D incorporating a rate- limited dissolution term.

Keyword(s): ground water modeling, NAPLs, mass transfer, solute transport.

Oral presentation in non-aqueous phase liquids session.

During start-up, an interconnected process network, e.g., a network of chemical reactors, often generates an exceedingly large amount of the product or products that do not meet the specifications and thus should be regarded as waste to be treated or reprocessed. Moreover, if a hazardous or toxic component is contained in the product, its accumulation during start-up may be such that it potentially poses a high risk. Naturally, it is desirable that the accumulation be minimized. Devising the optimal start-up strategies for an interconnected process network necessitates the understanding of the process transient characteristics for the different modes of start-up.

For illustration, the present study simulates the start-up of a system comprising of three CSTR's connected in series according to the various modes of operation under either isothermal or non-isothermal conditions. Several simultaneous and/or sequential chemical reactions of different orders are considered.

Keyword(s): start-up, reactor network, hazardous waste.

Poster presentation.

Incineration has been widely used to remediate munitions-contaminated soil; however, rising costs and public concern mandate less expensive, more environmentally acceptable alternatives such as phytoremediation. Grasses can be effective remediators because of their high water use, adventitious root systems and rapid establishment. We determined the effects of TNT (2,4,6-trinitrotoluene) and its reduction product, 4-amino-2,6- dinitrotoluene (4ADNT), on germination and early seedling development of tall fescue (Festuca arundinacea Schreb, cv. Rebel Jr.). Tall fescue seeds were germinated in nutrient-free agar containing 0, 1.9, 3.75, 7.5, 15, 30, 45 and 60 mg TNT L-1 or 0, 1.9, 3.75, 7.5 and 15 mg 4ADNT L-1. Radicle emergence was observed within 4 d. Number germinated, radicle length, secondary root length, shoot length, seedling dry weight and respiration were measured for a 14-day period. Germination, radicle emergence and seedling development were not significantly different from the controls at 1.9 and 3.75 mg TNT L-1. At low TNT concentrations, respiration rates tended to be greater than those of the controls. With increasing TNT concentration, germination decreased, seedling development was delayed, meristematic regions of the radicle were more disorganized, and secondary root and shoot development was reduced.

Respiration rate decreased exponentially at 7.5 mg TNT L-1 and greater. Germination decreased to 53 and 38% at 45 and 60 mg TNT L-1, respectively. At these high TNT concentrations radicles emerged without root hairs. Cell proliferation occurred in the meristematic region; cells were circular and disorganized. No secondary root development was observed and shoot growth was reduced. Tall fescue germination was not greatly affected by 4ADNT. Radicle emergence, root and shoot development were similar to the controls at 1.9 to 7.5 mg 4ADNT L-1. However, root and shoot development was reduced, and respiration was depressed at 15 mg 4ADNT L-1. Our observations indicate a potential use of tall fescue in remediation of soil marginally contaminated with munitions residues.

Keyword(s): TNT, 4ADNT, phytoremediation, tall fescue, Festuca arundinacea.

Poster presentation.

The occurrence of migration of colloidal particles through subsurface environments is extensively studied and well acknowledged. Several field studies have indicated the transport of microorganisms and colloidal matter through the subsurface. Therefore, a proper understanding of mechanisms and quantification of particle transport is essential to predict the contaminant migration in ground water. In this work a mathematical model to predict particle transport through porous media is presented. The important feature of this model is the representation of soil matrix as a cluster of pore tubes of different diameters. The effects of various parameters responsible for the particle transport and deposition such as pH, ionic strength, fluid properties, particle density and concentration are accounted for in the model. The effects of these factors are incorporated through the utilization of a single combined parameter.

The effects due to the variation of geometry of the medium and changes in pore size distribution are also taken into account in the model formulation. A numerical solution was obtained by using finite difference scheme to estimate the rate of change of particle concentration and net deposition of particles. The sensitivity analysis of model parameters was also conducted. The main advantages of this model are (1) it incorporates a unique and efficient scheme to account for particle deposition at various spatial and temporal levels; (2) it can be easily modified to estimate facilitated transport of contaminants; and (3) the numerical scheme is simple, and an efficient solution can be achieved without loss of generality.

Keyword(s): colloids, concentration, density, porous media.

Oral presentation in fate and transport session.

Validation of a 3-D, finite clement, multi- phase code, FEHMN (Finite Element Heat and Mass Nuclear) developed at Los Alamos National Laboratory was performed. Results from an isothermal 2-D tank experiment involving the injection of a dense NAPL into an initially water-saturated, 3- layered heterogeneous porous medium were used for validation of the code. Quantitative data obtained during the experiment include saturation distributions within the 2-D tank at various times using a dual gamma system, injected mass of NAPL over time, and visual propagation of the NAPL front dyed red. Based on the results of the numerical simulations, additional, more focused 2-D tank experiments were proposed for further model validation. This validated model will be used in our future research efforts on up- scaling of multi-phase flow parameters to field problems.

Keyword(s): multi-phase flow, NAPLs, numerical modeling.

Oral presentation in non-aqueous phase liquids session.

Use of thermal processes, such as hot water flooding and steam injection for the enhanced recovery of entrapped hydrocarbons from petroleum reservoirs have been practiced in the oil industry. The potential exists for the use of similar techniques for the mobilization and recovery of non-aqueous phase (NAPL) waste products from soils in contaminated aquifers. However, the direct application of these techniques for aquifer remediation is precluded due to some basic differences associated with the problem of scale, types of chemicals, expected cleanup levels and heterogeneities in aquifers. In our ongoing research, we are investigating the use of hot water for the mobilization of entrapped NAPLs under micro and macroscale entrapment saturations. The objectives of this research are to understand and model the mobilization process at various scales of interest, from the laboratory to the field scale.

This paper presents preliminary results from mobilization experiments that were conducted in soil columns. Sand is packed homogeneously in a vertical column that was placed in a temperature controlled insulated chamber. The bottom of the column is fitted with a base to which a high- suction (bubbling pressure) porous plate can be attached. After saturating the dry soil with the test NAPL, the column was drained at the bottom. Suction was then applied at the bottom to create residual saturation. After removing the porous plate, hot water at a known constant temperature was pumped from the bottom of the column. The effluent was sampled continuously to determine the volume of mobilized NAPL. The NAPL saturation in the column was monitored using a dual gamma attenuation system. The experiments were repeated for different temperatures of hot water (10 -50 C), sand types and flooding velocities. The data was analyzed to determine the recovery efficiencies. The research results from these experiments will be used to design mobilization experiments in two-dimensional tanks to evaluate the recovery efficiencies in more realistic field systems where the flow is multi-dimensional and heterogeneities control the flow behavior.

Keyword(s): ground water, NAPL, remediation, thermally enhanced recovery, up-scaling.

Oral presentation in non-aqueous phase liquids session.

The residual NAPL (non-aqueous phase liquid) ganglia remain entrapped in the saturated domain, posing a problem of paramount importance in ground water remediation. This paper addresses pumping with either pulsed or monotonic accelerations to recover trapped NAPL. Laboratory tests were conducted on both glass beads and sands to investigate the mechanisms involved. The results reveal that the durations of the accelerations are as important as the magnitudes in causing recovery. Th