LEACHING OF HEAVY METALS IN SOIL COLUMNS UNDER UNSATURATED CONDITIONS

Vast areas of abandoned mine tailings in southeast Kansas are to be reclaimed by covering them with topsoil and revegetating. Although this procedure will reduce wind erosion and runoff of heavy metal contamination, the impact on leaching of metals is not known. A greenhouse experiment was initiated to measure the changes in metal mobility resulting from covering mine tailings with up to 60 cm of soil and establishing vegetation. Columns with different depths of topsoil over tailings were planted with a cool- season grass (tall fescue, Festuca arundinacea Schreb), and a warm-season grass (big bluestem Andropogon gerardii Vitm.). Duplicate columns for each treatment were prepared for unsaturated flow and leached with 0.001 M CaCl2 at a flow rate of 3.8 L/s. A vacuum (0.03 MPa) was applied to the bottom of the column, and effluents were collected every 24 h. The concentrations of cadmium, lead and zinc in the leachate were measured. After six months, plants were harvested and analyzed for heavy metals. Sequential extractions of column subsoil will be conducted to evaluate different metal forms labile for leaching.

Keyword(s): heavy metals, leaching, unsaturated flow.

Oral presentation in research track.

The U.S. Bureau of Mines, Salt Lake City Research Center (SLRC), is investigating the biological reduction of selenate and selenite to develop a bioreactor for selenium removal from various processes and wastewaters. Indigenous selenium-reducing microorganisms vary somewhat from site to site and overgrowth of an established indigenous selenium-reducing microbial population by other indigenous nonselenium-reducing bacteria can pose a major bioreactor problem. In attempts to overcome this problem, the SLRC has used a consortium of selenium-reducing bacterial isolates as biofilms and immobilized in alginate beads to treat wastewaters containing 0.6 to 30.0 mg/L selenium. Reduction of both selenate and selenite to elemental selenium was obtained. Selenium reduction has been observed in a variety of bacteria under both aerobic and microaerophilic conditions. The SLRC has also used immobilized crude enzyme preparations to remove selenium from mining process solutions. The enzyme preparations reduced selenium in process solutions containing 100 mg/L cyanide; selenium- reducing bacteria are not cyanide tolerant. In laboratory tests, over 98% selenium removal has been attained using mining wastewaters.

Keyword(s): selenium reduction, bacteria, enzyme, immobilization.

Poster presentation.

Predictions of bacterial transport/attenuation during passage through porous media are widely based on filtration theory. Cell-collector affinity, in this context the fraction of collisions between the biocolloid and collector material that result in bacterial sorption, is generally represented by a single value, a, that must be empirically determined. This is often accomplished through bench-scale simulations of field-scale situations. Using radiolabeled bacteria to measure biocolloid retention within a uniform bed of spherical borosilicate beads in a bench-scale reactor, we have shown that there is a wide range of affinities, or a values, within even monoclonal bacterial populations. A probability density function (PDF) representing the distribution of a values in a population of deep subsurface bacteria was mathematically deduced. That PDF was then used to test the importance of such variation in scaling from laboratory results for prediction of bacterial transport in large reactors or in the field. Prediction of far-field concentrations of residual microorganisms proved extremely sensitive to the representation of a values in the bacterial population.

Keyword(s): biocolloid transport, porous media, heterogeneities, modeling.

Poster presentation.

Hard rock mining has been an important factor in the development of Montana as well as many western states for over one hundred years. As a result of these past mining operations that occurred prior to the passage of the mined land reclamation and other environmental statutes, mining was not regulated. Therefore many environmental degradation and reclamation problems exist at these "pre-law" mining sites that are abandoned or inactive today.

In an effort to eliminate the environmental degradation problems at these sites, the State of Montana, through the Montana Abandoned Mine Reclamation Bureau completed an inventory that identified some 6,000 sites, many of which require some form of reclamation/cleanup. It soon became apparent that the number of the abandoned and inactive mines needing cleanup far exceeded the Abandoned Mine Reclamation Bureau's ability to address this number of sites. Additionally, it was determined that many of these sites had multiple surface and mineral owners, including private, federal and state lands, as well as hazardous substances. These factors further complicate the issues of Responsible Party determination, responsibility for cleanup, and the cleanup standards that need to be met.

This presentation addresses the actual hands- on problems that need to be resolved when trying to coordinate and implement environmental cleanup and reclamation at these kinds of sites.

Keyword(s): hard rock mining, reclamation, inventory, hazardous substances, responsible parties.

Oral presentation in research track.

The National Institute of Environmental Health Sciences (NIEHS) Superfund Basic Research and Training Program (SBRP) was established in 1986 by the Superfund Amendments and Reauthorization Act (SARA). This is a unique program of basic research and training grants directed towards understanding, assessing and attenuating the adverse effects on human health resulting from exposure to hazardous substances. Grants made under the SBRP are for coordinated, multicomponent, interdisciplinary studies. The program's primary goal is to provide an opportunity for researchers from the biomedical sciences, engineering, ecology, and the geosciences to explore the scope of the problems of uncontrolled hazardous waste and seek solutions. The program, now in its eighth year, is designed to provide a broader and more detailed body of scientific information to the field of environmental management. The research findings from this program are being used by state, local, and federal agencies, private organizations and industry in making decisions related to the management of hazardous substances.

Many innovative technologies for detecting, assessing and reducing toxic materials in the environment have been developed as a result of funding by the SBRP. To assist grantees, the SBRP has developed a technology transfer strategy designed to handle the unique problems associated with transferring multidisciplinary technology from basic research to applied research. By 1995 this will result in the validation of many of the research products being generated by this program as driven by technology demonstrations and commercialization. A number of these novel technologies are presented. The SBRP has actively pursued increasing the availability of these findings to the scientific community. Currently, the database detailing each program is available through the NIEHS Gopher server on the Internet. A description of how to access this system is given. To encourage the interdisciplinary nature of the program, the SBRP has strongly encouraged grantees’ participation in scientific conferences and workshops. A listing of conferences and workshops sponsored by the SBRP for the years of 1993-1994 will be presented.

Keyword(s): superfund, technology transfer, database.

Poster presentation.

Biohydrometallurgy is the science and engineering concerned with the extraction of chemical elements from ores, concentrates and rocks through the solubilizing action of microorganisms. Acidophilic bacteria, especially Thiobacillus, are associated with this process and are used commercially in bioleaching (heap leaching.) These naturally occurring microorganisms also increase the rate at which acid mine (rock) drainage occurs. Traditional studies do not easily allow visualization of bioleaching. Flowthrough cell techniques adapted from biocorrosion/biofilm research used at Montana State University's Center for Biofilm Engineering will be presented and discussed. Comparisons between these new methods will be made with the more traditional batch/column studies, usually associated with biohydrometallurgical research.

Keyword(s): biohydrometallurgy, bioleaching, biofilm, Thiobacillus, techniques.

Oral presentation in research track.

The differential soil bioreactor is a continuous- flow, laboratory treatability-study device in which groundwater, supplemented with nutrients, is recirculated through a disc of aquifer material at a rate that simulates actual groundwater flow. A high recycle ratio ensures that all bacteria in the disc are exposed to the same physiochemical environment, so rate and yield parameters needed for modeling in-situ bioremediation can, in principle, be derived directly from measurements of inlet and outlet concentrations of contaminants, nutrients and cells. Results are shown for the biodegradation of trichloroethylene by methanotrophic bacteria in sediments from the Savannah River site. The limitations of the technique for slow-flowing aquifers are discussed.

Keyword(s): in-situ, bioremediation, trichloroethylene, methanotrophs.

Oral presentation in research track.

The transport of bacteriophages MS-2 and PRD-1 through three different saturated porous media formations were investigated in a two- dimensional pilot-scale flume (10m L, 0.05m W and 1.2 H), located in the Hydraulics Laboratory of the University of Colorado at Boulder. The migration of the virus-sized biocolloids co- injected with a bromide tracer were monitored in both space and time using up to fifteen sampling ports along the length of the flume. The three different simulated aquifer formations—a cross section of #30 sand (U.S. sieve size) homogeneously packed; a cross section of #30 sand, #8 sand (10 cm layer) and #30 sand; and a cross section of #30 sand, #30 sand coated with iron oxides (10 cm layer) and #30 sand—highlight the influences of physical and chemical aquifer media heterogeneities on the migration of virus- sized biocolloids. Included in this discussion is a description of the pilot-scale design and associated boundary conditions, methods for positioning injection and sampling points, techniques for packing and pre-experimental monitoring, approaches for analyzing and extrapolating information from breakthrough curves, and results from the experiments.

Keyword(s): biocolloid, transport, heterogeneities.

Oral presentation in research track.

Processes have been developed for the restoration of environments contaminated with hydrocarbons and heavy organics. The intended product is a field deployable materials handling system and phase separation process ranging in size from 1 yd3/hr to 50 yd3/hr for commercial application to environmental problems associated with the exploration, production, refining and transport of petroleum, petroleum products and organic chemicals. Effluents from contaminated sites will be clean solids (classified by size if appropriate), and the concentrated contaminant.

The technology is based on biochemical solvation, liquid/liquid and liquid/solid extractions, materials classification, mechanical and hydraulic scrubbing, and phase separation of organic and aqueous phases. Fluid use is minimized through utilization of closed-loop (recycle) systems.

Contaminants that are removed from the solid material may be destroyed, disposed of using existing technologies, or used on-site for cogeneration of power for plant operations.

Additionally, if the contaminant is a valued product, the material may be recovered for application or sale. Clean solid material is not sterilized and may be returned to normal agricultural, commercial, residential or recreational use in most instances.

Keyword(s): hydrocarbon removal, restoration, petroleum contaminants.

Oral presentation in technology transfer track.

A common environmental problem associated with the pumping and refining of crude oil is the disposal of petroleum sludge. This sludge is often treated by incorporation into the soil. If the soil is frequently tilled and fertilized, soil microorganisms will be stimulated and organic contaminants biodegraded. Unfortunately, the biodegradation rate of more recalcitrant and potentially toxic contaminants, such as the polynuclear aromatic hydrocarbons (PNAs), is rapid at first but declines quickly. Biodegradation of these compounds is limited by their strong adsorption potential and low solubility.

Recent research has suggested that vegetation may play an important role in the biodegradation of toxic organic chemicals, such as PNAs, in soil.

The establishment of vegetation on hazardous waste sites may be an economic, effective, low maintenance approach to waste remediation and stabilization. The use of plants for remediation may be especially well-suited for soils contaminated by organic chemicals to depths of less than 2 meters. The beneficial effects of vegetation on the biodegradation of hazardous organics are two-fold: organic contaminants may be taken up by the plant and accumulated, metabolized, or volatilized, and the rhizosphere microflora may accelerate biodegradation of the contaminants.

Completed greenhouse studies have indicated that vegetative remediation is a feasible method for clean-up of surface soil contaminated with petroleum products. However, a field demonstration is needed to exhibit this new technology to the industrial community. In this project, several petroleum contaminated field sites will be chosen in collaboration with three industrial partners. These sites will be thoroughly characterized for chemical properties, physical properties, and initial PNA concentrations. A variety of plant species will be established on the sites, including warm and cool season grasses and alfalfa Soil analyses for the target compounds over time will allow us to assess the efficiency and applicability of this remediation method.

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

Poster presentation.

Nitrogen oxides (NOx) are primary air pollutants and, as such, there is considerable interest in the development of efficient, cost effective technologies to remediate NOx containing emissions. Biofiltration involves the venting of contaminated gas streams through biologically active material such as soil or compost. This technology has been used successfully to control odors as well as volatile organic compounds from a variety of industrial and public sources. The purpose of this study was to evaluate the feasibility of using biofiltration to convert NOx to nitrogen gas.

Bioreactor studies measuring nitric oxide (NO) removal by bacteria indigenous to coniferous wood compost were conducted. Vertical bioreactors (2 l volume) were constructed using glass process pipe (12 in. x 3 in.). Compaction of the compost in the bioreactors was minimized by the addition of wood chips (17% w/w) measuring approximately 1.2-1.5 cm in diameter. The compost/bark mixture was ten loaded (1.4 l) into the columns. A nitrogen gas stream containing various concentrations of NO (100-500 µl l-1) was purged (1 l min-1) through the compost under single pass continuous flow conditions. The effects of moisture, pH, temperature and exogenous carbon sources on nitric oxide removal in the biofilters were investigated.

Moisture measurements during nitric oxide removal experiments indicated that biological activity was optimum when the compost was moist but not saturated (9-12 centibars of soil suction). Studies demonstrated that pH control in the biofilter was a critical variable for maximum nitric oxide removal. Optimum denitrifying activity occurred at pH levels ranging between 6- 7. Nitric oxide removal rates were found to increase in biofilters treated with an external carbon and energy source. Biofilters maintained at 37ºC and treated with lactate were shown capable of removing ³90% of the nitric oxide from an influent gas stream containing 500 ml/l NO.

Keyword(s): nitrogen oxides, biofiltration, denitrification.

Oral presentation in research track.

Elemental iron and zinc have been used to reductively convert part-per-thousand levels of aqueous-phase tetrachloromethane to trichloromethane in a few hours. Products include free metal irons, chloride ion and hydrogen gas.

Hydrogen ions are consumed. Process kinetics are dependent on solution pH, surface area of the elemental metal, tetrachloromethane concentration, and buffer selection. In mixed solvent experiments, conversion kinetics and process stoichiometry were dependent on the alcohol that was added to water. When isopropanol was added, acetone was among the suite of products. Dehalogenation reactions using elemental metals as reductants offer promise as a means for initiating the destruction of heavily halogenated aliphatic compounds. However, models of process mechanism, and therefore factors that will influence remediation designs, are incomplete. The results of recent experiments will be described.

Keyword(s): reductive dehalogenation, elemental metals, groundwater remediation, tetrachloromethane.

Poster presentation.

In 1990, the Department of Energy approved a cooperative agreement for a Waste-management Education and Research Consortium (WERC) program. This consortium includes as its members the New Mexico State University (NMSU), the University of New Mexico (UNM), the New Mexico Institute of Mining and Technology (NMIMT), the Navajo Community College, the Los Alamos National Laboratory, and the Sandia National Laboratories working with industrial affiliates.

The formative years have conclusively demonstrated that the partnership of universities, national laboratories and industry developed by WERC is an effective tool for education, technology development and technology transfer, with the education process also playing a critical role in technology transfer.

The university/national laboratory/industry partnership of WERC has resulted in unique solutions to technology issues. These have attained the demonstration stage at DOE and industry sites within the short period of three years after the start of the program. Further, the program has resulted in students with conventional course type education as well as experience on practical development projects at the leading edge of technology, thus forming a base for technology transfer as these students flow into government and industry jobs. Several of our past students occupy responsible positions and are already technology transfer agents.

Several of the unique technologies developed via WERC are successfully demonstrated via application at national laboratories and industrial sites. Examples are listed below.

Remediation of soil contaminated with plutonium using a polymer capture process has been applied at a DOE waste site.

Subsurface mapping of buried waste has been applied at a DOE integrated demonstration (ID) site.

A pipeline detection system has been applied to leak detection from storage tanks and pipelines in the oil industry.

This paper will present how the WERC partnership has been successful because of its unique structure and method of operation.

Keyword(s): technology transfer, partnerships, education.

Oral presentation in technology transfer track.

The kinetics of the transformation of volatile chlorocarbons in water solution in the presence of the zero-valence metal particles was studied using Gas Chromatography and Gas Chromatography/Mass spectroscopy. Metals including magnesium, zinc, tin were exposed to a low concentration (100 to 1000 ul L-l) of carbon tetrachloride in water. Tin caused the degradation of carbon tetrachloride and appearance of carbon dioxide, chloroform and tin oxide. The transformation of chlorocarbons was found to depend on the surface properties of the metal particles.

Keyword(s): metal particles, chlorocarbons, water, degradation.

Oral presentation in research track.

2,4-D is a widely used systemic herbicide for the control of broadleaf weeds in grain crops, field corn, pastures, and other crop and non-crop land.

This herbicide also has a large market in home and garden use. Under aerobic conditions, 2,4-D is rapidly degraded by microbes in soil.

Groundwater contamination is limited due to the pesticide’s high rate of microbial degradation and uptake by plants. Groundwater is susceptible to contamination at point sources where 2,4-D is formulated, loaded onto application equipment, and at clean-up areas where large amounts of rinseates can be produced. We have developed an aerobic biological process to degrade 2,4-D found in these rinseates and other water which may have contamination. This process involves establishing an environment in which a known 2,4-D degrading bacterium can utilize the herbicide as a carbon source and achieve mineralization to carbon dioxide and water. The environment conducive to 2,4-D degradation is produced by using an inexpensive nitrogen and phosphate source such as agricultural grade diammoniumphosphate and monoammoniumphosphate producing a buffer.

Oxygen is provided by vigorous aeration of the water with compressed air. The bacterium used is Alcaligenes eutrophus JMP134 (pJP4). The organism is produced in large amounts at relatively low cost by fermentation. The organism is air dried on peat and has exhibited good survival and degradation capabilities when stored at room temperature in a desiccated form for at least 60 days. This process has been successfully tested on rinseates produced by the cleaning of commercial spray rigs applying the herbicide Curtail®. Optimum physical parameters for the process such as pH, temperature, inoculam amounts, and buffer concentrations have been determined.

Keyword(s): 2,4-D, degradation, rinseates.

Poster presentation.

The field site was manipulated with injection of air (control experiment), 1% methane (in air), pulsing of air only and 4% methane, and pulsing of 4% methane supplemented with gaseous forms of nitrogen and phosphorous. Gases were injected through a horizontal well into the aquifer and a vacuum was established in a second horizontal well in the vadose zone. Following each injection regime, sediment samples from the contaminated region (100-140 feet below ground surface) were analyzed. Analyses included most-probable- number enrichments for physiological groups known or suspected to degrade trichloroethylene (TCE) and per-chloroethylene (PCE), TCE and PCE removal from enrichments, and DNA extraction and hybridization with various gene probes corresponding to enzymes known to degrade TCE or TCE metabolites.

Culturable populations in sediments following methane pulsing plus nitrogen and phosphorous (+ N + P) compared to pre-methane sediments showed methanotrophs increased 0 to >3 orders of magnitude (to >2400/g), propane-oxidizers increased 2 to >3 orders of mag (to >2400/g), and ammonia-oxidizers increased 2 to >4 orders of magnitude (to >24000/g). These three microbial trophic groups are known to degrade TCE.

Culturable methylotroph populations increased 1 to >2 orders of magnitude (to >2400/g) and culturable anaerobes showed little to no increase.

Following methane pulsing + N + P, TCE and PCE removal occurred in methanotrophic enrichments for most sediments with 1 mg of inoculum and 100 mg of inoculum, respectively.

In contrast, TCE and PCE removal in methanotrophic enrichments from pre-methane sediments rarely occurred with 1 g of inoculum. A messenger RNA probe corresponding to the soluble methane monooxygenase gene showed that the cultural methods underestimated the density of the gene in sediments by several orders of magnitude. The underestimation occurred during all injection regimes but was most severe following the 1% methane injection. Populations of TCE-degrading microorganisms corresponded with increases in contaminant removal in vadose zone piezometers and groundwater, strongly suggesting that microorganisms were responsible for much of the TCE and PCE removal.

Keyword(s): bioremediation, trichloroethylene, nucleic acid probes, methanotrophs.

Oral presentation in research track.

This work was supported by the U.S. Department of Energy as part of Pacific Northwest Laboratory’s Laboratory Directed Research and Development. Pacific Northwest Laboratory is operated for the U.S. Department of Energy by Battelle Memorial Institute under contract DE-AC06-76RLO 1830.

Plants have profound effects on physical, chemical and biological processes in soils and can potentially accelerate the rate of degradation of hazardous organic chemicals. Quantitative information describing the effects of vegetation on the fate of organic chemicals in soils is needed to increase our general understanding of the fate process and evaluate the potential use of plants in enhancing the remediation of contaminated soils.

This study was designed to examine rates and extent of degradation by the plant/soil system, as well as plant uptake, accumulation and metabolism, for several representative organic chemicals. A flow-through system, consisting of six modules, was designed to accommodate rapid flow rates through the plant growth chamber. Rapid flow rates prevent condensation in the chamber and also prevent the unnatural accumulation of volatile compounds in the chamber air. Each system module consisted of planted or unplanted soil covered with a glass bell jar, through which passed a continuous stream of air. Bell jars stood in a growth chamber, and plants (or soil controls) were kept at 23 ± 1 C, with a 16 hr photoperiod. Pre- and post-chamber flow rates were carefully balanced to minimize pressure gradients and thus minimize air leaks. Six such modules ran simultaneously, three each for the planted and unplanted systems.

Radiolabeled (14C) and non-radiolabeled aromatic hydrocarbons, dissolved in ethanol, were added to the soil to yield a concentration of approximately 100 mg/g dry weight of soil. Plants were started from seed at the beginning of a trial.

Concentrations of the 14C labeled test compounds in the vapor, plant and soil phases were determined, after appropriate extraction and/or concentration techniques, by liquid scintillation counting. Preliminary results, using the system and procedures described above, show that mineralization of the test aromatic hydrocarbons is significantly greater in the rhizosphere soil than in the unplanted soil after two weeks.

Keyword(s): plants, biodegradation, organic contaminants.

Oral presentation in research track.

The wood rotting Basidiomycete Phanerochaete chrysosporium is able to degrade a wide variety of environmentally persistent organic pollutants to carbon dioxide. The unique biodegradative abilities of this fungus are due, in part, to lignin peroxidases, oxidative enzymes that are secreted in response to nutrient deprivation. Lignin peroxidases catalyze the initial oxidation of many of the organic pollutants that are degraded by this fungus. Lignin peroxidases mediate the initial oxidation of N,N,N',N',N",N"- hexamethylpararosaniline, several azo dyes and certain polycyclic aromatic hydrocarbons. Lignin peroxidases also mediate oxidative dechlorination.

For example, lignin peroxidases oxidize pentachlorophenol to 2,3,5,6-tetrachloro- 2,5cyclohexadiene-1,4-dione. Similarly these enzymes mediate oxidative oligomerization of 4- chloroaniline resulting in production of several dimers, trimers and tetramers and net dechlorination of the aromatic ring. Interestingly, many, but not all, of the reactions mediated by lignin peroxidases are also mediated by other plant, fungal and mammalian peroxidases. In some instances the major role of lignin peroxidases is the oxidation an intermediate. In the case of phenanthrene degradation lignin peroxidases do not mediate the initial oxidation.

However, these enzymes do mediate the oxidation of 9-Phenanthrol, forming Phenanthrene-9,10- dione. This is of interest because 9-Phenanthrol is a major metabolite formed under nonligninolytic conditions while Phenanthrene-9,10-dione is a major metabolite formed in ligninolytic cultures.

Thus, in this case, lignin peroxidases appear to link the pathway occurring under nonligninolytic conditions with the pathway that predominates in ligninolytic cultures. (Supported by NIEHS grant ESO 4492.)

Keyword(s): Phanerochaete chrysosporium, lignin peroxidase, biodegradation.

Poster presentation.

A laboratory study was conducted to determine whether the concentration of heavy metals, zinc (Zn), lead (Pb), and cadmium (Cd), in leachate from mine tailings could be affected by the presence of organic acids exuded by plant roots and microbes in the rhizosphere. Geochemical modeling predicted that some organic ligands found in the rhizosphere have the capability to complex and increase the solubility of Zn. The leachate was analyzed for Zn, Pb and Cd content and for organic acid concentration. These results were confirmed by batch and column studies in which mine tailings were exposed to 0 to 10,000 mM organic acids.

Keyword(s): heavy metals, organic acids, rhizosphere, plants.

Oral presentation in research track.

The Mine Waste Technology Pilot Program (per published material) is involved with testing technologies to clean up mine and mineral waste and with the education and training of people who are or will be involved with mine waste issues.

The education component is a part of the larger MWTPP, sponsored by The Environmental Protection Agency through The Department of Energy, and administered by MSE, Inc., in Butte, Montana. Montana Tech's education role is to implement the following four point program: Master of Science degree with a mine and mineral waste emphasis, providing students with enhanced exposure to the interdisciplinary field of mine waste processing under existing engineering/science graduate programs; awards fellowships, graduate research assistantships, and graduate teaching assistantships; educational and training opportunities for industry professionals through specialized workshops; and educational opportunities for students and teachers, from kindergarten through high school.

In 1990, the Department of Energy approved a cooperative agreement for a Waste-Management Education and Research Consortium.. This consortium includes as its members the New Mexico State University, the University of Mexico, the New Mexico Institute of Mining and Technology, the Navajo Community College, the Los Alamos National Laboratory, and the Sandia National Laboratories. The model five year program was assigned the mission of demonstrating that a university/national laboratory partnership can effectively expand the nation’s capability to address the issues related to management of all types of waste via education and technology development. This partnership of universities, national laboratories, and industry developed by WERC is an effective tool for education, technology development, and technology transfer, with the education process playing a critical role in technology transfer. The WERC program is available to over 3000 students in academic institutions with a minority population of 25-95%.

Keyword(s): mine, hazardous, waste, education, university.

Oral presentation in research track.

The study reported here investigated the overall effect poplar trees exert on the fate and transport of atrazine in a variety of soil types. The research was conducted in batch reactors.

Reactors utilizing small poplar cuttings, reactors quantifying sorption/desorbtion phenomenon, and reactors dosed with surrogate and actual poplar root exudate were prepared containing a silica sand or a silt-loam soil. The atrazine fate was monitored by the use of atrazine labeled with carbon-14 isotopes. The extent of uptake in the poplars was then quantified through oxidation of the poplar biomass followed by liquid scintillation techniques. Experimental results indicate that virtually all of the atrazine in sand can be taken up by the poplars in a reasonably short amount of time, with little adverse effects on the trees. In organic soils, the poplars can take up only mobil atrazine which is not bound to the soil. Results also indicate that the poplars have either a positive effect or no detrimental effect on all fate and transport mechanisms studied. This would indicate that poplar trees may have a promising future in the role of remediation of pesticide contaminated waters.

Keyword(s): atrazine, pesticides, poplars, remediation.

Oral presentation in research track.

A field application using sulfate-reducing bacteria (SRB) to treat acidic mine water discharging from the Lilly/Orphan Boy Mine near Elliston, Montana, is described. The field application is a project under the MWTPP implemented by MSE, Inc., funded by the U.S. Environmental Protection Agency (EPA), and jointly administered by the EPA and the Department of Energy. The design of the field application involves using a flooded mine shaft as an in-situ biological reactor to which organic substrate and SRB will be added. Technical parameters required for the field application are presently being developed from laboratory testing of SRB in packed-bed reactors.

Keyword(s): sulfate-reducing bacteria, acid rock drainage.

Oral presentation in research track.

Creosote contaminated sites are of environmental significance due to the high concentrations of toxic and/or mutagenic PAH usually found at these sites. Microbial degradation of PAH can be seen as a novel form of contaminant detoxification. This paper describes the microbial degradation of PAH in creosote contaminated soils using (9-14C) phenanthrene as a model PAH. Microbial metabolism was assessed with a mass balance approach as well as identification of PAH metabolites by GC/MS/FTIR. The mass balance accounted for the amount portion of the added phenanthrene. To confirm the effectiveness of microbial degradation to decrease soil toxicity, the Microtox® and Mutatox® assays were used to monitor toxicity of the creosote soils throughout the experiments.

Mass balance results indicated that phenanthrene was readily mineralized in the contaminated soils, while metabolite production accounted for only a minor portion of the added phenanthrene. Toxicity of contaminated soils increased slightly early in the incubation and then decreased over longer time periods. Mutagenicity of soils, however, did not decrease appreciably over a 3-month time period. The identity of metabolic products found in the soils will be discussed.z

Keyword(s): polycyclic aromatic hydrocarbons, biodegradation, metabolite production, Microtox®/Mutatox®.

Poster presentation.

Complex mixtures of polynuclear aromatic hydrocarbons (PAHs) are organic combustion products and are components of creosote and oily wastes which have been identified in a large number of hazardous chemical waste sites. Risk assessment of PAH mixtures must take into account the toxicity or carcinogenicity of the individual compounds and their possible additive or nonadditive interactive effects. A reconstituted PAH mixture which resembled manufactured gas plant PAH residues was prepared using 16 different compounds and the immunotoxicity and monooxygenase induction activity of the 2-ring, 3-ring and ³ 4-ring PAHs were compared to that observed for the reconstituted mixtures in B6C3F1 mice. The results showed that the reconstituted mixture inhibited the splenic plaque- forming cell response to T-cell dependent and independent antigens and induced hepatic microsomal ethoxyresorufin O-deethylase activity and Cyp1a-1 mRNA levels. The relative potencies of the reconstituted mixture and its components indicated that most of the activity was associated with ³ 4-ring PAHs and the interactive effects of the individual PAHs in the reconstituted PAH mixture were essentially additive. This research was supported by the Electric Power Research Institute and the National Institute for Environmental Health Sciences (P42 ES04917).

Keyword(s): polynuclear aromatic hydrocarbons, interactive effects.

Poster presentation.

Contamination of soils with polychlorinated biphenyls at industrial and military sites is a significant problem. A process based on supercritical carbon dioxide extraction of polychlorinated biphenyls from the soil followed by supercritical water oxidation of the extract appears to be economically attractive with the benefit of returning clean soils/sediments to the environment. Our research objective is to assess the technical feasibility of this process and provide data for economic evaluation.

Results of desorption rate studies of Aroclor 1248 from soils and sediments will be presented. Data were acquired on a continuous flow fixed- bed laboratory-scale supercritical extraction unit. The experimental range of variables include: 30 to 50 C, 75 to 400 atmospheres, soil/sediment sample size of 8 grams, carbon dioxide flow rate of 0.02 to 0.54 grams/second, modifier flows 0.0 - 5 mole %, moisture content 0.0 to 20 weight %, and initial polychlorinated biphenyl concentration of 500 to 10,000 parts per million. The soils (sand, clay, till and surfacial soil) and sediment samples are representative of a specific Superfund Hazardous Waste Site in New York State. Contact time needed for sub 5 parts per million residual polychlorinated biphenyl concentrations range from 30 to 90 minutes depending on soil type, level of contamination, and conditions of contacting. A desorption rate model is presented to model the data. Also, solubility data of specific polychlorinated biphenyl congeners were obtained and modeled using the Peng-Robinson equation of state. These results will also be presented. Future work involving bench-scale studies with a 1.0 liter system will be described.

Keyword(s): supercritical extraction, carbon dioxide, polychlorinated biphenyls.

Oral presentation in research track.

Biodegradation of pentachlorophenol by Phanerochaete chrysosporium was examined in nonsterile soil. The rate of mineralization of pentachlorophenol was essentially linear for at least 27 days and increased almost linearly with increasing concentration of pentachlorophenol (from 50 to 1600 parts per million). With an initial concentration of 100 parts per million, no pentachlorophenol was found at 18 days while 40% of the added pentachlorophenol was present as pentachloroanisole, and mineralization continued linearly. Both pentachlorophenol and pentachloroanisole were found after 18 days when the initial concentration of pentachlorophenol was 800 parts per million. The rate of mineralization of pentachloroanisole also increased with increasing concentration of pentachloroanisole, however the increase was not linear. Essentially no radioactivity was found in either the aqueous or volatile organic fraction during the mineralization of either pentachlorophenol or pentachloroanisole.

Keyword(s): pentachlorophenol, pentachloroanisole, Phanerochaete chrysosporium, white rot fungi.

Oral presentation in research track.

A method for enumerating subsurface soil bacteria by direct epifluorescent microscopy was developed. The dyes DAPI (4, 6-diamidino-2 phenylindole) and CTC (5-cyano-2,3 ditolyl tetrazolium chloride) were used to assess total and viable cells, respectively. The DAPI-CTC method was compared in the laboratory to an INT-AO [(2- (p-iodopheny)-3-(p-nitropheny)-5-phenyl tetrazolium chloride]-[acridine orange] method and viable plate counts. The DAPI-CTC method was found to adequately evaluate microbial numbers.

Keyword(s): epifluorescent microscopy, subsurface, microbes, soil microflora.

Poster presentation.

Soil cores were obtained from the vadose zone of the Konza Prairie. Tempe cells and rigid-wall permeameters were used to determine water characteristic curves and saturated hydraulic conductivity. Runoff plots, neutron access tubes, and automated rain gauges were installed at the two sites to determine runoff, soil moisture, and rainfall amounts. A mathematical model was developed to predict the movement of water through the vadose zone using the soil hydraulic properties and surface water balance.

Keyword(s): vadose zone, soil hydraulic properties.

Poster presentation.

Missouri has a long history of lead mining activities. One of the most productive areas was in the southwest part of the state in what was called the "Tri-State District." It received this name because the ore deposits were in Kansas and Oklahoma, as well as Missouri. About 40% of all the ore came from Missouri. Mining in this region began in 1848, with production ending in 1957. The tailings or mining wastes were stored on the surface, where an estimated 8 million cubic yards remains today.

Because of the high levels of lead in the area, several superfund sites have now been designated in the "District." A cooperative study was done by Region VII EPA, Missouri Department of Health, and the Centers for Disease Control (CDC). Blood samples, dust, soil, water and paint samples were collected from 150 houses where young children lived in the Joplin, Missouri, area. The dust and soil samples were split and part was sent to the University of Missouri for analysis by sequential extraction in order to determine the environmental availability and possible bioavailability of lead. The dust samples were determined to be significantly more available than the soil. Other relationships including correlation with blood lead results will be presented.

Keyword(s): bioavailability, lead, soil, dust.

Oral presentation in research track.

Manufacturing and handling of conventional munitions have produced explosives-contaminated soil at numerous military installations. These soils pose both a reactivity and toxicity hazard. Waste streams at manufacturing facilities further add to the problem. To prevent contamination of groundwater, facilitate clean up of contaminated sites, and bring current manufacturing plants into line with environmental regulations, practical remediation methods are being sought.

Ideally, biological treatment would eliminate anthropogenic substances by aerobic mineralization to carbon dioxide and water or anaerobic decomposition to carbon dioxide and methane, hydrogen sulfide or nitrogen. However, accumulation of toxic intermediates rather than complete degradation, has hindered widespread application of the biological approach. Also, biodegradation that performs well in the laboratory is not always as efficient when tested in the field.

Microorganisms from extreme environments are a rich source of unique metabolic pathways and unusually stable enzymes. Anaerobic enrichment cultures were started a year ago with TNT, nitrobenzene or nitrotoluene and samples of thermal water. Of the five cultures now running, one has developed a thriving consortium. Recently, samples were analyzed under the direction of Dr. Donald Crawford. A total of 1200 ppm TNT was added to the culture. Now only 41.4 ppm TNT and 2.5 ppm 4-amino-2,6 dinitrotoluene remains in the liquid, while the soil extract contains 50.0 ppm TNT and 1.1 ppm 4- amino-2,6 dinitrotoluene.

Keyword(s): TNT, biodegradation, nitro-substituted.

Poster presentation.

Biodegradation research has focused primarily on the metabolism of single pollutants by pure strains of microorganisms despite the fact that contamination of soil and water is caused more often by chemical mixtures. When available, biodegradation data for mixtures is usually cast in terms of bulk measurements like total organic carbon, which are inadequate for many applications.

In this presentation, two aspects of our research into the biodegradation of organic chemical mixtures will be discussed. First, results of biodegradation experiments with Pseudomonas putida F1 and benzene, toluene, phenol and trichloroethylene will be presented.

Biodegradation rate data were obtained for the aromatic compounds individually and in mixtures, and cometabolism of trichloroethylene with these compounds has also been studied. Mathematical models have been proposed to describe these results.

The second part of the presentation will cover the application of these results to the development of an immobilized-cell bioreactor for the cometabolic degradation of trichloroethylene. Phenomena such as competitive inhibition, induction and energy supply have been incorporated into a mathematical model. Results from bioreactor experiments will be discussed.

Keyword(s): biodegradation, kinetics, mixture, aromatics, trichloroethylene.

Oral presentation in research track.

Abiotic interactions of pentachlorophenol (PCP) on manganese oxide surfaces were investigated to determine the extent of transformation. The optimal pH and ratio of manganese oxide to PCP were determined. Sorption of PCP on manganese oxide surfaces was quantified at optimal conditions. The effectiveness of utilizing manganese oxide to remediate contaminated subsurface environments was investigated.

Keyword(s): groundwater quality, geochemistry, remediation, aquifers.

Oral presentation in research track.

Microbial bioassays have been used to assess the genotoxic hazard at more than 30 different hazardous waste sites. Environmental samples were extracted with dichloromethane and methanol, and the resulting residue tested using GC/MS analysis as well as the Salmonella Microsomal and E. coli Prophage Induction assays. At a munitions wastewater contaminated site, there was no correlation between mutagenicity in bacteria, and the risk as estimated from chemical analysis data. Samples 202 and 204 from a coal gasification site contained 72 mg/kg and 9 mg/kg benzo(a)pyrene, whereas the mutagenic responses of these samples were 231 net revertants/mg and 902 revertants/mg, respectively. The data suggest that microbial bioassays provide a valuable tool for monitoring the interactions of the components of a complex mixture.

Keyword(s): bioassay, hazardous waste, benzo(a)pyrene, trinitrotoluene.

Oral presentation in research track.

This research was supported by NIH grant P42 ES04917.

Information regarding biodegradability is critical for assessing the environmental fate and impact of organic chemicals in soil/plant systems. However, quantitative information describing the biodegradation of organic chemicals in soils and the effect of vegetation is lacking, primarily due to the difficulty and expense associated with experimentally measuring biodegradation rates. Typically, biodegradation rates in soils are determined directly by measuring the disappearance of the chemical of interest over time or indirectly by measuring evolved CO2 or O2 consumption. Indirect methods are generally simpler, less expensive and less time consuming than direct methods. The focus of this study was to develop a simple microcosm approach, utilizing measurements of O2 consumption, to investigate the biodegradability of selected organic compounds in rhizosphere soil. The microcosms consisted of 100 mL glass vials fitted with Mininert® valves and typically contained 40 grams of either rhizosphere or control soil. The rhizosphere soil was obtained from a vegetated plot, while the control soil from a unvegetated plot. All compounds were added directly to the soil, without a carrier solvent, resulting in a soil concentration of approximately 200 ppm.

Headspace concentrations of O2, converted to percent of theoretical oxygen demand (%ThOD), were analyzed over time using a gas chromatograph equipped with a thermal conductivity detector. The indirect microcosm technique provided a simple, inexpensive method for comparing the aerobic biodegradation of several aromatic hydrocarbons in rhizosphere versus soil.

Keyword(s): microcosm, biodegradation rates, plants, soil, oxygen, carbon dioxide, gas chromatography.

Oral presentation in research track.

Our nation faces a daunting challenge to clean up and protect our environment. Before launching any cleanup, one must characterize the type, concentration and extent of the contamination. During cleanup, one must monitor the progress, and after cleanup, one must often monitor the site to ensure that the cleanup was successful. Chemical characterization and monitoring techniques and methods are at the heart of executing these efforts. R&D efforts to improve capabilities can translate into major savings and improvement in environmental cleanup by reducing the unit cost of measurements (e.g., fewer steps in an analysis), reducing the time required to provide the information to the user (e.g., field analytical), or improving the quality of information (e.g., chemical speciation).

Radiochemical analysis is of particular concern to DOE, where over $300 million is expended annually on this activity. Unlike organic and inorganic analytes, which are widely found as contaminants, there has been comparatively little effort expended on improvements of radiochemical analyses. Desirable characteristics of any new methods for characterization of DOE's radiochemical contamination are faster, to reduce horrendous turnaround times cheaper, to reduce the burden on the taxpayers better performance, to achieve desired data quality objectives reduced scale and fewer steps, to minimize secondary mixed waste Methods for chemical characterization of the environment are being developed under a multitask project for DOE's Office of Technology Development within the Office of Environmental Restoration and Waste Management. The project focuses on improvement of radioanalytical methods with an emphasis on faster and cheaper routine methods. We have developed improved methods for separation of environmental levels of technetium-99, radium and actinides from soil and water; separation of actinides from soil and water matrix interferences; and isolation of strontium. We are also developing methods for simultaneous detection of multiple isotopes (including nonradionuclides) using the new instrumental technique inductively coupled plasma/mass spectrometry (ICP/MS). These ICP/MS methods would more efficiently replace alpha and beta counting techniques. Integration and automation of the separation methods with the ICP/MS methology using flow injection analysis is underway with the objectives of achieving more reproducible results, reducing labor costs, cutting analysis time, and reducing secondary waste generation through miniaturization of the process. The final product of all activities will be methods which are available (published in DOE's analytical methods compendium) and acceptable for use in regulatory situations.

Keyword(s): analytical chemistry, flow injection analysis, inductively coupled plasma/mass spectrometry, radioanalytical, separations

Poster presentation.

This work is supported by the U.S. Department of Energy, Assistant Secretary for Environmental Remediation and Waste Management, Office of Technology Development, under contract W-310109-Eng-38.

Subsurface stratigraphy plays an important role in the migration and distribution of chemical and waste products that are in the form of nonaqueous phase liquids (NAPL). In the saturated zone, coarse layers act as preferential flow channels and as pockets for fluid entrapment. The entrapment saturations resulting from these macro-scale soil heterogeneities are much larger than the residual saturations controlled by the micro-scale pore characteristics of the soil. The phenomena of preferential flow and macro-scale entrapment have been observed in our laboratory spill simulations and in the field. It is our hypothesis that they are caused by the capillary barrier effects existing at the interfaces of the coarse and fine sand formations. Precision flow experiments were conducted in soil cells to obtain quantitative data to understand the nature of these capillary barrier effects. A complete testing program was implemented with five sands using both air and a light NAPL as the non-wetting phase. The experimental design and the results are presented. The experimental results are used to identify the characteristics of the soils in layered aquifers that produce barrier effects. The results of this study will help in developing field characterization techniques to determine soil parameters needed in modeling nonaqueous phase fluid flow and entrapment in heterogeneous aquifers. This knowledge will also be useful in the design of fine soil barriers for the containment of plumes and coarse soil traps for the recovery of waste fluids.

Keyword(s): groundwater contamination, organic wastes, nonaqueous phase fluids.

Oral presentation in research track.

The Environmental Restoration Project at Sandia National Laboratories/New Mexico (SNL/NM) is tasked with performing assessments and remediation of waste sites resulting from over 40 years of weapons development and testing. Operable Unit 1295, Septic Tanks and Drainfields, includes 23 different sites at SNL/NM where hazardous and radioactive wastes may have been released into the environment. A RCRA Facility Investigation (RFI) Work Plan for the sites has been submitted to the U.S. EPA for approval. This presentation will outline the proposed technical approach for the characterization of these sites for the RFI Report and the Corrective Measures Study. The phased assessment of the sites is designed to quickly eliminate sites where contamination levels are at or below background levels and fully determine the nature and extent of contamination at the other sites. Field investigation methods and sample field-screening techniques will also be presented.

Keyword(s): septic systems, site characterization, drainfields, field screening methods.

Poster presentation.

Subsurface contaminants are frequently encountered as mixtures of nonaqueous phase liquids (NAPLs) at sites contaminated by gasoline or coal tar comprising organic mixtures. The leaching of these organic mixtures from the aquifer has been examined with and without biodegradation. The results obtained have been compared with the limiting case of a single component NAPL.

Various physical processes involved have been quantified based on the assumptions that liquid- liquid and sorption equilibria are established at the beginning of each flushing; oxygen required for biochemical oxidation is completely consumed by the end of each flushing; and the rate of biochemical oxidation obeys the Monod kinetics for a multi-substrate system, characterized by an oxygen utilization factor. This has given rise to an equilibrium model expressing the mass fraction of any component remaining in the aquifer, its aqueous concentration, and the composition of the NAPL as functions of the number of flushings. The results of the simulation with the model demonstrate that bioremediation can significantly reduce the time necessary for removing the components of intermediate solubility such as xylene. Highly soluble components of the NAPL are mainly removed by the pump-and-treat mechanism while the components of extremely low solubility are unavailable to the microbes as substrates in a multi-component system. The results also demonstrate that relatively soluble contaminants tend to persist for a longer duration in the mixture than when they exist as pure components and that this effect is magnified by the inclusion of a non-soluble component in the mixture. The proposed mass balance approach yields a useful bound of the effectiveness of biodegradation aided dissolution of a multi- component NAPL; the approach is relatively simple and computationally efficient.

Keyword(s): dissolution, biodegradation, NAPL, mixture, equilibrium.

Oral presentation in research track.

In the development and application of groundwater models, it has been recognized that the process understanding at a small scale does not necessarily lead in a straightforward manner to appropriate models at a large scale. The upscaling of models of water flow and solute transport in saturated porous media has been the topic of significant theoretical investigation. Data from a few field sites have been used to validate some of these theories. However, the field data will have limitations with respect to accuracy and the inability to fully characterize the soil conditions which define the field-scale heterogeneities. Laboratory investigations in soil columns and tanks can provide much accurate data compared to the field. Also, soils which are used to create heterogeneities can be well characterized in the laboratory. The purpose of the study reported in this paper is to develop an experimental facility to generate accurate data on water flow and solute transport in heterogeneous aquifers. The data is used to study the scale effects in solute transport (scale-dependent dispersivity). The experimental facility consists of a horizontal soil tank of dimensions 2.44 m x 1.22 m. Soil samples of approximately 5 cm thickness can be packed into the tank. Two constant head end tanks are used to create various groundwater flow velocities. Pressure measurements and solute sampling will be done over the horizontal plane using 45 sampling ports drilled through the top wall. These same ports can be used for tracer injection. The experiments will involve injection of a tracer into the flow field and measurement of water pressure and solute concentrations at prescribed locations in the flow field. Pressure measurements are done using an automated pressure scanning system. The measured values of flow, pressure and solute concentrations are used to estimate hydraulic conductivity and dispersivity using inverse problem solution techniques. Both homogeneous and heterogeneous soil packing configurations could be investigated. Results from simulations with homogeneous packing are presented.

Keyword(s): upscaling, dispersivity.

Poster presentation.

A source removal action plan was developed by Midwest Gas and the Iowa Department of Natural Resources to address the source coal tar contamination within the underground gas holder basin at Former Manufactured Gas Plant (MGP) sites. The procedure utilizes a mixture of coal, contaminated soil, and coal tar sludge to provide a material that had suitable material handling characteristic for shipment and burning in high efficiency utility boilers. Screening of the mixture was required to remove oversized debris and ferrous metal. The resulting mixture did not exhibit toxic characteristics when tested under the Toxicity Characteristics Leaching Procedure (TCLP). Test results on the coal tar sludges have indicated that the more pure coal tar materials may fail the TCLP test and be classified as a RCRA hazardous waste. The processing procedure was designed to stabilize the coal tar sludges and render those sludges less hazardous and as a result pass the TCLP test. This procedure was adopted by the Edison Electric Institute to develop a national guidance document for remediation of MGP sites. EPA Office of Solid Waste and Emergency Response recommended this strategy to the Regional Waste Management Directors as a practical tool for handling wastes that may exhibit the RCRA characteristics.

Keyword(s): stabilization, coal tar, RCRA, TCLP.

Oral presentation in technology transfer track.

PAHs are a class of widespread pollutants, some of which have been shown to be genotoxic, hence the fate of these compounds in the environment is of considerable interest. Research on the biodegradation of 4 and 5 ring PAHs has been limited by the general lack of microbial isolates or consortia which can completely degrade these toxicants. Heitkamp and Cerniglia have described an oxidative soil Mycobacterium- strain PYR-1 that metabolizes pyrene and fluoranthene more rapidly than the 2 and 3 ring naphthalene and phenanthrene; although some metabolites of benzo-(a)-pyrene (BaP)were detected, no mineralization of BaP was observed. In 1991 Grosser et al. reported the isolation of a Mycobacterium sp. which mineralizes pyrene and also causing some mineralization of BaP. Our study describes a comparative analysis of these two strains, which show very similar colony morphology, growth rate and yellow-orange pigmentation. Genetic differences were shown by DNA amplification fingerprinting (DAF) using two arbitrary GC-rich octanucleotide primers, and by sequence comparison of PCR amplified 16S rDNA, although both strains show similarity closest to that of the genus Mycobacteria. These 16S rDNA sequences are in use for the construction of strain-specific DNA probes to monitor the presence, survival and growth of these isolates in PAH-contaminated soils in studies of biodegradation.

Keyword(s): polycyclic aromatic hydrcarbons, mycobacteria, pollution.

Poster presentation.

Supported by NIEHS Grant ES04908.

Ions derived from tributyl phosphate (TBP) are observed in the static secondary ion mass spectrum of minerals exposed to TBP; these ions are very dependent on the nature of the mineral surface. When TBP is adsorbed onto a reducing site, specifically Fe(ll), the compound will be reduced upon SIMS bombardment, and ions corresponding to tributyl phosphite will be observed. This observation can be made for TBP that is adsorbed to basalt samples having substantial reducing phases, and FeO. The tributyl phosphite that is formed from the reduction of TBP concurrently undergoes a hydride abstraction during the SIMS process, and proceeds to eliminate one and/or two C4H8 and/or one H20 molecules to form ions at m/z 193+, 137+, and 119+. These same ions can be observed in the SIM spectrum of tributyl phosphite adsorbed onto the same mineral surfaces, although ions corresponding to the protonation of tributyl phosphite are also observed. The m/z 193+ and 137+ ions are also observed in the methane chemical ionization (CI) mass spectrum of tributyl phosphite, which demonstrates that hydride abstraction is also occurring in the gas-phase (although this is a minor ion series in the CI mass spectrum).

When TBP is adsorbed onto surfaces that are not reducing, then protonation or hydride abstraction occur. Ions resulting from protonation derive from the sequential elimination of up to three C4H8 molecules (m/z 211+, 155+, 99+) from [M + H]+, and are observed from "oxidized" basalt samples. These ions are also observed from Fe2O3 although in this case substantial hydride abstraction is also observed. This latter ionization mode is followed by the elimination of one and/or two C4H8 molecules to produce ions at m/z 209+ and 153+. Both ion series (protonation and hydride abstraction) can be observed in the CI mass spectrum of TBP. Significantly, none of the ions attributed to tributyl phosphite are observed in the CI mass spectrum of TBP, which supports the idea that their formation is the result of a surface process, and not the result of gas-phase ion chemistry.

A significant ion is observed at m/z 99+ in the SIM spectrum of tributyl phosphite on oxidized surfaces: Fe2O3 and basalt This ion is interpreted in terms of tributyl phosphite being oxidized during the SIMS analysis.

Keyword(s): mass spectrometry, surface analysis, reduction.

Oral presentation in research track.

Degradation of many hazardous compounds in the soil environment can be affected by the different components of the soil matrix as well as the degrading microbial population present. Fulvic acids were extracted from various soils (both impacted and non-impacted) and then used to determine their effect on pyrene mineralization by an isolated pyrene-degrading Mycobacterium sp. A comparison of non-impacted to impacted soil fulvic acids was done to determine whether these fulvic acids have different binding affinities for the pyrene. To determine the effects of fulvic acid addition on mineralization, samples were prepared using sterile sand and different concentrations of fulvic acids (1, 4 and 10%) lyophilized onto the sand. Slurries were made using sterile water and added Mycobacterium cells. Serum bottle radiorespirometry was used to measure mineralization of added 14C-pyrene over a 32 day period. Results show that the addition of fulvic acid up to 5% had little overall effect on pyrene extent of mineralization by the bacteria, but the 5% fulvic acid addition resulted in a lag before mineralization began. The 10% fulvic acid addition decreased mineralization with an extended lag period. Because the addition of fulvic acids to the slurries decreases the pH, survival studies were conducted at unadjusted pH and at pH adjusted to 7, and with varying fulvic acid concentrations up to 2.5%. Activity of the Mycobacterium cells was measured as 14C-acetate incorporation into lipids and indicates that the activity in both unadjusted and pH 7 slurries was similar with up to 1% fulvic acid added. Fulvic acid addition of 2.5% resulted in six times greater activity in pH 7 slurry than in the unadjusted slurry. The decreasing mineralization of pyrene with increasing levels of fulvic acid addition appears to be due to toxicity to the microbes and possible sorption of the compound making it less bioavailable.

Keyword(s): Mycobacterium, mineralization, fulvic acid, sorption, bioavailability.

Poster presentation.

Ion exchange, surface adsorption/desorption, complexation by organic materials, and precipitation/dissolution of discreet solid phases are typical mechanisms that control heavy metals in solution. Understanding the mechanism that is responsible for a given metal is critical to prediction of leaching behavior. Plants can affect mobility of heavy metals by releasing organic compounds into the rhizosphere. Some of the organics released by plant roots (and microorganisms) are strong complexing agents for metals and can potentially increase metal mobility. Sorption and desorption reactions (kinetics and isotherms) of a variety of heavy metals will be determined for diffusion controlled and ion exchange reactions. Organic compounds that could impact metal transport, mine tailings, and soil will be equilibrated for approximately 18 hours in batch studies. The solution phase will be separated and concentrations of target metals measured. This research will quantify heavy metal adsorption/desorption characteristics of soil influenced by plant roots.

Keyword(s): heavy metals, rhizosphere, leaching, adsorption.

Poster presentation.

We are investigating the abiotic reductive dechlorination of carbon tetrachloride using elemental iron as an electron donor. Equation 1 shows the thermodynamic favorability of the reduction of carbon tetrachloride with the oxidation of iron metal at neutral pH.

Fe0 + CCl4 + H+ ® Fe2+ + CHCl3 + Cl- Eo’ = +0.99 Volts (1) Reduction of mono-, di-, and trichloromethane is also thermodynamically favorable to a lesser degree. Our work has provided preliminary feasibility data for the development of novel and inexpensive remediation techniques for carbon tetrachloride in groundwater, including an in-situ process, which may be applicable to other halogenated priority pollutants. Batch experiments were conducted in aqueous solution to determine stoichiometric and pseudo first order reaction rate coefficients for the sequential reduction of carbon tetrachloride to chloroform, methylene chloride, chloromethane and methane using powdered iron metal as the sole reductant. Aerobic reduction rates were slower than anaerobic rates, presumably due to dissolved oxygen from the ambient atmosphere competing with carbon tetrachloride as the terminal electron acceptor. Reduction rates were accelerated at higher temperatures in agreement with the Ahrennius equation. Soil column experiments which simulated reductive dechlorination of carbon tetrachloride in subsurface environments were conducted under anaerobic conditions. These experiments showed the beneficial effect of treatment with iron powder. Potential field applications include in-situ chlorinated solvent remediation and containment and treatment of off gasses.

Keyword(s): carbon tetrachloride, in-situ, iron, reductive dechlorination.

Poster presentation.

Recent surveys of mixed wastes in interim storage throughout the 30-site Department of Energy complex indicate that only 12 of those sites account for 98% of such wastes by volume. Current inventories at the Idaho National Engineering Laboratory (INEL) account for 38% of total DOE wastes in interim storage, the largest of any single site. For a large percentage of these waste volumes, as well as the substantial amounts of buried and currently generated wastes, thermal treatment processes have been designated as the technologies of choice.

Current facilities and a number of proposed strategies exist for thermal treatment of wastes of this nature at the INEL. High level radioactive waste is solidified in the Waste Calciner Facility at the Idaho Central Processing plant. Low level solid wastes until recently have been processed at the Waste Experimental Reduction Facility (WERF), a compaction, size reduction, and controlled air incineration facility. WERF is currently undergoing process upgrading and RCRA Part B permitting.

Recent systems studies have defined effective strategies, in the form of thermal process sequences, for treatment of wastes of the complex and heterogeneous nature in the INEL inventory. These recommendations have resulted in the proposal of combinations of treatment, storage and disposal facilities to most effectively fill these needs.

A number of research, development and demonstration projects are also currently active in both the low temperature incineration and high temperature melting regimes, to provide the fundamental scientific understanding necessary to support design, construction and operation of the proposed facilities. These studies address the partitioning of the toxic metals and radionuclides to the treatment process products and strategies for minimizing release of such residuals to the environment.

This presentation reviews the current status of operating facilities, active studies in this area, and proposed strategies for thermal treatment of INEL wastes.

Keyword(s): thermal treatment, incineration, melting, mixed waste, heavy metals.

Oral presentation in technology transfer track.

This study addresses a viable and natural solution to the elimination of volatile organic compounds (VOCs), pollutants, through the bioremediation process. Plants and associated rhizosphere bacteria have the ability for bioremediation of both volatile and non-volatile organic compounds. For volatile compounds, intersystem transfer by transpiration may be a matter for concern when plants interact with such materials. We have monitored, using FT-IR, the potential transfer of toluene from subsurface water in the presence of toluene-adapted alfalfa plants. These experiments show that the plants and/or their associated micro-organisms effectively degrade toluene so that potential intersystem transfer of VOCs by transpiration may be quite manageable with adapted-plants. Presently, we are monitoring l,l,l-trichloroethane (TCA) and trichloroethylene (TCE) from subsurface water and gas phase above plants. TCA does not show an indication of degradation whereas TCE does. Methane is produced in the groundwater but not transferred to the atmosphere, indicating the presence of a consortium of methanogens and methanotrophs in this soil. The TCE presumably is the substrate for methane production based on chloride ion accumulation. The majority of TCE must be degraded aerobically to yield CO2 in the vadose zone. The FT-IR spectrometer can quickly determine and analyze contaminants in the gas phase, groundwater and plant tissue successfully.

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

Oral presentation in research track.

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 groundwater 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, only a few chelates, familiar ones such as EDTA and NTA, have been tried for this application, and the choice of chelates for decontamination purpose appears to be haphazard. There exists a need to assess the full potential of this technology in removing and/or recovering heavy metals from contaminated media, e.g., soils and mine tailings ponds. This paper will: present a methodology to examine a large number of chelates and to identify those chelates suitable for the selective removal or recovery of various heavy metals. Chemical equilibrium modeling has been used to examine over 100 chelates for their extraction potential; present the experimental results of heavy metal extraction from soil using a few selected chelates. The extraction of metals including cadmium, copper, lead and zinc has been studied under different pH, soil suspension, total chelate concentration, total carbonate concentration, and age conditions; demonstrate that, through a proper choice of chelate, the extraction can be made more selective toward heavy metals; demonstrate that, with the chosen chelates, the extracted metals can be readily recovered as solid precipitates and the soluble chelates reclaimed and reused.

Keyword(s): metal, soil, chelate, contamination, remediation.

Poster presentation.

Detoxification of pentachlorophenol- containing wood preserving waste was monitored under ambient, enhanced and chemical pretreatment conditions for genotoxicity and parent compound removal. Samples were collected throughout the treatment periods and sequentially extracted with dichloromethane and methanol with the Tecator Soxtec apparatus. The organic extracts were analyzed on GC/ECD and GC/MS. The extract mutagenic and genotoxic potentials were evaluated with and without metabolic activation with the Salmonella Microsomal and E. coli Prophage Induction assays. The Salmonella mutagenic responses of extracts from Weswood soil amended with wood preserving waste and treated under ambient conditions were 2.0, 34.6 and 2.4 times greater than the solvent control on days 0, 540 and 1,200 respectively. Organic extracts of soil amended with wood preserving waste and treated under enhanced conditions in a solid-phase rotating drum bioreactor had mutagenic potentials of 3.4, 4.9 and 3.5 on days 0, 14 and 30, respectively. Extracts from wood preserving waste sludge treated with potassium polyethylene glycol were shown to have mutagenic potentials of 2.8, 6.1 and 3.8 at 0, 10 and 30 minutes. The results indicate that the initial products of the wood preserving waste detoxification under all treatment conditions appear to have greater genotoxic potentials than the starting material. The results also suggest that a more rapid detoxification occurs under enhanced and chemical pretreatment conditions.

Keyword(s): detoxification, chemical pretreatment, hazardous waste, pentachlorophenol, bioremediation.

Oral presentation in research track.

This research was supported by NIH grant P42 ES04917.

Organic solute mobility may be better understood by simulating field conditions in the greenhouse. Turf/soil columns from a Kentucky bluegrass (Poa pratensis L.) area near Mead, NE, and Ames, IA, were excavated, concrete encased, and transported to a greenhouse. Organic solutes applied at recommended rates included the herbicides 2,4-D, dicamba, mecoprop, and pendimethalin, the insecticides isazofos and chlorpyrifos, and metalaxyl fungicide. Nitrogen (15N urea) was applied at 49 kg ha-1. Potassium bromide was applied at 100 kg ha-1 as a conservative tracer. Two irrigation water regimes (2.5 and 5.0 cm) with drainage suction (500 cm water) were imposed. Daily column and leachate weights were used to determine water balance and schedule irrigations. The distribution of organic solute residues among leachate, verdure, thatch, and soil depth to 50 cm, were determined and related to nitrogen and water tracer movement. Residual analysis pesticide in the turf/soil profile was metalaxyl > chlorpyrifos = pendimethalin > isazofos. The amount of metalaxyl residue was mainly influenced by differences in soil types. The amount of isazofos residue was affected by irrigation level in the Nebraska soil. Chlorpyrifos and pendimethalin residues were similar in both soils and were not affected by irrigation level.

Keyword(s): pesticides, irrigation, chemical properties, soil properties.

Poster presentation.

The objective of this study was to evaluate the efficiencies of the automatic Soxtec and U. S. EPA SW846 Soxhlet soil extraction methods. In phases one and two of the experiment, extractions were performed on silicon dioxide matrices and silt-loam soils spiked with benz(a)pyrene, pentachlorophenol, and naphthalene at three concentration levels. Each test sample contained either an individual chemical or a 1:1:1 mixture of all three chemicals. Phase three consisted of extractions performed on a silt-loam soil spiked with a coal tar complex mixture. Soxtec samples were sequentially extracted with dichloromethane and methanol while Soxhlet samples were extracted with dichloromethane.

Gas chromatographic results obtained from sample extract analysis were used to calculate percent recoveries of the chemicals. The recoveries of benz(a)pyrene and pentachlorophenol in the Soxtec procedure ranged from 55-88% and 49-88%, respectively. For the Soxhlet method, the recoveries ranged from 46- 73% and 52-87%, respectively. Complex mixture recoveries ranged from 50-60% for both procedures. The mutagenic potentials of the solvent extracts were evaluated using Salmonella typhimurium strain TA98 with and without metabolic activation. Assay results indicated a positive correlation between mutagenic response, assay controls, and the chemical concentrations derived from GC analysis. The data indicate that the Soxtec method, which requires 2 hours, is as effective as the traditional 16 hour Soxhlet extraction procedure for recovering organic chemicals from contaminated matrices. The Soxtec method, thus, offered substantial time and cost savings.

Keyword(s): pentachlorophenol, benz(a)pyrene, extraction, bioassay, soil.

Poster presentation.

This research was supported by NIH grant P42 ES04917.

Numerical models of water flow and solute transport have been extensively used in problems in groundwater quantity and quality management. The fundamental processes which govern the flow and transport behavior are fairly well understood, and the models have been adequately validated using both laboratory and field data. Field and laboratory techniques for the determination of parameters needed in these models are generally available. However, the same cannot be said about the models which have been developed to simulate multiphase flow in aquifers. The need to model multiphase flow arises in dealing with contamination problems involving organic chemicals and waste products which are in the form of nonaqueous phase liquids. Existing models use the basic equations, mathematical formulations, and numerical schemes which have been used in reservoir simulators in petroleum engineering applications. The field application of these models as prediction tools for the design of remediation schemes in hazardous waste problems have been limited for a variety of reasons. These models have not been adequately validated in the laboratory or in the field due to the scarcity of data. The models sometimes fail in attempting to simulate flow and entrapment behavior under heterogeneous soil conditions that are commonly encountered in the field. Accurate field calibration and prediction become difficult due to the limitations of the field and laboratory techniques which are used to obtain the model parameters. The assumptions which are made in modeling the mass transfer from the nonaqueous phase to aqueous phase become questionable under some conditions of ganglia formation and macro-scale entrapment. Results from laboratory spill simulations conducted in large soils tanks, soil columns, soil cells and field investigations, and model analysis are used to discuss some of these limitations. Conclusions on possible improvements to models and issues related to laboratory and field characterization are presented.

Keyword(s): remediation design, multiphase flow, numerical models, groundwater models.

Oral presentation in research track.

An understanding of degradation rates of organic chemicals under transport conditions is critical for enhancing biodegradation rates in-situ. Currently, most solute transport models assume first-order degradation kinetics, and users generally rely on rate constants determined under batch conditions. However, the rates of solute diffusion and sorption-desorption reactions, which influence contaminant bioavailability, are dependent on pore water velocities. Consequently, batch degradation rates are probably not adequate for describing actual degradation rates occurring during transport. To test this hypothesis, we conducted transport experiments using l4C-labeled 2,4-D in disturbed soil columns at three different pore water velocities under unsaturated flow conditions. The amount of 2,4-D in effluent fractions was determined using scintillation analysis, and plotted as a function of pore volume (i.e. 2,4-D breakthrough curves, BTCs). The percent of applied 2,4-D degraded during transport was directly related to the residence time of 2,4-D in the column. For example, higher pore water velocities corresponding to lower residence times resulted in lower total amounts of 2,4-D degraded. These results can generally be predicted using the convection-dispersion equation for solute transport with a first-order model for 2,4-D degradation using batch-determined degradation rate constants. However, batch-determined degradation rates significantly underpredicted the amount of 2,4-D degraded during transport conditions. Optimized rate constants determined for the transport experiments were greater than batch-determined degradation rate constants, and increased with increasing pore water velocity. It is hypothesized that higher pore water velocities yield greater contaminant diffusion rates through interstitial pores and increase contaminant desorption rates, both resulting in enhanced bioavailability.

Keyword(s): biodegradation, transport, 2,4-D.

Poster presentation.

Research was undertaken to assist the Bureau of Land Management and Forest Service in determining the best rehabilitation techniques for mine waste streamside deposits in the Elkhorn Mountains of Montana. These wastes have a high sulfur content, a low pH, and are contaminated with elevated levels of arsenic, lead and other trace metals.

Utilizing a randomized block experimental design, these mine wastes were amended with calcium carbonate, calcium hydroxide, manure and fertilizer. Three grass species, Agrostis alba, Deschampsia caespitosa and Elymus cinereus, were grown under greenhouse conditions to determine their performance.

Keyword(s): revegetation, trace metals, acid mine waste.

Oral presentation in research track.

The oxidation of sulfide minerals in mine waste is a widespread source of resource degradation, often resulting in the generation of acidic water and mobilization of heavy metals. The quantity of acid-forming minerals present in mine waste, dominantly as pyrite (FeS2) is routinely determined by acid-base account (ABA) analytical methods. The acid-base account method specifies the use of extraction techniques to determine the total quantity of acid-forming sulfur compounds in a sample relative to the neutralizing potential. However, when common sulfide and sulfate minerals were subjected to ABA extraction methods, the ABA method failed to accurately distinguish the acid-forming from nonacid- forming minerals, resulting in errors in the determination of potential acidity. These analytical errors are subsequently reflected in inaccurate liming of acid producing waste materials resulting in either excessive cost when potential acidity is overestimated, or potential reclamation failure when potential acidity is underestimated.

Keyword(s): acid-base account, heavy metals, pyrite oxidation, acid mine drainage.

Oral presentation in research track.

In-situ soil vapor extraction, commonly known as soil gas venting, has become an effective remediation technique to remove volatile organic contaminants from the subsurface. The major drawback of this scheme is that the efficiency tends to decrease with the presence of less-volatile organics. Since fluid properties are highly sensitive to ambient subsurface temperature, it is potentially feasible to perform vapor extraction under induced thermal gradients, also called thermal venting, to enhance the recovery of less- volatile fraction of the contaminant mass. The objective of this work is to demonstrate the applicability of the thermal venting technique to enhance the recovery of organics from the liquid unsaturated zone.

To investigate the applicability of the thermal venting scheme, a multicomponent, non- isothermal theoretical model was developed to predict the coupled gas flow, heat transport and mass transport in the unsaturated zone. Heat input to the system was through the incoming gas flow. As the inlet heated air passes through the contaminated zone, enhanced volatilization of liquid contaminant occurs at the air-liquid interface. Heat energy transport was considered under thermodynamic equilibrium condition between different fluid phases. Also the latent heat transfer due to moisture condensation and evaporation of the organic phase was considered. Mass transport analysis used local phase equilibrium approximation to partition component mass between the air, oil, water and adsorbed phases within the residual oil plume. Phase partitioning between the aqueous, air and solid phases were considered outside the organic plume. A number of hypothetical simulations were performed to demonstrate the applicability of the proposed technique. The results were used to demonstrate the propagation of heat through the soil due to the effects of conductive and convective heat fluxes, the latent heat absorbed during contaminant volatilization, and the latent heat released during condensation of water vapor of the incoming air. The results also showed the rate of mass recovery and oil saturation in the contaminated zone during venting. The results of the model will also demonstrate the effectiveness of various forms of heat energy input, energy balance within the system, and the efficiency of the technique with different organic compounds.

Keyword(s): thermal venting, vapor extraction, less-volatile, remediation, hydrocarbons.

Oral presentation in research track.

Reduced radicals of highly oxidized and electron deficient halocarbons (carbon tetrachloride, chloroform, dichloromethane, trichloroethylene, 1,1,1-trichloroethane) were detected by electron paramagnetic resonance spin trapping spectroscopy in a reductive reaction system consisting of lignin peroxidase, hydrogen peroxide, veratryl alcohol, ethylenediaminetetraacetic acid or oxalate, hydrogen peroxide, phenyl-N-t-butylnitrone (as the spin trap) and 1% of the halocarbon. This is a free radical mediated process which uses the organic acid as the electron donor. To correlate the involvement of this mechanism in vivo, mineralization of trichloroethylene and carbon tetrachloride was studied by ligninolytic cultures of Phanerochaete chrysosporium. Both trichloroethylene (20.3% of 10 parts per million) and carbon tetrachloride (18.8% of 10 parts per million) were mineralized by the fungus over a period of 9 days. Mineralization of these chemicals did not take place in formaldehyde- killed control cultures or nonligninolytic cultures of the fungus, indicating that lignin peroxidases play an important role in the process. Since all the components of the reductive system are excreted entracellularly, we propose that this fungus can be used for bioremediation of these halocarbons.

Keyword(s): Phanerochaete chrysosporium, white rot fungi, aliphatic halocarbons, trichloroethylene.

Oral presentation in research track.

Polycyclic aromatic hydrocarbons (PAHs) are a class of potentially hazardous chemicals that exhibit toxic, mutagenic or carcinogenic properties. Microbial degradation is the major route through which PAHs are removed from contaminated environments although other mechanisms such as volatilization, leaching and photodegradation may also be effective. The rhizosphere contains a diversity of microorganisms that contribute to plant health and soil homeostasis. Recent studies indicate that microorganisms in the rhizosphere can degrade toxicants of concern to human health and the environment. The increased density and diversity of rhizosphere microflora may be an important factor for enhanced microbial degradation of PAHs.

The objective of this study is to evaluate degradation of a number of different PAHs in rhizosphere and non-rhizosphere soil. It has been shown that the biodegradation rates of PAHs increase as the number of PAH rings decrease, but there is little information about the biodegradation in rhizosphere soil. This study will provide results from a microcosm experiment designed to evaluate degradation of PAHs in rhizosphere and non-rhizosphere. Also, kinetic models will be developed to represent data collected.

Keyword(s): polycyclic aromatic hydrocarbons, rhizosphere, biodegradation.

Poster presentation.

Methane is the main component of natural gas and has been connected with global warming. The oxidative coupling of methane has been studied to enhance the C2 hydrocarbons selectivity and to reduce the formation of carbon oxides. The acid sites of supported catalysts play an important role in the formation of carbon oxides. The supported Zn-Oxide catalyst with a-Al203 shows no acidity in temperature programmed desorption by using NH3 and exhibits good C2 hydrocarbons selectivity. The optimum loading of Zn-Oxide on a-Al203 is 60wt%. The specific surface area of the catalyst appears not to influence activity. Using alkali metal salts as a promoter in the Zn- Oxide (60wt%)/a-Al203 catalyst, the activity performance for C2 hydrocarbons is LiCl>NaCl>KCl, and that performance is well correlated with the apparent molal enthalpy of formation in alkali halides. The activity performance for reducing carbon oxides is LiCl>KCl>NaCl, which is well correlated with the melting point in alkali halides.

Keyword(s): methane, oxidative coupling, C2 hydrocarbons, carbon oxides, promoter.

Poster presentation.

Conventionally prepared and autoclave prepared calcium oxides were studied to understand the decomposition of the carbon tetrachloride and trichloroethylene processes. To explain the increased ability of autoclave prepared calcium oxide for decomposition of chlorocarbons, different methods were employed. The infra-red technique for observing adsorbed species on calcium oxide after adsorbing carbon tetrachloride and spring balance studies to understand the importance of the basic and acidic sites on the oxide were done. To enlighten some other differences between these two oxides, transmission electron microscopy, thermogravimeric analysis, and instrumental analysis were used.

Keyword(s): chlorocarbon, calcium oxide, decomposition.

Oral presentation in research track.

Eleven polyelectrolytes were tried separately to treat the wastewater from a paint manufacturing industry. Amongst these, Zetag 66, a cationic polyelectrolyte was found to be most effective. A dosage of 5 mg/L of this polyelectrolyte was found to be adequate to achieve 65% COD removal, 97% suspended solids removal and 90% heavy metals removal. The use of this polyelectrolyte assumes significant importance as it eliminates the use of alum completely. This elimination of alum consumption results in considerable reduction of effluent treatment plant sludge which is a hazardous waste. The savings that results in the primary treatment is an added advantage.

Keyword(s): polyelectrolyte, heavy metals, alum consumption, hazardous waste.

Oral presentation in research track.

A near-infrared spectrophotometer has been interfaced with a high-pressure apparatus, utilizing a fiber optic probe. The system was designed to re-circulate carbon dioxide for studies of supercritical extraction. Near-infrared spectra, over the range of 400 to 2400 nm, have been obtained for dense carbon dioxide, at pressures to 8 MPa. Spectra for chlorinated biphenyls in supercritical carbon dioxide have been recorded also. Data is stored directly; a software package correlates solubility in dense carbon dioxide for long-term information management. New opportunities for non-invasive sampling in high- pressure environments are being explored. Solubilities in dense carbon dioxide are modeled utilizing the fugacity coefficient approach with appropriate equations of state.

Keyword(s): supercritical, sampling, solubility, extraction, fugacity.

Oral presentation in research track.

This study investigated the feasibility of using iron rich mine tailings in a metals removal process for leachate based on the natural iron cycle. The natural iron cycle involves the photoreductive dissolution of iron(III) (hydr)oxides resulting in soluble iron(II) during the day, and subsequent oxidation and reprecipitation to iron(III) during the night. Photolysis experiments conducted in the laboratory using mine tailings produced significant concentrations of soluble iron(II) in aqueous solution at low pH. Oxidation of soluble iron(II) to iron(III) removed soluble arsenic and cadmium from solution to concentrations less toxic, with the solid phase precipitate more concentrated for a possible metals recovery system. Factors influencing the photoproduction of iron(II) from the mine tailings included the concentration of organic matter, the presence of amorphous iron oxides, and the chemical forms of iron in the mine tailings. Solution pH and the addition of ligands also affected iron(II) photoproduction. Factors influencing the removal of arsenic and cadmium from aqueous solution included the pH of the solution, as well as the presence of organic matter and amorphous iron oxides in the mine tailings.

Keyword(s): iron, photoreduction, oxidation, adsorption, coprecipitation.

Oral presentation in research track.

Throughout the United States, petroleum hydrocarbon contamination of soil is a severe problem. Storage tanks are quite often the source, whereby hydrocarbons are released on or near the ground surface and are free to migrate through the soil to the groundwater. Sometimes, such chemicals accumulate at interface of different soil types.

Hexadecane transport and degradation in soil reactors were studied in a series of experiments. Three reactors, consisting of soil in sand-clay- sand layers, were contaminated at single points in the center of the top sand layer just below the surface. One reactor was used as a control while the other two were equipped with influent and effluent water ports located above the sand/clay interface. The ports were utilized to add water to the soil. One reactor was supplied with water only and the other was injected with a phosphorus/nitrogen solution to enhance degradation.

The project focused on two aspects: (1) the transport of the NAPLs at an abrupt sand/clay interface and (2) the ability of the soil microbes to degrade the hexadecane under aerobic conditions. Gas chromatography analysis of the effluent water samples indicate no significant removal of the NAPL from the soil by pumping, while mass balances indicate NAPL degradation due to microbial action. In addition, gas chromatography data of soil samples trace the movement of the chemical throughout the three reactors.

Keyword(s): NAPLs, bioremediation, soil interface, transport.

Oral presentation in research track.

The objective of this research is to investigate the impact of vegetation on the fate of toxic and recalcitrant pyrene in soil as well as the influence of different plant species (alfalfa (Meticago sativa) and fescue (Festuca arundinacea)). 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 highly controlled plant growth chambers during a 6-month experiment. The influence of plant species on the fate of pyrene will be estimated by comparing the dissipation rate of the 14C-target compound between alfalfa and fescue. These data will be analyzed to ascertain if there are differences between vegetated and non-vegetated soils, also between plant species with regard to leaching, degradation, plant uptake, mineralization of the 14C-labelled pyrene. The beneficial effects of vegetation planted in soil contaminated by pyrene is anticipated.

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

Poster presentation.

Low concentrations of toxic heavy metals generally encountered in wastewater treatment exclude, for economical reasons, the use of traditional removal methods such as chemical precipitation, ion exchange, filtration, membrane technology, etc. The economical feasibility of recovering heavy metals can be extended by using relatively inexpensive yet efficient natural biopolymers.

Pursuant to our goal of using these biopolymers in decontaminating natural waters, we have measured thermodynamic and kinetic parameters for combinations of metals over a series of temperatures. Copper, lead and zinc divalent metal ions were investigated, as were three different types of calcium alginate biopolymer gel beads. Water-jacketed batch reactors were used in these studies.

Keyword(s): heavy metals, toxic waste, biopolymers, water.

Oral presentation in research track.

Past production practices at munitions ordnance plants have resulted in contamination of terrestrial and aquatic ecosystems. Efforts to date have documented the nature of contamination and attempted to estimate potential migration routes. To predict the fate of munitions in contaminated soils, an accurate prediction of the adsorption- desorption process is critical. Soils from drainage ditches at the abandoned Nebraska Ordnance Plant were found to be highly contaminated with TNT. Equilibrium soil solution concentrations were approximately 70 mg L-1 and relatively independent of soil to solution ratios, indicating the presence of solid phase TNT. Transport experiments were conducted using solute pulses of 70 mg TNT L-1 with uncontaminated soil and with soil columns containing contaminated and uncontaminated layers. Experiments were performed by displacing 27 or 53 pore volumes of TNT-3H20 pulse through disturbed soil columns (5.1 cm diam, 7.5 cm length) at a pore water velocity of 11 cm d-1. Results using uncontaminated soils indicated that breakthrough curves of TNT effluent concentrations never reached initial solute pulse concentrations (C/Co » 0.8) . The equilibrium adsorption isotherm for TNT sorption on the uncontaminated soil was characterized as a nonlinear Freundlich type. Assuming local equilibrium and using a batch- determined distribution coefficient (Kd) in the convection-dispersion equation resulted in an over estimation of elution times. These results indicate that errors can result by assuming a linear adsorption isotherm when predicting TNT transport in highly contaminated soils.

Keyword(s): TNT, fate, transport.

Poster presentation.

A sticking coefficient (a) is defined as a ratio of the rate particles stick to a surface to the rate they strike a surface. A relatively non-attaching bacterium (~ 1 µm) may undergo 350 collisions while only being transported 10 m in soils (0.5 mm diameter). Bacteria do not instantaneously and completely desorb from surfaces producing two major effects. First, sticking coefficients measured from breakthrough concentrations in continuous injection tests can be overestimated since the slowly desorbing cells are incorrectly included in the "steady state" breakthrough concentration. Second, varying times to desorption and large numbers of collisions enhance longitudinal dispersion. We developed a computer program to model desorption rate as a function of time by tracking the desorption of bacteria striking soil surfaces. Model results were compared to bacterial injection experiments conducted in soil columns. We found slow desorption resulted in two factors commonly observed in bacterial breakthrough curves: a slow rise to steady state, and continuous elution of cells at 2-log concentration reductions after a pulse injection.

< b>Keyword(s): biocolloids, filtration, groundwater, particles, subsurface.

Oral presentation in research track.

Polycyclic aromatic hydrocarbons (PAH) are a hazardous group of compounds which are highly toxic, recalcitrant and persistent, and belong to the class of hazardous organic compounds. Petroleum refining, coal conversion and chemical manufacturing sites are most often contaminated with PAHs. The propensity for bioaccumulation and possible adverse health effects of PAH parent compounds as well as intermediates pose special problems in designing a soil treatment system that will effectively reduce the concentration of these compounds. Once incorporated into the soil, biodegradation seems to be the most significant means of PAH decomposition.

The role of vegetation to stimulate the degradation and detoxification of toxic and recalcitrant organic chemicals at low soil concentrations is brought about by several mechanisms of plant-soil interactions, including improvement of physical and chemical properties of contaminated soils, increase in soil microbial activity and increase in contact between microbes associated with the roots and toxic compounds in a contaminated soil. This represents a potential cost effective and low maintenance alternative for waste management. However, there is not enough information concerning specific application of plants, chemicals and soils either in the form of laboratory or field results.

In the research to be presented, different and diverse perennial plant species [grasses (monocot), legumes, and dicots] were collected from the native prairie grasslands and tested for their efficiency in mineralization of the target PAH contaminant—phenanthrene.

The mineralization of phenanthrene was evaluated by the measurement of 14CO2 from the radiolabeled target compound incubated in a rhizosphere soil microcosm. Results from this study will indicate the potential of using different types of plants to enhance degradation of PAHs in contaminated soils.

Keyword(s): bioremediation, phenanthrene, rhizosphere, mineralization.

Poster presentation.

Many acres of soil at the former Nebraska Ordnance Plant (NOP) are contaminated with TNT and other munitions residues. In some areas, solid phase TNT is present and controls the concentration of the soil solution. Native microbial populations in uncontaminated soils similar to those at the NOP site were severely reduced when solid phase TNT was allowed to control the soil solution TNT concentration. However, examination of NOP soil revealed an active population of Pseudomonas sp. A single species that could utilize TNT as a sole C source was isolated from the contaminated soil and tentatively identified as Pseudomonas corrugata through the BIOLOG system. Subsequent growth and characterization experiments indicate that the Pseudomonad metabolizes TNT while in the exponential phase of growth in medium containing glucose as a C source. In addition, a consortium of organisms was found that could utilize TNT as a sole N source. Low TNT mineralization rates (measured by CO2 evolution) in soil and media using the various isolates suggest reduced availability due to sorption and incorporation of transformation intermediates into the organic matrix and microbial biomass. Pretreatment of