Final Report: Rocky Mountain Regional Hazardous Substance Research Center for Remediation of Mine Waste Sites

EPA Grant Number: R829515
Center: HSRC - Rocky Mountain Regional Hazardous Substance Research Center for Remediation of Mine Waste Sites
Center Director: Shackelford, Charles D.
Title: Rocky Mountain Regional Hazardous Substance Research Center for Remediation of Mine Waste Sites
Investigators: Shackelford, Charles D.
Institution: Colorado State University
EPA Project Officer: Lasat, Mitch
Project Period: October 1, 2001 through September 30, 2006
Project Amount: $5,261,000
RFA: Hazardous Substance Research Centers - HSRC (2001) RFA Text |  Recipients Lists
Research Category: Hazardous Waste/Remediation , Land and Waste Management

Objective:

The Rocky Mountain Regional Hazardous Substance Research Center (HSRC) consisted of a consortium of participants from Colorado State University (CSU), Colorado School of Mines (CSM), Montana Tech from the University of Montana (MTUM), and several academic and non-academic participants from other regions of the U.S. and Canada. Although Rocky Mountain Regional HSRC represented EPA Region 8 states (Colorado, Montana, North Dakota, South Dakota, Utah, and Wyoming), the activities of the Rocky Mountain Regional HSRC also pertained to any location within the U. S., particularly where remediation of mine waste was required and/or where there was metals contamination.

The Rocky Mountain Regional HSRC consisted of two primary components: research and outreach. The research goal of the Rocky Mountain Regional HSRC was to develop new and to improve existing methods or technologies for remediation of mine waste sites that are cost effective and lead to clean ups that are protective of human health and the environment. Research was defined with respect to five research focus areas (concentrations) as follows: (1) site characterization and contaminant transport/transformation; (2) surface water and sediment transport; (3) treatment processes; (4) technologies; and (5) ecological and human health toxicity. The goals for each of these research focus areas varied.

The outreach activities of the Rocky Mountain Regional HSRC included technology transfer, technical outreach and service to communities (TOSC), and technical assistance for brownfields (TAB). Technology transfer included such activities as conferences, short courses, workshops, and field demonstrations, with a specific emphasis on the development of new technologies. The TOSC and TAB programs provided educational information to allow communities to make informed decisions concerning environmental contamination, and provided technical assistance to communities and other stakeholders including the redeveloping of brownfields sites. Unlike the research component of the Rocky Mountain Regional HSRC, outreach activities were not necessarily restricted to mine waste sites.

Summary/Accomplishments (Outputs/Outcomes):

A total of 11 research projects were funded as part of the Rocky Mountain Regional HSRC. The typical project duration was 2 years, with one project funded for 3 years and another project funded for only 1 year. Three projects were funded in each of three research focus areas, viz., treatment processes, technologies, and ecological and human health toxicity. One project was funded in each of the other two focus areas, viz., site characterization and contaminant transport/transformation, and surface water and sediment transport. Summaries of the findings with respect to each focus area follow.

Site Characterization and Contaminant Transport/Transformation. The primary goal of this research focus area was to improve our understanding of the role of chemical transformations in controlling the mobility of contaminants as related to the availability of the metals to ultimately affect human health and the environment. With respect to this goal, the mobility of arsenic (As), a common contaminant of concern at mine waste sites, in natural environments is a significant concern. In general, As mobility is controlled primarily by sorption onto metal oxide surfaces, and the extent of this sorption may be influenced strongly by the presence of other dissolved substances, specifically natural organic matter (NOM), that interact with surfaces or with arsenic itself. Thus, a study was undertaken to evaluate the fundamental influence of NOM on the mobility and fate of As in natural environments.

The objectives of the study were to evaluate the influences of samples of diverse natural NOM on the sorption of As onto hematite, a model metal oxide, as well as to reveal influences of arsenic on the sorption of NOM, using conditions and concentrations relevant to natural freshwater environments. Four of six NOM samples tested formed aqueous complexes with arsenate and arsenite. The extent of complexation varied with the NOM origin and, in particular, increased with the cationic metal (primarily Fe) content of the NOM sample. In addition, every NOM sample showed active redox behavior toward arsenic species, indicating that NOM may greatly influence redox as well as complexation speciation of arsenic in freshwater environments. When NOM and As were incubated together with hematite, NOM dramatically delayed the attainment of sorption equilibrium and diminished the extent of sorption of both arsenate and arsenite. Consistent with this result, when NOM and As were introduced sequentially, all NOM samples displaced sorbed arsenate and arsenite from hematite surfaces, and arsenic species similarly displaced sorbed NOM from hematite in significant quantities. Based on the results of the study, competition between NOM and As for sorption appears to be a potentially important process in natural waters, suggesting that NOM may play a greater role in arsenic mobility than previously recognized. In addition, in all sorption experiments, arsenite was consistently desorbed or prevented from sorbing to a greater extent than arsenate, indicating that interactions with NOM also may explain partially the generally greater mobility of arsenite in natural environments.

Surface Water and Sediment Transport. The primary goal for research in this focus area pertained to establishing impacts for metals, acidity, and any other parameters of concern that relate to the attainment of acceptable water quality in mine-impacted watersheds, with the aim of developing watershed-specific water quality management plans for the purpose of implementing waste load allocations from point sources typical of Superfund sites. In response to this goal, a research project focused on simulating with a spatially distributed watershed model the transport and toxicity of metals at the California Gulch, Colorado mine-impacted watershed. Using a database of observations for the period 1984-2004, hydrology, sediment transport, and metals transport were simulated for a June 2003 calibration event and a September 2003 validation event. Simulated flow volumes were within approximately 10% of observed conditions. Observed ranges of total suspended solids, cadmium, copper, and zinc concentrations were also successfully simulated. The model then was used to simulate the potential impacts of a 1-in-100-year rainfall event. Driven by large flows and corresponding soil and sediment erosion for the 1-in-100-year event, estimated solids and metals export from the watershed was 10,000 metric tons for solids, 215 kg for Cu, 520 kg for Cu, and 15,300 kg for Zn. As expressed by the cumulative criterion unit (CCU) index, metals concentrations far exceeded toxic effects thresholds, suggesting a high probability of toxic effects downstream of the gulch. More detailed Zn source analyses indicated that much of the Zn exported from the gulch originated from slag piles adjacent to the lower gulch floodplain and an old mining site located near the head of the lower gulch. With respect to managing site remediation, the results suggested that there is a significant risk of lower gulch floodplain recontamination due to the potential for transport from upstream areas over time. More importantly, even though 2000 waste piles are scattered across the site, the results indicate that much of the Zn entering the lower gulch floodplain originates from two main areas: slag piles adjacent to the lower gulch floodplain and an old mining site located near the head of the lower gulch. Since the physical setting of California Gulch is similar to other high mountain mine waste sites in the region, the results of these simulations can be generalized. Large, infrequent rainfall events can export substantial metals masses over short timeframes, but also redistribute mine wastes across the landscape and place even larger metals masses into transient storage in stream networks and adjacent floodplains. Smaller, more frequent events do not mobilize as much material from the land surface but can transport considerable material already within stream networks.

Treatment Processes. The goal of research on treatment processes was to focus on biologically mediated processes that can be used to treat mine waste streams, including acid mine drainage. The three research projects conducted on treatment processes focused on microbial reduction for the removal of metals from passive treatment zones, such as permeable reactive barriers. Two of the studies focused on the application of removal of metals via precipitation with sulfide in the presence of sulfate reducing bacteria (SRB), whereas the other study focused on the ability of fermentative and iron reducing bacteria to reduce uranium.

The objectives related to the studies involving SRB were to determine: (1) the dependence of SRB on changing chemical composition and on succession and competition of SRB with dynamic microbial populations within the microbial community; (2) the influence of decomposing organic solids on sulfate reduction rates for metals precipitation in sulfate reducing systems; and (3) the influence of inoculum on the performance of columns simulating sulfate reducing systems using chemical and biomolecular analyses. In terms of the dependence of SRB on changing chemical composition and on succession and competition of SRB with dynamic microbial populations, eight bench-scale columns simulating permeable reactive zones were constructed and monitored to define periods of establishment, performance, and decline, Short-term batch studies also were performed using substrate-supplemented column materials, on Days 0 (pre-establishment), 27 (establishment), 41 (performance), and 99 (decline) to reveal potential activities of cellulolytic bacteria, fermenters and anaerobic respirers, SRB, and methanogens. The columns showed active sulfate reduction, with sulfate removal rates of approximately 1–3 mol/m3/d, as well as effective removal of zinc. Potential activities of fermentative and anaerobic respiratory bacteria were initially high but diminished greatly during establishment and dropped further during performance and decline. In contrast, potential SRB activity rose during the establishment period, peaked during the performance period, and diminished as performance declined. Potential methanogen activity was low, and SRB methanogen substrate competition was shown not to limit SRB activity. Cellulolytic bacteria showed no substrate limitation at any time. However, fermenters experienced substrate limitation by Day 0, SRB by Day 27, and methanogens by Day 41, showing the dependence of each group on upstream populations to provide substrates. All potential activities, except methanogenesis, were ultimately limited by cellulose hydrolysis and declined substantially by Day 99, showing that long-term substrate deprivation strongly diminished the intrinsic capacity of the microbial community to perform.

In terms of the influence of decomposing organic solids on sulfate reduction rates for metals precipitation, model simulations based on a newly developed algorithm were compared with published experimental data for two single-substrate and two multiple-substrate batch equilibrium experiments. The comparisons were based on the temporal trends in sulfate, ferrous iron, and hydrogen sulfide concentrations, as well as on rates of sulfate reduction. The temporal behaviors of organic solid materials, dissolved organic substrates, and different bacterial populations also were simulated. The simulated results using Contois kinetics for polysaccharide decomposition, Monod kinetics for lactate-based sulfate reduction, instantaneous or kinetically controlled precipitation of ferrous iron mono-sulfide (FeS), and partial volatilization of hydrogen sulfide to the gas phase compared favorably with the experimental data. However, when Contois kinetics of polysaccharide decomposition was replaced by first-order kinetics to simulate one of the single-substrate batch experiments, a comparatively poorer approximation of the rates of sulfate reduction was obtained. The effect of sewage sludge in boosting the short-term rate of sulfate reduction in one of the multiple substrate experiments also is approximated reasonably well. The results illustrated the importance of the type of kinetics used to describe the decomposition of organic solids on metals precipitation in sulfate-reducing systems as well as the potential application of the model as a predictive tool for assisting in the design of similar biochemical systems.

Finally, in terms of the influence of inoculum on the performance of sulfate reducing systems, columns inoculated from two sources, i.e., a bovine dairy manure (DM) and a previous sulfate-reducing column (SRC), as well as uninoculated columns (U) were fed a simulated mine drainage and compared on the basis of pH neutralization and removal of cadmium, zinc, iron, and sulfate. Removal of cadmium, zinc, and sulfate was significantly higher in the SRC columns than in the DM and U columns, with no significant difference between the DM and U columns. Denaturing gradient gel electrophoresis (DGGE) analysis revealed differences in the microbial community composition among columns with different inocula, and indicated that the microbial community in the SRC columns was the first to reach a pseudo-steady state. In the SRC columns, a higher proportion of the DGGE band DNA sequences were related to microorganisms that carry out cellulose degradation, the rate limiting step in the energy flow of sulfate reducing systems, than was the case in the other columns. The proportion of sulfate-reducing bacteria of the genus Desulfobacterium was monitored using real-time quantitative PCR and was observed to be consistently higher in the SRC columns. The results of this study suggest that the inoculum plays an important role in the performance of sulfate reducing systems, and this study represented the first report providing a detailed analysis of the effect of different microbial inocula on the remediation of acid mine drainage.

The goal of the one-year project evaluating the ability of fermentative and iron reducing bacteria to reduce uranium (U) was to provide an initial evaluation and development of an applicable predictive kinetic model for the design of a feasible, low-cost, efficient, robust and passive treatment process for U- and co-contaminants (toxic-metals) impacted ground water from past mining activities in the Rocky Mountain region. The passive treatment process that was investigated has the potential for synergistically reducing uranium, U(VI), using the iron-reducing bacteria Shewanella putrefaciens CN32 and the fermentative bacteria Clostridium sp. The study involved batch reactor experiments that were used to optimize reductive processes and promote synergistic reduction of U by fermentative and iron-reductive microbial processes with efficient utilization of a carbon substrate (electron donor). Experimental systems were also configured to evaluate the effect of ligands (e.g., carbonate and citrate) on bioreduction. The results of the experiments demonstrated that both bacteria were able to rapidly and efficiently reduce U(VI) to U(IV) using simple electron donors (e.g., glucose, lactate or citrate). Results of experimental systems also showed that three processes operated in parallel: (1) sorption of uranyl species onto the cellular biomass; (2) reduction of U(VI) to (UIV) while being retained as a U(IV)-citrate complex; and (3) reductive precipitation through the stimulation of lactate. A key finding was the presence of the U(IV)-citrate complex which soluble and potentially mobile. However, the U(IV)-citrate complex appeared to be stable with respect to uranium re-oxidation. The process of modeling uranium bioreduction led to the analysis of two uranium-containing complexes: 1) 1:1:1 and 1:1:2 U-Fe-citrate complexes; and 2) the formation constant for the soluble U(IV)-citrate species.

Technologies. Research on technologies pertained to two broad categories: (1) treatment technologies, and (2) prevention and control technologies. The research in treatment technologies pertained to the use of in situ treatment systems, whereas research on prevention and control technologies focused on the use of alternative earthen final covers to control the generation of acid mine drainage (AMD) from sulfidic mine tailings and mine waste impoundments. Alternative earthen final covers are earthen covers designed on water-storage principles, and typically are cheaper and more resilient than the standard RCRA covers that employ a low permeability barrier (e.g., compacted clay) and are specified for use in municipal solid waste (MSW) and hazardous waste landfills.

In terms of treatment technologies, two projects were funded. One project involved an stochastic modeling of the influence of heterogeneity in aquifer hydraulic conductivity (K) on contaminant plume patterns and the required thickness and length of permeable reactive barriers (PRBs) used for in situ remediation. The results provided a quantitative means for evaluating the effects of (1) the level of aquifer heterogeneity as reflected by the standard deviation of the logarithm of K; (2) the aquifer correlation structure anisotropy; and (3) the distance from the contaminant source zone to the PRB. In terms of PRB thickness, a probabilistic factor of safety related to uncertainty in influent groundwater seepage velocities at the location of the PRB was quantified. In terms of PRB length, a probabilistic factor of safety related to uncertainty in the length of a PRB required to capture the contaminant plume, defined as the capture length ratio (CLR), was quantified. The mean and standard deviation in the factor of safety with respect to thickness significantly increased with increasing the level of aquifer heterogeneity, and increased less significantly with increasing aquifer correlation structure anisotropy and distance of transport to the PRB. The mean and standard deviation of CLR increased with increasing level of aquifer heterogeneity and distance of transport to the PRB, but decreased slightly with increasing correlation structure anisotropy. The results indicate that significantly thicker and/or longer PRBs relative to those based on the assumption of homogeneous aquifers are likely when the PRB is to be located within heterogeneous aquifers.

The goal of the second project on treatment technologies was to evaluate the technical feasibility of using electrokinetic injection delivery techniques for the remediation of acid mind drainage (AMD). The objectives focused on determining: (1) the transport efficacy of electrokinetic injection for delivery of organic electron donors, (2) the efficacy of unamended electrokinetic injection for removal of metal contaminants as oxides and hydroxides, and (3) the efficacy of electrokinetic injection for delivery of organic electron donors for stabilizing metals in AMD and characterizing the microbial community present in the soil columns. The objectives were accomplished primarily via bench-top electrokinetic studies using columns containing native alluvial material contaminated with elevated levels of arsenic and varying current levels over a period of thirty days. The experiments included both unamended and amended electrokinetic injection. For the unamended experiments, ground water was used as the electrolyte. For the amended experiments, the ground water in the anode compartment was neutralized with the daily addition of sodium hydroxide, and acetic acid was used in the cathode compartment. Soil samples from both unamended and amended soil columns were examined for presence of microbiological activity. Results indicated that an organic acid such as acetate can be uniformly transported under varying soil conditions at low current levels. For unamended electrokinetic injection, overall removal of the contaminant was indicated, although increased levels of arsenic in aqueous and soil samples taken in the region of the anode indicated formation of arsenic precipitates and an increase in the voltage drop in this region, leading to an overall increase in resistance across the column and ultimately to an increase in power requirements. In contrast, the use of acetic acid in the cathode promoted a less alkaline environment at the cathode and across the column, and the use of the pH-controlled anode and the neutralizing effect of the electrically transported acetate ion across the column promoted unhindered removal of arsenic, leading to more consistent removal of arsenic from the soil column. Finally, no viable microbial community was detected in samples from either unamended or amended columns, indicating that microbial activity was not responsible for the remediation of arsenic within the columns. The findings of this study are significant in terms of understanding contaminant species mitigation and transport in waters impacted from mining operations and from naturally occurring sources of arsenic, and in terms of the use of electrokinetic injection of amendments to sub-surfaces with varying hydraulic conductivities for nutrient addition and system neutralization as a viable option for passive remediation of contaminated subsurface environments.

The goal of the research focused on an assessment of the use of alternative earthen final covers was to evaluate the accuracy of five hydrologic models (UNSAT-H, VADOSE/W, Hydrus-2D, and LEACHM) commonly used for the design of cover systems using high quality field data from large-scale test facilities of alternative covers. The specific objectives of the research project were to provide: (1) a baseline assessment and comparison of the algorithms in existing hydrologic models when applied to a variety of meteorological conditions; (2) an unbiased critical assessment of the predictive capabilities of existing hydrologic models for covers using field data from the EPA's Alternative Cover Assessment Program (ACAP); and (3) improvement of the hydrologic model (or models) that have the most promise so that predictions made with the model are accurate. The study focused on comparing water-balance predictions for two alternative covers, a monolithic barrier and a capillary barrier, with the field measured water balance over three- and four-year periods. Water-balance predictions were obtained for both covers using LEACHM, HYDRUS, and UNSAT-H, whereas VADOSE/W was included for the monolithic cover.

For the capillary barrier, all of the codes captured the seasonal variations in water-balance quantities observed in the field. LEACHM and HYDRUS predicted total runoff during the monitoring period with reasonable accuracy, but the timing of predicted and observed runoff events was different. In contrast, UNSAT-H consistently over-predicted runoff. Evapotranspiration was predicted reliably with all three codes when data from the first year were excluded. However, all three codes over-predicted evapotranspiration in late winter and early spring, when snowmelt was occurring and soil-water storage was accumulating in the field. Consequently, soil-water storage generally was under-predicted by all three codes. Predicted percolation was in good agreement with measured percolation, except during the first year. Results of the comparison indicated that cover modelers should scrutinize runoff predictions for reasonableness and carefully account for snow accumulation, snow melt, and evapotranspiration during snow cover.

For the monolithic cover, accuracy of the runoff prediction was found to affect the accuracy of all other water-balance quantities. Runoff was predicted more accurately when precipitation was applied uniformly throughout the day, the surface layer was assigned higher saturated hydraulic conductivity, or when Brooks-Corey functions were used to describe the hydraulic properties of the cover soils. However, no definitive recommendation could be identified that would provide reasonable assurance that runoff mechanisms are properly simulated and runoff predictions are accurate. Evapotranspiration and soil-water storage were predicted reasonably well when runoff was predicted accurately, general mean hydraulic properties were used as input, and the vegetation followed a consistent seasonal transpiration cycle. However, percolation was consistently under predicted even when evapotranspiration and soil-water storage were predicted reliably. Better agreement between measured and predicted percolation was obtained using mean properties for the soil-water characteristic curve and increasing the saturated hydraulic conductivity of the cover soils by a factor between 5 and 10. Evapotranspiration and soil-water storage were predicted poorly at the end of the monitoring period by all of the codes due to a change in the evapotranspiration pattern that was not captured by the models. The inability to capture such changes was identified as a significant weakness in current modeling approaches and, therefore, as a need for future research.

Ecological and Human Health Toxicity. Research focused on assessing possible injurious effects of mine waste contamination on humans and ecosystems. For example, assessment of contaminant impacts on biotic receptors is often complicated by the difficulty of distinguishing the role of habitat characteristics from the adverse effects of contaminants. Thus, one specific area of need for improving such assessments is a better understanding in the use of molecular and biochemical indicators as a way of detecting and establishing the impacts of specific contaminants with respect to specific receptors (fish, plants, humans, etc.).

Three research projects were conducted in this research focus area. The objective of the first project was to evaluate indicators of recovery in a metal polluted stream (the Arkansas River) following remediation and improvements in water quality to (1) assess the influence of dissolved organic carbon (DOC) on metal bioavailability and toxicity, and (2) investigate potential interactions between heavy metals and other anthropogenic stressors. Stream microcosm and field experiments were conducted in the spring 2003 to examine the response of macroinvertebrates to heavy metal contamination on the community and population-level. In contrast to experiments conducted during the summer 2002, results showed no population-level responses. These differences were attributed to seasonal changes in the size distribution of the mayfly Rhithrogena hageni. Stream microcosm experiments established a concentration-response relationship between heavy metals and percent mortality of R. hageni. Based on EC50 values, the metal concentration that reduced abundance by 50 %, mortality of these sensitive species was size-dependent. The results indicate that life-stage is an important factor determining the sensitivity of aquatic macroinvertebrates to heavy metal contaminants, and that population-level endpoints increase the precision of community-based bioassessments. Microcosm experiments also allowed quantification of interactions between UV-B, organics and metals. Aquatic communities collected upstream from California Gulch on the Arkansas River, Colorado, were exposed to varying concentrations of DOC (12 mg/L humic acid), metals (zinc), and UV-B radiation in artificial streams. Results showed that periphyton accumulated more Zn in streams with elevated DOC levels. This implies that, in systems with higher DOC concentrations, herbivores may be exposed to higher Zn than previously expected. Treatments with elevated UV-B levels had a significant increase in drift of sensitive taxa, specifically the metal-sensitive mayfly Epeorus spp. Decreases in total abundance of Epeorus spp. at the end of the experiment could not be explained by drift alone; therefore, Epeorus spp likely had increased mortality associated with the combination of UV-B and Zn exposure.

The goal of a second project in the ecological and human health toxicity focus area was to establish soil metal toxicity thresholds for numerous plant species that are commonly used in reclamation activities in the Rocky Mountains. This information is currently not available and, as a result, ecological risk assessments must rely on toxicity thresholds established for agronomic species. The objective of this study was to provide a better estimate of soil metal toxicity thresholds for four metals and a large number of native plant species (and a few commonly used introduced species). These threshold values will be used by those in the reclamation industry (government regulators and private entities) to more accurately assess risks associated with soil metal contamination, and to better match re-vegetation plant species to site conditions. The research involved a series of greenhouse screening studies where seedlings of reclamation species and common agricultural species were grown in sand culture and exposed to supplemental concentrations of soluble metals. Six measures of toxicity were then determined: the 60-day LC50, 60-day EC50-plant, 60-day EC50-shoot, 60-day EC50-root, PT50-shoot, and the PT50-root. Experiments screening a variety of grasses, forbs and shrubs using zinc, copper, manganese and arsenic were completed. Results from these studies suggest that restoration species generally have higher metal tolerance than agronomic species reported in the past. Thresholds determined by these studies should be more useful for risk assessors than those currently used, which are based largely on agronomic crops. Our research has provided phytotoxicity thresholds for plants commonly used in remediation of hazardous waste sites in the Western U.S. This information should be valuable to ecological risk assessors and restoration ecologists involved in the characterization and restoration of metal-contaminated sites by providing information that is critical for making decisions about the degree of contamination and the extent of restoration required.

The overall goal of the third and final research project in the ecological and human health toxicity focus area was to improve our ability to set water quality criteria for streams that are affected by mining. The research project had four specific objectives: (1) evaluation of the existing Biotic Ligand Model (BLM) for mining impacted waters; (2) improvement of the BLM by examining the influence of the unique nature mining impacted waters on metal toxicity; (3) enhancement of the BLM to include mixed metals (Cu and Zn); and (4) development of a microbial bioassay to rapidly screen mine wastes to assess their toxicity potential. BLM modeling and toxicity testing were preformed using a series of waters collected from Clear Creek, a mining impacted watershed (MIW) located west of Denver. Toxicity experiments used Ceriodaphnia dubia to measure copper and zinc toxicity of the samples. The degree to which the BLM-predicted LC50 matched the measured LC50 was determined. For copper, the experimental results were in good agreement with the BLM prediction and opposite to the hardness-based prediction, indicating the superiority of the BLM approach over the hardness approach. For zinc, similar predictions of LC50 were obtained by the two approaches, suggesting the BLM did not offer a significant improvement relative to the current hardness-based approach. Overall the results for the Clear Creek study suggested that the BLM was accurate for predicting copper and zinc toxicity to Ceriodaphnia dubia in MIW. However, in a series of experiments with simulated waters containing iron and dissolved organic matter (DOM), the BLM occasionally under-predict the LC50 for copper, and the DOM complexation with iron may have inhibited the reduction in the ability of the DOM to complex copper, thus removing some of the protectiveness of the DOM in protecting Ceriodaphnia dubia from copper toxicity. Thus, water quality criteria obtained from BLM calculations should account for iron competition and DOM fractionation. In terms of the effect of metal mixtures including copper, zinc, cadmium, and nickel, the common assumption that the toxicity of each metal is additive was found to be not always correct and both antagonistic effects (toxicity less than predicted by the sum) and synergistic effects (toxicity more than predicted by the sum) were found. Finally, a commercially available bacterial test (MetPlate), which relies on an E. coli strain, was evaluated as a potentially more rapid and procedurally simpler way to evaluate the toxicity of MIW. The test was found to be not as highly affected by water chemistry, as was Ceriodaphnia dubia, and thus may not be as effective as the BLM calculation for predicating metal toxicity in MIW. However, the MetPlate method was very rapid and was easily integrated into as approach for determining the potential toxicity of waste rock piles. Based on the results, the MetPlate approach should provide USEPA with a rapid screening tool for examining metal contaminated sites.

Outreach Activities. In term of outreach activities, the Center personnel participated in a total of 12 TOSC projects and 8 TAB. The 12 TOSC sites included 7 sites in Colorado, 2 sites in Montana, and 1 site each in Michigan, South Dakota, and Utah. The 8 TAB sites included 5 sites in Montana, and 1 site each in Colorado, Missouri, and North Dakota. Thus, all 5 of the 6 states within EPA Region 8 were represented by Center TOSC and TAB activities, as well as 2 states outside the region (Michigan and Missouri).


Journal Articles: 16 Displayed | Download in RIS Format

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Journal Article Bednar AJ, Garbarino JR, Ranville JF, Wildeman TR. Effects of iron on arsenic speciation and redox chemistry in acid mine water. Journal of Geochemical Exploration 2005;85(2):55-62. R829515 (2005)
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  • Journal Article Clark JL, Clements WH. The use of in situ and stream microcosm experiments to assess population- and community-level responses to metals. Environmental Toxicology and Chemistry 2006;25(9):2306-2312. R829515 (2005)
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  • Journal Article Clements WH. Small-scale experiments support causal relationships between metal contamination and macroinvertebrate community responses. Ecological Applications 2004;14(3):954-967. R829515 (2003)
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  • Journal Article Hemsi PS, Shackelford CD, Figueroa LA. Modeling the influence of decomposing organic solids on sulfate reduction rates for iron precipitation. Environmental Science & Technology 2005;39(9):3215-3225. R829515 (2004)
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  • Journal Article Hemsi PS, Shackelford CD. An evaluation of the influence of aquifer heterogeneity on permeable reactive barrier design. Water Resources Research 2006;42(3):W03402, doi:10.1029/2005WR004629. R829515 (2004)
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  • Journal Article Hong H, Pruden A, Reardon KF. Comparison of CE-SSCP and DGGE for monitoring a complex microbial community remediating mine drainage. Journal of Microbiological Methods 2007;69(1):52-64. R829515 (Final)
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  • Journal Article Kashian DR, Prusha BA, Clements WH. Influence of total organic carbon and UV-B radiation on zinc toxicity and bioaccumulation in aquatic communities. Environmental Science & Technology 2004;38(23):6371-6376. R829515 (2004)
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  • Journal Article Logan MV, Reardon KF, Figueroa LA, McLain JET, Ahmann DM. Microbial community activities during establishment, performance, and decline of bench-scale passive treatment systems for mine drainage. Water Research 2005;39(18):4537-4551. R829515 (2004)
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  • Journal Article Paschke MW, Valdecantos A, Redente EF. Manganese toxicity thresholds for restoration grass species. Environmental Pollution 2005;135(2):313-322. R829515 (2004)
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  • Journal Article Paschke MW, Perry LG, Redente EF. Zinc toxicity thresholds for reclamation forb species. Water, Air, & Soil Pollution 2006;170(1-4):317-330. R829515 (Final)
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  • Journal Article Pruden A, Messner N, Pereyra L, Hanson RE, Hiibel SR, Reardon KF. The effect of inoculum on the performance of sulfate-reducing columns treating heavy metal contaminated water. Water Research 2007;41(4):904-914. R829515 (Final)
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  • Journal Article Prusha BA, Clements WH. Landscape attributes, dissolved organic C, and metal bioaccumulation in aquatic macroinvertebrates (Arkansas River Basin, Colorado). Journal of the North American Benthological Society 2004;23(2):327-339. R829515 (2003)
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  • Journal Article Redman AD, Macalady DL, Ahmann D. Natural organic matter affects arsenic speciation and sorption onto hematite. Environmental Science & Technology 2002;36(13):2889-2896. R829515 (2002)
    R829515 (Final)
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  • Journal Article Ritter K, Aiken GR, Ranville JF, Bauer M, Macalady DL. Evidence for the aquatic binding of arsenate by natural organic matter--suspended Fe(III). Environmental Science & Technology 2006;40(17):5380-5387. R829515 (2005)
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  • Journal Article Rojas R, Velleux M, Julien P, Johnson B. Grid scale effects on watershed soil erosion models. Journal of Hydrologic Engineering 2008;13(9):793-802. R829515 (2003)
    R829515 (2004)
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  • Journal Article Velleux ML, Julien PY, Rojas-Sanchez R, Clements WH, England Jr JF. Simulation of metals transport and toxicity at a mine-impacted watershed: California Gulch, Colorado. Environmental Science & Technology 2006;40(22):6996-7004. R829515 (Final)
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  • Supplemental Keywords:

    Abandoned mines, adsorption, acetate, acid, acid drainage, acid mine drainage, acid rock drainage, alternative covers, anaerobic, aquatic environments, aquatic habitat, Arkansas River, arsenic, arsenate, batch testing, bench scale, bioavailability, bioreduction, bioremediation, biotransformation, brownfields, cadmium, capillary barrier, column testing, copper, California Gulch, Contois kinetics, copper, electrokinetic remediation, environmental chemistry, evapotranspiration, evapotranspirative covers, facilitated transport, fate and transport, fermentative bacteria, goethite, ground water, heavy metals, iron reducing bacteria, kinetics, macroinvertebrates, manganese, metal bioaccumulation, metal pollution, metals, microbial analysis, microbial reduction, microcosm experiments, mine drainage, mine leachate, mine waste, mobility, modeling, monocovers, Monod kinetics, monolithic cover, natural organic matter, numerical modeling, passive treatment, permeable reactive barriers, permeable reactive zones, phytotoxicity, reclamation, remediation, restoration, Richards' equation, risk assessment, soil-water characteristic curve, soil-plant covers, sorption, sulfate reducers, sulfate reducing bacteria, Superfund, surface runoff, surface water, toxicity, unsaturated flow, uranium, waste rock, water quality, water balance, water-balance covers, watersheds, watershed modeling, zinc,, RFA, Scientific Discipline, Toxics, Waste, Ecosystem Protection/Environmental Exposure & Risk, Hydrology, National Recommended Water Quality, Bioavailability, Remediation, Contaminant Candidate List, Monitoring/Modeling, Fate & Transport, Hazardous Waste, Environmental Engineering, Geology, Hazardous, fate and transport, risk assessment, contaminated sediments, mathematical model, fate and transport , contaminant transport, lead, acid mine drainage, contaminated sediment, mine tailings, cleanup, sediment transport, modeling, surface water, contaminated soil, total maximum daily loads, manganese, Zinc, Selenium, toxicity, mining, copper, environmental toxicant, risk assessments, cadmium, arsenic, metals, microbial populations, contaminant transport models

    Relevant Websites:

    Rocky Mountain Regional Hazardous Substance Research Center http://www.engr.colostate.edu/ce/HSRC/ Exit

    Progress and Final Reports:

    Original Abstract
  • 2002 Progress Report
  • 2003 Progress Report
  • 2004 Progress Report
  • 2005 Progress Report
  • Subprojects under this Center: (EPA does not fund or establish subprojects; EPA awards and manages the overall grant for this center).
    R829515C001 Redox Transformations, Complexation and Soil/Sediment Interactions of Inorganic Forms of As and Se in Aquatic Environments: Effects of Natural Organic Matter
    R829515C002 Fate and Transport of Metals and Sediment in Surface Water
    R829515C003 Metal Removal Capabilities of Passive Bioreactor Systems: Effects of Organic Matter and Microbial Population Dynamics
    R829515C004 Evaluating Recovery of Stream Ecosystems from Mining Pollution: Integrating Biochemical, Population, Community and Ecosystem Indicators
    R829515C005 Rocky Mountain Regional Hazardous Substance Research Center Training and Technology Transfer Program
    R829515C006 Technical Outreach Services for Communities and Technical Assistance to Brownfields
    R829515C007 Evaluation of Hydrologic Models for Alternative Covers at Mine Waste Sites
    R829515C008 Microbial Reduction of Uranium in Mine Leachate by Fermentative and Iron-Reducing Bacteria
    R829515C009 Development and Characterization of Microbial Inocula for High-Performance Passive Treatment of Acid Mine Drainage
    R829515C010 Reactive Transport Modeling of Metal Removal From Anaerobic Biozones
    R829515C011 Assessment of Electrokinetic Injection of Amendments for Remediation of Acid Mine Drainage
    R829515C012 Metal Toxicity Thresholds for Important Reclamation Plant Species of the Rocky Mountains
    R829515C013 An Improved Method for Establishing Water Quality Criteria for Mining Impacted Streams