Final Report: Processes Controlling the Chemical/Isotopic Speciation and Distribution of Mercury from Contaminated Mine Sites

EPA Grant Number: R827634
Title: Processes Controlling the Chemical/Isotopic Speciation and Distribution of Mercury from Contaminated Mine Sites
Investigators: Brown Jr., Gordon E. , Coolbaugh, Mark , Engle, Mark , Fitzgerald, Brian , Giglini, Anthony , Gustin, Mae Sexauer , Johnson, Stephen B. , Kim, Christopher S. , Lowry, Gregory V. , Nacht, David M. , Rytuba, James J. , Shaw, Samuel , Sladek, Chris , Slowey, Aaron J. , Vette, Alan , Zehner, Richard E.
Institution: Stanford University , United States Geological Survey [USGS]
EPA Project Officer: Hiscock, Michael
Project Period: October 1, 1999 through September 30, 2002
Project Amount: $708,634
RFA: Mercury: Transport and Fate through a Watershed (1999) RFA Text |  Recipients Lists
Research Category: Water and Watersheds , Mercury , Water , Safer Chemicals

Objective:

The original objectives of this research project were to: (1) determine the chemical speciation and relative abundance of different forms of Hg in mine wastes using new synchrotron radiation methods; (2) investigate the role of colloidal transport as a mechanism for dispersal of Hg from waste sites; (3) identify the mode of Hg sorption in downstream sediments and fine-grained precipitates in the presence of common complexing ligands; (4) determine the effects of aqueous complexing ligands on the desorption and sorption inhibition of Hg; (5) measure and correlate Hg emission into the atmosphere with Hg speciation, climate, and geologic factors; and (6) examine Hg isotope fractionation as a potential means of identifying Hg from specific localities and correlate the information on chemical and isotopic speciation of Hg along the various pathways Hg may travel. Substantial progress was made in the first five areas of the project. Less progress than expected was made on Objective 6. This was considered to be exploratory in the original proposal, with some chance for success but with some big unknowns, such as the extent to which different Hg isotopes fractionate during natural and anthropogenic (e.g., calcining or Hg-ores) processes. Results from each of these areas are summarized in our Year 1, Year2, and Year3 annual reports as well as below. During the no-cost extension of this project covering the period October 1, 2002-September 30, 2004, several new projects were undertaken that extended our studies to include two new objectives to: (7) speciate Hg at several new Hg-contaminated sites, including placer mining areas in the Sierra Nevada foothills where liquid Hg was used to recover fine particles of gold; and (8) examine the role of organic acids in Hg transport.

Summary/Accomplishments (Outputs/Outcomes):

Objective 1: Mercury Speciation

We have completed studies of the molecular-level speciation of Hg in Hg-bearing samples from a variety of localities in the California Coast Range Hg mineral belt, the placer gold mining belt in the Sierra Nevada foothills, and Nevada. Different particle size fractions were generated by laboratory column experiments on Hg mine wastes and were characterized by X-ray absorption fine structure (XAFS) spectroscopy, scanning electron microscopy, and analytical transmission electron microscopy (ATEM). As an example of our findings, the colloidal fraction from calcines collected at the Sulphur Bank Mine were found to consist of cinnabar, metacinnabar, and corderoite, the last being a relatively soluble Hg-containing phase. This project was the first to use synchrotron-based XAFS spectroscopy to determine the molecular-level speciation of Hg in many different mining localities in California, and we found significant variations in Hg speciation at different sites. The major implication of these projects concerning human health impact of Hg pollution is that when highly soluble forms of Hg, such as the minerals corderoite, montroydite, schuetteite, egglestonite, and terlinguite, are present at a particular mining site, they potentially are much more bioavailable than highly insoluble forms of Hg, such as cinnabar and metacinnabar. When members of the former suite of minerals are present in mine tailings and sediments, these sites should be remediated. Such remediation would involve the removal or encapsulation of these phases. The results of these studies were published in several journal articles (Kim, et al., 2000, 2003, 2004a).

Objective 2: Colloidal Transport of Mercury

One of the major questions associated with Hg pollution is how mercury gets dispersed from point sources, such as mining sites, to sediments and surface waters, where it can be converted into methyl Hg by sulfate-reducing bacteria and incorporated into the food chain. In our projects, the relevant surface water bodies are drinking water reservoirs in Santa Clara County and San Francisco Bay. We conducted laboratory column experiments designed to examine the transport of Hg by colloids, which are very fine particles (< 1 μm in diameter) capable of being transported by flowing water (both groundwater and surface waters). Starting materials for these experiments were calcines (roasted Hg ores) from the New Idria Hg mine in central California, as well as raw mine wastes from New Idria and other localities, including the Sulphur Bank Mine in Lake County, California, and Clear Creek in Sacramento, California, where placer gold mining was carried out. Samples sequentially were exposed to electrolyte solutions and then to low levels of malonic acid or, in later experiments, to oxalic and citric acids. The use of oxalic and citric acids represents a significant refinement over our previous experiments with relatively high levels of malonic acid, as oxalic and citric acids are very common in nature, and the concentrations utilized were selected to closely mimic the concentrations of organic acids typically found in vegetated environments. The conditions, therefore, represent a simple model for newly revegetated mine tailings environments. Although the time required to generate particles from mine tailings increased markedly with decreasing organic acid concentration, even the lowest organic acid concentrations were found to lead to colloid generation (primarily cinnabar, metacinnabar, and corderoite as confirmed by XAFS spectroscopy and TEM studies) instead of Hg(II) complexes adsorbed on the surfaces of colloidal particle of iron oxide. In contrast, measurements of dissolved Hg in the solutions eluted from the columns showed very low concentrations ( ≤30 ppb beyond the first 10-15 pore volumes for a 1mM organic acid solution), indicating that the vast majority of Hg is transported in the colloidal phase.

The key finding of this project of colloid transport is that most of the Hg-bearing colloids are cinnabar or metacinnabar, which is surprising in light of the widely held belief that most heavy metals attach to colloidal particles, such as iron oxides, as sorption complexes. No evidence for such sorption complexes was found in this project. A paper describing our column experiments, Hg-colloid generation, and detailed characterization of the colloids has been published in the journal Environmental Science & Technology (Lowry, et al., 2004).

Objective 3: Sorption of Mercury on Particle Surfaces

Sorption of Hg(II) onto mineral particles may effectively sequester mercury in mine tailing and aquatic environments if the sorption complexes are strongly bonded to the particle surfaces. We have assessed the types of Hg(II) sorption complexes that form on common mineral particles (goethite, boehmite, and γ-alumina) in Hg-mine waste environments using XAFS spectroscopy. This work showed that Hg(II) dominantly forms innersphere sorption complexes on these common mineral particles. An important result of this project is the finding that Fe - and Al - (hydr)oxides can play a significant role in the uptake of Hg(II) through direct innersphere sorption processes. Within the pH range typical of the natural environment, Hg(II) sorption was found to be relatively constant among the substrates studied. Such sorption reactions could conceivably provide a transport mechanism for mercury. Our column studies of mercury transport (see Section 2 above), however, found little if any evidence for such colloid-facilitated transport. The results of this study are reported in a paper in the Journal of Colloid and Interface Science (Kim, et al., 2004b).

Objective 4: Effects of Complexing Ligands on Hg(II) Sorption and Transport

Sorption of Hg(II) on goethite ( α-FeOOH), boehmite ( γ-AlOOH), and γ-alumina ( γ-Al 2O 3) was examined in the presence of chloride and sulfate ions as a function of pH to determine how these common inorganic ligands interfere with or enhance Hg(II) uptake on these particle surfaces. Such ions are relatively common in natural waters, particularly hot springs, where mercury deposits often form. The reaction products were characterized at the molecular level using XAFS spectroscopy. The presence of Cl- was found to result in reduced Hg(II) sorption, largely through the formation of stable aqueous HgCl2 complexes. The presence of SO42- results in enhanced Hg(II) sorption, largely through the reduction of electrostatic repulsion at positively charged particle surfaces. Ternary surface complexation of Hg(II) was identified in the presence of Cl- and SO42-. The details of this project are reported in a paper in the Journal of Colloid and Interface Science (Kim, et al., 2004c).

Objective 5: Atmospheric Emissions of Mercury

This component of the project focused on assessing parameters that control Hg emissions from mine waste and surrounding Hg-enriched terrains, developing a database of emissions, and scaling up emissions for select sites. Other important tasks included linking Hg emissions with substrate Hg speciation and assessment of the speciation of mercury in the air associated with mining sites. The atmospheric emission work has built on a previous U.S. Environmental Protection Agency Science To Achieve Results (STAR) grant #R822529, “Investigation of the Light Enhanced Emissions of Hg from Substrate,” to M.S. Gustin. A brief summary of findings is given below.

Hg fluxes were measured from representative geologic units for 18 areas of Hg enrichment. The sites studied include areas naturally Hg-enriched and exploited for Hg, gold, silver, copper, lead, and zinc, and energy resources, including geothermal, oil and gas, as well as those of anthropogenic contamination where Hg was added to extract gold and silver from ores. Mercury fluxes from areas of hydrothermal alteration not associated with ore deposits and of rocks with background Hg concentrations also were collected. For nine of these areas, emissions were scaled up to provide regional estimates (Gustin, 2003). Data was developed that also allowed us to scale up natural source mercury emissions for the state of Nevada (Zehner and Gustin, 2002). Reactive gaseous mercury concentrations were measured in the air above two naturally enriched areas: one that has been significantly impacted by mining (Sulphur Bank Superfund Site, Clear Lake, California) and a second that is fairly undisturbed (Steamboat Springs Geothermal Area, Steamboat Springs, Nevada). In addition, Hg emissions from one area of anthropogenic Hg contamination (Carson River Superfund Site, Lyon/Churchill, Nevada,) also were measured. Reactive gaseous Hg data also were collected for a pristine area within the same region for comparison. Hg emissions were measured from mine waste in the New Idria mining district, Idria, California, for both pre- and postremediation sites. Data demonstrated that covering of mine waste significantly reduced Hg emissions to the atmosphere. Detailed laboratory experiments were done in collaboration with the Stanford group, which involved measuring mercury emissions as a function of the chemical form of Hg identified in the substrate by XAFS spectroscopy under light and dark conditions. Specific findings from these combined studies are as follows: (1) as particle size decreases, Hg concentration, Hg emissions, and light:dark emission ratio increases; (2) metacinnabar-bearing samples exhibit higher light:dark ratios than those containing cinnabar; and (3) the presence of more soluble Hg species also correlates positively with higher light:dark ratios. These findings suggest that more soluble Hg-containing minerals emit more Hg to the atmosphere. The major environmental implication of this finding is that Hg mining sites that have high concentrations of soluble Hg-containing species represent a greater risk to the environment than those containing less soluble Hg-containing species.

Objective 6: The Use of Hg Isotope Fractionation as a Potential Means of Identifying Hg from Specific Localities

This portion of our project examined the potential usefulness of Hg isotope ratios in determining the source of mercury pollution at a particular environmental site. It is well known that the ratios of some natural isotopes of elements such as oxygen (a stable or nonradiogenic isotope) or lead (an unstable or radiogenic isotope) can vary considerably depending on the physicochemical conditions that prevailed during their incorporation into a mineral phase, an organism, or a plant. Also, it is widely believed, however, that the heavy nonradiogenic isotopes of elements such as Hg, which has seven naturally occurring isotopes ( 196Hg, 198Hg, 199Hg, 200Hg, 201Hg, 202Hg, 204Hg), simply are too massive for biological processes to cause much preferential incorporation (or fractionation) of one isotope over another of the same element. Nonetheless, we decided to examine the variation of different Hg isotopes in a variety of natural mineral samples from quite different origins to determine if any natural variation in their ratios might be useful as a Hg source indicator. A variety of Hg-containing minerals were obtained from very different types of natural parageneses (i.e., different conditions of formation) and as well from different anthropogenic treatments (e.g., calcination or roasting of cinnabar ore). The Stanford-U.S. Geological Survey Sensitive High Resolution Ion Microprobe (SHRIMP) was used to measure 201Hg/ 202Hg ratios from these samples. The variation in this ratio from sample to sample was found to be approximately the same as the experimental error (about 0.0003), which suggests that either SHRIMP-based work does not provide sufficient precision or that the 201Hg/ 202Hg ratio shows insufficient variation to be useful as a source indicator. Additional studies using a more sensitive multicollector, inductively coupled plasma mass spectrometer are needed, however, before abandoning the idea that Hg isotope ratios are of no use in determining the source of the Hg in organisms such as fish.

Objective 7: Speciation of Mercury and Mode of Transport from Placer Gold Mine Tailings

Historic placer gold mining in the Clear Creek tributary to the Sacramento River ( Redding, CA) has impacted highly the hydrology and ecology of an important salmonid spawning stream. Restoration of the watershed utilized dredge tailings contaminated with Hg introduced during gold mining, posing the possibility of persistent Hg release to the surrounding environment, including the San Francisco Bay Delta. Column experiments were performed to evaluate the extent of Hg transport under chemical conditions potentially similar to those in river restoration projects utilizing dredge tailings such as at Clear Creek. Physicochemical perturbations, in the form of shifts in column influent ionic strength and the presence of a low molecular weight organic acid, were applied to coarse and fine sand placer tailings containing 109-194 and 69-90 ng-Hg/g, respectively. Significant concentrations of mercury, up to 16 μg/L, leached from these sediments in dissolved and particle-associated forms. Sequential chemical extractions of these tailings indicate that elemental Hg [Hg(0)] initially introduced during gold mining has been transformed to readily soluble species such as Hg oxides and chlorides (3-4%), intermediately extractable phases that likely include (in)organic sorption complexes and amalgams (75-87%), and fractions of highly insoluble forms such as Hg sulfides (6-20%; e.g., cinnabar and metacinnabar). XAFS spectroscopic analysis of colloids obtained from column effluent identified cinnabar particles as the dominant mobile Hg-bearing phase. The fraction of intermediately extractable Hg phases also likely includes mobile colloids to which Hg is adsorbed. The main environmental implication of this work is that elemental Hg is transformed into other forms of Hg during its transport from the Sierra Nevada foothills to the San Francisco Bay Delta, including both soluble Hg salts and insoluble Hg sulfides. This finding raises important questions about the various pathways that Hg follows during its transport from placer gold mining regions, where no other forms of Hg than Hg(0) should exist, to major wetlands such as the San Francisco Bay Delta. The results of this study are in press in Environmental Science & Technology.

Objective 8: Role of Organic Acids in Promoting Colloidal Transport of Hg From Mine Tailings

Inoperative Hg mines can contaminate surrounding ecosystems via transport of dissolved and particle-associated species of Hg and other heavy metal(loid)s. In this project, columns packed with a calcined Hg ore were leached with low molecular weight organic acid solutions (containing oxalate and citrate in concentrations of 10 - 500 μM each) in an attempt to simulate infiltration through the rooting zone of revegetated mine waste. This addresses: (1) the physicochemical conditions under which colloids may be mobilized; (2) the speciation of Hg in mobilized colloids; and (3) the extent of colloidal Hg transport. For all organic solution concentrations investigated, colloid-associated Hg was mobilized, with the onset of particulate Hg transport occurring later for lower low molecular weight organic acid concentrations. Chemical analyses of eluted colloids and 20 nm filtrates of column effluent indicated that over the timeframes of the column experiments (3 weeks to 3 months), 98 percent (by weight) of Hg mobilized from the column was in particulate forms. Mercury speciation was performed using Hg LIII-edge EXAFS spectroscopy and TEM with X-ray energy dispersive spectrometry, and indicated that HgS minerals (cinnabar and metacinnabar) dominate the Hg species in the mobilized colloids. Although not directly identified in this study, Hg adsorbed to mineral colloids is another likely mode of transport. The results of this project suggest that transport of colloid-associated Hg from revegetated Hg mine tailings sites may be of potential environmental concern, particularly in cases where sensitive wetland and/or estuarine environments are hydrologically proximate to those sites. They also demonstrate that from a chemical standpoint, the gradual infiltration of even very low concentrations of organic acids into mine tailings waste eventually will instigate conditions under which colloid mobilization can occur.

The results of this project are of particular potential relevance to revegetated mine tailing environments as revegetation is commonly used to hinder erosion. When exposed to toxins such as dissolved Al, which is prevalent under the acidic conditions typical of mine tailing environments, plants commonly exude organic acids such as citrate into the rhizosphere as a defense against Al phytotoxicity. Microbial degradation of dead plant tissue can provide a further significant source of organic acids. Such organic species can strongly sorb to positively charged mineral components, as demonstrated by a variety of laboratory-based adsorption studies. Importantly, mineral sorption of organic acids can act to protect them against biodegradation, thus potentially allowing a substantial surface coverage of organic material to be gradually accumulated, as has been previously noted to occur on mineral particles in different acid soil horizons. Chemical conditions that render colloidal mine tailings materials susceptible to mobilization when exposed to appropriate physical conditions (e.g., periods of intense rainfall) are, therefore, conceivable in revegetated mine tailings environments. Field studies into the potential impact of revegetation on the mobilization of colloidal materials from mine tailings materials are, however, required before the true impact of such processes can be accurately assessed. The results of these studies have been submitted for publication to Environmental Science & Technology (Slowey, et al., 2005), and the results of a separate study of the effect of low molecular weight organic acids on mineral particle dissolution have been published in Langmuir (Johnson, et al., 2004).


Journal Articles on this Report : 26 Displayed | Download in RIS Format

Other project views: All 93 publications 28 publications in selected types All 27 journal articles
Type Citation Project Document Sources
Journal Article Brown GE, Kim CS, Shaw S, Lowry GV, Rytuba JJ, Gustin MS. Processes controlling the chemical/isotopic speciation and distribution of mercury from contaminated mine sites. Abstracts of Papers of the American Chemical Society 2002;223(Pt 1):U524-U525 R827634 (Final)
not available
Journal Article Coolbaugh MF, Gustin MS, Rytuba JJ. Annual emissions of mercury to the atmosphere from natural sources in Nevada and California. Environmental Geology 2002;42(4):338-349 R827634 (Final)
not available
Journal Article Engle MA, Gustin MS, Zhang H. Quantifying natural source mercury emissions from the Ivanhoe Mining District, north-central Nevada, USA. Atmospheric Environment 2001;35(23):3987-3997. R827634 (2000)
R827634 (Final)
not available
Journal Article Engle MA, Gustin MS. Scaling of atmospheric mercury emissions from three naturally enriched areas: Flowery Peak, Nevada, Peavine Peak, Nevada and Long Valley Caldera, California. Science of the Total Environment 2002;290(1-3):91-104. R827634 (Final)
not available
Journal Article Gustin MS, Lindberg SE, Austin K, Coolbaugh M, et al. Assessing the contribution of natural sources to regional atmospheric mercury budgets. Science of the Total Environment 2000; 259(1): 61-71. R827634 (2000)
R827634 (Final)
not available
Journal Article Gustin MS, Biester H, Kim CS. Investigation of the light-enhanced emission of mercury from naturally enriched substrates. Atmospheric Environment. 2002;36(20):3241-3254. R827634 (Final)
R827622E02 (Final)
not available
Journal Article Gustin MS, Nacht D, Giglini A, Engle M. Speciation of mercury in the atmosphere above naturally and anthropogenically mercury enriched substrate. American Chemical Society, Division of Environmental Chemistry 2002;42(1):755-758 (abstract). R827634 (Final)
not available
Journal Article Gustin MS. Are mercury emissions from geologic sources significant? A status report. Science of the Total Environment 2003;304(1-3):153-167. R827634 (Final)
not available
Journal Article Gustin MS, Coolbaugh M, Engle M, Fitzgerald B, et al. Atmospheric mercury emissions from mine wastes and surrounding geologically enriched terranes. Environmental Geology 2003;43(3):339-351. R827634 (Final)
not available
Journal Article Jay J, Morel FMM, Hemond HF. Mercury speciation in the presence of polysulfides. Environmental Science and Technology 2000;34:2196-2200. R827634 (Final)
R824778 (Final)
R827915 (1999)
R827915 (2001)
not available
Journal Article Johnson SB, Yoon TH, Brown Jr GE, Scales PJ, et al. Effect of simple organic acid adsorption on the stability of aqueous metal oxide systems. American Chemical Society, Division of Environmental Chemistry 2003;43(1):512-518 (abstract). R827634 (Final)
not available
Journal Article Johnson SB, Yoon TH, Slowey AJ, Brown Jr GE. Adsorption of organic matter at mineral/water interfaces: 3. Implications of surface dissolution for adsorption of oxalate. Langmuir 2004;20(26):11480-11492. R827634 (Final)
not available
Journal Article Kim CS, Rytuba JJ, Brown Jr GE. Utility of EXAFS in characterization and speciation of mercury-bearing mine wastes. Journal of Synchrotron Radiation. 1999;6:648-650. R827634 (2001)
R827634 (Final)
not available
Journal Article Kim CS, Brown Jr GE, Rytuba JJ. Characterization and speciation of mercury-bearing mine wastes using X-ray absorption spectroscopy (XAS). Science of the Total Environment 2000;261(1-3):157-168. R827634 (2000)
R827634 (2001)
R827634 (Final)
not available
Journal Article Kim CS, Rytuba JJ, Brown GE Jr. EXAFS study of mercury(II) sorption to Fe- and Al-(hydr)oxides. I. Effects of pH. Journal of Colloid and Interface Science 2004;271(1):1-15. R827634 (2001)
R827634 (2002)
R827634 (Final)
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Journal Article Kim CS, Rytuba JJ, Brown Jr GE. Geological and anthropogenic factors influencing mercury speciation in mine wastes. Applied Geochemistry 2004a;19(3):379-393. R827634 (2001)
R827634 (Final)
not available
Journal Article Kima CS, Rytuba J, Brown GE. EXAFS study of mercury(II) sorption to Fe- and Al-(hydr)oxides - II. Effects of chloride and sulfate. Journal of Colloid and Interface Science 2004;270(1):9-20 R827634 (2001)
R827634 (2002)
R827634 (Final)
not available
Journal Article Lindberg SE, Zhang H, Vette AF, Gustin MS, et al. Dynamic flux chamber measurement of gaseous mercury emission fluxes over soils: effect of flushing flow rate and verification of a two-resistance exchange interface simulation model. Atmospheric Environment 2002;36(5):847-859. R827634 (Final)
not available
Journal Article Lowry GV, Shaw S, Kim CS, Rytuba JJ, Brown Jr GE. Macroscopic and microscopic observations of particle-facilitated mercury transport from New Idria and Sulphur Bank mercury mine tailings. Environmental Science & Technology 2004;38(19):5101-5111. R827634 (2002)
R827634 (Final)
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  • Journal Article Nacht DM, Gustin MS, Engle MA, Zehner RE, Giglini AD. Atmospheric mercury emissions and speciation at the Sulphur Bank Mercury Mine Superfund Site, Northern California. Environmental Science & Technology 2004;38(7):1977-1983. R827634 (Final)
    R829800 (2004)
    R829800 (Final)
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  • Journal Article Nacht DM, Gustin MS. Mercury emissions from background and altered geologic units throughout Nevada. Water, Air, & Soil Pollution 2004;151(1-4):179-193. R827634 (Final)
    R829800 (2004)
    R829800 (Final)
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  • Journal Article Sladek C, Gustin MS, Kim CS, Biester H. Application of three methods for determining mercury speciation in mine waste. Geochemistry: Exploration, Environment, Analysis 2002;2(4):369-375. R827634 (Final)
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    Journal Article Slowey AJ, Johnson SB, Rytuba JJ, Brown Jr GE. Colloid-associated arsenic and mercury: Enhancement of transport. American Chemical Society, Division of Environmental Chemistry 2003;43(1):163-169 (abstract). R827634 (Final)
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    Journal Article Slowey AJ, Rytuba JJ, Brown Jr GE. Speciation of mercury and mode of transport from placer gold mine tailings. Environmental Science and Technology 2005;39(6):1547-1554. R827634 (Final)
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  • Journal Article Zehner RE, Gustin MS. Estimation of mercury vapor flux from natural substrate in Nevada. Environmental Science and Technology 2002;36(19):4039-4045. R827634 (Final)
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  • Journal Article Zhang H, Lindberg SE, Barnette MO, Vette AF, Gustin MS. Dynamic flux chamber measurement of gaseous mercury emission fluxes over soils. Part 1: simulation of gaseous mercury emissions from soils using a two-resistance exchange interface model. Atmospheric Environment 2002;36(5):835-846. R827634 (Final)
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    Supplemental Keywords:

    mercury, mercury contamination at mining sites, mercury speciation in mining environments, X-ray absorption spectroscopy, colloidal transport of mercury, mercury isotopes, atmospheric emissions of mercury,, RFA, Scientific Discipline, Waste, Water, Ecosystem Protection/Environmental Exposure & Risk, POLLUTANTS/TOXICS, Bioavailability, Hydrology, Contaminated Sediments, Remediation, Environmental Chemistry, Arsenic, Chemistry, Fate & Transport, Water Pollutants, Groundwater remediation, Mercury, fate and transport, contaminated mines, colloidal particles, contaminated sediment, chemical speciation, emissions, biogeochemical cycling, methylmercury, mining, geochemistry, sulfide, atmospheric deposition, groundwater, mercury vapor

    Relevant Websites:

    Synthesis Report of Research from EPA’s Science to Achieve Results (STAR) Grant Program: Mercury Transport and Fate Through a Watershed (PDF) (42 pp, 760 K)

    Progress and Final Reports:

    Original Abstract
  • 2000 Progress Report
  • 2001 Progress Report