Grantee Research Project Results
2006 Progress Report: Assessment of Natural Source (Geologic and Vegetation) Mercury Emissions: Speciation, Mechanisms and Significance
EPA Grant Number: R829800Title: Assessment of Natural Source (Geologic and Vegetation) Mercury Emissions: Speciation, Mechanisms and Significance
Investigators: Gustin, Mae Sexauer , Zehner, Richard E. , Rytuba, James J. , Johnson, Dale W. , Sedinger, Ben , Hanson, Brian , Peterson, Christianna , Weaver, Coty , Zhang, Hong , Stamenkovic, Jelena , Ericksen, Jody , Fay, Laura , Martindale, Lindsey , Engle, Mark , Xin, Mei , Markee, Melissa , Weisburg, Peter , Pillai, Rekha , Lyman, Seth , Lindberg, Steve , Kuiken, Todd , Ellis, Tyler
Current Investigators: Gustin, Mae Sexauer , Zehner, Richard E. , Rytuba, James J. , Johnson, Dale W. , Hatchett, Ben , Sedinger, Ben , Hanson, Brian , Peterson, Christianna , Weaver, Coty , Zhang, Hong , Stamenkovic, Jelena , Ericksen, Jody , Fay, Laura , Martindale, Lindsey , Engle, Mark , Xin, Mei , Markee, Melissa , Weisburg, Peter , Pillai, Rekha , Lyman, Seth , Lindberg, Steve , Kuiken, Todd , Ellis, Tyler
Institution: University of Nevada - Reno , United States Geological Survey , University of Tennessee , Tennessee Technological University
Current Institution: University of Nevada - Reno , Desert Research Institute , Tennessee Technological University , United States Geological Survey , University of Tennessee
EPA Project Officer: Chung, Serena
Project Period: January 1, 2003 through December 31, 2005 (Extended to December 31, 2007)
Project Period Covered by this Report: January 1, 2006 through December 31, 2007
Project Amount: $891,545
RFA: Mercury: Transport, Transportation, and Fate in the Atmosphere (2001) RFA Text | Recipients Lists
Research Category: Heavy Metal Contamination of Soil/Water , Air Quality and Air Toxics , Safer Chemicals , Air
Objective:
The major objective of this project is to develop data sets and process level information on natural (“in accordance with or determined by nature; based on the operations of the physical world”; Webster’s Third International Dictionary) mercury (Hg) fluxes between soil, vegetation, and air that will allow us to assess the significance of natural source versus anthropogenic sources of atmospheric for the United States. We are working towards this major objective by way of five sub objectives:
- Quantify Hg emissions from representative sources that have significant terrestrial coverage including geologically naturally Hg-enriched areas, background areas, and biotic sources (plants and forest fires).
- Develop process level information on gaps in our understanding of micrometeorological parameters and substrate characteristics controlling Hg emission and deposition to and from soils.
- Quantify the potential for re-emission of elemental and reactive Hg by substrates.
- Investigate the speciation of atmospheric Hg associated with naturally enriched sites.
- Using a GIS framework, scale natural source Hg emissions for the United States.
Progress Summary:
This year a paper was compiled that summarizes our current understanding of natural sources and sinks. This paper will be published in Applied Geochemistry as part of the special issue dedicated to the Eighth International Conference on Mercury as a Global Pollutant. This paper is titled “An update on our understanding of the role of natural sources and sinks in the biogeochemical cycle of Hg.”
Natural emissions of Hg to the atmosphere occur from areas with ongoing geologic activity (volcanic and geothermal) and from substrates with elevated Hg concentrations (> 100 ppb) as a result of geologic processes. Geologically derived naturally Hg-enriched areas are concentrated, but not limited, to broad global belts that coincide with major plate tectonic boundaries. A component of emission from these naturally enriched areas includes re-emission of Hg deposited from the atmosphere.
Other “natural” terrestrial sources of atmospheric Hg include releases from low-Hg containing soils/substrates (< 100 ppb), fire, and foliar surfaces. Emission from these sources is most likely re-emission of Hg deposited from the air by wet and dry processes, and is derived from both anthropogenic and natural sources. In addition to natural sources of atmospheric Hg, there are identified natural sinks including soils, plant foliage, and regions where the atmospheric chemistry facilitates formation of reactive gaseous Hg (RGM) (i.e., Polar Regions, marine boundary layer). This grant supports work that focuses on understanding natural Hg cycling. Progress for 2006 relative to the objectives as listed above is summarized.
Objective 1
Geothermal Areas and Volcanoes. Estimation of Hg releases from volcanoes and geothermal areas is difficult due to spatial and temporal variability and our overall lack of data. To fill this data gap, we collected and compiled data for three geologically representative geothermal areas. In the paper describing this work by Engle, et al. (2006), an estimate is given for geothermal emissions for the conterminous United States. Using empirical data collected from the three field sites and applying this to similar geothermal areas with heat flow greater than 200 mW/m2, they estimated 1.2 to 3.1 Mg per year is emitted from geothermal areas within the conterminous United States. In addition, Engle and Gustin , in a poster presentation at the Eighth International Conference on Hg as a Global Pollutant, indicated that currently Mount St. Helens is the only volcanic source of atmospheric Hg in the United States. Based on SO2 emission data from this volcano, they concluded that direct volcanic emissions during non eruptive years were negligible, and during eruptive years, the amount released would be dependent upon the size of the eruption (~ 0.05 to 800 Mg per year).
Low-Hg Containing Terrains. It is important to quantify the flux of Hg from broad terrestrial areas with background or low Hg concentrations, for these types of terrains cover most of the world’s land area. We have developed empirical data from background soils in Oklahoma, Wisconsin, Colorado, California, North Dakota, Nevada, and Tennessee and at five forested sites along the eastern seaboard. At several of these sites, long term data sets have been collected (Ericksen, et al., 2006; Lyman, et al., 2007; Stamenkovic, et al., in press, 2007; Kuiken, et al., submitted, 2007a; Kuiken et al., submitted, 2007b; Gustin, et al., 2006). One manuscript, published this year in Applied Geochemistry, focused on summarizing some of this information. The abstract is below. In addition, other papers have been submitted or are in press or published regarding data from field areas.
Abstract. Mercury exchange between the atmosphere and low mercury containing substrates Mae Sexauer Gustin, Mark Engle, Jody Ericksen, Seth Lyman, Jelena Stamenkovic, Mei Xin, Applied Geochemistry 2006;21(11):1913-1923.
Mercury (Hg) is emitted to the air from Hg-enriched and low Hg-containing (natural background) substrates. Emitted Hg can be geogenic, or can be derived from the re-emission of Hg that previously entered soil from the atmosphere. This atmospheric Hg can be derived from natural and/or anthropogenic sources and can be deposited by wet or dry processes. It is important to understand the relative magnitude of emission, deposition, and re-emission of Hg associated with terrestrial ecosystems with natural background soil Hg concentrations since these landscapes cover large terrestrial surface areas. This information is also important for developing biogeochemical mass balances, assessing the impacts of atmospheric Hg sources, and predicting the effectiveness of regulatory controls at local, regional, and global scales.
The major focus of this paper is to discuss air-substrate Hg exchange for low Hg containing soils (< 0.1 μg Hg g-1) from two areas in Nevada and one in Oklahoma, USA. Data collected with field and laboratory gas exchange systems are presented. Results indicate that in order to adequately characterize substrate-air Hg exchange, diel and seasonal data must be collected under a variety of environment conditions. Field and laboratory data showed that dry deposition of gaseous Hg to substrates with low Hg concentrations is an important process. Environmental parameters important in influencing emissions include soil water content, incident light, temperature, atmospheric oxidants, and air Hg concentrations. There are synergistic and antagonistic effects between these parameters complicating prediction of flux.
Mercury Releases due to Fires. As part of this project, mercury pools for three different ecosystems were quantified and the mercury released due to fires in these ecosystems has been quantified (Engle, et al., 2006). This work contributed to our limited understanding of Hg releases from fires, but also added to the controversy surrounding this issue. Friedli, et al. (2003) estimated approximately 3.7 ± 1.9 Mg/y were released by fires in the United States. Biwas, et al. (2003) suggested that soil burning released a more significant amount than biomass than fires. Engle, et al. (2006) found the contrary with Hg in foliage, bark, and litter being the dominant pool of Hg released during three fires. Since soils contain more than 90% of the total ecosystem Hg reservoir, the contribution of soils to emissions during fires needs to be resolved.
Mercury Air-Soil-Plant Exchange. As part of this project, data have been collected in controlled multiple- plant exposure chambers using a variety of plant species with different soil and air Hg exposure concentrations. Data were collected to understand the potential for Hg uptake and assimilation and release by foliage and the whole plant. Both naturally Hg-enriched substrates and those amended with HgCl2 have been used. In addition, soil, plant, and litter Hg flux data were collected from undisturbed monoliths housed in large mesocosms and field plots of tall grass prairie ecosystems. Mercury flux was also measured from foliage associated with vegetation growing in wetland mesocosms with four experimental designs.
During multiple plant exposure experiments and collection of field data in the wetlands and associated with a tall grass prairie system, foliar Hg concentrations were quantified over time allowing for comparison with actual accumulation with foliar flux measured with a gas exchange system (Millhollen, et al., 2006a; Millhollen, et al., 2006b, Fay, et al., 2007 a, b; Stamenkovic, et al., in preparation, 2007). Based on this work, it is now thought that foliar uptake and sequestration are important net sinks for gaseous elemental Hg, and emissions reflect re-emission of Hg deposited to the leaf surface. Whether plants transfer Hg from soil to the air is now unclear. The importance of the atmosphere as a dominant source for foliar Hg has been demonstrated by numerous laboratory and field studies (Frescholtz, et al., 2003; Ericksen, et al., 2003; Millhollen, et al., 2006a; Millhollen, et al., 2006b; Fay, et al., 2007 a,b). These studies have shown that plant uptake is dependent upon plant species and age, as well as air Hg concentrations. The influence of soil Hg concentrations on foliar Hg concentrations at low exposures is uncertain, although some studies have found that at a high soil exposure concentration, foliage concentrations are slightly impacted (Millhollen, et al., 2007 ; Fay, et al., 2007). Studies of litter fall and through fall in forested systems have shown that litter fall is the largest Hg flux to forest. The estimated contribution of atmospheric elemental Hg to forested floors by way of vegetation uptake representing indirect dry deposition was approximately 2400 to 6000 T/y (c.f., summary in Gustin, et al., submitted, 2007). Millhollen, et al. (2006) showed that although plants act as a net sink for atmospheric Hg, exchange at foliar surfaces is dynamic with emission, deposition, and re-emission all occurring.
The presence of a plant canopy has been demonstrated to impact the whole ecosystem flux by reducing emissions from underlying substrates. Litter-covered surfaces have also been shown to suppress emissions from the underlying bare soils (Stamenkovic, et al., in press, 2007). In controlled mesocosm studies, using Hg- contaminated soils (12.3 μg Hg/g), during leaf-out, it was clearly demonstrated that Hg flux declined as the soil was shaded by the developing leaf canopy (Gustin, et al., 2005). Under the full canopy, Hg flux was reduced 1.2 to 1.5 times relative to that occurring from bare soil. Recent work by Kuiken, et al. (submitted, 2007a) showed that emissions from litter- covered forest floors were higher in the winter than in the summer and attributed this largely due to lack of the leaf canopy in the winter. This work clearly illustrates the need to include seasonality and litter covered surfaces in estimates of the direction and magnitude of Hg flux from forested systems.
Experiments investigating single plant responses to changing air Hg exposures and CO2 exposures in highly controlled experiments have been completed and the data are being compiled into a manuscript.
Mercury Deposition Associated With Saline Water Bodies. Recent studies have shown that Hg deposition may be promoted in areas associated with saline water bodies. During this past year we have had an initiative that focused on measurement of air Hg speciation and Hg fluxes associated with the Great Salt Lake. This work is ongoing and will continue through the summer of 2007. We expect to begin compiling the results of this work into a manuscript in fall/winter 2007/2008.
Objective 2
Factors thought to be important in controlling air-substrate exchange associated with naturally Hg-enriched substrates (> 100 ppb) include those that control the magnitude of the flux, such as substrate Hg concentration, rock type, the presence and type of hydrothermal alteration, and the presence of heat sources and geologic structures. Meteorological parameters, especially light, temperature, and precipitation are factors demonstrated to be important in influencing flux on seasonal and diel time steps (Gustin, et al., 2006). Work from this project has shown that soil moisture plays an important role in controlling emissions from naturally Hg- enriched soils and low- Hg containing soils. These four parameters are important in enhancing Hg emissions. Since each exhibits significant natural variability on diel and seasonal time steps and Hg flux is correlated with these parameters, it is not surprising that Hg air-substrate exchange also exhibits significant variability across space and time. It is important to consider this variability when developing natural source emission estimates based on point source measurements and to collect empirical data that reflects this variability (c.f., Gustin, et al., in revision/submitted 2007; Stamenkovic and Gustin, in preparation, 2007; Lyman and Gustin, in preparation, 2007). Engle (2005) has demonstrated that atmospheric ozone will enhance Hg released from both Hg-enriched and natural background soils. This suggests that spatial variability in atmospheric chemistry can also influence substrate Hg release, with those areas impacted by urban air pollutants having potentially exacerbated emissions.
Controlled laboratory studies assessing the influence of soil properties on elemental Hg flux as well as the potential for re-emission driven by environmental factors such as ultraviolet radiation, relative humidity and soil moisture have been completed (Xin, et al., submitted, 2007; Xin and Gustin, in press, 2007).
Abstract. Xin, Mei and Gustin, M.S. Gaseous elemental mercury exchange with low mercury containing soils: investigation of controlling factors. Applied Geochemistry (in press).
Deposition of atmospheric elemental mercury (Hg0) to soils may be an important pathway for the transfer of Hg0 to terrestrial ecosystems. In this study a laboratory method was applied to investigate the role of soils with natural background Hg concentrations (< 0.1 μg/g) as a source or sink for atmospheric Hg0 and to identify factors influencing Hg0 exchange between these soils and air. Air–soil Hg0 exchange was measured for a variety of dry substrates (8 pure soil constituents and 35 soils) under controlled experimental conditions. Fluxes measured using the pure soil constituents indicated that the mineralogical nature of the soil particles may play an important role in the sorption of atmospheric Hg0. In individual tests for 26 of the 35 natural soils, statistically significant linear correlations were found between Hg0 flux and air Hg0 concentration. Mercury flux under light conditions was typically higher than that in the dark, and soil air compensation points (CP, the air Hg0 concentration at which there is no net Hg0 exchange) were significantly higher under light exposure. When all soil data were combined, at low air concentrations (2.8 ± 0.8 ng/m3) soils emitted Hg0 to the air in light conditions (mean flux: 1.3 ± 1.0 ng/m2hr) and adsorbed Hg0 in dark conditions (mean flux: –1.1 ± 1.2 ng/m2hr); while at elevated air Hg0 concentration (5.8 ± 1.0 ng/m3) deposition was the dominant flux (mean flux of –2.1 ± 1.6 and –4.6 ± 1.25 ng/m2hr in the light and dark, respectively). At air Hg0 concentrations similar to the ambient air (< 5 ng/m3; 1.7 ± 1.6 ng/m3), Hg0 concentration in the air, light, and soil Hg concentration were significantly correlated with air–soil Hg0 exchange, while at higher air Hg0 concentrations (≥ 5 ng/m3; 8.2 ± 2.2 ng/m3) that might be found in urban areas, soil Hg concentration, pH, and organic matter were the primary factors correlated with Hg0 flux. This study indicates that natural background soil may be a source or sink of atmospheric Hg0 depending on environmental parameters and soil physical and chemical properties.
Objective 3
A paper describing detailed laboratory work investigating re-emission of Hg added in solution to simulate a rain event and elemental Hg dry deposition from soils.
Abstract. Mei Xin, Mae Gustin, Dale Johnson. Laboratory investigation of the potential for re-emission of atmospherically derived Hg from soils. Submitted to Environmental Science & Technology.
This paper presents data from controlled laboratory experiments focused on investigating the effect of moisture, visible and ultraviolet light on the emission and re-emission of mercury (Hg) from two soils, one with low or background Hg concentrations (14 ng g-1) and a soil naturally enriched in Hg (4800 ng g-1). Water addition was found to increase emissions from dry soils by an amount greater than that occurring during exposure to PAR or UV-A radiation, while UV-B and UV-C exposures facilitated the greatest release. Overall exposures only a small percentage of Hg (II) added in a wet spike simulating a precipitation input was released immediately after addition (< 3%). The majority of the Hg being released during all exposures was indigenous, and either an original component of the soil or derived from past wet and dry deposition. Under dark and light conditions elemental Hg was deposited to the dry low Hg-containing soil. Based on experimental results, it is hypothesized that dry deposition of gaseous elemental Hg is an important input to low Hg soils and light, water and UV-A exposures promote desorption and re-emission of elemental Hg. UV-B exposure is hypothesized to promote indirect photoreduction of Hg(II) existing in the soil. The available pool and the form of Hg in the soil, as well as the chemistry of the soil, will determine the overall flux response to environmental stimulation of emissions.
Field work has also been focused on trying to understand Hg emission and deposition at three sites in Nevada. The ongoing work will provide important information on the significance of dry Hg deposition and re-emission.
Abstract. Seth N. Lyman, Mae Sexauer Gustin, Eric M. Prestbo, Frank J. Marsik. Estimation of dry deposition of atmospheric mercury in Nevada by direct and indirect methods. Environmental Science & Technology 41:1970-1976.
Atmospheric models and limited measurements indicate that dry deposition of atmospheric mercury is an important process by which mercury is input to ecosystems. To begin to fill the measurement data gap, multiple methods were used simultaneously during seasonal campaigns conducted in 2005 and 2006 to estimate dry deposition of atmospheric mercury at two Mercury Deposition Network (MDN) sites in rural Nevada, U.S.A. and in Reno, Nevada, U.S.A. Gaseous elemental mercury (Hg0), reactive gaseous mercury (RGM), and particulate-bound mercury (Hgp) concentrations were measured using Tekran® 2537A/1130/1135 systems. These speciated measurements were combined with on-site meteorological measurements to estimate depositional fluxes of RGM and Hgp using dry deposition models. Modeled fluxes were compared with more direct measurements obtained using polysulfone cation-exchange membranes and foliar surfaces. Dynamic flux chambers were used to measure soil mercury exchange.
RGM concentrations were higher during warmer months at all sites, leading to seasonal variation in the modeled importance of RGM as a component of total depositional load. The ratio of dry to wet deposition was between 10 and 90%, and varied with season and with the methods used for dry deposition approximations. This work illustrates the variability of mercury dry deposition with location and time and highlights the need for direct dry deposition measurements.
Objective 4
We have, over the past year, measured air Hg speciation and soil air Hg exchange as well as the potential for dry deposition of Hg at two national Mercury Deposition Network (MDN) sites in Nevada as well as at one location just north of Reno, Nevada. One paper has been published regarding this work (Lyman, et al., 2007) and a second one is just about ready for submission (Lyman and Gustin, in preparation, 2007). We are continuing to develop data sets on air Hg speciation and dry and wet Hg deposition at two MDN sites and one additional long- term monitoring site in Nevada. Two of the sites are in areas with low levels of natural Hg enrichment. Both of these sites show elevated Hg concentrations in air due to Hg enrichment. One paper describes air Hg speciation in detail within a naturally enriched area and the atmospheric Hg signature associated with this.
Abstract. Jelena Stamenkovic, Seth Lyman, Mae S. Gustin. Seasonal and diel variation of atmospheric mercury concentrations in the Reno (Nevada, USA) airshed. Atmospheric Environment (in press).
This paper describes total gaseous mercury (TGM) concentrations measured in Reno, Nevada from 2002 to 2005. The three-year mean and median air Hg concentrations were 2.3 and 2.1 ng m-3, respectively. Mercury concentrations exhibited seasonality, with the highest concentrations in winter, and the lowest in summer and fall. A well-defined diel pattern in TGM concentration was observed, with maximum daily concentrations observed in the morning and minimum in the afternoon. A gradual increase of TGM concentration was observed in the evening and over night. The early morning increase in TGM was likely due to activation of local surface emission sources by rising solar irradiance and air temperature. The subsequent decline and afternoon minimum in TGM were likely related to increased vertical mixing and the buildup of atmospheric oxidants during the day resulting in increased conversion to oxidized species that are quickly deposited, coupled with weakening of the surface emissions processes. The described diel pattern was seasonally modulated with the greatest amplitude in variation of TGM concentrations occurring in the summer. It is suggested based on the comparison of diel TGM pattern with other gaseous pollutants that natural source surface emissions are a dominant source of TGM in the study area.
Objective 5
A paper has been submitted to Applied Geochemistry that summarizes some of the scaling efforts this year. Below is a table that summarizes natural source emissions and deposition estimated based on our work for the conterminous United States.
Table 1. From Applied Geochemistry Paper That Has Been Submitted. Gustin, et al. (2007) summary of estimates for “natural source emissions” and deposition to the same areas in the United States. Note that these numbers are estimates.
Source/Sink |
Emission Estimate Mg/y |
Deposition Estimate Mg/y |
Reference |
||||
NATURAL SOURCES |
|
|
|
||||
Volcanoes |
0 |
|
Engle and Gustin, 2006 |
||||
Geothermal Areas |
1.2 to 3 |
|
Engle, et al., 2006 |
||||
Fires |
3.6 ± 1.9 |
|
Friedli, et al., 2003 |
||||
Naturally enriched soils |
|
|
|
||||
Nevada only |
2.1 to 2.4 |
|
Gustin, et al., 2000/Zehner and Gustin, 2002 |
||||
Western United States |
10 to 20 |
|
Gustin, et al., 2000/Gustin, et al., 2008 |
||||
LOW Hg and Naturally enriched substrates |
|
|
|
||||
Nevada |
3.6 to 10 |
1.5 to 3.5 |
Zehner and Gustin, 2002/Gustin, et al., 2008/Lyman, et al., 2007 |
||||
Western United States |
46 to 90 |
40 |
Gustin, et al., 2008*/Lyman, et al., 2007 |
||||
Conterminous United States |
44 to 150 |
120 |
Ericksen, et al., 2006 |
||||
|
|
|
|
||||
|
|
|
|
||||
Anthropogenic point sources |
150 |
|
|
* States include Arizona, California, Idaho, Nevada, Oregon, Utah, and Washington.
Continued work is ongoing with the scaling. The estimates above do not include any modeling based on environmental parameters and spatial and temporal variability. We will be working on this over the next year.
Future Activities:
We have ongoing work investigating air Hg speciation and the potential for Hg deposition associated with the Great Salt Lake. It has been suggested that playas and salt lakes may be sinks for atmospheric elemental Hg. We are continuing to monitor air Hg speciation northwest of Reno and in the Truckee Meadows Basin. We will apply dry deposition models and surrogate surfaces to estimate dry deposition at these sites. In addition, we will measure air Hg concentrations at a rural MDN site in Nevada this summer though collaboration with the U.S. Environmental Protection Agency (EPA) Region 9. This will give us air speciation data that will allow us to monitor dry deposition at rural, suburban, and urban locations. We will give two presentations at the Air Quality VI (AQVI) meeting this fall in Washington, DC, regarding this work. We will focus work this summer on scaling and comparing some of our assumptions with those applied in other mercury cycling models. Collaborations have already been established with Christian Seigneur and we will work with others within the U.S. Geological Survey (USGS) and the National Oceanic and Atmospheric Administration (NOAA).
References:
Engle MA, Gustin MS, Goff F, Counce DA, Janik CJ, Bergfeld D, Rytuba JJ. Atmospheric mercury emissions from substrates and fumaroles associated with three hydrothermal systems in the western United States. Journal of Geophysical Research 2006a;111(D17):D17304, doi:10.1029/2005JD006563.
Engle MA, Gustin MS, Johnson DW, Murphy JF, Miller WW, Walker RF, Wright J, Markee M. Mercury distribution in two Sierran forest and one desert sagebrush steppe ecosystems and the effects of fire. Science of the Total Environment 2006b;367(1):222-233.
Kuiken T, Gustin M, Lindberg S, Zhang H. Mercury emission from background soils: I. Mercury emission fluxes within a southeastern deciduous forest (USA). Applied Geochemistry (submitted, 2007a).
Kuiken T, Gustin M, Lindberg S, Zhang H. Mercury emission from background soils: II. Mercury emission fluxes within a transect of forests in the eastern USA. Applied Geochemistry (submitted, 2007b).
Millhollen AG, Obrist D, Gustin MS. Mercury accumulation in grass and forb species as a function of atmospheric carbon dioxide concentrations and mercury exposures in air and soil. Chemosphere, 2006a;65(5):889-897.
Millhollen AG, Gustin MS, Obrist D. Foliar mercury accumulation and exchange for three tree species. Environmental Science & Technology 2006b;40(19):6001-6006.
Journal Articles on this Report : 10 Displayed | Download in RIS Format
Other project views: | All 78 publications | 31 publications in selected types | All 29 journal articles |
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Type | Citation | ||
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Engle MA, Gustin MS, Johnson DW, Murphy JF, Miller WW, Walker RF, Wright J, Markee M. Mercury distribution in two Sierran forest and one desert sagebrush steppe ecosystems and the effects of fire. Science of the Total Environment 2006;367(1):222-233. |
R829800 (2005) R829800 (2006) R829800 (Final) |
Exit Exit Exit |
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Engle MA, Gustin MS, Goff F, Counce DA, Janik CJ, Bergfeld D, Rytuba JJ. Atmospheric mercury emissions from substrates and fumaroles associated with three hydrothermal systems in the western United States. Journal of Geophysical Research 2006;111, D17304, doi:10.1029/2005JD006563. |
R829800 (2004) R829800 (2006) R829800 (Final) |
Exit |
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Ericksen JA, Gustin MS, Xin M, Weisberg PJ, Fernandez GCJ. Air-soil exchange of mercury from background soils in the United States. Science of the Total Environment 2006;366(2-3):851-863. |
R829800 (2004) R829800 (2005) R829800 (2006) R829800 (Final) |
Exit Exit Exit |
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Fay L, Gustin M. Assessing the influence of different atmospheric and soil mercury concentrations on foliar mercury concentrations in a controlled environment. Water, Air, & Soil Pollution 2007;181(1-4):373-384. |
R829800 (2006) R829800 (Final) |
Exit |
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Fay L, Gustin MS. Investigation of mercury accumulation in cattails growing in constructed wetland mesocosms. Wetlands 2007;27(4):1056-1065. |
R829800 (2006) R829800 (Final) |
Exit |
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Gustin MS, Engle M, Ericksen J, Lyman S, Stamenkovic J, Xin M. Mercury exchange between the atmosphere and low mercury containing substrates. Applied Geochemistry 2006;21(11):1913-1923. |
R829800 (2005) R829800 (2006) R829800 (Final) |
Exit Exit Exit |
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Kuiken T, Gustin M, Zhang H, Lindberg S, Sedinger B. Mercury emission from terrestrial background surfaces in the eastern USA. II. Air/surface exchange of mercury within forests from South Carolina to New England. Applied Geochemistry 2008;23(3):356-368. |
R829800 (2006) R829800 (Final) |
Exit Exit Exit |
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Lyman SN, Gustin MS, Prestbo EM, Marsik FJ. Estimation of dry deposition of atmospheric mercury in Nevada by direct and indirect methods. Environmental Science & Technology 2007;41(6):1970-1976. |
R829800 (2006) R829800 (Final) |
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Millhollen AG, Gustin MS, Obrist D. Foliar mercury accumulation and exchange for three tree species. Environmental Science & Technology 2006;40(19):6001-6006. |
R829800 (2005) R829800 (2006) R829800 (Final) |
Exit |
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Millhollen AG, Obrist D, Gustin MS. Mercury accumulation in grass and forb species as a function of atmospheric carbon dioxide concentrations and mercury exposures in air and soil. Chemosphere 2006;65(5):889-897. |
R829800 (2005) R829800 (2006) R829800 (Final) |
Exit Exit Exit |
Supplemental Keywords:
mercury, natural Hg sources, geothermal Hg sources, natural Hg biogeochemical cycling, vegetation-air-soil Hg exchange,, Scientific Discipline, Air, INTERNATIONAL COOPERATION, Waste, TREATMENT/CONTROL, Ecosystem Protection/Environmental Exposure & Risk, POLLUTANTS/TOXICS, Air Quality, air toxics, Treatment Technologies, Environmental Chemistry, Chemicals, Fate & Transport, Environmental Monitoring, Bioremediation, Chemistry and Materials Science, fate and transport, contaminated sediments, air pollutants, Hg, mercury, mercury emissions, modeling, mercury cycling, hazardous waste, chemical kinetics, contaminants in soil, bioremediation of soils, atmospheric mercury chemistry, mercury chemistry, phytoremediation, atmospheric chemistry, atmospheric mercury cycling, atmospheric deposition, contaminant transport models, heavy metals, mercury vapor, atmospheric mercuryProgress and Final Reports:
Original AbstractThe perspectives, information and conclusions conveyed in research project abstracts, progress reports, final reports, journal abstracts and journal publications convey the viewpoints of the principal investigator and may not represent the views and policies of ORD and EPA. Conclusions drawn by the principal investigators have not been reviewed by the Agency.