Grantee Research Project Results
2003 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 , Schorran, David E. , Zehner, Richard E. , Rytuba, James J. , Johnson, Dale W. , Hatchett, Ben , Hanson, Brian , Zhang, Hong , Ward, Jake , Fay, Laura , Martindale, Lindsey , Engle, Mark , Xin, Mei , Markee, Melissa , Lindberg, Steve , Kuiken, Todd
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 , Tennessee Technological University , United States Geological Survey , University of Tennessee , Desert Research Institute
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, 2003 through December 31, 2004
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 overall objective of this research project is to develop data sets and process-level information on mercury (Hg) fluxes between soil, vegetation, and air that will allow us to assess the significance of natural source Hg emissions relative to anthropogenic emissions for the United States. We are working towards this major objective by way of five specific objectives, which are to: (1) 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); (2) develop process-level information on gaps in our understanding of micrometeorological parameters and substrate characteristics controlling Hg emission and deposition to and from soils; (3) quantify the potential for reemission of elemental and reactive Hg by substrates; (4) investigate the speciation of atmospheric Hg associated with naturally enriched sites; and (5) scale natural source Hg emissions for the United States, using a geographic information system framework.
Progress Summary:
Objective 1
As a result of previous projects funded by the U.S. Environmental Protection Agency, we have built some significant data sets on Hg emissions from representative areas of geologic Hg enrichment and areas of anthropogenic contamination and disturbance. This year we focused on obtaining data from areas where we thought there were significant data gaps in our understanding of the inputs from naturally Hg-enriched geologic sources. We conducted intensive field campaigns in Lassen National Park and Yellowstone National Park. These areas represent specific types of geothermal areas that have the potential to be significant sources.
We made an intensive effort to develop a data set for Hg emissions from substrate with background Hg concentrations and different soil characteristics. This included areas in Oklahoma, Wisconsin, Colorado, California, Tennessee, and Nevada. Because areas with substrate with background concentrations of Hg cover most of the United States, it is important to develop some algorithms representative of them that we may use for scaling. Preliminary data indicate that emission rates for background sources are similar to those previously applied to global belts of geologic enrichment. These data indicate that large terrestrial surface areas with no natural enrichment are significant sources of Hg to the atmosphere.
We collected samples (pre- and postburn) from three areas impacted by wildfire, in collaboration with ongoing projects at the University of Nevada–Reno, to assess the input of Hg to the atmosphere from fires. Data collected will allow us to assess the potential for the amount of Hg released from both biota and soils from fires of different intensity. Unlike plume studies, these studies will allow us to more accurately quantify the amount of Hg released from vegetation and soils. Heating of the latter is thought to contribute a greater amount of Hg to the air than burning of foliage.
We also began compiling a database of substrate Hg fluxes for the United States and Hg concentrations in substrates in the United States. These data sets will be important for the scaling process.
Objective 2
During Year 1 of the project, we began to systematically investigate parameters that influence flux (for which algorithms that may be used in scaling had not been developed). We clearly know that these parameters strongly influence Hg emission from soils. They include soil moisture and precipitation, air Hg concentrations, and atmospheric oxidants. We also began experiments to quantify the influence of soil properties on elemental Hg adsorption from the air and emission. To meet this objective, we also have established four sites from which Hg flux is being monitored monthly to develop a data set that will allow us to model seasonal variations in Hg flux. These sites include a background and enriched site in Nevada, a background forest site and open field site in Tennessee.
Objective 3
Work is being conducted to assess the potential for elemental Hg and reactive Hg deposition to pure substrates and soils and the importance of reemission. Laboratory work has been the primary focus this year. We are using substrate from which we measured Hg fluxes in the field. A comparison of laboratory- and field-derived fluxes will allow us to determine the applicability of laboratory-derived data in scaling. We have found that air Hg concentrations and atmospheric oxidants exert significant control on soil Hg flux.
Objective 4
Speciation of Hg in the air has been measured from five naturally enriched sites. Significant laboratory work has been conducted to understand the release of reactive gaseous Hg from naturally enriched substrates. Significant results are that reactive gaseous Hg is emitted from soils, and this emission is related to Hg speciation in the soil and to exposure to atmospheric oxidants.
Objective 5
We currently are working on scaling up Hg emissions for the State of California, which will be used as a protocol for the U.S. scaling.
Because this is Year 1 of the project, publications that are a direct result of this project have not been released. However, publications are being prepared, and it is expected that there will be quite a few submitted in the next year.
These include:
• An invited paper for a book chapter and United Nations Environment Programme report entitled "Terrestrial mercury flux: is the net exchange up or down?"
• The role of soil moisture and precipitation in controlling mercury flux from substrate.
• Mercury emissions associated with three geologically distinct geothermal areas.
• Influence of atmospheric oxidants on mercury emissions from soils.
• Mercury releases from fires.
• Deposition and emission of elemental mercury from substrates: factors controlling mercury emissions from California
• In situ mercury flux from substrate with background mercury concentrations.
One member of our group, Dr. Jim Rytuba, has been asked to testify before the House Committee on Natural Resources and the Environment on the significance of natural source Hg emissions. Understanding the role of natural sources in the biogeochemical cycling of Hg is critical for assessing the potential for the success of regulatory controls on coal-fired utilities for reducing atmospheric Hg loadings. His testimony will become part of the Federal Register.
Future Activities:
Objective 1. We have several field initiatives planned for this year that should fill existing data gaps. These include measurement of fluxes from black shales, Dixie Valley geothermal area, and field initiatives for continued measurement of fluxes from background sources in the east and in the west. Assessment of the Hg released for several types of fires in two ecosystems will be completed and will be applied to scaling up the significance of fires as a source of atmospheric Hg. We also will scale up emissions from a background site in Tennessee (Standing Stone). The database of Hg fluxes will be completed this year. Work on the role of vegetation as a source or sink of atmospheric Hg in naturally enriched areas will be initiated.
Objective 2. Work on the role of soil moisture, precipitation, and atmospheric oxidants on facilitating the release of Hg from soils will be finalized. All three of these are being found to significantly enhance Hg emissions. The Tennessee Tech group will work on investigating the influence of photoreduction on facilitating reemission of atmospherically deposited reactive Hg. Monitoring will continue at semipermanent sites, along with site characterization and some experiments to look at flux from different settings.
Objective 3. Laboratory work on elemental Hg uptake and reemission will be completed, and the reemission of reactive Hg will be investigated in the laboratories at Tennessee Tech. We will conduct a field application of a stable Hg isotope as HgCl2 to determine the potential for reemission in an arid environment. This work can be compared with that of the Mercury Experiment To Assess Atmospheric Loading in Canada and the United States (METALLICUS) to help us decide how to model reemission in the scaling exercises.
Objective 4. Laboratory experiments to determine whether reactive gaseous Hg is emitted from naturally enriched substrates will be completed. We will measure reactive gaseous Hg emissions upwind and downwind of a naturally enriched site for which Hg fluxes have been characterized.
Objective 5. Scaling for California will be completed this year. This exercise will form the basis for scaling of terrestrial emissions for the United States.
For all of these objectives, manuscripts summarizing the work of Year 1 of the project will be prepared for publication.
Journal Articles:
No journal articles submitted with this report: View all 78 publications for this projectSupplemental Keywords:
air, ambient air, atmosphere, land, soil, adsorption, metals, heavy metals, scaling, terrestrial, public policy, decisionmaking, environmental chemistry, biology, geology, modeling, monitoring, analytical, EPA Region 1, EPA Region 2, EPA Region 3, EPA Region 4, EPA Region 5, EPA Region 6, EPA Region 7, EPA Region 8, EPA Region 9, EPA Region 10., 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.