Impact/Purpose:

To improve the scientific understanding of the linkage between fish methylmercury and ambient mercury in the environment.

To complete a model for transformation and bioaccumulation of mercury than can be linked with models for atmospheric deposition and hydrology to yield a multimedia integrated modeling system capable of quantifying regional exposure to mercury.

To apply state of the art modeling to assess ecosystem interactions with exposures to mercury for impacted aquatic ecosystems (e.g., wetlands, lakes, rivers, estuaries) including spatially distributed (GIS-based) modeling of watersheds, lakes and rivers.

Description:

Mercury is released from a variety of sources and exhibits a complicated chemistry. According to the Mercury Study Report to Congress, mercury fluxes and budgets in water, soil, and other media have increased by a factor of two to five over pre-industrial levels. The primary exposure pathway for humans and wildlife is the consumption of contaminated fish and shellfish. Because mercury is a natural element, it will not degrade to simpler compounds, but rather will continue to cycle through the environment until sequestered (i.e., trapped in lake or ocean sediments). The goal of this research is to provide the scientific information and technical data needed to reduce uncertainties limiting the Agency's ability to assess and manage mercury and methylmercury risks; NERL/ERD's research program seeks to understand the environmental cycling of the major speciated forms of mercury, especially the characteristics that induce mercury methylation in ecosystems and the pathways of exposure.

Specifically, NERL/ERD's activities will focus on models of key parameters that promote methylmercury production (i.e., bacterial activity, sulfur, organic carbon, and bioavailability of Hg) and bioaccumulation. Research will evaluate the variability in methylmercury production among aquatic systems in the same region to understand transformation and bioaccumulation processes. Process understanding, including research funded by ORD STAR grants, will be incorporated in the development of aquatic and terrestrial models, and field and laboratory data (including data derived from regional REMAP projects) will be used to characterize key model parameters.

In cooperation with other Federal, State, and local agencies, ORD will also complete field and model studies in South Florida, and then test and apply the techniques developed to several prototype ecosystems (e.g., New England lakes, Georgia river basins). In earlier phases of these studies, ORD and cooperating parties have developed or refined several mercury fate models, including a WASP mercury screening model (Hg-WASP), the Everglades Mercury Cycling Model (E-MCM), a community bioaccumulation model (BASS), a field scale terrestrial mercury model (Hg-GLEAMS), and a spatially-distributed watershed mercury model (Hg Tool). The South Florida project will develop a spatially structured model that links mercury biogeochemistry and bioaccumulation in the E-MCM with hydrology and water quality models, including the Everglades landscape model ELM. This linked modeling system will be critical for assessing multiple interactive stressors, for analyzing the spatial component of mercury and methylmercury exposures (e.g., methylmercury concentrations in local fish populations vs. nesting/foraging areas for wading birds), and for evaluating the effectiveness of criterion-based restoration goals.

The Hg-WASPand the Hg Tool will be applied to mercury TMDL issues in Region 4 and to a regional analysis of mercury exposures in New England lakes and reservoirs (Region 1 REMAP project). These models will be refined based on knowledge gained in their application. ORD will add appropriate process descriptions elucidated by scientific studies published by STAR grantees or in the general scientific literature. These models will be documented and packaged for distribution to EPA, states, and the general technical community. Knowledge and data gained in this development effort will be used to develop or improve mercury analysis capabilities in existing models used by EPA in various regulatory programs. These include development of the hazardous waste identification rule with 3MRA, RCRA permitting for hazardous waste incinerators using IEM, and development of TMDLs with BASINS.

In cooperation with the Multimedia Integrated Modeling System (MIMS) development project, an appropriate set of watershed and water body mercury fate models will be linked with the regional atmospheric mercury model CMAQ. Code revisions or wrappers will be developed according to MIMS protocols to produce an integrated multimedia mercury modeling capability. The prototype multimedia model will be tested on local and regional datasets in order to provide information on structural and parameter uncertainty to the continuing model development process. The case studies will be completed and documented along with the integrated multimedia model. In conjunction with the MIMS program, the technology will be provided to EPA and the general technical community.

Record Details:

Record Type:PROJECT

Completion Date:09/30/2002

OMB Category:Other

Record ID: 56189

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Project Information:

Progress :Advances in process understanding resulting from extramural research have been incorporated in the development of a screening model for South Florida. The WASP-based Everglades Mercury Screening Model has been applied to evaluations of potential mercury loadings from agricultural areas and proposed hydrologic restoration scenarios for the Everglades. Features of the screening model have been incorporated into the Everglades Mercury Cycling Model (E-MCM) for applications in South Florida restoration and in the development of TMDL methodologies for mercury. Similarly, a community bioaccumulation model (BASS) has been developed for applications to South Florida and other aquatic ecosystems.

From the Everglades Mercury Screening Model, the simpler and more generally applicable Hg-WASP was developed. From the simple watershed spreadsheet model developed for the Mercury Study Report to Congress and the GIS-based watershed tool developed by EPA Region 4, a generally applicable watershed Hg Tool was developed. These two models have been applied to eight Hg TMDLs in river basins of the southeastern United States. Results have been reported to two technical conferences. Two years of data have been collected from New England lakes as part of REMAP study to compare biogeographic factors contributing to different mercury exposures.

NERL/ERD ABSTRCT/ORAL:

Loux, N.T. The Role of Temperature Disequilibrium in Monitoring Low Volatility Contaminant Migration. Abstract presented at: Fourth International Symposium of Elements in Biological, Environmental and Toxicological Sciences, Whistler, British Columbia, Canada, June 25-July 1, 2000.

Ravichandran, Mahalingam, Araujo, R., and Zepp, R.G. Role of humic substances on the photochemical reduction of mercury. Abstract presented at: 220th ACS National Meeting, Washington, DC, August 20-24, 2000.

Loux, N.T. The role of aqueous thin film evaporative cooling on rates of elemental mercury air-water exchange under temperature disequilibrium conditions. Abstract presented at: Georgia Water Resources Conference, Athens, GA, March 26-27, 2001

Ambrose, Jr., R.B., and Wool, T.A. Modeling mercury fate in seven Georgia watersheds. Abstract presented at: Workshop on the fate, transport, and transformation of mercury in aquatic and terrestrial environments, West Palm Beach, FL, May 8-10, 2001.

Ambrose, Jr., R.B., and Wool, T.A. Modeling tools used for mercury TMDLs in Georgia rivers. Abstract presented at: Georgia Water Resources Conference, Athens, GA, March 26-27, 2001.

Loux, N.T. The effect of salinity on rates of elemental mercury air/water exchange. Abstract presented at: International Workshop on Trends and Effects of Heavy Metals in the Arctic, McLean, VA, June 18-22, 2001.

Relevance :According to the Mercury Study Report to Congress, mercury fluxes and budgets in water, soil, and other media have increased by a factor of two to five over pre-industrial levels. The primary exposure pathway for humans and wildlife is the consumption of contaminated fish and shellfish. As mercury is a natural element, it will not degrade to simpler compounds, but rather will continue to cycle through the environment until sequestered (i.e., trapped in lake or ocean sediments). The goal of this research is to provide the scientific information and technical data needed to reduce uncertainties limiting the Agency's ability to assess and manage mercury and methylmercury risks.

Clients :Gail Mitchell, Region 4 WTMD, 404-562-9234; Region 1; Office of Water; Don Axelrad, Florida DEP, 850 414-1347

Project IDs:

ID Code :6406

Project type :OMIS