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DEVELOPMENT OF A WATERSHED-BASED MERCURY POLLUTION CHARACTERIZATION SYSTEM
Dai, T., T. A. Wool, AND R B. Ambrose Jr. DEVELOPMENT OF A WATERSHED-BASED MERCURY POLLUTION CHARACTERIZATION SYSTEM. Presented at Ecological Society of America Meeting, Madison, WI, August 5-10, 2001.
Develop, test, and refine models to evaluate sub-basins to determine whether local water quality problems due to excessive nutrient loading exist, and if so, to characterize them and determine their relationships to nutrient loading. Develop models to simulate overland flow and non-point source pollutant loads to track and assess nutrient loadings across watersheds and provide approaches for estimating nutrient budgets within sub-basins and for predicting changes in nutrient budgets in response to changes in watershed activities/land use/land cover. Demonstrate the application of the recommended approach/models for predicting changes in nutrient budgets in response to changes in proposed watershed activities/land use/land cover, resulting in specific recommendations for reducing the nutrient loads to a basin. For coherence, cooperation, and economics, these models will be housed in a unified, consistent, computational environment for environmental analyses that allows teaching (i.e., technology transfer) to multiple users (users concentrate on problem, not model input/output); that appeals to multi-disciplinary groups for distribution and use as a consistent assessment methodology (includes models, tools, modular design and facilitated updates of science/engineering); that includes resident visualization, animation tools, documentation and tutorials on-line, hooks to GIS and environmental databases; and is executable on UNIX, personal computers, and HPC resources.
Objective # 2.2 Conserve and enhance nation's waters: By 2005, conserve and enhance the ecological health of the nation's (state, interstate, and tribal) waters and aquatic ecosystems-rivers and streams, lakes, wetlands, estuaries, coastal areas, oceans, and groundwater-so that 75% of waters will support healthy aquatic communities.
To investigate total mercury loadings to streams in a watershed, we have developed a watershed-based source quantification model ? Watershed Mercury Characterization System. The system uses the grid-based GIS modeling technology to calculate total soil mercury concentrations and mercury loadings from direct atmospheric deposition, surface runoff, soil erosion and point sources. The input for the system includes land use, soil type, digital elevation, stream distribution, climate and atmospheric monitoring data. In addition, mercury reduction rate constant in the upper soil layer must be specified. The equations for mercury fate in soils were modified from a pollutant fate and transport model (IEM-2M) developed by U. S. Environmental Protection Agency. Using Watershed Mercury Characterization System, we calculated mercury loads in 20 sub-watersheds in the Savannah River watershed of Georgia and South Carolina. Sensitivity analyses indicate that mercury loading rates from this watershed are affected significantly by the atmospheric deposition flux, the proportion of impervious area, the proportion of direct water surface area, and the soil mercury reduction rate constant. Watershed Mercury Characterization System is distributed as a software extension for ArcView GIS.