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Mercury dynamics in a coastal plain watershed: insights from multiple models and empirical data
Citation:
GOLDEN, H. E., C. D. KNIGHTES, P. Conrads, G. Davis, T. Feaster, S. Benedict, C. Journey, M. Brigham, AND P. Bradley. Mercury dynamics in a coastal plain watershed: insights from multiple models and empirical data. Presented at American Geophysical Union Fall Meeting, San Francisco, CA, December 04 - 09, 2011.
Impact/Purpose:
The goal of this research is to develop methods and indicators that are useful for evaluating the condition of aquatic communities, for assessing the restoration of aquatic communities in response to mitigation and best management practices, and for determining the exposure of aquatic communities to different classes of stressors (i.e., pesticides, sedimentation, habitat alteration).
Description:
Interactions among atmospherically deposited mercury, abundant wetlands, and surface waters with elevated acidity and dissolved organic carbon (DOC) often lead to widespread mercury-related fish consumption advisories in the Coastal Plain of the southeastern United States (US). However, the science behind understanding mercury dynamics in these mixed land cover, Coastal Plain watersheds is just beginning to emerge. Watershed models are important tools for answering questions related to watershed mercury cycling--including the spatial and temporal variations in surface water mercury concentrations and fluxes--particularly when limited data exist and multiple models with different underlying dynamics are available. We quantify total mercury concentrations and fluxes to the outlet of McTier Creek Watershed, located in the upper Coastal Plain of South Carolina, US, an area with more diverse land cover, a larger drainage area, and different geophysical setting than many previous mercury studies in North America (primarily from small forested headwater boreal or northern forested catchments). We apply three independently developed watershed mercury models with distinct mathematical frameworks that emphasize different system processes. Because spatially-explicit watershed scale mercury modeling is a recent advancement, the use of multiple models combined with data affords broader insights to total mercury dynamics in the watershed. As a result, we employ a spatially-explicit grid based watershed mercury model (GBMM), the spatially-explicit VELMA-Hg model, and the semi-empirical TOPLOAD-Hg model for HgT concentration and flux calculations. We use the S-LOADEST model for seasonal total mercury fluxes, while measured in-stream total mercury concentrations and fluxes provide additional insights and data for model calibrations. Our findings begin to elucidate important abiotic processes controlling total mercury, areas within the landscape where total mercury at the outlet is derived, and potential governing dynamics over temporal variations of total mercury concentrations and fluxes throughout the simulation period within this Coastal Plain watershed.