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Modeling Mercury Exposure at Different Scales in the McTier Creek Watershed and Edisto River Basin SC USA
Citation:
Knightes, C., H. Golden, P. Bradley, G. Davis, C. Journey, P. Conrads, AND M. Brigham. Modeling Mercury Exposure at Different Scales in the McTier Creek Watershed and Edisto River Basin SC USA. Presented at 9th INTECOL International Wetlands Conference, Orlando, FL, June 03 - 08, 2012.
Impact/Purpose:
Presentation for the 9th INTECOL International Wetlands Conference and INTECOL 9, Orlando, FL June 3-7, 2012
Description:
Mercury (Hg) is the toxicant responsible for the largest number of fish advisories across the United States, with 1.25 million river miles under advisory. The processes governing fate, transport, and transformation of Hg in lotic ecosystems are not well-understood, in large part, because these systems are intimately linked with their surrounding watersheds. To understand the Hg exposure concentrations within streams and rivers, the Hg fate and transport within the watershed must be understood. Atmospheric deposition is the primary source of Hg to many aquatic ecosystems. However, in systems where the watershed area greatly exceeds the surface water area, the indirect loading of Hg coming from the watershed is often the dominant pathway of Hg supply to the stream habitat. Despite its importance, there is little understanding and associated modeling representation of how atmospherically deposited Hg transports and transforms within the watershed on its way to receiving streams. In this study, we apply a linked watershed hydrology and biogeochemical cycling (N, C, and Hg) model (VELMA, Visualizing Ecosystems for Land Management Assessment) to predict daily flow and daily fluxes and concentrations of total mercury (THg), methylmercury (MeHg), dissolved organic carbon (DOC), dissolved inorganic nitrogen (DIN), and dissolved organic nitrogen (DON). VELMA is a 3-dimensional spatially (pixel-based) and temporally (daily time step) explicit watershed model consisting of four soil layers, which simulates Hg, N, and C transport and transformation within the watershed. The modeling effort was performed in concert with a rigorous Hg sampling effort as part of the USGS NAWQA program, including a focused study reach and upstream sampling stations. VELMA was applied at a series of different scales within a Coastal Plain watershed (McTier Creek, SC, USA): a focused reach (0.11 km2), two sub-watersheds (28 km2, 24 km2) and the full watershed (79 km2). The focused reach data set
