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Characterizing mercury concentrations and fluxes in a Coastal Plain watershed: Insights from dynamic modeling and data

March 26, 2012

Mercury (Hg) is one of the leading water quality concerns in surface waters of the United States. Although watershed-scale Hg cycling research has increased in the past two decades, advances in modeling watershed Hg processes in diverse physiographic regions, spatial scales, and land cover types are needed. The goal of this study was to assess Hg cycling in a Coastal Plain system using concentrations and fluxes estimated by multiple watershed-scale models with distinct mathematical frameworks reflecting different system dynamics. We simulated total mercury (HgT, the sum of filtered and particulate forms) concentrations and fluxes from a Coastal Plain watershed (McTier Creek) using three watershed Hg models and an empirical load model. Model output was compared with observed in-stream HgT. We found that shallow subsurface flow is a potentially important transport mechanism of particulate HgT during periods when connectivity between the uplands and surface waters is maximized. Other processes (e.g., stream bank erosion, sediment re-suspension) may increase particulate HgT in the water column. Simulations and data suggest that variable source area (VSA) flow and lack of rainfall interactions with surface soil horizons result in increased dissolved HgT concentrations unrelated to DOC mobilization following precipitation events. Although flushing of DOC-HgT complexes from surface soils can also occur during this period, DOC-complexed HgT becomes more important during base flow conditions. TOPLOAD simulations highlight saturated subsurface flow as a primary driver of daily HgT loadings, but shallow subsurface flow is important for HgT loads during high-flow events. Results suggest limited seasonal trends in HgT dynamics.

Citation Information

Publication Year 2012
Title Characterizing mercury concentrations and fluxes in a Coastal Plain watershed: Insights from dynamic modeling and data
DOI 10.1029/2011JG001806
Authors H.E. Golden, C.D. Knightes, P.A. Conrads, G. M. Davis, T.D. Feaster, C. A. Journey, S.T. Benedict, M. E. Brigham, P. M. Bradley
Publication Type Article
Publication Subtype Journal Article
Series Title Journal of Geophysical Research
Index ID 70037876
Record Source USGS Publications Warehouse
USGS Organization South Atlantic Water Science Center

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