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Characterizing mercury concentrations and fluxes in a coastal plain watershed: insights from dynamic modeling and data
Citation:
GOLDEN, H. E., C. D. KNIGHTES, P. Conrads, G. Davis, T. Feaster, C. Journey, S. Benedict, M. Brigham, AND P. Bradley. Characterizing mercury concentrations and fluxes in a coastal plain watershed: insights from dynamic modeling and data. Journal of Geophysical Research: Biogeosciences. American Geophysical Union, Washington, DC, 117(G01006):1 - 17, (2012).
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:
Mercury (Hg) is one of the leading water quality concerns in surface waters of the United States (U.S.). Although watershed-scale Hg cycling research has escalated in the past two decades, advances in the modeling of watershed Hg cycling processes in diverse physiographic regions, spatial scales, and land cover types are needed. We simulated total mercury concentrations and fluxes from a Coastal Plain watershed (McTier Creek) using three watershed Hg models and an empirical load model. Model output was evaluated with observed in-stream total Hg. Our goal was to assess Hg cycling in Coastal Plain systems using concentrations and fluxes estimated by multiple watershed-scale models with distinct mathematical frameworks reflecting different system dynamics. We found that overland flow is a potentially important transport mechanism of particulate total Hg during periods when connectivity between the uplands and surface waters is maximized. Other processes (e.g., streambank erosion, sediment re-suspension) may increase particulate total Hg in the water column. Model and data results suggest that variable source area (VSA) flow and lack of rainfall interactions with surface soil horizons results in increased dissolved total Hg concentrations with precipitation events but simulated decreases in DOC concentrations. However, DOC-complexed total Hg becomes more important during baseflow conditions. Our findings point to (1) important insights and additional questions concerning Hg science and modeling at the watershed scale in a Coastal Plain setting, but also across the U.S. and globally, and (2) the current state of the science and needs for improving watershed Hg modeling.