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Development and Example Application of a Pilot Model for the Biogeochemical Cycling of Mercury in Watersheds: SERAFM-NPS
Citation:
KNIGHTES, C. D. Development and Example Application of a Pilot Model for the Biogeochemical Cycling of Mercury in Watersheds: SERAFM-NPS. U.S. Environmental Protection Agency, Washington, DC, EPA/600/R-09/114 (NTIS PB2010-104717), 2009.
Impact/Purpose:
see description
Description:
Mercury is a developmental neurotoxicant, ubiquitous in the environment, existing both naturally and through anthropogenic additions, resulting in human and ecological exposure risks primarily via consumption of mercury contaminated fish tissue. To better understand the risk associated with mercury exposure, it has become necessary to not only understand the mercury biogeochemical cycling within water bodies where typical mercury exposure occurs, but to also understand terrestrial mercury biogeochemical cycling, including mercury deposition, transformation, and transport to receiving water bodies. Here, we present a relatively straight-forward and transparent spreadsheet-based pilot model to simulate the biogeochemical cycling of mercury in watersheds. The watershed is divided into different land use types (currently impervious, forest, grassland, agriculture-pasture, agriculture-row crops, and wetlands) lumping all similar land use types into one box. This model uses a simple box-model approach, with mechanistic differential mass balance equations to describe the transformation and transport of speciated mercury (Hg(0), Hg(II), and MeHg) within each land use type, predicting soil mercury concentrations and transport processes (volatilization, erosion, leaching, runoff, and total flux to receiving water bodies). The model is dynamic, running on time steps of years, allowing for development of mercury concentrations over long time periods. The output of this model was designed to provide loading information to water body models such as SERAFM and WASP.