The South Carolina Clean Metals Project

Mercury exists in many different physical and chemical forms in the environment and it is the interconversions between these species that mediate its distribution patterns and biogeochemical cycling. The most widely known conversion is the biological transformation of inorganic Hg (II) to methyl Hg and its subsequent biomagnification in piscivorous fish, which poses a risk to higher trophic level organisms and humans who consume these fish. The discovery of high levels of Hg (>0.25 ppm) in fish from water bodies in South Carolina (SC) has resulted in the issuance of many fish consumption advisories throughout the state. The highest fish tissue concentrations have been found in unregulated blackwater rivers in the Southeastern Plain and the Middle Atlantic Coastal Plain ecoregions, with lower fish Hg concentrations found in the Southern Coastal Plain, Blue Ridge, and Piedmont ecoregions. Investigating the geochemical cycling of Hg in aquatic systems is a necessary precursor to understanding the mechanisms responsible for its accumulation in higher trophic levels. The SC Clean metals project was initiated in 2010 and includes 4 quarterly sampling events. The first objective of this study is to determine levels of total and methyl Hg in water and sediments from 21 sites along a geographical gradient (west-east) within SC. Sites within differing ecoregions were chosen to identify potential factors governing the spatial variability of Hg levels in water and sediment throughout the state and how they may relate to the concentration of Hg in fish tissue. A second objective of the study is to examine how the mercury levels in the water and sediment may change on a seasonal basis. The third objective of the project is to collect as small subset of samples for low level copper and zinc at 4 sites within SC. The project involves a collaboration between Coastal Carolina University, South Carolina Department of Health and Environmental Control, and Pacific Northwest National Laboratory (Marine Science Laboratory).