Comparison of Methylmercury Production and Accumulation in Sediments of the Congaree and Edisto River Basins, South Carolina, 2004-06. Toxic Substances Hydrology Program and National Water-Quality Assessment Program

摘要

Fish-tissue mercury concentrations (approximately 2 micrograms per gram) in the Edisto River basin of South Carolina are among the highest recorded in the United States. Substantially lower mercury concentrations (approximately 0.2 microgram per gram) are reported in fish from the adjacent (about 30 kilometer) Congaree River basin and the Congaree National Park. In contrast, concentrations of total mercury were statistically higher in sediments from the Congaree River compared with those in sediments from the Edisto River. Furthermore, no statistically significant difference was observed in concentrations of methylmercury or net methylation potential in sediments collected from various Edisto and Congaree hydrologic settings. In both systems, the net methylation potential was low (00.17 nanogram per gram per day) for in-stream sediments exposed to continuously flowing water but substantially higher (about 1.8 nanograms per gram per day) in wetland sediments exposed to standing water.