HG(T) CONCENTRATIONS IN SOILS AND STREAM SEDIMENTS IN CENTRAL INDIANA

An investigation of Hg_(T)concentrations in soils and stream sediments has been conducted to better understand the impact of urbanization on the upper west fork of the White River watershed located in central Indiana. The study sites included Marion, Hendricks, and portions of Morgan, Hamilton, and Owen counties. Marion County has Hg_(T) emitters such as power plants, smelters, and foundries. The sampling approach for soils was designed to capture regional atmospheric deposition patterns and is one of the first attempts at doing this that we are aware of. Central Indiana's primary wind pattern (SW to NE) plus emissions data was used to follow emission plumes to better understand the anthropogenic influences on Hg_(T) distribution in soil. Stream sediment sampling was designed to understand the riverine particulate transport of Hg through a major metropolitan and industrial center (Indianapolis) and to predict the potential for stream sediments with high Hg _(T)contents along certain stretches of the river to become significant sources of methyl-Hg. The White River flows through urban and rural areas and has features such as dams, other impoundments, CSO's, WWTP, and other industry that may contribute to the variability in stream sediment concentrations within the study site.

Results show a pattern of Hg soil enrichment distributed from the downtown industrial sites toward the northeast, roughly following that predicted from local emission sources and prevalent wind directions. These results indicate that local sources for Hg deposition cannot be overlooked in managing Hg emission controls. Results from the stream sediment survey show Hg_(T) increasing from northern rural sample sites downstream to urban sites. Hg_(T) concentrations were even more elevated as the White River flowed through downtown Indianapolis where most the industry is located. WWTP and CSO's also contribute to Hg_(T) concentration in the immediate area of output. These results also show very high stream sediment Hg concentrations 10's of kilometers downstream of the emission sources in Indianapolis, indicating the potential for Hg fisheries hazards far from emission sources.