INFERRING REGIONAL AND LOCAL SOURCES OF MERCURY TO THE SEDIMENTS OF SENECA LAKE, NEW YORK

Mercury contamination is pervasive in aquatic ecosystems and its bioaccumulation may lead to severe health concerns for both wildlife and humans. Both local point sources and regional atmospheric fallout are historically important. Here we present mercury concentrations within the top two centimeters of sediment in Seneca Lake in central New York State to investigate the concentration of mercury in the sediments and the relative significance of local and regional atmospheric fallout. AES Greenidge, a coal-fired electrical generation station, is located along the western shore of the lake and has been in operation since 1939.

Eleven sediment grab samples were collected in September and October 2008 along a ~20-km transect extending from just south of the coal plant northward to examine the current impact of the power plant. The mercury concentrations reveal no gradient with distance from the power plant within Seneca Lake. The mercury concentrations range from 0.034 to 0.150 ppm (average = 0.127 ppm) in Seneca Lake. In other central NY lakes, concentrations up to 0.07 ppm were reported where the only expected source of mercury is regional atmospheric fallout and up to 0.16 ppm where additional local sources were suspected. The average concentration in Seneca Lake is at the high end of this range, suggesting both regional and local sources. Mercury concentrations increased with decreasing sediment grain size and with deeper water depths in Seneca Lake. This trend was observed in neighboring Finger Lakes and was explained by sediment focusing of fine-grained sediment and adsorbed mercury to deeper sections of the lake (Bookman et al, 2008). Sedimentation rate and porosity data are not available to calculate mercury fluxes to the sediments of Lake Seneca and to substantiate both conclusions.