HISTORICAL CHANGES IN MERCURY FLUXES TO SIX NEW YORK FINGER LAKES

Much of the mercury (Hg) contamination in lake ecosystems originates from coal-fired power plants. We determined historic changes in total mercury (Hg) loading using ²¹⁰Pb- and ¹³⁷Cs-dated sediment box cores from six Finger Lakes in central-western NY: Conesus, Honeoye, Canandaigua, Seneca, Cayuga, and Owasco. We selected these lakes for study to characterize how the proximity to coal-fired power plants impacts Hg-loading. Two of these lakes have a coal-fired power plants located on their shores, Seneca Lake and Cayuga Lake. Owasco Lake is located downwind from both these plants, and the remaining three lakes are located upwind of both these power plants. As expected, both Seneca Lake and Cayuga Lake, located nearest to Hg-emitting facilities, had the highest focus-corrected Hg fluxes and lakes located farther from Hg-emitting facilities had the lowest Hg fluxes. As a result, a clear spatial gradient of Hg loading occurs across the region.

The timing of the peak in Hg fluxes to most of these lakes is coincident with maximum atmospheric emissions in the Great Lakes region during the 1940-1970s, suggesting Hg fluxes were primarily controlled by atmospheric emissions. The similarity in pattern emphasizes that these lakes are likely receiving their Hg flux from similar atmospheric sources, and that the watershed influence did not mask the atmospheric signature. Declines in Hg deposition over the last several decades are evident in most lakes, which is consistent with recent nationwide industrial emission controls. The peak in the Hg flux to Seneca Lake predates that of the other Finger Lakes as well as other regional lakes. The timing of the Hg peak in Seneca Lake occurs after the gold and silver mining boom and before the major industrial boom after World War II. We attribute the high Hg flux in Seneca Lake to coal combustion in homes and commercial buildings in New York State during the late 1800s and early to mid-1900s.