MERCURY FLUXES TO NEW YORK LAKES INFERRED FROM LEAD-210 DATED SEDIMENT CORES

Lake-sediment records across the Northern Hemisphere show increased atmospheric deposition of anthropogenic mercury (Hg) over the last 150 years. Most of the previous studies have examined remote lakes affected by the global atmospheric Hg reservoir. We present Hg flux records from lakes in an urban/suburban setting of central New York affected also by local and regional emissions. Sediment cores were collected from the Otisco and Skaneateles lakes from the Finger Lakes region, Cross Lake, a hypereutrophic lake on the Seneca River, and Glacial Lake, a small seepage lake with a watershed that corresponds with the lake area. Dates were established by ²¹⁰Pb. The pre-anthropogenic atmospheric Hg flux of 3.0 μg m^-2 yr^-1 was estimated for Glacial Lake, which receives exclusively direct atmospheric deposition. Fluxes peaked during 1971-2001, and were 3 to 31.6 times greater than pre-industrial deposition. The sediment record from Otisco and Cross lakes showed enhanced sediment loads due to land use change, and soil retention and evasion that likely affected Hg deposition. Skaneateles and Glacial lakes have low sediment accumulation rates, and are excellent indicators for atmospheric Hg deposition. In these lakes, we found strong correlations with emission records for the Great Lakes region that peaked following the WWII and in the early 1970s. Modern declines in sediment Hg deposition are evident in three of the four lakes, consistent with nation-wide industrial emission controls in recent decades. However a new local source could be responsible for an increase in sediment Hg deposition in Glacial Lake since the early 1990s.