MODERN LIMNOLOGICAL RECORDS AND MERCURY CONTAMINATION OF CENTRAL NEW YORK LAKES

We are studying lacustrine sedimentary records to evaluate chemical changes attributed to recent human activity such as air-borne pollution, waste discharge and land-use change in the central New York area. The records are from five lakes: Otisco, Onondaga, Skaneateles, Oneida, and Cross, all located in the Seneca River watershed. The changes with depth in organic matter, nutrients, calcium carbonate, and the trace metal mercury, are recorded by analyzing 1 to 2 cm long segments from each core. The chronology is obtained using the Lead-210 dating method.

Preliminary results from Otisco Lake, a major drinking water supply since the beginning of the 20th century to Onondaga County, show major changes for the past 150 years. Since the 1870’s mercury flux increased from around 40 ug/m²/yr to a maximum value of 120 ug/m²/yr during the 1970’s. A distinctive increase in mercury flux is observed since the 1930’s. In the 1980’s the mercury flux reduced to around 90 ug/m²/yr, but rose again in the 1990’s. The top most 2 cm of the sediment core from Lake Otisco shows a significant decrease in flux to values below 80 ug/m²/yr. Nutrient flux (carbon and nitrogen) show similar trends that support a connection between changes in land use in the lake’s watershed with the mercury flux, suggesting the later is not solely a function of atmospheric deposition. The results contribute to the study of contaminants flux in the modern and pre-industrial periods and their influence on the lake’s chemistry. This study can assist in the management of these water bodies, which are used as drinking water supplies and ecological habitats.