ARE WINTER DE-ICING APPLICATIONS THE PRIMARY SOURCE OF CHLORIDE TO THE FINGER LAKES OF CENTRAL AND WESTERN NEW YORK?

The Finger Lakes of western and central New York support a rapidly expanding tourist industry and provide fresh drinking water to neighboring communities including the cities of Rochester and Syracuse. Threatening both uses are elevated dissolved chloride and sodium in Seneca Lake (~130 & 80 ppm), and to a lesser degree Cayuga Lake (50 & 25 ppm), compared to the other Finger Lakes (~20 & 10 ppm, respectively). Previous research hypothesized that the elevated chloride and sodium concentrations result from an additional saline groundwater source to Seneca and, to a lesser degree, Cayuga Lake from the underlying Paleozoic rock-salt deposits, because these two lakes are the only Finger Lakes deep enough to intersect the salt formations. However, Jolly (2005) presented historical chloride concentrations of ~30 ppm in 1900 for Seneca and Cayuga Lakes that questions a geologically constant saline groundwater source. His historical data also revealed a steady increase in chloride concentrations from 1900 to modern values by 1970. We now hypothesize that the historical chloride data reflect increased contributions of road salt, salt mining activities in the region, and a mid-century pulse of saline groundwater.

Modern and historical major ion concentration data from the Finger Lakes are presented to investigate our hypothesis. In addition to continuous sampling of the Finger Lakes, Seneca Lake, and Seneca streams, three samples were collected from the major inlets to six of the eleven Finger Lakes in June, 2006. Historical data were gathered from neighboring lakes using archived Health Department and Water Supply reports. Finally, annual salt application amounts were gathered from local highway departments in order to estimate the loading of salt into the Finger Lakes from winter de-icing practices. The data indicate that de-icing practices have raised chloride and sodium concentrations in the Finger Lakes, but eliminates de-icing as the primary source of the significantly larger chloride concentrations of Seneca Lake.