CHLORIDE HYDROGEOCHEMISTRY OF THE FINGER LAKES, NY

The chloride hydrogeochemistry of the eight eastern Finger Lakes in central New York: Honeoye, Canandaigua, Keuka, Seneca, Cayuga, Owasco, Skaneateles and Otisco, was investigated to discern likely sources. Previously, Wing et al. (1995) and Halfman et al. (2006) hypothesized groundwater sources for chloride in Seneca Lake based on equilibrium chloride budgets of measured inputs and outputs, and the bedrock floor intersecting Silurian-age evaporites underlying these basins. Subsequently, Jolly (2005, 2012) and Halfman (2014) refuted this hypothesis based on a century of historical data (Jolly, 2023), and subsequent monitoring of these lakes and ion chromatography analyses of surface and bottom water samples from 2006 through 2014 (Halfman, 2014).

We present surface and bottom water chloride analyses by titration (LaMotte field kits) and PerfectION Cl- combination ion probe collected from 2014 through 2022. We also modeled chloride inputs to each lake to attain the timing and extent of the observed changes in chloride concentrations using Stella. The models incorporated water retention times, historical stream inputs, road densities, measured chloride diffusion rates from the sediments, and permitted salt mine wastes from salt mines in the Seneca and Cayuga watersheds. Titration and PerfectION analyses from duplicate water samples compared favorably, i.e., within the analytical precision/accuracy of the techniques. All the lakes with historical data started below 10 ppm about 100 years ago, subsequent chloride concentration patterns divide the lakes into two camps: Camp 1: Seneca and Cayuga Lakes that are near or have recently approached steady state concentrations at 120 and 60 ppm after a 1960’s 200 and 140 ppm peak in chloride concentrations. The peak is presumably due to mid-20^th century mine waste disposal issues in both watersheds. Camp 2: The other Finger Lakes that reveal recent increases in chloride concentrations over the past few decades up to 60 ppm most likely due to increased road salt use in their watersheds. The road salt impact on our nations waterways has been observed in many other locations across the US.