MAJOR CATIONS AND ANIONS IN NATURAL WATERS IN THE NORTHWEST LAKE CHAMPLAIN BASIN, NEW YORK STATE

The purpose of this study was to determine the major surface and groundwater types in six watersheds in the northwestern region of the Lake Champlain Basin (Great Chazy River, Little Chazy River, Saranac River, Salmon River, Little Ausable River, and Ausable River). Water types were identified using Piper Plots of relative concentrations of dissolved cations (Ca, Mg, Na, and K), anions (SO₄, Cl, and NO₃), and alkalinity (CO₂, HCO₃, and CO₃). The dominant bedrocks in the study area are sandstone and anorthosite. Surface water samples were collected from over forty different locations, ranging from major streams, 1st and 2nd order streams, and lakes. Groundwater samples were collected from seven wells within two of the watersheds. When each sample was collected, we measured the specific conductivity, pH, and water temperature. In the field, each water sample was separated and stored in 30mL and 60mL HDPE sample bottles for cation and anion analyses respectively. Cation samples were field filtered (0.2µM) and acidified. Cations were measured using a Perkin-Elmer 3030B Atomic Absorption Spectrophotometer. Anions were measured using a Dionex DX-500 Ion Chromatograph/HPLC. Alkalinity was measured using a Gran Plot titration. In most water samples, concentrations of cations and anions were very low. Specific conductivities were typically less than 50µS/cm. The low concentrations and specific conductivities suggest either few cations and anions are leached from the bedrock to the water or the waters were diluted. Despite the low concentrations, from the Piper Plots we identified two distinct end-member waters: calcium/bicarbonate and sodium-potassium/chloride. Most of the other water samples plotted along a single mixing line between the two end-member waters. These results suggest that in this region there are only two distinct water types. We are using GIS layers of bedrock and surficial geology to compare water chemistry to watershed geology.