A GEOCHEMICAL INVESTIGATION OF BOG/LAKE INTERACTIONS IN THE BELGRADE LAKES WATERSHED, CENTRAL MAINE

Public concern over water quality has prompted us to investigate the hydrogeology and geochemistry of the Belgrade Lakes, a system of seven interconnected lakes in central Maine. North Bay is a shallow bay in the northeastern corner of Great Pond (one of the Belgrade Lakes). It is bordered on three sides by Great Bog, and on the fourth, by open water. Because shoreline water chemistry is an indicator of the extent of groundwater interaction between lakes and peripheral wetlands, we have investigated the surface water chemistry of North Bay in order to examine groundwater interactions between Great Bog and North Bay. Water was sampled at 17 sites along the shore of North Bay. Each sample was analyzed for temperature, pH, conductivity, oxidation-reduction potential, dissolved oxygen (DO), alkalinity, and cation concentration. Most of the sites have very similar chemical signatures, with pH between 6 and 7, conductivity between 46 and 52 mS, dissolved oxygen between 84% and 95% saturation, ORP between 200 and 250 mV, and alkalinity between 0.25 and 0.35 meq/L. Cation concentrations were low, with an average total cation concentration of 5.78 ppm, with little spatial variability. Sites 8 and 12 have significantly different chemistry (especially field measurements) with pH of 4.11 and 4.93, DO 66.7% and 82.3%, and alkalinities of 0.05 and 0.15 meq/L. These two sites are in inlets where bog vegetation is encroaching on open water. We will present a documentation of and correlation between lake chemistry and shoreline vegetation that allows us to qualitatively map groundwater influxes.