CONTROLS ON METHYLMERCURY PRODUCTION IN TWO CONNECTICUT RIVER EMBAYMENTS

Methylmercury is a neurotoxic that bioaccumulates within ecosystems. This project focuses on the controls on the production of methylmercury in two Connecticut River embayments, the Oxbow Lake, Northampton, MA and Hamburg Cove, Lyme, CT. Each site receives riverine input from both streams and the Connecticut. Hamburg Cove is tidally influenced and experiences occasional salt water intrusions. Sediment cores and pore water samples have been taken from both embayments for geochemical characterization. Preliminary porewater results indicate that Hamburg Cove has a higher sulfate concentration with values reaching ~13 mg/l, while the Oxbow has a higher iron porewater concentration reaching ~100 mg/l. Initial data from LOI indicate that both cores have a high organic content (~7-12%). Organic content has been linked to higher retention of inorganic mercury in sediments. Indeed, preliminary sediment mercury analyses from cores indicate high mercury values with peak concentrations for the Oxbow of ~500 ppb and for Hamburg Cove at ~2500 ppb. Although sediments contain inorganic mercury, studies have shown that in anoxic sediments iron reducing bacteria and sulfate reducing bacteria are able to methylate mercury. High iron and sulfate values in the pore water suggests that these processes may be occurring. Sediment methylmercury concentrations will be correlated with the porewater geochemistry to better quantify the production of methylmercury.