LEAD ISOTOPIC DETERMINATION OF HISTORICAL SOURCES OF LEAD TO LAKE ERIE, NORTH-AMERICA

Measurements of lead concentrations and stable lead isotopic compositi ons (Pb-204, Pb-206, Pb-207, Pb-208) in sediment cores from Lake Erie document both temporal and spatial variations in lead sources to the l ake. These analyses track the history of lead contamination in the lak e, as well as the transport of particulate matter which governs the re distribution of particle-reactive contaminants within the lake. The is otopic compositions of the sediments reveal two sources of natural lea d (fluvial and shoreline bluff erosion) and three primary sources of a nthropogenic lead (coal combustion, gasoline additives, and municipal waste water discharges) to the lake. Lead concentrations and isotopic compositions of Pb-210-dated sediment cores record historical variatio ns in the inputs from these sources. The heterogeneous isotopic compos ition of the three basins of Lake Erie indicates that lead from munici pal effluent is most prominent in the urbanized western region of the lake and that atmospheric deposition is most prominent in the more rur al eastern areas. Calculations based on a Pb-207/Pb-206 vs. Pb-208/Pb- 206 linear mixing model show that as much as 70% of sediment in the Ce ntral Basin and 25% in the East Basin originates from the West Basin o f Lake Erie. These calculations attest to the interbasinal redistribut ion of particle-reactive contaminants within the lake.