TRACE METALS, SOURCES AND MOVEMENT, IN PITTSBURGH LAKE SEDIMENTS

Over the past few winters, several half-meter cores have been retrieved from Panther Hollow Lake, a 100-yr-old manmade reservoir located in Pittsburgh’s Schenley Park. Extracted in the field at 0.5cm intervals, these cores were analyzed for trace metal concentrations using first an 11.1% nitric acid solution and separately by a four-step sequential extraction procedure to determine which metals were made available in each phase: weak acid, reducible, oxidizable, residual. The initial extraction showed high levels of metals that are typically found glommed onto fly ash as by-products: Pb, Al, Cu, As, Fe, and V, peaking before the inception of the clean air act and tapering off there after. Sr levels begin increasing at that point, possibly in response to scrubber regulations on local coal-fired power plants. Another batch of sediments were then sequentially extracted in preparation for a spheroidal carbonaceous particle count to quantify the ash content throughout the core. The sediments were also analyzed for magnetic susceptibility, bulk density, and loss on ignition with results indicating that the sediments are >10% organic matter. This record will be directly compared to that of the industry history of the area, providing another look at the impact of smelting. This work is currently in progress.