INVESTIGATION OF LEAD ISOTOPES AND TRACE METAL FLUXES AS PARTICULATE CONTAMINANT TRACERS AND CHRONOSTRATIGRAPHIC MARKERS FOR LAKE SEDIMENTS IN NORTHEASTERN PENNSYLVANIA

Lead (Pb) is an environmental contaminant known to be detrimental to human and ecosystem health. Human activity has been a source of Pb to the environment for millennia, but since the advent of the industrial revolution mining and smelting, fossil fuel combustion, and waste disposal have become dominant sources of Pb in the environment. Pb is distributed throughout the environment mainly by atmospheric transport, which allows anthropogenic Pb pollution to be carried great distances and deposited far from its source. Isotopic study of Pb in sedimentary archives, especially lacustrine sediments, is useful in discerning changes in the sources of Pb and other particulate pollution over time. Here, we use measurements of Pb isotopes and trace metal fluxes to develop a chronology of historical particulate pollution sources to two glacial lakes in northeastern Pennsylvania: Lake Lacawac (Wayne County) and Lake Giles (Pike County). Several potential historical sources of Pb to these lakes are regional combustion of leaded gasoline, regional and local smelting of Pb ores, and local coal combustion associated with activity from iron forges and furnaces. In addition, we assess the use of Pb isotopes as chronostratigraphic markers in sediment records from each lake. In particular, we investigate whether these lakes preserve Pb isotopic shifts consistent with the proliferation of leaded gasoline in the early 1930s and with the smelting of highly-radiogenic Pb-Zn ores from the Upper Mississippi Valley (UMV) at ~1850.