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Chemistry
Completed Project

A Depositional History of Lead in Ombrotrophic Catskill Bogs

Hailey Steichen, Vassar College ’17, Natasha Vargo, Vassar College ’17 and Prof. Alison Spodek Keimowitz
Lead is a heavy metal naturally present in the earth’s crust. However, anthropogenic activities such as the burning of fossil fuels increase lead concentrations in the atmosphere; from there lead may be deposited on surface environments, where it becomes accessible to the biosphere. Plants and animals can absorb this lead, which can have carcinogenic and neurotoxic effects. One way to observe the depositional history of lead is to analyze peat cores formed in ombrotrophic (rain-fed) bogs. These bogs serve as excellent depositional archives because they eliminate the possibility that the lead was deposited by water sources besides precipitation. Additionally, the acidity of the bog and the chemical stability of lead allow it to remain in the layer in which it was originally deposited. Previous research, mainly in Europe, has shown that layers of peat with high lead concentrations correspond to time periods when lead was prevalent in the atmosphere, such as during the peak of leaded gasoline usage in the 1960’s and 70’s. Our study examines the depositional history of lead in ombrotrophic bogs in the Catskill Mountains, a region where such depositional trends are unstudied. We obtained cores from six bogs throughout the Catskills, sectioned them, dried and homogenized the samples, then analyzed their lead content through x-ray fluorescence (XRF). Our data suggest that there tends to be a peak in lead concentration in the upper middle of cores with the highest concentration being 110.2 mg/kg at a depth of 9cm in core 1 from bog 372. In this core, the concentration steadily decreases to 0 mg/kg in the most recent layer, and eventually decreases to 0 mg/kg at the oldest depth of 29cm. We will date several points in each core to create a depositional timeline that could link the recent decrease in lead deposition to environmental actions such as the Clean Air Act. This will also allow comparisons between different Catskills sites, and with sites outside this region.