Documenting the Anthropogenic Impact on Ballston Lake New York from a short core using stable isotopes of carbon and nitrogen …

Documenting the Anthropogenic Impact on Ballston Lake New York from a short core using stable isotopes of carbon and nitrogen and trace metals

Geology

LaBrecque, Taylor S.

Gillikin, David

6/1/2012

Ballston Lake occupies a portion of an avulsed channel of the Mohawk River between Schenectady and Saratoga Springs, New York. The lake is about 5 km long, generally less than 200m wide, ~8-15m deep, dimictic, with a catchment basin area of ~22km2. Long cores (>8 m) indicate that the lake formed ~13,000 cal yr BP. This study was undertaken to document recent environmental change recorded in the upper portion of sediment in Ballston Lake. Three sediment cores ~40 cm long were acquired from ~8 m water depth at the north end of Ballston Lake (42°57.101'N, 73°51.066'W), and were analyzed for exchangeable metals, magnetic susceptibility, total organic carbon (TOC), total inorganic carbon (TIC), organic carbon to nitrogen ratios (C/N), and stable isotopes of carbon and nitrogen. An age model of the cores was established by correlating a prominent increase in Pb (1882 AD) and the Pb maximum (1970) based on 210Pb dating of cores from nearby lakes (Round Pond and Long Pond). Cu and Zn reflect similar increasing trends at this time, and these increases are likely attributed to industrialization and the burning of fossil fuels throughout the 20th century. ?13C values become more negative through time, declining from -29 to -30.5‰, suggesting the organic carbon is more aquatically derived. Percent TOC increases towards the surface of the core demonstrating increased productivity that is unrelated to nitrogen input, as %N and ?15N values are relatively constant. Though the data suggests that development around Ballston Lake has had only a minor impact on productivity and pollution, there are apparent changes that occurred in the lake between AD ~1970 and 1981. The increase in TIC and decrease in TOC, ?13C values, and grey scale values suggest there was an increase in clastic sediment input into the lake and reduction in terrestrial organic matter input. This event could be caused by the severe drought in New England that occurred in the 1960s, killing vegetation and weakening the erodible surfaces. Ballston Lake should be monitored for anthropogenic pollution in the future, though there has been little anthropogenic impact at this point in time.

thesis

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