EVIDENCE OF ANTHROPOGENIC IMPACT IN LAKE SEDIMENTS IN AN URBAN WATERSHED: SUMMIT LAKE, SUMMIT COUNTY, OHIO

Lake sediments can preserve a history of the impact that land use change had on both the lake and its watershed. A 210Pb-dated, 7-meter long sediment core from Summit Lake, a kettle lake in Akron, Ohio, exhibits changes in trace metal concentrations, magnetic properties, organic content, and lithology resulting from anthropogenic activity in the watershed. Below 280 cmblf, organic gyttja with low trace metal concentrations represents natural background for the Summit Lake system and was deposited during the Holocene to AD 1827. The partial drainage of the lake in 1827 and the construction of the Ohio-Erie Canal in 1832 through Summit Lake are recorded in the sediment as a change from gyttja to light brown organic mud at 280 cmblf. Canal construction corresponds to decreases in organic content and increases in mineral content as land disturbance increases sediment erosion. Between 280-242 cmblf thinly laminated sediment with increasing anthropogenic trace metal concentrations indicate the influence of the canal system on the lake. Above 242 cmblf, organic content decreases further and the anthropogenic metals Pb and Cu increase greatly, indicating onset of major industrial activity in the area at approximately AD 1850. Large increases in Zn and Cr occur higher up in the sediment, reflecting changing industrial activities. Between 242-80 cmblf, high trace metal and magnetic concentrations and low organic content reflect industrial development and urbanization associated with the growth of the city of Akron. Above 80 cmblf (AD 1972), trace metal and magnetic concentrations show a decreasing trend as a result of stricter environmental regulations and a major decline in the industrial activity in Akron. Magnetic concentration parameters and trace metal pollutants have high correlations in Summit Lake sediments. Because magnetic measurements are fast, inexpensive, and non-destructive, they provide a rapid proxy for pollution history.