A RECORD OF ANTHROPOGENIC ENVIRONMENTAL IMPACTS FROM THE SEDIMENTS OF NESMITH LAKE, OHIO

Anthropogenic environmental impacts can be assessed from lake sediments using a variety of magnetic and physical properties. A 2.68-m-long core was extracted from Nesmith Lake, Ohio and used to document anthropogenic impacts to the lake and its watershed. Down core profiles of magnetic concentration, magnetic grain size, magnetic mineralogy, dry bulk density (DBD), and organic content were divided into 4 zones. These 4 zones are interpreted in terms of changing anthropogenic activity. The Pre-settlement Zone spans 268-62 cm depth. Sediment in this zone has high organic content (~60%), low DBD and low ferrimagnetic concentration of predominately fine magnetic grain size. The Pre-settlement Zone is interpreted to reflect a forested watershed with minimal catchment erosion to the lake prior to Euro-American settlement in 1805. The Settlement Zone spans from 62-24cm depth. Sediment in this zone has low organic content (~30%), high DBD, and high ferrimagnetic concentration of predominately coarse magnetic grain size. Within this zone, there are abundant coal combustion spherules. The sediment of the Settlement Zone is interpreted to reflect greatly increased human activity in the region. In the 1830’s, the Ohio-Erie canal was built adjacent to Nesmith Lake. Railroads came to the region in the 1850’s and the region became more industrialized. The Sediment Input Zone spans 24-12 cm depth. Sediment in this zone has the lowest organic content (~14%), highest DBD and a moderate ferrimagnetic concentration of coarse magnetic grain size. The sediment of this zone is interpreted to reflect increasing sediment delivery in the lake, possibly from the Great Flood of 1913, increased housing development and the construction of a highway a few hundred meters from the lake. The Present Day Zone spans 12-0 cm depth and is characterized by low organic content (~24%), higher DBD, and declining ferrimagnetic concentration of coarse magnetic grain size. This zone is interpreted to reflect a fully developed region with residential and industrial land use. Furthermore, the passing of environmental regulations like the Clean Air and Water Acts of the 1970’s helped reduce pollution emissions to the environment and may contribute to the decline in the coarse grained ferrimagnetic concentration of the sediment.