Carbon particles in dated sediments from Lake Michigan, Green Bay, and tributaries

Carbon particle analysis is carried out of four sediment cores from Lake Michigan (CLM-I), Green Bay (GB-D), and the Fox (FR-C) and Kinnickinnic Rivers (KK-6) to explore the inputs of pollution from incomplete combustion of fossil fuels. Elemental carbon content is determined by CHN analyzer, and carbon particle type (from burning of coal, wood, and petroleum), abundance, and size are determined through scanning electron microscopy. Carbon contents are between 0 and 1.0% except for core KK-6, where high values (3-33%) appear to be linked to a now defunct coke and coal gasification plant. Maxima are found in the 1950s (CLM-I) or during 1940-1962(FR-C). The abundance of coal particles is between 40 and 95% in all four cores. The wood fraction is between 0 and 40% with the highest value in the central Lake Michigan core (CLM-I), indicating long-range transport of small diameter (18-22 mu m) wood particles with a minimum during 1960-1970 in agreement with the U.S. consumption record. The fraction of oil particles increases in the top layers of KK-6, FR-C, and CLM-I, reflecting increasing emissions from automobile traffic since 1920-1940. Core GB-D shows the opposite tend since 1953, demonstrating reduced significance of Green Bay as a commercial port. PAH data for these areas, obtained by others, generally support our results.