SOURCES OF POLYCYCLIC AROMATIC-HYDROCARBONS TO LAKE-MICHIGAN DETERMINED FROM SEDIMENTARY RECORDS

Four sediment cores from Lake Michigan were Pb-210 and Cs-137 dated and analyzed for 12 polycyclic aromatic hydrocarbons (PAHs). Sources of PAHs were determined based on multiple linear regression of U.S. energy consumption figures for coal, petroleum, and wood. Profiles of PAH fluxes in sediments with mixing were reconstructed with the inverse Berger-Heath model. PAHs generated from wood burning amount to 4.6-9.3 ng/cm2 per 10(15) Btu independent of location. For coal, the significance as an input source decreases slowly with increased distance from shore, and quickly for petroleum. Maxima in the PAH records were observed corresponding to 1985, reflecting petroleum-derived PAHs as shown by the BghiP/IP ratio of 2.18 +/- 0.37 and the similarity of the historical record to petroleum consumption data, and to the mid-1960s, which may be caused by a maximum in coke production in addition to a switch in home heating from coal to oil and gas.