ATMOSPHERIC LOADING OF POLYCYCLIC AROMATIC-HYDROCARBONS TO LAKE-MICHIGAN AS RECORDED IN THE SEDIMENTS

Five sediment cores from a north-south transect of Lake Michigan were collected using box cores deployed from the RV Lake Guardian and from a submersible (Johnson Sea Link II, RV Seward Johnson). The sediments, analyzed for PAHs (n = 28) and Pb-210 to Obtain accumulation rates an d inventories of PAHs, were used to determine the role of the atmosphe re in contaminant loading to Lake Michigan. The accumulation of PAHs i n the sediments increased dramatically around 1900, reached a plateau around 1930-1975, and decreased slightly in recent time. Surface sedim ent accumulation rates and inventories for Sigma PAHs (n = 17 parent), corrected for sediment focusing with Pb-210, equaled 50-70 ng cm(-2) yr(-1) and 5000-7000 ng cm(-2), respectively. The relative abundances of individual PAH compounds from Lake Michigan sediments, PM-10 aeroso l of Chicago, and a coke oven signature are statistically similar esta blishing a linkage between combustion sources in the south, atmospheri c deposition, and sediment accumulation. Further support for this link age is the historical PAH accumulation in lake sediments and historica l coal use in Illinois over the same time period. The major source of PAHs to Lake Michigan sediments is coke and steel production found in the urban/industrial complex around Chicago, IL, and Gary, IN. These P AHs are deposited primarily in the southern basin after which they are redistributed throughout the lake as a result of in-lake integration processes (water and sediment transport).