Previous work by Kannan et al. (2005) on sediment cores from inland lakes in Michigan have identified that with the use of indicator PAH compounds, major PAH sources of loading can be interpreted. In the study by Kannan et al. (2005) a major source of PAH emissions dominated the period 1940 to 1980, after the 1980s the influence of this source lessened. The underlying hypothesis in this study is that PAH loadings will be highest during the time period 1940 to 1980 (peak emission period) dominated by a common regional source. Post 1980, loadings will decrease. If the hypothesis is true, then, during peak emissions (1940-1980) a peak should be evident in PAH concentration profiles, PAH loading patterns should be highest in the south and lowest in the north, and PAH fingerprints amongst the lakes should be similar indicating a regional signal; and post 1980s PAH fingerprints amongst the lakes should be dissimilar indicating local watershed influences. The results were not consistent with the hypothesis, though some loading patterns were observed. Expected PAH fingerprints from cluster analysis were found to be dissimilar in all time periods. PAH concentrations were unexpectedly found to be increasing in some lakes in the recent, indicating a new source of PAH loadings despite environmental legislation; leading to a question as to what is the cause(s) of this unexpected increase. Specifically the hypothesis tested is that this recent increase in PAH loadings is related or attributable to the use of coal tar sealants, based on a hypothesis offered by Van Metre and Mahler (2010). The results were found to be inconsistent with this hypothesis, as sourcing methods did not indicate coal tar sealants as a viable source at this time.
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