ANALYSIS OF LANDSCAPE RECOVERY FROM HISTORIC PCB LOADINGS USING SEDIMENT-CHEMICAL CHRONOLOGIES

Previous studies have shown that atmospheric transport is the dominant pathway for PCB loadings to the environment and that urban areas can be major sources. PCB loadings have been previously reported to be higher in the southern parts of the Great Lake region and lower in the north, possibly reflecting population density or concentrations of urban land use. A significant segment of the existing research to date in the Great Lakes region mainly involves the Great Lakes. These water bodies occupy an enormous footprint on the North American continent and results on PCB studies here are reflective of a coarse regional signal of PCB distribution. More detailed understanding of loading patterns is needed for a more complete understanding of sources of PCBs and the current state of environmental recovery. In this study, sediment records from 44 inland lakes across Michigan were studied to better understand the spatial distribution and changes over time of PCBs. 210Pb dated PCB concentrations from each lake were compared to GIS-determined watershed land-use characteristics. Results show regional patterns to be emerging as a more significant segment of recent PCB distribution most notably, in the Upper Peninsula. However, several locations appear to have these regional loadings supplemented with localized environmental cycling of PCBs at the watershed scale. Overall, inventories were elevated in the Lower Peninsula compared to the Upper Peninsula and locations of high PCB inventories near urban areas were found. Results were also subject to cluster analysis via Jump 5.0 software. During high PCB production years (1970s), the concentration and congener cluster show clear localized patterns, but more recently, concentrations and congener distributions suggest a return to a more regional signal. This indicates that during high PCB production years, the distribution of PCBs was more controlled by local sources and in current years, it’s more dominant by regional atmospheric input.