Polychlorinated biphenyl congeners in sediment cores from the Upper Mississippi River

摘要

We determined polychlorinated biphenyls (PCBs) and radionuclide ¹³⁷Cs in sediment cores from the Upper Mississippi River (UMR) and the Iowa River, Iowa, at their confluence. Vertical distribution of ¹³⁷Cs indicated negligible mixing in the UMR core, while the Iowa River core showed signs of mixing. A clear ¹³⁷Cs peak was found in the UMR core, which was correlated to 1963. The PCB vertical distribution in UMR core was similar to the historical trend in Aroclor production observed in Great Lakes cores, with a peak close to the ¹³⁷Cs peak, suggesting a date near 1960. In general, PCB congener profiles in both cores resembled the Iowa soil background signal. We concluded that despite evidence of mixing in the Iowa River core, both cores retain the PCB signature of historical and regional environmental exposure. Further, our results indicate that this iconic waterway has a long history of PCBs that reflects national production and use.