PCB MOVEMENT, DECHLORINATION, AND DETOXICATION IN THE ACUSHNET ESTUARY

Congener‐specific analyses of the PCBs in Acushnet Estuary (New Bedford, MA) sediments and waters were undertaken to identify the PCB alteration and transport processes occurring in coastal marine sediments. These analyses indicated that (a) the PCBs deposited at the sediment sites sampled had originally consisted of Aroclors 1242 and 1254, in widely varying proportions; (b) these PCBs had undergone vertical movement within the sediments, rather than remaining stratified, but not horizontal translocation between sites; (c) they had also undergone extraction into the water, albeit at declining rates, with some consequent changes in composition but (d) the major compositional change was caused by a previously unreported type of reductive dechlorination process, designated Process H. This presumably anaerobic microbial process, subsequently identified at several other locations as well, had selectively removed non‐ortho chlorines from most of the higher PCB congeners, especially those associated with acute toxic effects. It appeared to have begun near the upper end of the estuary and not yet reached its lower portions, thus providing a marker for tracing the origin of the PCBs in estuarine water samples. Copyright © 1990 SETAC