NONCONSTANT POLYCHLORINATED BIPHENYL PARTITIONING IN NEW-BEDFORD HARBOR SEDIMENT DURING SEQUENTIAL BATCH LEACHING

Leaching of PCB-contaminated sediment from the New Bedford Harbor Superfund Site, New Bedford, MA, was conducted to assess the long-term mobilization of PCB. Sequential batch extraction of the sediment with distilled-deionized water resulted in a progressive increase in concentrations of PCB, dissolved organic carbon, and numbers of microorganisms in the extract. Sequential extraction with saline water produced extractant PCB concentrations that were relatively constant and significantly lower than those obtained with distilled-deionized water. The PCB mobilization pattern in distilled-deionized water extractant demonstrated dependence of PCB partitioning on ionic strength (as measured by conductivity). The dependency on ionic strength was related to release of sediment organic carbon as ionic strength decreased during sequential batch extraction. The data show that organic colloids and microparticulates mobilized by changes in ionic strength significantly facilitate the release of PCBs.