Distribution and characterization of polychlorinated biphenyl congeners in soil and sediments from a superfund site contaminated with Aroclor 1268

The use of Aroclor 1268 at a former chlor-alkali plant in coastal Georgia (United States) has resulted in extensive contamination of soils on-site and also of sediments in the adjacent brackish marsh. The concentrations of total polychlorinated biphenyls (PCBs) in soil and marsh sediments ranged between 9.6 and 567 mu g/g dry wt. A nearly 100-fold decline in total PCBs with distance away from the site suggests a high attenuation of PCBs by the marsh environment. Isomer-specific analysis of PCBs in Aroclor 1268 and in soils and sediments from the site revealed that a comparable proportion of octa- and nonachlorobiphenyl congeners, characteristic of the source, were present. The distribution of PCBs in marsh sediments was similar to that in Aroclor 1268, which suggests a high degree of stability of this PCB formulation in this environment. The estimated 2,3,7,8-TCDD equivalents of coplanar PCBs in soil and sediments were between 1.6 and 28.6 ng/g dry wt and also declined by 2 orders of magnitude along the contamination gradient; the non-ortho congener, IUPAC No. 126, contributed greater than 50% of the toxic equivalents in these samples.