Sorption of Polychlorobiphenyl (PCB) Congeners by Residual PCB‐Oil Phases in Soils

Abstract

AbstractIn this report we show that residual polychlorobiphenyl (PCB) oil present in soils heavily contaminated with PCB mixtures (Aroclors) functions as a highly effective partitioning medium accounting for the sorptive uptake of 2‐chlorobiphenyl from water. A PCB‐oil normalized partition coefficient (KPCB) was evaluated from the experimental sorption data of 2‐chlorobiphenyl onto four PCB‐oil contaminated soils which had PCB‐oil contents ranging from 2.17 g/kg to 7.67 g/kg (2170 ppm‐7670 ppm). This KPCB value (114 000) indicates that the residual PCB‐oil phase in soils, as a partitioning medium for 2‐chlorobiphenyl, is approximately 67 times more effective per unit mass than natural soil organic matter (KOM = 1700) and 3.5 times more effective than octanol (KOW = 32 400). Our results suggest a threshold PCB concentration in soil of about 0.1% (w/w), above which the PCB mixture forms a separate sorptive phase. The threshold concentration may correspond to the solubility of the liquid PCB mixture in natural soil organic matter. Because of its greater surptive effectiveness, the PCB‐oil phase, once formed, will primarily determine the soil‐water distribution of individual PCB congeners. Accurate prediction of the soil‐water distribution of PCB congeners in such soils can be obtained by considering the additive sorptive effects of the anthropogenic and natural organic matter phases.