PERSISTENCE AND FATE OF POLYCHLORINATED-BIPHENYLS (PCBS) IN SEWAGE SLUDGE-AMENDED AGRICULTURAL SOILS

Four metal enriched sewage sludges containing different concentrations of polychlorinated biphenyls (PCBs) were applied to two field soils i n the UK in 1968. Samples of the sludges, sludge-amended soils and soi ls from untreated control plots were stored and analysed retrospective ly, Sludge concentrations ranged from 1 to 7 mg Sigma PCB kg(-1). The pattern of PCBs was similar in three of the four sludges, with congene rs 14, 18, 28 and 52 present at the highest concentrations, The fourth sludge contained higher amounts of congeners 149, 153, 138 and 180. S igma PCB concentrations in control plot soil have declined over the la st 20 years, indicating a reduction in atmospheric deposition inputs o f PCBs to the soil. Sigma PCB concentrations also declined on the slud ge-amended plots, reaching control plot concentrations (30-60 mu g Sig ma PCB kg(-1)) in the late-1980s, Half-lives ranged from < 1 to 8.5 ye ars for congeners 18, 28 and Sigma PCB, Biodegradation and/or the form ation of reversibly sorbed soil PCB residues could not account for the losses observed. Volatilisation is implicated as the most important l oss process on both the control and sludge-amended plots, Using the fu gacity approach, congener concentrations in soils al Luddington were p redicted still to have not reached equilibrium with the air. Further l osses to the atmosphere ave likely. Copyright (C) 1996 Elsevier Scienc e Ltd