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 in the UK in 1968. Samples of the sludges, sludge-amended soils and soils from untreated control plots were stored and analysed retrospectively, 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 congeners 14, 18, 28 and 52 present at the highest concentrations, The fourth sludge contained higher amounts of congeners 149, 153, 138 and 180. Sigma PCB concentrations in control plot soil have declined over the last 20 years, indicating a reduction in atmospheric deposition inputs of PCBs to the soil. Sigma PCB concentrations also declined on the sludge-amended plots, reaching control plot concentrations (30-60 mu g Sigma PCB kg(-1)) in the late-1980s, Half-lives ranged from < 1 to 8.5 years for congeners 18, 28 and Sigma PCB, Biodegradation and/or the formation of reversibly sorbed soil PCB residues could not account for the losses observed. Volatilisation is implicated as the most important loss process on both the control and sludge-amended plots, Using the fugacity approach, congener concentrations in soils al Luddington were predicted still to have not reached equilibrium with the air. Further losses to the atmosphere ave likely. Copyright (C) 1996 Elsevier Science Ltd