Organochlorine pesticides and polybrominated diphenyl ethers in irrigated soils of Beijing, China: levels, inventory and fate.

Limited information on the levels, inventory and fate of Organochlorine pesticides (OCPs) and Polybrominated diphenyl ethers (PBDEs) in the soils irrigated by sewage or wastewater is available. In this study, variation in concentrations, profiles and fate of OCPs and PBDEs were investigated using soil samples collected from a region irrigated by sewage, mixed water and clean water in the east of Beijing, China. No significant variation was observed among groups, except for penta-BDEs. The measured SigmaOCPs and SigmaPBDEs residues ranged from 6.4 to 171.2 ng g(-1) (dw) and 501.9 to 3310.7 pg g(-1) (dw), respectively. SigmaDDTs and BDE-209 were the most abundant congeners accounting for about 76% of SigmaOCPs and 93% of SigmaPBDEs. Concentrations of hexachlorocyclohexanes (HCHs), dichlorodiphenyltrichloroethane (DDTs) and its major degradation products, and hexachlorobenzene (HCB) ranged from 1.2 to 11.4 ng g(-1) (dw), 4.0 to 155.6 ng g(-1) (dw) and 0.3 to 3.4 ng g(-1) (dw), respectively. The major DDT degradation products were p,p'-DDT and p,p'-DDE. The major hexachlorocyclohexane (HCH) isomer in irrigated soils is beta-HCH, reflecting its higher affinity to solids and resistance to degradation than other isomers. Both alpha-HCH/beta-HCH and p,p'-DDT/p,p'-DDE ratios were log-normally distributed and negatively correlated to log(SigmaHCHs) and log(SigmaDDTs), respectively, suggesting no significant recent application of OCPs. Individual BDE congeners, SigmaPBDEs and SigmaOCPs were significantly correlated with total organic carbon (TOC). Moreover, a good correlationship between SigmaPBDEs and black carbon (BC) was obtained but not between SigmaOCPs and BC. Sewage irrigation did not have obvious effect on their contaminant levels and inventory of OCPs and PBDEs.