Evaluation of risk associated with organchlorine pesticide contaminated sediment of the Lake Lianhuan watershed.

Characteristics and risk evaluation of organchlorine pesticides (OCPs) in the sediments of four lakes located in the Lake Lianhuan area were conducted to observe the risks on ecological system and identify the sources of pollutants. Measurement of eleven OCPs, four hexachlorocyclohexane (HCH) isomers (α-HCH, β-HCH, γ-HCH, δ-HCH), three dichlorodiphenyltrichloroethane (DDT) homologues (p,p'-DDT, p,p'-DDD, p,p'-DDE), and four cyclodienes (Aldrin, Dieldrin, Endrin and Heptachlor), indicated that concentrations of OCPs, HCHs and DDTs ranged from 0.04 to 9.95, 0 to 7.40 and 0 to 2.44 ng/g, respectively. The most dominant pollutants were the HCHs, high proportions of γ-HCH isomer indicating the recent input of lindane. The ratios of α-HCH/γ-HCH of four lakes are all lower than that in technical HCH mixtures indicated that there was input of lindane in the past several years, or that significant α-HCH evaporation into the atmosphere occurred. The ratios of (p,p'-DDE + p,p'-DDD)/p,p'-DDT in four sediments are all <1, and the mean ratios of (DDE + DDD)/∑DDT are all <0.5, suggesting recent DDT compounds input. The risk assessment was based on ERL and ERM values obtained by the approach used for assessment of ocean risk. The results suggest that OCPs in sediments of the Lake Lianhuan system poses a potential hazard to human health and environment.