Occurrence, sources, and risk assessment of OCPs in surface sediments from urban, rural, and reclamation-affected rivers of the Pearl River Delta, China

Sediments were collected to a depth of 20 cm from urban, rural, and reclamation-affected rivers in the Pearl River Delta of China. In total, 16 organochlorine pesticides (OCPs) were analyzed in all sediment samples, and the occurrence, possible sources, toxicity, and health risks of OCPs were evaluated to compare the contamination characteristics of OCPs in sediments among the three types of rivers. The results showed that concentrations of Sigma 16OCPs in sediments from the three rivers followed the order urban river > reclamation-affected river > rural river, with a mean value of 247.21, 232.91, and 114.92 mu g/kg, respectively, and the predominant OCPs were hexachlorobenzene (HCB), dieldrin, aldrin, endrin, and hexachlorocyclohexanes (HCHs). Source diagnostics illustrated that there might be recent input of HCHs, dichlorodiphenyltrichlo-roethanes (DDTs), and endosulfan in some sampling sites. Based on the soil quality thresholds of China, both HCHs and DDTs fell within the range of class II criteria except for some sediment samples in urban rivers with lower levels (below class I criteria). According to sediment quality guidelines, 92.86 % of samples were predicted to be toxic. The health risk assessment showed that OCPs would not pose a threat to people via dermal contact, ingestion, and inhalation, and the followed order of incremental lifetime cancer risks for OCPs in sediment samples was reclamation-affected river > urban river > rural river.