Organochlorine pesticides in soils around watersheds of Beijing reservoirs: a case study in Guanting and Miyun Reservoirs.

A systematic survey of organochlorine pesticides (OCPs) residues in soils around reservoirs that supply water to Beijing, China, has been lacking. 104 representative surface soil samples were collected around Guanting Reservoir (GTR) and Miyun Reservoir (MYR) in Beijing watershed to characterize concentrations and sources of organochlorine pesticides, hexachlorocyclohexane (HCH) and dichlorodiphenyltrichloroethane (DDT). Compared with other studies of OCPs in soils and with the Chinese environmental quality standard for soil, the concentrations of OCP were relatively lower in soils around the watershed. The results indicated that past agricultural application of OCPs was the major source of OCP residues in the watershed.