Residues and distributions of organochlorine pesticides in Chinas Weihe River

To exam ine the residues and distributions of hexachlorocyclohexanes (HCHs), dichlorodiphenyltrichloroethane (DDT), and other organochlorine pesticides (OCPs ) in the Weihe River basin of northwest China, a gas chromatography-mass spectrometer (GC-MS) was employed to analyze the samples collected from surface water, suspended solids, and sediments. Results showed that total concentrations of HCHs, DDT, and othe r OCPs in surface water were in the range of 2.41-178.18, 0.94-116.83, and 3.64-37.17 ng/L, respectiv ely; in suspended solids they were 5 1.76-241.23, 2.82-12.23, and 11.35-37.67 ng/L, respectively; and in sediments they were 74.13-517.49, 1.20-370.98, and 7.94-110.13 ng/g dry weight, respectively. The α-HCH/γ-HCH ratio indicated that historical usage of technical mixtures of HCHs was the main source of HCHs. The DDT ratio indicated that DDT at most sites came from older uses of technical DDT. Compared with some guideline values of OCPs in surface water, the concentrations of HCHs and DDT were at safe levels. Meanwhile, the Weihe Riv er sediments have high ecological risk pesticides.