[Distribution of organochlorine pesticides in surface sediments from the middle and lower reaches of the Yellow River].

Organochlorine pesticides (OCPs) in twenty-three sediment samples from the middle and lower reaches of the Yellow River were analyzed by GC-ECD. The OCPs detected were comprised mainly of HCHs, DDTs, hexachlorobenzene, chlordane, etc. The range of total OCPs concentration was 0.35 - 22.92 ng/g. The concentrations of HCHs and DDTs were much higher than other compounds and varied from 0.05 - 5.03 ng/g and 0.09 - 12.88 ng/g, respectively. Contamination level of OCPs in sediment increased from middle to lower reaches along the Yellow River. The distribution of total OCPs in main tributaries followed the sequence: Xinmang River > Jindi River > Si River > Yiluo River > Qin River. The Yellow River had a much higher concentration of HCHs than Hai River, the Pearl River, the Yangtze River and Huangpu River, and almost the same concentration of DDTs as other rivers except Hai River. The contamination of OCPs in the sediments from the middle and lower reaches of the Yellow River derived mainly from industrial contamination in riverbasim, the inflow of the main tributaries and the residues of organochlorine pesticides widely used for a long-term and the aged and weathered agricultural soils.