Distribution characteristics of organochlorine pesticides in water and surface sediments from the rivers of Nanning City

Residues of seven trace organochlorine pesticides(OCPs) in water and surface sediments from five rivers of Nanning City were determined with gas chromatography/electron capture detector(GC/ECD), and the samples were treated with improved solid phase extraction(SPE) and accelerated solvent extraction(ASE). The results indicated that HCHs were the dominant organochlorine components in the water, with concentrations ranging from nd to 0.141 mu g/L. The total concentration of OCPs in the surface sediments ranged from 2.13 to 2.80 mu g /kg in the five designated sampling sites. 4, 4'-DDE and 4, 4'-DDD were detected in all the sediment samples. The ratio of omega (DDD)/ omega (DDE) was lower than 1. In general, the concentrations of DDTs were higher than those of HCHs. However, all concentrations of OCPs were lower than the Consensus-based Threshold Concentration formulated by the United States Environmental Protection Agency.