Organochlorine pesticides in the surface water and sediments of the Pearl River Estuary, South China

Samples of surface water, suspended particulate matter (SPM), and surface sediment, collected from the Pear River Estuary, Guangdong Province, China in July of 2002 and April of 2003, were analyzed for hexachlorocyclohexanes (HCHs) and dichlorodiphenyltrichloroethanes (DDTs) using gas chromatography with electron capture detection. The levels of total HCHs in water varied from 213 to 3,116 pg/L, although in sediments they ranged from 181 to 1,388 pg/g dry weight. The levels of DDTs were in the range of 228 to 3,284 pg/L in water and 57 to 2,244 pg/g dry weight in sediments, respectively. The observed spatial and temporal variability of concentrations of the target compounds in water body could be attributed to the differences of SPM contents in water body and organic carbon contents in SPM between the two sampling periods. Seven of the 10 water samples collected in July of 2002 had the ratio of dichlorodiphenyltrichloroethane/(dichlorobischlorophenylethane + dichlorodiphenyldichloroethylene) (DDT/[DDD + DDE]) higher than one, indicating that there were likely fresh inputs of DDT to the Pear] River Estuary. The significant positive correlations between the organochlorine pesticide concentrations and organic carbon contents in SPM and sediments indicated that organic matter played an important role in controlling the distributions of these pollutants in the marine environment. Varied correlations between the partition coefficients of pollutants and total organic carbon, salinity, and total SPM contents have been observed, which indicated the influences of these factors on controlling the transport and fate of pollutants in the marine environment.