Polychlorinated biphenyl congeners and organochlorine insecticides in the water column and sediments of Daya Bay, China

Samples of sub-surface water, suspended particulate matter (SPM) and surfac e sediments collected from Daya Bay, China have been analysed for 12 polych lorinated biphenyl (PCB) congeners and 18 organochlorine insecticides, usin g gas chromatography electron capture detection. Total PCB levels varied fr om 91.1 to 1355.3 ng l(-1) in water and from 0.85 to 27.37 ng g(-1) dry wei ght in sediments. The levels of total organochlorine insecticides were in t he range 143.3-5104.8 ng l(-1) in water and 2.43-86.25 ng g(-1) dry weight in sediment. None of the target compounds were detected in SPM. The levels of total hexachlorocyclohexanes in water varied from 35.5 to 1228.6 ng l(-1 ), whilst in sediments they ranged from 0.32 to 4.16 ng g(-1) dry weight. F or the sum of dichlorodiphenyltrichloroethanes (DDTs), their levels were in the range 26.8-975.9 ng l(-1) in water, and 0.14-20.27 ng g(-1) dry weight in sediments. The distribution profiles of these contaminants in water and sediments suggest that there are a number of sources contributing to total contaminant burden in the bay, including soil runoffs, wastewater discharg es, sewage outfalls and shipping activities. Ratios of DDT/(DDE + DDD) in t he water and sediments indicate recent inputs of such chemicals into the ba y. The results, therefore, provide important information on the current con tamination status of a key aquacultural area in China, and point to the nee d for urgent actions to stop the use of persistent agrochemicals such as DD T and lindane. (C) 2001 Elsevier Science Ltd. All rights reserved.