Persistent organochlorine residues in sediments from Chinese river/estuary systems

Persistent organochlorine compounds were analyzed in surficial sediment samples from seven large Chinese river/estuary systems. The reported concentrations of organochlorine compounds in sediments collected from Zhujiang, Minjiang and Jiulongjiang were also presented for comparison. Concentrations of HCH were low in most sediments except the Zhujiang River, where the concentrations were one order of magnitude higher than for the other rivers. The levels of DDT were relatively low in sediments from north Chinese river/estuary systems while the values of DDT were high in South China. Higher concentrations of polychlorinated biphenyls (PCBs) were observed at Huangpujiang, Qiantangjiang and Changjiang, which drain highly industrialized and densely populated areas of China. Compared with the world's other river/estuary systems, the residue levels in these sediments were relatively low, though the production and usage of organochlorines in China is in large quantities. Great water discharge and/or sediment loads and biogeochemical processes such as biodegradation, volatilization, etc., may be responsible for low concentrations.