The occurrence and spatial distribution of organophosphorous pesticides in Chinese surface water.

The organophosphorous pesticides (OPPs) contaminations have been reported to occur in some Chinese waters. To describe the contamination status and the spatial distribution of OPPs in the surface water throughout China, samples were collected from over 600 sites located in the surface water of seven major river basins and three main internal rivers drainage areas during 2003 and 2004. The surface water samples were analyzed for the representative OPPs including dichlorvos, demeton, dimethoate, methyl parathion, malathion and parathion. In general, the most frequently detected compound was dichlorvos and demeton, being detected in 89.1% of samples (mean = 17.8 ng/L; range <1.4-1,552.0 ng/L) for dichlorvos, and 78.2% of samples (mean = 35.4 ng/L; range <1.5-2,560.0 ng/L) for demeton. While the detection frequencies of the dimethoate, methyl parathion, malathion, and parathion were all less than 50% in all the surface water samples. Measured concentrations for the six compounds were low and rarely exceed the environment quality standard for surface water of China. The six OPPs compounds were more frequently detected at much higher concentrations in the rivers of north China compared with those of south China. The results of this investigation indicate that OPPs contamination in the Yellow River, Huaihe River, Liaohe River, and Haihe River basins of north China should be of particular concern. When compared with other regions of the world, it appears that the Chinese surface water is some moderately polluted by dimethoate, methyl parathion, malathion, parathion and contaminated by dichlorvos and demeton in certain degree.