Organo-chlorine pesticide (DDT and HCH) residues in the Taihu Lake Region and its movement in soil-water system I. Field survey of DDT and HCH residues in ecosystem of the region

The use of organo-chlorine (DDT and HCH) has been banned in China for 20 years. A field survey was carried out during 1999-2000 in the Taihu Lake Region. Organo-chlorine pesticide (OCP) residues in soil, water, fish and sediment samples were investigated. DDT was detected in 5 out of 10 samples with concentration ranging from 0.3 to 5.3 mug/kg in the surface (0-15 cm) layer, 6 out of 10 with 0.5 to 4.0 mug/kg in the subsoil layer (16-30 cm), and 4 of 10 with 0 to 2.7 mug/kg in the deep soil layer (31-50 cm). Results for HCH residues in soil samples were similar to those of DDT. These results indicate that OCP residues in 0-50 cm profile had been leached out or degraded to safe level. In river water DDT was detected in 10 out of 13 samples ranging from 0.2 to 9.3 mug/l, with an average of 1.0 mug/l. While HCH was detected in 12 out of 13 samples ranging from 0.02 to 36.1 mug/l, with an average 5.6 mug/l. DDT residues in sediment ranged from 0.1 to 8.8 mug/kg, while HCH ranged from 0.3 to 66.5 mug/kg. DDT residues in fish body ranged from 3.7 to 23.5 mug/kg and HCH ranged from 3.7 to 132 mug/kg. These results demonstrate an accumulation through food chain (from soil-water-sediment-microbes-crop-fish-... etc.), also that HCH residues are generally more persistent than DDT residues. However, all these data are well below than the state warning standard limit. (C) 2002 Elsevier Science Ltd. All rights reserved.