Residue characteristics and risk evaluation of BHC and DDT in sediments of culture ponds in Zhuhai

The benzene hexachlorides (BHCs) and dichloradiphenyl trichloroethanes (DDTs) in sediments of some aquaculture ponds in Zhuhai, China were determined in July, 2005. The results showed that the contents of total BHC and total DDT were from 0.36 to 1.67 (arithmetic mean=0.91) μg·kg^-1 and 0.95 to 2.59(1.81) μg·kg^-1, respectively. The residue levels of ΣBHC, ΣDDT in sediments of the tested area were lower than those of some rivers, lakes and bays, and also under the superior limits of national sediment quality standard for no contamination fishery products. The quality grade of BHCs or DDTs was "basically clean". The ratio of γ-BHC/ΣBHC, (DDE+DDD)/ΣDDT were from 0 to 21.6% and 61.1% to 76.7%, respectively. It may be guessed that BHCs gradually decreased, most residual DDT had decomposed to DDE and DDD, there was little or no BHCs or DDTs distributed into the sediments of Zhuhai aquaculture ponds in recent years. The contents of BHC and DDT were lower than the ERL value of risk evaluation to consumers of bottom feeders.