Abstract: DDT and its metabolites（DDT residues）were measured in water,suspended solid（SS）,sediment and fish（Carassius auratus and Hypophthalmichthys molitrix）from two fishponds as well as top soils on their shores in Tianjin.It was found that all the media（including fish muscle and organs）were severely contaminated with DDT residues. The mean concentration of DDT residues in fish muscle was （66.4±2.7）ng·g^-1 for Carassius auratus and （24.3±23.4）ng·g^-1 for Hypophthalmichthys molitrix,respectively.The ΣDDT concentration in intestines was 3.2-3.9 times higher than in fish muscle. However,the ΣDDT content in gills was only 1.3-1.7 times higher than the content of DDT residues in fish muscle,indicating that DDT residues may accumulate in fish via intake of suspended particles（ingestion process）as well as via direct intake from water by gills.Their bioconcentration coefficient（lgBCF）reached 3.7 and 3.3,respectively.The two fishponds differed significantly in DDT residue content.ΣDDT concentrations in various media were much higher in the fishponds located in the area with the top soil severely contaminated with DDT residues than the other in the area less contaminated. The ratios of DDE/ΣDDT were relatively high for that severely contaminated fishpond,indicating heavy application of DDT in the past.However,the very low DDE/ΣDDT values in suspended solids along with the relatively high DDT concentrations suggested recent inputs of DDT.

Key words: DDT, fishpond, water, fish, suspended solid, sediment, soil, Tianjin