Abstract:

In order to study the concentrations and bioaccumulation characteristics of organochlorines, DDTs, HCHs, HCB and PCBs were detected in a series of aquatic organisms collected from the Dianshan Lake, including pond snails, shrimps and several species of fish. The results showed that DDTs, HCHs, HCB were found in all biological samples, the concentrations of the analyzed organochlorine pesticides in different organisms differed greatly from each other. Among the eight species, snakehead had the highest concentrations of organochlorines. This might be due to that snakehead, as a carnivore species, lies at a higher trophic level and has higher body fat ratio. The ∑DDTs (sum of DDT, DDE, DDD) concentrations ranged from 55 to 1135 ng/g lw in the muscle, the ∑HCHs (sum of αHCH, βHCH, γHCH, δHCH) and HCB concentrations ranged from 0.5 to 24 ng/g lw to 6.9 to 91 ng/ lw, respectively. DDTs were the dominant OCPs measured in the samples. The 4, 4DDE and αHCH were the most abundant congeners. As the predominant congener of DDTs, the 4,4DDE showed the highest concentrations in all samples and accounted for a mean percentage of 76.6% of the sum DDTs. The (DDD+DDE) /DDT ratios in all the aquatic organisms were above 1, which indicated that there was no recent input of DDT in the sampling region. The profiles of DDTs and HCHs suggested a historical usage rather than contribution from recent sources. PCBs were detected in all organisms except pond snail. The concentrations of PCBs in the aquatic organisms were in the following order: snakehead > crucian > horn > bleeker > loach> günther > shimp > pond snail. Taking pond snail as the reference, the OCPs biomagnifications factors (BMF) of different aquatic organisms ranged from 1.2 (loach) to 23 (snakehead). Taking shrimp as the reference, the PCBs BMF of different aquatic organisms ranged from 5.9 (günther) to 55 (snakehead). The lipophilic nature, hydrophobicity and low chemical and biological degradation rates of organochlorines have led to their accumulation in biological tissues and the subsequent magnification of concentrations in organisms, progressing through the food chain. The abovementioned results indicated that the studied organochlorine compounds can be bioaccumulated and biomagnified along the food chain in the Dianshan Lake, which may pose a potential threat to human health