[Sediment record of DDTs in sediment core from Hongfeng reservoir]

In order to reconstruct the chronology of 2,2-his (4-Chlorophenyl)-1,1,1-trichloroethane (DDT) input into the Hongfeng reservoir and assess the pollution issues, the temporal distribution of DDT in sediment core from Hongfeng reservoir was measured using GC/MS method, and the possible sources and potential risk assessment also had been identified. The DDTs (sum of p,p'- and o,p'-DDT, DDE and DDD) in sediment core were ranged from 7.6 to 23.7 ng/g, and roughly, ever decreased from the bottom to the surface sediment. In detail, a sharp decline of DDTs concentration in sediment was found from 1981 to 1983, followed by a tardy decrease trend to the present. The DDTs in sediment were mainly composed of p,p'-DDTs (sum of p,p'-DDT, DDE and DDD). The ratio of p,p'-DDTs to o,p'-DDTs (sum of o,p'-DDT, DDE and DDD) ranged from 5.1 to 8.4, which suggests that the DDTs in sediment were chiefly originated from the technical DDT. Meanwhile, the DDTs in sediments were dominated by the metabolites of DDT (DDD and DDE) and the ratio of DDT/(DDD + DDE) were between 0.31 and 0.84, indicating the DDTs in sediment were mostly stemmed from the historical usage. Besides, the vertical profile of the ratios of DDT/( DDD + DDE) and DDE/DDD indicate that possible usage of technical DDT still occurred in the drainage area of Hongfeng reservoir around 1990, although the usage of technical DDT in agriculture has been banned in 1983. The residue levels of DDE, DDD, DDT, and DDTs in surface sediment from Hongfeng reservoir were all between ERL and ERM, suggesting potential risk could occur, and the contamination of DDT in Hongfeng reservoir deserving more concerns.