[Distribution characteristics of organochlorine pesticides in surface water and sediments from the Mengjin wetland].

The surface water and sediments from the Mengjin wetland were collected. After seperated and concentrated by solid phase extraction and Soxhlet extraction, twenty kinds of organochlorine pesticides (OCPs) in the samples from the Mengjin wetland were analyzed by gas chromatography. In the surface water, 7 kinds of OCPs (incluing alpha-HCH, beta-HCH, gamma-HCH, delta-HCH, 4,4-DDT, heptachor and aldrin) were detected, with the detected ratio of 4.2% -62.5% and the content range of ND-12.21 ng/L. In the sediments, 4,4-DDE and 4,4-DDT were detected, with the detected ratio of 50%-75% and the content range of ND-64.58 ng/g. HCHs and DDTs in the surface water were both lower than the limited value defined by Environmental Quality Standards for Surface Water in China, while the surface sediments in the Mengjin wetland pose a bit high risk comparing with ERL and ERM value of risk evaluation. Distribution characteristics of OCPs components showed that HCHs usually had higher residue levels in surface water, while sediment was the fate of DDTs in the transfer process of materials from water to sediment. OCPs content in the surface water and sediments both decreased in the order of high water period > level water period > low water period. OCPs in the low water seasons were mainly the early residue, but OCPs in the high seasons had some new input in near term in the surface water and sediments. The results suggested that non-point source was one of the important sources of OCPs entering Mengjin wetland.