Distribution Characteristics Of Persistent Organic Pollutants In Source Area Of South-to-North Water Diversion Middle Line Project

South-to-North Water Diversion Middle Line Project is a major strategic decision of the State to conduct inter-basin water resources optimal allocation, which is a major water conservancy projects to ease the drought and water shortage in northern China and ensure water supply safety. Recently, as the water source of the middle canal, Danjiangkou reservoir, has draw much attention of the government and the environmental scientist, focusing on the agriculture nonpoint pollutant of nitrogen and phosphorus. However, data about the current contamination status with POPs which Seriously affect human health and water quality, were very scarce in this area. So, it will be of great significance, and has great practical value on monitoring and analysis of POPs in Danjiangkou reservoir water and soil environment.The pollution of persistent organic pollutants in the soil from Xichuan submerged area, surface water of Haoping river and runoff have been analyzed in this article.15 runoff ponds of three groups were built, and farmland soil samples, surface water samples and three times runoff samples have been collected for experiments, Basing on the data of 7 times experiments within 2 years, the types, level, distribution, sources and possible ecological risk about OCPs and PAHs were initially acquired in the reservoir area. It was found that:1. Two of OCPs (a-HCH and DDE) and ten of PAHs were detected in the soil from Xichuan submerged area, in comparisons with other areas, the mean value of a-HCH content in present study was higher slightly, DDE was at the same level and PAHs was lower relatively. OCPs pose a bit high risk and PAHs have little negative ecological risk comparing with ERL and ERM value of risk evaluation.2. Five of OCPs (a-HCH, heptachlor epoxide, endosulfanⅠ,Ⅱendosulfan and endosulfan sulfate) and eleven of PAHs were detected in Haoping River. It should be noted that contents of Chr, Bbf and Bkf were higher than the National Recommended Water Quality Criteria limits (US EPA at 2006),, which should be paid further attention.3. In the runoff of farmland soil and orchard, only a-HCH of OCPs was detected. The average content of a-HCH in farmland soil is about more than 30 times than that of orchard. The average contents and component types of PAHs in three types of land-use were all decreased in the order of cultivated land>orchard>mountain forest. Baa, Chr, Bbf, Bkf and Bap were out of the National Recommended Water Quality Criteria limits. There were a certain degree of ecological risk about runoff PAHs pollution in the study area. It was also be found that the runoff volume and the total PAHs content in runoff increase with the slope.4. Based on the Molecular Markers Indicative Law, the source analysis of PAHs was carried out. It was found that the dominant source of PAHs in the soil from Xichuan submerged area was combustion of coal, and a small amount came from vehicle exhaust emissions.5. The health risk from PAHs by drinking for one person ranged from 1.40×10-12 to 5.28×10-12 a-1, were lower than the maximum tolerable value(5.0×10-5 a-1) recommended by ICRP. The health risk of PAHs in the level period was six times than abundant water period.