Study On Environmental Behaviour Of Organochlirine Compounds In Hangzhou

Pesticides give a contribution to social development for a long time. However, it can not be ignored that the environmental pollution produced by them. Dichlorodiphenyltrichloroethanes (DDTs), hexachlorocyclohexanes (HCHs), paclobutrazol (PBZ) and uniconazole (UCZ), which can be classified as organochlirine compounds (OCs), were persistent and not easily degraded in environment. In China, DDTs and HCHs have been banned, while PBZ and UCZ were still use now. Hangzhou, which was developed agriculture area, had used a large amount of organochlorine compounds. Pollution by these compounds is still unknown in this area. With the development of urbanization, agriculture has been basically disappeared in Hangzhou. However, the suburb still retains farmland for ecological functions and purveyance,. Some greenhouses used in farmland to increase economic benefit of crops. The pollution characteristic of DDTs and HCHs which have been banned and dissipation differences by greenhouse and open field cultivation of PBZ and UCZ which are currently used were still unclear. This work investigate the pollution characteristic of the above compounds in Hangzhou including residues and distribution characteristics of DDTs and HCHs in air, water and sediment, dissipation characteristics of PBZ and UCZ in open field and greenhouse, and enantioselective degradation of organochlirine compounds in environment.The highest concentration of DDTs and HCHs were found in water exchange outlet of Qiantang River to West Lake in dissolved, particle phase and surface sediment, which indicate Qiantang River might be source of DDTs and HCHs in Hangzhou.DDTs and HCHs tend to exist in the air and sediment according to the distribution coefficient Ki.j. DDTs tend to exist in the particle phase, while HCHs are prone to present in the dissolved phase in water.The (+)-enantiomers of a-HCH and o,p-DDT were more prevalent than (-)-enantiomer in most sediment column samples.The concentrations of DDTs and HCHs in water and sediment do not exceed the national environmental quality standard. Risk assessment for surface sediment indicates that DDTs (especially p, p’-DDE) and y-HCH are the main species of ectoxicological concern. p,p’-DDT in some samples exceeded the Criterion Continuous Concentration (CCC,USEPA2009) value in water. It should be paid more attention that aquatic life suffered chronic toxicity by p,p’-DDT.The dissipation of paclobutrazol(PBZ) and uniconazole(UCZ) in greenhouse were different from those in open field.They were more persistent in greenhouse than in open field soil. The penetration produced by rainfall gave a greater contribution to the dissipation of PBZ and UCZ in open field surface soil than that in greenhouse surface soil. PBZ and UCZ had potentials to penetrate into deep soil layers. UCZ was more potent than paclobutrazol in penetration and leaching. Enantioselective degradation of PBZ and UCZ were observed in both soils.The persistence of PBZ and UCZ in greenhouse soil increased the possibility of phytotoxicity to the next crops, whereas the leaching in open field surface soil would produce environmental risk to groundwater and also contaminate surface water by ground-water input. It should be paid attention to the use amount of PBZ and UCZ in greenhouses and application time in open field. Additionally, environment risk and management of PBZ and UCZ should be considered at enantiomers level.