Distribution Features and Eco-risk Evaluation of Organochlorine Pesticides in Vegetable Soil of Chengdu Area

To determine current levels of organochlorine pesticides(OCPs) and to assess their distribution characteristics and potential eco-risk in vegetable soil,soil samples were collected from fourteen districts and counties in Chengdu region of Sichuan province and twenty-three kinds of OCPs were quantified by means of gas chromatography equipped with a 63Ni electron-capture detector(GC-ECD) system.The results show that OCPs were found widely in all these samples and ranged from 20.18 to 104.33 μg·kg-1,and residue levels of OCPs in vegetable soils from the outskirts of Chengdu(e.g.Shuangliu county,Long quanyi District,Pi county,Xindu District and Wenjiang District) were apparently less than those from outlying counties.Among eighteen kinds of OCPs found in the soil samples,including dichlorodiphenyltrichloroethane(DDT) and its principal metabolites dichlorodiphenyldichloroethylene(DDE) and dichlorodiphenyldichloroethane(DDD),hexachlorocyclohexane(HCH) and its isomers(α-,β-,γ-,and δ-HCH),aldrin,hexachlorobenzene,dieldrin,endrin,a-endosulfan,γ-chlordane,heptachlor epoxide,toxaphene and mirex,DDTs and HCHs were detected in all soil samples,with a range of 16.11～99.51 μg·kg-1 for DDTs and 1.31～9.34 μg·kg-1 for HCHs,and were the main components in residues of OCPs,accounting for 87.68% and 8.15% of the total,respectively.Hexachlorobenzene has an occurrence of 90%,a-endosulfan,γ-chlordane,heptachlor epoxide and mirex were detectable in a range of 44.29%～47.14% of all the samples,which were mostly collected in the outskirts of Chengdu.However,aldrin,dieldrin,endrin and toxaphene were only found in these sites in northwestern of Chengdu,such as Pengzhou,Du jiangyan,Dayi and Chongzhou),accounting for 32.86%～37.14% of the collected soil samples.Various isomers in OCPs and the changing rule of metabolins indicate residues of DDTs、HCHs in the soils might come from the old usage or atmosphere input,but there might be input into environment recently in Jintang,Qin bai-jiang and Xinjin regions for DDTs,and so does in Pengzhou,Du jiang-yan,Dayi and Chongzhou regions for HCHs.The eco-risk analysis shows that HCHs residues in the soils have no obvious influence on the geobiont there,while DDTs might have certain ecological risks on birds and geobiont.