Residual of organochlorine pesticides and distribution characteristics in the vegetable soils from Chengdu region of Sichuan province,China

To determine current levels of organochlorine pesticides(OCPs) and to assess their distribution characteristics in vegetable soils,soil samples were collected from fourteen sites in Chengdu region of Sichuan province in July 2010,and twenty-three kinds of OCPs were quantified by means of gas chromatography equipped with a 63Ni electron-capture detector(GC-ECD) system.Results showed that OCPs were found widely in all soil samples and ranged from 20.18 to 104.33 μg·kg-1,and residue levels of OCPs in soils from outskirts of Chengdu(e.g.Shuangliu,Long quan-yi,Pi county,Xindu and Wenjiang) was apparently less than those from outlying counties(e.g.Jintang,Qin bai-jiang,Xinji,Pujiang,Pengzhou,Du jiang-yan,Dayi and Chongzhou).Among eighteen kinds of OCPs found,including 1,1,1-trichloro-2,2-bis(p-chlorophenyl)ethane(DDT) and its metabolites 1,1-dichloro-2,2-bis(p-chlorophenyl)ethylene(DDE) and 1,1-dichloro-2,2-bis(p-chlorophenyl)ethane(DDD),hexachlorocyclohexane(HCH) and its isomers(α-,β-,γ-,and δ-HCH),aldrin,hexachlorobenzene(HCB),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.Compared to HCB with 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 mostly collected in the outskirts of Chengdu.However,aldrin,dieldrin,endrin and toxaphene were only found in these sites in northwestern of Chengdu(e.g.Pengzhou,Du jiang-yan,Dayi and Chongzhou),accounting for 32.86%～37.14% of the collected soil samples.Furthermore,indicated by the changing rule of residues of OCPs,their principal metabolites and isomers,the authors induced that for most area,residues of OCPs in the soils might come from the old usage or long distance trantsportion from their application sites,but there might be input into environment recently in Jintang,Qin bai-jiang and Xinjin regions for DDTs,and so did in Pengzhou,Du jiang-yan,Dayi and Chongzhou regions for HCHs.