Characteristics of organochlorine pesticide residues in agricultural soil of Chongming Island in Shanghai

Thirty surface soil samples were collected to investigate the residue concentrations of organochlorine pesticides (OCPs) in agricultural soil of Chongming Island in July 2008. Those samples were extracted using accelerated solvent extraction (ASE) and determined by gas chromatography with an electron capture detector (GC-μECD). Results showed that the concentrations of OCPs (dry weight) ranged between 3.11-117.47 ng·g^-1, with mean value of 26.25 ng·g^-1. Two major contaminants of OCPs were DDTs and HCHs, the concentration of which varied from 0.14 ng·g^-1 to 77.89 ng·g^-1 and from 1.14 ng·g^-1 to 22.43 ng·g^-1, respectively. At the same times, hexachlorobenzene (0.23-11.63 ng·g^-1), aldrin (0.03-0.75 ng·g^-1), heptachlor epoxide (0.05-1.44 ng·g^-1), dieldrin (0.05-5.33 ng·g^-1), endrin (ND-14.66 ng·g^-1) and mirex (0.03-10.58 ng·g^-1) could also be detected. Most of DDTs had been degraded to DDD and DDE, with the major compounds of DDE (about 64.7%), and the recent existed DDT was the residue of early input. All of the four isomers of HCHs were detected, and the contents of α-HCH (about 48.1%) and β-HCH (about 33.4%) were the maximum. The highest OCPs residues appeared in the soil of farm cultivation compared to greenhouse cultivation and ordinary open-air cultivation.