Abstract:Contents of HCH and DDT were measured and their isomeric compositions were investigated in 129 soil samples of typical agricultural surface soils gathered from 7 counties in the Huang-Huai-Hai Plain,China,to understand the present status of residues of the organochlorine pesticides commonly used in the past and to assess their potential toxicology to the environment.HCHs(HCHs=a-HCH+(3-HCH+y-HCH+8-HCH)was detected in all the samples analyzed,with an average content (±SD) of 4.01(±2.21)μg kg-1,while DDXs(DDXs=4,4'-DDE+4,4'-DDD+2,4'-DDD+4,4'-DDT) was found in 93% of the samples,with an average content(±SD) of 11.16(±17.29)μg kg-1.The former was found far less than 50 μg kg-1 in these samples,while the latter exceeding 50 μg kg-1 in 3.1% of the samples,an upper limit of the norms for HCH and DDT set by the state for quality of the first-class soil.Generally,agricultural soils from the Huang-Huai-Hai Plain were less contaminated with organochlorine pesticides than the samples from Tianjin,Europe,and USA.The highest contents of β-HCH with mea ±SD value of 2.48±1.88 μg kg-1)among 4 HCH isomers and of 4,4'-DDE(with mean ±SD value of 6.91±13.67 μg kg-1)among 4 DDT isomers were observed.Pesticide residues were not proportional to soil organic matter.