Abstract: 【Objective】 The spatial variation characteristics of 1,2,3,4,5,6-hexachlorocyclohexane (HCH)，1,1,1-trichloro- 2,2-bis (p-chlorophenyl) ethane (DDT) and their isomers and metabolites concentration in surface soils of farmland were studied based on the survey of 131 sampling points of Beijing plain area. 【Method】Data were analyzed with the traditional statistical analysis method, the geo-statistical analysis with semivariogram structure and model fitting, the ordinary Kriging and the inverse distance weighting method. 【Result】 The traditional statistical analysis indicated that soil residues of total HCH, total DDT and their isomers and metabolites were lognormal distribution, the coefficients of the variation of all the observed items belonged to the strong degree. According to the geo-statistical analysis with semivariogram structure and model fitting, the soil residues of -HCH, -HCH and the total HCH had no spatial variation structure, while other isomers, metabolites and total DDT had space variation structure and variances may fit the exponential model or the Gaussian model, separately. The variation ranges of α-HCH, the total DDT and its isomers were larger than 18 km, which was relatively higher compared to 2.73 km for -HCH. The trend analysis indicated that all the DDT isomers, metabolites and the total DDT had the obvious tendency effect. But for HCH, only isomers -HCH and -HCH had a slight tendency effect. The contour maps of organochlorine pesticide residues were obtained using the Ordinary Kriging and the Inverse Distance Weighting Method. Based on those maps, the spatial distribution of organochlorine pesticide residues was analyzed.【Conclusion】The results indicated that HCH concentration in all 131 soil samples and DDT concentration in 85% of soil samples were lower than 0.05 mg·kg-1, and reached the first level of China's "Soil Environment Quality Standard" (GB15618-1995). The organochlorine pesticides pollution was generally slight in farmland soil of Beijing plain area.

Key words: Soil, Organochlorine pesticide, Pesticide residues, Spatial analysis