北京市农田土壤中有机氯农药残留的空间分析

Spatial Variability of Organochlorine Pesticides (DDTs and HCHs) in Surface Soils of Farmland in Beijing,China

【目的】通过在北京平原区农田采取的131个表层土壤样品的化验分析,研究土壤中有机氯农药六六六(HCH)和滴滴涕(DDT)残留总量及异构体、代谢物含量的空间变异特征。【方法】样品测定结果采用传统统计分析,半方差结构和模型拟合的地统计分析以及结合普通Kriging和反比距离插值方法进行分析。【结果】传统统计分析表明,土壤中残留HCH和DDT的异构体、代谢物及总量均服从对数正态分布,并全部属于强变异。基于半方差结构和模型拟合的地统计分析,γ-HCH、δ-HCH和HCH总量没有空间变异结构方差,而其它农药含量存在空间变异结构方差、且可分别用指数模型或高斯模型拟合。模型拟合的结果看出α-HCH、DDT总量及其异构体以较大范围的变异为主(变程大于18km),而β-HCH的变程只是2.73km。趋势分析表明DDT的异构体、代谢物及总量都存在明显的趋势效应,而HCH及其异构体中只有β-HCH和γ-HCH略有趋势效应。结合普通Kriging和反比距离插值方法,获得了土壤有机氯农药残留含量的等值线图,并分析了其空间分布规律。【结论】所有土壤样本中的六六六含量和85%的土壤样本的滴滴涕农药含量均达到国家《土壤环境质量标准》(GB15618-1995)一级标准(<0.05mg·kg-1),残留污染较轻。

[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 γ-HCH, δ-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 β-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 β-HCH and T-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＂ （GB 15618-1995）. The organochlorine pesticides pollution was generally slight in farmland soil of Beijing plain area.