典型农区耕作土壤重金属空间变异的稳健性分析

以鲁西北典型农区禹城的耕作土壤重金属Cr、Pb含量为例,针对其偏态分布特点与变异函数的非稳健性,研究了克瑞西-豪金斯法(C-H)、中位调节法(MA)、中位数中位偏差法(MMD)和位置的Huber估计(HB)4种稳健统计方法对土壤重金属变异函数的稳健处理效果,交叉检验了各稳健处理变异函数模型用以克里格估值的精度,分析了该地区耕作土壤重金属的空间分布特征。结果表明:研究区土壤Cr、Pb含量变异性较强且其频数分布均呈强烈偏态特征;稳健处理使得变异函数的块金值、基台值总体降低,块金值/基台值和拟合精度均不同程度升高;C-H法和MMD法稳健处理下,土壤Cr、Pb含量克里格空间预测的精度最高,是较优的稳健处理方式;研究区土壤Cr、Pb含量的空间分布呈现局部斑块状的分布格局,目前耕地土壤环境质量良好。该研究结果为该地区耕地环境质量评价和重金属污染防控提供科学依据。

Robust Analysis on Spatial Variability of Heavy Metals in Typical Cultivated Soils

Considering the skew distribution and unrobustness of variogram of total content of soil heavy metal Cr and Pb in Yucheng City,four robust statistical methods including Cressie and Hawkins method(C-H),median adjustment method(MA),median of median deviation method(MMD) and Huber's estimation of location(HB) were introduced to study the robustness effect on variogram of soil Cr and Pb,then the kriging estimation accuracy was cross-validated for each method,and finally the spatial distribution of soil Cr and Pb across the study area was evaluated.Results indicated that soil Cr and Pb content exhibit strong spatial variation and skewness,and variogram parameters of nugget and sill decrease after robust treatment for both soil Cr and Pb,while the ratio of nugget to sill and fitting precision of variogram increase.The best kriging estimation precision is obtained for soil Cr and Pb under the treatment of mean of C-H method and MMD method respectively,which are selected as the optimal rubust statistical methods.The spatial distribution of soil Cr and Pb shows local patched and the environmental quality of cultivated soils is in good condition across the study area.The research results provide scientific reference to environmental quality assessment and prevention of heavy metal contamination for cultivated soils in Yucheng City.