沱江上源支流土壤重金属污染空间相关性及变异解析

Spatial correlation and variation analysis of soil heavy metals contamination in upper source tributary of Tuojiang River, China

为探究沱江上源支流土壤Cd、Hg、As、Pb、Cr 5种重金属的空间变异及其相关性,运用Global Moran’s I和Anselin Local Moran’s I空间关联指数进行相关性分析,并利用半变异函数云分析其空间结构,最后利用克里金法对污染空间进行预测,并分析其变异成因。结果表明:研究区土壤Cd、Hg、As、Pb、Cr 5种重金属含量大部分处于较低水平,且平均值均未超过国家土壤环境质量标准(GB 15618—2018)风险筛选值;土壤重金属含量与空间均呈现正相关的特点;除Hg外其他重金属产生聚类特征的可能性均很大,但从局部冷热点及异常值分析可知,Hg也存在聚类特征;Cd、Pb的空间连续性较好、相关性强烈且变程最长,As、Cr次之,Hg最差;重金属含量空间变异与企业分布、污水灌溉、大量施肥以及其他自然因素具有一定的相关性。

To explore the spatial variation and the correlation of soil heavy metals(Cd,Hg,As,Pb,and Cr)in the upper source tributary of Tuojiang River,we analyzed the spatial correlation of soil heavy metals through Global Moran′s I and Anselin Local Moran′s I and ana⁃lyzed their spatial structures using semi-variation cloud.Finally,we predicted the spatial distributions of heavy metals contamination using Kriging′s method and evaluated the causes of the spatial variation.The results showed that soil heavy metals contents were mostly at a low level,and their averages did not exceed the risk screening value of national standard for soil environmental quality(GB 15618—2018).There was a positive correlation between soil heavy metals contents and space in the study area.Heavy metals were likely to have clustering characteristics except Hg that exhibited clustering characteristics through the analysis of local cold-hot spots and abnormal values.Cd and Pb had good spatial continuity,strong correlation,and the longest range of variation,followed by As and Cr,and Hg was the worst.The spa⁃tial variations of heavy metals in this study area were related to the distribution of enterprises,sewage irrigation,heavy fertilization,and oth⁃er natural factors.