基于地理探测器的镇域尺度土壤重金属含量空间分异及其影响因素分析

Spatial Differentiation and Influencing Factor Analysis of Soil Heavy Metal Content at Town Level Based on Geographic Detector

为揭示镇域尺度规模土壤重金属含量的空间分异及其影响因素,以成都平原腹心地带某镇为研究区域,采集788份表层土壤样品,利用地累积指数法对土壤Cd、Hg、As、Cu、Pb、Cr、Zn和Ni的污染进行评价,基于地理探测器,以土壤性质、地形和距离等15种因子为自变量,各重金属含量为因变量,探析土壤重金属含量的空间分异及其影响因素.结果表明,研究区土壤Hg、As、Pb、Cr、Cu、Ni和Zn含量平均值是成都市土壤背景值的1.06~1.93倍,Cd含量低于背景值;除Hg呈现轻度污染外,其余7种重金属处于清洁状态.8种重金属空间分布存在显著差异,且各重金属间存在显著相关性,并与土壤性质存在显著相关性.因子探测发现,总磷(TP)、总钾(TK)、pH、总有机碳(TOC)、高程和距铁路距离对8种重金属含量的解释力最显著.交互作用探测发现,土壤性质与其他因子交互作用是重金属空间分异的最主要影响因素,高程、距住宅区距离、距铁路距离和距工业用地距离也是重要影响因子.风险探测发现,Hg在高程和距铁路距离的子区域的差异最显著,其余7种重金属在土壤性质影响因子子区域的差异最显著.镇域尺度规模土壤重金属的空间分布差异显著,这与研究区的土壤性质、地形和人类活动密切相关.

Geographic detectors can quickly detect spatial stratified heterogeneity and quantitatively reveal the intensity of driving factors of heavy metal content,which is of great significance for the prevention,control,and remediation of soil heavy metal pollution.In order to reveal the spatial differentiation and influencing factors of soil heavy metal content on the town-scale,788 topsoil samples were collected from a town in the hinterland of Chengdu Plain.Soil heavy metal(Cd,Hg,As,Cu,Pb,Cr,Zn,and Ni)pollution risk assessments were carried out by using the geo-accumulation index method.Additionally,based on the geographic detector model,15 factors such as soil properties,topography,soil forming factors,and distance were taken as independent variables,and the contents of each heavy metal element were taken as dependent variables to explore the spatial differentiation and influencing factors of heavy metal content in soils.The results showed that:the average contents of Hg,As,Pb,Cr,Cu,Ni,and Zn in the study area were 1.06-1.93 times the background value of Chengdu,and the content of Cd was lower than the background value;among them,Hg reached the light pollution level,and the other seven heavy metals were at the non-pollution level.The spatial distribution of eight heavy metals was significantly different,the correlation among the elements was significant,and a significant correlation was found between most heavy meals with soil properties;however,the correlation with distance factor and topographic factor was relatively weak.The factor detection showed that TP,TK,pH,TOC,elevation,and distance from the railway had the most significant explanatory power for the heavy metal contents.Interaction detection showed that the interaction between soil properties and other factors was the dominant factor for the spatial variation in heavy metals,and elevation,distance from residential area,distance from railways,and distance from industrial areas were also important factors.Risk detection showed that Hg had the most significant difference in the subregion of elevation and distance from railway,whereas the other seven heavy metals had the most significant difference in the sub-regions of influencing factors of soil properties.The spatial distribution of heavy metals varied significantly in soil at the town-scale,which was closely related to soil properties,topography,and human activities in the study area.