城郊农业土壤重金属不同尺度空间分布及源分析——以宁镇交界带为例

为了研究城郊农业土壤重金属空间分布特征和来源,以宁镇城郊农业土壤为研究对象,利用Arcgis中地统计学方法研究了三种尺度下重金属Cr、Ni、Cu、Zn、As、Pb的空间变化特征,运用PCA法分析土壤重金属的来源及尺度差异。研究结果表明:除了Ni之外,土壤中Cr、Cu、Zn、As、Pb的含量均超过了南京土壤背景值,土壤重金属的空间格局呈现明显差异;Ni、As在小尺度下能更好地反映其本身的空间分布格局,而Cr、Pb在大尺度下能更好地反映出主要的空间分布特征,Cu、Zn在3种尺度下均没有明显差异。通过主成分分析和周边环境分析,认为Pb、As主要受交通运输活动的影响,Cu、Zn主要受农业活动的影响, Ni、Cr则受土壤成土母质的影响,但不同尺度显示的土壤成分与重金属关联性存在差异,小尺度要明显好于中、大尺度。

Multi-scale Spatial Distribution and Source Discrimination of Heavy Metals in Suburb Soils: A Case Study of Junctional Zone between Nanjing City and Zhenjiang City

Studying the spatial distribution characteristics of heavy metals in soils provides valuable information not only for pollution source identification, but also for soil quality assessment. In this study,we investigated the multi-scale spatial distribution and source discrimination of Cr, Ni, Cu, Zn, As and Pb in agricultural soils in a junctional zone between Nanjing City and Zhenjiang City, using geostatistics method. Heavy metal concentrations in most of the studied soils exceeded the soil background values of Nanjing, except Ni, indicating the enrichment of heavy metals in the suburb soils. The semivariance analysis showed that the spatial patterns of heavy metals had obvious differences at different scales. Nickel and As displayed the spatial patterns at the small scale, while Cr and Pb had the spatial patterns preferably at the large scale. The spatial patterns of Cu and Zn showed no significant difference at different scales. Principal component analysis(PCA)showed that Pb and As were influenced by traffic source, whereas agricultural activities were the main source of Zn and Cu pollution. Nickel and Cr were mainly associated with parent materials. The association between heavy metals and soil composition was different at different scales, with better association at smaller scales than at moderate and large scales.