Identification of Soil Heavy Metal Sources Around a Copper-silver Mining Area in Ningxia Based on GIS

Abstract

This study area was based on the catchment area of the Yaoxianzi ditch located in the arid region of western China. A total of 194 topsoil samples of 0-20 cm depth were collected using the mesh distribution method. The contents of nine heavy metals (Ni, Cu, Zn, As, Ag, Cr, Cd, Hg, and Pb) were determined using ICP-MS. The source and spatial distribution of heavy metals were analyzed using PMF and IDW. Spatial autocorrelation and clustering and outlier analysis were performed using the Spatial Statistical Analysis tool of ArcGIS. The main sources and distribution areas of heavy metals in the soil were obtained through comprehensive analysis. In the study area, the average values of Hg, Ag, Cd, and Pb were 20.48, 3.13, 2.23, and 1.12 times the background values, and the maximum values of Cd, Cu, Pb, and As were 10.92, 5.52, 2.03, and 1.39 times the filter values, respectively. The coefficients of variation of Cu, Cd, Pb, and Hg were ordered as Cu(283.23%)>Cd(224.77%)>Pb(144.40%)>Hg(67.12%) and were closely affected by human activities. The heavy metals in the soil around mining areas came from four main sources:natural parent material (32%), the mixed source of mining activities and transportation (17.1%), the mixed source of industrial activities and atmospheric sedimentation (40.3%), and the mixed source of agricultural activity and putting sandy gravel in farmland (10.6%). Cr and Ni, As and Cu, Hg, and Cd could represent these four sources of heavy metal pollution, respectively. The main sources of soil heavy metal pollution were mining activities and agricultural activities. The heavily contaminated areas were distributed in the mining areas in the south of the study area and in the planting areas in the eastern, central, and northwestern parts of the study area.