Heavy metal(loid)s contamination assessment of soils in Shendong coal base of the Kuye River basin, China: spatial distribution, source identification and ecological risk

Source apportionment and risk evaluation of heavy metal(loid)s (HMs) in the soil is crucial for pollution mitigation and risk control in coal-mining areas. In this research, 129 topsoil samples were tested for HM content to explore the contamination characteristics, sources of contamination, and ecological risks of HMs in Shendong coal base, Shaanxi Province, China. The Nemerow integrated pollution index and the potential ecological risk index were used to assess soil contamination. A preliminary analysis of the source of HMs in the soil was performed using correlation analysis and principal component analysis. It was shown that the soil was heavily contaminated with Hg and Zn, moderately contaminated with Cd, slightly contaminated with Cu, and not contaminated with As, Cr, Pb, and Ni. It was also indicated by the potential ecological risk index that there was an extremely strong ecological risk of HMs in one soil sampling site and the remaining 128 sampling sites were classified as low risk. As for the spatial distribution, the heavily contaminated soil is located in the floodplain of the sewage outlet of the Daliuta coal wash plant. Analysis of the data shows that Hg and Zn originate mainly from anthropogenic sources, As, Cr, Cu and Ni from natural sources, and Cd and Pb from both natural and anthropogenic sources. In the study area, Cd poses the most widely distributed contamination and Hg shows the most significant ecological risk, suggesting that these two elements should be preferred contaminants for soil HMs contamination prevention and restoration. These findings highlight the ecological risks associated with potential sources of soil HMs contamination and provide valuable information for local environmental managers to mitigate the corresponding risks.