Source Identification and Potential Ecological Risk Assessment of Heavy Metals in the Topsoil of the Weining Plain (Northwest China)

The Weining Plain is an important area for agricultural production in northwest China. It is, therefore, imperative that stakeholders understand the status of topsoil heavy metal pollution, the sources of the metals, and the associated ecological risks. In this study, 71 topsoil (0-20 cm) samples were collected from the Weining Plain and analyzed for Cd, Cr, Zn, Pb, Cu, and Ni. The results showed that the average concentrations of Cd, Pb, Zn, and Cr seriously exceeded the background values for Ningxia in the study area. Spatial analysis revealed that the six heavy metals all had elevated levels, especially near industrial zones. Based on the absolute principal component scores-multiple linear regression model, the sources of heavy metals in topsoil were divided into anthropogenic, natural, and agricultural sources. Anthropogenic sources of pollution were the primary source of most of the heavy metals in the topsoil. The results of the heavy metal pollution index and the Hakanson potential ecological risk index showed that the topsoil quality is slightly polluted by the heavy metals except Ni. The concentrations of heavy metals in the study area as a whole represented a medium potential ecological risk, with Cd posing highest potential for ecological risk.