Ecological Risk Assessment and Source Analysis of Heavy Metals in the Soils of a Lead-Zinc Mining Watershed Area

In this study, concentrations of Cr, Mn, Pb, Cu, Zn, As, Cd, Sb, and Fe were determined in soils of a Pb-Zn mine watershed in northern Guangxi, China, for ecological risk assessment and source analysis. The atomic fluorescence spectrometry and ICP-OES were used to determine concentrations of heavy metals (HMs), and the total amount of Mn, Cu, Zn, As, Cd, and Pb exceeded the limit. Among them, the weak acid extractable fraction (F1) state masses of Pb, Mn, and Zn accounted for a higher ecological risk. The study area was divided into three distinct areas: highest concentrations of HMs were distributed in front of the Sidi River mountain (1# and 2#) and at the subterranean river entrance (5# and 6#), followed by the area along the river and the irrigated area of the river (3# and 4#), and the central highlands and southwestern parts had low concentrations (7# and 8#). The ecological risk assessment results indicate Cd is of extremely high ecological risk, Pb and Mn are of medium minor ecological risk, Zn is of minor ecological risk, and the rest have almost no impact on the eco-environment. The source apportionment results showed that Cu, Zn, Cd, Sb, and Pb were mainly controlled by anthropogenic activities, such as mining; Cr, Fe, and As were mainly influenced by natural processes, such as soil-forming parent rocks; and Mn is jointly controlled by mining and soil-forming parent rocks. This study can provide scientific guidance and technical support for soil risk control or remediation in mining areas.