Contamination and health risks of soil heavy metals around a lead/zinc smelter in southwestern China

• The soil near a Pb/Zn smelter was seriously contaminated by Cd, Pb, and Zn.
• Their contents decreased more rapidly in upwind than downwind direction.
• Their mobility order is Cd≥Zn⪢Pb.
• Antropogenic input increased Cd, Zn, and Pb bioavailability in the soil.
• Pb might pose higher potential health risk to children than other toxic metals.

Anthropogenic emissions of toxic metals from smelters are a global problem. The objective of this study was to investigate the distribution of toxic metals in soils around a 60 year-old Pb/Zn smelter in a town in Yunnan Province of China. Topsoil and soil core samples were collected and analyzed to determine the concentrations of various forms of toxic metals. The results indicated that approximately 60 years of Pb/Zn smelting has led to significant contamination of the local soil by Zn, Pb, Cd, As, Sb, and Hg, which exhibited maximum concentrations of 8078, 2485, 75.4, 71.7, 25.3, and 2.58 mg kg−1, dry wet, respectively. Other metals, including Co, Cr, Cu, Mn, Ni, Sc, and V, were found to originate from geogenic sources. The concentrations of smelter driven metals in topsoil decreased with increasing distance from the smelter. The main contamination by Pb, Zn, and Cd was found in the upper 40 cm of soil around the Pb/Zn smelter, but traces of Pb, Zn, and Cd contamination were found below 100 cm. Geogenic Ni in the topsoil was mostly bound in the residual fraction (RES), whereas anthropogenic Cd, Pb, and Zn were mostly associated with non-RES fractions. Therefore, the smelting emissions increased not only the concentrations of Cd, Pb, and Zn in the topsoil but also their mobility and bioavailability. The hazard quotient and hazard index showed that the topsoil may pose a health risk to children, primarily due to the high Pb and As contents of the soil.