Heavy metal pollution of the world largest antimony mine-affected agricultural soils in Hunan province (China)

Purpose The present work concerns the distribution of ten heavy metals (Sb, As, Cd, Cr, Cu, Hg, Mn, Ni, Pb, and Zn) in the surrounding agricultural soils of the world largest antimony (Sb) mine in China. The objective is to explore the degree and spatial distribution of heavy metal pollution of the Sb mine-affected agricultural soils. The presented data were compared with metal concentrations in soils from mining and smelting sites in China and other countries. Materials and methods There were 29 environmental samples in all that were collected in the year 2008 for this study. Soil characteristic parameters such as pH, total organic carbon, and cation exchange capacity were determined. Metal contents were determined after digestion in a Teflon bomb with aqua regia. Cd, Cu, Ni, Pb, and Zn concentrations were determined by inductively coupled plasma-mass spectrometry. As, Sb, and Hg concentrations were determined by atomic fluorescence spectrometry (AFS-2202). Fe, Al, Cr, and Mn concentrations were determined by inductively coupled plasma-atomic emission spectrometry. Results and discussion Almost all of the ten heavy metals exhibited much higher concentrations compared with their respective natural background values, especially Sb, and they varied with sampling site. The enriched factor values show that Sb (235.8), Cd (51.8), Hg (13.8), As (3.13), Zn (2.91), Pb (2.46), and Cr (1.67) are significantly accumulated in the study area. All of the integrated pollution indexes (IPI > 3) calculated from pollution indexes show that the soils are severely contaminated by investigated heavy metals. Principal component analysis, cluster analysis, and correlation analysis suggest that Cd, Cu, Pb, Zn, and Mn are derived from the sulfide mineralization paragenesis in Xikuangshan area. Cr, As, Hg, Al, and Sb are mainly due to the mining and smelting activities of this area and derived from organic matters, and Ni is mainly generated from agricultural activities. These metal concentrations in Xikuangshan agricultural topsoil are comparable or within the ranges of those in mine areas of other countries. Conclusions The heavy metal concentrations in the topsoil of Xikuangshan area are mostly higher than the background values, especially for Sb and As. Heavy metal pollution has spread in this mine area, both from mining activities and agricultural activities. Analysis of soil samples from 23 sampling locations of the area show significant spatial variation of the ten heavy metals.