Multivariate and spatial analysis of heavy metal sources and variations in a large old antimony mine, China

Purpose

Contaminations by multiple heavy metals in antimony (Sb) mines produce serious environmental and health problems; however, the spatial variations in various heavy metals relative to the sources and transportation of Sb have rarely been documented. To resolve this problem, we conducted a survey in an old Sb mine in Xikuangshan (XKS), China, to investigate the similarities and differences among the sources and diffusion characteristics of the heavy metals that were present as well as the factors influencing these patterns.

Materials and methods

A total of 71 surface soil samples were collected in the central study area, which has a history of intensive mining and smelting activities, as well as in surrounding areas at different distances from the central mine and with different coverage/landscape/land use characteristics; we refer to these areas as the central mining subarea, tailing subarea in the southwest, forestry subarea in the southeast, grass subarea at the northern edge of the study area and vegetation subarea at the southern edge. Multivariate and spatial analyses were performed to explore the correlations and patterns of variation of various heavy metals.

Results and discussion

Hg and Cd were evidently elevated in XKS, whereas the concentrations of As, Pb and Zn were moderate and that of Cr was comparable to the background values. Moderate correlations were found for Sb–As and Hg–Cd, and strong correlations were observed for Pb, Zn, Cd and Cr. The southeast direction was associated with the strongest spatial autocorrelation for Sb, which is consistent with the prevailing wind direction in XKS; the optimal directions for Zn and Cd were similar and indicated the transfer of Zn and Cd contamination from subareas with high levels to those with low levels, significantly affecting the spatial distribution of these metals in XKS.

Conclusions

Our results highlight the importance of the effect of wind on the diffusion of Sb in XKS. The co-contamination of Hg and Cd with Sb is widespread in XKS due to the presence of Hg and Cd in Sb-containing ores.