Soil heavy metal pollution around the Dabaoshan Mine, Guangdong Province, China

Soil contamination in the vicinity of the Dabaoshan Mine, Guangdong Province, China, was studied through determination of total concentrations and chemical speciation of the toxic metals, Cu, Zn, Cd, and Pb, using inductively coupled plasma mass spectrometry. The results showed that over the past decades, the environmental pollution was caused by a combination of Cu, Zn, Cd, and Pb, with tailings and acid mine drainage being the main pollution sources affecting soils. Significantly higher levels (P <= 0.05) of Cu, Zn, Cd, and Pb were found in the tailings as compared with paddy, garden, and control soils, with averages of 1486, 2516, 6.42, and 429 mg kg(-1), respectively. These metals were continuously dispersed downstream from the tailings and waste waters, and therefore their concentrations in the paddy soils were as high as 567, 1140, 2.48, and 191 mg kg(-1), respectively, being significantly higher (P < 0.05) as compared with those in the garden soils. The results of sequential extraction of the above metals from all the soil types showed that the residual fraction was the dominant form. However, the amounts of metals that were bound to Fe-Mn oxides and organic matter were relatively higher than those bound to carbonates or those that existed in exchangeable forms. As metals could be transformed from an inert state to an active state, the potential environmental risk due to these metals would increase with time.