Scheelite mines soils as sources of heavy metal contamination

Abstract

Heavy metals contribution is inherent to mining activity, however the absence of pollution control measures in mined areas contributes to the expansion of the contamination potential of soil, water, and organisms. The aim of this work was to evaluate the effect of exposure time of tailings and overburden deposition without environmental protection measures over soil heavy metal contamination stage in scheelite mines. Soil samples were obtained from 0-20 cm depth in active scheelite mine and in deactivated scheelite mine since four decades ago. Soil samples were submitted to analyses of particle-size, pH and contents of heavy metals Fe, Mn, Cr, Ni, Cd, Cu, Zn, and Pb. The increases of heavy metals contents at similar levels in active and deactivated mines indicate that even a smaller exposure time of overburden and tailings has a harmful effect when environmental protection and recovery measures were not adopted. These increases alert to the contamination risk of adjacent areas due to wind erosion and hydric erosion during the intermittent rainy events of semi-arid region. Cd, Cu, and Pb contents higher than values of agricultural investigation indicate that there is a risk to human health and that there is need for remediation of mined areas.