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.

摘要 重金属污染是采矿活动的固有伴随产物，但矿区未采取污染防控措施，会加剧土壤、水体及生物体的污染扩散风险。本研究旨在评估未采取环保防护措施的尾矿(tailings)与剥离物(overburden)堆存时长，对白钨矿(scheelite)矿区土壤重金属污染程度的影响。本研究采集了当前运营白钨矿及已关停四十年的停产白钨矿0~20 cm深度的土壤样品。对土壤样品开展了粒度、pH值及重金属铁(Fe)、锰(Mn)、铬(Cr)、镍(Ni)、镉(Cd)、铜(Cu)、锌(Zn)与铅(Pb)含量的检测分析。在运营与停产矿区中，土壤重金属含量均出现相似幅度的升高，这表明即便剥离物与尾矿堆存时长较短，若未采取环保防护与修复措施，仍会产生有害影响。上述重金属含量升高现象警示：半干旱地区间歇性降雨引发的风力侵蚀与水力侵蚀，会使周边区域面临污染扩散风险。镉(Cd)、铜(Cu)与铅(Pb)的含量超出农业用地调查标准限值，表明该矿区存在威胁人体健康的风险，亟需开展矿区修复治理工作。