广西珊瑚钨锡矿硅质尾矿的中和能力与重金属释放污染

Neutralization capacity and heavy metal release of siliceous tailings in Shanhu W-Sn mine,Guangxi

中性矿山废水(NMD)及重金属释放污染问题容易被忽视。以广西珊瑚钨锡矿石英脉型矿石选余的尾矿即硅质尾矿作为研究对象,采用尾矿酸-碱估算,以及地质积累指数、潜在生态危害指数和迁移污染效应(元素可交换态含量)等评价方法,分析珊瑚硅质尾矿的中和能力与重金属(Cd、Zn、Pb、Cu及As)释放污染的危险性。研究结果表明:(1)珊瑚尾矿的中和能力较强(平均中和潜力比率NPR=4.74,平均净产酸潜力NAPP=-41.2kgH2SO4/t),并且硫含量较低(平均总硫TS=0.60%),不存在释放酸性矿山废水(AMD)的危险,属于非释酸尾矿。尾矿的酸中和矿物主要是方解石和白云石,其持续风化分解释碱可维持尾矿渗滤水呈近中性,即产生NMD;(2)该尾矿中As、Cd的含量较高且迁移性强,是矿区尾矿源重金属污染的主要因子;而矿区发生尾矿源Pb、Cu污染的可能性较小。综合上述,珊瑚硅质尾矿在风化作用下伴随NMD渗出,可能产生As、Cd(Zn)释放污染。因此,NMD释放尾矿/非释酸尾矿也具有产生重金属污染的危险,不容忽视。

Pollution of heavy metals associated with neutral mine drainage(NMD) is easy to be ignored. This paper focused on siliceous tailings, which were produced by milling W-Sn quartz vein type ore in Shanhu mine. Through assessing the neutralization capacity of the tailings and the risk of heavy metals(Cd, Zn, Pb, Cu and As) released from the tailings, using the methods such as acid-base accounting, geological accumulation index, potential ecological risk index, as well as elements mobility(elements exchangeable fraction), the results demonstrate that:(1) Neutralization capacity of the siliceous tailings mine is remarkable(average NPR =4.74, NAPP =-41.2 kg H 2SO 4/t), and total sulfur content in the tailings is low(average TS=0.60%). It is inferred that the tailings may not cause the risk of acid mine drainage, and the tailings should be classitied as non-acidification tailings. Calcite and dolomite are main neutralization materials in the tailings. These minerals sustained to be decomposed and release alkali which can make percolation water near to neutral, namely NMD.(2) Along with NMD, Cd, As and Zn from the tailings are main factors in pollution of Shanhu mine district, because their high concentration and strong mobility. The possibility of Pb, Cu pollution is lower in the district. Based on this study, it may not be ignored that the siliceous tailings release neutral mine drainage, and is a risk of Cd, As and Zn pollution.