大兴安岭古利库砂金矿废弃地土壤重金属含量特征

Characteristics of soil heavy metals concentrations in the tailings of Guliku placer gold mine in the Greater Khingan Mountains

矿产资源开采后形成大量废弃地已经成为土壤重金属污染主要来源之一。大兴安岭地区是我国砂金矿重要分布区,近百年的开采历史导致该地区遗留大面积的砂金矿采矿废弃地。然而,目前关于大兴安岭砂金矿废弃地土壤重金属污染情况的研究鲜见报道。本文以大兴安岭地区古利库砂金矿废弃地为对象,研究了砂金矿废弃地土壤重金属元素Hg、As、Pb、Cd和Cr的污染情况及分布特征,并采用内梅罗指数进行土壤重金属元素综合污染等级评价。结果发现:(1)与大兴安岭天然林相比,砂金矿废弃地土壤As、Cd和Cr含量分别增加83%、78%和101%;(2)在砂金矿废弃地不同位置,土壤Hg和Pb含量存在差异,而As、Cd和Cr含量差异不显著;(3)砂金矿废弃地土壤Hg、As、Pb、Cd和Cr含量均低于我国土壤环境质量一级标准值,土壤重金属污染综合评价等级未达到轻度污染等级。研究表明,大兴安岭砂金矿废弃地土壤重金属污染并不严重,今后在该地区砂金矿废弃地生态恢复建设中应该重点考虑土壤水分或养分限制问题。

Mine tailings have become the potential sources of soil heavy metals contaminations. There are large areas of mine tailings in the Greater Khingan Mountains where is one of the most important distribution regions of placer gold mine in China because of nearly a century of mining activities. However, few studies have assessed the characteristics of soil heavy metals contamina- tions in the tailings of placer gold mine in this region. In this study, we investigated soil Hg, As, Pb, Cd and Cr concentrations and their distribution in the tailings of Guliku placer gold mine. Moreover, soil pollution risk was evaluated using Nemerow index. We found that： （1） soil As, Cd and Cr concentrations increased significantly by 83% , 78% and 101% in the tailings of plac- er gold mine as compared to natural forest soil. （2） soil Hg and Pb concentrations were different among sampling locations, but not for soil As, Cd and Cr. （3） soil Hg, As, Pb, Cd and Cr concentrations were all lower than the first-grade environmental quality standards for soils （GB 15618-1995 ） of China. Our results implied that soil heavy metals contaminations in the tailings of placer gold mine in the Greater Khingan Mountains were not serious. Therefore, we should pay more attention to soil water or nutrient limit rather than soil heavy metals contaminations during ecological restoration of placer gold mine tailings in the Greater Khingan Mountains.