摘要:
贵州丹寨金汞矿在开采期间,将大量的废渣露天堆放在环境中,这些尾渣不仅含有金,还含有有毒有害重金属汞和砷。本文研究丹寨尾渣中汞和砷的淋出特征以及矿区周边土壤、农作物和地表水汞砷分布特征,并通过尾渣中金含量来评估利用植物提取技术来回收金的可能性。研究结果表明,利用0.1mol·L-1 NaH2 PO4和0.1 mol·L-1 Na2 HPO4(3:2 V/V)的混合溶液淋洗尾渣,淋滤出的砷含量达到9 929.8 μg·L-1;利用0.1 mol·L-1 CH3 COONH4溶液淋洗尾渣,淋滤液汞含量达到12.12 μg·L-1。矿区周边土壤总汞含量和总砷含量分别为11.5~79.7 mg·kg-1和23.7~356.5 mg·kg-1,利用污染程度法和尼梅罗综合污染指数发对其Hg和As污染程度进行了评价,结果显示土壤汞污染严重,污染因子高达10.5~78.7;尼梅罗综合污染指数为62.97;同时该土壤还受到严重的As污染,除了其中一个样点的As污染程度小于0属于未超标,其它样点As污染程度均大于0;尼梅罗综合污染指数为13.41。农作物中总汞含量和总砷含量均超过国家食品卫生限量标准,分别是《食品安全国家标准》(GB2762-2012)中所允许最大总汞和最大总砷的10~1 150倍和1.6~7.4倍。位于尾渣堆放点上游的地表水中总汞和总砷浓度分别为102.4 ng·L-1和2 262.1 ng·L-1,流经尾渣堆后,浓度大幅度增加,分别为160.3 ng·L-1和11 571.8 ng·L-1,说明丹寨尾渣可能是潜在的汞和砷污染源。尾渣中金含量为0.54 g·t-1,可以探索利用植物提取技术来回收尾渣中的金。
关键词:
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丹寨
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汞
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砷
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分布特征
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潜在风险
Abstract:
Mercury (Hg) and gold (Au) mine in Guizhou, Danzhai is a typical Carlin-type gold mine which is associated with Au, Hg and As (Arsenic). The slag stacked on the ground during the mining operation, and it contented not only Au but also Hg and As, the Hg and As were regarded as the toxic heavy metals. This paper focused on the characteristic of leachable Hg and As, and the distribution of Hg and As in the surface water, soil and crop in mining area. And it also evaluated the possibility of using plant extraction technology to refine Au in the slag. The results showed that the slag was washed by the mixed solution of 0.1 mol·L-1 NaH2 PO4 and 0.1mol·L-1 Na2 HPO4(3:2 V/V), the concentration of As in the leachate was 9 929.8 μg·L-1; When washed by solution of 0.1 mol·L-1 CH3 COONH4, the Hg concentration in the leachate was 12.12 μg·L-1. The total concentration of Hg (THg) in the soil of Danzhai ranged from 11.5 and 79.7 mg·kg-1 and As (TAs) ranged from 23.7 and 356.5 mg ·kg-1, respectively. According to contamination degree and N. L. Nemerow, the assessment of Hg and As pollution showed that the situation of soil pollution is serious. The pollution factors are between 10.5 and 78.7 and the Newmerow comprehensive pollution index is 62.97. In addition, the As pollution factors are greater than 0 except one sample and the Newmerow comprehensive pollution index is 13.41. Both the content of THg and TAs of the crop exceeds the quality and safety standard national agricultural products and they are 10~1 150 times and 1.6~7.4 times the permissible range. The concentration of THg and TAs in the upstream surface water of the slag heap is 102.4 ng·L-1 and 2 262.1 ng·L-1, and increased to 160.3 ng·L-1 and 11 571.8 ng·L-1 respectively in the downstream surface water. The content of Au in the slag is 0.54 g·t-1, indicated that the phytomining may explore the recovery of the gold from the slag in the future.
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