Li Jinwen, Chen Nan, Rajan Ivy, Sun Zhehua, Wu Huiming, Chen Diyun, Kong Lingjun
School of Environmental Science and Engineering, Guangzhou University, Guangzhou, 510006, China.
Global ARD Testing Services Inc., Burnaby, Canada.
Environ Sci Pollut Res Int. 2017 May;24(13):12212-12219. doi: 10.1007/s11356-017-8809-8. Epub 2017 Mar 28.
Identifying and revealing the geochemical behaviour of Tl during mine waste weathering are very important to assess the potential environmental impact of Thallium (Tl) from open mine-waste piles. Herein, two methods including the modified BCR sequential extraction and the long-term humidity cell tests (HCT) were employed to understand the Tl chemical fractions and to stimulate intense chemical weathering process, respectively. The results from BCR sequential extraction showed that the Tl concentration in the studied sample was 18.78 mg/kg, containing 1.878 mg/kg oxidisable, 0.282 mg/kg acid exchangeable and 1.596 mg/kg reducible Tl. The acid exchangeable fraction contributed to a particular potential risk to the aquatic marine life in the early stages and the Fe/Mn oxidisable fraction posed a potential risk being dissolved into solution at low pH (i.e. acidic conditions). The variations of Tl concentration in leachates were classified as two period as the pH values decrease. In the first period, the Tl concentrations decreased positively with pH value with poor correlation between pH value and SO concentration in leachates. Drastic release of Tl was observed in the early period once the material was exposed to air and water, being ascribe to the acid exchangeable fraction bound to carbonate as dissolved by acid. During the second period, three increased peaks of Tl concentration (11.02, 16.03, 43.15 μg/L) and four increased peaks of SO concentration (315, 390, 899.61 and 2670 mg/L) were observed. A good correlation (R = 0.8384) between the concentrations of Tl and SO was observed, indicating the Tl was mainly released from the oxidation of sulphide.
识别和揭示矿山废弃物风化过程中铊（Tl）的地球化学行为对于评估露天矿废弃物堆中铊对环境的潜在影响至关重要。在此，分别采用改进的BCR顺序萃取法和长期湿度单元试验（HCT）来了解铊的化学形态，并模拟强烈的化学风化过程。BCR顺序萃取结果表明，研究样品中铊的浓度为18.78 mg/kg，其中可氧化态铊为1.878 mg/kg，酸交换态铊为0.282 mg/kg，可还原态铊为1.596 mg/kg。酸交换态部分在早期对水生海洋生物构成特殊潜在风险，而铁/锰氧化态部分在低pH值（即酸性条件）下有溶解到溶液中的潜在风险。随着pH值降低，渗滤液中铊浓度的变化分为两个阶段。在第一阶段，铊浓度随pH值呈正相关下降，渗滤液中pH值与硫酸根浓度之间相关性较差。一旦材料暴露于空气和水中，早期会观察到铊的急剧释放，这归因于与碳酸盐结合的酸交换态部分被酸溶解。在第二阶段，观察到铊浓度有三个增加的峰值（11.02、16.03、43.15 μg/L）和硫酸根浓度有四个增加的峰值（315、390、899.61和2670 mg/L）。观察到铊和硫酸根浓度之间有良好的相关性（R = 0.8384），表明铊主要从硫化物的氧化中释放出来。
