Department of Geological Sciences, University of Saskatchewan, 114 Science Place, Saskatoon, SK S7N 5E2, Canada.
Canadian Light Source Inc., University of Saskatchewan, 44 Innovation Boulevard, Saskatoon, SK S7N 2V3, Canada.
Sci Total Environ. 2017 May 15;586:753-769. doi: 10.1016/j.scitotenv.2017.02.053. Epub 2017 Feb 12.
Exposure of coal waste rock to atmospheric oxygen can result in the oxidation of sulfide minerals and the release of sulfate (SO) and associated trace elements (e.g., Se, As, Cd, and Zn) to groundwaters and surface waters. Similarly, reduced iron minerals such as siderite, ankerite, and the sulfide, pyrite, present in the waste rock can also undergo oxidation, resulting in the formation of iron oxyhydroxides that can adsorb trace elements released from the oxidation of the sulfide minerals. Characterization and quantification of the distribution of sulfide and iron minerals, their oxidation products, as well as leaching rates are critical to assessing present-day and future impacts of SO and associated trace elements on receiving waters. Synchrotron-based X-ray absorption near edge spectroscopic analysis of coal waste rock samples from the Elk Valley, British Columbia showed Fe present as pyrite (mean 6.0%), siderite (mean 44.3%), goethite (mean 35.4%), and lepidocrocite (mean 14.3%) with S present as sulfide (mean 26.9%), organic S (mean 58.7%), and SO (mean 14.4%). Squeezed porewater samples from dump solids yielded mean concentrations of 0.28mg/L Fe and 1246mg/L SO. Geochemical modeling showed the porewaters in the dumps to be supersaturated with respect to Fe oxyhydroxides and undersaturated with respect to gypsum, consistent with solids analyses. Coupling Fe and S mineralogical data with long-term water quality and quantity measurements from the base of one dump suggest about 10% of the sulfides (which represent 2% of total S) in the dump were oxidized over the past 30years. The S from these oxidized sulfides was released to the receiving surface water as SO and the majority of the Fe precipitated as secondary Fe oxyhydroxides (only 3.0×10% of the Fe was released to the receiving waters over the past 30years). Although the data suggest that the leaching of SO from the waste rock dump could continue for about 300years, assuming no change in the rate of oxidation of sulfides, SO is currently not a concern in receiving surface waters as the concentration levels are below regulatory limits.
煤矸石暴露在大气氧气中会导致硫化物矿物的氧化以及硫酸盐（SO）和相关痕量元素（如硒、砷、镉和锌）释放到地下水和地表水。同样，废石中存在的菱铁矿、铁白云石等还原态铁矿物也会发生氧化，形成铁氢氧化物，可吸附硫化物矿物氧化释放的痕量元素。硫化物和铁矿物的分布特征及数量、它们的氧化产物以及浸出率的确定，对于评估当前和未来 SO 和相关痕量元素对接收水的影响至关重要。利用同步辐射 X 射线吸收近边谱分析技术对不列颠哥伦比亚省埃尔克谷的煤矸石样品进行研究表明，Fe 主要以黄铁矿（平均 6.0%）、菱铁矿（平均 44.3%）、针铁矿（平均 35.4%）和纤铁矿（平均 14.3%）形式存在，S 主要以硫化物（平均 26.9%）、有机 S（平均 58.7%）和 SO（平均 14.4%）形式存在。从废渣中提取的压榨孔隙水样的平均浓度为 0.28mg/L 的 Fe 和 1246mg/L 的 SO。地球化学模拟表明，废渣中的孔隙水相对于铁氢氧化物处于过饱和状态，相对于石膏处于不饱和状态，这与固体分析结果一致。将 Fe 和 S 矿物学数据与一个废渣底部的长期水质和水量测量数据相结合，表明在过去 30 年中，约有 10%的（占总 S 的 2%）硫化物在废渣中发生了氧化。这些氧化的硫化物中的 S 被释放到接收的地表水作为 SO，大部分 Fe 以次生铁氢氧化物沉淀（在过去 30 年中，仅有 3.0×10%的 Fe 被释放到接收水中）。尽管数据表明，从废渣堆中浸出 SO 的过程可能会持续约 300 年，但假设硫化物氧化速率不变，目前接收地表水的 SO 浓度未达到监管限制，不会成为一个问题。
