School of Earth and Environmental Sciences, Schmid College of Science and Technology, Chapman University , One University Drive, Orange, California 92866, United States.
Environ Sci Technol. 2013 Aug 6;47(15):8164-71. doi: 10.1021/es4010653. Epub 2013 Jul 26.
The chemical speciation and distribution of potentially toxic metal(loid)s in mine wastes is critical to assessing the risks posed by these wastes and predicting the potential bioavailability of the metal(loid)s present. Of additional potential importance is the role of particle size in the fate, transport, and toxicity of contaminated mining materials. Spectroscopic analyses of size-separated mine tailings and adjacent background samples from the Randsburg Historic Mining District, California were conducted to quantify the speciation and distribution of arsenic (As) as a function of particle size. Micro-X-ray fluorescence (μXRF) mapping of separate size fractions was used to identify multiple populations of particles with different As:Fe ratios, indicating a variety of distinct arsenic-bearing species. Bulk extended X-ray absorption fine structure (EXAFS) spectroscopy identified phases including arseniosiderite, Ca2Fe3(3+)(AsO4)3O3·3H2O, and As(V) sorbed to iron hydroxides (ferrihydrite, goethite), confirming a strong statistical correlation between arsenic and iron observed in both μXRF studies and bulk chemical analyses. Differences in As speciation between the mine tailings and background samples also suggest that weathering of crystalline As-bearing phases in tailings leads to sorption of dissolved arsenic to iron hydroxides in nontailings background material.
对矿山废物中潜在有毒金属（类）的化学形态和分布进行研究，对于评估这些废物所带来的风险以及预测其中金属（类）的潜在生物可利用性至关重要。此外，颗粒大小在受污染采矿材料的命运、迁移和毒性方面也具有潜在的重要作用。对加利福尼亚州兰兹堡历史矿区的大小分离的矿山尾矿和相邻背景样本进行了光谱分析，以定量研究砷（As）的形态和分布随粒径的变化。利用微 X 射线荧光（μXRF）对不同粒径的单独部分进行测绘，确定了具有不同 As:Fe 比的多种颗粒群体，表明存在多种不同的含砷物种。扩展 X 射线吸收精细结构（EXAFS）光谱的批量分析确定了包括砷铁矿、Ca2Fe3(3+)(AsO4)3O3·3H2O 和吸附在铁氢氧化物（水铁矿、针铁矿）上的 As(V)在内的多个相，这证实了 μXRF 研究和批量化学分析中观察到的砷和铁之间存在强烈的统计相关性。尾矿和背景样本之间的砷形态差异也表明，尾矿中含结晶砷相的风化会导致溶解的砷吸附到非尾矿背景材料中的铁氢氧化物上。
