Examination of arsenic speciation in sulfidic solutions using X-ray absorption spectroscopy.
Examination of arsenic speciation in sulfidic solutions using X-ray absorption spectroscopy.
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DOI：
10.1021/es071858s
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发表时间：
2008-03
影响因子：
11.4
通讯作者：
D. Beak;R. Wilkin;R. Ford;S. Kelly
中科院分区：
文献类型：
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作者：
D. Beak;R. Wilkin;R. Ford;S. Kelly
硫代亚砷酸盐和硫代砷酸盐已被证明存在于硫化物沃茨中，但有不确定性的地球化学条件，这些砷物种的形成。本研究的目的是使用先进的光谱技术，形态建模，和色谱法来阐明砷的化学形态的硫化物溶液中最初含有亚砷酸盐和硫化物。X射线吸收光谱（XAS）的结果表明，实验溶液中含有砷和硫代亚砷酸盐的混合物，随着硫化物浓度的增加，砷上的氧被硫取代。实验样品显示没有证据表明聚合砷物种，或硫代亚砷酸盐转化为硫代砷酸盐。使用XAS测量的砷形态是类似的预测从热力学模型砷形态，不包括硫代砷酸盐物种在硫化物系统。在砷氧化态无法独立验证的情况下，我们的数据对色谱法测定天然沃茨中硫代砷酸盐和硫代亚砷酸盐（或混合物）的应用产生了一些疑问。硫代砷酸盐的相同色谱峰位置可以用硫代砷酸盐物种来解释。此外，样品稀释显示会改变物质分布，在色谱分析前应注意避免样品稀释。
Both thioarsenites and thioarsenates have been demonstrated to exist in sulfidic waters, yet there is uncertainty regarding the geochemical conditions that govern the formation of these arsenic species. The purpose of this research was to use advanced spectroscopy techniques, speciation modeling, and chromatography to elucidate the chemical speciation of arsenic in sulfidic solutions initially containing arsenite and sulfide. Results of X-ray absorption spectroscopy (XAS) show that experimental solutions contained mixtures of arsenite and thioarsenites with increasing substitution of sulfur for oxygen on arsenic as the sulfide concentration increased. Experimental samples showed no evidence of polymeric arsenic species, or transformation of thioarsenites to thioarsenates. The arsenic speciation measured using XAS was similar to predictions obtained from a thermodynamic model for arsenic speciation, excluding thioarsenate species in sulfidic systems. Our data cast some doubt on the application of chromatographic methods for determining thioarsenates and thioarsenites (or mixtures) in natural waters in cases where the arsenic oxidation state cannot be independently verified. The same chromatographic peak positions proposed for thioarsenates can be explained bythioarsenite species. Furthermore, sample dilution was shown to change the species distribution and care should be taken to avoid sample dilution prior to chromatographic analysis.