Formation and structural characterization of thioantimony species and their natural occurrence in geothermal waters.
Formation and structural characterization of thioantimony species and their natural occurrence in geothermal waters.
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DOI：
10.1021/es201003k
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发表时间：
2011-07
影响因子：
11.4
通讯作者：
B. Planer-Friedrich;Andreas C Scheinost
中科院分区：
文献类型：
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作者：
B. Planer-Friedrich;Andreas C Scheinost
以前通过实验室研究推测，现在可以使用阴离子交换层析-电感耦合等离子体质谱来证明地热水中存在锑硫物种。根据S/Sb比值和X射线吸收光谱的结构表征，将AEC-ICPMS检测到的两种硫代锑物种归属为三硫代锑和四硫代锑。X-射线光电子能谱证实，在低氧条件下，硫化物过量10倍的闪锌矿形成的初始物种是三硫代锑矿。三硫代锑在氧气存在下迅速转化为四硫代锑酸盐，或在过量的OH(-)与SH(-)浓度下转变为锑，并逃避层析检测。在天然地热水中检出高达30%的三硫代锑酸盐和9%的四硫代锑酸盐。PH值越高，硫化物浓度越高，氧浓度越低，它们的发生率越高。考虑到硫化物的大量过剩(100到10,000倍)，在自然条件下形成的硫代锑酸盐的比例低于合成溶液的预期。再加上观察到的高硫代砷酸盐浓度(占总砷的80%)，这表明在与砷直接竞争有限的硫化物来源时，硫代锑酸盐比硫代砷酸盐更少自发形成。因此，砷和锑与硫的相互作用可能对它们的环境行为的相似或不同起决定性作用。
Previously postulated from laboratory studies, the occurrence of antimony-sulfur species in geothermal waters could now be proven using anion-exchange chromatography-inductively coupled plasma-mass spectrometry. The two thioantimony species detected by AEC-ICP-MS in oxic synthetic antimonite-sulfide solutions were assigned to tri- and tetrathioantimonate based on their S/Sb ratios and structural characterization by X-ray absorption spectroscopy (XAS). XAS confirmed that the initial species formed under anoxic conditions from antimonite at a 10-fold sulfide excess is trithioantimonite. Trithioantimonite rapidly transforms to tetrathioantimonate in the presence of oxygen or to antimonite at excess OH(-) versus SH(-) concentrations, and escapes chromatographic detection. In natural geothermal waters, up to 30% trithioantimonate and 9% tetrathioantimonate were detected. Their occurrence increased at increasingly alkaline pH and with increasing sulfide and decreasing oxygen concentrations. Considering the large sulfide excess (100 to 10,000-fold) the proportion of thioantimonates formed under natural conditions is lower than expected from synthetic solutions. Together with the observed high thioarsenate concentrations (>80% of total arsenic), this indicates that in direct competition with arsenic for a limited source of sulfide, thioantimonates form less spontaneously than thioarsenates. Interactions of arsenic and antimony with sulfur can therefore be decisive for similarities or differences in their environmental behavior.