Environmental Geochemistry, University of Bayreuth, Universitaetsstrasse 30, 95440 Bayreuth, Germany.
Environ Sci Technol. 2011 Aug 15;45(16):6855-63. doi: 10.1021/es201003k. Epub 2011 Jul 21.
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.
先前从实验室研究中推断出，现在可以使用阴离子交换色谱-电感耦合等离子体质谱法来证明地热水中锑-硫物种的存在。AEC-ICP-MS 在有氧合成亚锑酸盐-硫化物溶液中检测到的两种硫代锑物种，根据它们的 S/Sb 比值和 X 射线吸收光谱（XAS）的结构特征，被分配到三价和四价硫代锑酸盐。XAS 证实，在缺氧条件下，从亚锑酸盐在硫化物过量 10 倍的情况下形成的初始物质是三硫代锑酸盐。三硫代锑酸盐在有氧或过量 OH(-)与 SH(-)浓度的情况下迅速转化为四硫代锑酸盐，并逃避色谱检测。在天然地热水中，检测到高达 30%的三硫代锑酸盐和 9%的四硫代锑酸盐。它们的出现随着 pH 值的增加、硫化物浓度的增加和氧浓度的降低而增加。考虑到大量的硫化物过剩（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中的预期。再加上观察到的高硫代砷酸盐浓度（总砷的>80%），这表明在与砷直接竞争有限的硫化物来源时，硫代锑酸盐的形成不如硫代砷酸盐自发。因此，砷和锑与硫的相互作用可以决定它们在环境行为上的相似性或差异性。
