Thioarsenates in geothermal waters of yellowstone national park:: Determination, preservation, and geochemical importance
Thioarsenates in geothermal waters of yellowstone national park:: Determination, preservation, and geochemical importance
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DOI：
10.1021/es070273v
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发表时间：
2007-08-01
影响因子：
11.4
通讯作者：
Wallschlaeger, Dirk
中科院分区：
文献类型：
--
作者：
Planer-Friedrich, Britta;London, Jacqueline;Wallschlaeger, Dirk
用阴离子交换层析-电感耦合等离子体质谱分析了黄石国家公园地热水中的一、二、三、四硫代砷酸根离子，以及甲基化的砷氧阴离子和硫代阴离子。保留时间与合成标准相符，测量的S：砷的比例，以及分子电喷雾质谱图支持鉴定。酸化不适合硫化水体中砷的形态保存，加入盐酸可能会导致总溶解砷的损失，这可能是由于砷-硫化物的沉淀。闪速冷冻是砷保存数周的首选方法。解冻后，样品必须立即进行分析。硫代砷酸盐在地热水中的pH值范围为2.1至9.3。它们显然在碱性条件下占主导地位(高达总砷的83%)，但在酸性水中也检测到一硫代砷(高达34%)。沿排水渠道的动力学研究表明，硫代砷酸盐对硫化物温泉中排出的砷的去向具有重要意义。观察到的砷形态变化表明有三个独立的反应：三硫代砷酸盐向亚砷酸盐的转化(主要初始反应)，三通过二硫代砷酸盐和一硫代砷酸盐向亚砷酸盐的逐步配体交换(次要反应)，以及亚砷酸盐的氧化成砷酸盐，只有在硫代砷酸盐消失后，这一反应才变得定量重要。
Mono-, di-, tri-, and tetrathioarsenate, as well as methylated arsenic oxy- and thioanions, were determined besides arsenite and arsenate in geothermal waters of Yellowstone National Park using anion-exchange chroma tography inductively coupled plasma mass spectrometry. Retention time match with synthetic standards, measured S:As ratios, and molecular electrospray mass spectra support the identification. Acidification was unsuitable for arsenic species preservation in sulfidic waters, with HCl addition causing loss of total dissolved arsenic, presumably by precipitation of arsenic-sulfides. Flash-freezing is preferred for the preservation of arsenic species for several weeks. After thawing, samples must be analyzed immediately. Thioarsenates occurred over a pH range of 2.1 to 9.3 in the geothermal waters. They clearly predominated under alkaline conditions (up to 83% of total arsenic), but monothioarsenate also was detected in acidic waters (up to 34%). Kinetic studies along a drainage channel showed the importance of thioarsenates for the fate of arsenic discharged from the sulfidic hot spring. The observed arsenic speciation changes suggest three separate reactions: the transformation of trithioarsenate to arsenite (major initial reaction), the stepwise ligand exchange from tri- via di- and monothioarsenate to arsenate (minor reaction), and the oxidation of arsenite to arsenate, which only becomes quantitatively important after thioarsenates have disappeared.