| 摘要: |
| 砷、锑是地热水中的典型有害组分，受地热水独特水化学条件影响，常呈现与其他类型天然水体相异的形态分布特征。本文以西藏阿里的朗久、曲色涌巴、门士、莫落江等地热区为研究区，分析了含硫化物地热水中砷、锑在竞争巯基化过程影响下的形态分布特征。受富砷、锑岩浆流体输入或高温条件下热储围岩加强淋滤的影响，上述地热区排泄的地热水中砷、锑浓度范围分别可达5833~20750 μg/L和579~2129 μg/L。地热水中砷以亚砷酸盐和砷酸盐为主要存在形态，但同时存在占总砷百分比在0.1%~55.1%之间的硫代砷酸盐；与砷的情况不同，地热水中锑检测出的形态均为亚锑酸盐和/或锑酸盐，所有样品中均未检出硫代锑酸盐。考虑到相当一部分地热水样品的S/Sb摩尔比在理论上满足硫代锑酸盐的形成条件，且所有样品中砷的富集程度均不同程度高于锑，我们认为地热水中锑的含氧络阴离子的巯基化过程受到了共存砷的强烈抑制。在硫化物相对于砷、锑总量并不充分盈余的情况下，砷的竞争巯基化是控制地热水中硫代锑酸盐形成的最重要因素。本工作及其研究结果有助于深入理解西藏地热水环境中砷、锑的环境地球化学行为。 |
| 关键词: 地热水 形态分布 硫代砷酸盐 硫代锑酸盐 竞争巯基化 西藏 |
| DOI：10.19826/j.cnki.1009-3850.2023.05002 |
| 相关附件： 20221230003-詹海鹏-附表.pdf |
| 投稿时间：2022-12-30修订日期：2023-05-02 |
| 基金项目:国家自然科学基金项目（No. 42077278、No. 42277188） |
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| Speciation of arsenic and antimony in geothermal water affected by their competitive hiolation: A case study in several typical Ali hydrothermal areas, Tibet |
| ZHAN Haipeng, GUO Qinghai |
| (Key Laboratory of Deep Geothermal Resources, MNR & School of Environment Studies, China University of Geosciences, Wuhan 430074, China) |
| Abstract: |
| Arsenic and antimony are typical harmful constituents in geothermal water, in which they usually show different speciationfrom other types of natural waters, as a result of the unique hydrochemical conditions there. With the Langjiu, Quseyongba, Menshi and Moluojiang geothermal areas in Ali, Tibet asthe study areas,, the arsenic and antimony speciation in the sulfide-bearing geothermal waters under the influence of competitive thiolation between their oxyanions was investigated. Owing toinput of arsenic- and antimony-rich magmatic fluids and/or enhanced leaching of reservoir hostrocks at elevated temperature, the arsenic and antimony concentrations in the geothermal waters discharged from the sehydrothermal areas range from 5833 to 20750 μg/L and from 579 to 2129 μg/L, respectively. Arsenite and arsenate are the main species of arsenic in the geothermal waters, but thioarsenates exist as well with their proportions in total arsenic ranging from 0.1 to 55.1%. Different from arsenic, the species of antimony in all the geothermal water samples are antimonite and/or antimonatewith thioantimonates being undetected. Considering that the S/Sb molar ratios of a large part of the geothermal waters are high enough for formation of thioantimonates and that arsenic in all the samples is more enriched than antimony to varying degrees, we concluded that thiolation of antimony oxyanions in the geothermal waters was strongly inhibited by coexisting arsenic oxyanions. Provided that there were no a large excess of sulfide over the sum of arsenic and antimony in geothermal water, competitive thiolation of arsenic oxyanions would be the most critical factor impeding formation of thioantimonates. The present work and the results obtained in this study would be helpful for an in-depth understanding of the environmental geochemical behaviour of arsenic and antimony in geothermal water environments in Tibet. |
| Key words: Geothermal water Speciation Thioarsenates Thioantimonates Competitive thiolation Tibet |
