The role of S−3 ion in thermochemical sulphate reduction: Geological and geochemical implications
The role of S−3 ion in thermochemical sulphate reduction: Geological and geochemical implications
复制标题
DOI：
10.1016/j.epsl.2014.04.018
复制
发表时间：
2014-06
影响因子：
5.3
通讯作者：
L. Truche;E. Bazarkina;G. Barré;E. Thomassot;G. Berger;J. Dubessy;P. Robert
中科院分区：
文献类型：
--
作者：
L. Truche;E. Bazarkina;G. Barré;E. Thomassot;G. Berger;J. Dubessy;P. Robert
热化学硫酸盐还原（TSR）在全球地壳硫循环中起着至关重要的作用，并可能影响当前和过去的硫同位素记录。然而，将在高温（200 °C以上）下测得的实验反应速率外推到较低温度，以及解释自然样品中记录的硫同位素分馏，需要准确描述控制这些反应的基本步骤。我们通过专门的实验解决了这个问题。基于situonin拉曼光谱测量，我们表明，三硫离子S− 3是主要的中间硫价物种参与非生物硫酸盐还原过程中引发的H2S，在很宽的温度范围（100-350 °C）和溶液组成，无论电子供体考虑。这里报告的原位光谱数据明确地证明了在低至100 °C的温度下S− 3的存在。S-3的存在对于实现硫酸盐的快速还原至关重要，尤其是在低温下。我们提出，任何溶解的成分，降低水的介电常数，或产生有利的S− 3配位，将稳定三硫离子（从而促进TSR）在T和pH条件下，是不那么极端比以前认为的。在讨论天然和/或实验TSR相关样品中记录的质量无关硫同位素组成时，也应该考虑S-3在这些过程中的重要性。
Thermochemical sulphate reduction (TSR) plays a crucial role in the global sulphur cycle in the Earth's crust, and may affect current and past sulphur isotopic records. However, the extrapolation of experimental reaction rates measured at high temperature (above 200 °C) towards lower temperatures, as well as the interpretation of the sulphur isotopic fractionation recorded in natural samples, require an accurate description of the elementary steps controlling these reactions. We addressed this question through dedicated experiments. Based onin situRaman spectroscopy measurements, we show that the trisulphur ion S−3is the dominant intermediate sulphur valence species involved in abiogenic sulphate reduction processes initiated by H2S, over a wide range of temperature (100-350 °C) and solution compositions, whatever the electron donor considered. Thein situspectroscopic data reported here unambiguously demonstrate the presence of S−3at temperatures as low as 100 °C. The presence of S−3is critical to achieve rapid sulphate reduction, especially at low temperature. We propose that any dissolved constituent which decreases the dielectric constant of water, or which yields favourable S−3coordination, will stabilise the trisulphur ion (thus promoting TSR) atTand pH conditions that are less extreme than previously thought. The importance of S−3in these processes should also be taken into account when discussing the mass-independent sulphur isotopic compositions recorded in natural and/or experimental TSR-related samples.