Molecular evidence for abiotic sulfurization of dissolved organic matter in marine shallow hydrothermal systems
Molecular evidence for abiotic sulfurization of dissolved organic matter in marine shallow hydrothermal systems
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DOI：
10.1016/j.gca.2016.06.027
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发表时间：
2016-10-01
影响因子：
5
通讯作者：
Buehring, Solveig I.
中科院分区：
文献类型：
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作者：
Gomez-Saez, Gonzalo V.;Niggemann, Jutta;Buehring, Solveig I.
浅海底热液系统是在热的还原流体和冷的含氧海水的界面处具有强氧化还原梯度的极端环境。与周围的海水相比，热液流体通常缺乏硫酸盐，并且可能含有高浓度的硫化氢（H2S）。众所周知，硫以其各种氧化态在有机物的加工和转化中起着重要作用。然而，溶解的有机硫（DOS）在水热系统的水柱中的形成和反应性迄今为止还没有很好的理解。我们调查DOS动力学及其与物理化学环境的关系，通过研究溶解有机物（DOM）的分子组成，在三个对比鲜明的浅热液系统关闭米洛斯（东地中海），多米尼加（加勒比海）和冰岛（北大西洋）。我们采用超高分辨率傅里叶变换离子回旋共振质谱（FT-ICR-MS）从分子水平上对DOM进行了表征。分子信息得到了一般地球化学数据、定量溶解有机碳和DOS分析以及同位素测量（δ H-2、δ O-18和（FC）-C-14）的补充。与多米尼加和冰岛的主要大气流体不同，米洛斯的热液流体主要由再循环海水提供。来自米洛斯的热液流体富含H2S和DOS，如高DOS/DOC比率所示，并且仅存在于流体中的所有指定DOM分子式中>90%含有硫。在所有三个系统中，来自热液流体的DOS的平均O/C比（0.26-0.34）低于周围的表面海水DOS（0.45-0.52），这表明浅热液系统作为还原DOS的来源，其可能在与含氧海水接触时被氧化。假设的硫化反应的评价表明DOM减少和硫化海水再循环过程中在米洛斯海底。四种最有效的潜在硫化反应是在式中用一个S原子交换一个O原子或等效的+ H2S反应，相应地用H2S分子交换H2O、H-2和/或O-2。我们的研究揭示了海洋热液环境中DOS动力学的新见解，并为有机硫地球化学的分子尺度机制提供了概念框架。(C)2016爱思唯尔有限公司版权所有
Shallow submarine hydrothermal systems are extreme environments with strong redox gradients at the interface of hot, reduced fluids and cold, oxygenated seawater. Hydrothermal fluids are often depleted in sulfate when compared to surrounding seawater and can contain high concentrations of hydrogen sulfide (H2S). It is well known that sulfur in its various oxidation states plays an important role in processing and transformation of organic matter. However, the formation and the reactivity of dissolved organic sulfur (DOS) in the water column at hydrothermal systems are so far not well understood. We investigated DOS dynamics and its relation to the physicochemical environment by studying the molecular composition of dissolved organic matter (DOM) in three contrasting shallow hydrothermal systems off Milos (Eastern Mediterranean), Dominica (Caribbean Sea) and Iceland (North Atlantic). We used ultra-high resolution Fourier transform ion cyclotron resonance mass spectrometry (FT-ICR-MS) to characterize the DOM on a molecular level. The molecular information was complemented with general geochemical data, quantitative dissolved organic carbon (DOC) and DOS analyses as well as isotopic measurements (delta H-2, delta O-18 and (FC)-C-14). In contrast to the predominantly meteoric fluids from Dominica and Iceland, hydrothermal fluids from Milos were mainly fed by recirculating seawater. The hydrothermal fluids from Milos were enriched in H2S and DOS, as indicated by high DOS/DOC ratios and by the fact that >90% of all assigned DOM formulas that were exclusively present in the fluids contained sulfur. In all three systems, DOS from hydrothermal fluids had on average lower O/C ratios (0.26-0.34) than surrounding surface seawater DOS (0.45-0.52), suggesting shallow hydrothermal systems as a source of reduced DOS, which will likely get oxidized upon contact with oxygenated seawater. Evaluation of hypothetical sulfurization reactions suggests DOM reduction and sulfurization during seawater recirculation in Milos seafloor. The four most effective potential sulfurization reactions were those exchanging an O atom by one S atom in the formula or the equivalent + H2S reaction, correspondingly exchanging H2O, H-2 and/or O-2 by a H2S molecule. Our study reveals novel insights into DOS dynamics in marine hydrothermal environments and provides a conceptual framework for molecular-scale mechanisms in organic sulfur geochemistry. (C) 2016 Elsevier Ltd. All rights reserved.