Abiotic formation of dissolved organic sulfur in anoxic sediments of Santa Barbara Basin
Abiotic formation of dissolved organic sulfur in anoxic sediments of Santa Barbara Basin
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DOI：
10.1016/j.orggeochem.2019.05.009
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发表时间：
2020-01-01
影响因子：
3
通讯作者：
Komada, Tomoko
中科院分区：
文献类型：
--
作者：
Abdulla, Hussain A.;Burdige, David J.;Komada, Tomoko
硫化作用已被发现能促进海洋沉积物中有机质的保存和石油的形成。然而，我们对硫化机理还没有一个全面的了解。在这项研究中，我们研究了加州边境地区圣巴巴拉盆地（SBB）缺氧沉积物顶部4.5 m中溶解有机硫（DOS）形成的几种可能机制。利用傅里叶变换离子回旋共振质谱（FTICR-MS），我们确定了这些DOS化合物的潜在溶解有机物（DOM）前体的化学式。我们还研究了非生物形成的DOS的公式如何随着深度在主要氧化还原梯度上的变化而变化。结果表明，亚硫酸氢化物（HS）和多硫化物（HSx）的非生物亲核加成反应是SBB沉积物缺氧孔隙水中形成DOS的主要硫化途径。在2203个DOM公式中加入HS和HSx可生成2124个独特的DOS公式，占这些孔隙水中检测到的DOS公式的70%左右。在非生物硫化反应中作为反应物的DOM分子式中，我们发现64%的分子式仅含有碳、氢和氧（CHO分子式），而其余的（34%）含有氮（DON分子式）。我们的研究结果表明，许多具有H/C和O/C元素比与富含羧基脂环分子（CRAM）重叠的CHO和DON分子式具有高的硫化反应性。这类特殊的分子式可能在硫化物海洋生态系统中有机硫化合物的形成和海洋沉积物中含硫原干酪根的形成中发挥重要作用。我们的研究结果进一步表明，缺氧沉积物是海洋中DOS化合物的来源。Elsevier Ltd.出版。
Sulfurization has been found to enhance organic matter preservation and petroleum formation in marine sediments. However, we do not yet have a comprehensive understanding of sulfurization mechanisms. In this study, we investigated several possible mechanisms of dissolved organic sulfur (DOS) formation in the top 4.5 m of anoxic sediments of Santa Barbara Basin (SBB), California Borderland. Using Fourier Transform Ion Cyclotron Resonance Mass Spectrometry (FTICR-MS), we identified chemical formulas of potential dissolved organic matter (DOM) precursors to these DOS compounds. We also examined how the formulas of abiotically formed DOS changed as a function of depth across a major redox gradient.Results show that abiotic nucleophilic addition reactions involving bisulfide (HS) and polysulfide (HSx) are the major sulfurization pathways that form DOS in anoxic pore waters of SBB sediments. We identified 2124 unique DOS formulas that could be generated from the addition of HS and HSx to 2203 DOM formulas, and this accounted for similar to 70% of all DOS formulas detected in these pore waters. Examining the DOM formulas that served as reactants in the abiotic sulfurization reactions, we found that 64% contained only carbon, hydrogen, and oxygen (CHO formulas) while the remainder (34%) included nitrogen (DON formulas). Our results revealed high reactivity toward sulfurization among many of the CHO and DON formulas that have H/C and O/C elemental ratios that overlap with those of carboxyl-rich alicyclic molecules (CRAM). This specific class of formulas could play an important role in the formation of organic sulfur compounds in sulfidic marine ecosystems, and in the formation of sulfur-containing protokerogen in marine sediments. Our results further suggest that anoxic sediments are a source of DOS compounds to the oceans. Published by Elsevier Ltd.