Sulfur, iron-, and calcium cycling associated with natural electric currents running through marine sediment
Sulfur, iron-, and calcium cycling associated with natural electric currents running through marine sediment
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DOI：
10.1016/j.gca.2012.05.036
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发表时间：
2012-09-01
影响因子：
5
通讯作者：
Nielsen, Lars Peter
中科院分区：
文献类型：
--
作者：
Risgaard-Petersen, Nils;Revil, Andre;Nielsen, Lars Peter
最近发现，穿过海洋沉积物的自然电流将表层的氧还原与深层缺氧层的硫化物氧化结合起来。在这里，我们表明这种氧化和还原过程的空间分离导致非常规的硫、铁和钙的动员和重新分配。将还原后的海洋沉积物与上覆的含氧水孵育，在45-150天后分析溶质和固体的垂直分布。高达44%的沉积物耗氧量是由电流驱动的，硫化物电氧化为硫酸盐，同时产生质子，导致沉积物缺氧层中硫化铁和碳酸钙的大量溶解。大部分被动员的铁扩散到氧化带，在那里形成氧化铁矿物。钙在氧区以镁方解石的形式析出。因此，遥远地区生物地球化学过程的电耦合在海洋沉积物中产生了独特的化学条件，其中关键元素被动员和重新安置，可能还有微量元素和营养物质。我们认为，这种电耦合的生物地球化学在短暂的氧耗尽后在海洋沉积物中蓬勃发展，在地质记录中留下了这种事件的明显特征。(C) 2012 Elsevier Ltd.版权所有。
Natural electric currents running through marine sediments have recently been found to couple oxygen reduction at the surface to sulfide oxidation in deeper anoxic layers. Here we show that such spatial separation of oxidation and reduction processes causes non-conventional sulfur, iron, and calcium mobilization and reallocation. Reduced marine sediment was incubated with overlying oxic water and the vertical distribution of solutes and solids was analyzed after 45-150 days. As much as 44% of sediment oxygen consumption was driven by electric currents, and electrogenic oxidation of sulfide to sulfate with concurrent proton generation resulted in significant dissolution of iron sulfides and calcium carbonates in the anoxic layers of the sediment. Most of the mobilized iron diffused to the oxic zone where it formed oxidized iron minerals. Calcium precipitated in the oxic zone as magnesium-calcite. The electric coupling of biogeochemical processes in distant regions thus generates unique chemical conditions in marine sediments whereby key elements are mobilized and relocated, probably along with trace elements and nutrients. We suggest that such electrically coupled biogeochemistry flourishes in marine sediments after transient oxygen depletion, leaving distinct signatures of such events in the geological record. (C) 2012 Elsevier Ltd. All rights reserved.