Collaborative Research: Unraveling Molybdenum and Rhenium speciation: Identifying the burial pathways of redox proxies in sulfidic settings

合作研究：揭示钼和铼的形态：识别硫化物环境中氧化还原代理的埋藏途径

• 批准号: 1503596
• 负责人: Anthony Chappaz
• 金额: $ 6.36万
• 依托单位: Central Michigan University
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2015
• 资助国家: 美国
• 起止时间: 2015-04-01 至 2017-09-30
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1503596&HistoricalAwards=false
• 关键词: Collaborative; Research; Unraveling; Molybdenum; Rhenium

When natural waters become devoid of oxygen, dissolved sulfide is produced and can accumulate via microbial sulfate reduction. Sulfidic conditions occurred within ancient oceans, and lead to extinction events in marine biota. Redox sensitive trace metals, like molybdenum (Mo) and rhenium (Re), display contrasting chemical behavior between oxygenated and sulfidic waters and therefore can be used as tools to enhance our understanding of the Earth's oxygenation history and the evolution of life. Oxygen depletion also occurs within modern oceans, probably as a result of anthropogenically-induced eutrophication. Such conditions have been observed globally, predominately in coastal areas, and have become a major environmental issue leading to massive fish kills. Thus, in addition to providing information on how and when the rise of oxygen (approximately ­2.4 billion years ago) in Earth's atmosphere facilitated the development of life, Mo and Re can contribute to assessing and preventing the development of oxygen-depleted zones within modern oceans. However, to fully exploit Mo and Re as indicators of oxygen-depleted conditions, the chemical transformations these metals undergo in sulfidic waters must be well defined, as well as the mechanisms governing their ultimate burial. Filling these gaps in knowledge is the backbone of this study as well as the future work it will spawn. In response, a two-pronged study has been initiated. (1) Quantify actual Mo and Re speciation in natural sulfidic waters utilizing our recently developed chromatographic method (reverse phase ion pair chromatography: RP-IPC). Investigators aim to (a) couple their present RP-IPC method with ICP-MS, (b) utilize RP-IPC-ICP-MS to quantify individual thiomolybdate and thioperrhenate anions in the water column of Green Lake (New York, USA), a lake characterized by a permanent chemocline and (c) quantify any stable Mo or Re isotopic fractionations during transitions among thiomolybdates and thioperrhenates. (2) Survey the role FeMoS cubane clusters play in the ultimate burial of Mo and Re under euxinic conditions. They will (a) produce and analyze solutions comprising an array of initial Fe, Mo, sulfide, ionic strength, and pH conditions as well as trace quantities of Re, and (b) use X-Ray Absorption Fine Structure (XAFS) spectroscopy to characterize any FeMoS solid produced in the test solutions. The impact of this study will extend widely. Five outcomes stand out most clearly: (1) Support the geoscientific community studying biospheric evolution. (2) Provide a new method for quantifying thiometallate speciation and isotopic fractionation. (3) Involve several undergraduate researchers from underrepresented minorities in all facets of the proposed research. (4) Train a Ph.D. student as a part of an international collaboration. (5) Communicate research results at appropriate conferences, as well as submit several scientific articles to disseminate findings.

当天然水无氧时，会产生溶解的硫化物，并可以通过减少微生物硫酸盐的减少来积累。硫磺状况发生在古老的海洋内，并导致海洋生物群的延伸事件。氧化还原敏感的痕量金属（如钼（MO）和rhenium（Re））在氧化和硫酸水之间显示出对比的化学行为，因此可以用作增强我们对地球氧合历史和生命进化的理解的工具。氧气部署也可能是由于人为引起的富营养化而导致的。在沿海地区，在全球范围内观察到了这种情况，并已成为导致大规模鱼类杀戮的主要环境问题。除了提供有关地球大气中氧气的兴起（大约24亿年前）如何以及何时提供的信息，还支持了生命的发展，MO和RE还可以促进和防止现代海洋内氧气耗尽的区域的发展。但是，为了完全利用氧气耗尽条件的指标，必须很好地定义这些金属的化学转化，以及控制其最终埋葬的机制。在知识中填补这些空白是这项研究的骨干，以及它将产生的未来工作。作为响应，已经开始了一项两管沟的研究。 （1）使用我们最近开发的色谱法（反相离子对色谱法：RP-IPC）来量化实际的MO和尊重。研究人员的目的是（a）将目前的RP-IPC方法与ICP-MS相结合，（b）利用RP-IPC-IPC-ICP-MS来量化Green Lake（纽约）水柱（纽约）水柱中的单个硫代苯甲酸酯和硫代苯甲酸酯（纽约）（美国）的thioperrhenate阴离子，以永久性化学量和（c）量化iSopicic Moopicic thripitions和（c）在湖中进行了量子，并在（c）中量化了（c）。硫代甲酸盐。 （2）调查Femos Cubane群集在莫和在优质条件下的最终埋葬中所扮演的角色。他们将（a）生产和分析溶液完成初始Fe，MO，硫化物，离子强度和pH条件以及痕量RE的阵列，以及（b）使用X射线吸收良好结构（XAFS）光谱，以表征测试溶液中产生的任何FEMOS固体。这项研究的影响将广泛扩展。五个结果最清楚地脱颖而出：（1）支持研究生物圈进化的地球科学社区。 （2）提供了一种量化硫代表规范和同位素分馏的新方法。 （3）涉及拟议研究各个方面的几位本科生研究人员。 （4）训练博士学位学生作为国际合作的一部分。 （5）在适当的会议上进行研究结果，并提交几篇科学文章以传播发现。