Critical new perspectives on molybdenum cycling under modern and experimental euxinic conditions: Tuning the paleoredox proxy

现代和实验性环境条件下钼循环的重要新观点：调整古氧化还原代理

• 批准号: 1124327
• 负责人: Timothy Lyons
• 金额: $ 29.85万
• 依托单位: University of California-Riverside
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2011
• 资助国家: 美国
• 起止时间: 2011-10-01 至 2015-09-30
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1124327&HistoricalAwards=false
• 关键词: Critical; new; perspectives; molybdenum; cycling

The story of ancient ocean chemistry is the story of our origins. The geologic record reveals the presence of animals over only the last 10% of Earth?s 4.6-billion-year history and the origins of modern humans only a flicker of time ago. Most researchers link the appearance of the first animals to a rise in atmospheric oxygen to a level high enough to support complex animal metabolisms. The first 90% of Earth history, however, is a story of profound change in the oxygen state of the atmosphere and ocean, with complete absence of oxygen over the first half of Earth history and an oxygen-free deep ocean for most of the next half. Oxygen abounds today, and the ocean teems with animals, yet the oxygen-lean landscape of the early ocean was the cradle of our ancestors. The best view of these early organisms and their surroundings comes from fossils and the chemical properties of sediments deposited within the ancient ocean, and no element in the periodic table has played a greater role than molybdenum (Mo) as a window to the past.Molybdenum, a nutrient essential in the biological cycling of nitrogen, must have been a determining factor in the paths and rates that led ultimately to the early evolution of marine animals, particularly since its concentration in seawater varies dramatically with the availability of oxygen. This and other life-sustaining metals can be scrubbed out of seawater in the presence of hydrogen sulfide, which probably spread through sizeable portions of the ancient ocean. Recent research by this group and a few others has come a long way in providing a roadmap to the chemistry of ancient seawater based on the distributions and isotopic properties of Mo in ancient sediments, but key questions remain. Our understanding of the co-evolution of early life and ocean chemistry can only be as strong as the knowledge of how Mo is cycled now and in the past?particularly under the oxygen-poor conditions that dominated the early ocean. This study seeks to use novel, cutting-edge analytical methods in the lab and in the field to fill essential gaps in our grasp of Mo biogeochemistry. Among the key issues and questions are the mechanisms of Mo uptake across diverse depositional settings, particularly those with abundant hydrogen sulfide in the seawater. What specifically are the relationships to organic matter, the remains of organisms, and are the isotopes of Mo fractionated during interactions with organic substrates? Isotopes are atoms of the same element that differ in their masses and specific reaction behaviors and so can provide unique information about chemical pathways and the controlling environmental factors, such as oxygen availability. What is the full range of potential Mo hosts in settings rich in hydrogen sulfide, and how does dissolved Mo speciate and fractionate isotopically under those conditions? Although these chemical questions are quite specific, the implications are broad and speak to the ability to fingerprint conditions in the ocean that either fostered or challenged the origins and diversification of early life. The impact of this study will extend widely. A far greater ability to unravel the history of life is an expected outcome, and investigators will develop and refine novel analytical methods with broader relevance to many other trace metals and their biogeochemical cycles, including those in the modern ocean. Thanks to their hard-earned experience they are now able to demonstrate the great utility of particle accelerators in geobiological research. They aim to smooth the path for others traveling the same route by providing a virtual experience (website and short course) that captures their analytical maturation from beginners to experts, spanning from the particulars of our experience to more general logistical and scientific details (a sort of ?Synchrotron for Dummies?). They plan a high level of undergraduate involvement that mirrors UCR?s status as one of the most culturally diverse campuses in America. Finally, in an effort to reach across international boundaries, investigators have planned monthly group meetings with their colleagues in Beijing designed to emphasize student presentations, to enhance the flow of ideas in both directions, and to foster additional collaborative exploration of the early ocean and its co-evolving life. Although the methods are diverse and demanding, their motivations distill down to a single simple question: where did we come from?

古代海洋化学的故事是我们起源的故事。地质记录揭示了动物在地球的最后10％的历史的历史的最后10％，而现代人类的起源仅在时代之前就存在。大多数研究人员将第一批动物的外观与大气中的氧气增加到足以支持复杂动物代谢的水平。然而，地球历史的前90％是一个故事，讲述了大气和海洋的氧气状态的深刻变化，在地球上半段中，完全没有氧气，在下半年的大部分时间里，没有氧气的深海。如今，氧气充斥着，海洋充满了动物，但是早期海洋的氧气叶景观是我们祖先的摇篮。 The best view of these early organisms and their surroundings comes from fossils and the chemical properties of sediments deposited within the ancient ocean, and no element in the periodic table has played a greater role than molybdenum (Mo) as a window to the past.Molybdenum, a nutrient essential in the biological cycling of nitrogen, must have been a determining factor in the paths and rates that led ultimately to the early evolution of marine animals, particularly since its海水的浓度随氧的可用性而变化巨大。在存在硫化氢的情况下，可以从海水中擦洗这种和其他维持生命的金属，这些金属可能通过古老的海洋大部分散布。该小组和其他一些人的最新研究在为古代海水的化学图表图中提供了基于MO在古代沉积物中的分布和同位素特性的路线图，但仍然存在关键问题。我们对早期生命和海洋化学的共同发展的理解只能像MO现在和过去如何循环的知识一样强？尤其是在占主导早期海洋的氧气贫困条件下。这项研究试图在实验室和现场使​​用新颖的，尖端的分析方法来填补我们对MO生物地球化学的掌握的基本空白。在关键问题和问题中，有多种沉积环境中MO吸收的机制，尤其是海水中硫化氢丰富的机制。与有机物的残留物，有机物的残留物以及MO的同位素在与有机基质的相互作用过程中是否分馏？同位素是与其质量和特定反应行为不同的相同元素的原子，因此可以提供有关化学途径和控制环境因素（例如氧利用率）的独特信息。在富含硫化氢的设置中，在各种条件下溶解的MO识别和分馏如何在这些条件下溶解的MO溶解和分量如何？尽管这些化学问题是非常具体的，但含义是广泛的，并说明了在海洋中养育或挑战早期生命的起源和多样化的海洋指纹条件的能力。这项研究的影响将广泛扩展。揭示生命历史的能力更大，这是一个预期的结果，研究人员将开发和完善与许多其他痕量金属及其生物地球化学周期（包括现代海洋中的痕量金属周期）更广泛相关的新型分析方法。由于他们来之不易的经验，他们现在能够证明粒子加速器在地球生物学研究中的巨大效用。他们的目标是通过提供虚拟体验（网站和短期课程）来捕捉他们从初学者到专家的分析成熟，从我们的经验的细节到更一般的后勤和科学细节（一种？synchrotron for Dummies？），他们旨在使其他人走上相同路线的道路。他们计划了高水平的本科参与，以反映UCR的地位是美国最多样化的校园之一。最后，为了跨越国际界限，调查人员计划与北京同事每月举行小组会议，旨在强调学生的演讲，以增强两个方向上的思想流程，并促进对早期海洋及其共同发展生活的额外协作探索。尽管这些方法是多种多样且要求的，但它们的动机将其提取到一个简单的问题：我们来自哪里？