Influence of hydroxamate siderophores on redox-sensitive trace elements and their isotopes and their relevance for the application of redox proxies in paleo-climate reconstruction studies

异羟肟酸铁载体对氧化还原敏感的微量元素及其同位素的影响及其与氧化还原代理在古气候重建研究中应用的相关性

• 批准号: 437594845
• 负责人: Professor Dr. Michael Bau, since 11/2021
• 金额: --
• 依托单位: Bundesanstalt für Geowissenschaften und Rohstoffe (BGR)
• 依托单位国家: 德国
• 项目类别: Research Grants
• 财政年份: 2020
• 资助国家: 德国
• 起止时间: 2019-12-31 至 2023-12-31
• 项目状态: 已结题
• 来源: https://gepris.dfg.de/gepris/projekt/437594845?language=en
• 关键词: Influence; hydroxamate; siderophores; redox; sensitive

In the natural environment, plants, microbes and fungi excrete a range of iron-specific organic chelators called siderophores. These molecules occur in almost all natural settings and are known to not only bind to Fe(III), but also have high complex stability constants with a range of other environmentally important trace metals, esp. to those that have a high charge and low ionic radius. These elements, i.e., Zr, Hf, the rare earth elements, Th, U and others, are referred to as high-field strength elements (HFSE) in geochemistry and are traditionally considered immobile during water-rock interaction unless a specific change in the oxidation state occurs, which may cause a different behavior of the redox-sensitive HFSE (i.e., U, Ce) and their isotopes in comparison to redox-insensitive HFSE. This observation is commonly used in paleoclimate studies to reconstruct past atmospheric oxygen levels. My pilot research indicates that the siderophore desferrioxamine B is able to bind to some of these redox-sensitive HFSE and enhances their mobility relative to the redox-insensitive HFSE during leaching from certain rock matrices. In the present proposal, I want to systematically investigate the potential impact of the DFOB siderophore on a range of redox-sensitive trace elements and their isotopes. In order to achieve this, I will conduct batch leaching experiments on natural rocks and I will also conduct scavenging experiments, both under oxic and anoxic conditions, in presence of siderophores as well as other organic ligands. The trace element and isotope studies will be complemented by XANES/EXAFS synchrotron radiation measurements to verify whether siderophores are actually able to oxidize redox-sensitive trace metals even under low oxygen conditions or whether other mechanisms cause the pronounced mobilization of redox-sensitive HFSE in presence of the DFOB siderophore. This study is filling an important research gap as the effects of extracellular biological compounds on these elements and isotopes in the natural environment are fairly unknown and it is also not clear whether the potential presence of such biogenic compounds may set limitations on the application of certain paleoredox proxies and whether intense biological activity during or after sediment deposition could lead to false-positives in paleoclimate reconstruction studies. The results of this project may also provide an idea on whether certain redox proxies, under certain circumstances, might indicate the presence of ‘life’ rather than the presence of oxygen, e.g., in the Meso- or Neoarchean. To achieve this goal, I will be collaborating with internationally renowned experts in the fields of trace element and isotope geochemistry and x-ray absorption spectroscopy.

在自然环境中，植物、微生物和真菌会分泌一系列称为铁载体的铁特异性有机螯合剂，这些分子几乎存在于所有自然环境中，并且已知不仅能与 Fe(III) 结合，而且具有较高的复杂稳定常数。与一系列其他对环境重要的微量金属，特别是那些具有高电荷和低离子半径的元素，即 Zr、Hf、稀土元素、Th、U 等，被称为。地球化学中的高场强元素（HFSE），传统上被认为在水-岩相互作用过程中是不可移动的，除非氧化态发生特定的变化，这可能导致氧化还原敏感的 HFSE（即 U、Ce）发生不同的行为。 ）及其同位素与氧化还原不敏感的 HFSE 的比较 该观察结果通常用于古气候研究中以重建过去的大气氧水平 我的初步研究表明，铁载体去铁胺 B 是。在从某些岩石基质浸出过程中，能够与其中一些氧化还原敏感的 HFSE 结合，并增强其相对于氧化还原不敏感的 HFSE 的迁移率。在本提案中，我想系统地研究 DFOB 铁载体对一系列的潜在影响。为了实现这一目标，我将在天然岩石上进行批量浸出实验，并且还将在有氧和缺氧条件下进行清除实验，在存在铁载体以及其他有机配体的情况下，微量元素和同位素研究将由 XANES/EXAFS 同步加速器辐射测量来补充，以验证铁载体是否实际上能够氧化氧化还原敏感的痕量金属，即使在低氧条件下或是否有其他机制。在 DFOB 铁载体存在的情况下，引起氧化还原敏感的 HFSE 的显着动员。这项研究填补了细胞外生物化合物对这些元素影响的重要研究空白。自然环境中的同位素是相当未知的，也不清楚此类生物化合物的潜在存在是否可能对某些古氧化还原替代物的应用产生限制，以及沉积物沉积期间或之后的强烈生物活动是否可能导致假阳性该项目的结果还可以提供一个想法，即某些氧化还原代理在某些情况下是否可能表明“生命”的存在而不是氧气的存在，例如在中观或中观世界中。为了实现这一目标，我将与微量元素和同位素地球化学以及 X 射线吸收光谱领域的国际知名专家合作。