Rhenium isotopes to track carbon dioxide emissions by oxidative weathering

铼同位素可追踪氧化风化引起的二氧化碳排放

• 批准号: NE/T001119/2
• 负责人: Robert Hilton
• 金额: $ 41.77万
• 依托单位: University of Oxford
• 依托单位国家: 英国
• 项目类别: Research Grant
• 财政年份: 2021
• 资助国家: 英国
• 起止时间: 2021 至 无数据
• 项目状态: 未结题
• 来源: https://gtr.ukri.org/projects?ref=NE%2FT001119%2F2
• 关键词: Rhenium; isotopes; track; carbon; dioxide

Carbon dioxide (CO2) plays a central role in controlling Earth's climate as a greenhouse gas. Atmospheric CO2 concentrations can be changed by Earth's carbon cycle, which moves carbon between the atmosphere, plant and animal life, the oceans and rocks. Atmospheric CO2 concentrations have been increasing in recent decades because of the human-induced transfer of carbon from rocks to the atmosphere by fossil fuel burning. However, natural processes can also change the rate of carbon transfer to the atmosphere. One such transfer occurs when rocks containing vast stores of organic carbon are exposed to weathering, a process that releases CO2. This process may have varied significantly over Earth's history, for instance during episodes of mountain building. However, we presently lack reliable tools to track these changes which limits our understanding of the processes controlling natural variability in atmospheric CO2 concentrations, and consequently our ability to accurately predict how the carbon cycle will evolve in the future. To measure the oxidation of rock organic matter in the modern day, we can track the CO2 gas directly. This approach can provide a local, short term view of the rates of CO2 release. Another approach has been developed which uses the element rhenium (Re) that is hosted in rocks alongside organic carbon. When rocks are weathered, the CO2 is released as a gas, while the Re becomes dissolved in water and is carried by rivers. In this way, we can measure how much Re rivers carry to estimate CO2 emissions over larger river basins. Unfortunately, to reconstruct weathering and CO2 emissions in the past, we cannot directly use these techniques. Instead, to look back in time at weathering of organic carbon in rocks and the associated CO2 emissions, the isotopes of Re hold much promise. This is because weathering could alter the ratio of Re isotopes released into river water, which in turn has the potential to change the global inventory of Re in seawater. Developments in analytical geochemistry, most recently led by the research team, mean that we have been able to measure the ratio of Re isotopes in river water for the first time. Our novel, unpublished data shows that the Re isotope ratio in rivers increases with weathering rate. This observation strongly suggests that Re isotopes could be used as a proxy of past oxidative weathering and associated CO2 emissions. In this project we will tackle the fundamental limitations of our present understanding of the Re isotope system, that hold back its current application as a weathering proxy. In particular, we must establish a deeper understanding of the relationship between Re isotope ratios in rocks, soils, the waters reacting in soils which feed rivers, and the largest rivers in the world. In parallel, we must also measure other sources of Re to the ocean from hydrothermal vents and the Re isotopes of seawater from the major ocean basins. Our proposal is planned as a unique collaboration between two laboratories with the same analytical capabilities. This collaboration allows us to capitalise on three major benefits: (i) To ensure data accuracy by sharing analytical and method advancements; (ii) To pool the expertise of a multi-disciplinary team of scientists; and (iii) To maximise the efficient use of resources by achieving an ambitious work programme across two cutting-edge laboratories. This project will produce the first complete assessment of the isotopic composition of Re in the bulk Earth and in weathering products being delivered to the global oceans. In doing so, we will lay the foundations for the Re isotope proxy to quantify and understand past changes in CO2 emission from rock weathering, and address a crucial shortcoming in the ability of state-of-the-art climate models to simulate the trajectory of carbon cycle changes in the past, present and future.

二氧化碳（CO2）在控制地球气候作为温室气体中起着核心作用。大气中的二氧化碳浓度可以通过地球的碳循环改变，该碳循环在大气，动植物生命，海洋和岩石之间移动碳。由于化石燃料燃烧，大气中的二氧化碳浓度在近几十年来一直在增加。但是，自然过程也可以改变向大气的碳转移速率。当含有大量有机碳储存的岩石暴露于风化时，就会发生这种转移，这是释放二氧化碳的过程。这个过程在地球历史上可能有很大不同，例如在山区建筑情节中。但是，我们目前缺乏可靠的工具来跟踪这些变化，从而限制了我们对控制大气二氧化碳浓度自然变异性的过程的理解，因此我们有能力准确预测碳循环将来如何发展。为了测量现代岩石有机物的氧化，我们可以直接跟踪二氧化碳气体。这种方法可以提供局部二氧化碳释放速率的局部短期视图。已经开发了另一种使用元素rhenium（re）的方法，该元素（re）与有机碳一起托管在岩石中。当岩石被风化时，二氧化碳被释放为气体，而RE溶解在水中并由河流携带。这样，我们可以衡量河流携带多少以估算较大河流盆地的二氧化碳排放。不幸的是，要重建过去的风化和二氧化碳排放，我们不能直接使用这些技术。取而代之的是，要回顾一下岩石和相关二氧化碳排放中有机碳的风化，RE的同位素具有很大的希望。这是因为风化可能会改变释放到河水中的RE同位素的比率，这反过来又有可能改变海水中RE的全球库存。分析地球化学的发展是由研究小组领导的，这意味着我们能够首次测量河水中的RE同位素比率。我们的新颖，未发表的数据表明，河流中的RE同位素比随风化速率而增加。该观察结果强烈表明，RE同位体可以用作过去氧化风化和相关二氧化碳排放的代表。在这个项目中，我们将解决我们目前对RE同位素系统的理解的基本局限性，这些局限性阻碍了当前的应用程序代理。特别是，我们必须更深入地了解岩石，土壤，水域在供养河流的土壤中反应和世界上最大的河流中的水域之间的关系。同时，我们还必须从主要海盆中的水热通风孔和海水的重新同位素中测量其他RE来源。我们的建议计划是两个具有相同分析能力的实验室之间的独特合作。这种合作使我们能够利用三个主要好处：（i）通过共享分析和方法进步来确保数据准确性； （ii）汇集一个多学科科学家团队的专业知识； （iii）通过在两个尖端实验室中实现雄心勃勃的工作计划来最大程度地利用资源。该项目将对散装地球中RE的同位素组成以及将产品传递到全球海洋中进行首次完整评估。在此过程中，我们将奠定RE同位素代理的基础，以量化和了解岩石风化的二氧化碳发射的过去变化，并解决最先进的气候模型模拟过去，现在和未来碳循环变化的轨迹变化的能力的关键缺点。

项目成果

Tracing oxidative weathering of rock organic carbon through geological time using rhenium isotopes

使用铼同位素通过地质时间追踪岩石有机碳的氧化风化

• DOI: 10.7185/gold2023.18305
• 发表时间: 2023
• 作者: Stow M

Using rhenium, d 187 Re, and RPO- 14 C to trace the fate of rock organic carbon in the Critical Zone

使用铼、d 187 Re 和 RPO- 14 C 追踪关键带中岩石有机碳的命运

• DOI: 10.46427/gold2022.10287
• 发表时间: 2022
• 作者: Grant K

Fractionation of rhenium isotopes in the Mackenzie River basin during oxidative weathering

• DOI: 10.1016/j.epsl.2021.117131
• 发表时间: 2021-11
• 期刊: Earth and Planetary Science Letters
• 影响因子: 5.3
• 作者: M. Dellinger;R. Hilton;G. Nowell

Quantifying petrogenic organic carbon weathering fluxes and associated CO 2 release using dissolved rhenium in rivers

使用河流中溶解的铼来量化成岩有机碳风化通量和相关的 CO 2 释放

• DOI: 10.7185/gold2023.17055
• 发表时间: 2023
• 作者: Dellinger M

Rhenium elemental and isotopic variations at magmatic temperatures

岩浆温度下铼元素和同位素的变化

• DOI: 10.7185/geochemlet.2402
• 发表时间: 2024
• 期刊: Geochemical Perspectives Letters
• 影响因子: 4.9
• 作者: Wang W