Muddying the waters: cation exchange processes as a major control on weathering fluxes?

搅浑水：阳离子交换过程是风化通量的主要控制因素？

• 批准号: NE/T007214/1
• 负责人: Edward Tipper
• 金额: $ 79.08万
• 依托单位: University of Cambridge
• 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: 已结题
• 来源: https://gtr.ukri.org/projects?ref=NE%2FT007214%2F1
• 关键词: Muddying; waters; cation; exchange; processes

Chemical weathering is the process by which rocks dissolve in rainwater, which is naturally acidic. This is because atmospheric carbon dioxide dissolves in rain to form carbonic acid, and the rainwater interacts with rocks making them dissolve. The dissolved carbon dioxide becomes trapped in river and seawater, as bicarbonate (present in all natural waters such as mineral water for example), where it resides stably for thousands, or tens of thousands of years, and is then stored permanently in a mineral form as calcium carbonate (like limescale) and deposited as limestone in the oceans. Rock dissolution or chemical weathering is a major process in the global carbon cycle and it is thought that this terrestrial chemical weathering of rocks, and subsequent burial of carbon as calcium carbonate, acts as the feedback which has controlled the carbon cycle and thus climate over Earth history.The carbon fluxes associated with chemical weathering are commonly estimated from river chemistry, assuming that the river composition can be matched to the type of rock dissolving. This is a simplification because chemical reactions mean that a river doesn't simply have the same chemical composition as a rock which dissolves. One suite of chemical reactions are referred to as cation exchange reactions. They occur rapidly as a chemical equilibrium develops between charged mineral surfaces and a water. One of the most important mineral groups which have charged surfaces are clays. These rapid reactions are well studied in soils and aquifers, but the scientific community working on river chemistry has largely neglected these reactions. We have generated a suite of preliminary data that shows that once the cation exchange process is taken into account it changes significantly the chemistry of natural waters and the total amount of carbon consumption through chemical weathering.We have developed a new tool kit that can address the significance of cation exchange. Our tools are 1) isotope geochemistry, that can trace the rapid chemical reactions, 2) nuclear magnetic resonance that can characterise the mineral surfaces where exchange is occurring and 3) X-ray diffraction that is sensitive to the specific compositions of exchangeable sites in minerals. We have planned a series of experimental studies to quantify the processes in well constrained controlled examples, coupled to a study on the largest rivers in the world (on an archive collection of samples) to determine the global importance of the problem.

化学风化是岩石溶解在雨水中的过程，这种雨水是天然酸性的。这是因为大气二氧化碳溶于雨中以形成碳酸，雨水与岩石相互作用，使其溶解。溶解的二氧化碳被困在河流和海水中，作为碳酸氢盐（例如，存在于所有天然水域，例如矿物水），在那里它稳定稳定成千上万，或数万年，然后以矿物质形式永久存储为碳酸盐（如limescale），并沉积在海洋中的碳酸盐（如limescale）。岩石溶解或化学风化是全球碳循环中的一个主要过程，人们认为，岩石的这种陆地化学风化，随后将碳作为碳酸钙埋葬，作为碳循环的反馈，从而控制了地球历史上的气候，因此与化学风光相关的碳量通常是从河流化学估计的河流中估计的，这些碳构成河流的构造是对河流构成的估计。这是简化的，因为化学反应意味着河流不仅具有与溶解的岩石相同的化学成分。一套化学反应称为阳离子交换反应。当化学平衡在带电的矿物表面和水之间发展时，它们迅速发生。充电表面的最重要的矿物质组之一是粘土。这些快速反应在土壤和含水层中进行了很好的研究，但是从事河流化学的科学界在很大程度上忽略了这些反应。我们已经生成了一套初步数据，这些数据表明，一旦考虑到阳离子交换过程，它会显着改变自然水的化学性质和通过化学风化的碳消耗总量。我们开发了一个新的工具套件，可以解决阳离子交换的重要性。我们的工具是1）同位素地球化学，可以追踪快速化学反应，2）可以表征发生交换的矿物表面和3）X射线衍射剂对矿物质可交换位点的特定组成敏感的矿物表面的核磁共振。我们已经计划了一系列实验研究，以量化受良好受控的示例中的过程，并与世界上最大河流（在样本的档案集中）进行研究，以确定问题的全球重要性。

项目成果

Global silicate weathering flux over-estimated because of sediment-water cation exchange

由于沉积物-水阳离子交换，全球硅酸盐风化通量被高估

• DOI: 10.17863/cam.63321
• 发表时间: 2021
• 作者: Tipper E

The efficacy of enhancing carbonate weathering for carbon dioxide sequestration

• DOI: 10.3389/fclim.2022.928215
• 发表时间: 2022-08-11
• 期刊: FRONTIERS IN CLIMATE
• 作者: Knapp, William J.;Tipper, Edward T.
• 通讯作者: Tipper, Edward T.

Magnesium Isotopes - Tracer for the Global Biogeochemical Cycle of Magnesium Past and Present or Archive of Alteration?

镁同位素 - 镁过去和现在的全球生物地球化学循环的示踪剂或蚀变档案？

• DOI: 10.1017/9781108991698
• 发表时间: 2022
• 作者: Tipper E