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自然酸性雨水中的过程。这是因为大气中的二氧化碳溶解在雨水中形成碳酸，雨水与岩石相互作用使它们溶解。溶解的二氧化碳被捕获在河流和海水中，作为碳酸氢盐（存在于所有天然沃茨中，例如矿泉水），在那里稳定存在数千年或数万年，然后以碳酸钙（如石灰石）的矿物形式永久储存，并以石灰石的形式沉积在海洋中。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，岩石的陆地化学风化以及随后以碳酸钙形式埋藏的碳，作为控制碳循环的反馈，从而控制了地球历史上的气候。与化学风化相关的碳通量通常通过河流化学估算，假设河流的成分可以与岩石溶解的类型相匹配。这是一种简化，因为化学反应意味着河流不仅仅具有与溶解的岩石相同的化学成分。一组化学反应被称为阳离子交换反应。当带电矿物表面和水之间的化学平衡发展时，它们迅速发生。具有带电表面的最重要的矿物组之一是粘土。这些快速反应在土壤和含水层中得到了很好的研究，但研究河流化学的科学界在很大程度上忽视了这些反应。我们已经生成了一套初步数据，这些数据表明，一旦考虑阳离子交换过程，它会显著改变天然沃茨的化学性质，以及通过化学风化作用消耗的碳总量。我们已经开发出一种新的工具包，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，可以追踪快速的化学反应，2）核磁共振，可以表征发生交换的矿物表面，3）X射线衍射，对矿物中可交换位点的特定成分敏感。我们已经计划了一系列的实验研究，以量化的过程中，以及约束控制的例子，再加上在世界上最大的河流的研究（对样本的档案收集），以确定全球的重要性的问题。

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

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

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.