Calcium Carbonate Dissolution Mechanisms in the Ocean

碳酸钙在海洋中的溶解机制

• 批准号: 2242211
• 负责人: Jess Adkins
• 金额: $ 63.64万
• 依托单位: California Institute of Technology
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2023
• 资助国家: 美国
• 起止时间: 2023-04-01 至 2026-03-31
• 项目状态: 未结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=2242211&HistoricalAwards=false
• 关键词: Calcium; Carbonate; Dissolution; Mechanisms; Ocean

The rate at which calcium carbonate dissolves in seawater is an important piece of the ocean carbon cycle. It is a key factor in the oceans’ ability to absorb fossil fuel carbon dioxide. It is also important to understanding and predicting ocean acidification and may play a role in new technologies to curb climate change. Despite this importance, a great deal remains uncertain about the mechanism and rate of calcium carbonate dissolution. This project will conduct laboratory experiments using new methods to study calcium carbonate dissolution at several different conditions. The project will support two early-career investigators including a graduate student. Results will be shared with the public, including through support of an animation artist. In previous work, this team and their collaborators have made several improvements to our understanding of the carbonate dissolution rate law in the ocean. Using a novel carbon isotope tracer technique in the lab, and in situ in the water column, they can measure the dissolution rate 20-200x more sensitively than other techniques. This is especially true near equilibrium where rates are slow, but also where most of the ocean resides. Their previous work demonstrated that the rate law has two critical thresholds between three separate modes of surface dissolution mechanisms: near equilibrium, dissolution proceeds as the advance of step edges; with further undersaturation, the free energy in solution opens fast-dissolving etch pits at lattice defects in the solid; furthest from equilibrium, etch pits begin to form homogeneously on the 2-D solid surface leading to maximal dissolution rates. However, understanding of the full chemical control on the rate law, and its interplay with these surface energetic features has yet to be determined. This project will seek to experimentally and theoretically constrain the mechanism behind the rate law for marine carbonate dissolution. The saturation state will be systematically changed as a function of other aspects of the chemistry to test the elementary reactions that have been successfully used for years to describe dissolution in freshwaters. The saturation state will be varied over a range of sulfate concentrations, calcium/carbonate ratios, and magnesium/calcium ratios in independent experiments. Both the initial time dependence of the raw data, and SIMS microprobe profiles of the experimental solids will allow determination of the gross precipitation and gross dissolution rates in conjunction with the net rate constraints from slopes of dissolved carbon isotope ratios produced versus time.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.

碳酸钙溶解在海水中的速率是海洋碳循环的重要部分。这是海洋吸收化石燃料二氧化碳的能力的关键因素。了解和预测海洋酸化并可能在新技术中发挥作用以遏制气候变化也很重要。尽管这一重要性，但对碳酸钙溶解的机理和速率仍然不确定。该项目将使用新方法进行实验室实验，以在几种不同的条件下研究碳酸钙溶解。该项目将支持包括研究生在内的两名早期研究人员。结果将与公众共享，包括通过动画艺术家的支持。在以前的工作中，该团队及其合作者对我们对海洋中碳酸盐溶解率法的理解做出了一些改进。使用实验室中的新型碳同位素示踪剂技术，在水柱中，它们可以比其他技术更敏感地测量20-200倍的溶解速率。在速度较慢的情况下，尤其是在大多数海洋住宅的地方，尤其如此。他们先前的工作表明，速率定律在三种单独的表面溶解机制之间具有两个关键阈值：接近平衡，溶解作为步进边缘的前进；随着进一步的不饱和，溶液中的自由能在固体中的晶格缺陷处打开快速溶解的ET坑。 ET坑从最远的等效坑开始在2-D固体表面上开始形成，从而导致最大溶解速率。但是，了解对速率定律的完整化学控制以及与这些表面能量特征的相互作用尚未确定。该项目将试图在实验和理论上限制海洋碳酸盐溶解的速率定律背后的机制。满意度状态将随着化学其他方面的函数而系统地改变，以测试已成功使用多年来描述淡水中溶解的基本反应。在独立实验中，满意度状态将在硫酸盐浓度，钙/碳酸盐比和镁/钙比的范围内变化。原始数据的初始时间依赖性以及SIMS实验固体的微探针概况都将允许确定总降水量和总体溶解速率，并结合产生的分散的碳同位素比的净率约束，而与时间相比，这是NSF的法定任务，并通过评估范围来评估奖项，这是奖励的良好的，并反映出了基础的支持。