OCE-PRF: Towards Quantifying Calcium Carbonate Sediment Dissolution During Marine Diagenesis

OCE-PRF：量化海洋成岩过程中碳酸钙沉积物溶解

• 批准号: 2205984
• 负责人: Mohammed Hashim
• 金额: $ 37.65万
• 依托单位: Woods Hole Oceanographic Institution
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2022
• 资助国家: 美国
• 起止时间: 2022-12-01 至 2024-11-30
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=2205984&HistoricalAwards=false
• 关键词: OCE; PRF; Towards; Quantifying; Calcium

OCE-PRF Towards Quantifying Calcium Carbonate Sediment Dissolution During Marine DiagenesisThe goal of the project is to investigate dissolution of calcium carbonate (CaCO3) in sediments below the seafloor and determine its importance to the chemistry of seawater. This project uses sediment samples and chemical data collected from different parts of the ocean during the past five decades by scientific ocean drilling programs. Sediment dissolution of carbonate can lessen the impact of ocean acidification, the process that causes the pH of the ocean to decrease due to the uptake of carbon dioxide (CO2) from the atmosphere. Ocean acidification threatens the survival of marine organisms, such as oysters, clams, and coral reefs, which could alter marine food chains and food supply to humans. By improving understanding of carbonate dissolution in the ocean, results from this project will enable better predictions of the effects of ocean acidification on marine organisms. This will advance the progress of science and contribute to the knowledge that can inform public policy. In addition, understanding carbonate sediment dissolution serves other important purposes. For example, dissolution can create small spaces between sediments that may get filled with groundwater once sediments convert to rocks over millions of years. Thus, understanding the occurrence and spatial distribution of spaces within rocks may help determine the volume and movement of groundwater in subsurface aquifers. This project provides support for a postdoctoral research fellow and research training opportunities for students through the Summer Student Fellowship and Woods Hole-wide Partnership Education Programs at the Woods Hole Oceanographic Institution. Carbonate mineral dissolution is an integral part of the alkalinity and carbon cycles in the ocean and is expected to play an increasingly significant role in mediating changes in ocean chemistry as atmospheric CO2 continues to rise. The goal of this project is to provide thermodynamic constraints necessary for quantifying carbonate sediment dissolution in marine diagenetic environments. Specifically, the CaCO3 saturation state of pore fluids will be calculated in 365 globally distributed sites from previous scientific ocean drilling expeditions using a specially developed Pitzer ion activity model which is particularly useful for calculating activity coefficients in high ionic strength solutions such as those that characterize most diagenetic environments. These calculations will be substantiated with geochemical and textural analyses of sediment samples from four representative sites to identify the specific diagenetic processes (e.g., dissolution, precipitation, and recrystallization) and document the conditions responsible for their occurrence and prevalence. The immediate advantage of calculating the saturation state of pore fluids is that such data can be used to estimate carbonate sediment dissolution below the seafloor and quantify its contribution to the alkalinity and carbon cycles, which will lead to more accurate predictions of the consequences of ocean acidification. Another benefit of the global saturation state dataset is that it will improve our understanding of authigenic carbonate precipitation and its link to the carbon cycle over Earth history, which has been proposed as a significant sink for carbon. Furthermore, by complementing the thermodynamic calculations with textural and geochemical analyses, this project will parse out various diagenetic processes and identify the sedimentological and geochemical conditions responsible for their occurrence. Such knowledge is crucial for evaluating the impact of diagenesis on the carbonate-hosted paleoenvironmental proxies. Collectively, this project will pave the way towards a mechanistic understanding of carbonate diagenesis. This will provide important constraints on the oceanic alkalinity cycle, carbon burial rates, and geochemical proxies, which ultimately help us better understand the future of our ocean system in the context of climate change.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.

OCE-PRF Towards Quantifying Calcium Carbonate Sediment Dissolution During Marine Diagenesis该项目的目标是调查碳酸钙（CaCO3）在海底以下沉积物中的溶解情况，并确定其对海水化学的重要性。该项目使用了过去50年来通过科学海洋钻探计划从海洋不同地区收集的沉积物样本和化学数据。碳酸盐的沉积物溶解可以减轻海洋酸化的影响，海洋酸化是由于从大气中吸收二氧化碳（CO2）而导致海洋pH值下降的过程。海洋酸化威胁着牡蛎、蛤蜊和珊瑚礁等海洋生物的生存，这可能会改变海洋食物链和人类的食物供应。通过提高对海洋中碳酸盐溶解的认识，该项目的结果将有助于更好地预测海洋酸化对海洋生物的影响。这将推动科学进步，并有助于为公共政策提供信息的知识。此外，了解碳酸盐沉积物溶解作用还有其他重要目的。例如，溶解可以在沉积物之间产生小空间，一旦沉积物经过数百万年转化为岩石，这些空间可能会被地下水填充。因此，了解岩石内部空间的发生和空间分布可能有助于确定地下含水层中地下水的体积和运动。该项目通过伍兹霍尔海洋研究所的暑期学生奖学金和伍兹霍尔范围内的伙伴关系教育方案，为博士后研究员提供支持，并为学生提供研究培训机会。碳酸盐矿物溶解是海洋碱度和碳循环的一个组成部分，预计随着大气CO2继续上升，碳酸盐矿物溶解将在调节海洋化学变化方面发挥越来越重要的作用。该项目的目标是提供量化海洋成岩环境中碳酸盐沉积物溶解所需的热力学约束。具体而言，CaCO3饱和状态的孔隙流体将计算在365个全球分布的网站从以前的科学海洋钻探探险使用专门开发的Pitzer离子活性模型，这是特别有用的计算活动系数在高离子强度的解决方案，如那些最具成岩环境的特点。这些计算将得到四个代表性地点沉积物样品的地球化学和结构分析的证实，以确定具体的成岩过程（例如，溶解、沉淀和重结晶），并记录导致其发生和流行的条件。计算孔隙流体饱和状态的直接好处是，这些数据可用于估计海底以下碳酸盐沉积物的溶解情况，并量化其对碱度和碳循环的贡献，从而更准确地预测海洋酸化的后果。全球饱和状态数据集的另一个好处是，它将提高我们对自生碳酸盐沉淀及其与地球历史上碳循环的联系的理解，这被认为是碳的重要汇。此外，通过用结构和地球化学分析补充热力学计算，该项目将分析各种成岩过程，并确定导致其发生的沉积学和地球化学条件。这些知识对于评价成岩作用对碳酸盐岩古环境代用指标的影响至关重要。总的来说，这个项目将为碳酸盐岩成岩作用的机械理解铺平道路。这将对海洋碱度循环、碳埋藏率和地球化学代用指标提供重要的限制，最终帮助我们更好地了解气候变化背景下海洋系统的未来。该奖项反映了NSF的法定使命，并通过使用基金会的知识价值和更广泛的影响审查标准进行评估，被认为值得支持。