Collaborative Research: Understanding substrate limitation and Lithium and Silicon isotope fractionation during secondary clay formation in marine systems

合作研究：了解海洋系统次生粘土形成过程中的底物限制以及锂和硅同位素分馏

• 批准号: 1923802
• 负责人: Yuanzhi Tang
• 金额: $ 33.89万
• 依托单位: Georgia Tech Research Corporation
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2020
• 资助国家: 美国
• 起止时间: 2020-01-01 至 2024-06-30
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1923802&HistoricalAwards=false
• 关键词: Collaborative; Research; Understanding; substrate; limitation

A long-standing topic of investigation in the field of chemical oceanography is understanding the processes that deliver elements to, and remove them from, seawater. There has long been a "missing sink" in the global marine silicon (Si) budget in that removal to sediments did not appear to balance the inputs from rivers. Several decades ago, it was postulated that "reverse weathering" in marine sediments could be this missing sink. In this process, the weathering process that takes place on land, whereby silicon is removed from minerals and dissolved in water, would be reversed and these minerals would be reconstituted in marine sediments through the formation of clays. Evidence for this process was very difficult to obtain, and only recently have studies using advanced measurement techniques shown that the global magnitude of marine reverse weathering could account for all the missing sink term in the global Si budget. If validated, this means reverse weathering would represent the largest individual sink for marine Si identified to date, with most of this burial occurring in a relatively small area of the ocean, the land-sea interface. Moreover, the continued upward revision of the marine reverse weathering rate has implications for the sequestration of other elements (e.g. iron, aluminum) and for other coastal processes (e.g. ocean acidification, as carbon dioxide is a byproduct of the reverse weathering process). This project aims to understand the most important factors affecting how fast reverse weathering occurs, and developing new approaches to evaluate this process in the field environment. Beyond the scientific pursuits, this project will support an early career researcher, a postdoctoral investigator, a graduate student, and undergraduate interns. It will also support high school outreach through science fair participation and annual scholarships for students wishing to pursue Marine Science education. This project will develop a community outreach activity to be used annually during the Atlanta Science Festival, Georgia's biggest science fair that showcases science and technology to the public. Finally, it will build capacity for silicon isotope measurements in the U.S.In this project, the investigators propose to understand the driving factors of marine secondary clay formation and facilitate the determination of reaction degree in the field using a novel dual silicon and lithium stable isotope approach. The overarching goals are: 1) to better constrain the geochemical factors, kinetics, and mechanisms involved in secondary clay formation from diatom-produced silica (bSiO2); this will be done by conducting controlled laboratory experiments using pure mineral phases, diatom bSiO2, and artificial seawater; 2) to test the validity of the isolated geochemical factors by conducting mesocosm incubation experiments using field sediment materials, diatom bSiO2, and seawater; and 3) to experimentally determine whether laboratory-derived Li and Si isotope fractionations are valid during secondary clay formation under marine sediment conditions. This work addresses one of the eight Ocean Sciences Priorities identified in The National Research Council's 2015-2025 Decadal Survey of Ocean Sciences, specifically "How have ocean biogeochemical and physical processes contributed to today's climate and its variability, and how will this system change over the next century?" These results have fundamental importance to understanding the factors regulating marine elemental sequestration (e.g. Si, C, Fe, Al, Mg, K) and those driving global climate through oceanic CO2 evolution, a byproduct of the reverse weathering reaction, in marine sediments.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.

化学海洋学领域的一个长期研究课题是了解将元素输送到海水中以及从海水中去除元素的过程。长期以来，全球海洋硅 (Si) 预算中一直存在“失踪汇”，因为沉积物的清除似乎无法平衡河流的输入。几十年前，人们推测海洋沉积物中的“逆风化”可能就是这个缺失的汇。在此过程中，陆地上发生的风化过程（即硅从矿物质中去除并溶解在水中）将被逆转，这些矿物质将通过形成粘土在海洋沉积物中重新组成。这一过程的证据很难获得，直到最近，使用先进测量技术的研究表明，全球海洋逆风化的程度可以解释全球硅预算中所有缺失的汇项。如果得到验证，这意味着逆风化将代表迄今为止发现的海洋硅的最大个体汇，其中大部分埋藏发生在海洋相对较小的区域，即陆海界面。此外，海洋逆风化速率的持续向上修正对其他元素（例如铁、铝）的封存和其他沿海过程（例如海洋酸化，因为二氧化碳是逆风化过程的副产品）产生影响。该项目旨在了解影响逆风化发生速度的最重要因素，并开发新方法来评估现场环境中的这一过程。 除了科学追求之外，该项目还将支持早​​期职业研究员、博士后研究员、研究生和本科生实习生。它还将通过参加科学博览会和为希望接受海洋科学教育的学生提供年度奖学金来支持高中的外展活动。该项目将开展一项社区外展活动，每年在亚特兰大科学节期间使用，亚特兰大科学节是佐治亚州最大的科学博览会，向公众展示科学和技术。最后，它将在美国建立硅同位素测量能力。在该项目中，研究人员建议了解海洋次生粘土形成的驱动因素，并利用新型双硅和锂稳定同位素方法促进现场反应程度的确定。总体目标是：1）更好地限制硅藻产生的二氧化硅（bSiO2）形成次生粘土所涉及的地球化学因素、动力学和机制；这将通过使用纯矿物相、硅藻 bSiO2 和人造海水进行受控实验室实验来完成； 2）利用现场沉积物材料、硅藻bSiO2和海水进行介层孵化实验，测试分离出的地球化学因子的有效性； 3) 通过实验确定实验室衍生的锂和硅同位素分馏在海洋沉积条件下次生粘土形成过程中是否有效。 这项工作涉及国家研究委员会 2015-2025 年海洋科学十年调查中确定的八个海洋科学优先事项之一，特别是“海洋生物地球化学和物理过程如何对当今的气候及其变化做出贡献，以及该系统将如何变化下个世纪？”这些结果对于了解调节海洋元素封存（例如 Si、C、Fe、Al、Mg、K）的因素以及通过海洋沉积物中逆风化反应的副产品海洋二氧化碳演化驱动全球气候的因素具有根本重要性。该奖项反映了 NSF 的法定使命，并通过使用基金会的智力价值和更广泛的影响审查标准进行评估，被认为值得支持。

项目成果

Effect of cleaning methods on the dissolution of diatom frustules

清洗方法对硅藻壳溶解的影响

• DOI: 10.1016/j.marchem.2020.103826
• 发表时间: 2020-08
• 期刊: Marine Chemistry
• 影响因子: 3
• 作者: Saad, Emily M.;Pickering, Rebecca A.;Shoji, Kanaha;Hossain, Mohammad I.;Glover, T. Grant;Krause, Jeffrey W.;Tang, Yuanzhi
• 通讯作者: Tang, Yuanzhi