The Speed, Signature, and Significance of Barium Transformations in Seawater

海水中钡转变的速度、特征和意义

• 批准号: 2023456
• 负责人: Tristan Horner
• 金额: $ 68.91万
• 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: 2020
• 资助国家: 美国
• 起止时间: 2020-09-01 至 2024-08-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=2023456&HistoricalAwards=false
• 关键词: Speed; Signature; Significance; Barium; Transformations

The biological cycling of carbon in the oceans entrains many other elements, some directly (like nutrients that are essential for life) and some indirectly, as they become chemically involved in the processes that are affecting carbon. One such element is barium (Ba). Particles of the mineral barite (barium sulfate) have been found to form in association with microbial consumption of organic material in the ocean’s “twilight zone.” These particles settle to the ocean floor, and their presence in sediments has been used to infer changes in the conditions in the ocean back in time. Both the amount of barite in sediments and the isotope composition of Ba in barite are potentially sensitive to processes occurring in the twilight zone. However, several long-standing questions remain about Ba cycling in the oceans, which complicates the interpretation of barium-based proxy records. Examples of remaining questions include how much barium enters the oceans at mid-ocean ridge hydrothermal sites, and what controls the precipitation and dissolution of barite in the water column. This project seeks to tackle these questions using new approaches, on three scheduled research expeditions in the Pacific and Southern Oceans. In doing so, this project will support the education, training, and career development of a graduate student, postdoctoral researcher, and junior investigator. Undergraduate students from underrepresented groups will be recruited to conduct complementary shore-based experiments. This proposal seeks to answer four questions central to the utility of barium-based proxies in oceanography: What are the major inputs of new Ba to the ocean? What are their isotopic compositions? What controls the amount of pelagic barite precipitated during the remineralization of organic matter? What influences its isotopic composition? These questions will be addressed using a field-centric approach combining: in situ and shipboard tracer-incubation experiments, AUV-led adaptive sampling of Ba cycling ‘hotpots’, and section-based surveying of the surrounding oceanographic features. This multi-pronged approach will be used to investigate: the flux and isotopic composition of Ba released from the largest hydrothermal fields in the ocean, the Southern East Pacific Rise, with a focus on low-temperature venting; rates and signatures of pelagic barite precipitation associated with different phytoplankton assemblages in the Southern Ocean; and, the importance of environmental conditions, such as low ambient oxygen concentrations, in setting the efficiency of barite precipitation in the Eastern Tropical Pacific. The significance of each transformation will be assessed, which may lead to ruling out the importance of certain processes, or identifying new dependencies that could form the basis of new proxies.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.

碳在海洋中的生物循环带走了许多其他元素，有些是直接的（如生命所必需的营养素），有些是间接的，因为它们在化学上参与了影响碳的过程。一种这样的元素是钡（Ba）。在海洋的“阴阳魔界”中，微生物消耗有机物质时，会形成矿物重晶石（硫酸钡）的颗粒。这些颗粒沉降到海底，它们在沉积物中的存在被用来推断海洋条件的变化。沉积物中重晶石的量和重晶石中Ba的同位素组成对发生在过渡带的过程都可能是敏感的。然而，关于钡在海洋中的循环仍然存在一些长期存在的问题，这使得对钡基代理记录的解释变得复杂。剩余问题的例子包括有多少钡进入大洋中脊热液区的海洋，以及是什么控制了水柱中重晶石的沉淀和溶解。该项目旨在通过在太平洋和南大洋的三次预定研究考察，采用新的方法解决这些问题。在这样做的过程中，该项目将支持研究生，博士后研究员和初级研究员的教育，培训和职业发展。来自代表性不足群体的本科生将被招募进行补充岸基实验。这项建议旨在回答四个问题的核心效用的钡为基础的代理在海洋学：什么是新Ba的海洋的主要投入？它们的同位素组成是什么？在有机质的矿化过程中，是什么控制了远洋重晶石沉淀的数量？是什么影响了它的同位素组成？这些问题将解决使用现场为中心的方法相结合：在原位和船上的示踪剂孵化实验，AUV主导的自适应采样Ba循环“热点”，和基于部分的调查周围的海洋特征。这种多管齐下的办法将用于调查：从海洋中最大的热液区-东南太平洋海隆-释放的钡的通量和同位素组成，重点是低温喷发;与南大洋不同浮游植物组合有关的水层重晶石沉淀的速率和特征;环境条件的重要性，如低的环境氧浓度，在设置东部热带太平洋重晶石沉淀的效率。每个转变的重要性将被评估，这可能导致排除某些过程的重要性，或确定可能形成新代理基础的新依赖关系。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。

项目成果

Barium in seawater: dissolved distribution, relationship to silicon, and barite saturation state determined using machine learning

• DOI: 10.5194/essd-15-4023-2023
• 发表时间: 2023-09
• 期刊: Earth System Science Data
• 影响因子: 11.4
• 作者: Öykü Z. Mete;A. Subhas;Heather H. Kim;A. Dunlea;L. Whitmore;A. Shiller;Melissa Gilbert;William D. Leavitt;Tristan J. Horner

A spatially and vertically resolved global grid of dissolved barium concentrations in seawater determined using Gaussian Process Regression machine learning

使用高斯过程回归机器学习确定海水中溶解钡浓度的空间和垂直解析全局网格

• DOI: 10.26008/1912/bco-dmo.885506.2
• 发表时间: 2023
• 期刊: Biological and Chemical Oceanography Data Management Office (BCO-DMO
• 作者: Horner, Tristan J.;Mete, Oyku Z.
• 通讯作者: Mete, Oyku Z.

Barium isotope fractionation in barite–fluid systems at chemical equilibrium

• DOI: 10.1016/j.chemgeo.2023.121453
• 发表时间: 2023-03
• 期刊: Chemical Geology
• 影响因子: 3.9
• 作者: J. Middleton;Wei Hong;A. Paytan;M. Auro;E. Griffith;T. Horner

Bioactive Trace Metals and Their Isotopes as Paleoproductivity Proxies: An Assessment Using GEOTRACES‐Era Data

生物活性微量金属及其同位素作为古生产力指标：使用 GEOTRACES Era 数据进行评估

• DOI: 10.1029/2020gb006814
• 发表时间: 2021
• 期刊: Global Biogeochemical Cycles
• 影响因子: 5.2
• 作者: Horner, T. J.;Little, S. H.;Conway, T. M.;Farmer, J. R.;Hertzberg, J. E.;Janssen, D. J.;Lough, A. J. M.;McKay, J. L.;Tessin, A.;Galer, S. J. G.
• 通讯作者: Galer, S. J. G.

Microbial functional diversity across biogeochemical provinces in the central Pacific Ocean.

• DOI: 10.1073/pnas.2200014119
• 发表时间: 2022-09-13
• 期刊: PROCEEDINGS OF THE NATIONAL ACADEMY OF SCIENCES OF THE UNITED STATES OF AMERICA
• 影响因子: 11.1
• 作者: Saunders, Jaclyn K.;McIlvin, Matthew R.;Dupont, Chris L.;Kaul, Drishti;Moran, Dawn M.;Horner, Tristan;Laperriere, Sarah M.;Webb, Eric A.;Bosak, Tanja;Santoro, Alyson E.;Saito, Mak A.
• 通讯作者: Saito, Mak A.