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.

海洋中碳的生物循环进入了许多其他元素，有些是直接的（例如对生命必不可少的营养物质），有些是间接的，因为它们在化学上与影响碳的过程有关。这样的元素是钡（BA）。已经发现，矿物质芳族的颗粒（硫酸钡）与海洋“暮光区”中有机材料的微生物消耗相关。这些颗粒沉降到海底，它们在沉积物中的存在已被用来推断海洋状况的及时变化。沉积物中的Barite量和BA中BA的同位素组成都可能对暮光区的过程敏感。但是，关于海洋中的BA骑自行车仍然存在一些长期的问题，这使基于钡的代理记录的解释变得复杂。剩余问题的例子包括在中山脊中水热位点进入海洋的多少，以及控制水柱中Barite的降水和溶解的原因。该项目旨在在太平洋和南大洋的三项预定研究探险中使用新方法解决这些问题。通过这样做，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。来自代表性不足的小组的本科生将被招募以进行完全基于海岸的实验。该提案试图回答有关海洋学基于钡的代理效用的核心的四个问题：新BA对海洋的主要投入是什么？他们的同位素成分是什么？是什么控制有机物的提案期间规定的闪光灯的量？是什么影响其同位素组成？这些问题将使用以场为中心的方法结合来​​解决：原位和船上示踪剂 - 固定实验，BA循环“热点”的AUV领导的自适应采样以及对周围海洋学特征的基于截面的测量。这种多管齐下的方法将用于研究：从海洋最大的水热田，东太平洋南部崛起释放的BA的通量和同位素组成，重点是低温通风；南海中与不同浮游植物组合相关的浮力稀沉沉淀的速率和特征；并且，环境条件的重要性，例如低环境氧浓度，在东部热带太平洋地区设定浓质降水效率方面的重要性。将评估每种转型的重要性，这可能导致排除某些过程的重要性，或确定可能构成新代理基础的新依赖性。该奖项反映了NSF的法定任务，并被认为是值得通过基金会的知识分子优点和更广泛影响的审查标准来通过评估来获得支持的。

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

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.

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.