Collaborative Research: Calibration, Validation, and Application of Barium Isotopes in Marine Barite as a Tracer of the Marine Carbon Cycle

合作研究：海洋重晶石中钡同位素的校准、验证和应用作为海洋碳循环示踪剂

基本信息

批准号：
1827401
负责人：
Tristan Horner
金额：
$ 14.16万
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：
2018
资助国家：
美国
起止时间：
2018-06-15 至 2019-12-31
项目状态：
已结题

来源：
https://www.nsf.gov/awardsearch/showAward?AWD_ID=1827401&HistoricalAwards=false
关键词：
Collaborative Research Calibration Validation Application

项目摘要

The ocean's biological pump refers to a set of chemical, physical, and biological processes that redistribute carbon and nutrients from the sunlit upper ocean to the deep ocean and seafloor. Globally, this pump has an important role in modulating the air-sea balance of carbon dioxide and can thus impact Earth's climate. However, reconstructing fluctuations in the strength and efficiency of the oceans biological pump cannot be done directly because there are so many variables in play and the ocean is so large. Thus, geochemical indicators, called proxies, that have a specific measurable response to a complex process are used. Most geochemical proxies for the ocean biological pump are sensitive only to local conditions. This research involves the exploration, calibration, and validation of a novel geochemical tracer (the stable isotopes of barium in the mineral barite) that is hypothesized to be sensitive to regional-scale biogeochemical processes. To examine this tracer, barite will be separated from marine sediment cores from the Equatorial Pacific. Barite's occurrence is widely interpreted as reflecting local biogeochemical processes related to the ocean's biological pump. Thus, the proposed proxy has the benefit of simultaneously revealing information on both local- and regional-scale processes, though reliable interpretation of proxy signals first requires calibration and validation in modern settings. This research sets out to do the calibration and validation of this proxy in a set of cores from the Equatorial Pacific Ocean. It is anticipated that the barium isotope approach will bridge the biogeochemical scaling divide and enable more accurate reconstructions of the biological carbon pump throughout Earth's history. Broader impacts of the work include student training, building infrastructure for science by developing a new biogeochemical proxy, engagement in the research of students from groups underrepresented in the sciences, support an early career scientist, and support of a researcher whose gender is underrepresented in the sciences. This research focuses on examining the utility of barium-isotopic analyses of marine barite to reconstruct the ocean's carbon cycle over regional spatial scales. The project involves a two pronged approach. Phase one of the research entails calibration of the proxy itself by means of an extensive survey of modern core-top sediments from the Equatorial Pacific. Samples of co-located sediments and pore waters will be analyzed. Barite will be separated from the cores via acid digestion and other separation techniques and examined for purity using a scanning electron microscope and its integrated chemical analyzer. Pore waters will be analyzed by standard wet-chemical techniques. After ensuring purity of the barite samples, the barium stable isotopes of the barite will be measured for each of the core tops. Phase two of the research assesses the fidelity of the proxy during diagenetic alteration down core via the analysis of co-located mineral separates and pore water geochemistry. This stage of the work tests whether and how much barium-isotopic modification occurs after burial on the seafloor. Results from phase one and two will be used to establish whether the barium-isotopic composition of marine barite faithfully records ocean biogeochemistry. If so, this project will have successfully calibrated and validated a novel means to reconstruct regional-scale marine carbon cycling, which will have utility over a range of timescales.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.

海洋生物泵是指将碳和营养物质从阳光照射的上层海洋重新分配到深海和海底的一系列化学、物理和生物过程。在全球范围内，该泵在调节二氧化碳的气海平衡方面发挥着重要作用，因此可以影响地球的气候。然而，无法直接重建海洋生物泵的强度和效率的波动，因为影响因素太多，而且海洋太大。因此，使用地球化学指标（称为代理），对复杂过程具有特定的可测量响应。海洋生物泵的大多数地球化学代理仅对当地条件敏感。这项研究涉及一种新型地球化学示踪剂（矿物重晶石中钡的稳定同位素）的探索、校准和验证，假设该示踪剂对区域规模的生物地球化学过程敏感。为了检查这种示踪剂，将从赤道太平洋的海洋沉积物岩心中分离出重晶石。重晶石的出现被广泛解释为反映了与海洋生物泵相关的当地生物地球化学过程。因此，所提出的代理具有同时揭示局部和区域尺度过程信息的优点，尽管对代理信号的可靠解释首先需要在现代环境中进行校准和验证。这项研究的目的是在赤道太平洋的一组岩心中对该代理进行校准和验证。预计钡同位素方法将弥合生物地球化学尺度鸿沟，并能够更准确地重建整个地球历史上的生物碳泵。这项工作的更广泛影响包括学生培训、通过开发新的生物地球化学代理来建设科学基础设施、参与科学领域代表性不足群体的学生的研究、支持早期职业科学家以及支持性别在科学领域代表性不足的研究人员。科学。本研究的重点是研究海洋重晶石的钡同位素分析在区域空间尺度上重建海洋碳循环的效用。该项目涉及双管齐下的方法。研究的第一阶段需要通过对赤道太平洋现代核心顶部沉积物的广泛调查来校准代理本身。将分析同位沉积物和孔隙水的样本。重晶石将通过酸消化和其他分离技术从岩心中分离出来，并使用扫描电子显微镜及其集成化学分析仪检查纯度。孔隙水将通过标准湿化学技术进行分析。确保重晶石样品的纯度后，将对每个岩心顶部的重晶石的钡稳定同位素进行测量。该研究的第二阶段通过分析同位矿物分离物和孔隙水地球化学来评估岩心成岩蚀变过程中替代物的保真度。这一阶段的工作测试埋藏在海底后是否发生钡同位素改变以及发生程度如何。第一阶段和第二阶段的结果将用于确定海洋重晶石的钡同位素组成是否忠实地记录了海洋生物地球化学。如果是这样，该项目将成功校准和验证一种重建区域规模海洋碳循环的新方法，该方法将在一系列时间尺度上发挥作用。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。

项目成果

期刊论文数量（6）

专著数量（0）

科研奖励数量（0）

会议论文数量（0）

专利数量（0）

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：
2021-11
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.;et al
通讯作者：
et al

Barium-isotopic constraints on the origin of post-Marinoan barites

钡同位素对后马里诺时代重晶石起源的限制

DOI：
10.1016/j.epsl.2019.05.018
发表时间：
2019-08-01
期刊：
Earth and Planetary Science Letters
影响因子：
5.3
作者：
P. Crockford;B. Wing;A. Paytan;M. Hodgskiss;K. K. Mayfield;J. Hayles;Julia E. Middleton;A. Ahm
通讯作者：
A. Ahm

Barium isotope signatures of barite–fluid ion exchange in Equatorial Pacific sediments

赤道太平洋沉积物中重晶石-流体离子交换的钡同位素特征