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

• 批准号: 1827431
• 负责人: Adina Paytan
• 金额: $ 9.32万
• 依托单位: University of California-Santa Cruz
• 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 2020-05-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1827431&HistoricalAwards=false
• 关键词: Collaborative; Research; Calibration; Validation; Application

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.

海洋的生物泵是指从阳光下海洋到深海和海底的一组化学，物理和生物学过程。在全球范围内，该泵在调节二氧化碳的空气平衡方面具有重要作用，因此可能影响地球的气候。但是，由于存在太多变量，而且海洋如此之大，因此无法直接完成海洋生物泵强度和效率的波动。因此，使用对复杂过程具有特定可测量响应的地球化学指标，称为代理。海洋生物泵的大多数地球化学代理仅对当地条件敏感。这项研究涉及对新型地球化学示踪剂（矿物质稀释液中稳定的钡同位素）的探索，校准和验证，该示踪剂（矿物质稀释液中的稳定同位素）被认为对区域规模的生物地球化学过程敏感。为了检查该示踪剂，将与赤道太平洋的海洋沉积物核心分离。 Barite的发生被广泛解释为反映了与海洋生物泵有关的局部生物地球化学过程。因此，拟议的代理具有同时揭示有关本地和区域规模过程的信息，尽管对代理信号的可靠解释首先需要在现代设置中进行校准和验证。这项研究旨在在赤道太平洋的一组核心中对该代理进行校准和验证。可以预料，钡同位素方法将弥合生物地球化学缩放鸿沟，并在整个地球历史上更准确地重建生物碳泵。 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，参与科学领域不足的学生的研究，支持早期职业科学家的学生的研究，并支持一名研究人员的性别不足。这项研究重点是研究海洋稀释液的钡 - 异位分析的效用，以在区域空间尺度上重建海洋的碳循环。该项目涉及一种两条钢琴的方法。研究的第一阶段需要通过对赤道太平洋的现代核心沉积物进行广泛的调查来对代理本身进行校准。将分析共同确定的沉积物和孔隙水的样品。 Barite将通过酸消化和其他分离技术与核心分离，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分析。在确保稀晶样品的纯度之后，将针对每个核心顶部测量Barite的钡稳定同位素。研究的第二阶段通过分析共同置换的矿物分离和孔隙水地球化学来评估核心降低核心过程中代理的保真度。工作的这一阶段测试了在海底埋葬后是否发生了多少钡 - 异位修饰。第一阶段和第二阶段的结果将用于确定海洋Barite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新型手段，以重建区域规模的海洋碳循环，这将在一系列时间标准上具有实用性。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的影响审查审查的审查标准来通过评估来获得支持的。

项目成果

Possible triggers of the seawater sulfate S-isotope increase between 55 and 40 million years ago

• DOI: 10.1016/j.chemgeo.2020.119788
• 发表时间: 2020-07
• 期刊: Chemical Geology
• 影响因子: 3.9
• 作者: W. Yao;A. Paytan

Barite formation in the ocean: Origin of amorphous and crystalline precipitates

• DOI: 10.1016/j.chemgeo.2018.09.011
• 发表时间: 2019-04
• 期刊: Chemical Geology
• 影响因子: 3.9
• 作者: F. Martínez-Ruiz;A. Paytan;M. T. González-Muñoz;F. Jroundi;M. M. Abad-M.;P. Lam;J. Bishop;T. Horner;P. Morton;M. Kastner

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

• 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: Crockford, Peter W.;Wing, Boswell A.;Horner, Tristan J.
• 通讯作者: Horner, Tristan J.

Toward an Improved Understanding of the Marine Barium Cycle and the Application of Marine Barite as a Paleoproductivity Proxy

• DOI: 10.3390/min10050421
• 发表时间: 2020-05-01
• 期刊: MINERALS
• 影响因子: 2.5
• 作者: Carter, Samantha C.;Paytan, Adina;Griffith, Elizabeth M.
• 通讯作者: Griffith, Elizabeth M.