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U.S. GEOTRACES Pacific Meridional Transect: Measurements of Actinium-227 to Trace Solute Transport

美国 GEOTRACES 太平洋经线横断面：通过测量 Actinium-227 来追踪溶质迁移

基本信息

批准号：
1830168
负责人：
Douglas Hammond
金额：
$ 13.88万
依托单位：
University of Southern California
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：
2018-08-15 至 2022-07-31
项目状态：
已结题

来源：
https://www.nsf.gov/awardsearch/showAward?AWD_ID=1830168&HistoricalAwards=false
关键词：
U.S.GEOTRACES Pacific Meridional Transect

项目摘要

The goal of the international GEOTRACES program is to understand the distributions of trace chemical elements and their isotopes in the oceans. This project will support the measurement of the naturally occurring radioisotope actinium-227 (Ac-227) in water samples from the 2018 U.S. GEOTRACES expedition in the Pacific Ocean, running south from Alaska to Tahiti. In addition, the investigators plan to analyze lead-210 and actinium-227 in sediment cores collected by the project, in order to constrain the source of Ac-227 to the water from bottom sediments. The value of measuring Ac-227 in the water column, particularly if the bottom source function is known, lies in the potential to use it to measure rates of mixing and transport of the water. These transport estimates can then be applied to understand the distributions of other trace elements measured on the expedition. The project would support a graduate student, several undergraduates, and a high school student, as well as outreach to local veterans groups encouraging their participation in STEM programs.Despite having a half-life (22 years) that is well suited for the study of both vertical and lateral transport in the deep ocean, few Ac-227 measurements have been made in the deep sea. Recent advances in instrumentation facilitate this analysis, and the synergy provided by the GEOTRACES program will provide an ideal opportunity to obtain additional data. In addition, Ac-227 will be of value in defining the spatial variability of mixing rates across a broad reach of the central Pacific, particularly when combined with estimates based on Ra-228 (6 year half-life) distribution, a tracer field that a collaborating GEOTRACES program will determine. By using multiple tracers with different half-lives, influences of mixing and advection may be distinguished, allowing a more complete understanding of the deep Pacific dynamics. These transport estimates can then be applied to concentration fields of other solutes, including metals and nutrients, but will be of particular importance for alkalinity and silicic acid, which should have strong benthic sources.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.

国际GEOTRACES项目的目标是了解海洋中微量化学元素及其同位素的分布。该项目将支持测量2018年美国GEOTRACES探险队在太平洋（从阿拉斯加向南到塔希提岛）采集的水样中天然存在的放射性同位素锕-227 （Ac-227）。此外，研究人员计划分析该项目收集的沉积物岩心中的铅-210和锕-227，以便将Ac-227的来源限制在底部沉积物的水中。测量水柱中Ac-227的价值，特别是在已知底源函数的情况下，在于有可能用它来测量水的混合率和输送率。这些运输估计可以用来了解考察中测量到的其他微量元素的分布。该项目将支持一名研究生、几名本科生和一名高中生，并与当地退伍军人团体联系，鼓励他们参与STEM项目。尽管Ac-227的半衰期（22年）非常适合研究深海中的垂直和横向输送，但在深海中很少进行Ac-227的测量。仪器仪表的最新进展促进了这种分析，GEOTRACES程序提供的协同作用将为获得额外数据提供理想的机会。此外，Ac-227在确定太平洋中部广阔海域混合率的空间变异性方面具有价值，特别是与基于Ra-228（6年半衰期）分布的估计相结合时，这是GEOTRACES合作项目将确定的示踪剂领域。通过使用具有不同半衰期的多种示踪剂，可以区分混合和平流的影响，从而更全面地了解太平洋深部动力学。然后，这些迁移估计可以应用于其他溶质的浓度领域，包括金属和营养物，但对碱度和硅酸将特别重要，因为它们应该有很强的底栖生物来源。该奖项反映了美国国家科学基金会的法定使命，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。