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.

国际地理计划计划的目标是了解痕量化学元件及其同位素在海洋中的分布。该项目将支持从2018年在太平洋的2018年美国地理探险队的水上样品中的天然放射性同位素actactinium-227（AC-227）测量，从阿拉斯加向南延伸到大塔希提岛。此外，研究人员计划在该项目收集的沉积物核心中分析铅-210和阳式227，以将AC-227的来源限制在底部沉积物中的水中。在水柱中测量AC-227的值，特别是在知道底部源功能的情况下，可能在于使用它来测量水的混合和运输速率。然后可以应用这些运输估计值以了解探险中测量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，并向当地退伍军人团体推广，鼓励他们参加STEM计划。尽管有一个半衰期（22年），这非常适合研究在深海中，垂直和横向运输都是在深海中进行的AC-227测量。仪器的最新进展促进了这一分析，而GeoTraces计划提供的协同作用将为获取其他数据提供理想的机会。此外，AC-227在定义中部太平洋范围内混合速率的空间变异性方面将是有价值的，尤其是在基于RA-228（6年半寿命）分布的估计值时，这是一个示踪剂领域，将确定一个协作的地理环境程序。通过使用多个具有不同半衰期的示踪剂，可以区分混合和对流的影响，从而更完整地了解深太平洋动力学。然后可以将这些运输估计值应用于其他溶质的浓度领域，包括金属和营养素，但对于碱度和硅酸将特别重要，它们应该具有强大的底栖来源。此奖项反映了NSF的法定任务，并且被认为是值得的。通过基金会的智力优点和更广泛的影响评估标准通过评估来支持。