GEOTRACES Arctic Section: Actinium-227 as a Naturally-occurring Tracer of Dissolved Material Transport in the Arctic Ocean

在这个项目中，一组参加2015年美国地理跟踪北极探险队的调查人员将测量北冰洋中Actdium-227的剖面，这是一种天然存在的放射性同位素，可用作海水运动的示踪剂。与国际地质勘测计划中的其他多国倡议一样，美国北极探险的目标是确定控制海洋中关键微量元素和同位素分布的过程和通量，并确定这些分布对不断变化的环境条件的敏感性。一些微量元素对生命是必不可少的，另一些是已知的生物毒素，还有一些很重要，因为它们可以用作海洋中各种物理、化学和生物过程的示踪剂。作为这项研究的一部分，测量的同位素Actdium-227的半衰期为22年，因此非常适合作为北冰洋混合和溶质运输的示踪剂。这项研究将为高中生和本科生提供科学研究方面的教育机会。量化深海的生物地球化学动力学对于了解海洋碳循环是必要的。尽管其半衰期非常适合于研究深海中的垂直和横向运输，但在深海中几乎没有进行过Ac-227的测量。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提供一个理想的机会，以获得更多的数据，这将服务于两个目的。这项研究中测量到的Ac-227将有助于确定边界交换率，特别是在与以Re-228为基础(作为另一项单独裁决的一部分进行测量)的估计相结合时，并将有助于推断GEOTRACES测量的其他溶质在深水中的迁移和动态。通过使用具有不同半衰期的多个示踪剂，可以区分这些过程的不同作用，从而允许更全面地了解溶质行为的动力学。

In this project, a group of investigators participating in the 2015 U.S. GEOTRACES Arctic expedition will measure profiles of actinium-227, a naturally-occurring radioisotope that can be used as a tracer of oceanic water movement, in the Arctic Ocean. In common with other multinational initiatives in the International GEOTRACES Program, the goals of the U.S. Arctic expedition are to identify processes and quantify fluxes that control the distributions of key trace elements and isotopes in the ocean, and to establish the sensitivity of these distributions to changing environmental conditions. Some trace elements are essential to life, others are known biological toxins, and still others are important because they can be used as tracers of a variety of physical, chemical, and biological processes in the sea. The isotope measured as part of this study, actinium-227, has a 22 year half-life, making it well-suited as a tracer of mixing and solute transport in the Arctic Ocean. This study will involve educational opportunities in scientific research for high school and undergraduate students.Quantifying the biogeochemical dynamics of the deep sea is necessary to understand the ocean carbon cycle. Despite having a half-life that is well suited for the study of both vertical and lateral transport in the deep ocean, few actinium-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 that will serve two purposes. The measurements of actinium-227 from this study will aid in defining the rates of boundary exchange, particularly when combined with estimates based on radium-228 (measured as part of a separate award) and will be useful for deducing the transport and the dynamics of other solutes measured by GEOTRACES in deep waters. By using multiple tracers with different half-lives, the separate roles of these processes may be distinguished, allowing a more complete understanding of the dynamics of solute behaviors.