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

在这个项目中，参加2015年美国GEOTRACES北极考察队的一组研究人员将测量锕-227的剖面，锕-227是一种天然存在的放射性同位素，可以用作北冰洋海水运动的示踪剂。与国际地质足迹计划中的其他多国倡议一样，美国北极考察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量化通量，并确定这些分布对不断变化的环境条件的敏感性。有些微量元素是生命所必需的，有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，锕-227，有22年的半衰期，使它非常适合作为北冰洋混合和溶质运输的示踪剂。本研究将涉及高中生和本科生的科研教育机会。量化深海生物地球化学动力学是了解海洋碳循环的必要条件。尽管锕-227的半衰期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测量。仪器仪表的最新进展促进了这种分析，GEOTRACES计划提供的协同作用将为获得额外数据提供理想的机会，这将满足两个目的。本研究中对锕-227的测量将有助于确定边界交换率，特别是当与基于镭-228的估计相结合时（作为单独奖励的一部分测量），并将有助于推断GEOTRACES在深水中测量的其他溶质的运输和动力学。通过使用具有不同半衰期的多种示踪剂，可以区分这些过程的不同作用，从而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.