Collaborative Research: GEOTRACES Arctic Section: Radium and Thorium Isotopes as Natural Geochemical Tracers in the Arctic Ocean

在这个项目中，参加2015年美国GEOTRACES北极考察的研究人员将测量北冰洋西部的镭和钍同位素。与国际GEOTRACES计划中的其他国家倡议一样，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，并确定这些分布对环境条件变化的敏感性。一些微量元素是生命所必需的，另一些是已知的生物毒素，还有一些是重要的，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。作为该项目的一部分，将测量的放射性核素很重要，因为它们是海洋学示踪剂，可提供关于其他微量元素循环速率的信息。该项目将为研究生研究人员和代表性不足群体的本科生提供培训机会。研究结果将通过伍兹霍尔海洋研究所公开分享。虽然其他GEOTRACES项目将绘制许多微量元素及其同位素（TEI）的分布图，但如果不同时测量能够提供边界和界面处内部TEI循环过程和通量速率的示踪剂，则无法正确解释其分布。该项目将测量的同位素包括一套铀/钍系列放射性核素，包括寿命较短的234-Th和228-Th以及镭四重态（224-Ra、223-Ra、228-Ra、226-Ra）。这些示踪剂具有适当的半衰期和反应性，可用于研究水平和垂直迁移和混合，以及在海洋边界的迁移、通过河流和海底地下水排放的供应、表面清除和输出以及地下矿化。研究人员在开发和实施最有效的方法来采样和量化这套示踪剂方面有相当丰富的经验，其中包括使用电池供电的原位泵进行大体积采样。因此，除了关于铀/钍系列放射性核素的拟议工作外，该小组还将通过协调泵的使用和对许多基本颗粒TEI的采样，为其他GEOTRACES研究人员提供服务。

In this project, investigators participating in the 2015 U.S. GEOTRACES Arctic expedition will measure radium and thorium isotopes in the western Arctic Ocean. In common with other national 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 radionuclides to be measured as part of this project are important because they are oceanographic tracers that provide information on rates of cycling of other trace elements. The project will involve training opportunities for graduate student researchers and for undergraduate students from under-represented groups. Results from the study will be shared publicly through the Woods Hole Oceanographic Institution?s Center for Marine and Environmental Radioactivity.While other GEOTRACES projects will map the distribution of numerous trace elements and their isotopes (TEIs), their distribution cannot be properly interpreted without concurrent measurement of tracers capable of providing rates of internal TEI cycling processes and fluxes at boundaries and across interfaces. The isotopes to be measured in this project include a suite of uranium/thorium series radionuclides, including the shorter-lived 234-Th and 228-Th as well as the radium quartet (224-Ra, 223-Ra, 228-Ra, 226-Ra). These tracers have the appropriate half-lives and reactivities to allow for study of horizontal and vertical transport and mixing, as well as removal at ocean boundaries, supply via rivers and submarine groundwater discharge, surface scavenging and export and subsurface remineralization. The researchers have considerable experience developing and implementing the most efficient methods to sample and quantify this suite of tracers, which includes use of battery powered in-situ pumps for large volume sampling. Hence, in addition to the proposed work on uranium/thorium series radionuclides, the team will also provide a service to other GEOTRACES researchers by coordinating pump use and sampling for many essential particulate TEIs.