Collaborative Research: US GEOTRACES Pacific Zonal Transect: Rates of supply, removal and internal cycling of trace elements and isotopes

GEOTRACES的目标是确定控制海洋中微量元素和同位素(TEI)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。虽然许多TEI的分布将由一大批GEOTRACES PI沿该样带绘制，但如果不同时测量能够提供边界和界面上的内部TEI循环过程和通量的速率的示踪剂，则无法正确解释它们的分布。自然生成的铀-钍系列放射性同位素非常适合于在时间和空间尺度上研究TEI的源和汇，这是解释TEI横向和垂直分布所必需的。在这个项目中，来自伍兹霍尔海洋研究所和南卡罗来纳大学哥伦比亚分校的一个研究小组将在美国GEOTRACES邮轮上对前往东热带南太平洋(ETSP)的一套铀/钍系列放射性核素进行测量。这套放射性示踪剂将包括寿命较短的第234次和第228次放射性示踪剂以及Re四重元素(224Ra、223Ra、228Ra、226Ra)，它们共同允许量化水平和垂直传输和混合的速率，以及海洋边界的清除、表面输出和次表层再矿化。更广泛的影响：PI积极地让本科生和高中生参与他们之前由NSF资助的项目，其中两个在最近几年的会议上获得了奖项。这一趋势将继续这一努力，并包括一名国际客座学生，他将致力于测量颗粒物228的分析改进。此外，两名世界卫生组织-麻省理工学院联合项目的学生将利用这个项目作为他们关于Th和Ra同位素的博士论文的主要部分。模型界热切期待着这6种同位素的结果对数据管理方面的贡献，因为在这些盆地尺度上，缺乏用于所有粒子反应性和生物活性TEI循环的参数的多个钍同位素数据集。

The goal of GEOTRACES is to identify processes and quantify fluxes that control the distribution of trace elements and isotopes (TEIs) in the ocean, and to establish the sensitivity of these distributions to changing environmental conditions. While the distribution of numerous TEIs will be mapped by a large team of GEOTRACES PIs along this transect, 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. Naturally-occurring radioisotopes of the Uranium-Thorium series are well suited for studying the sources and sinks of TEIs on time and space scales necessary to interpret lateral and vertical TEI distributions. In this project, a research team from the Woods Hole Oceanographic Institution and the University of South Carolina at Columbia will carry out measurement of a suite of uranium/thorium series radionuclides on the US GEOTRACES cruise to the Eastern Tropical South Pacific (ETSP) Ocean. This radiotracer suite will include shorter-lived 234Th and 228Th as well as the radium quartet (224Ra, 223Ra, 228Ra, 226Ra), which together allow the quantification of rates of horizontal and vertical transport and mixing, as well as removal at ocean boundaries, surface export, and subsurface remineralization. Broader Impacts: The PIs have actively involved undergraduate and high school students in their prior NSF-funded projects, with two having won awards at ASLO meetings in recent years. The trend will continue with this effort, along with the inclusion of an international guest student who will work on analytical improvements for measuring particulate 228Th. In addition, two WHOI-MIT Joint Program students will be involved using this project as a major part of their PhD theses on Th and Ra isotopes. Contributions to the data management side of the results from these 6 isotopes is eagerly awaited by the modeling community, where there is a lack of multiple thorium isotope data sets on these basin scales for parameterization of the cycling of all particle reactive and biologically active TEIs.