Collaborative Research: U.S. GEOTRACES Pacific Section: Analysis of 230Th, 232Th and 231Pa

国际GEOTRACES计划是一项多国努力，旨在调查（通过一系列跨洋剖面）和了解海水中微量元素和同位素的全球海洋分布。 GEOTRACES科学计划指定天然放射性同位素231 Pa和230 Th为关键参数，因为它们在所有剖面上的测量被认为对整个国际海洋科学计划的成功至关重要。来自哥伦比亚大学和明尼苏达大学的拉蒙-多尔蒂地球观测站的一个研究小组，双子城将在美国GEOTRACES秘鲁-塔希提岛部分测量230 Th和231 Pa的溶解和颗粒浓度，这是美国对全球GEOTRACES工作的贡献之一。 此外，他们将测量溶解和颗粒232 Th浓度，并分析有限数量的气溶胶样品，气溶胶沥滤物和表面沉积物中的放射性核素。 这些数据将用于：1）量化与生物生产性秘鲁上升流系统相关的231 Pa和230 Th的边界清除率，2）量化被认为与云状层中再悬浮沉积物相关的231 Pa和230 Th的底部清除率，第三章量化与东太平洋海隆热液羽流有关的含金属颗粒以及东太平洋海隆内形成的自生颗粒对溶解Th和Pa的吸收，利用232 Th和230 Th的联合研究定量了边缘沉积物中成岩232 Th的供应量;利用232 Th和230 Th的联合研究定量了气溶胶中成岩232 Th的供应量。通过与其他美国GEOTRACES调查人员的合作，该团队预计这项工作将对向海洋提供微量元素的过程以及去除它们的过程提供前所未有的限制。更广泛的影响。 该项目将为一名博士后研究助理和一名研究生提供培训和支助。

The International GEOTRACES program is a multi-national effort to survey (by a series of cross-ocean sections) and understand the global-ocean distribution of trace elements and isotopes in seawater. The GEOTRACES Science Plan has designated the natural radioisotopes 231Pa and 230Th to be key parameters inasmuch as their measurement on all sections is deemed to be critical to the success of entire international ocean science programIn this project, a research team from the Lamont- Doherty Earth Observatory of Columbia University and the University of Minnesota - Twin Cities will undertake measurement of the dissolved and particulate concentrations of 230Th and 231Pa on the US GEOTRACES Peru-Tahiti section, one of the American contributions to the global GEOTRACES effort. Additionally, they will measure dissolved and particulate 232Th concentrations and analyze a limited number of aerosol samples, aerosol leachates, and surface sediments for these radionuclides. These data will be used to: 1) Quantify the rates of boundary scavenging of 231Pa and 230Th associated with the biologically productive Peru upwelling system, 2) Quantify the rates of bottom scavenging of 231Pa and 230Th thought to be associated with resuspended sediments in nepheloid layers, 3) Quantify the uptake of dissolved Th and Pa by metalliferous particles associated with the hydrothermal plume emanating from the East Pacific Rise as well as by authigenic particles formed within the oxygen minimum zone, 4) Quantify the supply of lithogenic 232Th from margin sediments by the combined study of 232Th and 230Th, and 5) Quantify the supply of lithogenic 232Th from aerosols by the combined study of 232Th and 230Th. Through collaboration with other US GEOTRACES investigators, the team expects that this work will provide unprecedented constraints on the processes that supply trace elements to the ocean as well as the processes that remove them. Broader Impacts. The project will provide for the training and support of a postdoctoral research associate and one graduate student.