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

国际地质勘测方案是一项多国努力，目的是(通过一系列跨大洋断面)调查和了解全球海洋海水中微量元素和同位素的分布情况。地球科学计划已将天然放射性同位素231pa和230pa指定为关键参数，因为它们在所有部分的测量被认为对整个国际海洋科学项目的成功至关重要，来自哥伦比亚大学Lamont-Doherty地球天文台和明尼苏达大学双子城大学的一个研究小组将对美国GEOTRACES秘鲁-塔希提部分的230和231pa的溶解浓度和颗粒浓度进行测量，这是美国对全球地球物理研究的贡献之一。此外，他们将测量溶解和颗粒的232Th浓度，并分析有限数量的气溶胶样本、气溶胶渗滤液和地表沉积物中的这些放射性核素。这些数据将用于：1)量化与生物生产力秘鲁上升流系统有关的231Pa230Th的边界清除速率，2)量化被认为与云母层中的再悬浮沉积物有关的231Pa230Th的底部清除速率，3)量化与东太平洋隆起的热液羽流有关的金属颗粒以及在最低含氧区形成的自生颗粒对溶解Th和Pa的吸收，4)通过232Th和230Th的联合研究，量化边缘沉积物的成岩232Th供应，以及5)通过232Th和230Th的联合研究，定量232Th气溶胶的供应。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痕量元素的过程以及清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.