Collaborative Research: U.S. GEOTRACES GP17-OCE and GP17-ANT: Thorium-230, Thorium-232 and Protactinium-231 tracers of trace element supply and removal

合作研究：美国GEOTRACES GP17-OCE和GP17-ANT：Thorium-230、Thorium-232和Protactinium-231微量元素供应和去除示踪剂

• 批准号: 2048863
• 负责人: Christopher Hayes
• 金额: $ 46.18万
• 依托单位: University of Southern Mississippi
• 依托单位国家: 美国
• 项目类别: Continuing Grant
• 财政年份: 2021
• 资助国家: 美国
• 起止时间: 2021-07-01 至 2024-06-30
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=2048863&HistoricalAwards=false
• 关键词: Collaborative; Research; U.S.; GEOTRACES; GP17

The goal of the international GEOTRACES program is to understand the distributions of trace chemical elements and their isotopes in the oceans. Many trace elements are essential for life and are thought to limit biological productivity throughout much of the ocean. This limitation, in turn, partly controls the ability of the ocean to support other marine life as well as the ocean's capacity to absorb carbon dioxide from the atmosphere. This project will provide constraints on the processes that supply and remove trace elements in the South Pacific Ocean and Amundsen Sea which are currently not well quantified. Naturally occurring radioactive isotopes such as thorium-230 and protactinium-231, which will be measured as a part of this work, can be utilized as proxies to provide critical information about the processes that supply iron and other micronutrient elements, as well as the rates of those processes. The isotope thorium-232 will also be utilized as a tracer of the supply of elements that are added to the ocean through the deposition of aerosol dust and from coastal sediments. These rates and fluxes can be used to improve our understanding of the micro-nutrient iron and the sinking fluxes of carbon which are both critical in the global carbon cycle. Outreach and broader impacts will be achieved through undergraduate and graduate teaching, community events such as the Ocean Sciences Bowl and other efforts through the international GEOTRACES program. This project will provide support for four collaborating labs (University of Southern Mississippi, University of Minnesota, Lamont-Doherty at Columbia University and CalTech) to undertake measurements on two US GEOTRACES cruises in the South Pacific, known as GP17 (GP17-OCE running from Tahiti south to the marginal sea ice zone and GP17-ANT focusing on the Amundsen margin). The PIs will measure dissolved and particulate concentrations of Th-230 and Pa-231. In addition, they will measure dissolved and particulate Th-232 concentrations and analyze a limited number of aerosol samples, aerosol leachates, colloidal size fractions and surface sediments for these radionuclides. They will be used to quantify trace element supply, including sedimentary inputs from the Amundsen Sea’s glacial meltwater pump and atmospheric dust inputs in one of the world’s lowest dust input regions. Additionally, the team will be able to quantify trace element removal, including sinking particulate fluxes for carbon, as well as trace elements, and scavenging characteristics of variable particle composition regimes. These goals also contribute to assessing Th and Pa as key palaeoceanographic proxies.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.

国际 GEOTRACES 计划的目标是了解海洋中微量化学元素及其同位素的分布，许多微量元素对生命至关重要，并且被认为在一定程度上限制了整个海洋的生物生产力。控制海洋支持其他海洋生物的能力以及海洋从大气中吸收二氧化碳的能力。该项目将对目前在南太平洋和阿蒙森海供应和去除微量元素的过程进行限制。不太好天然存在的放射性同位素，如钍 230 和镤 231，将作为这项工作的一部分进行测量，可用作提供有关铁和其他微量营养元素供应过程的关键信息。同位素钍232也将被用作通过气溶胶灰尘和沉积物添加到海洋中的元素供应的示踪剂。这些速率和通量可用于提高我们对微量营养物铁和碳沉没通量的理解，这对全球碳循环至关重要，并将通过本科生和研究生教学实现更广泛的影响，该项目将为四个合作实验室（南密西西比大学、明尼苏达大学、哥伦比亚大学拉蒙特-多尔蒂大学和加州理工学院）提供支持，以对两个实验室进行测量。我们南太平洋的 GEOTRACES 巡航，称为 GP17（GP17-OCE 从塔希提岛南部到边缘海冰区，GP17-ANT 重点关注阿蒙森边缘）。 PI 将测量 Th-230 和 Pa- 的溶解浓度和颗粒物浓度。 231. 此外，他们将测量溶解的和颗粒的 Th-232 浓度，并分析有限数量的气溶胶样品、气溶胶浸出物、胶体尺寸分数和这些放射性核素的表面沉积物将用于量化微量元素供应，包括来自阿蒙森海冰川融水泵的沉积物输入和世界上灰尘输入量最低的地区之一的大气灰尘输入。此外，该团队还将能够量化微量元素。元素去除，包括碳的下沉颗粒通量以及微量元素，以及可变颗粒成分状况的清除特征，这些目标也有助于评估 Th 和 Pa 作为关键的古海洋学。该奖项反映了 NSF 的法定使命，并通过使用基金会的智力价值和更广泛的影响审查标准进行评估，被认为值得支持。