Collaborative Research: U.S. GEOTRACES GP17-OCE and GP17-ANT: Thorium-230, Thorium-232 and Protactinium-231 as 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作为微量元素供应和去除的示踪剂

• 批准号: 2049204
• 负责人: Robert Anderson
• 金额: $ 90万
• 依托单位: Columbia University
• 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=2049204&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.

国际地学研究计划的目标是了解海洋中痕量化学元素及其同位素的分布。许多微量元素是生命所必需的，被认为限制了海洋大部分地区的生物生产力。反过来，这种限制又部分控制了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。该项目将对供应和清除南太平洋和阿蒙森海中目前尚未很好量化的痕量元素的过程提供制约。将作为这项工作的一部分进行测量的自然产生的放射性同位素，如钍-230和钚-231，可作为替代物，提供有关供应铁和其他微量营养素的过程以及这些过程的速率的关键信息。同位素钍-232还将被用作元素供应的示踪剂，这些元素通过气溶胶尘埃的沉积和沿海沉积物添加到海洋中。这些速率和通量可以用来提高我们对微营养铁和碳的下沉通量的理解，这两种物质在全球碳循环中都是至关重要的。将通过本科生和研究生教学、社区活动(如海洋科学碗)以及通过国际地球轨道系统计划的其他努力来实现推广和更广泛的影响。该项目将支持四个合作实验室(南密西西比大学、明尼苏达大学、哥伦比亚大学的Lamont-Doherty和加州理工学院)对美国在南太平洋的两次GEOTRACES邮轮GP17进行测量(GP17-OCE从塔希提岛南部到边缘海冰地带，而GP17-ANT侧重于阿蒙森边缘)。PI将测量Th-230和PA-231的溶解和颗粒浓度。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本、气溶胶渗滤液、胶体组分和表层沉积物中的这些放射性核素。它们将被用于量化痕量元素的供应，包括来自阿蒙森海冰川融水泵的沉积输入，以及世界上粉尘输入最低的地区之一的大气粉尘输入。此外，该团队将能够量化痕量元素的去除，包括碳的沉降性颗粒通量以及痕量元素，以及不同颗粒组成制度的清除特性。这些目标也有助于评估Th和Pa作为关键的古海洋学指标。这一裁决反映了NSF的法定使命，并通过使用基金会的智力优势和更广泛的影响审查标准进行评估，被认为值得支持。