Collaborative Research: U.S. GEOTRACES Pacific Meridional Transect: Thorium-232, Thorium-231 and Protactinium-231 as tracers of trace element supply and removal

合作研究：美国 GEOTRACES 太平洋经线横断面：Thorium-232、Thorium-231 和 Protactinium-231 作为微量元素供应和去除的示踪剂

• 批准号: 1737224
• 负责人: Robert Anderson
• 金额: $ 69.96万
• 依托单位: Columbia University
• 依托单位国家: 美国
• 项目类别: Continuing Grant
• 财政年份: 2017
• 资助国家: 美国
• 起止时间: 2017-11-01 至 2023-10-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1737224&HistoricalAwards=false
• 关键词: Collaborative; Research; U.S.; GEOTRACES; Pacific

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 their extremely low concentrations in seawater are thought to limit biological productivity (fertility) throughout much of the ocean. This limitation, in turn, partially constrains the level of fisheries that can be supported by marine ecosystems as well as the ocean's capacity to absorb carbon dioxide from the atmosphere. Whereas the importance of these trace-element micronutrients is well established, many basic features of their ocean distribution remain unknown. Measurements of other elements and isotopes can be used to understand the processes that influence the distributions of the micronutrient elements. Two naturally-occurring radioactive isotopes that are particularly important in this regard are thorium-230 and protactinium-231, which have been designated as key parameters to be measured as part of GEOTRACES. This project will focus on the measurement of these two isotopes in order to provide critical information about the processes that supply iron to the Pacific Ocean, as well as the rates of those processes. The project will support an early career investigator, a postdoctoral researcher, and students at the undergraduate and graduate levels.Samples of seawater and of suspended particulate material will be collected along a north-south transect between Alaska and Tahiti to examine the processes that supply and remove trace elements. These samples will be analyzed for naturally-occurring radionuclides thorium-232, thorium-230 and protactinium-231. Aerosol samples and sediments collected along the transect will be analyzed as well. In collaboration with other investigators involved in the expedition, this project will:1) Interpret the distributions of thorium-232 and thorium-230 to quantify the supply of iron and other trace elements delivered by dust as well as the trace elements supplied by chemical reactions in volcanic sediments along the Alaskan margin, 2) Determine the sinking flux of major particulate phases and of particulate trace elements throughout the water column to quantify their rate of removal from the ocean, and 3) Compare the rate of trace element removal among contrasting environmental regimes to be encountered along the Alaska to Tahiti transect to identify the key physical, chemical and biological factors, such as dust supply and biological productivity, that regulate the rate of trace element removal from the ocean.

国际地理计划计划的目标是了解痕量化学元件及其同位素在海洋中的分布。许多痕量元素对生命至关重要，它们在海水中的极低浓度被认为限制了整个海洋的生物生产力（生育能力）。反过来，这种局限性部分限制了海洋生态系统可以支持的渔业水平以及海洋从大气中吸收二氧化碳的能力。尽管这些痕量元素微量营养素的重要性已经很好，但其海洋分布的许多基本特征仍然未知。其他元素和同位素的测量可用于了解影响微量营养素元素分布的过程。在这方面尤其重要的两个自然出现的放射性同位素是Thorium-230和Protactinium-231，它们已被指定为要作为地理位置的一部分测量的关键参数。该项目将重点介绍这两个同位素的测量，以便提供有关为太平洋提供铁的过程以及这些过程的速率的关键信息。该项目将支持早期的职业研究员，博士后研究人员以及本科生和研究生级别的学生。海水的样本和悬浮的颗粒物材料将沿着阿拉斯加和塔希提岛之间的南北横向收集，以检查供应和删除微量元素的过程。这些样品将分析为天然存在的放射性核素232，Thorium-230和Protactinium-231。也将分析沿横切收集的气溶胶样品和沉积物。该项目与参与探险的其他研究人员合作，将：1）解释thorium-232和Thorium-230的分布，以量化灰尘传递的铁和其他微量元素的供应以及灰尘所提供的其他微量元素，以及由化学反应提供的痕量元素沿着阿拉斯加地区的沿着阿拉斯加余量的沿沿着阿拉斯加余量的量相关量的痕迹和量化量的痕迹的痕迹，并确定粒子范围的下水道，并确定遍布均值的范围。比较沿阿拉斯加遇到的对比鲜明的环境方案之间的微量元素去除速率与大溪地样带，以确定调节从海洋中删除痕量元素的速率的关键物理，化学和生物学因素，例如灰尘供应和生物生产力。