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

合作研究：美国 GEOTRACES 北极部分：Thorium-230、Thorium-232 和 Protactinium-231 微量元素供应和清除示踪剂。

• 批准号: 1434886
• 负责人: Richard Edwards
• 金额: $ 45.49万
• 依托单位: University of Minnesota-Twin Cities
• 依托单位国家: 美国
• 项目类别: Continuing Grant
• 财政年份: 2015
• 资助国家: 美国
• 起止时间: 2015-01-01 至 2018-12-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1434886&HistoricalAwards=false
• 关键词: Collaborative; Research; U.S.; GEOTRACES; Arctic

In support of the 2015 U.S.GEOTRACES Arctic expedition, this project will focus on the fate and distributions of naturally-occurring radioisotopes in the Arctic Ocean. Such information is useful for understanding why other chemical substances, both natural and man-made, occur where they do in the ocean. Like other national initiatives involved in the International GEOTRACES Program, the goals of this U.S. Arctic expedition are to identify processes and quantify fluxes that control the distributions of key trace elements and isotopes (TEI) in the ocean, and to establish the sensitivity of these distributions to changing environmental conditions. Working at sea alongside a multi-institutional team of ocean trace element experts, investigators on this project will define regions of unusually high rates of TEI removal, anticipated to be located near basin margins and near the sea floor. By combining their measurements of naturally-occurring thorium and protactinium with TEI data collected by other participating investigators, they expect to be able to translate these rates into information that can be applied to other TEIs. Like most other participating investigators, this group will include graduate students as part of the research team and will participate in a variety of public educational outreach activities for Alaskan communities.This study will undertake measurements of the dissolved and particulate concentrations of 230Th and 231Pa, two isotopes designated as key or critical to the success of the GEOTRACES program. Additionally the team will measure dissolved and particulate 232Th concentrations and analyze a limited number of aerosol samples, aerosol leachates, sea ice, melt pond water and surface sediments for these radionuclides. The work plan will be broken down into five tasks geared to: (1) determine the rates of boundary scavenging of 231Pa and 230Th associated with the particle-rich waters near the southern margin of the Canada Basin; (2) determine the rates of bottom scavenging of 231Pa and 230Th associated with nepheloid layers that are prevalent in the Arctic Ocean; (3) assess the contribution to scavenging in the Canada basin by MnO2-coated particles, formed during early diagenesis in organic-rich sediments surrounding the Arctic Ocean; (4) determine the rate of supply of lithogenic 232Th from margin sediments using information derived from 230Th; and (5) determine the rate of supply of lithogenic 232Th from sea ice, including the aerosols and ice-rafted sediments that they transport, by the combined study of 232Th and 230Th. The proposed work fulfills core scientific objectives defined in the U.S. GEOTRACES Arctic Implementation Plan.

为了支持2015年美国北极探险队，该项目将重点关注北极海洋自然出现的放射性同位素的命运和分布。 这些信息对于理解为什么其他化学物质（无论是天然和人为）在海洋中所做的位置很有用。像国际地理计划计划中涉及的其他国家倡议一样，这项美国北极探险的目标是确定过程并量化控制海洋中关键的微量元素和同位素（TEI）分布的通量，并确定这些分布对不断变化的环境条件的敏感性。 该项目的调查人员与海洋微量元素专家的多机构团队一起在海上工作，将定义出异常高的TEI拆除率的地区，TEI拆除率异常，预计将位于盆地边缘附近和海底附近。 通过将其对自然折叠和Protactinium的测量与其他参与研究人员收集的TEI数据相结合，他们希望能够将这些速率转化为可以应用于其他TEI的信息。像大多数其他参与研究人员一样，该小组将包括研究生作为研究团队的一部分，并将参加各种为阿拉斯加社区的公共教育外展活动。这项研究将对第230和231PA的溶解和颗粒物浓度进行测量，两个同位素指定为对地理位置的成功或关键的同位素。此外，该团队将测量溶解和颗粒物232浓度，并分析这些放射性核素的数量有限的气溶胶样品，气溶胶渗滤液，海冰，融化的池塘水和表面沉积物。 工作计划将分为五个任务：（1）确定与加拿大盆地南部边缘附近粒子富含水域相关的231Pa和第230次边界清除的速率； （2）确定与在北极海洋中普遍存在的231Pa和第230层的底部清除率； （3）评估MNO2涂层的颗粒在加拿大盆地清除的贡献，该颗粒在北极海洋周围的有机丰富的沉积物中形成了早期成岩作用； （4）使用从第230位获得的信息确定岩性232的供应速率； （5）通过第232和230号研究的合并研究，确定海冰岩性232的供应速率，包括它们运输的气溶胶和冰羊皮的沉积物。 拟议的工作实现了美国北极实施计划中定义的核心科学目标。