Collaborative Research: GEOTRACES Atlantic Section: Trace Element Sources and Sinks Elucidated by Short-Lived Radium and Thorium Isotopes

合作研究：GEOTRACES 大西洋部分：短命镭和钍同位素阐明的微量元素源和汇

• 批准号: 0925158
• 负责人: Matthew Charette
• 金额: $ 72.71万
• 依托单位: Woods Hole Oceanographic Institution
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2010
• 资助国家: 美国
• 起止时间: 2010-01-01 至 2012-12-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=0925158&HistoricalAwards=false
• 关键词: Collaborative; Research; GEOTRACES; Atlantic; Section

In this project, researchers at the Woods Hole Oceanographic Institution and the University of South Carolina will measure a suite of uranium/thorium series radionuclides on the first U.S.GEOTRACES cruise in the North Atlantic. The goal of GEOTRACES is to identify processes and quantify fluxes that control the distribution of trace elements and isotopes (TEIs) in the ocean, and to establish the sensitivity of these distributions to changing environmental conditions. Thorium and radium radioisotopes are well suited to study the sources and sinks of TEIs on time and space scales that are required to interpret lateral and vertical TEI distributions in the NOrth Atlantic basin. Accordingly, this project will employ the radium ?quartet? (224Ra, 223Ra, 228Ra and 226Ra) to quantify horizontal and vertical transport of dissolved TEIs, as well as the shorter lived thorium isotopes, 234Th and 228Th, used to quantify particle scavenging, vertical fluxes and remineralization rates of bioactive and/or particle reactive TEIs. A wide range of processes will be encountered along the proposed GEOTRACES N. Atlantic leg, and the short-lived U-Th series isotopes proposed herein will play a key role in the interpretation of observed TEI distributions. The utility of the Th and Ra tracers can be used to address two main key processes: boundary inputs of TEIs and TEI particle cycling including scavenging, vertical export and remineralization. To this end, the sampling plan includes: (1) detailed underway sampling of short-lived Ra isotopes (224Ra, 223Ra) at the western and eastern margins to quantify terrestrial inputs and off-shelf TEI transport; (2) upper ocean (0-1000 m) 234Th and 228Th profiling to capture export and remineralization patterns, (3) full water column 228Ra and 226Ra profiles to derive (a) submarine groundwater discharge, (b) midwater transport of TEIs from shelf/slope-basin interactions and (c) diapycnal mixing rates across the thermocline and benthic boundary layer, and (4) near bottom sampling to ascertain TEI sources and sinks associated with abyssal plain sediments and hydrothermal systems. Broader Impacts: The PIs have actively involved undergraduate and high school students in their prior NSF-funded projects, and this activity will continue in this project through the participation of an undergraduate intern. The anticipated timing of the GEOTRACES line is ideal for the student?s participation in the cruise as well as for several weeks back in the laboratory analyzing samples.

在该项目中，伍兹霍尔海洋研究所和南卡罗来纳大学的研究人员将在北大西洋的首次 U.S.GEOTRACES 巡航中测量一套铀/钍系列放射性核素。 GEOTRACES 的目标是识别控制海洋中微量元素和同位素 (TEI) 分布的过程和量化通量，并确定这些分布对不断变化的环境条件的敏感性。 钍和镭放射性同位素非常适合在时间和空间尺度上研究 TEI 的源和汇，这需要解释北大西洋盆地的横向和垂直 TEI 分布。 因此，该项目将采用镭“四重奏”。 （224Ra、223Ra、228Ra 和 226Ra）用于量化溶解 TEI 的水平和垂直传输，以及较短寿命的钍同位素 234Th 和 228Th，用于量化生物活性和/或颗粒反应性的颗粒清除、垂直通量和再矿化率TEI。沿着拟议的 GEOTRACES 北大西洋航线将会遇到各种各样的过程，本文提出的短寿命 U-Th 系列同位素将在解释观测到的 TEI 分布中发挥关键作用。 Th 和 Ra 示踪剂的实用性可用于解决两个主要关键过程：TEI 的边界输入和 TEI 粒子循环，包括清除、垂直输出和再矿化。为此，采样计划包括： (1) 在西部和东部边缘对短寿命 Ra 同位素（224Ra、223Ra）进行详细采样，以量化陆地输入和现成 TEI 传输； (2) 上层海洋 (0-1000 m) 234Th 和 228Th 剖面，以捕获输出和再矿化模式，(3) 全水柱 228Ra 和 226Ra 剖面，以得出 (a) 海底地下水排放，(b) 来自陆架的 TEI 的中水输送/坡盆相互作用和（c）跨温跃层和底栖边界层的二重混合率，以及（4）近底部采样确定与深海平原沉积物和热液系统相关的 TEI 源和汇。更广泛的影响：PI 积极让本科生和高中生参与其之前的 NSF 资助项目，并且该活动将通过本科生实习生的参与在本项目中继续进行。 GEOTRACES 线的预期时间非常适合学生参与巡游以及返回实验室分析样本的几周时间。