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

在这个项目中，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第一次美国geotraces巡航上测量一系列铀/钍系列放射性核素。GEOTRACES的目标是确定控制海洋中微量元素和同位素（TEIs）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，这是解释北大西洋盆地TEI横向和垂直分布所必需的。因此，这个项目将采用镭四重奏。（224Ra, 223Ra， 228Ra和226Ra）用于量化溶解TEIs的水平和垂直输送，以及寿命较短的钍同位素234和228Th用于量化生物活性和/或颗粒反应性TEIs的颗粒清除、垂直通量和再矿化率。沿着提出的GEOTRACES N.大西洋分支将遇到广泛的过程，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示踪剂的使用可用于解决两个主要的关键过程：TEI的边界输入和TEI颗粒循环，包括清除，垂直出口和再矿化。为此，采样计划包括：(1)在东、西边缘详细采样短寿命Ra同位素（224Ra、223Ra），量化陆地输入和离架TEI输运；(2)上层海洋（0-1000米）234和228Th剖面，捕捉出口和再矿化模式；(3)全水柱228Ra和226Ra剖面，得出(a)海底地下水排放；(b)陆架/斜坡-盆地相互作用中TEI的中水输送；(c)跨温跃层和底栖边界层的底流混合速率；(4)近底采样，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在他们之前的nsf资助项目中积极地让本科生和高中生参与其中，并且该活动将通过本科生实习生的参与在该项目中继续进行。GEOTRACES线路的预期时间对学生来说是理想的？美国参加这次巡航，以及几周后在实验室分析样本。

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.