GEOTRACES Pacific section: Dissolved Fe, Cd, and Zn isotopes

GEOTRACES 太平洋部分：溶解的铁、镉和锌同位素

• 批准号: 1235150
• 负责人: Seth John
• 金额: $ 39.4万
• 依托单位: University South Carolina Research Foundation
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2012
• 资助国家: 美国
• 起止时间: 2012-09-01 至 2016-09-30
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1235150&HistoricalAwards=false
• 关键词: GEOTRACES; Pacific; section; Dissolved; Fe

Iron (Fe) and other trace metals have a profound impact on marine biogeochemistry. In about 20 to 50% of the world's oceans, primary productivity is limited because phytoplankton cannot obtain enough Fe to satisfy their physiological needs. Small changes in seawater Fe concentrations can therefore have an immense impact on the growth of phytoplankton, affecting the productivity of ecosystems and the sequestration of carbon in both the modern and ancient oceans. Other trace metals such as zinc (Zn), and cadmium (Cd) can be important nutrients for phytoplankton in their own right, and can be used as chemical tracers to explore processes such as nutrient supply and remineralization, ocean circulation, and earth's climate history. In this project, a research team at the University of South Carolina at Columbia will measure dissolved Fe stable isotopes in samples collected on the US GEOTRACES Eastern Tropical South Pacific (ETSP) transect. GEOTRACES is an international effort to map the distribution of biogeochemically important metals in the oceans. Trace metal isotope ratios add a crucial dimension to the GEOTRACES mission because the information contained in isotope signals is often very different from what can be learned by concentration distributions alone. Along with Fe isotopes, they will simultaneously generate Cd and Zn isotope ratio data in some of the same samples. These data will be used to distinguish between competing hypotheses about trace-metal and nutrient distribution in the oceans, with a focus on two specific questions: (1) What are the sources of bioavailable Fe to the oceans? Dust deposition, flux of reduced Fe from continental margin sediments, and hydrothermal vents have all been hypothesized as major contributors to the global dissolved Fe pool. The team will measure the stable Fe isotopic signatures of these fluxes at 'end-member' locations including surface waters (dust), the Peru oxygen minimum zone (reducing sediments), and the East Pacific Rise (hydrothermal vents). Basin-scale Fe isotopic distribution will then be studied in order to quantify how these various sources contribute to the global pool of biologically utilized Fe. (2) What processes cycle Fe within the ocean? As Fe is cycled by various biological and inorganic processes, the team will track Fe isotopic composition in order to better understand how source-Fe isotopic signatures are modified through internal cycling, how iron is transferred between different pools such as dissolved and particulate phases, and the processes that allow dissolved and particulate Fe to become bioavailable. Broader Impacts: This study will contribute to education through the training of a postdoctoral associate, a graduate student, and the involvement of undergraduate students in several aspects of this work. Additionally, this project addresses questions of broad oceanographic and scientific importance, potentially transforming our understanding of the role that trace-metals and other nutrients play in supporting life in the oceans and affecting global climate change

铁等微量金属元素对海洋地球化学有着深远的影响。在世界上约20%至50%的海洋中，初级生产力受到限制，因为浮游植物无法获得足够的铁来满足其生理需求。因此，海水Fe浓度的微小变化可能对浮游植物的生长产生巨大影响，影响生态系统的生产力和现代和古代海洋中碳的封存。其他微量金属，如锌（Zn）和镉（Cd），本身就是浮游植物的重要营养物质，可用作化学示踪剂，以探索营养供应和矿化、海洋环流和地球气候历史等过程。在这个项目中，哥伦比亚的南卡罗来纳州大学的一个研究小组将测量在美国GEOTRACES东热带南太平洋（ETSP）断面上收集的样品中溶解的铁稳定同位素。GEOTRACES是一项国际努力，旨在绘制海洋中地球化学重要金属的分布图。痕量金属同位素比为GEOTRACES使命增加了一个重要方面，因为同位素信号中所含的信息往往与仅通过浓度分布所能了解的信息大不相同。 沿着Fe同位素，它们将同时生成某些相同样品中的Cd和Zn同位素比值数据。这些数据将被用来区分竞争的假设之间的微量金属和营养分布在海洋中，重点是两个具体的问题：（1）什么是生物可利用的铁的海洋来源？尘埃沉积、大陆边缘沉积物还原铁通量和热液喷口都被假设为全球溶解铁库的主要贡献者。该小组将测量这些通量在“端元”位置的稳定铁同位素特征，包括地表沃茨（灰尘），秘鲁氧气最小区（减少沉积物）和东太平洋隆起（热液喷口）。流域规模的铁同位素分布，然后将进行研究，以量化这些不同的来源如何有助于全球池的生物利用铁。(2)海洋中铁的循环过程是什么？由于Fe通过各种生物和无机过程循环，该团队将跟踪Fe同位素组成，以便更好地了解源Fe同位素特征如何通过内部循环进行修改，铁如何在不同的池（如溶解和颗粒相）之间转移，以及允许溶解和颗粒Fe成为生物可利用的过程。更广泛的影响：这项研究将有助于教育，通过培训博士后助理，研究生，本科生参与这项工作的几个方面。此外，该项目还涉及具有广泛的海洋学和科学重要性的问题，可能会改变我们对微量金属和其他营养物质在支持海洋生命和影响全球气候变化方面所起作用的理解