Stable Isotopic Constraints on Nitrogen Transformations in Low and High Temperature Hydrothermal Fluids

低温和高温热液中氮转化的稳定同位素约束

• 批准号: 1537372
• 负责人: Scott Wankel
• 金额: $ 37.97万
• 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: 2015
• 资助国家: 美国
• 起止时间: 2015-09-01 至 2018-08-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1537372&HistoricalAwards=false
• 关键词: Stable; Isotopic; Constraints; Nitrogen; Transformations

Part 1This project will address deficiencies in our understanding of Nitrogen transformations under hydrothermal conditions with implications for the fate of bioavailable Nitrogen in the modern subsurface biosphere and of reduced Nitrogen on pre-biotic Earth. Through the PIs the project will advance the utility of Nitrogen isotopic composition in active submarine hydrothermal systems. Three hypotheses will be tested concerning: the reaction temperature and redox state of hydrothermal reaction zones; NH4+ in high temperature vent fluids; and NH4+ and NO3- in low-temperature vent fluids. To address these hypotheses, the PI's plan combined experimental and observational approaches. Well-constrained laboratory experiments will be conducted to determine operative reaction pathways and associated N isotopic fraction during redox dependent reactions involving dissolved N species under hydrothermal conditions. In addition, measurements will be made in high and low temperature hydrothermal vent fluids from existing samples spanning a range of hydrothermal environments to constrain abiotic and microbially mediated processes that influence the abundance of aqueous N species in submarine hot springs. The broader impacts consist of educational opportunities for students at various levels. Part 2This project aims to address existing deficiencies in our understanding of nitrogen transformations under hydrothermal conditions with implications for the fate of bioavailable nitrogen in the modern subsurface biosphere and of reduced nitrogen on pre-biotic Earth. Through the examination of the controls on reaction pathways, rates, and associated stable isotope systematics, this project will advance the utility of nitrogen isotopic composition in active submarine hydrothermal systems, and help to constrain geologic records of nitrogen isotopic composition. This research is guided by the hypotheses that 1) reaction temperature and redox state of hydrothermal reaction zones regulate the geochemical conversion of nitrate (NO3-) and possibly dinitrogen (N2) to ammonium, that 2) the stable nitrogen isotopic composition of NH4+ in high temperature vent fluids will record the relative roles of these reaction processes and that 3) variations in the abundance and isotopic composition of NH4+ and NO3- in low-temperature vent fluids in concert with their corresponding high temperature endmember source fluids can be used to constrain the nature and extent of subsurface biological processes. To address these hypotheses, the PI?s plan combined experimental and observational approaches. Well-constrained laboratory experiments will be conducted to determine operative reaction pathways and associated N isotopic fraction during redox dependent reactions involving dissolved N species under hydrothermal conditions. In addition, the abundance and N (and O) isotopic composition o NH4+ (and NO3-) will be measured from high and low temperature hydrothermal vent fluids from a rich archive of samples spanning a range of hydrothermal environments to constrain abiotic and microbially mediated processes that influence the abundance of aqueous N species in submarine hot springs. The broader impacts consist of educational opportunities for students at various levels.

本项目将解决我们对热液条件下氮转化的理解不足之处，这将对现代地下生物圈中生物可利用氮的命运和生物诞生前地球上还原氮的命运产生影响。通过pi，该项目将推进氮同位素组成在活跃海底热液系统中的应用。本文将检验三个假设：热液反应带的反应温度和氧化还原状态；高温排气液中的NH4+；低温排气液中的NH4+和NO3-。为了解决这些假设，PI的计划结合了实验和观测方法。将进行约束良好的实验室实验，以确定在水热条件下涉及溶解N物种的氧化还原依赖反应中有效的反应途径和相关的N同位素分数。此外，将对现有样品的高温和低温热液喷口流体进行测量，这些样品跨越一系列热液环境，以限制影响海底温泉中水氮丰度的非生物和微生物介导的过程。更广泛的影响包括各级学生的教育机会。本项目旨在解决我们对热液条件下氮转化的现有认识的不足，这对现代地下生物圈中生物可利用氮的命运和生物诞生前地球上还原氮的命运具有重要意义。通过对反应途径、速率和相关稳定同位素系统控制的研究，本项目将促进氮同位素组成在活跃海底热液系统中的应用，并有助于限制氮同位素组成的地质记录。本研究基于以下假设：1)热液反应带的反应温度和氧化还原状态调节硝酸盐（NO3-）和二氮（N2）向铵态氮的地球化学转化；2)高温喷口流体中NH4+稳定的氮同位素组成将记录这些反应过程的相对作用；3)低温喷口流体中NH4+和NO3-丰度和同位素组成的变化及其对应的高温端元源流体可以用来约束地下生物过程的性质和程度。为了解决这些假设，PI？S计划结合实验和观测方法。将进行约束良好的实验室实验，以确定在水热条件下涉及溶解N物种的氧化还原依赖反应中有效的反应途径和相关的N同位素分数。此外，还将从一系列热液环境中丰富的样品档案中测量高温和低温热液喷口流体中NH4+（和NO3-）的丰度和N（和O）同位素组成，以约束影响海底温泉中水氮丰度的非生物和微生物介导的过程。更广泛的影响包括各级学生的教育机会。