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

第1部分本项目将解决我们对热液条件下氮素转化的认识上的不足，这将对现代地下生物圈中生物可利用氮的命运和生物前地球上还原氮的命运产生影响。通过PIS，该项目将促进氮同位素组成在活跃的海底热液系统中的应用。将检验三种假设：水热反应区的反应温度和氧化还原状态；高温排气液中的NH4+；以及低温排气液中的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。将进行受限的实验室实验，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的操作反应路径和相关的N同位素分数。此外，将在一系列水热环境中对现有样品的高温和低温热液喷口流体进行测量，以限制影响海底温泉中含氮物种丰度的非生物和微生物中介过程。更广泛的影响包括为学生提供不同层次的教育机会。第2部分本项目旨在解决我们对热液条件下氮素转化的现有认识上的不足，这对现代地下生物圈中生物可利用氮和生物前地球上还原氮的去向有影响。通过对反应途径、速率和相关稳定同位素系统学控制的研究，该项目将促进氮同位素组成在活跃的海底热液系统中的应用，并有助于约束氮同位素组成的地质记录。本研究的指导思想是：1)热液反应带的反应温度和氧化还原状态调节硝酸盐(NO3-)和可能的氮素(N_2)向氨的地球化学转化；2)高温喷口流体中稳定的NH_4+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NH_4+和NO_3-的丰度和同位素组成的变化与其对应的高温端元流体相一致，可以用来限制地下生物过程的性质和程度。为了解决这些假设，皮？S计划结合了实验和观测方法。将进行受限的实验室实验，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的操作反应路径和相关的N同位素分数。此外，将从一系列热液环境的丰富样品档案中测量NH4+(和NO3-)的丰度和N(和O)同位素组成，以限制影响海底温泉水中N物种丰度的非生物和微生物中介过程。更广泛的影响包括为学生提供不同层次的教育机会。

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.