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转化的理解中的不足，并对现代地下生物圈中生物有效氮的命运和生物地球前的氮减少产生影响。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。将测试三个假设：热液反应区的反应温度和氧化还原状态;高温喷口流体中的NH 4 +;低温喷口流体中的NH 4+和NO 3-。为了解决这些假设，PI的计划结合了实验和观察方法。约束良好的实验室实验将进行，以确定操作的反应途径和相关的氮同位素馏分在氧化还原依赖的反应，涉及溶解的N物种在水热条件下。此外，还将对来自各种热液环境的现有样本的高低温热液喷口流体进行测量，以限制影响海底温泉中含水氮物种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。第2部分本项目旨在解决现有的缺陷，我们的理解氮转化热液条件下的影响，在现代地下生物圈的生物有效氮的命运和减少氮的前生物地球。通过对反应途径、速率和相关稳定同位素系统学的控制的研究，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，并有助于限制氮同位素组成的地质记录。本研究的指导假设是：1）热液反应区的反应温度和氧化还原状态调节硝酸盐（NO3-）和可能的二氮（N2）向铵的地球化学转化，2）NH4+的稳定氮同位素组成记录了这些反应过程的相对作用;低温喷口流体中的NH4+和NO3-的丰度和同位素组成的变化与它们相应的高温端元源流体一致，可用于限制地下生物过程的性质和程度。为了解决这些假设，PI？他的计划结合了实验和观察的方法。约束良好的实验室实验将进行，以确定操作的反应途径和相关的氮同位素馏分在氧化还原依赖的反应，涉及溶解的N物种在水热条件下。此外，丰度和N（和O）同位素组成的NH 4+（和NO3-）将从高低温热液喷口流体测量从一个丰富的档案的样品跨越一系列热液环境，以限制非生物和微生物介导的过程，影响丰富的水性N物种在海底温泉。更广泛的影响包括各级学生的教育机会。

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.