EAR-PF: Quantifying methane reactivity and turnover in the subterranean estuary: combined in-situ and ex-situ isotope tracer approaches

在陆地和海洋的界面处，地下河口（STE）充当地下过渡区。STE可以支持各种生物地球化学反应，影响营养物质和碳的浓度和运输。在沿海地下观测到高浓度的甲烷（CH 4），这是一种重要的温室气体，也是全球碳循环的主要参与者。然而，这种CH 4池在STE内转化和运输的方式仍然不受约束。这项研究将提供一个新的理解甲烷是如何在地下循环，特别是其周转时间和转换控制浓度和命运，就在释放到地表沃茨。这些研究成果代表了基本的制约因素，这些制约因素对于确定来自地下的CH 4通量以及STE在全球碳循环中的作用至关重要。Stephanie Wilson博士将在东海岸沿着多个研究小组先前工作的基础上，进一步科学地了解CH 4循环和地下与上覆水或大气之间的交换。这项研究的结果将直接适用于正在进行的研究和建模工作，提供有关甲烷的基本信息，为计算地下水的通量和排放量提供信息，其影响超出了地下水水文学和地球化学领域。此外，该项目旨在优化其调查结果的覆盖面并开发人力资本。研究结果将在会议、部门研讨会上传播，并在科学期刊上发表。威尔逊博士将把本科生纳入实地和实验室研究工作，目标是创造一个包容的环境，促进个人成长和科学学习。研究结果将通过几种途径向公众提供，旨在通过各种参与活动吸引K-12学生，教育工作者，当地社区和更广泛的公众。地下河口（STE）是地下的重要过渡区，承载着各种地球化学反应。它们是受流域和潮汐驱动力影响的动态系统。在STE中，微地球化学反应控制地下营养物和碳的形态和浓度，因此，它们决定了这些分析物释放到上覆水和/或大气中时的命运。有越来越多的文献报道，高浓度的甲烷（CH 4）在地下沿着沿海边缘，然而，该池的转换和运输的机制仍然未知。因此，有一个有限的了解如何地下甲烷池交换与上覆水和/或大气。STE可以作为一个被动界面，使CH 4在含水层内产生的移动通过STE保守，或CH 4库存可能会修改通过消费或生产STE内的时间尺度快于净运输。缺乏上下文和定义的限制控制的STE CH 4池代表了一个知识差距至关重要的确定通量的CH 4从地下和STE在全球碳循环中发挥的作用。该项目包括采用一种三管齐下的方法，将原位和非原位稳定同位素标记示踪实验与地下地球化学梯度的表征相结合，研究甲烷在STE中的转化和迁移。这项工作涉及利率和机制。将在美国东海岸沿着的几个STE中进行示踪剂实验，这些STE被解析为两种主要的沿海STE类型，湿地和桑迪，并跨越水文强迫谱。从这项研究的结果将提供一个新的理解甲烷是如何在地下循环，特别是其周转时间和转换控制浓度和命运，就在释放到地表沃茨。具体而言，这项工作将提供关于CH 4总量周转率、转化率和运输率的信息。这些产品代表了基本的限制，这是至关重要的，以确定流量的甲烷从地下和STE在全球碳循环中的作用。这一新的信息将直接适用于正在进行的确定过渡区在温室气体动力学和全球气候变化中的作用的研究。研究产品将提供基本信息，其影响将超出地下水水文学和地球化学领域。研究结果将为STE所设想的CH 4大气通量建模提供基本约束，该项目旨在优化其研究成果的覆盖范围并开发人力资本。该奖项反映了NSF的法定使命，并通过使用基金会的知识价值和更广泛的影响审查标准进行评估，被认为值得支持。

At the interface of land and sea, subterranean estuaries (STEs) serve as subsurface transition zones. STEs can support a variety of biogeochemical reactions that influence concentrations and transport of nutrients and carbon. High concentrations of methane (CH4), an important greenhouse gas and major player in the global carbon cycle, has been observed in the coastal subsurface. However, the way that this CH4 pool is transformed and transported within STEs remains unconstrained. This study will provide a novel understanding of how CH4 is cycled in the subsurface, specifically its turnover time and the transformations controlling concentration and fate, just prior to release to surface waters. These research products represent fundamental constraints, which are critical to determining fluxes of CH4 from the subsurface and the role of STEs in the global carbon cycle. Dr. Stephanie Wilson will build upon previous work conducted by multiple research groups along the east coast, to further scientific understanding of CH4 cycling and exchanges between the subsurface and the overlying water or atmosphere. The results of this study will be directly applicable to ongoing research and modeling efforts, providing fundamental information about CH4 to inform calculations of fluxes and emissions from the subsurface, with implications beyond the fields of groundwater hydrology and geochemistry. Moreover, the project is designed to optimize the reach of its findings and develop human capital. Results will be disseminated at conferences, departmental seminars, and published in scientific journals. Dr. Wilson will incorporate undergraduate students in both field and lab research efforts with the goal of creating an inclusive environment that promotes personal growth and scientific learning. Research findings will be made available to the public via several avenues designed to engage K-12 students, educators, the local community, and the larger public via a variety of engagement activities.Subterranean estuaries (STEs) are important transition zones within the subsurface that host a variety of biogeochemical reactions. They are dynamic systems influenced by both watershed and tidal drivers. Within the STE, biogeochemical reactions control the speciation and concentration of subsurface nutrients and carbon, therefore, they determine the fate of these analytes when they are released to the overlying water and/or the atmosphere. There is a growing body of literature reporting high concentrations of methane (CH4) in the subsurface along coastal margins; however, the mechanisms of transformation and transport of this pool remain unknown. There is, therefore, a limited understanding of how this subsurface CH4 pool exchanges with the overlying water and/or atmosphere. The STE may act as a passive interface whereby CH4 generated within the aquifer moves through the STE conservatively, or CH4 inventories may be modified via consumption or production within the STE on timescales faster than net transport. The lack of context and defined constraints controlling the STE CH4 pool represents a knowledge gap essential to determining fluxes of CH4 from the subsurface and the role STEs play in the global carbon cycle. The project includes examination of the transformations and transport of CH4 in STEs using a three-pronged approach that combines in situ and ex situ stable isotope labeled tracer experiments with the characterization of subsurface geochemical gradients. The work addresses rates and mechanisms. Tracer experiments will be conducted in several STEs along the east coast of the US parsed into the two dominant coastal STE types, wetland and sandy, and spanning a spectrum of hydrologic forcings. Results from this study will provide a novel understanding of how CH4 is cycled in the subsurface, specifically its turnover time and the transformations controlling concentration and fate, just prior to release to surface waters. Specifically, this work will provide information regarding the CH4 pool rate of turnover, transformation, and transport. These products represent fundamental constraints, which are critical to determining fluxes of CH4 from the subsurface and the role of STEs in the global carbon cycle. This novel information will be directly applicable to ongoing research determining the role of transition zones in greenhouse gas dynamics and global climate change. Research products will provide fundamental information, which will reach beyond the fields of groundwater hydrology and geochemistry. Results will provide fundamental constraints on modeling atmospheric fluxes of CH4 meditated by the STE and the project is designed to optimize the reach of its findings and develop human capital.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.