Collaborative Research: Understanding the role of hyporheic processes on nitrous oxide emissions at the stream network scale

合作研究：实地证据证实，活性氮（Nr），主要是铵和硝酸盐的流处理，是一个潜在的温室气体一氧化二氮（N2O）的重要来源。河流排放量可能占全球人为N2O产量的10%，N2O每单位重量的变暖潜力是二氧化碳的310倍。在河流中，N2O的产生主要发生在河床沉积物中，反应性物种的质量迁移，即，溶解氧、Nr和有机碳通过潜流强烈影响反应速率、停留时间和随后的N2O排放。以往的研究表明，在潜流区（HZ）和河床形态水力学之间的强烈相互作用。该项目耦合一种新的拉格朗日建模方法的基础上的停留时间分布差异的通道到达类型和当地的潜流组件的流网络与季节性天气抽样在两个流域对比土地利用。加强对流域和网络规模控制有效的温室气体排放的理解将是社会相关的政策制定者解决地表沃茨氮浓度升高。研究成果将适用于土地利用管理、非点源污染和河流恢复项目。本研究的成果将为估算Nr在水系尺度上的命运提供一个模型，为HZ在水系尺度上的作用提供一个新的认识，并阐明水系结构和河流形态对HZ过程的影响。这项研究的结果可以扩展到研究其他溶质和病原体沿沿着的运输。随着遥感和地理信息系统工具的进步，这种方法的数据将更容易获得，从而在可获得最少实地调查数据的情况下可用于提供预测。更广泛的影响还包括对高中生的宣传，以及与麦考尔户外科学学校在气候变化背景下交流工作的工作。

Collaborative Research: Understanding the role of hyporheic processes on nitrous oxide emissions at the stream network scale Field evidence confirms that stream processing of reactive nitrogen (Nr), primarily ammonium and nitrate, is a potentially important source of the potent greenhouse gas nitrous oxide (N2O). Stream emissions may account for up to 10% of global anthropogenic N2O production and N2O has 310 times more warming potential per unit weight than carbon dioxide. In streams, the production of N2O occurs primarily in streambed sediments, and the mass transport of reactive species, i.e., dissolved oxygen, Nr, and organic carbon, via hyporheic flow strongly influences reaction rates, residence times, and subsequent N2O emissions. Previous research has shown a strong interaction between hydraulics in the hyporheic zone (HZ) and streambed morphology. The project couples a novel Lagrangian modeling approach based on residence time distributions differentiated for channel reach types and local hyporheic components of the stream network with seasonal synoptic sampling in two watersheds with contrasting land use. Improved understanding of watershed and network scale controls on potent greenhouse gas emissions will be societally-relevant to policy makers addressing elevated Nr concentrations in surface waters. Research results will be applicable to land use management, non-point source pollution, and river restoration projects. The products from this research will provide a model for estimating the fate of Nr at the stream network scale, offer a new understanding of the role of HZ at the stream network scale, and clarify the effect of stream network structure and stream morphology on HZ processes. Results from this research can be extended to study transport of other solutes and pathogens along streams. With the advance in remote sensing and GIS tools, data for this approach will be more readily available and thus applicable to provide predictions when minimal field survey data are available. The broader impacts also involve the outreach to high school students, and the work with the McCall Outdoor Science School in regards to communication of the work in a climate change context.