EAR-PF Subsurface Nitrous Oxide Emissions Along River Corridors: Analysis Across Spatial and Temporal Scales

科里·d·华莱士博士获得了美国国家科学基金会EAR博士后奖学金，将在辛辛那提大学工作，研究农业实践和降水模式的变化如何影响河流沿岸氧化亚氮的产生。一些证据表明，溪流附近农业活动产生的肥料可能会导致温室气体释放到大气中，这一过程随着人类对食物和能源需求的增加而加速。地表水和地下水沿着河流混合，将这种氮输送到河床和河岸，在那里它刺激了氮气的形成。释放量可能受到降雨量、土壤特性和土地使用类型的影响。通过实验、实地工作和建模活动，这项工作将研究河流如何促使温室气体释放到大气中，以及这种排放在未来可能如何变化。这项工作的结果将促进对温室气体如何释放到大气中的认识，并将有助于制定减少这些排放的管理战略。该博士后还将主持一门关于气候变化和农业对环境影响的实地和课堂课程，以加强研究生和本科生的教育。作为一个氧化还原过程，地下氮循环的程度和强度随养分有效性和地下水流动模式的变化而变化。因此，随后产生的一氧化二氮在空间和时间尺度上是高度可变的。本研究的工作假设包括：(a)在类似的地球化学环境中，相对于均匀的岩性，沉积物非均质性增加了地下氧化亚氮通量；(b)与气候变化相关的降水模式变化增加了河流走廊沿线的氧化亚氮通量，形成了一个正反馈循环，进一步刺激了气候变化。该博士后将利用辛辛那提大学的CV Theis地下水观测站，以高空间和时间分辨率评估大迈阿密河附近的河岸含水层，并阐明地下氮循环对氧化亚氮产量的水文和地球化学控制。这些实地测量将为数值模型的发展提供信息，而数值模型的发展又将提供关于沉积物非均质性和其他因素对氧化亚氮产生的影响的信息。流域尺度效应将通过同时使用模拟的未来气候数据和预估的土地利用变化来评估河流走廊沿线的一氧化二氮通量来评估。该奖项反映了美国国家科学基金会的法定使命，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。

Dr. Corey D. Wallace has been granted an NSF EAR Postdoctoral Fellowship to work at the University of Cincinnati to examine how agricultural practices and changes in precipitation patterns affect nitrous oxide production along rivers. Some evidence suggests that fertilizers from agricultural activities near streams could contribute to the release of greenhouse gases to the atmosphere, a process that has accelerated as human food and energy demands have increased. Surface water and groundwater mixing along rivers delivers this nitrogen to river beds and banks, where it stimulates the formation of nitrogen gases. The release may be influenced by the amount of rainfall, the characteristics of the soil, and type of land use. Through experimental, field work, and modeling activities, this work will study how streams contribute to the release of greenhouse gases into the atmosphere and how such emissions might change in the future. Results from this work will advance knowledge on how greenhouse gases are released to the atmosphere and will contribute to the development of management strategies to reduce these emissions. The postdoctoral fellow will also enhance graduate and undergraduate education by hosting a field and classroom-based course on the environmental effects of climate change and agriculture.As a redox process, the extent and magnitude of subsurface nitrogen cycling changes with nutrient availability and groundwater flow patterns. Subsequent nitrous oxide production is thus highly variable across spatial and temporal scales. The working hypotheses of this study include: (a) sediment heterogeneity increases subsurface nitrous oxide flux relative to a homogenous lithology in an otherwise analogous geochemical environment, and (b) climate change related shifts in precipitation patterns increase nitrous oxide flux along river corridors, creating a positive feedback loop that further stimulates climate change. The postdoctoral fellow will utilize the CV Theis Groundwater Observatory at the University of Cincinnati to evaluate the riparian aquifer adjacent to the Great Miami River at high spatial and temporal resolution and elucidate the hydrologic and geochemical controls on nitrous oxide yield from subsurface nitrogen cycling. These field measurements will inform numerical model development, which in turn will provide information on the influence of sediment heterogeneity and other factors on nitrous oxide production. Watershed-scale effects will be assessed by concomitantly using simulated future climate data and projected land use change to estimate nitrous oxide flux along river corridors.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.