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

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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.