Corey is a groundwater and geochemical scientist with ten years of research experience. His practice focuses on groundwater-surface water interactions, physical hydrology, and groundwater flow and reactive transport modeling to assess groundwater quality and evaluate remediation strategies.
The paper entitled “Spatiotemporal dynamics of nitrous oxide emission hotspots in heterogeneous riparian sediments,” published in Water Resources Research, analyzes subsurface nitrogen transformation dynamics in response to varying hydrologic conditions. Corey’s coauthors were Mohamad Reza Soltanian, Daniele Tonina, Felipe P.J. de Barros, and Jeffrey McGarr. Water Resources Research publishes original research articles on hydrology, water resources, and the social sciences of water that provide a broad understanding of the role of water in the Earth system.
Abstract:
Nitrous oxide (N2O) is a potent ozone-depleting greenhouse gas produced by incomplete denitrification. Recent works on riverine N2O emissions focus on contributions from in-channel, benthic, and fluvial hyporheic environments under assumptions of steady-state conditions and homogeneous sediment hydraulic conductivity (K). However, riparian floodplains are also a potentially important N2O source characterized by complex sediment heterogeneity and dynamic surface and groundwater interactions. We use numerical flow and reactive transport models to investigate the influence of complex sedimentary architecture and high-flow events (e.g., storms) on N2O production. We interpret the correlation between flow and solute fields with the flow topological Okubo-Weiss metric (OW) and the scalar dissipation rate weighted by soil organic matter fraction and soil saturation. We model a heterogeneous riparian floodplain based on field observations from the Theis Environmental Monitoring and Modeling Site, Ohio, USA. N2O production is greatest within intermediate-K sediments (e.g., sands) where denitrification rates are highest, and emissions increase by more than an order of magnitude during storms. Sensitivity analysis reveals that the denitrification rate is most influential for N2O flux, accounting for nearly 46% of the variance in production rates. Denitrification rates adapt to spatial changes in the flow topology (measured by OW) related to sediment heterogeneity and are strongly influenced by subsurface mixing dynamics. Mixing is greatest in shear strain-dominated regions, while vorticity promotes OM dissolution and prolongs residence times. Accurate lithologic representation is imperative for characterizing subsurface N2O production dynamics, especially given growing concern regarding climate change driven hydrologic changes within watersheds worldwide.
More Information
Learn more about the article: https://doi.org/10.1029/2021WR030496
For consultation regarding groundwater-surface water interactions, groundwater modeling, and reactive solute transport, contact Corey Wallace at CWallace@Geosyntec.com
Learn more about Corey: https://www.linkedin.com/in/corey-d-wallace/
