Characterization of Nitrogen Hot Spots and Hot Moments in a Flood Plain Using Numerical Modeling

Environmental hot spots and hot moments (HSHMs) denote small locations and short time periods that exert disproportionate influences over the ecosystem dynamics. Flood plains is a crucial part in contributing to the cycling of nitrogen. This research applied the concept of HSHMs for characterizing the transport and distribution of nitrogen at a floodplain site in Rifle, CO. Studies indicate that accurate characterization of hydrologic flow paths and biogeochemical processes in the subsurface are essential for producing reliable nitrogen dynamics in the floodplain. This study examined the chemical heterogeneity and physical heterogeneity for characterizing and quantifying nitrogen dynamics using 2-D flow and reactive transport model. This study investigated nitrogen HSHMs features through sensitivity analysis. The nitrogen HSHMs features are including the seasonality and extreme cases for temperature fluctuations and water table fluctuations. Furthermore, we studied the influences of spatially variable physical properties (e.g. hydraulic conductivity and porosity) to the nitrogen dynamics. This study aims at exploring the applicability of HSHMs in subsurface hydrology, identifying a benchmark for the characterization of nitrogen dynamics in the floodplain environment.