Models for Nitrates in the Subsurface Environment

This chapter aims to highlight a number of models and submodels for describing the transport and fate of nitrogen and nitrates in the subsurface environment. An initiating mechanism for nitrogen or nitrate movement toward the groundwater system involves leaching. A factor that obviously affects nitrate movement in the subsurface environment is the quantity of recharge water. The most comprehensive models for nitrates in the subsurface environment are those that address transport in both the unsaturated and saturated zones. The chapter aims to presents source characterization models, a plume model for a nitrogen point source, and management models useful for developing nitrate pollution prevention and control programs. Four important factors that were identified as affecting nitrate leaching loss and that were controllable included irrigation quantity, nitrogen source, nitrogen amount, and timing of nitrogen application. Soil processes can include infiltration, evapotranspiration, nitrogen transformations, nitrogen losses due to ion exchange, and nitrogen uptake by crops.