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Numerical Modeling of the Effect of Immobile Water Content on Nitrate Transport in an Unsaturated Porous System
Abstract
Nitrate originating from wastewater applied onagricultural sites, is one of the most common pollutants ingroundwater. It causes a prime risk for human health during theconsumption of nitrate contaminated groundwater. In this presentstudy, a numerical model is developed to understand and forecast thefate and transport of nitrogen species in an unsaturated porous media.In addition, the concept of mobile-immobile water content in anunsaturated zone is incorporated in the one-dimensional numericalmodel for nitrogen species transport. The mass transfer of contaminantin mobile-immobile zone is effectively carried out to predict theconcentration of nitrogen species in unsaturated zone. The numericalresults of water flow and contaminant transport model in unsaturatedzone developed for this study have been validated with the availableanalytical/numerical solution. Results indicate that the immobile watercontent plays a predominant role in nitrogen species transport in anunsaturated zone. The simulation results also suggest that nitrogenspecies concentration travels to a low depth in mobile water zonecompared to the immobile water content due to the exchange ofcontaminant mass from mobile phase to immobile phase. Moreover,the numerical results suggest that the mass transfer rate is aninfluencing parameter in the movement of ammonium nitrogen andnitrate nitrogen concentration in an unsaturated zone.
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References
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