Different numerical and analytical models are presently available that provide the tools to predict pollutant and water transfer processes between the soil surface and the groundwater level. Among the existing models, the Hydrus-1D model has been used for years in the prediction of water and pollutants transfer in the unsaturated zone. The main purpose of this paper was to model the movement of the landfill leachate in the soil at the Aradkouh landfill and predict the changes in nitrogen and

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... sphorus concentration in the leachate at different depths. Two pilots were used in this study, one included the local soil and the other contained local soil with Vetiver grass (Chrysopogon zizanioides). After its initial purification, the resultant leachate entered the pilot and was collected after passing through the soil. Finally, the flow of the leachate movement as well as the nitrogen and phosphorus concentration changes in soil were modeled by using Hydrus-1D. The prediction model for the phosphate and nitrogen concentration changes at different depths showed that the best results were obtained in the surface charge of 0.12 m 3 /m 2 .week and by the pilot with the Vetiver grass. The results showed that the use of Vetiver grass in surface purification increased the efficiency of the purification.