EVALUATION OF A HYDRUS-3D MODEL FOR PHOSPHORUS TRANSPORT IN SOIL COLUMNYaser Hoseini1 and Alireza Pilpayeh
In order to put forward practical and effective methods to prevent contamination of groundwater, rigorous understanding of the transport mechanisms of contaminants in soils and aquifers is necessary. In the past two decades, models were developed to characterize the movement of inorganic solutes as well as organic contaminants in homogeneous soils. The ability of the HYDRUS -3D model was tested to describe phosphate (PO4) adsorption onto soil particles using soils collected from agricultural fields. The objectives of the present study were to understand phosphorus transport from soil columns at different densities of water flux and to compare computer simulation results using HYDRUS-3D and the physical model (column-experiment) data. Two densities of water flux (0/0085, 0/0045 m s-1) and P concentration rates (42 mmol cm-3) were used. The soil has a silty-clay-loam texture. The HYDRUS-3D model was calibrated and validated with results from re-packed column experiments. The simulated results were then compared with results obtained by the physical experiment model. The overall goodness-of-fit for the HYDRUS-3D model simulations was classified as well. The numerical model (HYDRUS-3D) with Langmuir adsorption constants shows that this model is suitable for predicting the amount of P adsorption in soil column. In conclusion, the HYDRUS- 3D model successfully simulated water flow, but unrealistically described PO4 distribution in the soil profile. The difference between the model and experiments may be the result of preferential flow of water through the soil without sufficient time for reaction between the soil and the solute.
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