Simulation du lessivage des bromures par un modéle de transport en phases mobile-immobile

Integration of mobile-immobile water in the dispersion-advection equation (DAE) has resulted in a mobile-immobile transport equation (MITE) which takes into account the homogeneous preferential flow in weakly structured soils. A numerical model using the numerical method of lines (NML) coupled with the MITE with Richards' equation was developed. Results of the model were compared to those of a numerical model solving the DAE and to experimental data (concentration profiles and drained masses of bromide) collected over 195 days in three undisturbed pan lysimeters cultivated under potatoes. Two alternatives were considered for the immobile water content (θ_im) formulation. For the first one, θ_im was considered as a constant, whereas for the second one, a polynomial relationship of the second order was considered between θ_im and the total water content (θ). Use of the MITE improved the results of the simulation of bromide leaching compared to those obtained by the DAE. Between both alternatives, the second one results in smaller differences with observed data than the first one.