ABSTRACT
A mathematical model, named SIMASS, was developed to simulate the one-dimensional water and solute transport in the soil profile under unsteady flow conditions. Both the water and solute transport equations were numerically solved by the finite difference method. Among other characteristics, the model allows the simulation of soil moisture and solute distribution in the soil profile; the utilization of the boundary conditions of the constant potential and the steady flux types; and the use of two functions for estimating the hydraulic conductivity in the unsaturated soil. The SIMASS model was compared to the CXTFIT model for soil-water saturated conditions. Simulations of nitrate breakthrough curves in leaching columns and nitrate distribution profiles from soil columns were obtained in order to verify the SIMASS performance. The SIMASS sensibility to Δz and Δt was analyzed. The results showed an adequate performance of SIMASS in simulating the breakthrough curves and nitrate concentration distribution profiles when compared to CXTFIT and experimental data. The SIMASS model is more sensible to Δz in simulating the breakthrough curves in leaching columns and Δt to simulating the nitrate concentration distribution profiles.
Key words:
modeling; soil water content; solute transport; unsteady flow