Development of numerical simulation models for vertical solute transport in unsaturated soils and unconsolidated sediments

The theory and the numerical simulation of the vertical movement of water and solute in the unsaturated soil in the field are discussed. Firstly, a simulation model is described with which the vertical movement of water can be calculated, taking into account the uptake of water by roots. A newly developed method of calculation permits time-depth curves of water movement to be plotted and the residence time of water in the unsaturated soil to be determined. Next, the transport of solute under steady-state and transient water flow conditions is dealt with; it is simulated using finite difference models. The influence of adsorption processes and uptake of nutrients by roots on the movement of solute is considered and their simulation using numerical models is described. (orig.)