PEARL is a one-dimensional numerical model of pesticide behaviour in the soil-plant system. It simulates water flow in soil and considers changes in groundwater levels due to rainfall. Soil evaporation and plant transpiration are calculated. For the FOCUS scenarios, crop growth is simulated with a simple growth model that assumes a fixed length of the growing season. In this growth model, both the leaf area index and the rooting depth are a function of the development stage of the crop. Heat flow in soil is described, too. The thermal properties are a function of porosity and water content and are therefore a function of time and soil depth. PEARL is based on: (i) the convection/dispersion equation including diffusion in the gas phase with a temperature dependent Henry coefficient, (ii) a two-site Freundlich sorption model (one equilibrium site and one kinetic site), (iii) a transformation rate that depends on water content, temperature and depth in soil, (iv) a passive plant uptake rate. The model includes formation and behaviour of transformation products and describes also lateral pesticide discharge to drains (but drainage is switched off for the FOCUS scenarios). PEARL does not simulate preferential flow. Volatilisation from the soil surface is calculated assuming a laminar air layer at the soil surface. PEARL uses an explicit finite difference scheme that excludes numerical dispersion (the dispersion length was set to 5 cm) (Leistra and Boesten, 2010; Leistra and Van Den Berg, 2007; Tiktak et al., 2013).


Go To Top