Performance testing and validation of PESTFADE

PESTFADE (PESTicide Fate And Dynamics in the Environment) is a one-dimensio nal, transient mathematical model which is capable of simulating the moveme nt of water and pesticides in the soil environment. PESTFADE was validated using field measured amounts of herbicide atrazine from the upper 20 cm of a loam soil in a three-year study in Quebec, Canada. Statistical techniques were employed to evaluate the accuracy/efficiency of model results in comp arison with the measured data. Model predictions for atrazine concentration in the upper 20 cm of the soil profile closely followed the observed value s. The model performance tests also provided acceptable model efficiencies, especially when the Gamble kinetics for adsorption was employed. Specifica lly, a high prediction efficiency (E-p) value of 0.82 was obtained from a G amble run, suggesting that the model worked satisfactorily. Although there were discrepancies between simulated and measured amounts of atrazine for s ome runs, they were attributed to experimental error as evidenced by a high standard deviation in the observed values. The results of this study showe d that PESTFADE can simulate the fate and behavior of atrazine in the soil, with good accuracy. (C) 1998 Elsevier Science B.V. All rights reserved.