Evaluation of Five Simulation Models for Predicting Aldicarb and Bromide Behavior Under Field Conditions

Five pesticide simulation models (Chemical Movement in Layered Soils (CLMS), Method of Underground Solute Evaluation (MOUSE), Pesticide Root Zone Model (PRZM), Groundwater Leading Effects of Agriculture Management Systems (GLEAMS), and Leaching Estimation and Chemistry Model-Pesticides (LEACHMP)) were evaluated using data for the transport and transformation of aldicarb and bromide in the unsaturated zone. Although these models have been tested separately, to date no effort has been made to evaluate all of them using a comprehensive data set from a single field study. Model performance was evaluated based on their ability to predict: the depth of solute center of mass, solute dissipation, and solute concentration distributions within the soil profile. GLEAMS and MOUSE underestimated bromide and aldicarb dissipation, while the other models provided satisfactory predictions of both solute center of mass and pesticide degradation. None of the models accurately described measured solute concentration distributions. Recommendations are made for the selection and use of the models based on objective and subjective criteria including graphical analysis, objective functions, intended model use, and the difficulty in obtaining model input data.