Computer Simulation of Fate and Transport of Metolachlor in a Soil Column Study

Abstract

PRZM2 is a computer model developed to simulate pesticide transport through the soil profile under saturated and unsaturated conditions. The ability of PRZM2 to simulate the fate and transport of metolachlor will be examined and the simulation results from a soil column study will be evaluated. The input parameters and the measured data were obtained from a soil column study. The model outputs were compared to the measured values and statistical analyses were performed using the coefficient of performance approach. Based on the simulated results, metolachlor did not leach below 0.2 m depth, however, herbicide residue was detected in the soil solution at deeper depths in the soil columns. Although the simulated metolachlor results at 0.1 m depth followed the observed time and depth pattern, the model did not perform well in simulating metolachlor concentration at other depths. The statistical analyses show that the simulated metolachlor concentration was in poor agreement with the corresponding measured data over the entire experimental period. Higher or lower estimation of metolachlor concentrations by the model may be due to a simplistic treatment of matrix flow and the absence of a realistic macropore flow component. The existing mathematical formulation to handle transport and transformation processes may not adequately reflect the realistic fate and transport of metolachlor in soil. This may imply the need for further research and validation of PRZM2 for herbicides. © 2004, Taylor & Francis Group, LLC.