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. Résumé : Le modèle PRZM2 consiste en un modèle informatique conçu afin de simuler le transport des pesticides à travers le profil pédologique dans des conditions de sol saturé et de sol non saturé. La capacité de PRZM2 à simuler le transport et le sort du métolachlore sera examiné et les résultats de simulation obtenus à partir d'une étude sur des colonnes de sol seront évalués. Les paramètres d'entrée et les données mesurées ont été obtenus à partir d'une expérimentation sur des colonnes de sol. Les données de sortie du modèle ont été comparées aux valeurs mesurées et des analyses statistiques ont été faites à l'aide de la méthode de coefficient de performance. D'après les résultats simulés, le métolachlore n'a pas été lessivé au-dessous de 0,2 m de profondeur. Cependant, des résidus d'herbicides ont été détectés dans la solution du sol à des profondeurs plus grandes dans les colonnes de sol. Bien que les résultats simulés quant au

Simulated Fate and Transport of Metolachlor in the Unsaturated Zone, Maryland, USA

“…A limited number of studies have examined metolachlor attenuation in the unsaturated zone. Studies have examined data derived from laboratory experiments (Jebellie et al, 2004; Sanyal and Kulshrestha, 2003; Wietersen et al, 1993) and field sampling efforts (Zacharias et al, 1999; Hippe and Hall, 1996; Smith and Parrish, 1993; Trevisan et al, 1993; Mullaney et al, 1991). Results of these studies have shown that metolachlor concentrations generally taper off to values less than the method reporting limit between 0.1 and 0.5 m and are immeasurable in the saturated zone.…”

“…Results of these studies have shown that metolachlor concentrations generally taper off to values less than the method reporting limit between 0.1 and 0.5 m and are immeasurable in the saturated zone. Numerical models, including AgriFlux (Novak et al, 2003), GLEAMS (Zacharias et al, 1999), LEACHM (Trevisan et al, 1993), PRZM (Trevisan et al, 1993), PRZM2 (Jebellie et al, 2004), MACRO (Balderacchi et al, 2002), and Opus (Zacharias et al, 1999), have been used in conjunction with field and laboratory data to examine the capabilities of models to simulate metolachlor leaching and to identify factors affecting attenuation. Most models have demonstrated the capability to simulate metolachlor concentrations near the surface but have been less accurate at forecasting distributions below the root zone.…”

Estimation of contaminant transport parameters for a tropical sand in a sand tank model

“…Several hygiene related deaths globally (Victor, 2008). There is researchers, in the area of groundwater/subsurface now an urgent need to scientifically harness both contaminant engineering, have studied contaminant human and material resources especially in the transport and transformation in 1-D laboratory soil emerging field of geoenvironmental engineering in column (Jebellie et al, 2004; Adams and Guzman order to meet the target 10 (Halve, by 2015, the Mirbagheri and Hashemi Monfared, 2009). proportion of people without sustainable access to safe Sand tank model is a 3-D physical aquifer model and drinking water and basic sanitation) of the pertinent ever since, early 1980s, it has been widely employed in millennium development goal (goal 7 -ensure several fields of study in the laboratory to observe environmental sustainability).…”