A European test of pesticide-leaching models: methodology and major recommendations

Applying a statewide geospatial leaching tool for assessing soil vulnerability ratings for agrochemicals across the contiguous United States

“…Simulating water flow and pollutant transport in the subsurface provided a structured approach to analyze the risk of contamination in response to these factors (Dusek et al, 2011;. Various models (e.g., MACRO, PRZM3, and HYDRUS) were available that evaluated contaminant leaching in the vadose zone (Holman et al, 2004;Vanclooster et al, 2000). The performance of simulation models varied considerably depending on soil hydrology and contaminant fate and transport processes ( Simunek, 2005).…”

“…The performance of simulation models varied considerably depending on soil hydrology and contaminant fate and transport processes ( Simunek, 2005). For example, the models that implemented the Richard equation were found to more accurately elucidate subsurface water flux, specifically in an upward direction, than cascading soil water balance models (Vanclooster et al, 2000). This is because cascading models do not account for the effect of soil texture on water movement precisely as well as are dedicated to a top-down (vertical) flow, as their name implies.…”

“…This is because cascading models do not account for the effect of soil texture on water movement precisely as well as are dedicated to a top-down (vertical) flow, as their name implies. There have been several studies that attempted to compare estimates of vertical concentration profiles among simulation models for a given scenario in a regulatory context (Dusek et al, 2011;Vanclooster et al, 2000). With increased complexity of modeled processes, a high quality monitoring data set, detailed soil profiles, and extensive computations are typically required to obtain the most accurate simulation results from any of these models ( Simunek, 2005;Vanclooster et al, 2000).…”

“…There have been several studies that attempted to compare estimates of vertical concentration profiles among simulation models for a given scenario in a regulatory context (Dusek et al, 2011;Vanclooster et al, 2000). With increased complexity of modeled processes, a high quality monitoring data set, detailed soil profiles, and extensive computations are typically required to obtain the most accurate simulation results from any of these models ( Simunek, 2005;Vanclooster et al, 2000). Therefore, simulation models of intermediate complexity or higher cannot be easily applied to large-scale leaching assessments (of pesticides and VOCs) that show high spatial and temporal heterogeneity in environmental conditions.…”

“…Although these differences are not significant in some areas, it is generally accepted that physically based screening tools which utilize basic properties that control contaminant movement tend to be more reliable and robust than subjective and empirical approaches. In addition, these empirical approaches of pesticide leaching will not show good performance in leaching assessment of new target compounds that involve the additional upward mass flux from soils such as VOCs (Hantush et al, 2002;Vanclooster et al, 2000).…”