Non-linear and time-dependent sorption are common compound properties that allow for a realistic description of the transport and degradation of agrochemicals in the vadose zone of the soil. The groundwater model FOCUS PRZM 3.5.2 includes these soil processes following intensive evaluation and technical dialog among European stakeholders. This approach is used in the EU regulatory process and as such, laboratory data needed to describe the enhanced binding processes are often available. The PRZM-GW model considers only linear sorption. Non-linear and time-dependent sorption can be included in PRZM-GW with the US EPA environmental scenarios to demonstrate the effect on the predicted groundwater concentrations. In some cases, significant reductions can be obtained, and the predicted concentrations were in general agreement with SCI-GROW concentrations and the field study results from which SCI-GROW was developed. The results suggest that incorporation of Freundlich sorption isotherms and time-dependent sorption into the exposure assessments for plant protection products would result in more realistic estimates of groundwater concentrations when justified based on laboratory and/or field data. This approach is therefore suggested as an efficient means of improving drinking water exposure assessments for North America.

Effect of refined environmental fate properties on groundwater concentrations calculated with PRZM-GW

246th National Meeting (2013)

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