Both USEPA field dissipation and EU FOCUS modeling guidance outline the use of inverse modeling as a means to understand dissipation pathways and derive degradation parameters for modeling endpoints from terrestrial field dissipation studies (TFD). As an alternate method to normalizing TFD studies, inverse modeling allows the model to take into account specific processes that may occur such as plant uptake, sorption, or photolysis, in addition to degradation. The modeling of two TFD studies are presented to illustrate the methodologies used to optimize input parameters against observed field data. The non-linear parameter estimation tool (PEST 9.0) was coupled with the USEPA PRZM model and separately the EU FOCUS PEARL model to estimate degradation parameters using site specific soils and weather data. Both models were able to predict observed pesticide residues accurately within the soil profile. Optimized parameters from inverse modeling can be used for further refinement of exposure assessments and provide added value for TFD studies.

Inverse modeling for the derivation of degradation parameters in European and North American terrestrial field dissipation studies

246th National Meeting (2013)

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