This presentation describes a conceptual model for a pesticide that specifically addresses the question: Why does dissipation and mobility in the field differ from that observed under laboratory conditions? A conceptual model hypothesis was developed on the basis of established physical processes and experimental data and tested against a range of higher-tier laboratory studies to understand the mechanism by which photolysis acts as a major degradation route in the field. A re-parameterization of the USEPA regulatory model, Pesticide Root Zone Model (PRZM), was proposed to reflect a conceptual model describing the dissipation of the pesticide under actual-use conditions. The refined model predicted soil residues that were a significantly better match to the observed data from the field studies compared to those from unrefined modelling using standard regulatory modelling inputs. This suggests that the conceptual model is generally applicable and the use of the re-parameterized model for risk assessment is justifiable.

Development and validation of a conceptual model of pesticide dissipation pathways under field conditions

246th National Meeting (2013)

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