According to EU FOCUS groundwater guidance, Tier-2a can be performed with refined parameters, which can include aged sorption parameters from lab(DT50 eq, 1/n, Fne, Kdes, Kom).  But there is lack of guidance for deriving aged sorption parameters from terrestrial field dissipation (TFD) studies. Product A is a relatively mobile pesticide and shows evidence of aged sorption in lab and in TFD studies. For TFD studies, inverse modeling with PEARL and PEST was used to derive aged sorption parameters with two approaches – total residues and depth dependent. Step-wise optimization vs all parameter optimization approaches were also tested. Visual and statistical assessments were used to assess the reliability of fits and parameters.  Advantages and challenges of each approaches will be discussed. Aged sorption parameters for metabolites were also derived by fitting parent and metabolite together. Effects of soil type, irrigation applied (soil moisture) on aged sorption were also evaluated.<br/>

Inverse modeling approaches for derivation of aged sorption parameters from terrestrial field dissipation studies

2019 Fall National Meeting

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