The behavior of organic arsenical herbicides in the environment is fundamentally different from that of most pesticides registered by the U.S. Environmental Protection Agency, the European Food & Safety Authority, and other regulatory agencies. Specifically, organic arsenicals extensively sequester within the soil matrix thereby limiting runoff, leaching, and access by microorganisms to methylate or demethylate the compounds. Modeling the kinetics of sequestration and transformation for compounds of this nature can be challenging due to edaphic influences on chemical sorption such as pH, clay content, and minerals, and the potential for reverse reactions to occur. A method was developed to simulate key kinetic processes in USEPA’s Pesticide Root Zone Model (PRZM5) using a series of first-order reactions. The presentation includes the configuration of the model, its application to predict organic arsenical behavior in its use environment, and a comparison of predicted outcome to empirical data.

Modeling the sequestration and transformation kinetics of organic arsenical herbicides in a regulatory framework

ACS Fall 2021

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