Terbuthylazine (TBA) is a widely used herbicide, and its heterogeneous reaction with OH radicals is important for assessing its potential to undergo atmospheric long-range transport and to affect the environment and public health. The apparent reaction rate coefficients obtained in different experimental investigations, however, vary by orders of magnitude depending on the applied experimental techniques and conditions. In this study, we used a kinetic multilayer model of aerosol chemistry with reversible surface adsorption and bulk diffusion (KM-SUB) in combination with a Monte Carlo genetic algorithm to simulate the measured decay rates of TBA. Two experimental data sets available from different studies can be described with a consistent set of kinetic parameters resolving the interplay of chemical reaction, mass transport, and shielding effects. Our study suggests that mass transport and shielding effects can substantially extend the atmospheric lifetime of reactive pesticides from a few days to weeks, with strong implications for long-range transport and potential health effects of these substances.

Department of Chemistry University of California Irvine California 92617 United States

Forschungsstelle für Atmosphärische Chemie University of Bayreuth 95440 Bayreuth Germany

Multiphase Chemistry Department Max Planck Institute for Chemistry 55128 Mainz Germany

Research Centre for Toxic Compounds in the Environment Masaryk University 62500 Brno Czech Republic

School of Chemical and Biomolecular Engineering Georgia Institute of Technology Atlanta Georgia 30332 United States

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