A Closure Study of the Reaction between Sulfur Dioxide and the Sulfate Radical Ion from First-Principles Molecular Dynamics Simulations.

In a previous study, we applied quantum chemical methods to study the reaction between sulfur dioxide (SO2) and the sulfate radical ion (SO4(-)) at atmospheric relevant conditions and found that the most likely reaction product is SO3SO3(-). In the current study, we investigate the chemical fate of SO3SO3(-) by reaction with ozone (O3) using first-principles molecular dynamics collision simulations. This method assesses both dynamic and steric effects in the reactions and therefore provides the most likely reaction pathways. We find that the majority of the collisions between SO3SO3(-) and O3 are nonsticking and that the most frequent reactive collisions regenerate sulfate radical ions and produce sulfur trioxide (SO3) while ejecting an oxygen molecule (O2). The rate of this reaction is determined to be 2.5 × 10(-10) cm(3) s(-1). We then conclude that SO4(-) is a highly efficient catalyst in the oxidation of SO2 by O3 to SO3.