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 cm³ s^-1. We then conclude that SO₄ ^- is a highly efficient catalyst in the oxidation of SO₂ by O₃ to SO₃. (Chemical Equation Presented).