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Updated: Oct 29, 2026

Production and Measurement of Organic Particulate Matter in the Harvard Environmental Chamber
Published on: November 18, 2018
Revisiting atmospheric sulfur chemistry: Acid-catalyzed pathways do not control H2SO4 formation
Bo Long1, Chaolu Xie2, Joseph S Francisco3,4
1College of Materials Science and Engineering, Guizhou Minzu University, Guiyang 550025, China.
Abstract:
Sulfuric acid (H₂SO4) drives new particle formation and radiatively important aerosol processes in the atmosphere, but its formation pathways remain poorly resolved because of limited kinetics data. To clarify these pathways, we combined coupled-cluster calculations, reaction rate theory, and a global chemistry transport model to quantify acid-catalyzed SO3 hydration and its atmospheric significance. We find that the overall kinetics is not governed by a tight transition state but rather is controlled by a preceding loose transition state associated with the formation of the precursor complex of the acid-catalyzed SO3 hydration. Our results reverse a recent view that acid catalysis is the dominant contributor to atmospheric SO3 hydration, instead supporting an earlier view that water catalysis dominates SO3 hydration. Incorporating the revised kinetics into the GEOS-Chem atmospheric model reveals no significant impact of acid-catalyzed SO3 hydration on the simulated concentrations of H2SO4. The present findings highlight the critical roles of variational transition states in kinetic modeling.
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