The Reaction of Sulfur Dioxide Radical Cation with Hydrogen and its Relevance in Solar Geoengineering Models. Issue 11 (29th April 2020)

• Record Type: Journal Article
• Authors: Satta, Mauro; Cartoni, Antonella; Catone, Daniele; Castrovilli, Mattea Carmen; Bolognesi, Paola; Zema, Nicola; Avaldi, Lorenzo
• Is Part Of: Chemphyschem. Volume 21:Issue 11(2020)
• Page Start: 1146
• Page End: 1156
• Publication Date: 2020-04-29
• Subjects: ion-molecule reactions -- rate coefficient -- reaction mechanisms -- synchrotron radiation -- VTST; Chemistry, Physical and theoretical -- Periodicals; 541.05
• DOI: 10.1002/cphc.202000194
• Languages: English
• ISSNs: 1439-4235

Abstract

Abstract: SO 2 has been proposed in solar geoengineering as a precursor of H 2 SO 4 aerosol, a cooling agent active in the stratosphere to contrast climate change. Atmospheric ionization sources can ionize SO 2 into excited states of S O 2 · +, which quickly reacts with trace gases in the stratosphere. In this work we explore the reaction of H 2 D 2 with S O 2 · + excited by tunable synchrotron radiation, leading to H S O 2 + + H ( D S O 2 + + D ), where H contributes to O 3 depletion and OH formation. Density Functional Theory and Variational Transition State Theory have been used to investigate the dynamics of the title barrierless and exothermic reaction. The present results suggest that solar geoengineering models should test the reactivity of S O 2 · + with major trace gases in the stratosphere, such as H 2 since this is a relevant channel for the OH formation during the nighttime when there is not OH production by sunlight. OH oxides SO 2, triggering the chemical reactions leading to H 2 SO 4 aerosol. Abstract : In the solar geoengineering strategies SO 2 is injected in the stratosphere, and it can be ionized by cosmic rays and reacts with trace gases, such as H 2 O and H 2 . These reactions produce the atmospheric relevant oxidant OH, which in the nighttime is an alternative process to that occurring during daytime due to photodissociation of O 3 by sunlight. OH triggers the SO 2 reactions leading to H 2 SO 4 aerosol formation which acts as a cooling agent in the stratosphere.