Role of Criegee intermediates in the formation of sulfuric acid at a Mediterranean (Cape Corsica) site under influence of biogenic emissions

Kukui, Alexandre; Chartier, Michel; Wang, Jinhe; Chen, Hui; Dusanter, Sébastien; Sauvage, Stéphane; Michoud, Vincent; Locoge, Nadine; Gros, Valérie; Bourrianne, Thierry; Sellegri, Karine; Pichon, Jean-Marc

Reaction of stabilized Criegee intermediates (SCIs) with SOinline-formula2 was proposed as an additional pathway of gaseous sulfuric acid (Hinline-formula2SOinline-formula4) formation in the atmosphere, supplementary to the conventional mechanism of Hinline-formula2SOinline-formula4 production by oxidation of SOinline-formula2 in reaction with OH radicals. However, because of a large uncertainty in mechanism and rate coefficients for the atmospheric formation and loss reactions of different SCIs, the importance of this additional source is not well established. In this work, we present an estimation of the role of SCIs in Hinline-formula2SOinline-formula4 formation at a western Mediterranean (Cape Corsica) remote site, where comprehensive field observations including gas-phase Hinline-formula2SOinline-formula4, OH radicals, SOinline-formula2, volatile organic compounds (VOCs) and aerosol size distribution measurements were performed in July–August 2013 as a part of the project ChArMEx (Chemistry-Aerosols Mediterranean Experiment). The measurement site was under strong influence of local emissions of biogenic volatile organic compounds, including monoterpenes and isoprene generating SCIs in reactions with ozone, and, hence, presenting an additional source of Hinline-formula2SOinline-formula4 via SOinline-formula2 oxidation by the SCIs. Assuming the validity of a steady state between Hinline-formula2SOinline-formula4 production and its loss by condensation on existing aerosol particles with a unity accommodation coefficient, about 90 % of the Hinline-formula2SOinline-formula4 formation during the day could be explained by the reaction of SOinline-formula2 with OH. During the night the oxidation of SOinline-formula2 by OH radicals was found to contribute only about 10 % to the Hinline-formula2SOinline-formula4 formation. The accuracy of the derived values for the contribution of OH inline-formula+ SOinline-formula2 reaction to the Hinline-formula2SOinline-formula4 formation is limited mostly by a large, at present factor of 2, uncertainty in the OH inline-formula+ SOinline-formula2 reaction rate coefficient. The contribution of the SOinline-formula2 oxidation by SCIs to the Hinline-formula2SOinline-formula4 formation was evaluated using available measurements of unsaturated VOCs and steady-state SCI concentrations estimated by adopting rate coefficients for SCI reactions based on structure–activity relationships (SARs). Thepage13334 estimated concentration of the sum of SCIs was in the range of (1–3) inline-formula× 10inline-formula3 molec. cminline-formula−3. During the day the reaction of SCIs with SOinline-formula2 was found to account for about 10 % and during the night for about 40 % of the Hinline-formula2SOinline-formula4 production, closing the Hinline-formula2SOinline-formula4 budget during the day but leaving unexplained about 50 % of the Hinline-formula2SOinline-formula4 formation during the night. Despite large uncertainties in used kinetic parameters, these results indicate that the SOinline-formula2 oxidation by SCIs may represent an important Hinline-formula2SOinline-formula4 source in VOC-rich environments, especially during nighttime.

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Kukui, Alexandre / Chartier, Michel / Wang, Jinhe / et al: Role of Criegee intermediates in the formation of sulfuric acid at a Mediterranean (Cape Corsica) site under influence of biogenic emissions. 2021. Copernicus Publications.

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