Role of stabilized Criegee Intermediates in the formation of atmospheric sulfate in eastern United States

A Community Multiscale Air Quality model with the Master Chemical Mechanism is applied to evaluate the reactions of stabilized Criegee Intermediates SCIs with SO2 ( k SCI + SO 2 ) on sulfate aerosols in the eastern United States (US) during the summer of 2006. Surface sulfate concentrations and total sulfate columns increased by as much as 18% and 6%, respectively, when ( k SCI + SO 2 ) was increased from 7 × 10−14 cm3 s−1 to a suggested value of 3.9 × 10−11 cm3 s−1. The episode-average increase of the top-of-atmosphere direct radiative forcing due to the additional sulfate can be as much as −0.7 W m−2 (5%). However, if the SCI + H2O reaction rate constant ( k SCI + H 2 O ) was also increased based on the reported ratio of kSCI+H2O to ( k SCI + SO 2 ) (6.1 × 10−5), the surface sulfate and total sulfate column increases were less than 0.5%, which suggests that the impact of SCIs on sulfate may be insignificant and additional studies are needed to better determine k SCI + H 2 O . Small SCIs such as CH2OO and CH3CHOO, and SCIs from isoprene (MVKOO) and monoterpene (APINBOO) oxidation are the dominant SCIs in the eastern US.