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+SO2)) 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+SO2)) was increased from 7 x 10(-14) cm(3) s(-1) to a suggested value of 3.9 x 10(-11) cm(3) 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+H2O)) was also increased based on the reported ratio of k(SCI+H2O) to (k(SCI+SO2)) (6.1 x 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+H2O). Small SCIs such as CH2OO and CH3CHOO, and SCIs from isoprene (MVKOO) and monoterpene (APINBOO) oxidation are the dominant SCIs in the eastern US. (C) 2013 Elsevier Ltd. All rights reserved.