Oxidation of SO<sub>2</sub> by stabilized Criegee intermediate (sCI) radicals as a crucial source for atmospheric sulfuric acid concentrations

Abstract

Abstract. The effect of increased reaction rates of stabilized Criegee intermediates (sCIs) with SO2 to produce sulfuric acid is investigated using data from two different locations, SMEAR II, Hyytiälä, Finland, and Hohenpeissenberg, Germany. Results from MALTE, a zero-dimensional model, show that using previous values for the rate coefficients of sCI + SO2, the model underestimates gas phase H2SO4 by up to a factor of two when compared to measurements. Using the rate coefficients recently calculated by Mauldin et al. (2012) increases sulfuric acid by 30–40%. Increasing the rate coefficient for formaldehyde oxide (CH2OO) with SO2 according to the values recommended by Welz et al. (2012) increases the H2SO4 yield by 3–6%. Taken together, these increases lead to the conclusion that, depending on their concentrations, the reaction of stabilized Criegee intermediates with SO2 could contribute as much as 33–46% to atmospheric sulfuric acid gas phase concentrations at ground level. Using the SMEAR II data, results from SOSA, a one-dimensional model, show that the contribution from sCI reactions to sulfuric acid production is most important in the canopy, where the concentrations of organic compounds are the highest, but can have significant effects on sulfuric acid concentrations up to 100 m. The recent findings that the reaction of sCI + SO2 is much faster than previously thought together with these results show that the inclusion of this new oxidation mechanism could be crucial in regional as well as global models.

Reactivity of stabilized Criegee intermediates (sCIs) from isoprene and monoterpene ozonolysis toward SO<sub>2</sub> and organic acids

“…Sulfuric acid plays a key role in Earth's atmosphere, triggering secondary aerosol formation (Kulmala et al, 2004;Berndt et al, 2005, Riipinen et al, 2007Sipilä et al, 2010;Kerminen et al, 2010), and thus connects natural and anthropogenic SO 2 emissions to global climate via indirect aerosol effects on radiative forcing. The effect of sCI on SO 2 oxidation was assessed by Boy et al (2013), who simulated sulfuric acid production at the SMEAR (Station for measuring atmosphere-ecosystem relations) II boreal forest field station using the reaction rate coefficients suggested by Mauldin III et al (2012). Their results supported the experimental observations by Mauldin III et al (2012), showing that a signif-icant fraction (several tens of percents) of ground-level gas phase sulfuric acid originates probably from sCI-initiated oxidation of SO 2 .…”

Online measurements of water-soluble organic acids in the gas and aerosol phase from the photooxidation of 1,3,5-trimethylbenzene

“…Recent studies show that SO 2 reacts much faster with Criegee radicals than previously reported (10 −13 -10 −11 cm 3 s −1 ; Welz et al, 2012;Mauldin III et al, 2012;Boy et al, 2013). The differences in the experiments with and without SO 2 could be explained by reaction of a precursor Criegee radical with that species, hindering the formation of these acids.…”

The UV absorption spectrum of the simplest Criegee intermediate CH2OO

“…Now it is generally accepted that ozonolysis of alkenes proceeds via Criegee intermediates, highly reactive species postulated in 1949 by Rudolf Criegee. 1,2 In the troposphere, Criegee intermediates are involved in several important atmospheric reactions, 3 including reactions with SO 2 and NO 2 , [4][5][6][7] or can be photolyzed by near UV light, [7][8][9][10] as shown for CH 2 The formation of SO 3 and NO 3 , as in (R2) and (R3), plays an important role in atmospheric chemistry, 11,12 including aerosol and cloud formation. The formation of O( 1 D), as in (R4), will result in OH formation through (R5).…”