Potential Role of Stabilized Criegee Radicals in Sulfuric Acid Production in a High Biogenic VOC Environment

Abstract

We present field observations made in June 2011 downwind of Dallas−Fort Worth, TX, and evaluate the role of stabilized Criegee radicals (sCIs) in gaseous sulfuric acid (H 2 SO 4 ) production. Zerodimensional model calculations show that sCI from biogenic volatile organic compounds composed the majority of the sCIs. The main uncertainty associated with an evaluation of H 2 SO 4 production from the sCI reaction channel is the lack of experimentally determined reaction rates for sCIs formed from isoprene ozonolysis with SO 2 along with systematic discrepancies in experimentally derived reaction rates between other sCIs and SO 2 and water vapor. In general, the maximum of H 2 SO 4 production from the sCI channel is found in the late afternoon as ozone increases toward the late afternoon. The sCI channel, however, contributes minor H 2 SO 4 production compared with the conventional OH channel in the mid-day. Finally, the production and the loss rates of H 2 SO 4 are compared. The application of the recommended mass accommodation coefficient causes significant overestimation of H 2 SO 4 loss rates compared with H 2 SO 4 production rates. However, the application of a lower experimental value for the mass accommodation coefficient provides good agreement between the loss and production rates of H 2 SO 4 . The results suggest that the recommended coefficient for the H 2 O surface may not be suitable for this relatively dry environment. ■ INTRODUCTIONMost sulfur compounds emitted to the atmosphere are in a reduced form (e.g., sulfur dioxide, SO 2 (IV)). Atmospheric gasphase oxidation processes sulfur throughout the troposphere and the stratosphere and transforms these emitted sulfur compounds into the most oxidized form of gas-phase sulfuric acid (H 2 SO 4 ), unless heterogeneous uptake transforms the sulfur into condensed-phase forms. The discussion in this paper will focus exclusively on gas-phase H 2 SO 4 formation from gas-phase SO 2 oxidation. Although sulfur compounds contribute a relatively minor fraction of the chemical composition of the troposphere, 1 the critical role of H 2 SO 4 in determining acidity in precipitation 2 and forming particles that influence regional and global climate has been highlighted. 3−5 Anthropogenic sulfur emission in the form of SO 2 is currently estimated to dominate global sulfur emissions, followed by oceanic dimethylsulfide (CH 3 SCH 3 ). 6 The gas-phase atmospheric oxidation processes of SO 2 were thought previously to be driven mostly by hydroxyl radical (OH), as shown in R1−R3. 7The potential role of stabilized Criegee biradicals (sCIs) 8 in SO 2 oxidation has been discussed since the 1970s. Cox and Penkett 9 reported significant SO 3 formation rates from chamber experiments with various alkene compounds, ozone (O 3 ), and SO 2 . They speculated sCIs prompted SO 2 oxidation because the reaction between SO 2 and O 3 is insignificant under atmospheric conditions. Calvert and Stockwell 2 presented comprehensive zero-dimensional model calculation results examining atmosp...

Airmass aging metrics derived from particle and other measurements near Fort Worth

“…Differences in diurnal profiles and in the comparisons shown 598 in Figures 4b, 5b, and 6b were evaluated using a student's t-test; results supported statistical 599 differences from hour to hour in diurnal profile and in the relationships shown in Figures 5b and 600 6b. 601 602 Toluene 15% (Kim et al, 2015) Photochemical Age 26% Benzene Figure S6. Time series of NO x (gray) and NO y (black) mixing ratios (ppbv).…”

Kinetics of dimethyl sulfide (DMS) reactions with isoprene-derived Criegee intermediates studied with direct UV absorption

“…In addition, utilizing the direct detection of CIs, a number of kinetic investigations of CI reactions, e.g. with SO 2 (Huang et al, 2015), water vapor (Chao et al, 2015), alcohols (Chao et al, 2019), thiols (Li et al, 2019), amines (Chhantyal-Pun et al, 2019), carbonyl molecules (Taatjes et al, 2012), and organic (Welz et al, 2014) and inorganic (Foreman et al, 2016) acids, etc., have been reported (Lee, 2015;Osborn and Taatjes, 2015;Lin and Chao, 2017;Khan et al, 2018;Cox et al, 2020).…”

Rates of Wintertime Atmospheric SO2 Oxidation based on Aircraft Observations during Clear‐Sky Conditions over the Eastern United States

“…CIs are produced by ozonolysis of unsaturated hydrocarbons in the atmosphere. CIs either decompose to radical species like OH, deactivate to a SCI and subsequently undergo a rearrangement reaction, or react with atmospheric species, such as SO 2 to form SO 3 (S. Kim, Guenther, et al, 2015;Sarwar et al, 2013;Welz et al, 2012), which is subsequently converted into H 2 SO 4 . Recent findings suggest that CI reactions with SO 2 might account for the discrepancy between the observed and modeled concentrations of H 2 SO 4 during both the summer and winter (Berndt et al, 2014;Boy et al, 2013; P. S. Kim, Jacob, et al, 2015;Mauldin Iii et al, 2012;Sarwar et al, 2014).…”