Organic Peroxides and Sulfur Dioxide in Aerosol: Source of Particulate Sulfate

Abstract

Sulfur oxides (SO x ) are important atmospheric trace species in both gas and particulate phases, and sulfate is a major component of atmospheric aerosol. One potentially important source of particulate sulfate formation is the oxidation of dissolved SO2 by organic peroxides, which comprises a major fraction of secondary organic aerosol (SOA). In this study, we investigated the reaction kinetics and mechanisms between SO2 and condensed-phase peroxides. pH-dependent aqueous phase reaction rate constants between S­(IV) and organic peroxide standards were measured. Highly oxygenated organic peroxides with O/C > 0.6 in α-pinene SOA react rapidly with S­(IV) species in the aqueous phase. The reactions between organic peroxides and S­(IV) yield both inorganic sulfate and organosulfates (OS), as observed by electrospray ionization ion mobility mass spectrometry. For the first time, 34S-labeling experiments in this study revealed that dissolved SO2 forms OS via direct reactions without forming inorganic sulfate as a reactive intermediate. Kinetics of OS formation was estimated semiquantitatively, and such reaction was found to account for 30–60% of sulfur reacted. The photochemical box model GAMMA was applied to assess the implications of the measured SO2 consumption and OS formation rates. Our findings indicate that this novel pathway of SO2–peroxide reaction is important for sulfate formation in submicron aerosol.

Fast oxidation of sulfur dioxide by hydrogen peroxide in deliquesced aerosol particles

“…As well, the importance of general acid catalysis needs to be considered not only for the many organic acids that are present under pollution conditions but potentially also for ammonium ions which are present in aerosol particles at very high concentrations. While such rate enhancements may arise under any conditions with a high aerosol liquid water content and solute concentrations, for the specific Chinese haze situation it is particularly important to assess these effects on the reactions of organic hydroperoxides, NO 2 and O 3 that also oxidize dissolved SO 2 (41), over a range of aerosol pH. This will permit a more comprehensive assessment of the overall rate of multiphase sulfur oxidation under cloud-free conditions.…”

Molecular Characterization of Organosulfates in Highly Polluted Atmosphere Using Ultra‐High‐Resolution Mass Spectrometry

“…Several recent studies have revealed the formation of OSs from photooxidation of anthropogenic precursors, such as polycyclic aromatic hydrocarbons (Riva et al, 2015) or long‐chain alkanes (Riva, Barbosa, et al, 2016), on sulfate seed particles. Moreover, direct formation of OSs from uptake of gaseous SO 2 by unsaturated fatty acids (Passananti et al, 2016; Shang et al, 2016) and organic peroxides (Wang, Zhou, et al, 2019) and OS formation from reaction of hydrogen sulfite with unsaturated carbonyl compounds in the presence of Fe 3+ (Huang, Cochran, et al, 2018) have been reported. However, the atmospheric relevance of these processes has yet to be elucidated.…”

Supplementary material to "Heterogeneous Interactions between SO<sub>2</sub> and Organic Peroxides in Submicron Aerosol"

“…As a result, the uptake rate was instead estimated by measuring the sulfate production rate using AMS. However, it should also be noted that the sulfate collection and ionization efficiencies of AMS are highly uncertain, since the yield of organosulfate is significant from these reactions (Wang et al, 2019), and AMS has a lower sensitivity towards organosulfates especially under humid conditions in the current study as indicated by ion chromatography and SMPS measurements ( Fig.S10-12) (Chen et al, 2019;Farmer et al, 2010).…”