Temperature and acidity dependence of secondary organic aerosol formation from <i>α</i>-pinene ozonolysis with a compact chamber system

Abstract

Abstract. Secondary organic aerosols (SOAs) affect human health and climate change prediction; however, the factors (e.g., temperature, acidity of pre-existing particles, and oxidants) influencing their formation are not sufficiently resolved. Using a compact chamber, the temperature and acidity dependence of SOA yields and chemical components in SOA from α-pinene ozonolysis were systematically investigated under 278, 288, and 298 K temperatures using neutral ((NH4)2SO4) and acidic (H2SO4+((NH4)2SO4)) seed aerosols. SOA components with m/z less than 400 were analyzed using negative electrospray ionization liquid-chromatography time-of-flight mass spectrometry. Based on the slightly negative temperature dependence of the SOA yields, the enthalpies of vaporization under neutral and acidic seed conditions were estimated to be 25 and 44 kJ mol−1, respectively. In addition, SOA yields increased with an increase in the acidity of seed particles (solid/near-solid state) at low SOA mass loadings, when compared with the seed particle amounts. Acidity dependence analysis of the chemical formula, molecular mass, and O:C ratio of the detected compounds indicated the enhanced formation of multiple oligomers in the wide molecular mass range with a wide range of O:C ratios under acidic seed conditions. The peak abundances of some chemical compounds increased with an increase in the acidity of seed particles (e.g., m/z 197, 311, 313, 339, 355, and 383), while decreases in the peak abundances of some chemical compounds were observed (e.g., m/z 171, 185, 215, 343, and 357). The acidity dependence could be explained by acid-catalyzed heterogeneous reactions or acid-catalyzed decomposition of hydroperoxides. In addition, organosulfate (OS) formation was observed under acidic seed conditions. Six out of the 11 detected OSs were potentially formed via the aldehyde + HSO4- pathway.

New Particle Formation Promoted by OH Reactions during α-Pinene Ozonolysis

“…A temperature-controlled test chamber described previously was used in this study. The chamber is a cuboid-shaped Teflon bag (FEP; 0.7 m 3 volume, 900 mm × 600 mm × 1300 mm; 50 μm thickness; Takesue, Japan) contained in a constant temperature cabinet (HCLP-1240; NK System, Japan).…”

Hydronium Ion Acidity Above and Below the Interface of Aqueous Microdroplets

“…The fast rates of interfacial reactions on microdroplets has enhanced their participation in atmospheric chemistry . Because protonation and deprotonation are key steps in many organic reactions, the recent finding that atmospheric microdroplets are more acidic than previously thought , brings about the questions of how acidity could affect interfacial reactions and whether the surface of water is more or less acidic than the bulk. − …”

“…11 The fast rates of interfacial reactions on microdroplets has enhanced their participation in atmospheric chemistry. 3 Because protonation and deprotonation are key steps in many organic reactions, the recent finding that atmospheric microdroplets are more acidic than previously thought 12,13 brings about the questions of how acidity could affect interfacial reactions 14 and whether the surface of water is more or less acidic than the bulk. 15−17 In this letter, we summarize experimental results obtained in our laboratories on the protonation of organic gases in collisions with microdroplets as a function of pH that bear on these important issues.…”

Autoxidation of terpenes, a common pathway in tropospheric and low temperature combustion conditions: the case of limonene and α-pinene

“…Chemical compounds with relative intensity less than 1 ppm to the highest mass peak in the mass spectrum were not considered. Nevertheless, it should be considered that some of the molecules presented in this study could result from our experimental conditions (continuous flow reactor, reagent concentration, temperature, reaction time) and to some extent from our acquisition conditions, different from those of the previous studies (Deng et al, 2021;Quéléver et al, 2019;Meusinger et al, 2017;Krechmer et al, 2016;Tomaz et al, 2021;Fang et al, 2017;Witkowski and Gierczak, 2017;Jokinen et al, 2015b;Nørgaard et al, 2013;Bateman et al, 2009;Walser et al, 2008;Warscheid and Hoffmann, 2001;Hammes et al, 2019;Kundu et al, 2012). Indeed, the use of a continuous flow reactor operating at elevated temperature, as well as a high initial concentration of reagents can induce the formation of combustion-specific products, which does not exclude their possible formation under atmospheric conditions.…”

“…This represents 31% of the chemical formulae for the ozonolysis of α-pinene and 31% for those of limonene ozonolysis. For α-pinene, the similarities compared to combustion are specific to each study:(Deng et al, 2021) 69%(Meusinger et al, 2017) 46%(Quéléver et al, 2019)7%(Krechmer et al, 2016) 23%. Chemical formulae common to all studies were not identified.…”