Laboratory chamber studies on the formation of organosulfates from reactive uptake of monoterpene oxides

Abstract

Evidence from field measurements suggests that organosulfates contribute substantially to ambient secondary organic aerosol (SOA) and might dominate a considerable fraction of total sulfur in tropospheric particles. While alcohols and epoxides are suggested to be most likely precursors for organosulfates in SOA, their reactivity in acidic particles and their potential for organosulfate formation are still unclear. In the present study, a series of aerosol chamber experiments was performed to investigate the formation of organosulfates from reactive uptake of monoterpene oxides (alpha-pinene oxide and beta-pinene oxide) and acid catalysed isomerisation compounds of alpha-pinene oxide (campholenic aldehyde and carveol) on neutral and acidic sulfate particles. Organosulfate formation was observed only under acidic conditions for both monoterpene oxides and, to a lesser extent, campholenic aldehyde, indicating that epoxides most likely serve as precursors for some of the organosulfates reported from both ambient and laboratory SOA samples. Structures of organosulfates were elucidated by comparing the tandem mass spectrometric, accurate mass and ion mobility data obtained for both the synthesised reference compounds and aerosol chamber-generated organosulfates. In the experiment performed using beta-pinene oxide and acidic sulfate seed particles, an organosulfate with a sulfate group at a tertiary carbon atom accounts for 64% of the detected organosulfates. In contrast, an organosulfate with a sulfate group at a secondary carbon atom accounts for 80% of the detected organosulfates in the sample from alpha-pinene oxide/acidic sulfate particle experiment. The concentration of beta-pinene-derived organosulfates was higher than known alpha-pinene oxidation products such as pinic acid and pinonic acid in an ambient aerosol sample collected at a Norwegian spruce forest site during the summer time, ranging up to 23 ng m(-3). Furthermore, alpha-pinene oxide is found to isomerise readily on the wet seed particle surface, forming campholenic aldehyde. It is likely that other epoxides also play an important role for the formation of organosulfates under atmospheric conditions, and the isomerisation of epoxides may be an important route for the formation of some SOA constituents whose structures do not resemble precursor volatile organic compounds (VOCs).

Effects of NO<sub><i>x</i></sub> and SO<sub>2</sub> on the secondary organic aerosol formation from photooxidation of <i>α</i>-pinene and limonene

“…The significant contribution of organic nitrate to nitrate may have important implications for deriving the hygroscopicity from chemical composition. For example, a number of studies derived the hygroscopicity parameter by linear combination of the hygroscopicity parameters of various components such as sulfate, nitrate, and organics, assuming all nitrates are inorganic nitrate Cubison et al, 2008;Yeung et al, 2014;Bhattu and Tripathi, 2015;Jaatinen et al, 2014;Moore et al, 2012;Gysel et al, 2007). Because the hygroscopicity parameter of organic nitrate may be much lower than inorganic nitrate (Suda et al, 2014), such derivation may overestimate hygroscopicity.…”

“…Secondly, H 2 SO 4 formed by photooxidation of SO 2 can enhance SOA formation via acid-catalyzed heterogeneous uptake, an important SOA formation pathway initially found from isoprene photooxidation (Jang et al, 2002;Lin et al, 2012;Surratt et al, 2007) and later also in the photooxidation of other compounds such as anthropogenic VOC (Chu et al, 2016;Liu et al, 2016). For the products from monoterpene oxidation, such an acid-catalyzed effect may also occur (Northcross and Jang, 2007;Wang et al, 2012;Lal et al, 2012;Zhang et al, 2006;Ding et al, 2011;Iinuma et al, 2009) and, in this study, the particles were acidic with the molar ratio of NH + 4 to SO 2− 4 around 1.5-1.8, although no aqueous phase was formed.…”

Organosulfates from Pinene and Isoprene over the Pearl River Delta, South China: Seasonal Variation and Implication in Formation Mechanisms

“…During the day, NO would compete against RO 2 and HO 2 to react with hydroperoxy radical 1; and NO 3 reaction could be ignored due to its high photolysis rate. Thus, the fractional yield of hydroxynitrate in the OH pathway is calculated by f OH = k 7 2 ] levels might be comparable in the ambient (e.g., 6.8 × 10 8 molecules cm −3 vs 4.5 × 10 8 molecules cm −3 in summer of Beijing), 64 here we assumed that [RO 2 ] had the same levels as [HO 2 ] . Thus, the f OH and f NO3 were calculated as 0.23 and 1.2 × 10 −4 , respectively with the rate constants in Scheme 1 at T = 298.15 K. Although both hydroperoxy radical 1 and nitroperoxy radical 1 are potential sources of hydroxynitrate, the hydroperoxy pathway initiated by OH in the day is far more efficient.…”

Reactive uptake of ammonia to secondary organic aerosols: kinetics of organonitrogen formation

“…Secondary formation of particulate organics have also recently been considered another possible source of BrC through heterogeneous or multiphase chemical reactions Zarzana et al, 2012;Nguyen et al, 2013;Powelson et al, 2014), in which heteroatoms including O, S and N can be introduced into the particulate matter via a variety of precursors. For example, as characteristic components of HULIS (Nguyen et al, 2014, organosulfates and organonitrates have been observed in both laboratory generated (Liggio and Li, 2006b;Iinuma et al, 2009;Russell et al, 2011;Darer et al, 2011) and ambient organic particles (Hawkins et al, 2010;Surratt et al, 2006;Russell et al, 2011). Oxygen-and nitrogen-containing oligomers of high molecular weight have also been identified in secondary organic aerosols (SOA) (Kalberer et al, 2004).…”