Characterization of polar organosulfates in secondary organic aerosol from the unsaturated aldehydes 2-<i>E</i>-pentenal, 2-<i>E</i>-hexenal, and 3-<i>Z</i>-hexenal

Abstract

Abstract. We show in the present study that the unsaturated aldehydes 2-E-pentenal, 2-E-hexenal, and 3-Z-hexenal are biogenic volatile organic compound (BVOC) precursors for polar organosulfates with molecular weights (MWs) 230 and 214, which are also present in ambient fine aerosol from a forested site, i.e., K-puszta, Hungary. These results complement those obtained in a previous study showing that the green leaf aldehyde 3-Z-hexenal serves as a precursor for MW 226 organosulfates. Thus, in addition to isoprene, the green leaf volatiles (GLVs) 2-E-hexenal and 3-Z-hexenal, emitted due to plant stress (mechanical wounding or insect attack), and 2-E-pentenal, a photolysis product of 3-Z-hexenal, should be taken into account for secondary organic aerosol and organosulfate formation. Polar organosulfates are of climatic relevance because of their hydrophilic properties and cloud effects. Extensive use was made of organic mass spectrometry (MS) and detailed interpretation of MS data (i.e., ion trap MS and accurate mass measurements) to elucidate the chemical structures of the MW 230, 214 and 170 organosulfates formed from 2-E-pentenal and indirectly from 2-E-hexenal and 3-Z-hexenal. In addition, quantum chemical calculations were performed to explain the different mass spectral behavior of 2,3-dihydroxypentanoic acid sulfate derivatives, where only the isomer with the sulfate group at C-3 results in the loss of SO3. The MW 214 organosulfates formed from 2-E-pentenal are explained by epoxidation of the double bond in the gas phase and sulfation of the epoxy group with sulfuric acid in the particle phase through the same pathway as that proposed for 3-sulfooxy-2-hydroxy-2-methylpropanoic acid from the isoprene-related α,β-unsaturated aldehyde methacrolein in previous work (Lin et al., 2013). The MW 230 organosulfates formed from 2-E-pentenal are tentatively explained by a novel pathway, which bears features of the latter pathway but introduces an additional hydroxyl group at the C-4 position. Evidence is also presented that the MW 214 positional isomer, 2-sulfooxy-3-hydroxypentanoic acid, is unstable and decarboxylates, giving rise to 1-sulfooxy-2-hydroxybutane, a MW 170 organosulfate. Furthermore, evidence is obtained that lactic acid sulfate is generated from 2-E-pentenal. This chemistry could be important on a regional and local scale where GLV emissions such as from grasses and cereal crops are substantial.

Chemical composition of isoprene SOA under acidic and non-acidic conditions: effect of relative humidity

“…These processes result in the formation of gas and aerosol products including numerous oxidized SOA components. Aerosol species previously reported include 2-methyltetrols, 2-methylglyceric acid, C 5 -alkene triols, and organosulfates (i.e., Edney et al, 2005;Surratt et al, 2007aSurratt et al, , 2010Riva et al, 2016;Spolnik et al, 2018). While many of these are formed through multiphase chemistry (e.g., isoprene epoxydiol (IEPOX) channel), we cannot exclude their gas-phase formation at least for 2-methyltetrols, probably in part through re-evaporation processes (Issacman-VanWertz et al, 2016), and for 2methylglyceric acid, as these compounds have been linked to gas-phase reaction products from the oxidation of isoprene and in ambient PM 2.5 (Xie at al., 2014).…”

“…Atmospheric organosulfates are another class of organic compounds formed from atmospheric reactions of various precursors, including isoprene, and have been identified as components of ambient particulate matter (PM; Surratt et al, 2008;Froyd et al, 2010;Stone et al, 2012;Tolocka and Turpin, 2012). The most common isoprene organosulfates have been identified both in smog chamber experiments and in field studies (Surratt et al, 2007a(Surratt et al, , 2008Gomez-Gonzalez et al, 2008;Shalamzari et al, 2013;Tao et al, 2014;Hettiyadura et al, 2015;Szmigielski, 2016;Spolnik et al, 2018). For many of these polar oxygenated compounds, chemical structures, mass spectrometry (MS) frag-mentation patterns, and formation mechanisms have been tentatively proposed (Surratt et al, 2007a, b;Gomez-Gonzalez et al, 2008;Zhang et al, 2011;Shalamzari et al, 2013;Schindelka et al, 2013;Nguyen et al, 2014;Tao et al, 2014;Hettiyadura et al, 2015;Riva et al, 2016;Spolnik et al, 2018).…”

“…The most common isoprene organosulfates have been identified both in smog chamber experiments and in field studies (Surratt et al, 2007a(Surratt et al, , 2008Gomez-Gonzalez et al, 2008;Shalamzari et al, 2013;Tao et al, 2014;Hettiyadura et al, 2015;Szmigielski, 2016;Spolnik et al, 2018). For many of these polar oxygenated compounds, chemical structures, mass spectrometry (MS) frag-mentation patterns, and formation mechanisms have been tentatively proposed (Surratt et al, 2007a, b;Gomez-Gonzalez et al, 2008;Zhang et al, 2011;Shalamzari et al, 2013;Schindelka et al, 2013;Nguyen et al, 2014;Tao et al, 2014;Hettiyadura et al, 2015;Riva et al, 2016;Spolnik et al, 2018). The commonly detected components of isoprene SOA attributed to processing of isoprene oxidation products (e.g., IEPOX, methacrolein, and methyl vinyl ketone) have the reported molecular weights (MWs) of 154, 156, 184, 198, 200, 212, 214, 216, 260, and 334 (Surratt et al, 2007b154, 156, 184, 198, 200, 212, 214, 216, 260, and 334 (Surratt et al, , 2008154, 156, 184, 198, 200, 212, 214, 216, 260, and 334 (Surratt et al, , 2010Gomez-Gonzalez et al, 2008;Kristensen et al, 2011;Zhang et al, 2011;Shalamzari et al, 2013;Schindelka et al, 2013;Nguyen et al, 2014;Hettiyadura et al, 2015;Riva et al, 2016).…”

Responses to Referee 1

“…3.4 for the high-NO x conditions) in Beijing Hu et al, 2015). The RH in Beijing was lower than that in the southeast US , which possibly led to an increase in aerosol viscosity and a decrease in diffusivity within the particles, resulting in lower OS formation (Shiraiwa et al, 2011). Moreover, the OM-coated particle structures observed in Beijing could reduce the reactive uptake of isoprene oxidation products (Li et al, 2016;Zhang et al, 2018;Riva et al, 2016a), which may be another possible reason for lower isoprene OSs in this study.…”

“…Many prior chamber experiments revealed the precursors and formation mechanisms of OSs (Surratt et al, 2007Liggio and Li, 2006;Chan et al, 2011;Shalamzari et al, 2014Shalamzari et al, , 2016; however, the atmospheric relevance of these remain unclear. Various biogenic VOC (BVOC) precursors have been reported, including isoprene (Hatch et al, 2011;Surratt et al, 2010), monoterpenes , sesquiterpenes , pinonaldehyde (Liggio and Li, 2006), unsaturated aldehydes (Shalamzari et al, 2014(Shalamzari et al, , 2016, and 2-methyl-3-buten-2-ol . OSs originating from isoprene are some of the most studied compounds and could be among the most abundant OA in some areas (Liao et al, 2015;Chan et al, 2010;Surratt et al, 2010;Lin et al, 2013a;Worton et al, 2013).…”