Volatility and Yield of Glycolaldehyde SOA Formed through Aqueous Photochemistry and Droplet Evaporation

Abstract

Aqueous hydroxyl radical (∼10 −12 M) oxidation of glycolaldehyde (1 mM), followed by droplet evaporation, forms secondary organic aerosol (SOA) that exhibits an effective liquid vapor pressure and enthalpy of vaporization of ∼10 −7 atm and ∼70 kJ/mol, respectively, similar to the mix of organic acids identified in reaction samples. Salts of these acids have vapor pressures about three orders of magnitude lower (e.g., ammonium succinate ∼10 −11 atm), suggesting that the gas-particle partitioning behavior of glycolaldehyde SOA depends strongly on whether products are present in the atmosphere as acids or salts. Several reaction samples were used to simulate cloud droplet evaporation using a vibrating orifice aerosol generator. Samples were also analyzed by ion chromatography (IC), electrospray ionization mass spectrometry (ESI-MS), IC-ESI-MS, and for total carbon. Glycolaldehyde SOA mass yields were 50-120%, somewhat higher than yields reported previously (40-60%). Possible reasons are discussed: (1) formation of oligomers from droplet evaporation, (2) inclusion of unquantified products formed by aqueous photooxidation, (3) differences in gas-particle partitioning, and (4) water retention in dried particles. These and similar results help to explain the enrichment of organic acids in particulate organic matter above clouds compared with those found below clouds, as observed previously in aircraft campaigns.

Inorganic salts interact with oxalic acid in submicron particles to form material with low hygroscopicity and volatility

“…The formation of organic salts is also a reactive sink of particle-phase organics, enhancing gas phase uptake (Pierce et al, 2011). Recently, the formation of low-volatility organic salts has been observed under various atmospheric conditions in reactions of organic acids with mineral salts (Laskin et al, 2012), ammonium (Martinelango et al, 2007;Dinar et al, 2008;Ortiz-Montalvo et al, 2012) and amines (Sorooshian et al, 2008;Smith et al, 2010).…”

Structure–activity relationship for the estimation of OH-oxidation rate constants of carbonyl compounds in the aqueous phase

“…SOA in the atmosphere, especially in the presence of water (Loeffler et al 2006;Altieri et al, 2006;Carlton et al, 2007;Volkamer et al, 2009;Perri et al, 2009;Ervens and Volkamer, 2010;Tan et al, 2010;Lee et al, 2012;Ervens et al, 2011;Liu et al, 2012;Ortiz-Montalvo et al 2012). The oligomeric condensation processes of carbonyl compounds in the atmosphere are only partially understood, and a large effort currently concentrates on the determination of the oligomerization mechanisms.…”

The effects of isoprene and NO<sub><i>x</i></sub> on secondary organic aerosols formed through reversible and irreversible uptake to aerosol water

“…During the summer, model predictions suggest that glyoxal production from isoprene occurs almost equally through low-and high-NO x pathways in the eastern USA (Chan Miller et al, 2017). Glyoxal is taken up to ALW reversibly and irreversibly (Ortiz-Montalvo et al, 2012;Galloway et al, 2009). IEPOX is formed predominantly through the low-NO x pathway (Paulot et al, 2009;Surratt et al, 2010), and its uptake to ALW could be reversible or irreversible (Nguyen et al, 2014;Riedel et al, 2015).…”