Formation of highly oxygenated multifunctional compounds from cross-reactions of carbonyl compounds in the atmospheric aqueous phase

Abstract

There is increasing evidence that aqueous-phase atmospheric chemistry is an important source of secondary organic aerosols (SOA), but this chemistry is currently not adequately represented in atmospheric models due to the missing information on most products. The main focus of this study is to provide molecular-level insight into the photosensitized reaction mechanism of pyruvic acid (PA) alone in the atmospheric aqueous phase, and of mixtures of PA with glyoxal (GL), a typical and widely occurring carbonyl compound. With two ultrahigh resolution mass spectrometers, Orbitrap and FT-ICR-MS, a broad and complex spectrum of organic products were unambiguously identified. The detected formation of oligomers illustrates the progression from C 3 to C 20 molecules through direct PA photolysis and irradiation of PA + GL. The performed ab-initio calculations indicate that cross-reactions (i.e., PA + GL) are more likely than self-reactions (i.e., PA alone) in clouds and aerosol deliquescent particles. Hence, this result implies that photosensitizers like PA can initiate the transformation of common organic cloud constituents like GL into oligomers. These oligomeric products that are formed in significant amount could potentially impact optical and cloud-forming properties of aerosols, especially if they partition to the aerosol surface.

Formation of Toxic Unsaturated Multifunctional and Organosulfur Compounds From the Photosensitized Processing of Fluorene and DMSO at the Air‐Water Interface

“…Most of the C c H h O o liquid phase products formed upon photosensitized interfacial chemistry of FL exhibit DBE values in the range between 2 and 6, with 7 to 20 carbon atoms and 5 to 8 oxygen atoms (circled in Figure ). These high molecular weight organic compounds contain two to six carbonyl groups with several oxygen‐containing moieties like hydroxyl or carboxyl, depending on the occurrence of different oxygen atoms (Mekic et al, ; Mekic et al, ; Vione et al, ). The C c H h O o with the same DBE values but different carbon numbers are considered as homologs differing from each other by a repeating mass increment (Jiang et al, ).…”

Molecular composition and photochemical evolution of water-soluble organic carbon (WSOC) extracted from field biomass burning aerosols using high-resolution mass spectrometry

“…C 18 H 14 O 3 and C 24 H 18 O 4 for phenol trimer and tetramer, C 21 H 20 O 6 for guaiacol trimer), as well as their hydroxylated species were observed. The formation mechanism can be ascribed to C-O or C-C coupling of phenoxy radicals that were formed via H abstraction of the phenols or OH addition to the aromatic ring (Net et al, 2009;Sun et al, 2010). The reaction at the para position or para-para coupling was more likely to occur due to a higher probability of free electrons to occur in this position (Lavi et al, 2017) or a weaker steric hindrance in the para position.…”

“…Although the direct photolysis was performed on present WSOC extracts from WSBA samples in the presence of simulated sunlight irradiation without adding any oxidants, the photooxidation process still occurred since the particle extracts were very likely to include various oxidants, e.g. singlet molecular oxygen ( 1 O 2 ), peroxides, hydroxyl radical (OH), or an excited triplet state of organics produced under light excitation (Anastasio et al, 1997;Vione et al, 2006;Net et al, 2009Net et al, , 2010aBateman et al, 2011;Rossignol et al, 2014;Gómez Alvarez et al, 2012). In particular, the excited triplet state of aromatic carbonyls (e.g.…”

“…glyoxal (Carlton et al, 2007;Lim et al, 2010), methylglyoxal (Altieri et al, 2008;Lim et al, 2010), pyruvic acid (e.g. Grgic et al, 2010;Griffith et al, 2013;Reed Harris et al, 2014;Rapf et al, 2017;Eugene and Guzman, 2017;Mekic et al, 2018Mekic et al, , 2019, and phenols (Sun et al, 2010). The presence of these highly oxygenated compounds that possibly contain acidic groups (e.g.…”

Acidity and the multiphase chemistry of atmospheric aqueous particles and clouds

“…show substantial deviations from this theory (see Nah et al (2018)) for instance because of the formation of organic salts which can increase their particle partitioning by two orders of magnitude (Meng et al, 2007). In practice, weak acid anions are often measured in non-negligible fractions in the particle phase (Tanner and Law, 2003;Limbeck et al, 2005;van Pinxteren and Herrmann, 2007;Bao et al, 2012;Nah et al, 2018;Teich et al, 2019).…”