Glyoxal Induced Atmospheric Photosensitized Chemistry Leading to Organic Aerosol Growth

Abstract

In recent years, it has been proposed that gas phase glyoxal could significantly contribute to ambient organic aerosol (OA) mass through multiphase chemistry. Of particular interest is the reaction between glyoxal and ammonium cations producing light-absorbing compounds such as imidazole derivatives. It was recently shown that imidazole-2-carboxaldehyde (IC) can act as a photosensitizer, initiating aerosol growth in the presence of gaseous volatile organic compounds. Given the potential importance of this new photosensitized growth pathway for ambient OA, the related reaction mechanism was investigated at a molecular level. Bulk and flow tube experiments were performed to identify major products of the reaction of limonene with the triplet state of IC by direct (±)ESI-HRMS and UPLC/(±)HESI-HRMS analysis. Detection of recombination products of IC with limonene or with itself, in bulk and flow tube experiments, showed that IC is able to initiate a radical chemistry in the aerosol phase under realistic irradiation conditions. Furthermore, highly oxygenated limonene reaction products were detected, clearly explaining the observed OA growth. The chemistry of peroxy radicals derived from limonene upon addition of oxygen explains the formation of such low-volatile compounds without any traditional gas phase oxidant.

Secondary brown carbon formation via the dicarbonyl imine pathway: nitrogen heterocycle formation and synergistic effects

“…38 Moreover, we have observed synergistic cross-reactions between different dicarbonyls in amine containing solutions. This gives rise to photodegradation (photobleaching), but also to photosensitization reactions.…”

“…16,17,[19][20][21][22][23][24][25][26][27][28][29][30][31][32][33][34][35][36] Recent modeling studies suggest that BrC could contribute significantly or sometimes dominate overall aerosol absorption at specific wavelengths. 38 The formation of light-absorbing products from (di-)carbonyl + ammonia or amino acid reactions have received increasing attention over the past years. 38 The formation of light-absorbing products from (di-)carbonyl + ammonia or amino acid reactions have received increasing attention over the past years.…”

“…17,22,28,51 The change in absorption properties was attributed to the formation of light-absorbing species from the reactions of ammonia and specific carbonyl intermediates of the VOC oxidation reactions, e.g., ketolimononaldehyde, while other carbonyl intermediates, e.g., pinonaldehyde (a first generation oxidation product of a-pinene) or limononaldehyde (a first generation oxidation product of limonene) did not form BrC. 38 In this study, we focus on the investigation of chemical mechanisms and identification of light-absorbing products in secondary BrC formation. 52 Further, BrC chromophores are subject to photo-bleaching upon irradiation, with atmospheric lifetimes of minutes to a few hours.…”

Aerosols in atmospheric chemistry and biogeochemical cycles of nutrients

“…Atmospheric reactions of inorganic nitrogen (nitrogen oxides and ammonia) with organic compounds in the gas and the aqueous/aerosol phases can lead to the formation of organic nitrogen compounds and subsequent transfer of inorganic nitrogen to the aerosol phase (Atkinson andArey 2003, Ervens andVolkamer 2010). Recent laboratory investigations have shown that photosensitizers can initiate aerosol growth in the presence of gaseous volatile organic compounds, in particular the imidazole derivatives, like imidazole-2 carboxaldehyde, that are formed by reaction of glyoxal with ammonium cations (Rossignol et al 2014). Dark reactions including acid-catalyzed aerosol chemistry of hydronium or ammonium ions, which protonate epoxide and carbonyl groups thus enabling attack by nucleophiles such as water, SO 4 2− , NH 3 and NO 3 − , may be responsible for the ring opening mechanism of epoxides, organosulfate formation by epoxides and carbonyls and C-N-containing lightabsorbing organic species as part of the 'brown carbon' pool (Surratt et al 2010, McNeill 2015, Laskin et al 2015.…”

Model Analysis of Secondary Organic Aerosol Formation by Glyoxal in Laboratory Studies: The Case for Photoenhanced Chemistry

“…20 Allowing for differences in H* due to varying seed aerosol conditions, we find it necessary to invoke newly proposed mechanisms for SOA formation involving photosensitizer chemistry 16,17,21 in order to achieve closure with the irradiated experiments, particularly when fulvic acid is present in the seed aerosol.…”