Glyoxal processing by aerosol multiphase chemistry: towards a kinetic modeling framework of secondary organic aerosol formation in aqueous particles

Abstract

Abstract. This study presents a modeling framework based on laboratory data to describe the kinetics of glyoxal reactions that form secondary organic aerosol (SOA) in aqueous aerosol particles. Recent laboratory results on glyoxal reactions are reviewed and a consistent set of empirical reaction rate constants is derived that captures the kinetics of glyoxal hydration and subsequent reversible and irreversible reactions in aqueous inorganic and water-soluble organic aerosol seeds. Products of these processes include (a) oligomers, (b) nitrogen-containing products, (c) photochemical oxidation products with high molecular weight. These additional aqueous phase processes enhance the SOA formation rate in particles and yield two to three orders of magnitude more SOA than predicted based on reaction schemes for dilute aqueous phase (cloud) chemistry for the same conditions (liquid water content, particle size).The application of the new module including detailed chemical processes in a box model demonstrates that both the time scale to reach aqueous phase equilibria and the choice of rate constants of irreversible reactions have a pronounced effect on the predicted atmospheric relevance of SOA formation from glyoxal. During day time, a photochemical (most likely radical-initiated) process is the major SOA formation pathway forming ∼5 µg m −3 SOA over 12 h (assuming a constant glyoxal mixing ratio of 300 ppt). During night time, reactions of nitrogen-containing compounds (ammonium, amines, amino acids) contribute most to the predicted SOA mass; however, the absolute predicted SOA masses are Correspondence to: B. Ervens (barbara.ervens@noaa.gov) R. Volkamer (rainer.volkamer@colorado.edu) reduced by an order of magnitude as compared to day time production. The contribution of the ammonium reaction significantly increases in moderately acidic or neutral particles (5 < pH < 7).Glyoxal uptake into ammonium sulfate seed under dark conditions can be represented with a single reaction parameter k effupt that does not depend on aerosol loading or water content, which indicates a possibly catalytic role of aerosol water in SOA formation. However, the reversible nature of uptake under dark conditions is not captured by k effupt , and can be parameterized by an effective Henry's law constant including an equilibrium constant K olig = 1000 (in ammonium sulfate solution). Such reversible glyoxal oligomerization contributes <1% to total predicted SOA masses at any time.Sensitivity tests reveal five parameters that strongly affect the predicted SOA mass from glyoxal: (1) time scales to reach equilibrium states (as opposed to assuming instantaneous equilibrium), (2) particle pH, (3) chemical composition of the bulk aerosol, (4) particle surface composition, and (5) particle liquid water content that is mostly determined by the amount and hygroscopicity of aerosol mass and to a lesser extent by the ambient relative humidity.Glyoxal serves as an example molecule, and the conclusions about SOA formation in aqueous particles can serve for...

Diurnal and temporal variations of water-soluble dicarboxylic acids and related compounds in aerosols from the northern vicinity of Beijing: Implication for photochemical aging during atmospheric transport

“…Hence, the ratios of C 2 /total diacids could be enhanced in nighttime. These results suggest that C 2 is partly produced via the oxidation of ωC 2 , which may be derived from MeGly and Gly (Ervens and Volkamer, 2010). Oxidation of biogenic VOCs (e.g., isoprene) emitted from the forest areas in the north during daytime produces α-dicarbonyls, which may be transported to the Mangshan site in nighttime, and finally oxidized to ωC 2 and then C 2 in aqueous phase as discussed above.…”

Ship-based detection of glyoxal over the remote tropical Pacific Ocean

“…With a typical deposition velocity of 3-4 cm/s, the CHOCHO loss to the ocean surface can add 20 to 30% to the daytime loss rate from photolysis and OH reaction; dry deposition is relatively more important at night. Also, CHOCHO uptake by aerosols to form SOA can compete with rapid gas-phase losses and will further lower the atmospheric lifetime of CHOCHO Fu et al, 2008;Stavrakou et al, 2009;Ervens and Volkamer, 2010). The CHOCHO life time in the tropical Pacific Ocean is thus shorter than the global mean life time of CHOCHO (2.5 to 3 h; Myriokefalitakis et al, 2008;Fu et al, 2008;Stavrakou et al, 2009), and about comparable to that in urban photochemical hot-spots (Volkamer et al, 2005a.…”

Glyoxal vertical columns from GOME-2 backscattered light measurements and comparisons with a global model

“…Further interest in glyoxal originates from its recognized potential for formation of secondary organic aerosols (SOA, Fu et al (2008), Stavrakou et al (2009b), Ervens and Volkamer (2010) and references therein). Glyoxal is expected to be one of the missing links necessary to bridge the gap between observed and modelled organic carbon concentrations.…”