A modeling study of aqueous production of dicarboxylic acids: 1. Chemical pathways and speciated organic mass production

Abstract

While the formation pathways and thermodynamic properties of inorganic species (e.g., sulphate) in atmospheric aerosols are well understood, many more uncertainties exist about organics. In the present study we present oxidation pathways of organic gas phase species that lead to low volatility organic compounds (C2‐C6 dicarboxylic acids, pyruvic acid) in both the aqueous and gas phases. This mechanism is implemented in a cloud parcel model initialized with pure (NH4)2SO4 particles in 10 discrete sizes. Under clean continental conditions a few cloud processing cycles produce a total organic mass addition of ∼150 ng m−3. Individual resuspended aerosol size classes contain significant organic fractions, sometimes higher than 50%. These are likely upper bound estimates of organic mass production. In a polluted, i.e., SO2‐rich scenario, about 400 ng m−3 organic material is produced after about eight cloud cycles. Since the initial conditions in this latter case favor significant production of sulphate, the organic fraction of the aerosol mass after cloud processing represents a much lower percentage of the total aerosol mass. Oxalic, glutaric, adipic, and pyruvic acids are the main contributors to the organic fraction in both cases. In agreement with observations, the oxalate fraction in processed particles exceeds the fractions of other dicarboxylic acids since it represents an end product in the oxidation of several organic gas phase species. The study suggests that cloud processing may act as a significant source of small dicarboxylic acids, some fraction of which can be retained in the aerosol phase upon drop evaporation.

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

“…60±70 ng m -3 ) at night. Glyoxal (Gly) and methylglyoxal (MeGly) are produced by gaseous-phase oxidation from various VOCs including ethylene (Ervens et al, 2004), and toluene, benzene, xylene (Volkamer et al, 2001) as well as terpenes (Fick et al, 2004) and isoprene (Zimmermann and Poppe, 1996). Interestingly, Gly showed higher concentrations in daytime whereas MeGly is more abundant in nighttime (Table 2).…”

Contribution of Selected Dicarboxylic and ω-Oxocarboxylic Acids in Ambient Aerosol to them/z44 Signal of an Aerodyne Aerosol Mass Spectrometer

“…Kawamura and Ikushima (1993) suggested that oxidation of volatile organic compounds (VOCs) is the major source of low molecular weight (C 2 -C 6 ) diacids observed at an urban site in Tokyo, based on the seasonal variation of these diacids. More recently, Ervens et al (2004) proposed that cloud processing could be an important source of low molecular weight diacids, although there are still many uncertainties in the production pathway of these compounds.…”

Aerosol formation and heterogeneous chemistry in the atmosphere

“…Clouds and aqueous aerosols provide an efficient medium for liquid phase reactions of water soluble species: more than 60% of the total sulfate on a global scale is estimated to be produced from aqueous phase oxidation of SO 2 (Kanakidou et al, 2005). Recent studies suggest that, as sulfate, SOA can also be produced through aqueous phase reactions in clouds, fogs and aerosol water (Blando and Turpin 2000;Ervens et al 2003;Ervens et al 2004a;Ervens et al 2004b;Ervens et al 2008;Gelencsér and Varga 2005;Lim et al 2005;Altieri et al 2006;Altieri et al 2008;Carlton et al 2006;Carlton et al 2007;Poulain et al, 2007;Liu et al, 2009;El Haddad et al 2009;Poulain et al 2010). Briefly, reactive organics are oxidized in the interstitial spaces of clouds to form highly water-soluble compounds (e.g.…”