Evaluation of the atmospheric significance of multiphase reactions in atmospheric secondary organic aerosol formation

Abstract

Abstract. In a simple conceptual cloud-aerosol model the mass of secondary organic aerosol (SOA) that may be formed in multiphase reaction in an idealized scenario involving two cloud cycles separated with a cloud-free period is evaluated. The conditions are set to those typical of continental clouds, and each parameter used in the model calculations is selected as a mean of available observational data of individual species for which the multiphase SOA formation route has been established. In the idealized setting gas and aqueous-phase reactions are both considered, but only the latter is expected to yield products of sufficiently low volatility to be retained by aerosol particles after the cloud dissipates. The key variable of the model is the Henry-constant which primarily determines how important multiphase reactions are relative to gas-phase photooxidation processes. The precursor considered in the model is assumed to already have some affinity to water, i.e. it is a compound having oxygen-containing functional group(s). As a principal model output an aerosol yield parameter is calculated for the multiphase SOA formation route as a function of the Henry-constant, and has been found to be significant already above H~103 M atm-1. Among the potential precursors that may be eligible for this mechanism based on their Henry constants, there are a suite of oxygenated compounds such as primary oxidation products of biogenic and anthropogenic hydrocarbons, including, for example, pinonaldehyde. Finally, the analogy of multiphase SOA formation to in-cloud sulfate production is exploited.

Kinetics and Products of Gas-Phase Reactions of Ozone with Methyl Methacrylate, Methyl Acrylate, and Ethyl Acrylate

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

“…Models that accurately link emissions to air pollution concentrations and effects are important to developing effective air quality management plans and understanding to what degree SOA is controllable . SOA is formed from gas-phase chemistry, followed by either vapor pressure-based partitioning into particulate organic matter-SOA OM (Odum et al 1996;Seinfeld and Pankow 2003;Hallquist et al 2009) or aqueous-phase chemistry in clouds and wet aerosols-SOA aq (Blando and Turpin 2000;Gelencsér and Varga 2005;Ervens et al 2011). Several papers report comparable amounts of SOA OM and SOA aq globally and in certain regions, although uncertainties are large (Chen et al 2007;Carlton et al 2008;Fu et al 2008Fu et al , 2009Gong et al 2011).…”

In-cloud oxalate formation in the global troposphere: a 3-D modeling study

“…Aqueous-phase chemistry provides a complementary pathway for SOA formation to non-aqueous gas-particle partitioning ("traditional" description of SOA) and has the potential to enhance OA concentrations in the atmosphere and particularly in the free troposphere (Blando and Turpin, 2000;Gelencser and Varga, 2005;Sorooshian et al, 2007;Ervens et al, 2008). During SOA formation in the gas-phase, the precursors are mostly high molecular weight (MW) molecules (>C 7 ) able to produce semi-volatile compounds.…”