AGS-PRF: Experimentally Determined Volatility of Secondary Organic Aerosol Formed Through Aqueous Oxidation

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Secondary organic aerosols (SOA) are small particles produced by the oxidation of organic gases emitted by forests, fossil fuel combustion and fires. Complex chemical processes that are not well represented in climate models and are a source of large uncertainties in climate assessments produce sOAs. In particular the oxidation of organic gases by water in cloud drops is recognized to be important but there are limited studies to represent the processes that produce the particles and their properties. The proposed work will measure and quantify the persistence of these aqueous SOA particles by measuring their volatility in the laboratory and their inclusion in climate models will enable more robust assessments. In order to constrain aqueous SOA (aqSOA) production mechanism this research would experimentally quantify the volatility of aqSOA compounds that determine the low volatility fraction that survive evaporation and scavenging to effect global climate. The goal is to probe the fundamental relationship between the precursor molecular properties and aqSOA volatility. The laboratory studies will elucidate aqSOA-volatility relationships from (1) methylglyoxal, pyruvic acid, and methyl-vinyl ketone oxidation, (2) oxidation products in precipitation samples and (3) dried organic aerosol oxidation. The oxidation will be performed by hydroxyl radicals produced from hydrogen peroxide photolysis in a batch reactor, the mixtures will be aerosolized with a vibration orifice aerosol generator then evaporated in a flow tube and finally detected by an optical particle counter. Polarity-resolved volatility distributions will be measured using elution and ion chromatography. The results will elucidate the fundamental volatility properties of aqSOA to understand how they effect past, present and future climate.