Secondary organic aerosol (SOA) is a ubiquitous component of submicron ambient aerosol, but its formation mechanisms and the connection between chemical composition and physical properties are not well understood. In recent years, aerosol phase has been shown to range from to solid to semi-solid to liquid for ambient particles, Morphology (e.g. core-shell) of SOA with inorganic components (e.g. ammonium sulfate) have shown morphologies ranging from well-mixed liquid particles to core shell or more complex morphologies as a function of relative humidity (RH) and temperature. The changing water content of aerosols can impact acidity and reactive uptake of molecules such as isoprene epoxydiols (IEPOX). However, direct evidence of the impact of non-liquid phases and phase separation on heterogeneous uptake and continuing chemistry in aerosols is far more limited. Herein, we use atomic force microscopy (AFM) with phase images and photothermal infrared spectroscopy (AFM-PTIR), electron microscopy, and Raman microspectroscopy to probe phase, structure, and acidity of mixed SOA and ammonium sulfate particles in controlled laboratory studies (flow tube and chamber) and field measurements. Decreased uptake of IEPOX and conversion of inorganic to organic sulfate lead to important modifications of aerosol physicochemical properties and has large implications for aerosol impacts on air quality and climate.<br/> <br/>

Modification of aerosol phase, acidity, and structure by heterogeneous and multiphase chemistry

2019 Fall National Meeting

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