Phase, morphology, hygroscopicity and oxidative aging of mixed organic/inorganic aerosol particles

B J Dennis-Smither, R E H Miles, N-O A Kwamena & J P Reid

Aerosol optical tweezers are used to investigate the phase, morphology and hygroscopicity of single mixed inorganic/organic aerosol particles formed of sodium chloride (NaCl) and a water-insoluble unsaturated fatty acid, oleic acid (OL), over a range of relative humidities from less than 5 % to greater than 95 %. Additionally, changes in the composition and properties of the particles due to oxidative aging have been investigated by exposing particles to ozone. The structure, size, and composition of the single aerosol particles are probed by a combination of brightfield microscopy and cavity-enhanced Raman spectroscopy. Aqueous NaCl/OL particles form a phase-separated structure consisting of two partially engulfing liquid phases and the hygroscopicity of both the inorganic and organic components have been measured. During oxidative aging loss of OL by reaction with ozone is observed, as are changes in particle size due to evaporation of volatile products, changes in refractive index, and an increase in the hygroscopicity of the organic phase.

Join today to view and download the full abstract/presentation