Title: The Connection between Microphysical Morphology and Atmospheric Particle Phase Transitions
Description: The phase of atmospheric particles can influence heterogeneous chemistry, cloud formation, and radiative forcing. Sulfate particles ranging from sulfuric acid to ammonium sulfate are the largest contributor arising from anthropogenic activities to the global fine aerosol burden. Multi-component inorganic particles of neutralized or partially neutralized crystalline components and acidic solutions can form via uptake of gaseous ammonia. Under some atmospheric conditions, secondary organic material can combine with sulfate species to form internally mixed organic-sulfate particles. The way in which interactions between the constituents in ambient multi-component particles affect the phase of the overall particle are not well understood, especially for complex mixtures containing secondary organic material. This thesis presents measurements of relative humidity-dependent phase transitions of atmospherically relevant multi-component particles, measured using tandem differential mobility analyzer (TDMA) setups. Particle morphologies implied by these measurements and their impact on other atmospheric processes are discussed.