| The purpose of this laboratory research program is to investigate the fundamental properties and processes of atmospheric aerosol. The research uses the low temperature single particle levitation system developed at Brookhaven National Laboratory specifically for this purpose. This apparatus allows investigations of isolated particles over a wide range of temperatures and gas phase compositions, thus providing information about the composition and phase transformations of important atmospheric aerosols. In this thesis, I will present the first laboratory observations of isolated individual H2SO4/H 2O, NH4HSO4/H2O and (NH4) 2SO4/H2O particles over a broad temperature range. The data observed from deliquescence and efflorescence transitions were used to derive the NH4HSO4/H2O, and (NH4 )2SO4/H2O equilibrium and metastability phase diagrams as functions of pressure, temperature, and composition. New crystalline phases H2SO4·8H2O, NH 4HSO4·8H2O, and (NH4)2 SO4·4H2O were discovered. A complete phase diagram in temperature/composition, as well as the vapor-pressure/temperature domains is shown here for the first time. |
