AEROSOL PHASE-TRANSFORMATION AND GROWTH IN THE ATMOSPHERE

The dynamic behavior of hygroscopic multicomponent aerosols under the influence of changing relative humidity in the atmosphere is investiga ted. Laboratory measurements of the deliquescence humidity as a functi on of temperature between 5-degrees and 35-degrees-C are carried out w ith single aerosol particles individually suspended in an electrodynam ic cell. The single-particle levitation cell is placed in a vacuum cha mber that can be evacuated and backfilled with water vapor. The phase transformation of the aerosol particle is monitored by laser light sca ttering, and the relative humidity at the transition point is determin ed by directly measuring the water vapor pressure in the cell. Results am obtained for aerosol particles composed of binary mixtures of NaCl , KCl, NaNO3, Na2SO4, and (NH4)2SO4, which am common constituents of a mbient aerosols. The measured temperature and composition dependence o f the deliquescence properties agrees well with a theoretical model ba sed on thermodynamic considerations. A study of aerosol particles cont aining more than two inorganic salts shows that the system is too comp lex for the present theoretical analysis. Further work is needed in or der to elucidate and predict the complex nature of multicomponent aero sols.