THERMODYNAMIC AND OPTICAL-PROPERTIES OF MIXED-SALT AEROSOLS OF ATMOSPHERIC IMPORTANCE

Extensive water activity, density, and refractive index data at 25 deg rees C are reported for mixed-salt solutions, NaCl-KCl, NaCl-NaNO3, Na Cl-Na2SO4, Na2SO4-NaNO3, and (NH4)(2)SO4-Na2SO(4) The data are obtaine d from hydration experiments using the single-particle levitation tech nique developed recently for measuring the thermodynamic and optical p roperties of microdroplets. These data, covering the whole concentrati on range from dilute solutions to high supersaturations, provide an op portunity to explore the light-scattering properties of both internal and external mixtures of the chloride, sulfate, and nitrate aerosols o f atmospheric importance. It is shown that for sulfate and nitrate aer osols as solution droplets, the light-scattering properties do not dif fer appreciably among all mixture types and compositions, as long as t he dry-salt aerosols have the same particle-size distribution. However , for mixed-salt aerosols containing NaCl, the light-scattering proper ties do depend upon the composition and particle-size distribution, al though not so much on the mixture type.