title: Gas-particle partitioning of atmospheric aerosols: interplay of physical state, non-ideal mixing and morphology.
abstract: Atmospheric aerosols, comprising organic compounds and inorganic salts, play a key role in air quality and climate. Mounting evidence exists that these particles frequently exhibit phase separation into predominantly organic and aqueous electrolyte-rich phases. As well, the presence of amorphous semi-solid or glassy particle phases has been established. Using the canonical system of ammonium sulfate mixed with organics from the ozone oxidation of α-pinene, we illustrate theoretically the interplay of physical state, non-ideality, and particle morphology affecting aerosol mass concentration and the characteristic timescale of gas-particle mass transfer. Phase separation can significantly affect overall particle mass and chemical composition. Semi-solid or glassy phases can kinetically inhibit the partitioning of semivolatile components and hygroscopic growth, in contrast to the traditional assumption that organic compounds exist in quasi-instantaneous gas-particle equilibrium. These effects have significant implications for the interpretation of laboratory data and the development of improved atmospheric air quality and climate models.
authors.affiliation: Division of Chemistry and Chemical Engineering, California Institute of Technology, Pasadena, CA 91125, USA.
authors.forename: Manabu
authors.initials: M
authors.lastname: Shiraiwa
authors.forename: Andreas
authors.initials: A
authors.lastname: Zuend
authors.forename: Allan K
authors.initials: AK
authors.lastname: Bertram
authors.forename: John H
authors.initials: JH
authors.lastname: Seinfeld
mesh_terms: D000336:Aerosols / Q000737:chemistry*; D001272:Atmosphere / Q000737:chemistry*; D005740:Gases / Q000737:chemistry*; D015394:Molecular Structure
chemical_list: D000336:Aerosols; D005740:Gases