title: Chemical closure study on hygroscopic properties of urban aerosol particles in Sapporo, Japan.
abstract: To assess the link between hygroscopicity of atmospheric particles and the chemical composition, we performed a chemical closure study on the hygroscopicity of organic-inorganic mixed particles nebulized from water extracts of ambient aerosols collected in Sapporo, Japan during summer 2005. The hygroscopicity of 100 nm particles was measured using a hygroscopicity tandem differential mobility analyzer (HTDMA) at 5-95% relative humidity. The chemical analyses of the extracts showed that inorganic salts accounted for 32-84% of the water-soluble fraction and that the remaining was water-soluble organic matter (WSOM). The liquid water content (LWC) of particles was primarily governed by the relative abundance of inorganic salts in particles. The chemical closure with a thermodynamic model did not indicate a significant perturbation of LWC by WSOM at 85% RH with the consideration of the uncertainties estimated. However, a positive perturbation by WSOM was suggested at 50% RH. Individual oxygenated compounds identified using gas chromatography were not abundant enough to substantially increase the LWC at 85% RH.
authors.affiliation: Institute of Low Temperature Science, Hokkaido University, Kita 19, Nishi 8, Kita-ku, Sapporo 060-0819, Japan. aggarwal@pop.lowtem.hokudai.ac.jp
authors.forename: Shankar Gopala
authors.initials: SG
authors.lastname: Aggarwal
authors.forename: Michihiro
authors.initials: M
authors.lastname: Mochida
authors.forename: Yasuyuki
authors.initials: Y
authors.lastname: Kitamori
authors.forename: Kimitaka
authors.initials: K
authors.lastname: Kawamura
mesh_terms: D000336:Aerosols / Q000032:analysis*; D000393:Air Pollutants / Q000032:analysis*; D007564:Japan; D014504:Urban Health; D014867:Water / Q000737:chemistry
chemical_list: D000336:Aerosols; D000393:Air Pollutants; D014867:Water