Hygroscopicity of aerosol particles and CCN activity of nearly hydrophobic particles in the urban atmosphere over Japan during summer. Issue 12 (29th June 2016)

• Record Type: Journal Article
• Authors: Ogawa, Shuhei; Setoguchi, Yoshitaka; Kawana, Kaori; Nakayama, Tomoki; Ikeda, Yuka; Sawada, Yuuki; Matsumi, Yutaka; Mochida, Michihiro
• Is Part Of: Journal of geophysical research. Volume 121:Issue 12(2016)
• Page Start: 7215
• Page End: 7234
• Publication Date: 2016-06-29
• Subjects: urban aerosol -- hygroscopicity -- chemical composition -- cloud condensation nuclei -- organic aerosol; Atmospheric physics -- Periodicals; Geophysics -- Periodicals; 551.5
• DOI: 10.1002/2015JD024636
• Languages: English
• ISSNs: 2169-897X

Abstract

Abstract: We investigated the hygroscopicity of 150 nm particles and the number‐size distributions and the cloud condensation nuclei (CCN) activity of nearly hydrophobic particles in aerosols over Nagoya, Japan, during summer. We analyzed the correlations between the number concentrations of particles in specific hygroscopic growth factor ( g ) ranges and the mass concentrations of chemical components. This analysis suggests the association of nearly hydrophobic particles with hydrocarbon‐like organic aerosol, elemental carbon and semivolatile oxygenated organic aerosol (SV‐OOA), that of less hygroscopic particles with SV‐OOA and nitrate and that of more hygroscopic particles with low‐volatile oxygenated organic aerosol (LV‐OOA) and sulfate. The hygroscopicity parameter ( κ ) of organics was derived based on the g distributions and chemical composition of 150 nm particles. The κ of the organics correlated positively with the fraction of the total organic mass spectral signal at m / z 44 and the volume fraction of the LV‐OOA to the organics, indicating that organics with highly oxygenated structures including carboxylic acid groups contribute to the water uptake. The number‐size distributions of the nearly hydrophobic particles with g around 1.0 and 1.1 correlated with the mass concentrations of chemical components. The results show that the chemical composition of the particles with g around 1.0 was different between the Aitken mode and the accumulation mode size ranges. An analysis for a parameter F max of the curves fitted to the CCN efficiency spectra of the particles with g around 1.0 suggests that the coating by organics associated with SV‐OOA elevated the CCN activity of these particles. Key Points: The relationship between hygroscopicity and composition was investigated The size distributions and CCN activity of nearly hydrophobic particles were investigated The amount of organics controls the CCN activity of the nearly hydrophobic particles