In Situ Surface Tension Measurement of Deliquesced Aerosol Particles

Masao Gen; Akihide Hibara; Phuong Nguyet Phung; Yuzo Miyazaki; Michihiro Mochida

doi:10.1021/acs.jpca.3c02681

In Situ Surface Tension Measurement of Deliquesced Aerosol Particles

J Phys Chem A. 2023 Jul 27;127(29):6100-6108. doi: 10.1021/acs.jpca.3c02681. Epub 2023 Jul 18.

Authors

Masao Gen¹, Akihide Hibara^{1

2}, Phuong Nguyet Phung³, Yuzo Miyazaki⁴, Michihiro Mochida^{3

5}

Affiliations

¹ Institute of Multidisciplinary Research for Advanced Materials, Tohoku University, Sendai 980-8577, Japan.
² Department of Chemistry, School of Science, Tokyo Institute of Technology, 2-12-1-W4-19 Ookayama, Meguro-ku, Tokyo 152-8550, Japan.
³ Graduate School of Environmental Studies, Nagoya University, Nagoya 464-8601, Japan.
⁴ Institute of Low Temperature Science, Hokkaido University, Sapporo 060-0819, Japan.
⁵ Institute for Space-Earth Environmental Research, Nagoya University, Nagoya 464-8601, Japan.

PMID: 37462410
DOI: 10.1021/acs.jpca.3c02681

Abstract

The surface tension of aerosol particles can potentially affect cloud droplet activation. Hence, direct measurement of the surface tensions of deliquesced aerosol particles is essential but is challenging. Here, we report in situ surface tension measurements based on a novel method that couples a linear quadrupole electrodynamic balance (EDB) with quasi-elastic light scattering (QELS). The EDB-QELS is validated using surface tension measurements of atmospherically relevant inorganic and organic droplets. The surface tension results reasonably agree with the reference values in the range of ∼50-90 mN m^-1. We find a significant size dependence for sodium chloride droplets containing surface-active species (sodium dodecyl sulfate) in the size range of ∼5-18 μm. The surface tension increases from ∼55 to 80 mN m^-1 with decreased size. Relative humidity (RH)-dependent surface tensions of mixed ammonium sulfate (AS) and polyethylene glycol droplets reveal the onset of liquid-liquid phase separation. Droplets containing water-soluble matter extracted from ambient aerosol samples and 2.3-2.9 M AS exhibit a ∼30% reduction in surface tension in the presence of ∼50 mmol-C L^-1 water-soluble organic carbon, compared to pure water (∼72 mN m^-1). The approach can offer size-resolved and RH-dependent surface tension measurements of deliquesced aerosol particles.