Maho Nakagawa1,2, Tomoki Nakayama This email address is being protected from spambots. You need JavaScript enabled to view it.1,3, Hiroshi Sasago1, Yuki Kuruma1,4, Hikari Yai5, Shuhei Ogawa5, Yange Deng5,6, Michihiro Mochida1,5, Yutaka Matsumi1

1 Institute for Space-Earth Environmental Research, Nagoya University, Chikusa-ku, Nagoya 464-8601, Japan
2 National Institute of Information and Communications Technology, Koganei, Tokyo 184-8795, Japan
3 Faculty of Environmental Science and Graduate School of Fisheries and Environmental Sciences, Nagasaki University, Bunkyo-machi, Nagasaki 852-8521, Japan
4 National Institute of Advanced Industrial Science and Technology, Umezono, Tsukuba 305-8560, Japan
5 Graduate School of Environmental Studies, Nagoya University, Chikusa-ku, Nagoya 464-8601, Japan
6 National Institute for Environmental Studies, Tsukuba 305-8506, Japan


Received: January 16, 2020
Revised: July 3, 2020
Accepted: July 5, 2020

 Copyright The Author(s). This is an open access article distributed under the terms of the Creative Commons Attribution License (CC BY 4.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are cited.

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Nakagawa, M., Nakayama, T., Sasago, H., Kuruma, Y., Yai, H., Ogawa, S., Deng, Y., Mochida, M. and Matsumi, Y. (2020). Assessment of the Sphericity Characteristics of Submicron Particles Using a Single-particle Polar Nephelometer at an Urban Site in Japan. Aerosol Air Qual. Res.


  • Scattering angular distribution of individual particles was measured in an urban site.
  • Particle sphericity was estimated from scattering angular distribution.
  • At least two types of particles with high and low sphericities were externally mixed.
  • Particle sphericity increased during daytime by photochemical formation or aging.
  • Nitrate formation possibly increased sphericity in the early morning during high RH.


Sphericity is one of the essential properties of particles in evaluating their effects on climate and human health. With the use of a home-made polar nephelometer, real-time measurements of the scattering angular distribution of individual particles with a diameter of 500 nm, with and without passing through the thermodenuder (TD), were conducted in Nagoya, Japan, to examine particle sphericity and its controlling factors. Particle sphericity was estimated from the depths of local minima in the scattering angular distributions, and ambient aerosols were found to be external mixtures of at least two types of particles with relatively high and low sphericities. Although most particles with higher sphericity were removed with passage through the TD, approximately one-third with lower sphericity remained. In the daytime, the proportion of particles with low sphericity were lower and the average sphericity of particles with high sphericity increased, which can be explained by the photochemical formation and/or aging processes. For days when the relative humidity was extremely high, another peak in the diurnal variation of the average sphericity was found in the early morning, which is possibly due to secondary formation of nitrate.

Keywords: Polar nephelometer; Scattering angular distribution; Single particle; Particle sphericity.

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