A comparative study on effective density, shape factor, and volatile mixing of non-spherical particles using tandem aerodynamic diameter, mobility diameter, and mass measurements

Mohsen Kazemimanesh, Md Mostafizur Rahman, Dumitru Duca, Tyler J. Johnson, Ahmed Addad, George Giannopoulos, Cristian Focsa, Adam M. Boies

Research output: Contribution to journalArticlepeer-review

11 Citations (Scopus)


Combustion-generated particles are typically non-spherical (soot aggregates) and sometimes mixed with organic compounds (e.g. in vehicle emissions). The effective density, dynamic shape factor, and volatile mixing of particles are widely studied using aerosol instruments that measure the particle mobility diameter, aerodynamic diameter, and mass. In theory, any of these three physical properties can be obtained from a combination of the other two. In the present study, a tandem arrangement of aerodynamic aerosol classifier (AAC; measuring aerodynamic diameter), differential mobility analyzer (DMA; measuring mobility diameter), optional catalytic stripper (CS), and centrifugal particle mass analyzer (CPMA; measuring particle mass) was used to study the effective density, dynamic shape factor, and volatile mixing of non-spherical non-homogenous particles. In terms of mass, the vast majority of the particles were purely semi-volatile mixed with soot with and without semi-volatile coating. The effective density of polydisperse non-stripped particles was relatively constant (indicating nearly spherical particles), while that of polydisperse stripped particles decreased from ∼1200 to ∼800 kg/m3 as the particle size increased (indicating a compact structure). The effective density of monodisperse particles, measured by DMA-CPMA, AAC-DMA, and AAC-CPMA methods, was consistent within the measurement uncertainty; however, the latter method had larger discrepancy with the other two methods, particularly for non-spherical particles. The dynamic shape factor, measured by AAC-CPMA and DMA-CPMA methods, increased with the mobility diameter, a trend also supported by electron micrographs. The volatile mass fraction of particles decreased as their mobility diameter increased, with smaller particles having volatile mass fraction of ∼20%. This result was further confirmed by chemical characterization of size-selected particles, proving the robustness of online aerosol measurements.

Original languageEnglish
Article number105930
JournalJournal of Aerosol Science
Early online date13 Dec 2021
Publication statusPublished - Mar 2022
Externally publishedYes

Bibliographical note

NOTICE: this is the author’s version of a work that was accepted for publication in Journal of Aerosol Science. Changes resulting from the publishing process, such as peer review, editing, corrections, structural formatting, and other quality control mechanisms may not be reflected in this document. Changes may have been made to this work since it was submitted for publication. A definitive version was subsequently published in Journal of Aerosol Science, 161 (2022)
DOI: 10.1016/j.jaerosci.2021.105930

© 2021, Elsevier. Licensed under the Creative Commons Attribution-NonCommercial-NoDerivatives 4.0 International http://creativecommons.org/licenses/by-nc-nd/4.0/


Funding Information:
This project has received funding as a part of the PEMS4Nano project from the European Union's Horizon 2020 research and innovation programme under Grant Agreement no. 724145 . Additionally, this work was supported by the UK EPSRC Center for Sustainable Road Freight ( EP/R035199/1 ) and NERC Integrated Research Observation System for Clean Air ( NE/T001909/1 ).

Funding Information:
The authors wish to acknowledge contributions of equipment and time from our PEMS4Nano partners, Bosch GmbH, TSI Inc. and Horiba Ltd. The TEM facility in Lille, France is supported by the Conseil Régional des Hauts-de-France and the European Regional Development Fund (ERDF).


  • Dynamic shape factor
  • Effective density
  • Non-spherical
  • Soot
  • Tandem measurement
  • Volatile mixing

ASJC Scopus subject areas

  • Environmental Engineering
  • Pollution
  • Mechanical Engineering
  • Fluid Flow and Transfer Processes
  • Atmospheric Science


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