Atmospheric humidity and particle charging state on agglomeration of aerosol particles

Yuanping He, Zhaolin Gu, Weizhen Lu, Liyuan Zhang, Tomoaki Okuda, Kentaro Fujioka, Hui Luo, Chuck Wah Yu

Research output: Contribution to journalArticlepeer-review

44 Citations (Scopus)


Formation of haze is a phenomenon dependent on the relative atmospheric humidity and concentration of aerosol particles. The physical and chemical reactions on particle surfaces would lead to variations in particle sizes. This paper focuses on the physical behaviour of aerosol particles under the influence of atmospheric humidity, which produces liquid bridging forces and electrostatic interactions among particles. By water absorption experiment, a correlation between relative humidity (RH) and water content on particles was obtained. Through theoretical derivation, a relationship between the relative humidity and humidity ratio was established for calculating liquid bridging forces. The findings from experiments on atmospheric particles charging, showed most aerosols were negatively or positively charged and the average charges on these particles was more than one. An extended soft-sphere discrete element method (DEM) was used to simulate the evolution of aerosol particles, encapsulated in water vapour by considering liquid bridging forces, electrostatic interactions and Brownian forces. Results suggest that the agglomeration rate of particles would increase with a rise in the atmospheric humidity due to the increased liquid bridging forces that enhance the agglomeration velocity. The higher humidity would enhance the ionization on particle surfaces, which could affect electrostatic interactions. This paper provides an insight of a mechanism for formation of haze in atmosphere.

Original languageEnglish
Pages (from-to)141-149
Number of pages9
JournalAtmospheric Environment
Publication statusPublished - 2019 Jan 15


  • Aerosol particles
  • Agglomeration rate
  • Atmospheric humidity
  • Electrostatic interactions
  • Haze formation
  • Liquid bridging forces
  • Particle charging

ASJC Scopus subject areas

  • General Environmental Science
  • Atmospheric Science


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