Ozone, UV and Aerosol studies

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Aerosol particles in the atmosphere

Aerosols are particles in the solid or liquid phase that are suspended in the atmosphere. They range in size (diameter) from a few nanometers to tens of micrometers. Particles may be either directly emitted into the atmosphere (primary aerosols) or can be formed there by conversion processes (secondary aerosols). Sources of aerosols can be either natural or anthropogenic. Natural sources include:

  • wind-borne dust
  • sea spray
  • volcanic activities
  • biomass burning


Emissions that can be attributed to anthropogenic activities include:

  • fuel combustion
  • industrial processes
  • non-industrial fugitive sources (e.g. construction work)
  • transportation sources (e.g. automobiles)


Aerosol particles can change their size and composition by condensation of vapour species or by evaporation, by coagulation with other particles, by chemical reaction or by activation in the presence of water supersaturation to become fog and cloud droplets. Particles are removed from the atmosphere by two 2 mechanisms: deposition at the Earth's surface (dry deposition) and incorporation into cloud droplets during the formation of precipitation (wet deposition).


Relative sizes of a typical raindrop, a droplet of water in a cloud, an extremely large aerosol particle and a smaller aerosol particle of a more typical size (Source: