Physical and chemical properties of aerosol particles in the troposphere

Aerosol particles are an important constituent of the atmospheric system. Particles may be created as primary aerosol particles - those that are released directly into the atmosphere as particulate matter or as secondary aerosols - those formed during gas-to-particle conversion of gaseous precursors emitted into the atmosphere. Particles are emitted from both natural and anthropogenic activities. Sources vary from widespread surface sources like deserts and arid surfaces (mineral soil dust), oceans (sea-salt), biosphere (pollen, bacteria, plant debris) and biomass and fuel burning (organic and graphitic carbon, fly ash). Industries and diffuse sources like traffic emit mainly carbonaceous aerosols and secondary gaseous precursors, while intense point sources, e. g., volcanic eruptions, inject large volumes of particles and traces gases into the atmosphere. Extraterrestrial sources are usually negligible. The major gaseous precursors are sulphur dioxide (SO2), ammonia (NH3), oxides of nitrogen (NOx), dimethyl sulphide (DMS) and volatile organic compounds (VOCs). Estimates for global source strengths of particles and their precursors can be found elsewhere (IPCC, 2001). [...]