Glossary: Aerosols

Aerosols

Aerosols are solid or liquid particles dispersed in the air,and include dust, soot, sea salt crystals, spores, bacteria, viruses and a plethora of other microscopic particles. Collectively, they are often regarded as air pollution, but many of the aerosols have a natural origin. They are conventionally defined as those particles suspended in air having diameters in the region of 0.001 to 10 microns (millionth of a metre). They are formed by the dispersal of material at the surface (primary aerosols), or by reaction of gases in the atmosphere (secondary aerosols).

Primary aerosols include volcanic dust, organic materials from biomass burning, soot from combustion and mineral dust from wind-blown processes. Secondary aerosols include sulphates from the oxidation of sulphur-containing gases during the burning of fossil fuels, nitrates from gaseous nitrogen species, and products from the oxidation of volatile organic compounds (VOCs). Although making up only 1 part in a billion of the mass of the atmosphere, they have the potential to significantly influence the amount of sunlight that reaches the Earth's surface, and therefore the Earth's climate