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Term Ozone

A substance whose molecule is composed of three oxygen atoms (O3) instead of two, as in the case of molecular oxygen (O2). Ozone is a gaseous component of the atmosphere, which is found in different concentrations between 10 and 40 kilometers above sea level. It is divided in tropospheric ozone and stratospheric ozone.

The stratospheric ozone is constantly being formed in the ozone layer, which is located in the earth's stratosphere between 20 and 40 kilometers of altitude. The stratospheric ozone is formed by the action of ultraviolet light (uv), which breaks the links between the two atoms that make up oxygen gas. Each atom of oxygen released binds to another molecule of oxygen (O2), forming molecules of ozone (O3). Stratospheric ozone acts as an air purifier and as a filter against dangerous ultraviolet radiation from the sun, allowing only visible light to pass and thus protecting the development of life on earth.

Tropospheric ozone, which is located in the lowest layer of the atmosphere between 10 and 20 kilometers above sea level, is formed through a completely different mechanism. In this case, ozone is formed through photochemical reactions between nitrogen oxides (NOx) and volatile organic compounds (VOCs), pollutants that come from human activity such as burning fuel. The high presence of tropospheric ozone becomes a problem because it is highly toxic, and-- in sufficient concentration-- may cause damage to human health (starting at approximately 150 micrograms per cubic meter) or to vegetation (starting at approximately 30 parts per billion).

See chlorofluorocarbons (CFCs)


Additional Information
GraphicOzone Layer
GraphicOzone Layer 2
GraphicOzone Layer 3
Topic  Environmental pollutionClimate