The first 40 to 50 mi (64–80 km) above the earth contains 99% of the total mass of the earth's atmosphere and is generally of a uniform composition, except for a high concentration of ozone, known as the ozone layer, at 12–30 mi (19–50 km).
The lower atmosphere contains varying amounts of water vapor, which determine its humidity.
The air also carries many kinds of dust of meteoric as well as terrestrial origin.
Various gaseous and solid impurities resulting from human activity (pollution).
CFCs (Chlorofluorocarbons) – chemically stable gases used in air conditioners and refrigerators.
Properties of the atmosphere:
•nitrogen, 78.09%
•oxygen, 20.95%
•argon, 0.93%
•carbon dioxide, 0.03%
•traces of neon, helium, methane, krypton, hydrogen, xenon, and ozone.
Layers of the atmosphere.
Retrieved on November 13th, 2008 from http://ds9.ssl.berkeley.edu/lws_gems/3/graph_1.htm
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