Atmosphere
The atmosphere is a mechanical mixture of gases (as opposed to a chemical compound) which is dominated by four gases. Nitrogen, oxygen, argon and carbon dioxide acount for 99.98% of the atmosphere. They are mixed in constant proportion up to 80 km. greenhouse gases play an important role in the thermodynamics of the atmosphere. they have the ability to trap longwave terrestrial radiation (the greenhouse effect). Without greenhouse gases the earth would be cold as the radiation entering the atmosphere would not be trapped. The main greenhouse gases are nitrous oxide, carbon dioxide, methane and chloroflourocarbons (CFC's).
Carbon dioxide exists in a complex global cycle. Some of it is released form the interior of the earth, some is produced through respiration, soil processes, combustion, and evaporation over oceans. Carbon dioxide is dissolved in oceans and by photosynthesis. Methane is produced primarily by anaerobic processes in wetlands and digestive processes and also by the burning of biomass. Nitrous oxide is produced by biological mechanisms in oceans and soils. It is also produced by industrial combustion, automobiles, chemical fertilisers and the burning of biomass. CFC's are produced by anthropogenic activity (human activity or interferance). Our activity produces aerosol propellants, air conditioners and refrigerator coolants such as frion and some household cleaners that aid in the production of these carbons. Ozone is formed by high level breakup of oxygen molecules by U.V.R. It can also be destroyed by reactions involving nitrogen and chlorine in the middle and upper atmosphere. |
