A - THE ATMOSPHERE
Introduction 
Radiation and The Atmosphere
Ozone
Halogenoalkanes
Problems in the Troposphere
Introduction
What's in the Air?
Introduction
This topic studies the atmosphere, and some chemical processes that occur in this global area.
The processes that go on in this area are vital to life. Some human activities have destroyed the gases in this area, and it is vital that we correct the problems caused by these activities in the past.
You may also want to refer back to:
What's in the Air?
The atmosphere extends about 100km above the Earth's surface. The two most chemically important regions are the troposphere (up to 15 km) and the stratosphere (15 - 50 km). The atmosphere becomes less dense the higher you go. 90% of all molecules in the atmosphere are in the troposphere. Temperature decreases through the troposphere but increases through the stratosphere. The composition of the troposphere is shewn below:
| Gas | Concentration by Volume |
|---|---|
| Nitrogen | 78% |
| Oxygen | 21% |
| Argon | 1% |
| Carbon dioxide | 353ppm |
| Neon | 18ppm |
| Helium | 5ppm |
Other gases are present but in smaller quantities. Natural processes produce all the gases listed. Other gases in the atmosphere, e.g. CFCs (chlorofluorocarbons) are only produced as a result of human activity.
Gases mix together completely by diffusion, so pollutant gases will spread throughout the atmosphere in time.
