CFC's and Ozone Depletion
Ozone in the Atmosphere
Ozone in the Lower Atmosphere (troposphere)
About 10% of all ozone (O3) in the atmosphere is found in the troposhere (up to 16km above the earth's surface).
Ozone in the troposhere has harmful effects on many living things because it is toxic.
In humans, ozone causes eye irritation, compromised lung functions, aggrevation of respiratory conditions like asthma, and increases the susceptibility to infection.
Ozone pollution in the troposphere is often linked to photochemical smog.
Ozone in the lower atmosphere is formed during electrical discharge from high voltage appliances as shown in the equations below:
O2(g) → 2O(g)
O2(g) + O(g) → O3(g)
Ozone in the Upper Atmosphere (stratosphere)
About 90% of all ozone (O3) in the atmosphere is found in the stratosphere (16 to 32 km above the earth's surface).
In the stratosphere ozone acts as the primary UV radiation shield, short wavelength UV radiation from the sun (<240nm) provides the energy to split oxygen molecules into oxygen atoms:
|O2(g)||UV radiation |
Oxygen atoms then react with oxygen molecules to form ozone:
O(g) + O2(g) → O3(g)
Ozone can absorb harmful UV-B and UV-C radiation, preventing it from reaching the earth's surface:
|O3(g)||UV radiation |
|O2(g) + O(g)|
The constant formation and destruction of ozone maintains a balance over time.
Human acitivities, such as the release of chlorofluorocarbons in to the atmosphere, have disturbed this balance.