1. Ozone Depletion

2. Role of stratospheric ozone (ozone layer) in absorption of UV light
Cause of Ozone Depletion
Ozone Depletion
Geographic location of where ‘hole’ is worst
Effect of UV on living organisms
Methods of Reducing CFC’s

3. Role of stratospheric ozone (ozone layer) in absorption of UV light

4. Cause of Ozone Depletion
CFC’s
Chlorine
Chlorine breaks down atmosphere

5. Chemical Reactions
Summary of Reactions:

6. Happens in Stratosphere
Chemical Reactions
Ozone Destruction
A single chlorine atom is chlorine radical because it has a free electron which makes it highly reactive.
A free chlorine radical can react with an ozone molecule, breaking it down to leave an two oxygen molecules and chlorine monoxide
Happens in Stratosphere

7. Chemical Reactions
The chlorine monoxide can then react with a monatomic oxygen atom to make chlorine dioxide. This prevents the formation of ozone!

8. Chemical Reactions
The ClO can then break down to release chlorine again which may repeat these reactions thousands of times.
This means these reactions start and end with a free radical of Cl.

9. Cl + O3 + O  2 O2 + Cl Summary of Reactions
The reactions that regulate ozone are therefore in a state of ’dynamic equilibrium’.
Chlorine is so reactive that if it is released in the troposphere it will probably react with another element and never reach the stratosphere! The reactions above therefore occur in the troposphere as explained earlier.

10. Geographic location of where ‘hole’ is worst
4% loss over whole globe
Worst in the Spring-October
33% Loss in Arctic
66% Loss in Antarctic

11. Effect of UV on living organisms

12. Methods of Reducing CFC’s
Evidence suggests the hole may now disappear by 2070 due to the ban on CFC’s
Montreal Protocol 1987!
HCFC’s in refrigeration units
Alternative propellants e.g. Butane and propane
Replacement Materials