1. By: Desiree Collins
The Ozone Layer

2. History of the Ozone Discovery
Dramatic loss of ozone in the lower stratosphere over Antarctica was first noticed in the 1970s by a research group
from the British Antarctic Survey were monitoring the atmosphere above Antarctica.

3. What is the ozone hole?
News media confuses it with the problem of global warming
Ozone contributes to the greenhouse effect
Over Antarctica (and the Arctic), stratospheric ozone depleted over past 15 years at certain times of the year
Hole presently size Antarctica, 10km altitude - lower stratosphere

4. What is ozone?
Ozone forms a layer in the stratosphere, thinnest in the tropics (around the equator) and denser towards the poles

5. How is ozone formed?
UV radiation strikes the O2 molecule and splits it, atomic oxygen associates itself with another O2 molecule .

6. Hole Formation Based on Two different mechanisms:
Meteorological mechanism
Movement of air from one place to another in the upper stratosphere
Cold temperature in the upper atmosphere causes nitric acid to freeze into crystals forming wispy pink clouds
Forms a vortex of tightly twisted winds thus forming a hole in the upper atmosphere

7. Chemical Mechanism
Different chemicals are responsible for the destruction of the ozone layer
Topping the list :
chlorofluorocarbons (CFC’s)
man-made, non-toxic and inert in the troposphere
In the stratosphere are photolysed, releasing reactive chlorine atoms that catalytically destroy ozone

8. UV light & DNA UV-B has a direct effect on DNA
DNA absorbs UV light of 260nm
The action of UV forms thymine dimers
This can cause a gene mutation when the DNA replicates

9. Specific damage by UV light
Sunburn
Clouding of the cornea and formation of cataract
Skin cancer (melanoma)
Reduced rates of photosynthesis

10. What are CFCs? Used as propellants in aerosol spray cans
Used as refrigerants in fridges, freezers and air conditioning units

11. What can be done? Reduce the use of CFCs
They are already banned in aerosols (1987)
BUT they are still used as refrigerants
Recycle fridges and air conditioning plants

12. The current situation
The holes developing over the pole suggest that they may be show an improvement
BUT CFC molecules take 30 years to rise up to the stratosphere
The chlorine radicals last a long time
The peak ozone damage was supposed to be in 2000
Damage could go on another 50 years