Pollution

CFC’s and the Ozone Layer

What is the ozone layer?

• 90% of the world’s ozone (O₃) is found in the high atmosphere (upper stratosphere – 17km to 26km above the earth’s surface). Mount Everest is 9km high.
• This is a renewable thin veil which is essential for life as it protects against 99% of harmful U.V. radiation reaching the surface of the Earth.
• Ozone is formed by the action of U.V. radiation on oxygen.
  O₂ is split by U.V. radiation into O + O
  O₂ then combines with O to form O₃
• At low levels (the troposphere – surface up to 15km) ozone can be harmful.
• It acts as a super-greenhouse gas (10⁵ worse than Carbon Dioxide)
• Traps pollution (dust and smoke) causing city ‘smogs’.
• Direct irritation to eyes and lungs.
• Damage to leaves and may reduce crop production by 10%.
• Ozone at low level is produced by fossil fuel combustion.
  NO₂ is released by combustion
  NO₂ is split by U.V. radiation into NO + O
  O₂ then combines with O to form O₃
   

Value of the upper ozone layer.

• Stratospheric ozone absorbs solar ultraviolet radiation which would otherwise reach the Earth’s surface.
• Some UV-B (290-320nm) reaches the earth and causes:
• Sunburn
• Some forms of cancer
• Eye cataracts
• UV-C (240-290nm) does not at present reach the surface but laboratory tests have shown that it causes damage to DNA (increased mutation rates) and proteins.
   

 Ozone Holes