how ozone layer depletion take place, what causes depletion.

1. Ozone Depletion

2. Formation of Ozone
O2 + UV O + O
O + O2 O3 (Ozone)

3. Principle Cause of Ozone Depletion
Chlorofluorocarbons - CFC’s
Once used in:
•Air conditioners
•Refrigerators
•Aerosol Sprays
•Plastic Foams

4. CFCs are used in aerosol sprays
CFCs were used as refrigerants in the
past

5. Chemical Reactions
* CFCl3 + UV ➔ Cl• + CFCl2
* ClO• + O• ➔ O2 + Cl•
* Cl• + O3 ➔ O2 + ClO•

6. Other Ozone-Destroying Chemicals
Methyl Bromide – Pesticide
Halons -Fire Extinguishers

7. Carbon Tetrachloride & Methyl Chloroform – Solvents
HCFC’s - Refrigerants

8. Present situation
Stratospheric ozone over Antarctica:
– Has been depleted over the last 15 years
– The ozone hole:
enlarging
large enough to cover most of the North America
would take at least 50 years to restore

9. Effects of Air Pollution Summary
• Respiratory Problems - coughing, bronchitis,
asthma, emphysema, cancer
• Cardiovascular Problems - CO
• Nerve Damage - Hg and Pb
• Tree damage
• Acidify lakes
• Damage concrete, statues

10. Effects of UV
• Sunburn
• Accelerated Aging (wrinkles, sun spots)
• Depresses immune system
• Cataracts Clouding of Lens of Eye
(400,000 new cases/year US (1 in 49 people)

11. Causes of ozone depletion
Details are not fully understood
Catalyzed by halocarbons (carbon compounds
containing fluorine, chlorine, bromine and iodine)
– Examples: CFCs and ClONO2
Halogen atoms catalyze ozone layer depletion by
destroying ozone molecules and forming oxygen
molecules.
Much more serious in Antarctica than other regions
on the planet

12. Consequences of less ozone
Because CFCs has long life span
and very stable, it continuous to
attack the ozone layer and more
UV reach our earth.

13. Food supply
Reduce photosynthesis - crops
affected.
Kills plankton  fish ¯

14. Ozone Depletion ≠ Global Warming