ozone depletion

Ozone Depletion

Formation of Ozone

O2 + UV O + O

O + O2 O3 (Ozone)

Chlorofluorocarbons - CFC’s

Principle Cause of Ozone Depletion

Once used in: •Air conditioners •Refrigerators •Aerosol Sprays •Plastic Foams

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

Chemical Reactions

* CFCl3 + UV ➔ Cl• + CFCl2

* ClO• + O• ➔ O2 + Cl• * Cl• + O3 ➔ O2 + ClO•

Other Ozone-Destroying Chemicals

Methyl Bromide – Pesticide

Halons -Fire Extinguishers

HCFC’s - Refrigerants

Carbon Tetrachloride & Methyl Chloroform – Solvents

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

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

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)

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

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.

Food supply

� Reduce photosynthesis - crops affected.

� Kills plankton fish ↓

Ozone Depletion ≠ Global Warming