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Ozone Depletion
• Ozone (O3)
– Absorbs harmful UV radiation from sun
ozone is produced during lightning storms
• Chlorofluorocarbons (CFC’s) destroy ozone
– CFC’s production was banned in 1977
– CFC’s “live” for hundreds of years
Depletion of the Ozone Layer

Ozone (O3) in upper atmosphere blocks ultraviolet (UV) light from Sun.

UV causes skin cancer and cataracts.

O3 depletion is caused by chlorofluorocarbons (CFCs).
Uses for CFCs:
CFCs
refrigerants
aerosol propellants
banned in U.S. in 1996
O3 is replenished with each strike of lightning.
Freon (CFC’s)
chlorofluorocarbons
F
Cl
C
Cl
Cl
Cl
Trichlorofluoromethane
(Freon-11)
Cl
C
F
F
Dichlorodifluoromethane
(Freon-12)
CFC-11 and CFC-12 are odorless, nontoxic, nonflammable, and very stable.
Mechanism of Ozone Depletion
“free radical”
• Initiation
CCl2F2
• Propagation
Cl . + O3
Solar radiation
ClO . + O .
Cl. + CF2Cl .
ClO. + O2
Cl . + O2
• Termination
A single chlorine molecule can destroy thousands of ozone molecules.
Ozone, O3
Ozone Hole
Grows Larger
Ozone hole has increased 50% from 1975 - 1985
Monthly Change in Ozone
TOMS Total Ozone Monthly Averages
Ultraviolet Radiation
• Skin cancer
• Cataracts
• Sun-glasses
UVA & UVB protection
Greenhouse Effect vs. Ozone
Hole
Alike
Different
Global Warming
by trapping heat
on Earth
Plant trees to
slow down and burn
less fossil fuels
that produce CO2
Depletion of O3
(ozone layer)...
causes skin cancer
and cataracts
Environmental
Issues
Topic
Caused by
buildup of CO2
carbon dioxide
Different
Greenhouse
Effect
Topic
Related to
Earth's
Atmosphere
Man-made
problem
Ozone
Hole
Caused by CFC's
(chlorofluorocarbons)
destroying ozone
layer
Replace CFC's in
AC & refrigerators