stratospheric ozone depletion - willis'...
Post on 06-Sep-2018
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• Ozone: 3 oxygen atoms in
stratosphere that absorbs UV radiation
• Protects us from UV B and UVC
radiation: sunburns and cancer
Strat. O3 Formed?
O2 + UV (light) O + O
O + O2 Stratospheric O3
O3 + UV O + O2
**The Cycle Continues**
• UV rays broke down CFC’s so Cl-
interacted w/ O3: Cl- + O3 ClO + O2
• 1 Cl- can break down 1000’s of O3
molecules. (Br- also)
CFC’s in Stratosphere
• Rowland and Molina (1974)- UCI
• Chlorine atoms are removed
from CFCl3 by UV light
• CFCl3 + UV -------> CFCl2 + Cl
• Cl + O3 --------> ClO + O2
• 2ClO + UV -------> 2Cl + O2
I guess there is a reason to
go to UCI…!
Why Antarctica?
• In Antarctic winter icy clouds
form sites for CFCs to react and
produce Cl2 atoms
• Cl2 stay attached to clouds until
spring
• In spring, ice crystals melt,
releasing Cl2 into air react to
remove O3
Protecting Ozone Layer
• 1978 - U.S. banned use of CFC’s
• 1987 - Montreal Protocol: gradually
phased out use of CFC’s
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