Section 9 and 10 Ozone Depletion • What is the threat from ozone depletion? Good versus bad ozone. • What causes ozone depletion? • What happens to ozone levels over Earth’s poles? • Why should we be worried about ozone depletion? • What are solutions to this problem?
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Section 9 and 10 Ozone Depletion What is the threat from ozone depletion? Good versus bad ozone. What causes ozone depletion? What happens to ozone levels.
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Section 9 and 10 Ozone DepletionSection 9 and 10 Ozone Depletion
• What is the threat from ozone depletion? Good versus bad ozone.
• What causes ozone depletion?
• What happens to ozone levels over Earth’s poles?
• Why should we be worried about ozone depletion?
• What are solutions to this problem?
Ozone DepletionOzone Depletion
What is ozone?
“Good” versus “bad” ozone
Where is the “ozone layer”
Keeps out about 95% of UV rays
Layer has been thinning
Ozone Depletion: What Causes Depletion?Ozone Depletion: What Causes Depletion?
GM Chemist discovered Chlorofluorocarbons in 1930 (CFCs)
…also known as freon
• Very stable• Nontoxic• Noncorrosive• Inexpensive
“Dream Chemical”
Ozone Depletion: What Causes Depletion?Ozone Depletion: What Causes Depletion?
CFCs used for:
• Coolant in refrigerators and air conditioners
• Propellant in aerosol sprays
• Cleaner for electronics
• Bubbles in plastic foams
• Insulations
Former Uses of CFCsFormer Uses of CFCs
Air Conditioners
Refrigerators
Spray cans
Cleaners for electronic parts
Sterilizing medical instruments
Fumigants for granaries and cargo ships
Air Conditioners
Refrigerators
Spray cans
Cleaners for electronic parts
Sterilizing medical instruments
Fumigants for granaries and cargo ships
Ozone Depletion: What Causes Depletion?Ozone Depletion: What Causes Depletion?
Too good to be true:
1974 study at UC Irvine indicated threat to ozone layer from CFCs
Shock to the $28 billion per year CFC industry –DuPont and other chemical companies
Ozone Depletion: What Causes Depletion?Ozone Depletion: What Causes Depletion?
1) CFCs remain stable in troposphere due to unreactivity
2) Over 11-20 years they get lifted into stratosphere by convection and drift
3) Once in stratosphere they break down by UV rays releasing highly reactive chlorine atoms (with others) that in a chain reaction break apart ozone
Ozone Depletion: What Causes Depletion?Ozone Depletion: What Causes Depletion?4) Each CFC molecule lasts
in stratosphere for 65-385 years
Can convert 100,000 of O3 to O2 during that time.
DuPont and others fought findings until 1988 when they admitted problems.
1995 Nobel Prize Chemistry
Ozone Depletion in the StratosphereOzone Depletion in the Stratosphere
Fig. 21-21 p. 484
Ozone Depletion: What Causes Depletion?Ozone Depletion: What Causes Depletion?