1. Advanced Placement Environmental Science Teacher
Ozone Hole
Mark Ewoldsen, Ph.D.
Advanced Placement Environmental Science Teacher
La Cañada High School

2. Two Atmosphere Layers Stratosphere is above Troposphere
Ozone Layer blocks UV radiation
Troposphere is where we live
Weather and Global Warming
72% of all air is below the cruising altitude of commercial airliners (33000 ft)

4. Stratospheric Ozone vs. Tropospheric Ozone
(Good)
vs.
Tropospheric Ozone
(Bad)

5. Ozone – Two Faces Stratosphere – Good Ozone Troposphere – Bad Ozone
Blocks UV radiation
Hole caused by depletion due to CFC’s
Troposphere – Bad Ozone
Pollution
Photochemical smog
Eye irritant

6. Harmful effects of UV radiation
Skin cancer such as melanoma(ultraviolet radiation can destroy acids in DNA)

7. matrix.ucdavis.edu/tumors/tradition/ gallery-ssmm.html

8. Harmful effects of UV radiation
Skin cancer such as melanoma(ultraviolet radiation can destroy acids in DNA)
Cataracts and sun burning

9. www.snec.com.sg/clinical_services/ cataract.asp

10. Harmful effects of UV radiation
Skin cancer such as melanoma(ultraviolet radiation can destroy acids in DNA)
Cataracts and sun burning
Suppression of immune systems
Adverse impact on crops and animals
Reduction in the growth of ocean phytoplankton
Degradation of paints, plastics, tires

12. Good Ozone
Most ionizing

14. Natural Ozone Hole Winter = no sunlight
Air in the polar vortex can get very cold -80C
Special clouds called Polar Stratospheric Clouds form as nitric acid trihydrate
PSCs are crucial for ozone loss to occur
Since there is no sunlight, the air within the polar vortex can get very cold

16. The ozone hole builds up over the winter months, peaking at around September and breaking up again by December, this data set from 2005
                               July
                          August
                               September
           October
                               November
December

19. Destroying Good Ozone Chloroflourocarbons discovered (1928) In 1974
Non-toxic, non-flamable refrigerants by DuPont
In 1974
Cl + O3 -> ClO + O2 ClO + O3 ---> 2 O2 + Cl
In a 1985
Ozone levels had dropped to 10% below normal January levels for Antarctica.

20. A single chlorine atom removes about 100,000 ozone molecules before it is taken out of operation by other substances

21. Ultraviolet light hits a chlorofluorocarbon
(CFC) molecule, such as CFCl3, breaking
off a chlorine atom and leaving
CFCl2.
Sun Cl Cl
Once free, the chlorine atom is off
to attack another ozone molecule
and begin the cycle again. C Cl F
UV radiation Cl Cl O O
A free oxygen atom pulls
the oxygen atom off
the chlorine monoxide
molecule to form O2.
The chlorine atom attacks
an ozone (O3) molecule, pulling an oxygen atom
off it and leaving
an oxygen
molecule (O2). Cl Cl O O O O O
The chlorine
atom and the
oxygen atom join
to form a chlorine
monoxide molecule (ClO) Cl O O O

22. Montreal Protocol (1987)
International treaty to protect the ozone layer
phasing out production of number of substances believed to be responsible for ozone depletion
Effective January 1, 1989

23. Signed
Effective