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 occurs here
72% of all air is below the cruising altitude of commercial airliners (33000 ft)

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

4. 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

5. 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
Cooling of the Earth's stratosphere and possibly some surface climatic effect
Degradation of paints and plastic material

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

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

9. Good Ozone

10. Ozone Formation
Ozone forms a layer in the stratosphere, thinnest in the tropics (around the equator) and denser towards the poles.
O2 + hv  O + O
(1) O + O2 O3
wavelength ~ 240 nm

13. 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

14. 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

15. Destroying Good Ozone

17. Destroying Good Ozone
Chloroflourocarbons were first created in 1928 as non-toxic, non-flamable refrigerants, and were first produced commercially in the 1930's by DuPont
In 1974, a laboratory study demonstrated the ability of CFC's to catalytically breakdown Ozone in the presence of high frequency UV light
Cl + O3 -> ClO + O2 ClO + O3 ---> 2 O2 + Cl
In a 1985, a study summarized data that had been collected by the British Antartic Survey showing that ozone levels had dropped to 10% below normal January levels for Antarctica.

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

19. The frozen crystals that make up polar stratospheric clouds provide a surface for the reactions that free chlorine atoms in the Antarctic stratosphere

20. 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

24. Montreal Protocol
An international treaty designed to protect the ozone layer
phasing out production of number of substances believed to be responsible for ozone depletion
Effective January 1, 1989
Five revisions
1990 (London)
1992 (Copenhagen)
1995 (Vienna)
1997 (Montreal)
1999 (Beijing)

27. Septembe r 21-30, the average area of the ozone hole was the largest ever observed, at million square miles