2. Quick review of atmosphere layers
Troposphere
0 – 12 km thick
75% of all gases in atmosphere;
all weather happens here;
temperature decreases with higher altitude (gets colder!)

3. Quick review of atmosphere layers
Stratosphere
12-50 km thick
horizontal winds (jet stream)
contains ozone layer
temperature increases with higher altitude (gets warmer!)

4. Quick review of atmosphere layers
Mesosphere
50-80 km thick
meteor showers happen here
temperature decreases with higher altitude (gets colder!)

5. Quick review of atmosphere layers
Thermosphere
aurora borealis and aurora australis (northern lights)
ionosphere is here…reflects radio waves for communications
can be very very hot (2000+ ℃) !

6. Quick review of atmosphere layers
Exosphere
550km+ above earth’s surface
outermost layer of earth’s atmosphere
satellites orbit here

7. Atmosphere

8. Intro to Ozone Ozone is found in two layers of the atmosphere
Stratosphere = good ozone
Troposphere = bad ozone

9. GOOD OZONE
(Blocks harmful UV radiation)
BAD OZONE!
(part of smog pollution)

10. HOW IS OZONE FORMED AND DESTROYED?

11. Intro to Ozone O3 Made of 3 oxygen atoms A reactive gas
What does ozone do?
Stratospheric ozone blocks incoming UV radiation from the sun
Protects life from damaging UV radiation!

12. The Ozone Layer The ozone layer is in dynamic equilibrium
Ozone is constantly made from oxygen atoms and is continuously converted back to oxygen.
Equilibrium because: there is a balance between two ongoing processes

13. The Ozone Layer UV radiation gets absorbed when
ozone molecules are formed
and when
ozone molecules break apart

14. Ozone and UV radiation Ozone…
allows UV-A and UV-B through
blocks UV-C waves.
Ozone layer absorbs 99% of UV-C and 50% of UV-B

15. Effects of UV radiation
UV-A – Lowest energy (longest wavelength) causes wrinkles
UV-B - causes skin cancer
UV-C – Highest energy (shortest wavelength). Most harmful, because of damage to organisms/tissues

16. Effects of UV Radiation
Damaging Effects:
Genetic mutations that effect health
Damage to living tissues (sunburns, etc.)
Cataract formation in eyes
Skin cancers
Suppression of immune system

17. Effects of UV Radiation
Damaging Effects:
Damage to photosynthetic organisms, especially phytoplankton
Damage to consumers of photosynthetic organisms, especially zooplankton
(these are the BASE OF AQUATIC FOOD WEBS!)

18. Beneficial Effects of UV
In animals, stimulates the production of Vitamin D
Treat psoriasis and vitiligo (skin diseases)
Steriliser, water purifier
Forensics, lighting, lasers

19. Damage to the Ozone Layer
Ozone Depleting Substances (ODSs) are breaking down the ozone layer

20. Sources of ODS’s aerosols (spray cans) gas-blown plastics pesticides
flame retardants
refrigerants

21. HOGs (Halogenated Organic Gases)
HOG’s are usually stable but break down into halogen atoms (F, Cl, Br, I, At) which are highly reactive and destroy the ozone layer
A type of HOG is chlorofluorocarbon (CFC)

22. CFCs (chlorofluorocarbons)
CFC’s are usually very stable molecules
But, in the high stratosphere, UV radiation breaks them down.
Thus releasing free chlorine atoms, which are very reactive.
The free chlorines break apart ozone molecules.

23. Therefore, MORE UV RADIATION reaches the earth.
CFC’s enter the stratosphere. UV radiation hits the CFC molecules.
UV radiation causes the Chlorine atoms to separate from their CFC molecules.
The free Chlorine atoms bond to oxygen atoms that are part of ozone molecules.
The ozone layer is depleted as more ozone molecules are broken apart. 
Therefore, MORE UV RADIATION reaches the earth.
The Chlorine atoms remove an oxygen atom from the Ozone molecules, breaking apart the ozone molecules
Free chlorine atoms continue moving around the stratosphere, breaking apart more and more ozone molecules.

24. Explain how CFC’s are depleting the ozone layer. [5]

25. Replace – Regulate – Restore Model
Replace CFC’s with CO2, propane, or air
Replace aerosols with pump action sprays
Replace methylbromide pesticides with something other than greenhouse gases
Don’t use aerosol hair products or deodorant

26. Replace – Regulate – Restore Model
Require a switch to HCFC’s because they don’t persist as long in the atmosphere;
(They are still harmful to the ozone layer…just less so)
Create laws to require that old refrigerators are returned to manufacturers to recover harmful materials inside
Capture CFC’s from scrap cars AC units

27. Replace – Regulate – Restore Model
Remove chlorine from the stratosphere or add ozone (not exactly feasible!)
Allow the ozone layer to slowly replenish itself as long as we continue to ban ODS’s

28. International Organizations and Agreements
How do we regulate all countries from using ODSs?
UNEP - United Nations Environmental Programme
Key role in:
Providing information on air pollution
Creating and evaluating international agreements
Brought together the countries that formed the Montreal Protocol!
Protection of stratospheric ozone

29. International Organizations and Agreements
Montreal Protocol 1987
International agreement for the reduction of ODS use.
National governments made laws and regulations aimed at reducing consumption and production of ODS (CFCs in particular)
There have been many updates to the Montreal Protocol, that have made it even more effective

31. The Montreal Protocol - 1987
VERY significant because:
Best example of international cooperation on an environmental issue.
Example of the precautionary principle in science-based decision making.
Experts from many different fields came together to research a problem and find solutions.
The first to recognize that different countries could phase- out ODS chemicals at different times depending on their economic status. (LEDC’s were given more time)
The first with regulations that were carefully monitored.
Had updates to the agreement, which made it more effective

32. The Montreal Protocol - 1987
Precautionary principle - in environmental matters, the theory that if the effects of a product or action are unknown, then
the product should not be used
or the action should not be taken