1. Recall – quick questions 1.In which 2 layers of the atmosphere is ozone found? 2.Where is it considered “good” and “bad”? Why? 3.What happens to the structure of the atmosphere as you move away from earth? 4.How does ozone absorb UV light? 5.Why is it important for ozone to absorb UV light?

2. Learning outcomes All of you should be able to: Identify that halogenated organic gases that reduce the rate of ozone reformation Most of you should be able to: Describe methods for reducing the manufacture and release of ozone-depleting substances. Some of you might be able to: Explain the interaction between ozone and halogenated gases.

3. Chlorofluorocarbons (CFCs) Developed during the 1930s and used extensively in aerosols, air conditioners, refrigerators, solvents and gas-blown plastics. They are extremely stable and inert and were used to replace earlier coolants that caused explosions. In the troposphere they are indestructible and insoluble in water, however…

4. When CFCs meet Ozone…

5. Chlorofluorocarbons (CFCs) They remain in the troposphere for up to 100 years and ultimately make their way to the stratosphere which is where the damage starts!

7. Other ozone depleting substances (ODSs) Substances containing the halogens chlorine, fluorine and bromine. Most do not occur naturally and are industrial products or by-products. Examples: CFCs Hydrochlorofluorocarbons (HCFCs – replacement for CFCs) Halons (fire extinguishers) Methyl bromide (pesticide)

8. Quick quiz 1.Why were CFCs so popular for propellants and coolants? 2.Describe the steps in the breakdown of ozone by CFCs. 3.Describe how ozone is formed. 4.Marco was talking to Eugenio, “It is the hole in the ozone layer that is allowing heat from the sun to enter the atmosphere.” Comment on this statement. 5.Where is ozone found?

9. Reducing ozone depleting substances (ODSs) Using the “replace, regulate and restore” model of pollution management come up with some actions for reducing ODSs.

10. Replace – human activity Replace CFCs with carbon dioxide, propane or air as a propellant. Replace methyl bromide pesticides (some of these can be greenhouse gases e.g. chloropicrin or dazomet) Replace gas-blown plastics

11. Regulate – point of emission Recover and recycle CFCs from fridges and air conditioning units Legislate to have fridges returned to the manufacturer Capture CFCs from scrap cars (found in the cooling systems) Since 1993 Australia has collected 3000 tonnes of ODSs which have been either recycled, stored or destroyed.

12. Restore - clean-up Add ozone to or remove chlorine / bromine from atmosphere (not practical)

13. Checking outcomes 1.What halogenated gases reduce ozone? 2.How do they reduce it? 3.Describe one method from each strategy “replace, regulate, restore” to control ODSs.