1. 02/23 Turn in your Homework! “The World We Create” NATS 101 Section 6

2. Project 1 Mean 88.4% SD 10% 86.6% 87.5% 87.7% 87.7% 88.2% 89.2% 89.5% 89.9% 90.1%

3. UNIT 1

4. UNIT 2: Environmental changes, Natural or Man-Made? UNDERSTANDING OZONE DEPLETION

5. Ozone Layer Last class we talked about the importance of the Ozone Layer for life in our planet.

6. 95% penetrates 5% penetrates 0% penetrates

7. Ozone Cycle Recap. 2 O 3 3 O 2 UVB Natural destruction of Ozone: UVB absorbed! 3 O 2 2 O 3 Natural formation of Ozone: UVC absorbed! UVC Let’s analyze what you understood!

8. Each small group will need 1 bag that includes: Marsh mellows Gumdrops Tooth picks 1 white board per letter team. GOAL: To Model the Cycle of destruction an formation of O 3. 2 O 3  3 O 2 3 O 2  2 O 3 UVB UVC

9. If marsh mellows represent oxygen molecules, and tooth picks are chemical bonds:  Use these materials to model the cycle of destruction and formation of O 3. You need to build a sequence of at least five 3D-frames (a single one of a series of still models) that shows the whole process.  After your group is finished, let your TAs know. They will select a group that will draw the set of frames on a whiteboard to show to the rest of the class. You 5 minutes

10. 2 O 3  3 O 2 3 O 2  2 O 3 UVB UVC You need at least 5 frames! One group will write it on a white board for your team.

11. Destruction Formation The Natural Cycle There is evidence that shows that pollutants released by humans are interfering with this cycle.

12. An ozone hole? Concern about thinning of the ozone layer over Antarctica arose in the 1970’s but it was not monitored until in the 1980s We know the amount of O 3 is changing 1 Dobson Unit = 0.01 mm at 0 o C, 1 atm

13. The Evidence The presence of chlorine atoms Cl and ClO molecules is inversely correlated with O 3 concentration. Cl

14. Sources of chlorine Where are CFC’s found?  Foaming agents for plastics  Solvents for cleaning  Aerosol propellants  Refrigerants  Fire extinguishers Main source CFC’s: chlorofluorocarbons

15. CFCs are handy  Nontoxic;  Not flammable;  Stable in the Troposphere  unreactive;  Many different forms so they have many different applications.

16. UVC Cl Action UVC produces very reactive Cl atoms that affect the natural cycle of O 3 formation-destruction. Cl Radical Cl + 2 O 3  3 O 2 + Cl

17. If marsh mellows represent O, Gumdrops represent Cl, and toothpicks represent Chemical bonds:  Model how Cl atoms may be affecting the cycle of formation and destruction of O 3. You need to build a sequence of four 3D-frames that show the effect of Cl atoms.  Discuss why the action of Cl is SO problematic. Cl Action  After your group is finished, let your TAs know. They will select a group that will draw the set of frames on a whiteboard to show to the rest of the class. You 10 minutes

18. Cl + 2 O 3  3 O 2 + Cl Cl 2 O 3 Cl 3 O 2 Hint: ClO is formed in the process  Discuss why the action of Cl is SO problematic. The sequence should have at least 4 frames (Including beginning and end)

19. CFCs in the Stratosphere CFCs take on average fifteen years to reach the stratosphere, and they can remain in the atmosphere for up to one hundred years. However, once there, one single Cl. radical can destroy over 100,000 ozone molecules!

20. Cl Action

21. The Effects The largest area of diminishing ozone has been documented in the stratosphere over Antarctica since the 1980s.

22. Here is a NASA movie of the ozone “hole” over Antarctica from July through December: What is happening in Antarctica?

23. Average Size

24. Size and Seasons This graph shows the area of ozone depletion in Antarctica.  What is it telling us about the time of year when the area of ozone depletion is greatest?

25. Artic vs. Antartic

26. Why the Antarctic? What are these data telling us about the relationship between: temperatures, seasons, and sunlight in the Arctic and Antarctica?

27. Your Ideas In your groups discuss the relationships that you see among temperature, seasons, sunlight, and area of ozone depletion.

28.  How has the area of the ozone hole over Antarctica changed in the past 25 years?  How does it change with seasons? How do you explain it?  What differences do you observe between Antarctic ozone and Artic ozone? What may explain the difference? Discussion

29. What has been done? Ozone can be rebuilt if active pollutant agents are eliminated from the atmosphere Legislation  1980s: US banned the use of CFCs in aerosol cans  1987: Montreal Protocol  many nations agreed to stop use of CFCs and replace them with alternatives such as HCFCs  Clean Air Act: Amended to include “Ozone Protection Program”

30. Recovery? Estimated ozone recovery: Up to 100 years from 2006 2045-2060 Estimate of the amount of ozone remaining: ~58% +/- 5% Beginning of Ozone Recovery: ~15 years after decrease in CFC production: 2005-2010

31. Wrap-up: How are they related? Build as many connections between these concepts. CLEARLY STATE THE CONNECTION USING A VERB OR PHRASE. OZONE UVA UVB UVC CFC STRATOSPHERE OZONE DEPLETION SKIN CANCER OZONE UVC blocks