1. APES 2/24 and 2/25
Please get a laptop and pull up your Ozone Depletion Assignment
It should be shared with me when class starts

2. Ozone Depletion

3. History of ozone thinning
1930’s – 1950’s: Discovery and increased use of CFC’s
1974 – Mario Molina and Sherwood Rowland hypothesized that CFC’s could deplete ozone
1985 – Hole in the ozone was confirmed by NASA and British Antarctica Survey
1987 – Montreal Protocol
Early 1990’s – Rate of thinning increases dramatically
Mid 1990’s – Substantial thinning detected in Arctic
2000 – highest atmospheric concentrations met

4. Stratospheric vs. Tropospheric Ozone
Troposphere= Bad
Secondary pollutant/smog
Stratosphere = Good
Protects from UV radiation

5. Types of Ultraviolet Radiation
UVA
UVB
UVC
Length/Energy
Longest/Least Energetic
Intermediate/ Medium Energy
Shortest/Very Energetic
Pathway to the Earth
Not absorbed by ozone/almost all reaches the Earth
Absorbed by ozone/reaches the Earth if not stopped by ozone
Absorbed by O2, causes it to break apart/rarely reaches the Earth
Damage to Living Things
Some Damage
Highly Damaging
UVB reaching the surface of the Earth is really THE problem associated with ozone depletion

6. Problems associated with UVB
Humans
Ecosystems
Sun Burn
Skin cancer
Eye cataract
Damage to immune System
Damages plant leaves
Damages algae in the ocean
Effects fish, amphibians, mammals
Ultimately whole food webs affected – Why?

7. Natural Formation/Destruction of Ozone with UVB
O3 + UVB  O2 + O
UVB’s energy absorbed to break bond in O3
Equilibrium is maintained as O3 reforms as quickly as it is broken by UVB
Process happens very quickly so if use bath tub analogy the level stays fairly constant, with UVB constantly being absorbed.

8. CFC’s disrupt equilibrium
CFC – Chloroflurocarbon (CCl3F)
Were in aerosols, coolants, Styrofoam
CFC’s have very long residence times
UVB releases chlorines from CFC’s
Creates a catalytic chain reaction
Upsets the balance, ozone is being broken apart and reformed but doesn’t absorb UVB in the process.

9. Catalytic Chain Reactions
CCl3F + UVB  3 Cl + CF
Cl + O3  ClO + O2
ClO + O  Cl + O2
Cl is the catalyst that is “free” to break apart more Ozone – chain reaction
Why is the equilibrium of stratospheric ozone disrupted?
More O2 than O3 is being created
Overall amount of O3 in the atmosphere decreases

10. Other Ozone Depleters
Halons- chemical containing Bromine that is used in fire extinguishers, wildfire suppression, dry cleaners
Methyl Bromide- agricultural chemical sprayed on fields to kill pests in soil
Both release Br- into the stratosphere, which reacts with O3 much like Cl- does

11. Why Poles are Thinner Polar Stratospheric Clouds!
Natural, high altitude clouds made of ice crystals and nitric acid
They bond with natural nitrates that usually would bond with Cl
Instead, the Cl is free to rip apart O3
When the clouds disappear, nitrates are released and re-bond with the Cl
The hole actually is the worst in September because the free chlorine has been building up all winter , it is still ad in October and November because it takes awhile for all of the nitrates to rebond with the cholinres

12. Why Poles are Thinner
Polar Vortex: persistent, Coriolis-caused cyclone of cold air at the poles
Extends into stratosphere
Traps Cl- and Br- in one concentrated area

13. Why September?
In the southern hemisphere, winter is June – August/September
Height of polar clouds and polar vortex
Polar stratospheric clouds begin to clear up in August, but it takes a while for the nitrates to re-bond the chlorines
When would the arctic ozone
hole be worst?

14. Montreal Protocol International agreement in 1987 to phase out CFC’s
Updated several times, to speed up timetable when extent of damage being caused was realized
Developed countries need to help developing countries with technology and money to accomplish phase out
Developed countries total phase out -2000
Developing countries total phase out – 2015
“Hole” expected to be back to normal by 2050

15. Alternatives to CFC’s Hydrofluorocarbons (HFC’s)
Contain fluorine rather than chlorine, which has a much shorter residence time
New cooling technologies using water vapor, hydrocarbons, ammonia

16. Ozone Depletion Assignment
Revise your answers based on your new knowledge and resubmit!
Don’t need the time? Start your current event (due Friday)
Please inventory your Current Events so far

17. Ozone FRQ You have 20 minutes until scoring! Good luck!
If you finish early, take a break 

18. Indoor Air Pollution Sensors
Build 2 pollution sensors following the diagram on the board.
You will hang them in two indoor locations and bring them back next Tuesday.
How could we get a quantitative measurement using this method?

19. Indoor Air Pollution Brainstorm
What do you think is lurking in your house?
Sometimes it is much more sinister…

20. Homework time
Inventory your current events with the provided half-sheet
Start Module 50 notes + end of mod and end of chapter multiple choice