1. Ozone Hole

2. Understanding Ozone http://royal. okanagan. bc
Discovered in 1839 by German scientist Christian Friedrich Schonbein
Pale blue, unstable molecule made of three oxygen atoms
Vital to life in the stratosphere
Harmful to plants and humans in the troposphere
Concentration: stratosphere  up to 15 ppm at about 25 km
Formed when atomic oxygen (O) from higher parts of the atmosphere collides with molecular oxygen (O2) in the stratosphere
UV radiation splits the ozone back to O and O2 and it can form another ozone molecule

5. The Ozone Hole
First discovered in 1985: observations from Antarctica extend back into 1950’s.
Characterized as a rapid depletion of ozone over Antarctica during spring.
Ozone hole season, Spring (August – October)
Ozone hole located over mainly over Antarctica.
Ozone hole recovers by late December
Ozone hole caused by human chemicals (CFC’s)
Ozone hole not present in early 1970’s
Observations over Antarctica data back to the 1950’s. The discovery of the ozone hole occurred in It turns out that the research group measuring ozone had seen a sharp decline in ozone levels during October over Antarctica (see next overhead), but didn’t report it immediately because they worried that their instrument might be faulty. Finally, after a few years of testing, they published a paper documenting this rapid decline of ozone levels. However, at the time, there was no explanation for why ozone was declining.
During that same time period, NASA was also observing ozone levels globally. However, they didn’t expect to see signs of ozone depletion over Antarctica, and consequently, ‘missed’ the ozone hole due to a computer glitch. When they realized their mistake, and fixed up the computer problem, they also saw the clear signs of an emerging hole in the ozone layer.
The ozone hole is characterized by a rapid depletion of ozone over Antarctica during the springtime.
The science of the ozone hole was well understood by the early 1990s.

7. (Key Learning Figure)
Many students (and the public) have the perception that the ozone hole (and ozone in general) is getting much worse. This is likely due to press reports that usually say, ‘the ozone hole reached it’s largest size…’ The reality is that in the last decade, the size and severity of the ozone hole have stayed about the same, compared to rapid changes seen in the middle 1980’s.
Year to year variations in the depth and severity of the ozone hole is really a function of the atmospheric weather conditions (I.e. the colder the winter, the more greater the ozone loss). In addition, the ozone hole is about as bad as it can get. Between km, all the ozone is essentially destroyed during spring over Antarctica, so it couldn’t get much worse. Thus, we don’t expect the size and depth of the ozone hole to change dramatically in the future. Rather, it is expected that the size of the ozone hole is about as big as it’s going to get, and with time (10 or more years) and reduced chlorine levels, we should start to see the size of the ozone hole get smaller.
Thus, this graphic is intended to illustrate how in the 80’s, the size of the ozone hole increased rapidly, while in the 90’s and 2000, things stabilized.

8. science.widener.edu/svb/ atmo_chem/oct15.html

10. Ozone hole stabilizes October 17, 2001
WASHINGTON (CNN) A hole in the Earth's protective ozone layer
is about the same size as in the past three
years, according to scientists at the National
Oceanic and Atmospheric Administration,
who predict it will hold steady in the near
future.
Satellite data show the hole over Antarctica,
which allows more harmful solar radiation to
reach the Earth, peaked this year at about 10
million square miles (26 million square km),
roughly the size of North America.

12. History of Ozone Depletion
CFCs developed in 40’s and 50’s
Refrigerants, propellants, fire retardants
1970’s CFCs detected in atmosphere.
Many of these have long atmospheric lifetimes (10’s to 100’s of years)
1974 Rowland and Molina propose that CFC’s can destroy ozone in the stratosphere.
CFCs broken apart by UV radiation forming chlorine which can destroy ozone quickly:
O3 +Cl  ClO+ O2 (Catalytic Reaction)
ClO+O  Cl+O2
(advanced)
CFC’s are a class of chemicals that were developed in the 40 and 50s for many valuable applications including refrigerants, propellants (for spray cans) and fire retardants. One of the most remarkable and extremely valuable characterizes of CFC’s is that they do not react anything. Therefore, if you have some type of fire, you can safely use CFC’s to extinguish the fire, not worrying if your fire retardant is going to enhance the fire.
This characteristics of CFC’s also means that many CFC’s remain in the atmosphere for many years (10’s to 100’s). They have long atmospheric lifetimes. Therefore, if you release a CFC molecule into the atmosphere, it may bounce around in the atmosphere for many many years.
In 1974, two scientist (Rowland and Molina; who later received the Nobel Prize in chemistry) suggested that because CFC’s are around for a long time, they may eventually reach the upper atmosphere, where they can be broken apart by the sun. CFC’s contain chlorine, a chemical that can rapidly destroy ozone under certain conditions, and in some cases, a single chlorine atom may destroy thousands of ozone molecules through a self replicating cycles (catalytic reaction).
The catalytic cycle is self replicating…ozone gets converted by chlorine, producing ClO and more oxygen. The ClO then reacts with a free oxygen atom, thereby producing another Cl atom. The cycle can then continue again.

13. Chlorofluorocarbons or CFCs
First produced by General Motors Corporation in 1928, CFCs were created as a replacement to the toxic refrigerant ammonia
CFCs have also been used as a propellant in spray cans, cleaner for electronics, sterilant for hospital equipment, and to produce the bubbles in Styrofoam

14. CFCs are cheap to produce and very stable compounds, lasting up to 200 years in the atmosphere
Many countries have recently passed laws banning nonessential use of these chemicals.
Nevertheless, by 1988 some 320,000 metric tons of CFCs were used worldwide.

17. Action of CFCs
CFCs created at the Earth's surface drift slowly upward to the stratosphere where UV radiation from the sun causes their decomposition and the release of chlorine
Chlorine in turn attacks the molecules of ozone converting them into oxygen molecules
Cl + O3 »»» ClO + O2
ClO + O »»» Cl + O2

18. 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

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

21. Low and Middle Latitudes
Current measurements indicate that the amount of ozone in the stratosphere of the low and middle latitudes has decreased by about 3% with estimates that it will decrease by10% by 2025

22. Harmful effects of UV radiation.
Skin cancer (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

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

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

25. Conclusion
Ozone Depletion Exists and effects certain areas of the Earth more than others
Currently, one in five North Americans and one in two Australians will develop some form of skin cancer in their lifetime
With a sustained 10% decrease in stratospheric ozone, an additional 300,000 non-melanoma and 4,500 melanoma skin cancers could be expected world-wide, according to UNEP estimates.

26. Natural Capital Degradation Effects of Ozone Depletion
Human Health
Worse sunburn
More eye cataracts
More skin cancers
Immune system suppression
Food and Forests
Reduced yields for some crops
Reduced seafood supplies from reduced phytoplankton
Decreased forest productivity for UV-sensitive tree species
Wildlife
Increased eye cataracts in some species
Decreased population of aquatic species sensitive to UV radiation
Reduced population of surface phytoplankton
Disrupted aquatic food webs from reduced phytoplankton
Air Pollution and Materials
Increased acid deposition
Increased photochemical smog
Degradation of outdoor paints and plastics
Global Warming
Accelerated warming because of decreased ocean uptake of CO2 from atmosphere by phytoplankton and CFCs acting as greenhouse gases

27. 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) accelerated the phasing out of key ozone- depleting chemicals.
1995 (Vienna)
1997 (Montreal)
1999 (Beijing)

28. Ozone Depleting Chemicals
Chlorofluorocarbons (CFCs)
Halons
Methyl bromide
Carbon tetrachloride
Methyl chloroform
Hydrogen chloride

29. Former Uses of CFCs Air Conditioners Refrigerators Spray cans
Cleaners for electronic parts
Sterilizing medical instruments
Fumigants for granaries and cargo ships

30. Solutions: Protecting the Ozone Layer
CFC substitutes
Montreal Protocol
Copenhagen Protocol
Fig p. 489