1. Stratospheric Ozone
Holy Ozone!

2. What is Ozone? Ozone Found in 2 layers of the atmosphere
A molecule made up of 3 oxygen atoms
Blocks incoming ultraviolet radiation and protects life
Found in 2 layers of the atmosphere
Troposphere (bad!)
Stratosphere (good!)
Highest concentrations between 20 and 40 km
Very thin layer (only about 1-10 ppm)
Dynamic Equilibrium
Ozone is constantly formed and
destroyed
UV radiation is absorbed in both
formation and destruction of ozone

3. Stratospheric Ozone and Ultraviolet Radiation (UVR)
UV-A: least dangerous, 315nm to 400nm
UV-B: 280nm to 315nm (ozone layer absorbs about 50%)
UV-C: most dangerous, 100nm to 280nm. Ozone layer absorbs most of this (more than 99%)

4. Who cares about UV? Good Stuff Bad Stuff
Stimulates production of vitamin D (prevents rickets)
Can be used to treat skin diseases like vitiligo or psoriasis
Can be used to sterilize
Industrial uses
Bad Stuff
Genetic Mutations
Damage living tissues
Cataract formation in eyes
Skin cancer
Suppresses immune system
Damages phytoplankton
Damages zooplankton

5. An Ozone Hole? Been measuring ozone since the 1950s
Discovered that the amount of ozone decreased significantly in the Spring (Sept./Oct.) and then increases again in Nov.
Despite annual cycles the hole appeared to be growing
In the last 30 years the minimum thickness has reduced drastically
one Dobson unit being equivalent to a layer of pure ozone 0.01 mm thick at standard temperature and pressure

6. Ozone Depleting Substances
Most ozone depletion is caused by
human made chemicals
Halogenated organic gases
A few others
CFCs
Developed during the 1930s
Inert at ground level (seemed brilliant!)
Used as…
Propellants in aerosols
Pesticides
Gas blown plastics
Flame retardants
refrigerants
1 chlorine from CFC can convert
100,000 molecules of ozone to oxygen
Takes CFCs years to reach the
stratosphere
animation

7. Reducing ODS “Replace, Regulate, and Restore” The Montreal Protocol
Even before any government action, much of the general public began to boycott products containing CFCs causing the spray can industry to respond
UNEP (United Nations Environmental Programme) created the Montreal Protocol in 1987
International agreement to phase out ODS
LEDCs were given more time to comply/implement treaty
197 countries ratified it (all of them at the time)
One of the most successful international agreements to date

8. Reducing ODS