1. Earth’s Atmosphere and the Ozone Layer

2. Earth’s Early Atmosphere

4. The Atmosphere “Blanket” of gases surrounding the Earth
Absorbs energy from the sun
Recycles water & other chemicals
Protects from high-energy radiation
Protects and supports life
Atmospheric Composition
(What it’s made of)
78% Nitrogen
21% Oxygen
<1% Argon
0.038% Carbon Dioxide
Trace (Minute) Amounts:
Helium, Neon, Methane, Hydrogen, Ozone, Water Vapor

5. 3 oxygen molecules bonded together.
What is Ozone?
Ozone =
3 oxygen molecules bonded together.

6. The Ozone Layer is in the Stratosphere

8. Ozone is a “double-edged sword”
At the earth’s surface - can be dangerous. It is corrosive and harmful to breathe in. And considered a form of air pollution.
In the lower stratosphere - it protects from the sun’s harmful UV rays.
Without ozone - too dangerous to walk outside without having to wear a special suit. 

9. Ozone in the troposphere1
Ozone is a naturally occurring gas found in the troposphere and other parts of the atmosphere.
It is found in low concentrations at ground-level.
Two major sources:
NITROGEN OXIDES:
RELEASED BY PLANTS AND SOIL
OZONE FROM THE STRATOSPHERE:
MIGRATES DOWN TO EARTH’S SURFACE 2
Ozone forms naturally in the troposphere when Nitrogen Dioxide is split by sunlight.
The freed oxygen bonds with O2 molecules to make ozone.
These reactions BALANCE each other. 3

10. Additional OZONE in the TROPOSPHERE is considered pollution.
It’s produced when nitrogen oxides (NOx)
and volatile organic compounds (VOC) interact with sunlight. 
The amount of ozone present in the troposphere varies from day to day and from place to place

11. VOCs : Volatile Organic Compounds
NOx: Nitrous Oxides
natural sources vs man-made sources
animal manure intentional burning of crops
Chemical processes in soil automobiles
Lightning sewage treatment Forest fires burning fossil fuels
VOCs : Volatile Organic Compounds
produced by a variety of sources
fossil fuel refining and combustion
thousands of industrial chemical products.
Plants/bacteria processes in soil

12. Breathing in ground-level ozone can be harmful to your health.
Who is most at risk?
People with asthma or other lung diseases
Older adults
People of all ages who exercise or work hard outside
Babies and children

13. Air Quality Index (AQI)
number used by government agencies to communicate to the public how polluted the air currently is or how polluted it is forecast to become

14. ** Ozone is
good up high,
But bad
Nearby**

15. What is Ozone (O3) in the stratosphere?
3 Oxygen Atoms bonded together
Performs critical function to life on Earth
Filters/Shields UV radiation from the sun
Absorbs UVA and UVB radiation
Can be found in the troposphere and stratosphere
Oxygen (O2) absorbs UVC wavelengths.
Ozone (O3) absorbs UVA and UVB wavelengths

16. HOW IS IT MADE??

17. Humans need a small amount of UV Radiation to maintain health.
UV radiation activates vitamin D in the human body.
VITAMIN D:
assists intestines in absorbing minerals.
(Ex: Calcium and Phosphorous)
Which play a crucial role in:
Skeletal development
Immune function
Blood cell formation
used to successfully treat a number of diseases
(Rickets, Psoriasis, Eczema, and Jaundice)
5 to 15 minutes of sun exposure (hands, face and arms) 2-3 times a week during summer is enough to keep your vitamin D levels high

18. 3 Types of UV Wavelengths: UVC – shortest wavelength
UVA – longest wavelength
UVB- middle wavelength
We cannot see or feel UV radiation
UVA
goes deep into the skin.
It can cause long-term damage like wrinkles, blotchiness, sagging and skin cancer. 
UVB
Effects top layer of skin.
Can cause sunburn, skin damage and skin cancer.
Changes the shape of DNA molecules 
UVA and UVB wavelengths
cause 65% to 90% of melanoma of the skin
(accounts for ¾ of all skin cancer deaths)

19. Remain chemically active in the atmosphere for decades
Chloroflurocarbons
(Chlorine, Flourine, Carbon)
Man-made
Commercial &
Consumer Applications:
refrigeration, air conditioning, foam production, aerosol propellants, and circuit board cleaning.
Halons:
Synthetic (man-made)
Chemicals used to extinguish fires
Stable
Long-lived
Remain chemically active in the atmosphere for decades

20. How do CFCs Destroy Ozone Molecules??
O3 molecules interact with CFC’s and Halons
They DESTROY molecular bonds of O3
ONE Chlorine molecule can eliminate 100,000 O3 molecules
Halons are even more potent O3 destroyers than CFCs

21. Ozone Formation and Depletion

22. Volcanic particles settle out of the atmosphere in 2-3 years
Volcanoes RELEASE Hydrogen Chloride (HCl)
They account for 3% of Chlorine in the stratosphere
HIGH Amounts of Hydrogen chloride (HCl) can deplete Ozone
At least two factors reduce the impact of HCl...
Chlorine appears to be released during low-levels of volcanic activity. Limiting it to the troposphere, where it is most likely to be washed out by rain
Hydrogen chloride may also condense in the rising volcanic plume, again to be scrubbed out by rain or ice
Effects from volcanoes are short lived, when emitted into the troposphere.
Volcanic particles settle out of the atmosphere in 2-3 years

23. Death of phytoplankton Disrupts food chain Reduces photosynthesizers
Humans:
Increased incidences of skin cancer
Premature aging of the skin
Sunburns
Increased incidences of cataracts
Weakened immune response
Ozone Depletion Leads to Increased UV Radiation
Effects of Ozone Depletion on Plants and Animals
Plants:
Interferes with photosynthesis
Reduced disease resistance
Reduced crop yields
Interferes with DNA
Marine Life:
Death of phytoplankton
Disrupts food chain
Reduces photosynthesizers

25. considered by many the most successful environmental global action.
Montreal Protocol (1987):
Mid 1980s, concerns grew over what appeared to be a ‘hole’ in the ozone layer
over Antarctica in spring
smaller hole over the Northern Hemisphere
Scientists determined it was caused by humans due to man-made chemicals (CFCs)
Signed by 197 Countries
1st treaty in the history of the United Nations to achieve universal ratification.
considered by many the most successful environmental global action.
US signed in 1987
In 1995, the UN named September 16 - International Day for the Protection of the Ozone Layer.

26. THE GOAL:
Reducing/stopping the production of CFCs.
Provided a double benefit:
stopping ozone depletion
slowing the growth of greenhouse gases.
ISSUES:
Many substitutes for ozone depleting substances are ozone safe, BUT many are powerful greenhouse gases.
They have the potential for offsetting climate gains currently achieved by the Montreal Protocol.

27. HFC – Hydrofluorocarbons: The alternative to CFCs
synthetic organic compounds 
composed of hydrogen, fluorine, and carbon.
used as alternatives to ozone depleting substances
**They became widely used as refrigerants (late 1980’s) due to the Montreal Protocol. 
NOW THERE’S A NEW PROBLEM: HFCs are potent greenhouse gases.
Atmospheric observations show that the volume of HFCs in the atmosphere is increasing rapidly, about 10-15% per year.

28. The Ozone is on the ROAD to RECOVERY