OZONE DEPLETION

Videos

NASA 12009 “hole”

Weather Ch.

Stratosphere: GoodBlocks UV radiation

Damages human health and welfare

Troposphere: Bad

The ozone layer is in the Stratosphere

The ozone layer blocks 95-99% of the sun’s Ultraviolet Radiation

UV Radiation has negative effects• O3 Depletion causes higher UV Radiation which

causes:– Sunburn– Skin Cancer– Eye Cataracts– Weakened Immune System– Reduced crop yield– Damages to marine ecosystem, etc.– More photochemical smog to form (including O3)

Link to EPA Site on Effects

Ozone Formation

• Oxygen in Troposphere makes it into Stratosphere.

• UV radiation in stratosphere converts O2 to O3.

Ozone Formation

Troposphere

Stratosphere

O2

UV

O2

O2Oxygen in troposphere goes into stratosphere

Ozone Formation

Troposphere

Stratosphere

UV

O OO2

O2

UV breaks O2 into two atomic oxygens (O)

Ozone Formation

Troposphere

Stratosphere

O2

UV

O2

O3

O3

The atomic O binds with O2 to make O3 (ozone)

Ozone Destruction• Cause: CFCs and other Chlorine-

and Bromine-containing molecules– Used for aerosol spray cans,

Styrofoam inflation, air conditioners and refrigerators (Freon), pesticides, and other industrial processes.

Link to EPA site of ozone-depleting substances

Ozone Destruction

Troposphere

Stratosphere

O2

UV

O2

O3

CFCs travel into stratosphere

CFC

Ozone Destruction

Troposphere

Stratosphere

O2

UV

O2

O3

UV breaks off a Chlorine atom

Cl

Ozone Destruction

Troposphere

Stratosphere

O2

UV

O2

ClO

The Chlorine atom takes an O atom from ozone, converting ozone to chlorine monoxide and oxygen O2

Ozone Destruction

Cunningham/Cunningham 2002 text

Where is Ozone Depletion?• Everywhere: Global thinning

– E.g.: US sees 5-10% drop– Note: this is enough to significantly

increase skin cancer, etc.• Highest over Antarctic (also Arctic)

– Polar vortex, cold temps, long winter produce polar stratospheric clouds upon which reactions occur.

– Where the so-called ozone hole occurs (where ozone less than 220 dobson units – a 70% reduction; normal is 250-475+).

Increasing Ozone Depletion

                                      

http://ozonewatch.gsfc.nasa.gov/

“a column ozone level of less than 220 Dobson Units is a result of the ozone loss from chlorine and bromine compounds”

Ozone Hole on 11/8/08

When is Ozone Depletion Highest?• Spring when sunlight first hits

because sunlight causes the reaction that breaks down the O3.

• Remember Spring in the Antarctic is during our Fall (especially Oct).

Link to EPA site of ozone hole animation

Ozone Depletion Solutions• Montreal Protocol: international treaty

– 1987: reduce CFC use by half by 2000– 1990: goal to cut in half by 1995– 1992: US law eliminated by end of 1995

Ozone Depletion Reference

http://www.esrl.noaa.gov/csd/assessments/2006/report.html