Mark Ewoldsen, Ph.D.

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Ozone Hole

• Mark Ewoldsen, Ph.D.
• Advanced Placement Environmental Science Teacher
• La Cañada High School

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Two Atmosphere Layers

• Stratosphere is above Troposphere
• Ozone Layer blocks UV radiation
• Troposphere is where we live
• Weather occurs here
• 72 of all air is below the cruising altitude of
  commercial airliners (33000 ft)

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• Stratospheric Ozone
• (Good)
• vs.
• Tropospheric Ozone
• (Bad)

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Ozone Two Faces

• Stratosphere Good Ozone
• Blocks UV radiation
• Hole caused by depletion due to CFCs
• Troposphere Bad Ozone
• Pollution
• Photochemical smog
• Eye irritant

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Harmful effects of UV radiation

• Skin cancer such as melanoma(ultraviolet
  radiation can destroy acids in DNA)
• Suppression of immune systems

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matrix.ucdavis.edu/tumors/tradition/
gallery-ssmm.html
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Harmful effects of UV radiation

• Skin cancer such as melanoma(ultraviolet
  radiation can destroy acids in DNA)
• Suppression of immune systems
• Cataracts and sun burning

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www.snec.com.sg/clinical_services/ cataract.asp
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http//www.wep.org.au/info/files/images/Amelia_and
_the_kids.jpg
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Harmful effects of UV radiation

• Skin cancer such as melanoma(ultraviolet
  radiation can destroy acids in DNA)
• Suppression of immune systems
• Cataracts and sun burning
• 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

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GoodOzone
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Ozone Formation

• Ozone forms a layer in the stratosphere, thinnest
  in the tropics (around the equator) and denser
  towards the poles.

• O2 hv ? O O
• (1) O O2 ?O3
• wavelength 240 nm

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http//www-imk.fzk.de/topoz-iii/ataglanz/ozonbild.
html
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http//www-imk.fzk.de/topoz-iii/ataglanz/ozonzerst
.html
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Natural Ozone Hole

• Winter no sunlight
• Air in the polar vortex can get very cold -80C
• Special clouds called Polar Stratospheric Clouds
  form as nitric acid trihydrate
• PSCs are crucial for ozone loss to occur

Since there is no sunlight, the air within the
polar vortex can get very cold
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The ozone hole builds up over the winter months,
peaking at around September and breaking up again
by December, this data set from 2005
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Destroying Good Ozone
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Destroying Good Ozone

• Chloroflourocarbons were first created in 1928 as
  non-toxic, non-flamable refrigerants, and were
  first produced commercially in the 1930's by
  DuPont
• In 1974, a laboratory study demonstrated the
  ability of CFC's to catalytically breakdown Ozone
  in the presence of high frequency UV light
• Cl O3 -gt ClO O2 ClO O3 ---gt 2 O2 Cl
• In a 1985, a study summarized data that had been
  collected by the British Antartic Survey showing
  that ozone levels had dropped to 10 below normal
  January levels for Antarctica.
• http//www.nas.nasa.gov/About/Education/Ozone/hist
  ory.html

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A single chlorine atom removes about 100,000
ozone molecules before it is taken out of
operation by other substances
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The frozen crystals that make up polar
stratospheric clouds provide a surface for the
reactions that free chlorine atoms in the
Antarctic stratosphere
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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
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http//www.clas.ufl.edu/users/dlsmith/Lecture_11.h
tml
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http//www.mmscrusaders.com/newscirocks/ozone/cfc.
jpg
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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)
• 1995 (Vienna)
• 1997 (Montreal)
• 1999 (Beijing)

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Area of North America
Area of Antarctica
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