OZONE LAYER DEPLETION

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OZONE LAYER DEPLETION

• Why the hole in the atmospheric ozone layer above
  us
• What has been done about this
• Why should I worry ourselves about the Ozone
  Layer Depletion

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Good life at the beach threatened

• Mr. OZONE Will I be able to continue
  enjoying this life without problems

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What is Ozone Ozone Layer

• Ozone (O3) is a highly-reactive from of oxygen.
• Unlike oxygen (O2) ozone has a strong scent and
  is blue in color.
• Ozone exists within both the tropospheric and
  stratospheric zones of the Earths atmosphere
• In the troposphere ground level ozone is a major
  air pollutant and primary constituent of
  photochemical smog
• In the stratosphere the ozone layer is an
  essential protector of life on earth as it
  absorbs harmful UV radiation before it reaches
  the earth.

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CFCs and ozone depletion

• Chlorofluorocarbons are created and used in
  refrigerators and air conditioners. These
  chlorofluorocarbons are not harmful to humans and
  have been a benefit to us. Once released into the
  atmosphere chlorofluorocarbons are bombarded and
  destroyed by ultraviolet rays. In the process
  chlorine is released to destroy the ozone
  molecules

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Destruction of ozone by chlorine

• Molecular oxygen is broken down in the
  stratosphere by solar radiation to yield atomic
  oxygen which then combines with molecular oxygen
  to produce ozone. The ozone is then destroyed by
  chlorine atoms.

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Ozone destruction by UV rays

• UV radiation from the sun releases the radicals
  Cl and ClO.
• Ozone is a highly unstable molecule so it readily
  donates its extra oxygen molecule to free radical
  species such as hydrogen bromine and chlorine.
• These compound species act as catalysts in the
  breakdown of ozone molecules.

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The ozone depletion process
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Responsibility for ozone damage each year
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Global CFC production
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(No Transcript)
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Ozone hole in Southern hemisphere October 1979
1998

• Monthly means of total ozone in the Southern
  Hemisphere observed with TOMS
• Images for October of 1979 (left) and 1998
  (right).

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Ozone hole size by month
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Ozone hole measurements over the Antarctic region
1980-98
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Ozone concentration at the center of ozone hole
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Ozone hole over continents comparison 1996
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Image of the ozone hole over the South pole July
10 2003
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Image of the ozone hole over the North pole July
10 2003
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Ozone status full day global image July 9th 2003
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Effects of UV rays on Aquatic Ecosystems

• Ozone depletion causes increases in UV rayss
  effects on aquatic ecosystems by
• 1. decreasing the abundance of phytoplankton
  affects the food stock for fishes and the
  absorption of CO2
• 2. decreasing the diversity of aquatic organisms
  reduces food stock and also destroys several
  fish and amphibians.

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Effects of UV rays on Terrestrial Ecosystems

• Damage to plant cell DNA molecules - makes plants
  more susceptible to pathogens and pests
• Reductions in photosynthetic capacity in the
  plant - results in slower growth and smaller
  leaves
• Causes mutations in mammalian cells and destroys
  membranes

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Harmful effects of UV rays on people

• Skin cancer
• Premature aging (photoaging) of the skin
  (different from normal chronological aging)
• Cataracts and eye disorders (corneal sunburn and
  blindness)
• Immune system damage

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Correlation between Ozone depletion and skin
diseases
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The Ultraviolet Exposure Index
INDEX VALUES EXPOSURE 0 2
Minimal 3 - 4 Low 5
- 6 Moderate 7 - 9
High 10 Very High
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Factors affecting UV exposure

• Clouds cover - partly cloudy days do little to
  reduce UV exposure but rainy or substantially
  overcast days reduce UV exposures
• The time of day peak exposure time is 1200
  noon - 100 p.m. UV intensity is reduced by about
  half at three hours before and three hours after
  the peak exposure time.

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Factors affecting UV exposure..2

• The time of year - more UV is received in the
  late spring and early summer and much less is
  received in the late fall and early winter.
• Life style determines a persons risk to UV
  exposure. Skiing sunbathing or swimming can
  lead to extremely high exposures. Use of tanning
  parlors also increase risk.

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Policy responses to Ozone depletion

• Mario Molina and Sherwood Rowland showed in 1974
  that CFC gases destroy ozone
• Coordinating committee on Ozone Layer (CCOL)
  established by UNEP in the 1970s
• Vienna Convention for the protection of the ozone
  layer held in 1985
• Montreal Protocol to ban substances that deplete
  the ozone layer held in 1987
• Amendments to the Montreal Protocol London -
  1990 Copenhagen - 1992 and Montreal - 1997.