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OZONE LAYER DEPLETION

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OZONE LAYER DEPLETION. Why the hole in the atmospheric ozone layer above us? ... Unlike oxygen (O2), ozone has a strong scent and is blue in color. ... – PowerPoint PPT presentation

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Title: OZONE LAYER DEPLETION


1
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?

2
Good life at the beach threatened?
  • Mr. OZONE Will I be able to continue
    enjoying this life without problems?

3
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.

4
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

5
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.

6
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.

7
The ozone depletion process
8
Responsibility for ozone damage each year
9
Global CFC production
10
(No Transcript)
11
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).

12
Ozone hole size by month
13
Ozone hole measurements over the Antarctic region
1980-98
14
Ozone concentration at the center of ozone hole
15
Ozone hole over continents comparison 1996
16
Image of the ozone hole over the South pole July
10 2003
17
Image of the ozone hole over the North pole July
10 2003
18
Ozone status full day global image, July 9th 2003
19
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.

20
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

21
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

22
Correlation between Ozone depletion and skin
diseases
23
The Ultraviolet Exposure Index
INDEX VALUES EXPOSURE 0 2
Minimal 3 - 4 Low 5
- 6 Moderate 7 - 9
High 10 Very High
24
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.

25
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.

26
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.
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