Title: OZONE LAYER DEPLETION
1OZONE 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?
2Good life at the beach threatened?
- Mr. OZONE Will I be able to continue
enjoying this life without problems?
3What 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.
4CFCs 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
5Destruction 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.
6Ozone 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.
7The ozone depletion process
8Responsibility for ozone damage each year
9Global CFC production
10(No Transcript)
11Ozone 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).
12Ozone hole size by month
13Ozone hole measurements over the Antarctic region
1980-98
14Ozone concentration at the center of ozone hole
15Ozone hole over continents comparison 1996
16Image of the ozone hole over the South pole July
10 2003
17Image of the ozone hole over the North pole July
10 2003
18Ozone status full day global image, July 9th 2003
19Effects 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.
20Effects 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
21Harmful 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
22Correlation between Ozone depletion and skin
diseases
23The Ultraviolet Exposure Index
INDEX VALUES EXPOSURE 0 2
Minimal 3 - 4 Low 5
- 6 Moderate 7 - 9
High 10 Very High
24Factors 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.
25Factors 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.
26Policy 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.