The document discusses the composition and layers of the atmosphere, with a focus on the ozone layer. It describes the ozone layer as a concentration of ozone molecules in the stratosphere that protects the Earth from ultraviolet radiation. It then explains that chlorofluorocarbons released from human activities were depleting the ozone layer by releasing chlorine atoms that break down ozone molecules. While regulations have led to a reduction in ozone-depleting substances, full recovery of the ozone layer is not expected until around 2050.

2. • The atmosphere is a layer of gases which
surrounds the entire Earth. The purpose of this
"layer" around the Earth is to prevent
excessive amounts of radiation from reaching
the Earth to survive a planet.
The atmosphere is divided into;
I. Troposphere.
II. Stratosphere.
III. Mesosphere.
IV. Thermosphere.

3. •This is the upper limit of
our atmosphere.
•A layer is also where the
space shuttle orbits.
•Meteors or rock
fragments burn up in it.
•Many jet aircrafts fly in it,
because it is very stable.
Also, the ozone layer absorbs
harmful rays from the Sun.
• The first layer above the
surface and contains half
of the Earth's atmosphere.

4. is a colorless gas, it relatively simple molecule,
consisting of three oxygen atoms bound together.
is a highly-reactive from of oxygen, Near the
Earth‘s surface, hurt plant life, and damage people‘s
lung tissues.
is a gas that occurs naturally in our atmosphere.
Most of it is concentrated in the ozone layer, a region
located in the stratosphere several miles above the
surface of the Earth.
also plays a vital role by shielding humans and
other life from harmful ultraviolet ―ultraviolet B‖, light

5. • The ozone layer is a deep layer
and concentration of ozone
molecules in the stratosphere,
encircling the Earth.
• The ozone layer is a belt of
naturally occurring ozone gas
that sits ‗‘15 to 30 kilometers‘‘
above.
• About 90% of the planet's
ozone is in the ozone layer.
• While stratospheric ozone,
which protects us from the sun.

6. when short-wavelength UV
light from the sun hits a molecule
of oxygen gas. The light has so
much energy that it breaks the
oxygen bond holding the atoms
together, thus creating two
oxygen atoms. Through this
process, the oxygen essentially
absorbs the short-wavelength UV
light, but this still leaves a
significant amount of UV light
with longer wavelengths, which is
where ozone comes in.

7. Destruction of the stratospheric ozone
layer. This destruction of ozone is caused by the
breakdown of certain chlorine and/or bromine
containing compounds (chlorofluorocarbons or halons),
which break down when they reach the stratosphere and
then catalytically destroy ozone molecules.
A worrying rate of ozone depletion is found
above the Arctic. Stratospheric clouds in the Arctic

8. • The Antarctic ozone hole was
discovered in 1985 by British
scientists Joesph Farman,
Brian Gardiner, and
Jonathan Shanklin of the
British Antarctic Survey.
• The ozone "hole" is really a
reduction in concentrations of
ozone high above the earth in
the stratosphere. The ozone
hole has steadily grown in size
(up to 27 million sq. km.

9. • Human actions can change the natural state of our
climate:
• The world community works together in a targetted
way, global environmental problems can be effective.
• Cfc's are just one class of chemical substance that
depletes the ozone layer, but they are the most important
one.

10. halogen source gases are emitted at
earth‘s surface by human activities and natural
processes.
halogen source gases accumulate
in the atmosphere and are globally distributed
throughout the lower atmosphere by winds and
other air motions.
halogen source gases are transported
to the stratosphere by air motions.

11. most halogen gases are converted in
the stratosphere to reactive halogen gases in
chemical reactions involving ultraviolet
radiation from the sun.
reactive halogen gases cause
chemical depletion of stratospheric ozone over
the globe.
air containing reactive halogen gases
returns to the troposphere where the gases are
removed by moisture in clouds and rain.

12. • The cause of ozone depletion is the in the
level of such as hydroxyl radicals,
nitric oxide radicals and atomic and
.
• The most important compound, which accounts
for almost 80% of the total depletion of ozone in
the stratosphere are chlorofluorocarbons (CFC).

13. • chlorofluorocarbons (CFC).
• These compounds are very stable in the lower atmosphere of
the Earth, but in the stratosphere, they break down to
release a free chlorine atom due to ultraviolet radiation.
• When CFCs and HCFCs reach the
stratosphere, the ultraviolet
radiation from the sun causes them
to break apart and release chlorine
atoms which react with ozone,
starting chemical cycles of ozone
destruction that deplete the ozone
layer.
• One chlorine atom can break apart
more than 100,000 ozone molecules.

14. • Measurements of CFCs in the stratosphere are made
from balloons, aircraft, and satellites.
• CFCs a were once widely used in aerosol propellants,
refrigerants, foams, and industrial processes.

15. • Other chemicals that damage the ozone layer include;
I. methyl bromide (used as a pesticide),
II. halons (used in fire extinguishers),
III. methyl chloroform (used as a solvent in industrial
processes for essential applications).
• Methyl bromide and halons are broken apart, they release
bromine atoms.
• which are 60 times more destructive to ozone molecules
than chlorine atoms.

16. • 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.

17. • When the ozone layer are thinned larger
quantities of harmful ultraviolet rays to reach
the earth.

18. • UV radiation includes:
– UV-A, the least dangerous form of UV radiation, with a
wavelength range between 315nm to 400nm.
– UV-B with a wavelength range between 280nm to
315nm.
– UV-C which is the most dangerous between 100nm to
280nm. UV-C is unable to reach Earth‘s surface due to
 nm stratospheric ozone‘s ability to absorb it.
=
“Nanometer”

19.  Ozone depletion causes increases in UV rays‘s effects
on aquatic ecosystems by:
i. decreasing the abundance of phytoplankton –
affects the food stock for fishes and the
absorption of CO2.
ii. decreasing the diversity of aquatic organisms –
reduces food stock and also destroys several fish
and amphibians.

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

21.  DNA absorbs UV-B radiation
• Changes shape in DNA
– Changes in the DNA molecule
mean that enzymes cannot ―read‖
the DNA code .
– Results in mutated cells or the cells
die.
 Cells have developed the
ability to repair DNA
• A special enzyme arrives at
the damage site.
• removes the damaged
section of DNA .
• replaces it with the proper
components.

22. i. Skin cancer.
ii. eye disorders (blindness).
iii. Immune system damage.
iv. Premature aging
(photoaging) of the skin
(different from normal
chronological aging).
! Possibly other things too that we
don't know about at the moment.

23. • Because our atmosphere is one connected system, it is
not surprising that ozone depletion and global warming
are related in other ways.
• The ozone hole, is not the mechanism of global
warming. Ultraviolet radiation represents less than one
percent of the energy from the sun—not enough to be
the cause of the excess heat from human activities.
– Global warming is caused primarily from putting
too much carbon into the atmosphere when coal, gas,
and oil are burned to generate electricity or to run
our cars.

24.  Will the ozone layer recover? Can we make more ozone
to fill in the hole?
– Provided that we stop producing ozone-depleting
substances, ozone will be created through natural
processes that should return the ozone layer to
normal levels by about 2050.

25. http://www.weatherquestions.com/What_is_the_ozone_la
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http://environment.nationalgeographic.com/environment/
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http://www.patrickbrown.org/
http://www.teachmefinance.com/Scientific_Terms/Ozone_
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http://news.nationalgeographic.com/news/2010/01/10012
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http://earthobservatory.nasa.gov/Features/UVB/printall.ph
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http://www.windows2universe.org/earth/Atmosphere/trop
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