the ozone and atmosphere

Depletion of the Ozone, green house effect and whats being deon about it.

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Farrah Khalid 12 MAS
Depletion of the Ozone Layer
Man made chemicals, primarily chlorofluorocarbons (CFCs), travel to the upper
atmosphere where they catalyze the breakdown of the protective ozone layer.
Scientists have warned that even if action is taken quickly enough, ozone depletion
can be reduced, but not reversed for at least 100 years.
Ozone is composed of three oxygen molecules (O3) is produced naturally by sunlight.
At ground level ozone is a pollutant, but in the upper stratosphere (a segment of
atmosphere extending approximately 9 miles to 30 miles above the earth's surface) it
forms a layer that protects the earth from the sun's harmful ultraviolet radiation, and
rocks form outer space. Although ozone composes a small part of the atmosphere's
total mass, it absorbs more than 99% of the sun's ultraviolet radiation.
In small doses, ultraviolet radiation can produce sunburn and has been shown to
cause skin cancer in laboratory animals. In greater amounts this radiation can "break
apart" important biological chemicals, including DNA. 1% depletion in the ozone layer
allows 2% more ultraviolet radiation to reach the earth's surface. Scientists predict
that this would raise the incidence of skin cancer by 4% to 5%.
Increased ultraviolet radiation will also cause an increase in cases of cataracts,
suppress human and animal immune systems, damage fish larvae, kill off
micro-organisms on the ocean floor that serve as food for larger marine life, give some
crops 'sunburn", decrease crop yield, and damage man made products such as paints
and plastic.
Chlorofluorocarbons CFC's have been shown to contribute to the greenhouse effect.
This would result in a partial melting of the ice caps, a rise in sea levels, and the
disruption of current weather patterns and the decline of agricultural productivity.
Scientists had measured the amounts of ozone layer for many years fearing it might
be damaged by man-made air pollution. Then suddenly, in 1985, British scientists
announced that they had discovered a thirty per cent decrease in the amount of
ozone over Halley Bay in the Antarctic. At first they could not believe their
Measurements - they had expected damage to occur slowly. Also satellite scientists
had told their computers to regard any very low readings as errors and therefore
missed the hole. The damage was so dramatic that scientists were extremely
CFC sources
CFCs are found in fridges, freezers and air conditioners and in some aerosol spray
and fire extinguishers. Plastic foams used for packaging and furniture can be made
with CFCs. In electronics factories, CFCs are used to clean the circuit boards that go
into televisions and computers. The CFCs then gradually drift up into the atmosphere

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Farrah Khalid 12 MAS
Chlorofluorocarbons (CFC's), and chemicals like it, do not bond easily with other
chemicals. This makes them nontoxic and ideal for use in manufacturing processes.
Because CFCs are so unreactive, they do not decompose in the lower atmosphere as
most chemicals do. Instead, they travel up to the stratosphere where the ozone layer
exists. There they are broken down by ultraviolet radiation and release chlorine
atoms.…read more

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Farrah Khalid 12 MAS
Other Harmful Chemicals
In addition to CFCs, other chemicals have been shown to destroy the ozone layer.
These are methyl chloroform, halon 1211 and 1301, and carbon tetrachloride. Methyl
chloroform is used as a cleaner for electronic and metal parts. Halon 1211 and 1301
are used as fire extinguishing agents. Carbon tetrachloride is commonly used in
Europe, the Soviet Union and much of the third world as a solvent and is also used in
the U.S.…read more

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Farrah Khalid 12 MAS
Nitrous oxide and CFCs. There is nearly a third more carbon dioxide in the
atmosphere today than there was 200 years ago.
3. Methane is a greenhouse gas made up of carbon and hydrogen gas. A
single cow expels 500 liters of methane every day.
4. The greenhouse effect is very important. Without the greenhouse effect
the Earth would not be warm enough for humans to live on.…read more

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Farrah Khalid 12 MAS
through the glass or plastic but the roof and walls slow the escape of heat and so
heats the interior.
Similarly the earth's atmosphere allows most of the sunlight that reaches it to pass
Through and heat the earth's surface. The earth sends the heat energy back into the
Atmosphere as infrared radiation. Much of this infrared radiation does not pass freely
Into space, because certain gases in the atmosphere absorb it.…read more


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