Page 206 - Science Class 08
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ozone layer which protect us from ultraviolet there are lots of greenhouse gases, one is a
rays coming from the sun. worse offender than any of the others. That gas
Deforesta on : Plants convert CO in O during is CO . The burning of fossil fuels is leading to
2
2
2
the process of photosynthesis. Due to defores- increase concentra on of CO in the atmo-
2
ta on the amount of CO is increasing in the sphere. Scien sts believe that increasing levels
2
atmosphere. Since CO traps the heat of the of CO and other gases in the atmosphere are
2
2
atmosphere, the temperature is rising on the leading to rise in temperature of the earth. This
earth’s surface causing ‘global warming’. could have serious effects. The polar ice-caps
will start mel ng and the amount of water in
ocean and seas will increase. As sea levels rise,
the coastal areas will be flooded.
6% sca ered by atmosphere
20% reflected by clouds
20% absorbed by
Harmful Effects of Air Pollu on atmosphere and
clouds 5% reflected by
Air pollu on has a great impact on our health.
49% absorbed by the earth’s
It may cause serious respiratory diseases like the earth’s surface
surface
asthma, bronchi s, pneumonia, lung cancer
and tuberculosis. If anyone is exposed to such
pollu ng condi on for a longer period, he or
she can become the vic m of many other
severe diseases. Ozone Hole : Chlorofluoro carbons (CFCs) are
Carbon monoxide is a poisonous gas which used to make coolants for refrigerators and air
causes suffoca on. It may even cause death. condi oners, computer parts and sprayers.
CFCs can do a lot of damage. They destroy the
Acid Rain : On burning of fossil fuels like coal or
ozone layer. The ozone layer protects the earth
petroleum, Nitrogen Oxide (NO) and sulphur
dioxide (SO ) are produced. These gases com- from the harmful ultraviolet rays of the sun.
2
bine with the atmospheric water and form These harmful rays can cause skin cancer and
eye defects in human beings.
nitric acid and sulphuric acid, respec vely.
Then, acids reach the surface of the earth with Preven on and Control of Air Pollu on
water droplets caused acid rain. It damages The most important step to control air pollu on
crops, plants, buildings, monuments, metal is to grow more trees. You know that trees
structures, soil, etc. convert CO into O and maintain their balance
2
2
The Green House Effect : The Green House in the atmosphere. They also reduce dust
Effect is a process in which certain gases, par cles in the air.
known as greenhouse gases trap heat that is Curbing the Emissions from Vehicles : This
radia ng from the earth’s surface. Though type of control can be a ained by:
206 Science-8
