CBSE Class 12 Geography Geographical Perspective On Selected Issues And Problems. Students can download these worksheets and practice them. This will help them to get better marks in examinations. Also refer to other worksheets for the same chapter and other subjects too. Use them for better understanding of the subjects.
GIST OF THE LESSON:
Pollution: Harmful change for animals and plants in the environment is called pollution. Different
components of environment have a definite composition. When some other element is added to
these components their basic composition is altered. This change is called pollution.
ENVIRONMENT: The external conditions surrounding an organisms or a community are its
environment. The environment has two components- one is natural (physical) environment and the
other is human environment.
AIR POLLUTION:Addition of any undesired smell, solid, gas or dust to air and any unnecessary
interference in living conditions due to this is called Air pollution.
Harmful effects of air pollution
Effect on weather and climate: Chemical pollution of air is one of the causes of depletion of
ozone in the atmosphere. The ozone layer saves us from the harmful ultra- violet rays of the
sun. Higher amount of carbon dioxide and some other gases leads to a rise in temperature also.
This has created the danger of melting of ice sheets and glaciers in polar and mountainous
Effect on the health of people: Air pollution can lead to several ailments affecting lungs,
skin, eyes and throat. High levels of air pollution, especially when poisonous gases are present
in the atmosphere, can kill thousands of people. About 2,500 people died in Bhopal city in
1984 due to mixing of poisonous gas MIC in the air thousands became handicapped for life.
Effects on animals and plants:Air pollutants have damaging effects on the leaves and trunks
of the trees and plants by retarding their growth.
Effects on structures like buildings: Theair pollutants like sulphur dioxide, smoke, sand and
dust particles cause damage to various materials. Buildings turn black due to air pollution.
Acid rain creates small hollows in the marble slabs. The colour and shine of world famous Taj
Mahal is badly affected by air pollution.
Control of air pollution
Use of lead- free petrol
Complete checkon burning of fossil fuels
Use of more fuel- efficient engines
use of filters in smoke stacks
Locating factories away from dense settlements
Use of pollution-free energy resources
High smoke stacks
Restricting use of harmful chemicals
WATER POLLUTION: Such changes in the quality of water due to human or natural activities
that render water un-suitable for human consumption or for other organisms, agriculture, fisheries
CAUSES OFWATER POLLUTION
Chemicals used in agriculture
Religious and cultural gatherings along river banks
Inadequate sewage systems and toilets
half-burnt and un-burnt dead bodies
Drilling in sea for petroleum
Quality Criteria for fresh water: The Central Pollution Control Board of India has divided water
into five groups:
I. The first group of water can be consumed without purification, just by removing germs.
II. Water of the second group is considered safe for bathing.
III. Water of this category can be consumed after purifying it through methods and making it
IV. The fourth group of water is suitable for fisheries. It is suitable for wildlife also.
V. The fifth group of water can be used for irrigation, industrial air conditioning and controlled
disposal of waste.
On the basis of above criteria, the water of most Indian rivers belongs to the (iii), (iv) and (v)
groups.Clean drinkablewater is becoming rare in Indian rivers.According to the some studies
“seventy per cent of total available water in India has been polluted”.
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