WBBSE Class 6 Geography Solutions Chapter 8 Pollution

Detailed explanations in West Bengal Board Class 6 Geography Book Solutions Chapter 8 Pollution offer valuable context and analysis.

WBBSE Class 6 Geography Chapter 8 Question Answer – Pollution

Answer the following questions briefly: (1 mark each)

Question 1.
What is the main source of air pollution?
Answer:
Auto-vehicles

Question 2.
Name a natural source of air pollution.
Answer:
Volcanic eruption

Question 3.
Name a man-made source of air pollution.
Answer:
Industrialisation

WBBSE Class 6 Geography Solutions Chapter 8 Pollution

Question 4.
Expand CFCs.
Answer:
Chloro fluoro carbons

Question 5.
Which gases deplete ozone layer?
Answer:
CFCs

Question 6.
Name a disease caused by air pollution.
Answer:
Lung cancer

Question 7.
Which element causes acid rain?
Answer:
Sulphur

Question 8.
Which gas is called Greenhouse gas?
Answer:
Carbon dioxide

Answer the following questions briefly: (2 mark each)

Question 1.
Define pollution and its types.
Answer:
Pollution : Pollution is defined as the contamination of natural environment that causes instability, disorder, harm to the ecosystem i.e. physical systems or living organisms.

Types of Pollution :

  • Air pollution
  • Water pollution
  • Land pollution
  • Noise pollution.

WBBSE Class 6 Geography Solutions Chapter 8 Pollution

Question 2.
What are pollutants?
Answer:
Elements which cause pollution and harm the ecosystem are called pollutants.

Question 3.
How is acid rain caused?
Answer:
Acid rain : Acid rain is caused mainly by the presence of oxides of sulphur and nitrogen in the upper atmosphere, where the rain precipitation occurs.

Question 4.
Name the causes and effects of air pollution.
Answer:
Causes and effects of air pollution are –

  • greenhouse effect
  • particulate, contamination
  • increased UV radiation
  • acid rain
  • increased ground level ozone concentration
  • increased levels of nitrogen oxides.

Question 5.
What is radiation pollution?
Answer:
Radiation pollution is caused by radioactive substances released by nuclear power plants. This is harmful to humans and other organisms.

Question 6.
Name two greenhouse gases.
Answer:
Carbon dioxide, methane.

WBBSE Class 6 Geography Solutions Chapter 8 Pollution

Question 7.
What is smog ?
Answer:
In urban areas smog is formed when fog is mixed with smoke,

Question 8.
How is depletion of ozone caused ?
Answer:
Depletion of ozone is caused mainly by chlorofluorocarbons (CFCs) emitted from air conditioners refrigerators etc.

Question 9.
Name the important gases which is responsible for ‘greenhouse effect’?
Answer:
Chlorofluorocarbons (CFCs) and carbon dioxide.

Question 10.
Write any one cause of indoor air pollution.
Answer:
Chemicals like paints, varnishes etc, artificial building materials like plywood can cause indoor pollution. Poor ventilation is homes can worsen the situation.

Question 11.
How air polluted by different automobiles?
Answer:
Buses, lorries, private cars, ships and aeroplanes use petrol, diesel, gasoline as fuels. As a result huge amounts of lead and carbon monoxide gets mixed with air.

WBBSE Class 6 Geography Solutions Chapter 8 Pollution

Question 12.
How air polluted by bacteria repellents and air fresheners?
Answer:
Air also gets polluted from the waste, the smoke of incense sticks, mosquito coils and oils, chemical substances used as bacteria repellents and air fresheners.

Answer the following questions briefly: (3 mark each)

Question 1.
Describe the harmful effects of air pollution on human body.
Answer:
Harmful effects of air pollution :

  • Inhalation of polluted air causes diseases associated with respiratory system.
  • It ranges from common cold to lung cancer.
  • Damage to respiratory system may lead to bronchitis, asthma etc.
  • Air polluted with carbon monoxide, when inhaled reacts with hemoglobin of blood and reduces its oxygen-carrying capacity.
  • Some pollutants in air also cause irritation to eyes.

Question 2.
What is the cause of depletion of ozone layer?
Answer:
The continous use of chlorofluoro carbons (CFCs) as refrigerants, coolants, propellants in aerosol sprays, discharge of oxides of nitrogen from supersonic aircrafts, excessive use of nitrates as fertilizers deplete the ozone layer. This results in the increase in ultraviolet radiation from the sun reaching the earth.

Question 3.
Explain Green house effect.
Answer:
Atmosphere consists of different types of gases namely nitrogen, oxygen, carbon dioxide and other gases. Out of all gases, carbon dioxide has the tendency to retain or trap heat radiated from the earth’s surface. As the concentration of carbon dioxide increases in the atmosphere, more and more heat gets trapped.

Carbon dioxide is transparent to incoming solar radiation but does not allow long wave terrestrial radioations to escape into the space. This causes the temperature of earth to rise. This is called greenhouse effect.

WBBSE Class 6 Geography Solutions Chapter 8 Pollution

Question 4.
State measures for abatement of air pollution.
Answer:

  • Air quality standards be used.
  • Technical division for industries be used.
  • Vehicular exhaust be controlled.
  • CFC free products are to used.
  • Alternative products be used.

Identify the correct answers (MCQ): (1 mark each)

Question 1.
Which one of the following air pollutants is formed by the burning of coal ?
a. Sulphur dioxide
b. Ammonia
c. Nitrogen dioxide
d. Nitric acid.
Answer:
a. Sulphur dioxide

Question 2.
Which gas is both harmful and beneficial to life on earth ?
a. Oxygen
b. Ozone
c. Carbon dioxide
d. Methane
Answer:
b. Ozone

WBBSE Class 6 Geography Solutions Chapter 8 Pollution

Question 3.
Which is the major source of harmful radiations in the house?
a. Tube light
b. Colour TV
c. Microwave oven
d. Heater
Answer:
b. Colour TV

Question 4.
Which gas is mainly responsible for the creation of the Greenhouse effect?
a. Ozone
b. Oxygen
c. Carbon dioxide
d. Carbon monoxide
Answer:
c. Carbon dioxide

Question 5.
Of the following four metropolitan cities, tell where pollution hangs above like a cloud ?
a. Mumbai
b. Kolkata
c. Delhi
d. Chennai
Answer:
c. Delhi

Question 6.
Which colour has become established as a sign of conservation and environment ?
a. Orange
b. Purple
c. Safron
d. Green
Answer:
d. Green

Question 7.
Green house effect is-
a. an ocean phenomenon
b. atmospheric phenomenon
c. soil phenomenon
d. none of these.
Answer:
b. atmospheric phenomenon

Question 8.
Which day is celebrated as world environment day?
a. 2 February
b. 19 July
c. 5 June
d. 28 August
Answer:
b. 19 July

WBBSE Class 6 Geography Solutions Chapter 8 Pollution

Question 9.
Depletion of ozone is caused by ………………..
a. water pollution
b. air pollution
c. land pollution
d. noise pollution.
Answer:
b. air pollution

Question 10.
Acid rain is likely to occur in ………………..
a. desert
b. a highly industrialised a tea
c. a forest area
d. agricultural area.
Answer:
d. agricultural area.

Question 11.
A warm layer of air over a cool, stationary layer of air is scientifically called ………………..
a. Smog
b. Fog
c. Thermal pollution
d. Thermal inversion.
Answer:
b. Fog

Question 12.
Acid rain is a serious problem in …………………
a. Cape Town
b. New York
c. Rome
d. Chandigarh
Answer:
c. Rome

Question 13.
Major pollutant for ozone depletion is ………………..
a. water vapour
b. dust
c. chlorofluorocarbons
d. vapour
Answer:
b. dust

Question 14.
Ozone layer is found over a distance of ………………..
a. 5-6 km
b. 10-35 km
c. 55-75 km
d. 40-100 km
Answer:
a. 5-6 km

WBBSE Class 6 Geography Solutions Chapter 8 Pollution

Question 15.
Preventive measure for air pollution
a. controlled use of fossil fuels
b. control of air pollution
c. built of damage
d. none of these
Answer:
b. control of air pollution

Fill in the blanks with correct words : (1 mark each)

1. In urban area ____ is formed when fog is mixed with smoke.
Answer: smog

2. Major pollutant for ozone depletion is ____
Answer: chlorofluorocarbons

3. Global warming is caused by ____ effect.
Answer: Greenhouse

4. CFC is the main threat to ____ layer.
Answer: ozone

5. Forest fire causes ____ to mix with air.
Answer: carbon dioxide

6. Decomposition of swampy land and bogs emits ____ gas and pollutes air.
Answer: methane

7. ____ pollution may be defined as an unwanted change in the quality of the earth’s atmosphere.
Answer: Air

8. The ____ layer of the earth’s atmosphere protects us from the harmful ultraviolet rays of the sun.
Answer: ozone

9. Many marble statues are damaged due to ____ caused as a result of air pollution.
Answer: acid rain

10. Ultraviolet rays are responsible for cancer of ____ and ____ in human beings.
Answer: skin, eyes

If the sentence is true, write ‘T’ and if false write ‘F’ against the following :

1. CFC is a greenhouse gas.
Answer: True

2. Afforestation can same the grave situation of the environmental pollution.
Answer: True

3. Air pollution is caused by poisonous gases like carbon dioxide, carbon monoxide, nitrogen oxide, sulphur dioxide etc.
Answer: True

WBBSE Class 6 Geography Solutions Chapter 8 Pollution

4. The amount of carbon dioxide in air is decreasing day by day.
Answer: False

5. Ozone hole is largest over Antarctica.
Answer: True

Match the Following (1 mark each)

1. Smog a. damages marble statues
2. Global warming b. winter morning
3. CFC c. melting of polar ice cap
4. Acid rain d. disease caused by air pollution
5. Asthma e. Greenhouse gas

Answer:

1. Smog b. winter morning
2. Global warming c. melting of polar ice cap
3. CFC e. Greenhouse gas
4. Acid rain a. damages marble statues
5. Asthma d. disease caused by air pollution

Pollution Class 6 WBBSE Notes

Chapter at a Glance

  • Pollution : Pollution is defined as the contamination of natural environment.
  • Pollutants : Substance that contaminate air.
  • Anthropogenic pollutant : Pollutants such as carbon dioxide, emitted due to burning of fossil fuels.
  • Aerosols : Matter emited into the air-like dust, smoke, mist, fog.
  • Acid rain : Acid rain is caused when a pollutant like sulphuric acid combines with droplets of water in the air.
  • Smog : Smog is smoke and fog emitted in industrial forms

Causes of Air Pollution : Air pollution is caused by harmful gases such as carbon dioxide, sulphur dioxide and nitrogen dioxide and very small particles of carbon. Most of the air pollution is caused by the emissions factories, vehicles and livestocks. Environment is our basic life support system. It provides the air we breath, the water we drink, the food we eat and the land where we live.

WBBSE Class 6 Geography Solutions Chapter 8 Pollution

How do human beings modify this natural environment? The car fumes pollute the air, water is collected in a pot, food is served in vessels and land is used to build factories. Human beings make cars, mills factories and manufacture containers. This is how human beings modify natural environment then what is environment? What ever we see in our surroundings is a part of our environment. Everything which surrounds us may collectively be termed as the environment.

Modern man lives a life of comfort and luxury which requires additional resources. The activity of modern man has slowly degrading the quality of global environment. So life on this planet earth has continued to modify and alter the atmospheric, lithospheric and oceanic components of the natural environment since the very beginning. As a result, the changed environmental conditions adversely affect the organisms in the biosphere. This deteriorating conditions of the physical environment is called environmental degradation.

What is Pollution ? Pollution is defined as the contamination of natural environment that causes instability, disorder, harm to the ecosystem i.e. physical systems or living organisms.

Pollution means the presence of undesirable substance in any segment of the environment primarily due to human activity discharging by products and waste products which are harmful to man and other organisms. The environmental pollution is now considered a global phenomenon.

What is pollutant? A pollutant is defined as any form of energy or matter that causes degradation and pollution.

Different types of Pollutants : Pollutants can be divided into following types-

  • Primary pollutants such as carbon monoxide
  • Secondary pollutants such as ozone, aerosols
  • Biodegradable pollutants such as sewage
  • Nonbiodegradable pollutants such as plastics
  • Natural pollutants such as carbon dioxide.

Air Pollution :

Definition : Air pollution may be defined as the mixing of some substances in the surrounding (ambient) air in such concentration that a situation arises in which man and environment is badly affected. It is an unwanted change in the quality of the earth’s atmosphere caused by emission of gases due to burning of fossil fuels and other natural causes.

WBBSE Class 6 Geography Solutions Chapter 8 Pollution

Causes of air pollution: Air pollution is caused by various types of pollutants released mainly from different sources or reasons. There are many causes of air pollution which may be grouped into two categories.
A. Air pollution due to natural causes and
B. Air pollution due to human activities.

A. Air pollution due to nature : The air pollutions which are caused by nature may be distinguished as :

  • Volcanic eruption : It may be caused by volcanicity, when eruption occurs, sulphides, sulpher dioxide, carbon monoxide and other gases come out and mix with air, causing pollution.
  • Forest fire : Forest fires caused due to friction of two dry branches release carbon dioxide, ash, carbon particles those mix with the air and pollute it.
  • Dust storm : Occurence of dust storms in different parts on earth surface specially in desert are as release huge amount of dust particles in the air we breath become heavy pollution.
  • Decompositions of Swampy land: Decomposition of swampy land and bogs emits methane gas and thus pollutes air.

WBBSE Class 6 Geography Solutions Chapter 10 India Our Motherland 20

B. Air pollution due to human activities : Increase in population, deforestation, urbanization, industrialization and wars have rapidly taken place. Air pollution is caused by various types of pollutants released mainly from industries, thermal powers, domestic appliances and automobiles.

WBBSE Class 6 Geography Solutions Chapter 8 Pollution

a. Fossil fuel based industries:

  • Petroleum refineries release poisonous gases like sulphur dioxide SO2 nitrogen oxides (NO) etc.
  • Large scale burning of fossil fuels such as coal, diesel, petroleum produces poisonous gases like carbon dioxide CO2 carbon monoxide (CO), nitrogen oxide (NO) and sulphur dioxide.

WBBSE Class 6 Geography Solutions Chapter 8 Pollution 2

b. Cement factories : Dust is produced from cement factories as stones crushers and hot mix plants release suspended particulate matter (SPM) more than five times the safety limits by industrial standards.

c. Thermal power plants : Thermal power plants produce deadly pollutants such as fly ash, SO2 hydrocarbon etc.

d. Other industries : Other industries like food, fertilizers and chemical manufacturing plants also produce harmful poisonous gases.

Urban areas : In urban areas, automobiles are the chief sources of air pollution. The ever-increasing traffic density has aggravated the existing problem of air pollution particularly in the major cities of the world.

WBBSE Class 6 Geography Solutions Chapter 8 Pollution

f. Automobiles : Automobiles mainly produce pollutants like unburnt hydrocarbons, CO (carbon monoxide), NO (nitrogen oxide), lead oxides etc. Other pollutants like aldehydes, esters, ethers, ketones and peroxides are also found in automobile emissions.

Some 10 lakhs kilograms of smoke emitted daily from the vehicles that ply on roads of the five metropolises of our country namely Kolkata, Delhi, Mumbai, Chennai and Bangaluru gets mixed with air. The chief pollutants derived from different sources are listed below :

i. Carbon compounds : Carbon compounds complete combustion of fossil fuels like mineral oil and coal produces carbon dioxide CO2 and carbon monoxide (CO). The principal sources of CO, apart from automobiles, are combustion processes such as stones, forest fires and open fires.

ii. Sulphur compounds : Fossil fuels like coal release sulphur compounds like SO2 hydrogen sulphide H2 and sulphuric acid (H2SO)4).

Amongst all the compounds, the oxides of sulphure are considered to be the most poisonous pollutants. The other compounds include carbonyl sulphide (COS), carbon disulphide (CS2), dimethyl sulphide [(CH3)2] and sulphates (XSO4).

iii. Nitrogen Oxides (NOX) : Nitrogen monoxide (NO), nitric acid (HNO)3 and nitrogen dioxide NO2 are released by automobiles, industries, power plants etc.

WBBSE Class 6 Geography Solutions Chapter 8 Pollution

iv. Ozone (O3): It is released from home appliances like refrigerators, air conditioners etc. due to the release of harmful chlorofluorocarbons (CFCs), etc. (O3) is also formed in the atmosphere as a result of chemical reactions involving polutants like SO2, NO2 aldehydes etc.

Others :

  • Smoking of cigarettes, cigars, bidis etc. produces carbon monoxides gas due to incomplete combustion of tobacco leaves.
  • Pesticides and insecticides are complex organic compounds using toxic elements like chlorine, bromine, arsenic etc. for killing pests and insects.
  • Chemicals like paints, varnishes etc., artificial building materials like plywood can cause indoor pollution.
  • Huge amount of smoke, carbon particles and quite a few harmful gases blend with air from the wood, cowdung cakes, coal and gas used in cooking.
  • Air also gets polluted from waste, the smoke of incense sticks, mosquito coils and oils, chemical substances used as bacterial repellents and air fresheners.
  • In 2011, there was an explosion in the nuclear plant at Fukushima in Japan. As a result huge amount of radioactive materials contaminated the air causing pollution.

Effects of Air Pollution
A brief discussion of the impact of air pollution follows :

1. Ozone Depletion :
What is ozonosphere :
Ozone is gas. The region of stratosphere of atmosphere, at an attitude of 23-26 km over equator and at slightly lower altitude elsewhere, having a thick sheet of ozone is called ozonosphere. As per estimates, 90% of the total atmospheric ozone is present in this region.

A What is ozone and its utility ? : Ozone is a form of oxygen. The molecule of ozone contains three oxygen atoms (O3). In the stratosphere, ozone is being photo-dissociated and generated by the absorption of short-wave length ultraviolet UV radiations :
WBBSE Class 6 Geography Solutions Chapter 8 Pollution 4
The two reactions (photodissociation of O3 and its generation) are in equilibrium leading to steady concentration of ozone in the stratosphere some 20-26 km above sea level. This ozone dynamics dissipates the energy of UV radiations as heat. In this way, ozone layer in the stratosphere acts as a shield to protect all types of life on earth from the harmful effects of UV radiations.
WBBSE Class 6 Geography Solutions Chapter 8 Pollution 3

A Unit of measurement : The amount of atmospheric ozone is measured by Dobson Spectrometer and is expressed in Dobson Units [DU]. One DU is equivalent to 0.01 mm thickness of pure ozone at the density it would possess if it were brought to ground level pressure (1 atm).

WBBSE Class 6 Geography Solutions Chapter 8 Pollution

A Thickness and absorption of UV radiation : Absorption of UV radiations by ozone blanket is proportional to its thickness. As the thickness of ozone is more above poles than at equator, therefore, the maximum amount of UV radiations pass through atmosphere to reach the earth surface in the tropics (near equator).

This amount of UV radiations reaching the earth decreases towards the poles. Also, concentration of ozone in the stratosphere changes with seasons; it is maximum during spring season (February to April) and maximum during fall season (July to October).

Ozone hole : Decline in the thickness of ozone layer over a restricted area is called ozone hole. It was first discovered over Antarctica in 1985 by Dr. Joe. C. Farman and his colleagues in British Antarctic Surveys. The spring time ozone layer thickness above Antarctica varies from 280 to 325DU[1DU = 1ppb] between 1956 A. D. to 1970 A. D. Thereafter, it sharply declined to 225 DU in 1979, to 136 DU in 1985, and to about 94 DU in 1994.

Causes of ozone depletion and ozone hole : Chlorofluorocarbons (CFCs) are mainly responsible for ozone depletion in the stratosphere. CH4 and N2O also cause destruction of O3 through complicated series of reactions. CFCs are a group of synthetic chemicals first discovered by Thomas Midgley Jr. in 1930. Chlorofluorocarbons are used as coolants in refrigerators and air conditioners, as propellants, cleaning solvents, slerilant and in styrofoam etc.

Once released in the troposphere, CFCs reach the stratosphere and produce ‘active chlorine’ [Cl and ClO radicals] in the presence of UV radiation. These radicals through chain reactions destroy ozone by converting it into oxygen. A single chlorine atom converts 1 lakh molecules of ozone into oxygen.

WBBSE Class 6 Geography Solutions Chapter 8 Pollution 5

Acid Rain:
The poisonous gases and other chemicals heat power into atmosphere every second have made atmosphere a global sink of dangerous wastes. In this sink hundreds of chemical reactions are surfacing from time to time. Apart from global warming and ozone depletion acid rain is another complex phenomenon. Its effect is compounded by the fact that is occurs with precipitation. Sulphuric acid and nitric acid are produced by burning of petrol, coal and gas in automobiles and factories. They are also chief waste products of power stations.

WBBSE Class 6 Geography Solutions Chapter 8 Pollution 6

These geses collect in atmosphere and mix with the moisture in air and fall to the ground with precipitations (rain, snow, hail). The rain clouds of ten drift hundreds of kilometre before falling as rain. The presence of carbon dioxide in air reduces rainfall pH (hydrogen ion concentration to 5.6 is water).

WBBSE Class 6 Geography Solutions Chapter 8 Pollution

In industrialised countries of the world like the USA, Western Europe, North-East China and Japan acid rain with a pH below 4.0 has been recorded. Norway and Sweden also have experienced acid rain as a result of emissions in air in the UK. Much of the acid rain experienced in north-western Europe comes from emissions in atmosphere in Germany because of drifting of clouds.

3. Effects on Weather and Climate :
a. Smog: Big factories emit a lot of smoke, dust, carbon and dust particles. They pollute out atmosphere. Fog is formed during cool nights particularly in England. These particles remain in the atmosphere. Fog is then called smog. In 1952, the smog formed over London killed 4,000 persons due to suffocation.

b. Leakage of poisonous gases :

  • The Leakage of poisonous gases from a pesticide factory in Bhopal in the year 1984 caused deaths to thousands of people.
  • The leakage of radioactive material in Chernobyl Atomic Power Plant in Russia in 1986 resulted in extensive damage.

4. Effects on Human health
Air pollution mainly affects the respiratory system. Bronchitis, asthma and lung cancer are some of the chronic diseases caused due to exposure to polluted air.

5. Effects on Plants and Animals
Air pollution has caused widespread damage to vegetation. Depletion of ozone results in increase of ultra-violet solar radiation reaching the earth’s surface. The UV rays badly affect plant and animal communities in a variety of ways.

Green house Effect

Definition : A building
made chiefly of glass for growing or sheltering the delicate or exotic plants is called green house. The air in the greenhouse is warmer than the outside air though it receives less solar radiation. The occurrence of higher temperature inside a green house than outside, even though the interior receives less solar radiation, is known as the ‘green house effect’.

WBBSE Class 6 Geography Solutions Chapter 8 Pollution 7
Reasons for Green House Effects: Three factors contribute to the green. house effects i.e. warmness in a green house:

  • Glass wall is of the green house
  • CO2 contents, and
  • Water vapour contents of the air in the green house.

WBBSE Class 6 Geography Solutions Chapter 8 Pollution

These allow most of the solar radiations to enter right upto the earth’s surface, but do not allow a substantial amount of the long-wave infrared radiation emitted by the earth to escape. This makes green house air warmer than the outside air.

WBBSE Class 6 Geography Solutions Chapter 8 Pollution 8

Green House Effect on Earth : If the earth had no atmosphere, its average surface temperature would be about -18°C, the same as that of the moon, which lacks atmosphere. Actually, the temperature of the earth’s surface is about 15°C. The reason why the earth is warmer than the moon is that it has an atmosphere.

The atmospheric cover around the earth acts like glass walls of a greenhouse. It absorbs much of the incoming solar radiation from the sun and rediates to the earth’s surface. However, it prevents the long-wave infrared radiation emitted by the earth’s surface to escape into the space.

Thus, the atmosphere acts as a green house, trapping the heat. Man can survive on earth only because of this green house effect. The gases in the atmosphere most responsible for keeping the earth’s surface warm are carbondioxide (CO2), nitrous oxide (N2O) and water vapours. These gases are called as green house gases. CO2 CH4, CFCs and (N2O) are also termed as radiatively active gases as they can absorb long wave infrared radiation.

Man is adding large amount of CO2 to the atmosphere each year by burning fossil fuels in homes, industries and automobiles, biomass burning associated with agricultural practices etc. Methane is added to the atmosphere by marshes, paddy fields, cattle sheds and biogas plants. Chlorofluorocarbons are emitted by refrigerators and air conditioners.

Nitrogen oxides are produced from organic matter and fertilizers by denitrifying bacteria as well as from automobiles exhausts and industries. Recently, the concentrations of these green house gases in the atmosphere have increased and this is affecting the global climate. The increase in mean global temperature due to increased concentrations of greenhouse gases is called global warming.

WBBSE Class 6 Geography Solutions Chapter 8 Pollution

Global Warming:

Definition : Global warming refers to a gradual rise of temperature in the atmosphere and the consequent change in the global radiation balance mainly due to anthropogenic processes leading to climatic change at different levels-local, regional and global.

Causes : About 75% of the solar energy reaching the Earth is absorbed by the Earth’s surface, which increases its temperature. The rest of the heat radiates back to the atmosphere. Some of the heat is trapped by greenhouse gases [GHGs], mostly carbon dioxide. As carbon dioxide is released by various human activities, it is rapidly increasing. This causing global warming.

According to the Director of the Philippines Atmospheric Geophysical and Astronomical Services Administration [PAG-ASA], global warming and consequent temperature rise can be mostly attributed to the developed countries which heavily depend on automobiles, air-conditioning and other high-tech amenities which produce CO and methane.

Carbon dioxide contributes 60% of global warming and comes mostly from the burning of fossil fuels such as coal, oil and natural gas. Methane contributes 15-20% in global warming. It is derived from flooded paddy fields, livestocks, waste dumps and coal mining.

Effects of Global Warming :

  • Global warming could cause climatic change, increasing in temperature, acid rain, increased rate of ultraviolet (UV) rays penetraion, increased ozone in the troposphere acting as the primary component of atmospheric smog.
  • The effects on the biosphere include the loss of habitat, depletion of coral reserves, loss of biodiversity, forest fires, desertification and so on.
  • 10-15% of the arable land and economic reproductivity of such areas could be lost.
  • High concentration of carbon dioxide will have fertilizing effect and will encourage plant growth.
  • Some animals may die due to intolerance of increased amount of heat.
  • Insects would start breeding more vigorously.
  • Food chains will be altered and breeding time of many species would be affected.
  • Many wetlands would dry out.
  • It would cause large scale migration of people living on the coastal areas due to inundation of coastal areas.

WBBSE Class 6 Geography Solutions Chapter 8 Pollution

Remedies : The remedial measures have been summarized below :

a. Control of Carbon dioxide emission : A drastic cut in the fossil fuel consumption is needed, particularly in the developed countries of the world with almost 50% of the world consumption of fossil fuel.

b. Alternative energy : If the Toronto Resolutions (1988) demanding a drastic cut of 20% fossil fuel emission are to be implemented, more emphasis should be given on developing new alternative fossil fuels. Recently the use of CNG and liquefied petroleum gas [LPG] in a few metre of the world has proved successful. These substitutes cause very low pollution.

c. Others :

  • Increasing the vegetation cover particularly forests for photosynthetic utilisation of CO2.
  • Replacing chlorofluorocarbons with substitutes having little effect on global warming and ozone.
  • Minimizing the use of nitrogen fertilizer’s by relying more and more on nitrogen fixation.

Measures for Reducing Air Pollution:
Air pollution can be controlled or reduced by taking some measures. These measures are discussed in the next page :

1. Checking of Industrial Pollution : For checking industrial pollution it is necessary to remove particular matter and gaseous pollutants from the industrial wastes. The removal of particular matter is possible by using devices such as cyclone collectors which remove about 70% of the particles; electrostatic precipitators (ESPs) which can remove the particles from gas by applying electrical forces with in the precipitator’s chamber, and can effectively remove 99 per cent of the particulars.

WBBSE Class 6 Geography Solutions Chapter 8 Pollution

2. Remove gaseous pollutants : In order to remove gaseaus pollutants, wet systems may be used these are washing towers in which the fluid of alkali circulates, and reacts with ‘sulphur dioxide’ to produce a precipitate. In wet-dry systems, calcium hydroxide and charcoal are used as pollutant absorbents in drycleaning plants, paint factories, breweries, food processing plants, pharmaceutical industries etc.

3. Enforcement of laws :The problems related to industrial pollution can be controlled by enforcing laws. For example, the recent supreme court judgement in India has forced all the industries in Mathura and Agra (surrounding the historic Taj Mahal) to either upgrade their machineries or shift to other places because industrial pollution was causing damage to the Taj Mahal’s structure.

For checking pollutant emission from vehicles, the following methods are adopted

  • applying new proportion of air and gasoline.
  • maintaining more exact time for feeding fuel,
  • using gas additives for improvement of combustion.
  • converting exhaust compounds of vehicles to less toxic materials by injecting air into the exhaust.
  • updating engine design to eliminate poisonous gases like carbon monoxide (CO), nitric oxide and hydrocarbon productions.

4. Afforestation and check on deforestation: Clearing of forested area by felling the trees should be prohibited by law. Afforestation or planting trees should be encouraged. In India Forest Conservation Act was passed in 1980, which was ammended in 1988.

WBBSE Class 6 Geography Solutions Chapter 8 Pollution

5. Mass awareness programme : Regular campaigning against air pollution through newspapers, radio, television can be quite effective for protection air pollution. The harmful effects of air pollution and the source and nature of different pollutants may be highlighted through all these awareness programmes. Taking up programmes like ‘Van Mahotsav’ (planting of new saplings). ‘Social forestry'(1990 growing trees for the benefit of’ people or farmer), ‘Agro-forestry’ (yields by combining food crops with tree crops at the same time).

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