Chapter 7
CHAPTER NO.7 ENVIRONMENT POLLUTION
Environmental pollution refers to contamination of
the environment with waste products and other impurities. It produces
undesirable changes in the physical, chemical or biological quality of
air,water and soil. These changes are harmful to human life, other organisms
and property. Pollution can be natural or man made. Most of the pollution is
man made and is an outcome of different unplanned activities such as
urbanization, industrialization, transportation and agriculture. The natural
pollution is caused by eruption of volcanoes, weathering or rocks, erosion of
soil, forest fires, decomposition of organic matter, etc. The waste products or
substances (solids, liquids and gases) that cause the pollution of environment
are known as pollutants, ¢.g., smoke, dust, plastics and pesticides. The
important types of pollution are: air pollution, water (fresh and marine)
pollution, soil pollution, noise pollution and radiation pollution.
AIR POLLUTION :
The atmosphere is an invisible cover of gases that
envelops the earth. The clean air present in the atmosphere is a mixture of
gases (nitrogen, oxygen, argon, carbon dioxide) and water vapours.Air pollution
refers to contamination of air by waste products and other impurities which are
hannful
to humans, animals, vegetation and buildings.
The sources responsible for air pollution are of two
types viz., the natural sources and the man made sources (Fig. 7.1). The
natural sources include forest fires, volcanic eruptions, wind erosion of soil,
pollen dispersal, natural radioactivity and decomposition of organic matter by
bacteria. The man
made sources are much diversified. These include
automobiles, industries, thermal power plants,agricultural activities and
quarrying. The fossil fuels (coal, ail, natural gas) are burnt in industries,
thermal power plants and automobiles. This results
in the emission of carbon oxides: carbon monox-ide (CO), carbon dioxide (CO,);
sulphur oxides: sulphur dioxide (SO,), sulphur trioxide (SO,) and nitrogen
oxides: nitric oxide (NO), nitrogen dioxide (NO,), nitrous oxide (N,O).
Different hydrocar-bons (methane, butane, ethylene, benzene) and suspended
particulate matter (dust, soot, asbestos,lead, cadmium, chromium, arsenic,
salts etc). are also present in these emissions. These gases and
suspended particulate matter (SPM) produced as a
result of burning of fossil fuels are the greatest
source of air pollution. The dust and fumes released
by many industries contain nickel, zinc, chlorine,
ammonia, hydrochloric acid and oxides of copper.
Different types of agricultural activities such as spraying of pesticides,
burning of crop residues, release of methane from paddy fields and dust from
agticultural operations also cause a minor pollution of air. Quarrying results
in the release of a large quantity of dust (coal, limestone, quartz, iron,
etc.) into the air.
The pollutants released from natural sources of air
pollution are dispersed in a vast area and do not cause any serious damage.
Most of the health related air pollutants come from man made sources of air
pollution. In large cities, breathing the polluted air proves harmful to human
health. Carbon
monoxide, a serious air pollutant reduces the oxygen carrying capacity of blood and causes nausea,
headache, convulsions, muscular
weakness and slurring of speech. Oxides of nitrogen can damage the lungs, heart
and kidneys of man and other animals. The presence of hydrocarbons in air
causes irritation of eyes, bronchial constrictions, sneezing and coughing.
Similarly, Lead can damage liver,kidneys, brain and reproductive system.
Different air pollutants can result in stunted growth of plants and even may
kill them. In densely populated cities, the air pollution may take the form of industrial
smog and photochemical smog. Industrial smog is a combination of smoke, gas and
fog. Photo-chemical smog is produced as a result of interaction of the air
pollutants under the influence of sunlight. If it perists for several days,
inhalation of this polluted air may cause many health problems.The oxides of
sulphur released from different sources react with water vapours present in the
air and
form sulphuric acid. Then this sulphuric acid falls
on the ground as acid rain and results in erosion of buildings, damage to crops
and death of aquatic animals. Long term excessive emission of carbon dioxide is
also responsible for an increase in the average temperature of the earth's
atmosphere. It acts as a green house gas and has significantly contributed to
the problem of global warming.
WATER (FRESH AND MARINE) POLLUTION :
More than 70 percent of the earth's surface is
covered with water. Out of this, about 97.5 percent of water is present in
oceans. The fresh water which is actually available for irrigation,
drinking, power generation and industrial use is only 0.5 percent of the
total quantity. It is found in
lakes, streams, rivers, and underground. Both the
fresh and marine water are very essential for sustaining life on the planet
earth. Water pollution may be defined as an undesirable addition of
organic, inorganic, biological and radioactive
materials into it that deteriorates its true quality.
The major sources of freshwater pollution are sewer
system, industries and agricultural farms (Fig. 7.2). The sewage is the waste
water containing human wastes (urine and excrement), soaps,detergents, animal
wastes and many othe dissolved organic compounds. The discharge of untreated
sewage into the water bodies results in their pollution. Similarly, the waste
generated by different industries such as paper mills, leather tanneries, soap
factories and sugar mills also adds to water
pollution. In this industrial waste, a variety of
poisonous materials like alkalis, acids, cyanides, lead,
mercury, zine, etc. are key pollutants. Agricultural
activities produce several types of water pollut-ants. The surface run off from
the fields carries away the weedicides, pesticides, chemical
fertilizers,manures and crop residues into the water bodies. In India, the
water pollution is also caused by
unbumnt and incompletely bumt dead bodies of human
beings and other animals that are throw into the tivers,
The polation of fresh air water makes it unfit for
domestic, irrigation, industrial and recreational purposes. Certain micro-organisms
present in the polluted water are responsible for spread of sev-eral water
borne disease such as typhoid, cholera, bacterial dysentary, diarrhoea and
heaptitis. Chemi-cals like lead, mercury and arsenic may damage the nervous
system. The pesticides used in the agricultural farms enter the aquatic
food-chains and their concentration increases at every stage of the food-chain.
This is known as biomagnification. Seepage of these dissolved pesticides may
cause
polhution of the groundwater. The process of
nutrient enrichment (typically phosphates and nitrates)
due to entry of fertilizers and detergents in
aquatic ecosystems is known as eutrophication. It causes
rapid growth of algae and micro-organisms. It
decreases the amount of oxygen dissolved in water.The hot water released from
an industry into a wafer source, increases its temperature and thuscasuses its
thermal pollution. The aquatic biota {animals and plants} that normally live in
cool water fail to tolerate this rise in temperature and get killed due to
thermal pollution.
The marine water is rich in sea food, salts,
chemicals, medicines and minerals. It supports a major components of biological
diversity. About one-fifth of the world's total oil supply comes from the sea.
Oceans are supposed to be the ultimate disposal sites for all natural and
man-made pollu-tion. Like fresh water, marine water also receives a variety of
pollutants from different sources.These include surface run off from urban
areas and farms, industrial wastes from coastal areas and direct dumping of
sewage and garbage by merchant ships and pleasure boats. The accidental oil
spills from tankers, natural cil seepage and materials released from off-shore
drilling platforms also cause pollution problems of the marine water. It is
more rapid around estuaries, harbours, wetlands
and mouths of polluted rivers.
As in case of fresh water, different harmful
chemicals dumped into the marine water enter the ocean food-web and undergo
biomagnification. The ingestion of pesticides, plastics and other syn-
thetic substances causes death of sea birds and
mammals including whales, dolphins and seals. The floating oil released
accidentally from tankers and natural cil seepage fons a coat around the body
of sea animals which may lead to their death. The pollution of marine water,
especially along sca beaches has great economic bearing on coastal area
populations. Also, it reduces the recreational value of the beaches vis-a-vis
income from fishing and tourism.
SOI POLLUTION:
The soil is a loose mixture of inorganice minerals
(clay, silt and sand), decaying organic matter,
water and air. A variety of organisms also inhabit
soil for shelter and food. it is formed in nature by disintegrations of rocks.
Soil provides different nutrients that are essential for growth of plants. The
thickness of this layer ranges from 1m to about 4m. Soil pollution refers to
the accumulation of hamrful foreign substances like toxic chemicals,
pesticides, salts, radio-active waste and disease causing agents that ultimately
alter its true fertile nature.
The major pollutants causing soil pollution come
from domestic waste, industrial waste and agricultural operations. The domestic
waste include kitchen garbage, empty bottles, plastic, cloth pieces etc, that
are dumped into the soil. The industrial waste causing soil pollution is
generated from
paper, textile, petroleum, sugar, cement, leather
and chemical plants. Different agrochemicals (herbi-
cides, fungicides, pesticides and fertilizers) used
in agriculture deteriorate the natural quality of soil.
Heavy rainfall and strong winds also result in loss
of the usefull topsoil. This phenomenon is known as
soil exosion.
Pollution of soil changes its true physical,
chemical and biological characteristics, The harmful
chemicals added to the soil enter the plants and
ultimately find their way into the animal tissues, Many
health disorders such as cancer, goitre, arthritis,
ulcers, rheumatism, crippled bones and baldness are known to be caused by such
chemicals, The poisonous chemicals also kill the useful micro-organ-isms
present in the soil. The seepage of chemicals (fertilizers, pesticides) also
leads to pollution of the groundwater. Long term excessive use of fertilizers
reduces soil porosity and disturbs its water hold-ing capacity. Such soils
become more compact and hence unfit for plant growth. In water logged
soils, concentration of salts is very high and these
soils are useless and unfertile. The pathogens present in the polluted soil
cause many soil bome disease in plants and animals. In nutshell, the pollution
of soil decreases its fertility and gives rise to many health related problems.
NOISE POLLUTION :
Sound is generated by vibration of air or some other
medium. It is known as noise when it becomes too loud or disagreeable. Noise
pollution refers to generation of disagreeable loud sound
that may pose several health problems, Loudness of
sound is measured in decibel (dB). The loud-ness of normal conversation is
about 30-35dB and the average interior loudness of a home is about 4SdB. This
measurement is approximately 60-70 dB for automobiles and about 120dB for a jet
aircraft at take off. Frequency is another characteristic of sound. It is
measured in Hertz (Hz) and it denotes the number of vibrations per second. The
human ear can perceive sound waves between a
frequency range of 20Hz to 20000Hz.
The major sources of noise pollution include
industrial plants, motor vehicles, aircrafts, horns,sirens, musical
instruments, electrical appliances etc. The use of loudspeaker at religious
functions,demonstrations, marriage parties and other social gatherings also
causes noise pollution.
Prolonged exposure to noise may cause auditory
fatigue and temporary or permanent deaihess.Noise interferes with general
verbal communication causing annoyance and ill temper. In addition to
hearing loss, noise produces physiological
disturbances and stress in the human beings. It may cause
increase in heart rate, hypertension, peptic ulcers,
digestive disorders and brain damage.
RADIATION POLLUTION :
Radiation pollution refers to the emission of harmful radiations from radioactive
substances.These substances are unstable and undergo spontaneous breakdown into stable components, releas-ing energy in the form of radiation. This process is known as radioactive decay. For example, the
tadioactive nucleus of Uranium (U-235) decays over
time into lead (Pb-2007). The radiation emit-ted by radioactive substances is
also called as ionizing radiation as it has enough energy to cause ionization
of the atoms it hits. The most common types of ionizing radiation are alpha,
beta and gamma radiations.
The natural radioactivity does not pose any serious
problem of radiation pollution. Its concen-tration is very low. The major
sources of radiation pollution are the nuclear power plants, radioactive wastes
released from these plants and research stations. The nuclear fission taking
place during
explosion of atom bombs and peace time nuclear
experiments results in nuclear fallout. It gives rise to enormous release of
high energy radiations. The leakage of radioactive substances from nuclear
reactors, industries and laboratories also contribute to the radiation
pollution.
The ionizing radiation has several deleterious
effects on the living organiams. It can produce changes in the genetic
material, Le. deoxyribo-nucleic acid (DNA). These sudden, relatively stable and
inheritable changes in genetic meterial are known as mutations. Radiation
pollution may cause bruns on skin, contract, sterlity and cancer of bone, thyroid,
lung, blood and breast. Radioactive waste may enter the food-chains and becomes
dispersed in the ecosystem.
EXERCISE
(A) Very short answer type questions (1
mark each) :
1. What do you mean by environmental pollution?
2. Name different factors responsible for natural
pollution.
3. What are the causes of man made pollution?
4. What are important types of pollution?
5. Which are the major gases present in air.
6. Enlist different sources of fresh water.
7. Whats biomagnification?
8. What do you mean by eutrophication?
9. Which one is more abudant, marine water or fresh
water?
10. Where is the pollution of marine water mote
rapid?
11. Give the composition of soil.
12. What is soil erosion?
13. How is soil formed in nature?
14, Name the units for loudness and frequency of
sound,
15. Give the audible frequency range for human ear.
16. What are mutations?
(B) Short answer type questions (2
marks each) :
1. Differentiate between industrial smogand
photochemical smog.
2. How is acid rain produced?
3. What is the harmful effect of excessive emission
of CO,?
4, For what purposes we need fresh water?
5. Define water pollution.
6. How does pollution of underground water take
place?
7. What is the cause of thermal pollution?
8. Give major sources of noise pollution.
9. ‘What is radioactive decay? Give an example.
(C) Short answer type questions (4
marks each):
1. How do the fossile fuels cause pollution?
2. Give a brief account of sources of marine water
pollution.
3. How does the pollution of marine water effects the
sea animals?
4. Write a note on sources of soil pollution.
5. What are the adverse effects of noise pollution?
6. How does the pollution of soil make it unfit for
plant growth?
(D) Long answer type questions: (5
marks each):
1. Explain different sources of air pollution.
2. Describe the adverse effects of air pollution.
3. Discuss briefly the causes and consequences of
fresh wate pollution.
4. Write an account of soil pollution.
5. Whatis radiation pollution? Discuss its causes
and consequences.
