WEEK TWO
SUBJECT: BASIC SCIENCE
CLASS: GRADE 7
TERM: SECOND
TOPIC: ENVIRONMENTAL
POLLUTION
MEANING OF
ENVIRONMENTAL POLLUTION: Environmental pollution is the
unfavorable alteration of our surrounding wholly or largely as a byproduct of
man’s actions, through direct or indirect effects of changes in energy
patterns, radiation levels, chemical and physical condition and abundance of
organisms. Pollution is defined as an undesirable change in physical, chemical
or biological characteristics of air, water and soil (land).
TYPES OF ENVIRONMENTAL
POLLUTION:
i. Water pollution:
Water pollution is defined as the contamination of prevailing water as a result
of release of detrimental substances into the water bodies such as rivers,
oceans and lakes. In other words, water pollution occurs when pollutants are
discharged directly or indirectly into water bodies without adequate treatment
to remove harmful substances. Examples of water pollutants include oil
spillage, various insecticides, pesticide, chemical fertilizer, industrial
wastes and gamalin-20. These pollutants adversely affect the water bodies. The
specific contaminants leading to water pollution include a wide spectrum of
chemicals pathogens and physical or sensory changes such as elevated
temperature and discoloration.
ii. Air pollution: Air pollution is the introduction of
chemicals, particulate matter, or biological materials that cause harm or
discomfort to human beings or other living organisms, or cause damage to the
natural environment, or built environment, into the atmosphere. The atmosphere
is a complex dynamic natural gaseous system that is essential to support life
on the planet earth. Stratospheric ozone depletion due to air pollution has
been recognized as a threat to human health as well as to the earth's
ecosystem.
iii. Soil pollution: Soil
pollution is defined as the build-up in soils of persistent toxic compounds,
chemicals, salts, radioactive materials, or diseases causing agents, which have
adverse effects on plant growth and animal life including human beings.
CAUSES (POLLUTANTS)
Causes of water pollution:
i.
Discharge of contaminated or and heated water that has been used for industrial
purposes.
ii.
The surface run off that contains spilled petroleum products.
iii.
The surface runoff from farms, construction sites or other impervious surfaces.
iv.
The improper disposal of solid wastes like litter on a localized scale.
v.
Addition of excessive nutrients by runoff containing detergents or fertilizers
known as eutrophication.
vi.
Maltreated sewage discharge in a wrong manner.
vii.
Oil spillage, coming out from wrecked oil tankers, forms oil slicks which
disturbs the ecosystem of water bodies. It may cause organisms to migrate from
one place to another.
viii.
Untreated sewage contains detrimental microorganisms that can cause diseases
like typhoid, dysentery and cholera.
ix.
Chemical fertilizers are transported into the stream, which can lead to sudden
vegetative growth as a result, oxygen in available water reduces.
x.
Municipal, industrial and agricultural causes are different categories of the
causes of water pollution. Municipal causes are related to waste water from
homes and commercial establishments. The main aim of handling municipal waste
water is to decrease the harmful bacteria, oxygen requiring materials, mixed
inorganic compounds and suspended solids.
Causes of air
pollution:
A
substance in the air that can cause harm to humans and the environment is known
as air pollutant. Pollutants can be in the form of solid particles, liquid
droplets, or gases. In addition, they may be natural or man-made. Sources of
air pollution are given below.
(i)
Sulphur Oxides : It is produced by volcanoes and in various industrial
processes. Since coal and petroleum often contain sulphur compounds, their
combustion generates sulphur dioxide.
(ii)
Nitrogen Oxides: Especially, nitrogen dioxide is produced by high temperature
combustion.
(iii)
Carbon Monoxide : It is produced by incomplete combustion of fuel such as
natural gas, coal or wood. Vehicular exhaust is the major source of carbon
monoxide.
(iv)
Carbon Dioxide : It is a non-toxic greenhouse gas associated with ocean
acidification, emitted from sources such as combustion, cement production and
respiration.
(v)
Particulate Matter: These are tiny particles of solid or liquid suspended in a
gas. Sources of particulate matter can be man-made or natural. Some
particulates occur naturally, originating from volcanoes, dust storms, forest
and grassland fires. Human activities, such as burning of fossil fuels in
vehicles and power plants, also generate significant amount of aerosols.
Causes of soil
pollution:
Detrimental
substances dumped on the soil surface through various activities of human
beings that results into pollution are termed soil pollutants. Soil pollution
is caused by the presence of xenobiotic (man-made) chemicals or other
alteration in the natural soil environment. This type of pollution typically
arise from the rupture of underground storage tanks, application of pesticides,
percolation of contaminated surface water to subsurface strata, oil and fuel
dumping, leaching of wastes from landfills or direct discharge of industrial
wastes to the soil. The most important chemicals involved are petroleum
hydrocarbons, solvents, pesticides, lead and other heavy metals. Occurrence of
this phenomenon is correlated with the degree of industrialization and
intensities of chemical usage. Treated sewage sludge, known in the industry as
bio-solid has become controversial as a fertilizer to the land. As it is the
byproduct of sewage treatment, it generally contains contaminants such as
organisms, pesticides, and heavy metals other than soil.
THEIR EFFECTS AND
METHODS OF CONTROL:
Control measures of
water pollution:
(i)
Control use of fertilizers and agricultural herbicides, insecticides and
pesticides.
(ii)
Take notice of proper and suitable sewage disposal system.
(iii)
Use modern techniques for the avoidance of oil spillage.
(iv)Domestic
wastes and industrial wastes should not be dumped in water bodies.
(v)
Gamalin-20, which kills the other inhabitants of water, should be avoided
during fishing.
(vi)Sewage
dumping into pond, lakes and agricultural fields should be prohibited.
Consequences of air
pollution:
(i)
Due to Carbon Monoxide: For the active site on the haemoglobin of human blood, carbon monoxide (CO) competes
with Oxygen (O,). It reduces oxygen-carrying capacity of red blood cells
(RBCs). It causes suffocation and ultimately leads to death.
(ii)
Due to Particulate Matter and Dust: Dust particles cause irritation to human
eyes. It chiefly affects breathing system and lungs, as a result asthma may
take place.
(iii)
Due to Sulphur Dioxide: Sulphur dioxide (SO,) affects respiratory organ, i.e.,
lungs. When dissolved in rainwater, it forms acid rain which can affect plants
and animals adversely. The acid rain also corrodes buildings and historical
monuments.
(iv)
Due to Oxides of Nitrogen: Oxides of nitrogen, when dissolved in water, form
acidic solution. This acidic solution corrodes building materials
It
also irritates human eyes, and causes suffocation in breathing. This
suffocation may lead to death.
(v)
Due to Smoke: Smoke may cause irritation in eyes, breathing disorder, reduction
in plant yield by reducing photosynthetic rate, etc.
Control measures of air
pollution:
(i)
Heavy industries and factories should be established far away from residential
areas.
(ii)
Factories and industries should be equipped with tall chimneys to allow smoke
to pass out directly into the air.
(iii)
People should be encouraged to plant trees.
(iv)Government
should take measures to limit emissions of carbon dioxide and other greenhouse
gases.
(v)
Exhausts from vehicles should be reduced.
Effects of soil
pollution:
(i)
Synthetic Fertilizers: Excess use of fertilizers destroys the microbial plant
life in the soil, thus leading to disturbance of essential processes in soil
such as nitrogen fixation.
(ii)
Pesticides: Pesticides are often used to keep away pests which damage the crop
produced and often cause soil pollution. They enter the marine environment and
enter the food chain. Solid, liquid and
(iii)
Industrial Effluents gaseous pollutants from thermal power plants and other
heavy industries enter the soil and cause dreadful conditions of soil due to
their toxicity.
(iv)
Non-Biodegradable Wastes: Urban wastes like plastics, broken bottles tend to
remain in soil and affect soil yield.
(v)
Toxic chemicals affect plant growth and animal life
Control measures of
soil pollution:
(i)
By reducing the use of chemical, fertilizers and pesticides.
(ii)
Recycling and reusing of materials such as glass containers, plastic bags,
paper, cloth etc, at domestic levels rather than disposing the solid waste.
(iii)
Wastelands, soil erosion and floods can be controlled by reforestation.
(iv)
Biological treatment of waste using anaerobic microorganisms is advisable as it
helps to break down the soil wastes into a less toxic and biodegradable form.
ASSIGNMENT
OBJECTIVE QUESTIONS:
1. The following solid particles cause
environmental contamination of the air EXCEPT A. carbon (IV) oxide B. dust C. pollen
D. sand E. saw-dust
2.
Which of these materials is biodegradable? A. Cans B. Glasses C. Irons D.
Papers E. Tyres
3.
The effects of soil pollution include the following except A. degradation of the environment B. increase in nutritional
value of the soil C. loss of livelihood to farmers D. loss of soil organism E.
poor plant yields
4.
Any substance which cause pollution is called A. vector B. pollutant C. causal
organism D. none of these E. all of these
5.
Oxides of sulphur and nitrogen are pollutants of – A. air B. water C. soil D.
none of these E. all of these
6.
All these causes water pollution EXCEPT A. chemical fertilizer B. mal-treated
sewage C. oil spillage D. sulphur dioxide
THEORY:
1.
Differentiate between environmental pollution and pollution.
2.
List and explain three types of environmental pollution.
3.
State two causes of pollution of the three types of environmental pollution
listed above.
4.
State two effects of pollution of the three types of environmental pollution
listed above.
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