Page 208 - Science Class 08

Sources of Air Pollu on Effects of Water Pollu on
Let us study about some important sources of
water pollu on:
Discharge of Domes c Wastes : Domes c
wastes include human excreta, animal wastes,
organic food materials and inorganic salts like
nitrates and phosphates of detergents and also
sodium calcium, potassium and chloride ions.
When these domes c wastes are discharged in
water bodies they make them polluted.
Industrial Effluents : Industrial effluents discha-
rged into water bodies are the main source of
water pollu on. Industrial effluents discharged
by tanneries, breweries, dying tex les, paper
and pulp mills etc., include organic as well as
inorganic pollutants. These pollutants include
acids and alkalies, fluorides, free ammonia,
lead, etc.
Agricultural Discharge : Excessive use of
chemical fer lizer, pes cides, herbicides, etc.
are also responsible for water pollu on. Some
quan ty of these chemicals percolate through
soil along with water into the underground
water causing its pollu on. Some mes, these
chemicals are washed away into the rivers,
ponds, lakes, etc. by rain water. These
chemicals are very harmful for the human
beings as well as the aqua c organisms.
Thermal Pollu on : Water is u lised for cooling
on thermal power plants and atomic energy
plants and the resultant warm water is
discharged into rivers, streams, lakes, etc. It
raise the temperature of water bodies causing
changes in aqua c life.
Oil spills : Discharge of petroleum products
into the sea during loading and unloading of
tankers or drilling oil wells is called oil spills.
Accidents of ships also cause oil spills. This is
very harmful for the aqua c life.
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Each type of water pollu on affects the living
organisms in different ways which have an
ul mate impact on human beings.
Some of the major effects of water pollu on
are:
v Disposal of domes c wastes into the water
bodies give rise to pathogenic micro-
organisms (bacteria, viruses and proto-
zoans). These micro-organisms may cause
typhoid, dysentery, poliomyeli s and
hepa s.
v The toxic wastes discharged by industries
may cause death of animals or may damage
our liver, kidneys, reproduc ve system,
respiratory system or even nervous system.
Mercury caused a crippling and fatal
diseases called Minamata disease in a
group of fishermen in Japan.
v Agrochemical include many toxic subst-
ances which do not only destroy pests and
insects, but also destroy many useful
organisms and by ge ng deposited in
fishes they reach the ssue of human
beings.
v Some plants especially thermal power
plants discharge very hot water which can
kill aqua c animals.
Eutrophica on : It is a natural process which
literally means, “Well nourished or enriched”. It
is natural state in many lakes and ponds which
have a rich supply of nutrients and it also
occurs as a part of the ageing process in lakes,
as nutrients accumulate through natural
succession. Eutrophica on becomes excessive
when abnormally high amounts of nutrients
from sewage, fer lizers, animal wastes enter
streams and lakes causing excessive growth of
micro-organisms and aqua c vegeta on.
Science-8