The concentration of substances like pesticides increases as they pass from organisms of one trophic level to another, 1resulting into highest resulting Concentratioon in into highest concentration in the terminal
organism of food chain. This is called

biomagnification.

DDT is the most striking example
of biomagnification.It is non-
biodegradable. Once it is absorbed by
non- an organisms, it can not be metabolised
or excreted out. It remains
accumulated in the body tissues. In
this way its concentration continue to
rise up and reach dangerous level, that
may cause the death of the organisms.
When these organısms are eaten by
other organisms (at higher trophic
level), the Concentration of DDT
becomes still higher. For example, the
zooplanktons contain about five times
greater DDT concentration than
phytoplanktons.Similarly, aquatic
DDT
birds show 25 times greater DDI
concentration, than in the fishes.

Bhopal Gas Tragedy

India witnessed, one of the largest of the industrial disasters on 3rd Dec, 1984.It
ed by leakage of meth hyl-iso-cyanate (MIC), which is used in the manufacture
icide-Savin by Union carbide at Bhopal. The leakage killed about 2.000
people and large number of animals.

Groundwater Pollution

Cround water is the major source ot drinking water lor human beings. Itis also
an important source or water lor irigation.

Contamination ot ground water, due to sewage from industrial effluents.
municipal wastes, sewerage channels and agricultural runoff is the major problem in India.

The contaminated water has excess of nitrates which may be dangerous for
human beings.

It reacts with haemoglobin and forms nonfunctional methaemoglobin. This
haemoglobin inhibits the oxygen transport through blood, resulting into
hypoxia and consequent death. This condition is called methaemoglobinemia. In children, it is called blue-baby syndrome.

The contaminated ground water also contains excess of fluorides which cause
teeth deformity, hardened bones and stiff and painful joints (skeletal fluorosis).

At many places in India, groundwater is contaminated with arsenic, mainly
from naturally occurring arsenic in bedrocks. Chronic exposure to arsenic
causes black-foot disease.

Arsenic also causes diarrhoea, peripheral neuritis, hyperkeratosis, and also lung
and skin cancers. Ground water at many places, also contains an heavy amount
of dissolved salts. These salts make the water hard and unfit for drinking.

Control of Water Pollution and Improving Water Quality

The following are some common methods used to control water pollution-

(a) Precipitation of phosphate by using lime, ferric chloride, calcium oxide, calcium
hydroxide, alum or zirconium should be done.

(b) replacement of non-biodegradable alkyl benzene sulphonate (ABS) by
degradable linear alkyl sulphonates (LAS) is suggested.

(c) Septic tanks, oxidation ponds, filter beds, etc., are used to reduce the amount of organic substances.

(d) Revers osmosis is a relatively new process which may help in recycling ciean drinking water.

(e) Pesticides should be used with care and especialy unde and especially under the supervision of
for replacement of the more harmful specialists. A search should be made for replacenct of the more harmful chemicals by bio-degradable compounds.

(f) Waste Sewage water can be treated in an ‘effluent treatment plant.

Tags: Biomagnification