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MHT-CET : Biology Entrance Exam

MHT - CET : Biology - Pollution Page 1

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Pollution

  1. Pollution is an undesirable change in the physical, chemical and biological characteristics of water, air and land, which is harmful to plant and animal life.
  2. Substances which cause pollution are called pollutants. E.g: toxic chemicals, radioactive materials, heat, etc.
  3. There are two main types of pollutants, namely,
    • Biodegradable or degradable pollutants, and
    • Non-degradable pollutants
  4. The pollutants, which are biologically degradable, are called degradable or biodegradable pollutants.
    Degradable pollutants are of two types, viz.;
    • Rapidly degradable, e.g. animal and crop waste and
    • Slowly degradable, e.g. fertilizers and chemicals.

 

  1. The pollutants, which do not undergo degradation, are called non-degradable (non-biodegradable) pollutants.
    Non-degradable pollutants produce toxic, harmful substances when they accumulate in dangerous proportions in the biosphere. E.g: mercuric salts, DDT and phenolic compounds.
    Polythene bags and plastic articles, which cause solid waste pollution, do not disintegrate naturally.
  2. Air Pollution

a)

Sources Of Air Pollution

                                 The main source of air pollution is burning. E.g. burning of wood, fossil fuels, garbage, cigarettes, etc.
Burning results in release of harmful substances such as carbon monoxide, sulphur dioxide, hydrocarbons, soot and others in the air.

                                 Suspended particles are produced by construction and demolition activities. Certain industries like cement and asbestos also add to these suspended particles.

b)

The Main Air Pollutants are

                                 Oxides of carbon

                                 Oxides of sulphur

                                 Oxides of nitrogen

                                 Hydrocarbons

                                 Chloroflurocarbons

                                 Particulate materials

c)

Control Measures to Curb Air Pollution

 

Scientific Methods

                                 Equipment installed in factories and automobiles is designed to limit the pollutants released in the process.

                                 Methods of manufacture and working of machines are changed so as to reduced air pollution.

                                 When both the above methods are not possible, the particular process of manufacture or the machine is given up or safer fuel is used.


Other Methods

                                 Use of sulphur-free fuels in industries and automobiles. This reduces the emission of SO2.

                                 Automobiles are equipped with catalytic converters. These converters reduce the pollutants in the exhaust.

                                 Various types of filters can be used to prevent the particulate pollutants from entering the atmosphere.

                                 Products like aerosol spray, which cause air pollution, should be banned.

                                 Alternate technologies that do not produce harmful pollutants should be developed.

 

  1. Water Pollution

a)

Sources Of Water Pollution
The main sources of water pollution are:

 

                                 Acid rain

                                 Sewage

                                 Industrial waste

                                 Agricultural drainage

                                 Radioactive waste

                                 Oil spills

b)

Serious Problems Posed by Water Pollution

 

                                 Toxins in Industrial Wastes
The toxins in industrial wastes may vary with the type of industry producing the waste.
The various types of toxins produced by the industries are
fluorine, lead, mercury, cadmium, arsenic, chloroform, polychlorinated biphenyls (PCBs)
The toxins percolate through the soil and affect the ground water.

Effect of Toxins
Prolonged exposure to toxins is harmful and may cause cancer.
Mercury causes damage to the nervous system.
The presence of PCB in the body results in birth defects and cancer.

                                 Thermal Pollution
Thermal pollution is also caused by industrial waste.
The waste water used in cooling towers is hot and increases the temperature of the water body in which it is released.
These harmful effects are produced due to the following reasons;
Heat reduces the solubility of oxygen in water.
Acquatic organisms cannot survive at higher temperature.
The reproductory activities of animals are also affected by high temperature.

                                 Eutrophication
Eutrophication is a process by which sewage effluents and salts released from agricultural fields cause a lake or a pond to become highly rich in organic and mineral nutrients. Owing to this, the algae grow rapidly and deplete the oxygen supply.

Effects Of Eutrophication
Eutrophication leads
to algal blooms.
Eutrophication reduces the oxygen level in water bodies.
The death of these algae increases the decomposing micro-organisms which use more oxygen from water.
The oxygen in water is decreased, thus rendering it unfit for fishes and other aquatic living organisms that die out without oxygen.

                                 Biological Magnification:
The phenomenon of concentration of harmful substances inside the body is called biological magnification.
Non-degradable pesticides (like DDT and dieldrin) and inorganic toxins (like mercury) reach water through agricultural and industrial drainage. On their absorption by plants and planktom, they get circulated through the food chain. These substances cannot be excreted, and hence, they get stored in certain tissues of animals. The predators who eat such polluted prey die due to poisoning when consumed in large quantities. Human beings, on consumption of fishes from polluted water, can from biological magnification.

c)

Control Of Water Pollution

 

                                 Sewage treatment

                                 Waste treatment

                                 Modification of manufacturing processes

                                 Water purification

                                 Tremination of polluting processes

 

 

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