INDIAN SCHOOL AL WADI AL KABIR

DEPARTMENT OF SCIENCE-2017-18

CLASS: VIII HANDOUT -POLLUTION OF AIR AND WATER

Air and water are two of the most important natural resources .Both are necessary for the survival of all living organisms.But various human activities have contaminated air and water.

Pollution

The contamination of natural resources, like air and water by the addition of harmful substances is called pollution.

Pollutant

Any substance that causes pollution is called a pollutant.

Air pollution

The contamination of air with harmful, unwanted substances like toxic gases smoke and dust which have harmful effects on both living and non-living objects is called air pollution.

Air pollutant

The harmful and unwanted substances which contaminate the air are called air pollutants .eg Sulphur dioxide, carbon dioxide

Causes of air pollution

Industries, vehicles, increase in population and urbanisation are some of the major causes for air pollution

Natural causes:Dust storm in deserts, smoke from forest fires and grass fires, volcanic activity etc. . . .

Human activities

Causes of air pollution / Harmful effects
Automobile emissions / Release smoke which contain carbon monoxide, carbondioxide, Chlorofluorocarbonetc.
Industries / Coal is the main fuel in industries combustion of coal release air pollutants such as Sulphur dioxide, carbon dioxide, smoke dust and fumes. Sulphur dioxide, carbon dioxide causes acid rain and smog.
Suspended particulate matter (SPM)-the minute solids in the air in the form of smoke or dust that can remain suspended for long periods. / Main source of haze which reduces visibility.
Causes respiratory problems
CFC- Chlorofluorocarbon
Compound containing carbon, chlorine, and fluorine. / Causes damage to ozone layer that protects the earth from the sun’s ultraviolet radiation.
Exposure to UV radiation causes skin cancer, eye damage etc.
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Sulphur dioxide released from thermal power plants, petroleum industry and oil refineries. / Causes heart and respiratory diseases, affects growth and reproduction of plants, and also result in acid rain.
Lead from automobile exhausts / Dangerous for small children and can lead to lower IQ’S kidney problems, for adults heart attacks or strokes
Carbon dioxide / Increases atmospheric temperature causing greenhouse effect ,increases acidity of sea water,decreses availability of carbonates for forming shells for aquatic animals
Carbon monoxide / Combines with haemoglobin of blood and reduces oxygen carrying capacity as it forms carboxyhaemoglobin

Effects of air pollution:

Air pollution effects plants,animals andalso climatic conditions.

Smog (smoke + Fog):It is formed when various gases with water vapour and smoke settle on dust particles .These gases are formed when fuels are burnt. Smog reduces visibility and causes a haze similar to fog, but very different in composition. It decreases the capacity of the lungs cause shortness of breath, pain when inhaling deeply, wheezing and coughing .It can cause eye and nose irritation.

Acid rain: It occurs when Sulphur dioxide and nitrogen dioxide produced from burning fossil fuels combine with water vapour in the atmosphere and falls as snow, rain or fog. It causes damage to water, forest soil resources and human health. It can react with marble and affects all buildings, monumentsand statues made of marble.

Steps to check air pollution:

*using alternate sources of energy like solar and nuclear energy.

*preventing the mixing of harmful gases with air using air filters.

*using unleaded petrol and regular pollution checking of vehicles

* using CNG as domestic fuel

* Growing moretrees to absorb carbon dioxide and switch to carpooling or using public transport.

Water pollution

It is the contamination of waterbodies by discharge of undesirable substances that are toxic and poisonous

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Sources of water pollution

Domestic sewage / Waste generated in homes, food wastes plastic wrappers, soaps and detergents. / Microorganisms present in the wastes multiply and reduces the concentration of oxygen in water bodies leading to death of aquatic lives.
Agricultural run off / Excess use of fertilizers, pesticides etc., seep into ground water / Causes eutrophication,( a condition by which water bodies get enriched with nutrients that allow rapid growth of algae that utilize dissolved oxygen leading to oxygen depletion in water making it unfit for other aquatic forms to survive) which leads to growth of weeds in water bodies that use up almost all the oxygen present in water
Industrial effluents / Waste water and chemicals from industries / Chemicals like mercury,lead, copper,cadmium etc.,affects the nervous system and cause skin diseases, endangers aquatic life.
Oil spills / Leakage of oil and petroleum into the oceans / Endangers life of marine plants and animals
Thermal pollution / Hot water expelled from power plants to water bodies increases the temperature of water bodies / Reduces oxygen content,kills aquatic organisms

All types of water pollution are harmful tothe health of humans and animals. It may not damage the health immediately but can be harmful in the long term exposure.It causes water borne disease like typhoid, cholera and jaundice.

Steps to prevent water pollution:

*Do not litter water bodies.

*Industrial wastes should be treated before dumping into water bodies.

*Excreta and other wastes should be used to produce fuel as bio gas.

*Garbage and carcasses should not be thrown in water bodies

*Excessive use of chemical fertilisers should be reduced and bio fertilisers and bio pesticides to be used Page 3 of 4

*Both government and industries should take the responsibility of cleaning water bodies.

*Sewage treatment plants should be more in number to treat sewage before dumping in water bodies.

*Turn off taps when not in use.

Potable water:

Water fit for consumption by humans and other animals.it is also called drinking water.

The basic properties of potable water:

*it should be colorless and odourless.

*it should be free of any suspended impurities, germs and pathogens

*should contain essential amounts of dissolved mineral salts of sodium, calcium and magnesium essential for physiological processes.

* should contain dissolved gases.

Purification of water:

The water that is obtained from various resources contains soluble and insoluble impurities. It has to be purified before it is used for drinking and other domestic needs.

Purification for public distribution

It is done in water treatment plant

Water from water source is passed through screen filters to remove big particles, it is then send to treatment plant for purification. At the treatmentplant muddy water is made to stand in large tanks for a long time. Due to this most of the heavy impurities settle down sedimentation tanks. Later alum is added to remove suspended impurities. Clear water is then send for filtration. Filtering is done by passing water through layers of gravel, pebbles, broken bricks charcoal and sand. Charcoal is used to remove coloring matter. Chlorination is a process of adding bleaching powder in calculated amounts to kill harmful germs. Chlorinated water is then tested for purity and pumped into public water supply.

Methods to purify water at homes:

1.  Boiling: can be used for small quantities of water, and kills germs.

2.  Chemical treatment: by adding disinfectants like potassium permanganate and bleaching powder. The water thus treated has to be boiled before drinking

3.  Water purifying gadgets: Modern purifying gadgets involve use of ceramic candles with fine pores for removing suspended impurities. Some purifiers use activated charcoal and ultraviolet rays along with ceramic filters to purify water.

Prepared by Rexy Ninan Page 4 of 4