2. AIR POLLUTION
1. What is meant by air pollution?
Air pollution refers to any physical, chemical or biological
change in the air. It is the contamination of air by harmful gases,
dust and smoke which affects the plants, animals, and humans
drastically.
3. 2. Mention the composition of atmospheric air.
• Nitrogen 78% Oxygen 21% Argon 0.9%
• Carbon dioxide 0.03% Other gases 0.15%
4. 3. Discuss the classification of air pollutants with examples.
(A) Primary Pollutants
• Primary air pollutants are directly emitted from the sources into
the atmosphere
• Examples:
• (i) Inorganic gases such as SO2, NOX, H2S, CO, NH3, CO2, HF.
• (ii) Particulate matter like ash, smoke, dust, fumes, mist, spray.
• (iii) Olefinic and aromatic hydrocarbons.
• (iv) Radioactive compounds.
5. (B) Secondary Pollutants
• Secondary Pollutants are those which are derived from the
primary pollutants due to chemical or photochemical reactions in
the atmosphere.
• Examples: NO2, which is formed as NO combines with oxygen
in the air;
• acid rain, which is formed when sulfur dioxide or nitrogen oxides
react with water;
• Smog, formed by the intermingling of smoke and fog
6. (C) According to Sate of Matter:
• (i) Gaseous pollutants (Oxides of Nitrogen, Sulphur and Carbon)
• (ii) Particulate pollutants (small solid particles and liquid droplets)
• (iii) Aerosols
• (iv) Metallic components
• (v) Radioactive pollutants
• (vi) Pesticides
7. 4. Discuss the effect of air pollutants.
(i) Diseases
(lung cancer, heart diseases, asthma, allergy, pnemonia etc.,)
(ii) Global Warming
The increase of earth’s temperature due greenhouse effect
(iii) Acid Rain
The rain water become acidic, and fall as acid rain which damages
human, animal and plant life.
(iv) Ozone Layer Depletion
The depleting ozone layer does not prevent the harmful ultraviolet rays
coming from the sun and causes skin diseases and eye problems
(v) Effect on Animals
The air pollutants suspend on the water bodies and affect the aquatic life.
Pollution also compels the animals to leave their habitat and shift to a new
place.
8. 5. Write a note on (i) Greenhouse effect (ii) ozone layer depletion.
(i) Greenhouse effect:
This trapping of the sun’s heat near the earth’s surface and keeping it
warm is called natural greenhouse effect.
Greenhouse gases: Carbon dioxide, methane, ozone,
chlorofluorocarbon compounds (CFCs) and water vapours.
Global Warming: Global warming is a gradual increase in the earth’s
temperature generally due to the greenhouse effect caused by
increased levels of carbon dioxide, CFCs, and other pollutants.
9. (ii) ozone layer depletion
• Release of chlorofluorocarbon compounds (CFCs), also known as
freons lead to their mixing with the normal atmospheric gases and
eventually reach the stratosphere.
• In stratosphere,
This way, the chlorine radicals are
continuously regenerated and cause
the breakdown of ozone layer.
10. • Effects of Depletion of the Ozone Layer
• With the depletion of ozone layer, more UV radiation filters into
troposphere. UV radiations lead to:
• Ageing of skin, cataract, sunburn and skin cancer etc. in human beings
• Killing of many phytoplanktons
• Damage to fish productivity
• Affect the plant proteins which lead to the harmful mutation of cells
• Increases the evaporation of surface water through the stomata of the
leaves and decreases the moisture content of the soil
• Increases in UV radiations damage paints and fibres, causing them to fade
faster
