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AIR POLLUTION
Contamination of air with smoke, dust and harmful gases is called air pollution and the substances causing pollution are called as pollutants.
The common pollutants are:
Gases like sulphur oxides, nitrogen oxides, carbon oxides and hydrogen sulphide, smoke soot and particulate matter etc.
SOURCES OF AIR POLLUTION
- Burning/combustion of fuel: Burning of fuel for household purposes generates gases like carbon dioxide, carbon monoxide as well as soot and particulate matter.
- Vehicular emission: Gases emitted from the exhausts of motor vehicles contribute significantly to the air pollution. These gases are nitrogen oxides, sulphur dioxide, carbon monoxide, hydrogen sulphide etc.
- Industrial emission: With the increase in population, the numbers of industries are increasing day-by-day. They emit harmful gases and smoke. For example, operations like mining of coal release dust into the atmosphere.
- Emissions from power plants: Thermal power plants and nuclear power plants release harmful gases, smoke and radioactive pollutants.
- Deforestation: Trees absorb substantial amount of carbon dioxide from the atmosphere. Hence, cutting of trees pollutes the atmosphere increasing the amount of carbon dioxide into it.
- Use of chlorofluorocarbons (CFCs) in refrigerators, fire extinguishers, aerosol sprays etc. leads to release of harmful gases that deplete the ozone layer.
OZONE DEPLETION
The atmosphere of our earth is surrounded by an ozone layer which protects both plants and animals on the earth by absorbing harmful ultraviolet radiation of the sun. but this layer has started depleting because of chlorofluorocarbons (CFCs) released from leaky refrigerators, air conditioners etc.
A hole was discovered in the ozone layer right above the Antarctica by NASA in September 2004. It was found to be expanding continuously exposing some populated areas of South America to the harmful ultraviolet rays of the sun.
The CFCs released by us in the atmosphere convert ozone into oxygen. This reduces the amount of ozone in the ozone layer and creates a hole in it.
The depletion of ozone layer affects the health of animals and human beings who are now exposed to a higher level of UV radiation. They may develop skin cancer and eye problems if exposed to these rays for prolonged periods. Exposure to UV rays affects the crops also that to very adversely.
Q.1. Which amongst the following is not an example of air pollutant:
- Hydrogen sulphide
- Hydrogen gas
- Carbon monoxide
- Sulphur dioxide
Ans.b
Q.2. Ozone protects us from:
- UV rays
- Infra red rays
- Visible rays
- None
Ans. a
Q.3. Ozone layer is present in the:
- Troposphere
- Stratosphere
- Mesophere
- Ionosphere
Ans. b
Q.4. Deforestation refers to:
- Cutting of trees
- Planting of trees
- Replanting the trees
- Planting trees in a society
Ans. a
Q.5. Burning of fossil fuels generate:
- Carbon dioxide
- Carbon monoxide
- Particulate matter
- All
Ans. d
