AIR POLLUTION NOTES

AIR POLLUTION NOTES

AIR POLLUTION:

     Air pollution is the outcome of any change in the composition of air, either by physical or chemical methods that cause harmful effects on health.

Sources of Air Pollution:
There are two sources namely,
     1. Natural sources
     2. Man-made (anthropogenic) sources.

Natural sources:
     Volcanic eruption, forest fire, sea salt sprays, biological decay, photochemical oxidation of terpenes, marshes, pollen grains, and spores are some natural sources. Radioactive minerals present in the earth’s crust are the sources of radioactivity in the atmosphere.

Man-made sources:

     Industrial emissions, vehicles, aeroplanes, power-stations, burning of fuels, etc.,are man-made sources. Air pollution is caused mainly due to burning of fuels to run vehicles and the smoke emanating from chimneys of factories and power stations.

The Greenhouse Effect:
     Some of the infrared radiation from the earth passes through the atmosphere but most of it is absorbed and re-emitted in all directions by greenhouse gas molecules and clouds. This warms up the Earth’s surface and the lower atmosphere.

Air Pollutants:
     The following table shows a few air pollutants and their effects on human health and environment.

Acid Rain:
    Oxides of nitrogen, sulphur, and carbon produced by combustion of coal, petroleum, etc,. dissolve in atmospheric water vapour. They form their corresponding acids like nitric acid, sulphuric acid, etc., and reach the earth’s surface as acid rain. 

Effects of acid rain:

• It irritates the eyes and the skin of human beings. 
• It inhibits germination and growth of seedlings. 
• It affects the fertility of soil, destroys plant and aquatic life. 
• It causes corrosion of many buildings, bridges, etc., 

     The increase in the concentration of greenhouse gases (CO 2 , methane) in the atmosphere allows radiations of short wavelength reflect back to earth. The consequent increase in the global mean temperature due to greenhouse gases is called global warming.

Ozone Depletion:

     Ozone is a colourless gas, found in the upper atmosphere (stratosphere) and is highly beneficial. The Ozone layer is thinning due to the emission of pollutants into the atmosphere. Holes caused in the ozone layer allow the harmful UV rays to reach the earth.

Control of air pollution:
     Air pollution can be minimized by following ways: Use of crude oil should be avoided and use of high quality fuels, unleaded petrol, bio-diesel and Compressed Natural Gas (CNG) should be recommended. Use of automobiles should be minimized. Industrial smoke must be filtered before releasing it into the atmosphere. Planting of more trees to get pure air (O 2) and reduce the CO 2 content in the environment.