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Thursday, October 16, 2014

Major Gaseous Pollutant

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Substances that cause pollution of air are called as air- pollutants. These pollutants can be       put into two broad categories A. Gaseous Pollutants, and B. Particulates.
The gaseous pollutants causing air pollution are numerous. Some remarkable gaseous pollutants in the present context are being mentioned below.
1.           Sulphur dioxide: Sulphurdioxide (SO2) and sulphur tri- oxide (SO3) are produced largely by the combustion of coal and petroleum. These are also produced through smelting of ores of sulphide, copper, zinc, and lead; and decomposition of bio-mass. Some industries that emit sulphur dioxide are industries manufacturing sulphuric acid (H2SO4), oil refineries, fertilizer industries and paper industries.
2.           Hydrogen sulphide: It is a colourless toxic gas which is produced from decaying vegetation and animal materials particularly in shallow fresh water and marine environment. It also comes out from sulphur springs, volcanoes, coal pits and sewers.
3.           Carbon monoxide: It is a poisonous gas which originates from incomplete combustion of carbonaceous materials. It can also be oxidized to carbon dioxide which too is a poisonous gas.
4.           Hydrogen fluoride: It naturally comes out from volcanoes. However, it is produced from blast furnaces and industries concerned with the production of brick, tiles and super phosphates. It also comes out during combustion of coal.
5.           Hydrogen chloride: It comes out during the combustion of coal, paper, plastics and chlorinated hydrocarbons.
6.           Hydrocarbons: Chemical compounds made of hydrogen and carbon, are called as hydrocarbons. Methane, ethylene and aniline are three examples of hydrocarbons. Methane is the principal constituent of the natural gas. Major sources of release of hydrocarbons are organic matter, seepage from natural gas and oil fields and emissions of Volatile Organic Chemicals (VOCs). Hydrocarbons are also produced due to incomplete combustion of fuels, automobile exhausts, petroleum refineries, burning of crop residues, cracking of natural gas in petrochemical plants etc.
7.           Ammonia: This gas is principally generated through refrigerator pre- cooler system of cold storage, manufacture of anhydrous ammonium fertilizers, nitric acid and domestic incineration etc. The emission of ammonia causes bleaching of plant-leaves reduction of root and shoots growth, browning and softening of fruits, reduction in the rate of germination etc.
8.           Nitrogen Oxides: Nitrogen oxide and Nitric Oxide are principal gaseous pollutants emitted through human activities. Nitrogen oxides have been reported to cause fading of colours of clothes, deterioration of nylon and cotton and corrosion of metals.
9.           Tobacco Smoke: Smoking of cigarettes and allied things generate tobacco smoke. It is a potent pollutant in closed atmosphere like buses; trains etc. It causes lung cancer, pulmonary and coronary heart diseases. Even passive smokers may be caught by a pulmonary or a coronary disease.

Key Words:major, gaseous, pollutants

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