Air Pollution
Definition :
The contamination of air with foreign substances such as dust, smoke, fumes, etc., from natural and man-made sources (industries) is called air pollution. The substances which pollute air are called air pollutants.
Composition of Air:
Air is a mixture of gases. The average composition of clean dry air near sea level.
Sources of Air pollution:
Industries:
Oil refineries, cement factory, ceramic factory, paper mill, chemical plants, mines and quarries are responsible for about 20% of total air pollution. They release acid fumes, smoke, dust and poisonous gases.
Automobile exhausts are responsible for more than 75% of the total air pollution. Automobile release poisonous gases such as carbon monoxide, oxides of nitrogen, hydrocarbons and particulate lead.
Agrochemicals:
Crops spraying and dusting with pesticides in agricultural practices also cause air pollution.
Burning of Fossil fuels:
Burning of Fossil fuels like coal, oil and natural gas in our homes and factories release poisonous gases such as CO, CH4, SO2, NO, NO2, etc.,
Deforestation :
Plants purify air by taking in CO2 for their use in photosynthesis. Deforestation by man will increase atmospheric CO2.
Population growth:
CO2 gas is released by the respiration of man and animals. Population growth will cause an increase in concentration of CO2 in the atmosphere.
Volcanic eruptions:
The ash released during volcanic eruptions pollute air. It contains poisonous gases like SO2, H2S and CO.
Hazards of air pollution:
Carbon monoxide:
It is produced by incomplete combustion of any carbon containing fuel like petrol in motor vehicles. It is deadly poisonous gas. It produces varieties of symptoms from discomfort through headache, visual difficulty, ataxia, paralysis, coma and deaths.
Sulfur dioxide:
SO2 is oxidized to SO3 by air. It dissolves in the moisture in air and is converted into H2SO4. This H2SO4 is injurious to human beings. Besides, it attacks marble, lime stone, roofing slate, vegetation, electrical contacts, paper and textiles. It dissolves even nylon products. Taj Mahal is deteriorated by SO2 and CO2 emitting by nearby railway yard and foundries in and around Agra. A refinery is going to increase the damage to Taj Mahal.
Nitrogen Oxides:
NO and NO3 mainly pollute air. NO causes chronic lung diseases which may cause even death. It causes chlorosis and extensive leaf drop in plants.
The aerosols produced in various photochemical reactions create a white haze called smog, which reduces visibility in roads.
Another type of smog is called industrial smog or London smog.
Acid rain:
Sulfur and nitrogen oxides are converted into sulfuric and nitric acid through a series of complex reactions in the atmosphere, come down to earth by rain or snow. Such a rain is contaminated with acids is called acid rain.
Acid rains have several ecological impacts. It makes lakes water acidic. So fishes cannot live in such lakes. Agricultural yield decreases. Stone monuments are destroyed. Trees become eroded and become sick.
Green house effect:
A Green house is a light structure with glass walls and roofs to rear delicate plants or to hasten the growth of a plant. In the green house, the glass window admit the solar radiation but partially trap the IR radiation reradiated from within and return part of it back into the green house.
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