The major problem that the atmosphere is being subjected to is pollution. In India, about 100 million tons of pollutants are being added to the atmosphere annually. This figure is likely to go up in future. Polluted air is harmful to man and the biosphere on the whole, as well. This problem needs to be tackled urgently. Since all of us contribute to it directly or indirectly, we must study air pollution in detail and discuss the means of controlling and preventing it. Air pollution can be defined as 'the change of composition of air by the addition of harmful substances like the industrial and automobile gases and particulate matter.'
Sources of Air Pollution
Most of the sources of air pollution are related to man's activities as a result of the modern lifestyle. Added to this are also natural causes like the volcanoes, anaerobic decomposition of organic matter, atmospheric reactions, etc.
Burning of Fossil Fuels
Fossil fuels include petroleum and coal. Burning of coal produces a lot of smoke and dust whereas burning of petrol mainly produces sulphur dioxide. In addition to these, the pollutants include carbon monoxide (CO), carbon dioxide (CO2), nitrogen oxides, hydrocarbons, particulate matter and traces of metals.
Petrol on combustion produces carbon monoxide, hydrocarbons, nitrogen oxides, aldehydes, sulphur compounds, organic acids and ammonia and carbon particles. Incomplete combustion of petrol produces a hydrocarbon, 3,4 benzpyrene. There is more pollution during acceleration and deceleration than during constant speed.
They produce oxides, sulphur, nitrogen, hydrocarbons, particulate matter and fluorine.
Since they are coal based the pollutants are fly ash, soot and sulphur dioxide. Textile Industries
They produce cotton dust, nitrogen oxides, chlorine, naphtha vapours, smoke and sulphur dioxide.
They produce carbon monoxide, carbon dioxide, sulphur dioxide, phenol, fluorine, cyanide, particulate matter, etc.
Volcanic eruptions release oxides of nitrogen that pollute the atmosphere. Decomposition of organic matter under anaerobic conditions produces methane which on being oxidized in the atmosphere produces carbon monoxide. Decomposition of this matter also produces foul smelling gases. Photochemical oxidation of marine organic matter and biological oxidation by marine organisms produce lot of carbon monoxide on the surface of the oceans which enters the atmosphere. Major Pollutants
There are six main categories of air pollutants:
* oxides of carbon
* sulphur dioxide
* oxides of nitrogen
* inorganic particulate matter and aerosols
* organic particulate matter
Harmful Effects of the Pollutants in Air
The various categories of air pollutants and their harmful effects are summarized in the given table: Pollutant| Source/Cause| Effect|
Carbon monoxide| Automobile exhaust, photochemical reactions in the atmosphere, biological oxidation by marine organisms, etc.| Affects the respiratory activity as haemoglobin has more affinity for Co than for oxygen. Thus, CO combines with HB and thus reduces the oxygen-carrying capacity of blood. This results in blurred vision, headache, unconsciousness and death due to asphyxiation (lack of oxygen).| Carbon di oxide| Carbon Burning of fossil fuels, depletion of forests (that remove excess carbon dioxide and help in maintaining the oxygen-carbon dioxide ratio).| Global warming as it is one of the greenhouse gases.| Sulphur dioxide| Industries, burning of fossil fuels, forest fires, electric generation plants, smelting plants, industrial boilers, petroleum refineries and volcanic eruptions.| Respiratory problems, severe headache, reduced productivity of plants, yellowing and reduced storage time for paper, yellowing and damage to limestone and marble, damage to leather, increased rate of corrosion...