Ans: Air Pollution
Air pollution is one of the major environmental issues of today.
It is defined as the change of composition of air by the addition of harmful substances (e.g. industrial and automobile gases and particulate matter).
Sources: All sources of air pollution are related to human activities. Burning of coal produces a lot of smoke and dust whereas burning of petroleum produces sulphur dioxide. In addition to these, air pollutants include carbon monoxide, carbon dioxide nitrogen oxides, hydrocarbons, particulate matter and traces of metals.
Different industries.produce air pollution in the following ways:
i) Fertilizer industries release oxides of sulphur and nitrogen, hydrocarbons, particulate matter and fluorine.
ii) Thermal industries are coal based and their pollutants are fly ash, soot and sulphur dioxide.
iii) Textile industries release cotton dust, nitrogen oxides, chlorine, smoke and sulphur dioxide. '
iv) Steel industries release carbon monoxide, carbon dioxide, sulphur dioxide, phenol, fluorine, cyanide, particulate matter etc.
Effects of Air Pollution
Studies show that global warming is one of the consequences of air pollution. Other effects of air pollution are as follows:
(a) Smog formation: When pollutants like hydrocarbons and nitrogen oxides combine in the presence of sunlight, smog is formed. This is a mixture of gases. It forms a yellowish brown haze especially during winter and hampers visibility. It also causes many respiratory disorders and allergies as it contains polluting gases.
(b) Acid rains: The air pollutants like sulphur dioxide and nitrogen oxides react-with water in the atmosphere producing acid rains.
(c) Ozone depletion: The upper layer (stratosphere) of the atmosphere has ozone (O3) which absorbs ultraviolet (UV) rays present in the sun's radiation. However, the air pollutants like chlorofluorocarbons (CFCs) destroy the ozone molecules and so break the ozone layer. Ozone holes are created which permit UV rays to reach the Earth's surface. The UV rays increase the temperature and also cause skin cancers.
Control of Air Pollution
For effective control of air pollution, it is important to create public awareness about the ill-effects of air pollution. Air pollution can be controlled by the following ways:
a) Afforestation: It means the establishment of new forests by planting on .non-forest areas. Forests are effective means to control air pollution because plants can filter and absorb air pollutants.
b) Modification of Industrial Effluents: The air pollutants coming from industries should be passed through filters and other devices, so that the particular matter is removed before the waste gases are released out. The smoke producing units should have long chimneys to take the polluting gases far above and then disperse over a larger area. Industries should also invest for solar cookers or for producing bio gas.
c) Environment Friendly Fuels: Lead-free fuels should be used in automobiles. Similarly, sulphur-free fuel should be used in coal-based industry to reduce pollution by sulphur dioxide. .