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Discuss in detail about the gaseous air pollutants. |
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Answer» Solution :Gaseous air pollutants `:` Oxides of sulphur, oxides of nitrogen, oxides of carbon, and hydrocarbons are the gaseous air pollutants. ( a) Oxides of Sulphur `:` (i) Sulphur dioxide and sulphur trioxide are produced by burning sulphur containing fossil fuels and roasting sulphide ores. Sulphur dioxide is a poisonous gas to both animals and plants. Sulphur dioxide causes eye irritation, coughing and respiratory diseases like asthma, bronchitis, etc. (ii) Sulphur dioxide is oxidised into more harmful sulphur trioxide in the presence of particulate matter present in POLLUTED air. `2SO_(2) + O_(2) overset("Particulate matter")(rarr) 2SO_(3)` (iii) `SO_(3)` combines with atmospheric water vapour to form `H_(2)SO_(4)` , which comes down in the form of acid rain. `SO_(3) + H_(2)O rarr H_(2)SO_(4)` (b) Oxides of nitrogen `:` (i) Oxides of nitrogen are produced during high temperature combustion processes, oxidation of nitrogen in air and from the combustion of fuels ( coal, diesel, petrol etc. ) `N_(2) + O_(2) overset( gt 1210^(@)C) (rarr) 2NO` `2NO + O_(2) overset( 1100^(@)C)(rarr) 2NO_(2)` `NO + O_(3) rarr NO_(2) + O_(2)` (ii)The oxides of nitrogen are converted into nitric acid which comes down in the form of acid rain. They also form reddish brown haze in heavy traffic. Nitrogen dioxide potentially damages plant leaves and retards PHOTOSYNTHEIS . `NO_(2)` is a respiratory irratant and it can cause asthma and lung injury . Nitrogen dioxide is also harmful to variuos textile figures and metals. (c ) Oxides of carbon `:` The major pollutants of oxides of carbon are carbon monoxide and carbon dioxides. (i) Carbon monoxide is a poisonous gas produced as a result of incomplete combustion of coal are firewood. It is released into the air mainly by automobile exhaust. It binds with haemoglobin and form carboxy haemoglobin which impairs normal oxygen transport by blood and hence the oxygen carrying capacity of blood is reduced . This oxygen deficiency results in HEADACHE, dizziness,tension, Loss of consciousness, blurring of eye sight and cardiac arrest . (ii) Carbon dioxide `:` Carbon dioxide is released into the atmosphere mainly by the process of respiration, burning of fossil fuels, forest fire, decomposition of limestone in cement industry etc. Green plants can convert `CO_(2)` gas in the atmosphere into carbohydrate and oxygen through a process called photosynthesis. ( d) Hydrocaron `:` (i) The compounds composed of carbon and hydrogen only are called hydrocarbons. They are mainly produced naturally (marsh gas ) andalso by incomplete combustion of automobile fuel. (ii) They are potential cancer causing ( carcinogenic ) agents. For example, polynuclear AROMATIC hydrocarbons ( PAH ) are carcinogenic , they cause irritation in eyes and mucous membranes. |
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