AIR POLLUTION Presented by Satyam Yadav
What is air pollution??? 277 The air pollution is caused due to the addition of unwanted substances or gases.The atmospheric pollution is caused by the activities of man and concentrated to the inhabited and the industrial complexes in cities. THESE ARE OF TWO TYPES; 1)Gases 2)Particulates
Gases: The gaseous materials include various gases and vapours of volatile substances or the compound with a boiling point below 200 MAJOR AIR POLLUTANTS AND THEIR EFFECTS 1.Carbon monoxide: Source-it is the main air pollutant releasedfrom smoke of automobile. Effect- CO is highly toxic gas,it combines with haemoglobinof blood and blocks the transportation ofoxygen.Thus it impairs respiration and it causes death due toasphyxiation when inhaledin larged amount.
2. Unburnt hydrocarbons- Source-These are mainly released from automobiles and burning of fossil fuels (petrol, diesel).Methane is the most abundant hydrocarbon in the atmosphere and its main source is marshy areas and paddy fields. Effect-hydrocarbons causes lung cancer. Ethylene- Source-Ethylene released in the air during ripening of fruits. ffectufling of lawvesons,fallig of flowerng bud before time.
4.Nitrogen oxide Source-Burning of fossil fuel in automobiles. Effects-These nitrogen oxide forms photochemical smog in the atmosphere and released ozone.Nitrogen oxide also responsible for rain.lt causes emphysema, bronchitis, swelling of lungs, and lungs cancer etc. 5.Sulphur oxide- Source-These are most harmful gaseous pollutants, the main source of sulfur oxides are coal burning, smelters, oil refineries. Effect-Lichen and mosses do not grow in polluted areas.These are indicators of pollution.lt causes chlorophyll destruction.
Control of air pollution- 1)Control of particulate matter - Two devices are used to remove particulate air pollutants. (a)Arresters (b)Scrubbers ARRESTERS: These are used to separate particulate matters from contaminated air. Arresters of different types: A- Cyclonic separators or trajectory separators- Commonly used for separate out particulate matters from industrial emissions with minimum moisture content.these work on the principle of dust separation by centrifugal force.
b) electrostatic precipitators : It is the most efficient device to remove fine particulate pollutants.it works on the principle of electrical charging of dust particles and collecting it on a differently charged platform These are several ways of removing particulate matter, the most widely used of which is the electrostatic precipitator , which can remove 99% particulate matter present in the exhaust from a thermal power plant. It has electrode wires that are maintained at several thousand volts, which produce corona and releases electrons. These electrons attach to dust particles giving them a net negative charge. The collecting plates attract the charged dust particles. The velocity of air between the plates must be low enough to allow the dust to fall
Scrubbers These are used to clean air for both dust and gases. Wet and dry two types of scrubbers are used for dust separation. A rubber gases like sulfur dioxide. In a scrubber, the exhaust is passed through a spray of water or lime. (2) control of gaseous pollutants- combustion, absorption and adsorption technique are used to control gaseous pollutants. Combustion- in the combustion process, oxidizable gaseous pollutants are completely burnt at a high temperature, petrochemical fertilizer, paints and varnish industries used combustion control of gaseous pollutants. (a)
(b) Absorption:- In this technique, gaseous pollutants are absorbed in suitable absorbent materials. (c) Adsorption:- this technique is applied to control toxic gases, vapors, and inflammable compounds that could not be efficiently removed or transferred by a fore said technique. Such air pollutants are adsorbed on large solid surface