Air Pollution - PDF

AIR POLLUTION 1.1Causes of pollution problem Pollution is the effect of undesirable changes in our surroundings that have harmful effects on plants, animals and human beings. Two basic problems result from the consumption of resources for our energy requirement Resource Crunch That results from irre...

AIR POLLUTION 1.1Causes of pollution problem Pollution is the effect of undesirable changes in our surroundings that have harmful effects on plants, animals and human beings. Two basic problems result from the consumption of resources for our energy requirement Resource Crunch That results from irreparable depletion of resources exceeding the carrying capacity of resources Environmental degradation That results from imbalances of our Ecosystem exceeding the assimilating ability of ecosystem thereby causing degradation in environment Environmental degradation causes various pollution problems Degradation in air environment causes air pollution problem. Degradation in noise environment causes noise pollution problem. Degradation in water environment causes water pollution problem. Dumping of solid waste in land causes land pollution problem. Pollution affects the flora and fauna in various ways causing ecological Pollution problem 1.2.Nature of pollutants In general, the pollutants can be classified depending on the degradation of them in the environment. a. Degradable pollutants: Easily degradable, easily decomposed to simpler compounds by means of biodegradation and physico-chemical degradation. Most of the wastes released by living beings are biodegradable. Most of the waste in our daily use are easily degradable. b. Difficultly degradable: These wastes are not easily degradable. They take a long time to degrade. Examples are plastic waste, chlorofluorocarbon, some pesticides etc. c. Non-degradable: These waste is not degradable to simpler compounds. Examples are metallic waste. Toxic heavy metals like lead, mercury, cadmium, chromium, nickel etc. will always remain the same metal and hence toxic 1 1.3 History of air pollution The origin of air pollutionon the earth can be traced from the timeswhen man started using firewood as a meansof cooking and heating. Hippocrates has mentionedair pollution in 400 BC. With thediscoveryand increasing use of coal, air pollutionbecame more pronounced especially in urbanareas. It was recognized as a problem 700 yearsago in London in the form of smoke pollution,which prompted King Edward I to make the firstantipollution law to restrict people from usingcoal for domestic heating in the year 1273. Inthe year 1300 another Act banning the use ofcoal was passed. Defying the law led to impositionof capital punishment. In spite of this airpollution became a serious problem in Londonduring the industrial revolution due to the useof coal in industries. The earliest recorded majordisaster was the ‘London Smog’ that occurredin 1952 that resulted in more than 4000 deathsdue to the accumulation of air pollutants overthe city for five days. Pollutants are also found indoors from infiltrationof polluted outside air and from variouschemicals used or produced inside buildings.Both indoor and outdoor air pollution are equally harmful. 1.4 Atmospheric useful gases and air pollutants Oxygen is required for human respiration (metabolic requirements). Oxygen is required for wild fauna in natural ecosystems and domestic animals used by man as food.Oxygen as a part of carbon dioxide, oxygen used for the photosynthetic activities of plants and prepares the first food of ecosystem. The atmosphere forms a protective shell over the earth. It is a complex dynamic system. If its nature is disrupted it affects all mankind. Most air pollutants have both global and regional effects. Living creatures cannot survive without air even for a span of a few minutes. To continue to support life, air must be kept clean. Major pollutants of air are created by industrial units that release various gases such as carbon dioxide, carbon monoxide and toxic fumes into the air. Air is also polluted by burning fossil fuels. The buildup of carbon dioxide which is known as greenhouse effect’ in the atmosphere is leading to current global warming. The growing number of scooters, motorcycles, cars, buses and trucks which run on fossil fuel (petrol and diesel) is a major cause of air pollution in cities and along highways. Air pollution leads to acute and chronic respiratory diseases such as various lung infections, asthma and even cancer. 1.5 Structure of the atmosphere 2 The atmosphere is normally composed of 79 percent nitrogen, 20 percent oxygen and one percent as a mixture of carbon dioxide, water vapour and trace amounts of several other gases such as neon, helium, methane, krypton, hydrogen and xenon. The general structure of the atmosphere has several important features that have relevance to environmental problems. The atmosphere is divided into several layers. The lowest layer, the troposphere,the only part warm enough for us to survive in, is only 12 kilometers thick. The stratosphere is 50 kilometers thick and contains a layer of sulphates which is important for the formation of rain. It also contains a layer of ozone, which absorbs ultra-violet light known to cause cancer and without which, no life could exist on earth. The atmosphere is not uniformly warmed by the sun. This leads to air flows and variations in climate, temperature and rainfall in different parts of the earth. 1.5.1 Comparison of troposphere and stratosphere Table 1.1: Comparison of troposphere and stratosphere Troposphere Stratosphere Close to earth surface, extends from surface Extends from 20 km up to 50 km to about 20 km above. 3 Maximum moisture content Moisture content less than I ppm All cloud formation and precipitation No cloud formation and precipitation All types of atmospheric pollution problem Only ozone layer depletion problem Ozone is a pollutant > 100 µg/m3 Ozone layer of more than 1000 ppm is maintained in stratosphere to prevent carcinogenic ultraviolet radiation reaching the atmosphere of earth. Lapse rate is negative that means the Lapse rate is positive that means temperature temperature decreases with altitude. increases with increase in altitude. Contains more than 75 % atmospheric mass Minimum atmospheric mass 1.6 Types of air pollutants Depending upon the occurrence, chemical nature and physical state etc. the air pollutants are classified into following category 1.6.1Natural air pollution and Anthropogenic air pollution The various air pollutants are occurring naturally. But their occurrence is few and far between so as to cause significant air pollution problem.  Lightening: Atmospheric nitrogen and oxygen can react at high temperature of lightening cause nitrogen oxide and nitrogen dioxide pollution  Forest fire: Fire remnants of forest have the air pollution in the form of particulates, unburnt hydrocarbon, carbon monoxide and some toxic pollutants  Forest fire: Fire remnants of forest have the air pollution in the form of particulates, unburnt hydrocarbon, carbon monoxide and some toxic pollutants  Volcanic eruptions: Molten lava have the sulfur converted to sulfur dioxide and can SO pollution 2 1.6.2 Anthropogenic air pollution Use of fossil fuel like coal, crude oil, petroleum products cause air pollution in the form of particulate pollution, SO , NO , CO, CO and other toxic pollutants 2 x 2 4  Vehicular pollution: particulate, CO and NO x Mineral excavation and beneficiation: particulate pollution Transportation: CO, CO2,SO , NOx, other hazardous pollutants 2 Loading and unloading: Particulate pollution 1.6.3Primary air pollution Pollutants that are emitted directly from identifiable sources are produced both by natural and anthropogenic events. Examples are CO,CO , SO ,NO,NO , Particulates classified as PM (Particle size.