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CHAPTER, , 18, , Pollution of Air and Water, , , , he presence of unusually high concentrations of harmful or poisonous substances in the, environment (air, water, ete.) is called pollution. Pollution conta, Poisonous substances and makes them impure to such an extent that they become 1, human beings, other animals, plants as well as to the non-living things. An unwanted and harmfil, substance that contaminates the environment (such as air and water) is called a pollutant. Inm, words, @ substance that lled a pollutant. The air and water v, levels harmful to humans, other annals, plants and non-living things are said to be polluted. Air and, , , , , , , , , , , , , , , , , , air is necessary for breathir, ter for more than a f, , , , water are both essential for our survival. For example, without air even for a few minutes. Similarly, we cannot |, (though we can live much longer without food)., , Air is a mixture of gases (which is present all around us). The two main Bases ria in air are, nitrogen and oxygen. Nitrogen makes up about 78 per cent of air where:, cent of air by volume. Air also contains small amounts of carbon dioxide, argon A and water vapour, ete., le, argon and wate i, , , , without, , , , , , , , The mixture of gases, ar. which is good for us. In addition to the normal constituents, the polluted air may also cant aenifil, substances such as carbon monoxide, sulphur dioxide, nitrogen oxides, smoke and dust, etc. \When air, is polluted, we are forced to breathe it to remain alive (though it is harmful to us). Mans, respiratory problems are caused by breathing in polluted air. In fact, the an o among, children are increasing day by dav due to increasing air pollution. Water is the most c \, Fresh water (usable water) is present in rivers, lakes and por, , , , around us, , , , , , , is present around u, also present under the ground. Due to increasing water pollution, water-borne disea, day by day. In this Chapter we will discuss how er get polluted; ¥, air and water pollution; and how air and water pollution can be controlled (or mi, , AIR POLLUTION, , h, , , , air and v, , , , , , ly contaminated with harmful gases like sulphur dioxide, nitrogen, , The air over large cities is heas, dust, etc. The contamination of air with harmful gases (like sulphur, , oxides, carbon monoxide, smoke an, , , , , , 340

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341, , ye, nitrogen oxides, carbon monoxide), smoke and dust, etc., is called air pollution. The poe, ioe “ esence in air makes it impure or contaminated is called an air pollutant. A substance becomes an ., , " pot lien it is present in air in such concentration which is high enough to have a harnful effect oo —, jolt wii things. The major pollutants which cause air pollution are : Sulphur dora os saiae, 5 Carbon monoxide, excess of Carbon dioxide, Chlorofluorocarbons, and Suspended partic, , (such as Dust, Smoke and Fly ash)., , rces of Air Pollution, aot sgt of the air pollution is caused by the burning of fuels such as wood, cow-dung cakes, coal,, N, , ne, petrol and diesel in homes, motor vehicles (automobiles), factories and thermal power plants,, kere yarious sources of air pollution are given below :, elt 7 smoke emitted from homes by the burning of fuels like wood,, , " cow-dung cakes, kerosene and coal causes air pollution., , ii) Exhaust gases emitted by motor vehicles (automobiles) due to, purning of petrol and diesel cause air pollution (see Figure 1)., Molor veltic les are the major cause of air pollution in big cities., , (iii) Smoke emitted by factories and thermal power plants due to, purning of coal causes air pollution, Oil refineries and industries engaged in the production of, , (i?) 7 : 7 :, metals and manufacture of chemicals cause air pollution., , a , _.) Stone crushers, cement factories, asbestos factories and lead ‘ <haust gases emitted by motor, , (v) Ste Figure J. Exhaust g t, processing units cause air pollution. vehicles cause air pollution. Motor, , itioni: shicle: Ct i rbon, , ,j) Use of chlorofluorocarbons in refrigeration, air conditioning vehicles produce pollutants like ca, , ‘ monoxide, carbon dioxide, sulphur, , dioxide, nitrogen oxides and smoke, etc., , (, , and acrosol sprays causes air pollution, (il) Smoking causes air pollution, All the above sources of air pollution are man-made sources of air pollution in which pollutants are, added to air by various human actis ities. Forest fires and volcanic eruptions are the two natural sources, of air pollution w hich put smoke and dust into the air., , Harmful Effects of Air Pollution, , Air pollution produces a large number of bad effects on living and non-living things. Air pollution can, cause health problems in human beings. It can kill animals and plants. It can also damage the environment, and property (buildings, etc.) We will now give the names, sources and harmful effects of various air, pollutants., : ()) SULPHUR DIOXIDE. Sulphur dioxide is produced by the burning of coal in factories and thermal, power plants. Sulphur dioxide is also produced by the burning of petrol and diesel in motor vehicles., Actually, the fuels such as coal, petrol and diesel contain some sulphur as impurity which burns to produce, sulphur dioxide gas. Oil refineries also emit sulphur dioxide gas into air. Sulphur dioxide gas in the, polluted air causes respiratory problems. If may even cause permanent lung damage. Sulphur dioxide, gas in polluted air produces acid rain. This acid rain damages trees, plants, soil, aquatic animals (like fish),, , statues, buildings and historical monuments. Sulphur dioxide also contributes to the formation of a deadly, , , , , , , , air pollutant called smog., , (ii) NITROGEN OXIDES. Nitrogen oxides are produced by the burning of fuels like petrol and, diesel in motor vehicles They are also produced by ihe burning of coal in factories and thermal power, Plants. Actually, the high temperature produced by the burning of fuels like petrol, diesel and coal makes, Some of the nitrogen and oxygen of air to combine to form nitrogen oxides. Oil refineries also produce and, at nitrogen oxides into the air. Nitrogen oxides attack breathing system and lead to lung congestion., , ney also attack skin. Just like sulphur dioxide, nitrogen oxides present in polluted air produce acid rain., ‘Togen oxides also contribute to the formation of smog., , , , , , - —e

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342, , f smoke and fog (The minute, , Smog is a deadly air pollutant which is formed by the combination 0, ther in winter, Is called fo)., , water particles suspended in air near the surface of earth during cold wea, Smoke contains tiny carbon particles, and harmful gases such as nitrogen oxides and sulphur dioxide, etc, , The carbon particles, nitrogen oxides and sulphur dioxide, etc., of smoke combine with the condensed, water vapour called fog to form ‘smog’. Smog causes cough and aggravates (makes worse) asthma and, other lung diseases, especially in children., , (iii) CARBON MONOXIDE. Carbon monoxide is produced by the i, like wood, coal, kerosene, petrol and diesel in homes, factories and moto:, motor vehicles (cars, buses and trucks, etc.) contain carbon monoxide whic!, combustion of fuels which produces carbon monoxide, takes place in insuf 2, smoke also contains carbon monoxide. Carbon monoxide is a very poisonous gas. When inhaled, carbon, monoxide combines with the haemoglobin of our blood and reduces the oxygen-carrying capacity of, blood. Due to this, blood is not able to carry sufficient oxygen to our body parts. This lack of onsen, causes respiratory problems (breathing problems). It causes suffocation. If too much carbon monoxide is, inhaled, it may even cause death. ., , (iv) CARBON DIOXIDE. Carbon dioxide is produced in excessive amounts by the burning of large, quantities of fuels such as wood, coal, kerosene, petrol, diesel, LPG, and CNG in homes, factories and, motor vehicles. Though carbon dioxide is a normal constituent of air but excess of carbon dioxide in air, is considered a pollutant (because it produces undesirable changes in the environment). Carbon dioxide, , is the main greenhouse gas which traps sun’s heat in the earth’s atmosphere by producing greenhouse, effect which leads to global warming. We will study this in detail after a while., , (v) CHLORO-FLUORO-CARBONS (CFCs). Chlorofluorocarbons are the chemical compounds made, of chlorine, fluorine and carbon elements. They are commonly known as CFCs. Chlorofluorocarbons are, used in refrigeration, air conditioning and aerosol sprays. So, all these sources release chlorofluorocarbons, into the air. Clilorofluorocarbons are industrially useful gases but they also behave as air pollutants because of their, damaging effect on ozone layer (which exists high up in the atmosphere or upper atmosphere)., Chlorofluorocarbons are depleting the useful ozone layer of the upper atmosphere. This happens as, follows : Chlorofluorocarbons released into the air go up and ultimately reach high into the atmosphere, where the protective ozone layer exists The chlorofluorocarbons react with the ozone gas of ozone layer, and destroy it gradually. Ozone layer prevents the harmful ultraviolet radiations of the sun from, reaching the earth. So, ozone layer protects us from the harmful effects of the ultraviolet radiations of the, sun. The destruction of ozone layer by CFCs will allow the extremely harmful ultraviolet radiations of, the sun to reach the earth. These ultraviolet radiations can cause skin cancer, cataract, and destruction, , of plants, including crops. In fact, a big hole has already been made by the destruction of ozone gas in the, ozone layer over the South Pole of the earth. It is called “ozone hole”. The good news is that less harmful, , ncomplete combustion of fuels, 1 vehicles. The exhaust gases of, h they emit into air (Incomplete, ficient supply of air). Cigarette, , chemicals are now being used in place of CFCs, , (vi) SUSPENDED PARTICULATE MATTER (SPM). The finely divided solid or liquid particles, suspended in air are called suspended particulate matter. Some of the examples of suspended particulate, matter are ; Dust, Smoke and Fly ash. They remain suspended in air for long periods., , (a) Dust consists of tiny particles of earth. Dust is produced by blowing wind, heavy traffic on roads,, stone crushers and construction activities. Dust in air spoils our clothes and reduces visibility Dust, produces allergic reactions in human body and aggravates diseases like bronchitis. Dust covers the, , , , leaves of plants and trees and prevents photosynthesis., , (b) Smoke is mainly tiny particles of carbon in air. Smoke is produced by the burning of fuels like, wood, cow-dung cakes, coal, kerosene, petrol, and diesel in homes, factories, thermal power plants and, motor vehicles. Smoke present in air spoils our clothes and blackens the buildings. Smoke attacks our, , lungs and causes respiratory diseases.

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yo, , phe, , 343, , minute ash particles formed by the burning of coal and carried into air by the gases, , (7 guring burning, Is called fly ash. Fly ash is emitted by the chimneys of coal based thermal, 0 ants Fly ash particles present in air cause irritation to the eyes, skin, nose, throat and, i ple, , yer ee tact. Continued breathing in air containing fly ash causes diseases like bronchitis and lung, i?, , , , , “th sid extremely harmful effects of air pollution on the environment are acid rain and greenhouse, , Jobal warming). So, we will now discuss acid rain and greenhouse effect produced by polluted, ject (0 1, one by one. Let us start with acid rain., , a otal, , . purning of fossil fuels like coal and oil in factories, thermal power plants and oil refineries, and, nd diesel in motor vehicles produce acidic gases like sulphur dioxide and nitrogen oxides which go, gt . and pollute it. Sulphur dioxide reacts with water vapour present in the atmosphere to form, oe jc acid whereas nitrogen oxides react with water vapour present in the atmosphere to form nitric, ttre acids dissolve in rainwater and fall to the earth in the form of acid rain. Thus, acid rain is that, eich contains small amounts of acids formed from acidic gases like sulphur dioxide and nitrogen, ait resent in polluted air. Acid rain contains very dilute solutions of sulphuric acid and nitric acid, oi alt causes great damage to living and non-living things. The damage caused by acid rain is very,, ar and hence cannot be seen immediately. Acid rain has the following harmful effects :, ‘0 Acid Rain Destroys Forests. Acid rain damages the forest trees by destroying their leaves [see, sre 2A) It causes the leaves of trees to turn yellow and fall off. In the absence of leaves, the roots of, ao absorb water from the soil. And due to lack of water the trees die. Acid rain also damages a, , of crop plants every year and causes a big loss to the farmers. Acid rain makes the soil acidic. This acidic, a not good for the growth of crop plants., sou, , it, , ve, , Seki, , , , , , (a) Forest tres led due to high acidity of, , , , e (c) A statue damaged, by acid rain lake water caused by acid rain by acid rain, , Figure 2. Harmful effects of acid rain., , (ii) Acid Rain Kills Aquatic Animals Such as Fish. Acid rain causes the water in ponds, lakes and, Mets to become much more acidic and unsuitable for the survival of aquatic animals and plants. Due to, nigh acidity of water, the aquatic animals such as fish get killed [see Figure 2(b)]., wien Rain Corrodes the Statues, Buildings and Historical Monuments and Damages Them, So ene buildings and monuments are made of marble or limestone, etc. The acids present in, , ‘act with the carbonates present in marble and limestone of a statue, building or monument and, , Ortode j . 5, , Wiens slowly (dissolve it slowly ). In this way, acid rain makes the statues, buildings and monuments, Tumb S ), __ & away slowly [see Figure 2(c)]., , , , cue of Taj Mahal. The Taj Mahal at Agra (near Delhi) is a beautiful historical monument made, ute marble (see Figure 3). The experts have warned that air pollution around Taj Mahal area is, Ng its white marble and also corroding it slowly. This poses a threat to the beauty of Taj Mahal., , ae, , , , d, “Scolouri

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344, , Actually, the Mathura Oil Refinery near Agra as well as, the various industries in and around Agra are emitting, gaseous pollutants such as sulphur dioxide and nitrogen, oxides into the air which cause acid rain. The acids present, in acid rain react with the marble (calcium carbonate) of Taj, Mahal monument and corrode it slowly. The slow corrosion, (or eating up) of marble of a monument by acid rain is also, known as ‘Marble Cancer’. [he suspended particulate matter, such as soot particles emitted in the smoke from Mathura Oil, Refinery is discolouring the pure white marble of Taj Mahal by, turning it yellowish. The Supreme Court of India has taken, several steps to save Taj Mahal from the damage being, caused by air pollution (acid rain, etc.). It has ordered all, the industries in Agra area to switch over to cleaner fuels, like CNG and LPG to reduce air pollution. It has also asked vehicles to be run, in the Taj Mahal area., , From the above discussion we conclude that it is not only the living things (such as humans, other land, animals, aquatic animals like fish, trees and crop plants, etc.) which are affected by air pollution, even the, non-living things (such as soil, statues, buildings and historical monuments) get affected by air pollution., , Before we go further and describe the greenhouse effect, we, should know the meaning of ‘greenhouse’ and how it works. This is, described below : The greenhouse is a structure or building made of, glass walls and glass roof in which the plants that need protection |, from cold weather are grown (see Figure 4). The glass walls and glass, roof of a greenhouse allow the sun’s heat rays to go in freely but do, not allow the inside heat (reflected by soil, plants and other things in iy, the greenhouse) to go out. In this way, more and more of sun’s heat |, rays are trapped inside the greenhouse due to which the temperature, in the greenhouse rises. So, even without an internal supply of heat,, the temperature inside a greenhouse becomes higher than that :, outside. This heat is beneficial for the growth of plants inside the figure 4. A, greenhouse (when the outside temperature is very low during winter roof of this greenhouse are made of g, season). Thus, greenhouse acts as a heat trap (which traps sun’s heat This house acts as a heat trap (tor, energy). We will now describe why a greenhouse acts as a heat trap., , The sun is an extremely hot object due to which the heat rays emitted by the sun are of shorter, wavelengths. The shorter wavelength heat rays coming from the sun can pass through the glass walls and, glass roof of a greenhouse and go inside it. On the other hand, the inside objects of glasshouse are much, less hot (than the sun), so they emit heat rays of longer wavelengths. The longer wavelength heat rays, emitted by the inside objects of the greenhouse cannot pass through the glass wails and glass roof of a, greenhouse and go out. Thus, glass is a material which allows sun’s heat rays to come in but does not allow, heat rays to go out. This is called greenhouse effect. Due to the presence of a carbon dioxide layer around, the earth, our atmosphere acts like the glass roof of an ordinary greenhouse and allows sun’s heat rays, to be trapped within the earth’s atmosphere. This is why itis called greenhouse etfect. Let us discuss it in, detail., , , , ‘ (a 2, 3, Taj Mahal monument is being affected by, , air pollution., , , , , Figure, , on CNG or unleaded petro], , , , , , lass, , , , GREENHOUSE EFFECT, Carbon dioxide gas present in the atmosphere allows the heat rays of the sun to pass through it and, reach the earth but prevents the heat rays reflected from the earth’s surface and its objects from passing out, of the atmosphere into space. In this way, the sun’s heat rays remain trapped in the earth’s atmosphere and