POLLUTION OF AIR AND WATERPOLLUTION OF AIR AND WATER

Paheli and Boojho were very excitedto hear the news that TajMahal in Agra is now one of the

seven wonders of the world. But theywere disappointed to hear that thebeauty of this monument in whitemarble is being threatened by airpollution in the area surrounding theTaj. They were eager to know ifsomething can be done to fight the airand water pollution.

We are all aware that ourenvironment is not what it used to be.Our elders talk about the blue sky, cleanwater and fresh air that was availablein their times. Now the media regularlyreports on the falling quality of theenvironment. We ourselves feel theimpact of the falling quality of air andwater in our lives. The number of peoplesuffering from diseases of the respiratorysystem, for example, is steadily rising.

We dread to imagine a time whenclean air and water may no longer beavailable! You have learnt about theimportance of air and water in yourprevious classes. In this chapter, we willstudy about the harmful changes takingplace in our surroundings and theireffects on our lives.

18.1 Air Pollution

We can survive for some time without food,but we cannot survive even for a fewminutes without air. This simple fact tellsus how important clean air is to us.

You already know that air consistsof a mixture of gases. By volume, about78% of this mixture is nitrogen andabout 21% is oxygen. Carbon dioxide,argon, methane, ozone and watervapour are also present in very smallquantities.

Activity 18.1

You may have covered your nosewhile passing a brick kiln emittingsmoke or started coughing whilewalking on a busy road (Fig. 18.1).On the basis of your experience,compare the quality of air at theplaces given below:

� A park and a busy road.� A residential area and an

industrial area.� A busy traffic intersection at

different times of the day e.g.early morning, afternoon andevening.

� A village and a town.

Fig. 18.1 : A congested road in a city

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Fig. 18.3 : Air pollution due to automobiles

One of your observations in theabove activity could be the differencesin the amount of smoke in theatmosphere. Do you know where thesmoke could have come from? Additionof such substances to the atmospheremodifies it. When air is contaminatedby unwanted substances which havea harmful effect on both the living andthe non-living, it is referred to as airpollution.

18.2 How does Air Get Polluted?

The substances which contaminate theair are called air pollutants. Sometimes,such substances may come from naturalsources like smoke and dust arising fromforest fires or volcanic eruptions.Pollutants are also added to theatmosphere by human activities. Thesources of air pollutants are factories(Fig. 18.2), power plants, automobileexhausts and burning of firewood anddung cakes.

Activity 18.2

You might have read in thenewspapers that respiratoryproblems amongst childrenare rising day by day. Conduct asurvey of households in yourneighbourhood and among friendsto find out how many children aresuffering from respiratory problems.

Many respiratory problems arecaused by air pollution. Let us now tryto find out the substances or pollutantswhich are present in the polluted air.

Have you noticed how rapidly thenumber of vehicles is increasing in ourcities?

Vehicles produce high levels ofpollutants like carbon monoxide, carbondioxide, nitrogen oxides and smoke (Fig.18.3). Carbon monoxide is producedfrom incomplete burning of fuels suchas petrol and diesel. It is a poisonousgas. It reduces the oxygen-carryingcapacity of the blood.

Fig. 18.2 : Smoke from a factory

Do you know?

If the vehicles registered in Delhi arelined up one after the other, the totallength would be nearly equal to thecombined lengths of the two longestrivers in the world, Nile and Amazon!

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Boojho remembers seeing a thickfog-like layer in the atmosphere,especially during winters. This is smogwhich is made up of smoke and fog.Smoke may contain oxides of nitrogenwhich combine with other air pollutantsand fog to form smog. The smog causesbreathing difficulties such as asthma,cough and wheezing in children.

Many industries are also responsiblefor causing air pollution. Petroleumrefineries are a major source of gaseouspollutants like sulphur dioxide andnitrogen dioxide. Sulphur dioxide isproduced by combustion of fuels likecoal in power plants. It can causerespiratory problems, includingpermanent lung damage. You havealready studied about the burning offossil fuels in Chapter 5.

Other kinds of pollutants arechlorofluorocarbons (CFCs) which areused in refrigerators, air conditionersand aerosol sprays. CFCs damage theozone layer of the atmosphere. Recallthat the ozone layer protects us fromharmful ultraviolet rays of the sun. Haveyou heard of the ozone hole? Try to findout about it. Thankfully, less harmfulchemicals are now being used in placeof CFCs.

In addition to the above mentionedgases, automobiles which burn dieseland petrol, also produce tiny particleswhich remain suspended in air for longperiods (Fig. 18.3). They reducevisibility. When inhaled, they causediseases. Such particles are alsoproduced during industrial processeslike steel making and mining. Powerplants give out tiny ash particles whichalso pollute the atmosphere.

Activity 18.3

Prepare a table using the pollutantsmentioned above. You may even addmore data to the following Table.

Table 18.1

Air Pollutants Sources Effects

18.3 Case Study : The TajMahal

Over the past 2 decades, India’s mostfamous tourist attraction, Taj Mahallocated in Agra (Fig. 18.4), has becomea matter of concern. Experts havewarned that pollutants in air arediscolouring its white marble. So, it isnot only living organisms that getaffected by polluted air but non-livingthings like buildings, monuments andstatues also get affected.

The industries located in and aroundAgra like rubber processing, automobile,chemicals and especially the Mathura oilrefinery, have been responsible forproducing pollutants like sulphurdioxide and nitrogen dioxide. Thesegases react with the water vapour presentin the atmosphere to form sulphuric acidand nitric acid. The acids drop down withrain, making the rain acidic. This iscalled acid rain. Acid rain corrodes themarble of the monument. Thephenomenon is also called “Marblecancer”. Suspended particulate matter,such as the soot particles emitted byMathura oil refinery, has contributedtowards yellowing of the marble.

The Supreme Court has takenseveral steps to save the Taj. It has

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and a part is reflected back into space.A part of the reflected radiation istrapped by the atmosphere. The trappedradiations further warm the earth. If youhave seen a greenhouse in a nursery orelsewhere, recall that the sun’s heat isallowed to get in but is not allowed togo out. The trapped heat warms thegreen house. The trapping of radiationsby the earth’s atmosphere is similar.That is why it is called the greenhouseeffect. Without this process, life wouldnot have been possible on the earth. Butnow it threatens life. CO2

is one of thegases responsible for this effect.

You know that CO2 is one of thecomponents of air. You have also studied

I am reminded of thechapter on crops. I

wonder whether acid rainaffects the soil and

plants also.

But how does CO2 contentrise in the atmosphere and

become excessive?

ordered the industries to switch tocleaner fuels like CNG (CompressedNatural Gas) and LPG (LiquefiedPetroleum Gas). Moreover, theautomobiles should switch over tounleaded petrol in the Taj zone.

Discuss with your elders and seewhat they have to say about thecondition of the Taj, 20 or 30 years ago!Try to procure a picture of the Taj Mahalfor your scrap book.

18.4 Greenhouse Effect

You know that the sun’s rays warm theearth’s surface. A part of the radiationthat falls on the earth is absorbed by it

Fig. 18.4 : Taj Mahal

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the role of carbon dioxide in plants. Butif there is excess of CO2 in the air, itacts as a pollutant.

Can you help Paheli find out theanswer to her question?

On the one hand, CO2 is continuouslybeing released because of humanactivities. On the other hand, area underforests is decreasing. Plants utilise CO2

from the atmosphere for photosynthesis,thereby decreasing the amount of CO2

in the air. Deforestation leads to anincrease in the amount of CO2 in the airbecause the number of trees whichconsume CO2 is reduced. Humanactivities, thus, contribute to theaccumulation of CO2 in the atmosphere.CO2 traps heat and does not allow it toescape into space. As a result, the averagetemperature of the earth’s atmosphereis gradually increasing. This is calledglobal warming.

Other gases like methane, nitrousoxide and water vapour also contribute

Global Warming

A Serious Threat!

Global warming can cause sea levelsto rise dramatically. In many places,coastal areas have already beenflooded. Global warming could resultin wide ranging effects on rainfallpatterns, agriculture, forests, plantsand animals. Majority of people livingin regions which are threatened byglobal warming are in Asia. A recentclimate change report gives us onlya limited time to keep the greenhousegases at the present level. Otherwise,the temperature may rise by morethan 2 degrees Celsius by the end ofthe century, a level considereddangerous.

towards this effect. Like CO2, they arealso called greenhouse gases.

Global warming has become a majorconcern for governments worldwide.Many countries have reached anagreement to reduce the emission ofgreenhouse gases. The Kyoto Protocolis one such agreement.

Boojho is surprised to hear that anincrease in the earth’s temperature byeven as little as 0.5 ºC can have such aserious effect! Paheli tells him that shehad read in the newspapers recently thatthe Gangotri glacier in the Himalayashas started melting because of globalwarming.

18.5 What can be Done?

What can we do to reduce airpollution?

There are many success stories in ourfight against air pollution. For example,a few years ago, Delhi was one of themost polluted cities in the world. It wasbeing choked by fumes released fromautomobiles running on diesel andpetrol. A decision was taken to switchto fuels like CNG (Fig. 18.5) and

Fig. 18.5 : A public transport bus powered by CNG

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unleaded petrol. These measures haveresulted in cleaner air for the city. Youmight know of some other examplesfrom your area regarding reduction ofair pollution. Share these with yourfriends.

fuels for our energy requirements. Thesecould be solar energy, hydropower andwind energy.

Activity 18.4You have various options ofcommuting to your school such aswalking, going by bicycle, travellingby bus or other public transport,using a car individually, travellingby car pool. Discuss in your classthe impact of each of these optionson the quality of air.

Small contributions on our part canmake a huge difference in the state ofthe environment. We can plant trees andnurture the ones already present in theneighbourhood. Do you know about VanMahotsav, when lakhs of trees areplanted in July every year (Fig. 18.6)?

Fig. 18.6 : Children planting saplings

Do you know about the “Say no tocrackers” campaign which wasorganised by children from manyschools? This made a big differenceto the air pollution levels aroundDiwali.

The quality of air at various locationsis monitored regularly by governmentand other agencies. We can use this datato generate awareness about airpollution among friends andneighbours.

There is a need to switch over toalternative fuels instead of the fossil

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Boojho and Paheli once happened togo to an area where some people wereburning dry leaves. They startedcoughing because the entire area was fullof smoke. Paheli thought it would be abetter option to put them in a compostpit rather than burning. What do youthink?

18.6 Water PollutionIn Class VII you learnt that water is aprecious resource. Think and list thevarious activities in which we needwater. We saw that water is becomingscarce due to increase in population,industries and agricultural activities.You have also studied how waterbecomes “dirty” after we use it forwashing clothes, bathing, etc. Thismeans that we are adding somematerials to the water, which spoil itsquality and change its smell and colour.

Whenever harmful substances suchas sewage, toxic chemicals, silt, etc., getmixed with water, the water becomespolluted. The substances that pollutewater are called water pollutants.

Activity 18.5

Try to collect samples of water froma tap, pond, river, well and lake.Pour each into separate glasscontainers. Compare these forsmell, acidity and colour. Completethe following Table.

Table 18.2

Smell Acidity Colour

Tap Water

Pond Water

River Water

Well Water

Lake Water

18.7 How does Water GetPolluted?

Case Study

Ganga is one of the most famous riversof India (Fig. 18.7). It sustains most ofthe northern, central and easternIndian population. Millions of peopledepend on it for their daily needs and

Fig. 18.7 : Course of the river Ganga

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livelihood. However, recently a study bythe World Wide Fund for Nature (WWF)found that Ganga is one of the ten mostendangered rivers in the world. Thepollution levels have been rising formany years. We have reached this stagebecause the towns and cities, throughwhich the river flows, throw largequantities of garbage, untreated sewage,dead bodies, and many other harmfulthings, directly into the river. In fact theriver is “dead” at many places wherethe pollution levels are so high thataquatic life cannot survive.

An ambitious plan to save the river,called the Ganga Action Plan waslaunched in 1985. It aimed to reducethe pollution levels in the river. However,the increasing population andindustrialisation have already damagedthis mighty river beyond repair.

Let us take a specific example tounderstand the situation. The Gangaat Kanpur in Uttar Pradesh (U.P.), hasone of the most polluted stretches ofthe river (Fig. 18.8). Kanpur is one ofthe most populated towns in U.P. Peoplecan be seen bathing, washing clothes

and defecating in the river. They alsothrow garbage, flowers, idols of godsand goddesses and non-biodegradablepolythene bags into the river.

At Kanpur the amount of water iscomparatively small and the flow of theriver is very slow. In addition, Kanpurhas more than 5000 industries. Theseinclude fertiliser, detergent, leather andpaint industries. These industrial unitsdischarge toxic chemical wastes into theriver.

Based on the above informationthink of the answers to the followingquestions :

� What are the factors responsible forpollution of the river ?

� What steps can be taken to restorethe river Ganga to its past glory ?

� How would the disposal of garbage,etc., affect the living organisms in theriver ?

Many industries discharge harmfulchemicals into rivers and streams,causing the pollution of water(Fig. 18.9). Examples are oil refineries,paper factories, textile and sugar mills

Fig. 18.9 : Industrial waste discharged into ariver

Fig. 18.8 : A polluted stretch of the riverGanga

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and chemical factories. These industriescause chemical contamination of water.The chemicals released include arsenic,lead and fluorides which lead to toxicityin plants and animals. There areregulations to prevent this. Industriesare supposed to treat the wasteproduced before discharging it intowaters, but quite often the rules are notfollowed. The soil is also affected byimpure water, causing changes inacidity, growth of worms, etc.

We have learnt in Chapter 1 theimportance of pesticides and weedicidesfor the protection of crops. However, allthese chemicals dissolve in water andare washed into water bodies from thefields. They also seep into the groundto pollute ground water.

Have you seen ponds which lookgreen from a distance because they havea lot of algae growing in them? This iscaused by excessive quantities ofchemicals which get washed from thefields. These act as nutrients for algaeto flourish. Once these algae die, theyserve as food for decomposers likebacteria. A lot of oxygen in the waterbody gets used up. This results in adecrease in the oxygen level which maykill aquatic organisms.

Recall Activity 18.6

You had investigated the sewagedisposal system of your locality inClass VII.

Do you remember how thesewage was collected from yourhome and where it went thereafter.

Sometimes untreated sewage isthrown directly into rivers. It contains

food wastes, detergents, microor -ganisms, etc. Can ground water getpolluted by sewage? How? Watercontaminated with sewage may containbacteria, viruses, fungi and parasiteswhich cause diseases like cholera,typhoid and jaundice.

The bacteria present in the faecesof mammals are indicators of thequality of water. If water has thesebacteria, it means that it has beencontaminated by fecal matter. If suchwater is used by us, it can cause variousinfections.

Do you know?

Hot water can also be a pollutant !This is usually water from powerplants and industries. It is releasedinto the rivers. It raises thetemperature of the waterbody,adversely affecting the animals andplants living in it.

18.8 What is Potable Waterand How is WaterPurified ?

Activity 18.7

Let us construct a water filter withsimple, everyday materials.

Take a plastic bottle and cut itinto 2 halves at the centre. Use theupper half as a funnel by putting itupside down in the lower half. Makelayers in it with paper napkin or afine cloth followed by, cotton, sandand then gravel. Now pour dirtywater through the filter and observethe filtered water.

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Discuss the following questionsamongst yourselves and with yourteacher:� Why do we need to filter water

before drinking ?� Where do you get your drinking

water from?� What will happen if we drink

polluted water?

Boojho is very upset. He tells Pahelithat he drank water which looked clearand was without any smell, but still hefell sick !

Paheli explains that water whichlooks clean may still have disease-carrying microorganisms and dissolvedimpurities. So, it is essential to purifywater before drinking, for example, byboiling.

Water which is suitable for drinkingis called potable water. You have seenhow various physical and chemicalprocesses in the sewage treatmentplants help to clean water beforedischarging it into water bodies.Similarly, municipal bodies treat thewater before supplying it to households.

water. Boiling kills the germs presentin the water.

� Chlorination is a commonly usedchemical method for purifying water.It is done by adding chlorine tabletsor bleaching powder to the water. Wemust be cautious. We should notuse more chlorine tablets thanspecified.

18.9 What can be Done?

Activity 18.8

Investigate the level of awarenessabout water pollution in your area.Collect data on the sources ofdrinking water and the methods ofsewage disposal.What are the common water-bornediseases in the community? You canconsult your local doctor/healthworker for this.Which are the governmental andnon-governmental organisationsworking in this field? What are themeasures being taken by them forgenerating awareness?

Laws for industrial units should bestrictly implemented so that pollutedwater is not disposed off directly intorivers and lakes. Water treatment plantsshould be installed in all industrialareas (Fig. 18.10). At our individuallevels we should consciously save waterand not waste it. Reduce, reuse andrecycle should be our mantra !

Think of your daily routine – Howcan you save water?

We can think of creative ideas likereusing water used for washing and forother household tasks. For example,

Do you know?

25% of the world’s population iswithout safe drinking water !

Let us see how water can be madesafe for drinking:� You have already seen how water is

filtered. This is a physical method ofremoving impurities. A popularhousehold filter is a candle typefilter.

� Many households use boiling as amethod for obtaining safe drinking

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water used for washing vegetables maybe used to water plants in the garden.

Pollution is no longer a distantphenomenon. It is affecting the quality

of our daily lives. Unless we all realiseour responsibility and start usingenvironment-friendly processes, the verysurvival of our planet is in danger.

Fig. 18.10 : Water treatment plant

Do you know?

While brushing your teeth, leaving the tap running may waste several litres ofwater. A tap that drips once every second wastes a few thousand litres of waterevery year. Think about it !

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KEYWORDS

ACID RAIN

AIR POLLUTION

CHEMICAL

CONTAMINATION

GLOBAL WARMING

GREENHOUSE

EFFECT

POLLUTANTS

POTABLE WATER

WATER POLLUTION

WHAT YOU HAVE LEARNT

� Air pollution is the contamination of air by

impurities which may have a harmful impact

on the living organisms and the non-living

components.

� Pollutants are the substances which

contaminate air and water.

� Carbon monoxide, nitrogen oxides, carbon

dioxide, methane and sulphur dioxide are the

major pollutants of air.

� Increasing levels of greenhouse gases like CO2

are leading to global warming.

� Water pollution is the contamination of water

by substances harmful to life.

� Sewage, agricultural chemicals and industrial

waste are some of the major contaminants of

water.

� Water which is purified and fit for drinking is

known as potable water.

� Water is a precious natural resource. We must

learn to conserve it.

Exercises

1. What are the different ways in which water gets contaminated ?

2. At an individual level, how can you help reduce air pollution?

3. Clear, transparent water is always fit for drinking. Comment.

4. You are a member of the municipal body of your town.

Make a list of measures that would help your town to ensure the supplyof clean water to all its residents.

5. Explain the differences between pure air and polluted air.

6. Explain circumstances leading to acid rain. How does acid rain affect us?

7. Which of the following is not a greenhouse gas?

(a) Carbon dioxide

(b) Sulphur dioxide

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(c) Methane

(d Nitrogen

8. Describe the ‘Green House Effect’ in your own words.

9. Prepare a brief speech on global warming that you have to make in yourclass.

10. Describe the threat to the beauty of the Taj Mahal.

11. Why does the increased level of nutrients in the water affect the survivalof aquatic organisms?

E X

E R

C I

S E

S

Extended Learning — Activities and Projects

1. In some cities, a pollution check has been made compulsory forvehicles. Visit a petrol pump in order to learn about the process ofconducting a pollution check. You may systematically record yourfindings in the following areas:

� Average number of vehicles checked per month.

� Time taken to check each vehicle.

� Pollutants checked for.

� The process of testing.

� Permissible levels of emission of various gases.

� Measures taken if the emitted gases are above the permissiblelimits.

� How frequently is a pollution check required ?

2. Conduct a survey in your school to investigate various environmentrelated activities that have been undertaken. The class can divideitself into two groups, with each group looking at a different area.For example, one group can find out whether there is anenvironment club in the school. What are its objectives ? What isits calendar of events ? How can you become a member ?

If your school does not have such a club, you can even think ofstarting one along with a few of your friends.

3. Organise a field visit to a river in or around your town with the helpof your teachers.

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Observations followed by discussion could focus on :

� The history of the river.

� Cultural traditions.

� Role of the river in meeting the town’s water needs.

� Pollution concerns.

� Sources of pollution.

� Effects of pollution on the people living by the riverside as wellas those living far away.

4. Find out with the help of your teachers and the internet (if possible),whether there are any international agreements to control globalwarming. Which are the gases covered under these agreements?

� www.edugreen.teri.res.in/explore/air/air.htm

� www.edugreen.teri.res.in/explore/water/pollu.htm

� www.cpcb.nic.in/citizen’s%Charter/default_citizen’s.html

� coe.mse.ac.in/kidswater.asp

� coe.mse.ac.in/kidsair.asp