ptuas.loremate.com environmental science 5

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http://ptuas.loremate.com/evs/node/6 March 7, 2012

Environmental Science

Q. 1. What are causes of soil pollution?

Ans. Soil Pollution. It is resulted due to human activities, such as dumping of wastes, use of

agrochemicals, mining operations and, urbanization. Alteration in soil by addition and removal of materials leading to reduced productivity is called soil pollution. Here, soil productivity includes boththe quantity and the quality of the produce.

Causes of Soil pollution.

Types of Soil Pollutants /Sources of Soil Pollution. Many materials adversely affect the physical,chemical and biological properties of the soil and reduce its productivity. These include (1)Municipal wastes (2) industrial wastes (3) pesticides, (4) fertilizers and organic manure (5) radio-active wastes, (6) discarded materials and mining operation.

Q. 2. Differentiate marine pollution and water pollution.Ans. Water pollution. Addition of harmful materials to water is termed as water pollution. Thesources of inland water pollution are community waste water (sewage) and water from industries -and agricultural practices. Water pollutants include organic matter, pathogens, chemicals andminerals, solid particles, radioactive wastes and heat. Marine pollution. This type of pollution iscommon in sea water. The pollution of sea water is due to following reasons

(i) Due to spilling of oil from naval transport.

(ii) Accidents of oil transporting naval transports.

(iii) During loading and unloading of oil in naval transports.

(iv) Leakage of oil from the oil wells located nearby sea shore.

Q. 3. What are problems associated with e-wastes?

Ans. Problems associated with e-wastes

Irreparable computers and electronic goods are known as electronic wastes or e-wastes. Most of them are shipped to developing countries for metals like copper, nickel, silicon, gold are recoveredby recycling. Recycling the environmental friendly technologies are the methods for treatment of defunct ships and e-wastes. International treaty called Basel Convention drafted in Basel(Switzerland) was result of great demand from developing countries.

Q. 4. What is particulate matter? Give prime sources of particulate matter.

Ans. Suspended Particulate Matter (5PM). The solid particles or liquid droplets (aerosols) remainsuspended in air. For example smoke, soot dust, asbestos etc. SPM above the size of 10 mm istrapped by nasal hair, pharyngeal, tracheal and bronchial mucus. The same are coughed out or deposited in nose as nasal scales. Smaller particles of SPM reach the alveoli. There they may beattacked by phagocytes or pass into living cells. SPM causes irritation in respiratory tract, bronchitisand lung diseases. These particles may cause asbestosis, pneumoconiosis. They also result inreduced visibility.

Q. 5. What is equitable use of resources?

Ans. The countries of north are more developed whereas the countries of south are less developed.
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The developed countries have only 22% of worlds population but they use 88% of its naturalresources, 73% of its energy and command 85% of its income. Whereas the less developedcountries have 78% of worlds population and use about 12% of natural resources and 27% of energy. Problems of unemployment, poverty and hunger in less developed countries can only betackled through development. Solution to this problem is to have more equable distribution of resources and wealth. A global consensus has to be reached for balanced distribution of basicresources like safe drinking water, food, fuel, etc. So that the poor in the less developed countriesare at least able to sustain their life.

Q. 6. What is smog and why is it caused?

Ans. Smog (Des Voeux, 1905). Smog is opaque or dark fog having condensed water vapours,dust, smoke and gases (SO2, H2S, NO2 etc.). It causes silvering! glazing and necrosis in plants,allergies and asthma/bronchitis in humans. Some famous smogs of the world are Los Angelessmog (1946), London smog (1952), Tokyo, Rome, New York, Sydney (1970). Smog is of two types:

(i) Classical (London) Smog. It occurs at low temperature, contains sulphur gases (hydrogensuiphide, sulphur dioxide), smoke and dust particles.

(ii) Photochemical Smog. It is secondary pollutant. It is yellowish brown smog which is formed under oxidising conditions and high temperature over cities and towns that are releasing a lot of nitrogenoxides and unburnt hydrocarbons. In still air the two interact photochemically to producephotochemical oxidants-ozofle, PAN, aldehydes and phenols. Photo-chemical smog does not have,any appreciable amount of primary pollutants. It is also called Los Angeles smog.

Effect on biological world. It causes bleaching of foliage of certain plants. It also

causes silvering, glazing and necrosis of the leaves.

Q. 7. Describe the three measures of water quality.

Ans. Water pollution means the introduction into natural water of anything that

is foreign to them. It is undesirable change in physical, chemical or biological characteristics of water that may harmfully affect the human life, our industrial processes, living organisms.

Three measures of water quality

1. Prevent run-off manure, agrochemicals, like fertilizers and pesticides. Divert such run-off to basinfor settlement. The nutrient rich water can be used as

fertilizer in the fields.

2. Developing of sewage treatment plants and industrial effluent Treatment system so that all typesof pollutants can be removed from it and pure water may be

made available for recirculation.

3. Bathing, washing etc. should be prohibited in the vicinity of sources and public awarenessregarding water pollution should be treated.

Q. 8. What is thermal pollution?

Ans. Thermal Pollution. Hot effluents and hot water (e.g., thermal plants/atomic reactors) bringabout rise in water temperature. Warm water contains less oxygen, has lower rate of putrescibilityresulting in increased organic loading, replacement of green algae by blue-green ones. Manyanimals fail to reproduce e.g., Trout, Salmon. El Nino is warm ocean or Peru current that recurs after 58 years. It kills marine animals and planktons over large tracts along Peru and Ecudor coasts.


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Q. 9. Differentiate primary air pollutants and secondary air pollutants.

Ans. Differences between primary air pollutants and secondary air pollutants

Q. 10. Whatdoes

Environmental (protection) Act 1986 of India mean ? List the major categories of pollutant.

Ans. In environmental (protection) Act, 1986 of India environmental pollutant means any solid,liquid or gaseous substance present in such concentration as may be or tend to be injurious toenvironment and environmental pollution means the presence in the environment of anyenvironmental pollutant. There are two basic types of pollutants:

Pollutant Categories

Pollutants may be categorised in several ways. Some major categories of pollutants are

(i) Organic pollutants. Such as DDT, polychiorinated biphenyls (PCBs), oil.

(ii) Inorganic pollutants. Such as nitrates, acids found in acid rain, metals.

(iii) Acid pollutants. Found in run off from coal mining, Cl formed by a reaction of HC1 gas withmoisture.

(iv) Radiological pollutants. Which are radioactive chemicals found naturally in rocks, soil and water.

(v) Biological pollutants. Are pathogenic micro-organisms such as infectious bacteria, viruses andProtozoa.

(vi) Multiple pollutants. These are many pollutants that affect the organism at one time e.g.,xenobiotics (foreign chemicals.)

(vii) Physical pollutants. Which may have both inorganic and organic component e.g., soil carried inrain water run off from agricultural fields.

Q. 11. What is air pollution? List various air pollutants and their sources.

Ans. Air pollution. Release of harmful materials into the air is called air or atmospheric pollution. It isthe degradation of air quality and atmosphere condition. Air pollutants include gaseous materials,suspended particles and radioactive substances.

(a) The gaseous pollutants of air come from combustion in motor vehicles and industries. Theseinclude CO, GO2, NO, NO2, SO2, so3, hydrocarbons1 fluorides and photochemical oxidants, suchas peroxyacyl nitrate (PAN), ozone (03), and aldehydes. PAN is formed in the air by interactionbetween nitrogen oxides and hydrocarbons in the presence of sunlight. It is more toxic than theprimary pollutants. Increase in toxicity by reaction among pollutants is called synergism.

(b) The particulate contaminants of air also come from industries and automobiles. These include flyash, soot, metal dust, cotton fibres, asbestos, fibres, lead, aerosols (chloroflUorOCarb015 or CFCs), polychiorinated biphenyls (PCBs), tobacco smoke, smog, pollen, spores, cysts andbacteria.


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(c) Radioactive substances are released by nuclear explosions and war explosives.

Main sources of air pollution

1. Fixed sources. Which include large factories, electrical power plants, mineral smelters, smallindustries.

2. Mobile sources. They include all sorts of transports.

Atmospheric pollutants and their sources

Air pollution

Short Answer TypeQuestions

Q. 1. (a) Whatis acid rain?

(b) What areadverseeffects of acidrain?

Ans. (a) Acidrains. Sulphur

dioxide andsulphur trioxideare producedby oxidation of sulphur in thefossil fuels.These gasesreact with water and form sulphuric acid or sulphurOus acid. These acids when precipitatedas rain or snOw create acid rain or acidprecipitation. The pH of acid rains is less than 5-6and could be as low as 4.

(b) Effects of acid rains.

1. Acid rain adversely affect plant vegetation bycausing chlorosis, necrosis, defoliation and dieback.

2. It causes leaching of essential minerals of soil. Toxic minerals left in the soil further kill the plants.50% of natural forests have been destroyed by acid rain in Germany, Sweden, north east U.S.A.,Romania, Poland, etc.

3. Acid rain has also ruined fresh water reservoirs of most industrialised countries, e.g. 80% inNorway, 25% in Sweden, 20% in U.S.A.

4. Acidity dissolves toxic metals like Hg, Pb, Zn, Al. Both acidity and toxic metals kill all types of


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aquatic life except some algae and fungi.

5. Acid rain corrodes metals, marble, painted surfaces, slate, stone, etc. The phenomenon is calledstone leprosy.

Q. 2. Explain different stages of solid waste management.

Ans. Solid Waste. Because of various human activities, millions of tonnes of waste is producedevery day all over the world. Waste is produced in the households, offices, factories, industries, etc.Household wastes include newspapers, bottles, cans, broken crockery, broken glass, plasticcontainers, ash, polythene bags, dust or domestic garbage. The discarded solid material after useis called Garbage, Refuse, Rubbish or Solid waste

The constituents of solid wastes are similar all over the world but the proportion varies widely fromcountry to country and city to city. Nevertheless, more waste is generated in urban areas ascompared to rural areas.

Management of Solid Waste

Solid waste management involves activities including collection, transfer and transport to suitablesites, and safe disposal of wastes by methods which are environmentally compatible.

Collection of Waste. In poor countries like India, collection methods are poor or even absent. Mostof the waste remain near the place of source. Domestic garbage is generally thrown in streets or dumped on any available land. The heaps of garbage produce foul smell and are usually spread bystray cattle, pigs, rodents and rag pickers who search some reusable items. The clearance bymunicipalities is usually irregular.

Proper planning demands the provision of collection bins in streets and along roads which must becleared at least once or twice a day. In developed countries, there are automatic machines for collection of waste.

Transfer and Transport of waste. It is the second step of waste management which needs a fleet of transporl vehicles for the transfer of heaps of garbage from street corners or municipal dustbins todisposal sites or places of processing. India cities have only few vehicles (2-5 in city of 10 lakhpopulation) as compared to the amount of waste.

Disposal of Solid Wastes

1. Municipal solid wastes are burnt to reduce the volume.

2. Sanitary landfills have been adopted as an alternative to open-burning dumps.

3. Municipal wastes are incinerated and the heat-emitted is used to generate electricity.

4. They are also recycled for various components.

5. Fly ash is used in construction industry or buried as landfills; it is also used for soil amendment asin increases water retention and aeration of soil.

6. e-wastes are buried as landfills or incinerated ; they are also recycled.

Q. 3. Taj Mahal is reported to be threatened by Mathura Refinery. Discuss the possible

threats that the refinery poses.

Ans. The acid depositions react with lime stone, marble and other materials to cause deteriorationand disfigure the building material. A good example is Taj Mahal in danger of being destroyed bythe components of polluted atmosphere due to pollutant released from the nearby Mathura Refinery.


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The Refinery is using low sulphur fuels, emits about 25-30 Tornies of SO2 daily. The emittedSO2 results in acidic precipitation - (both dry and wet) under condensation a flow of wind combinedwith humidity, in the surrounding area. The acid deposition reacts with calcium carbonate (CaCO3)in the marble to form calcium sulphate (CaSO4) which causes deterioration. Some of the visiblesigns of deterioration of the Taj Mahal are as follows

1. Discoloration of the grey or brown rust like stains, especially in the niches and

arches.2. Chipping and breaking of the edges of the marble slabs.

3. Formation/appearance of cracks in marbles.

4. It can also lead to reduction in brightness contrast between objects.

Q. 5. Write a note onsecondary air pollutant.

Ans. Secondary air pollutants. The primaryair pollutants (gases,particulates) take part ina wide range of photochemicalreactions, formingsecondary pollutants.Such new products oftencause greater damage

than is caused directlyby the primary pollutants.

The main products thatresult from light strikingthe hydrocarbons fromexhaust are the olefins(also known as alkenes),ethylenes or unsaturatedhydrocarbons, carboncompounds containing

double bonds, thealdehydes and thearomatics. The aromaticcompounds createdphotochemically appear to be among the mostserious of all air pollutants. One of thesecompounds benzpyrene,has been proved toinduce cancer. Two

other photochemicalpollutants that appear tocause serious problemsare peroxybenzoylnitrate and peroxyacetyl


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nitrate (PAN).

Important examples of secondary pollutants are :

The smog is aharmful mixture of smoke plus fog.The word was first

used in 1905 todescribe thecombination of smoke and fog thatwas observed in London and totally obscured visibility for a few hours. This smog resulted fromSO2, soot and tarry materials released into the atmosphere by burning of high-sulphur coal.

The photochemical smog results from the reaction of nitrogen oxides and volatile organic chemicalsin summer sunlight to form ozone. In addition to ozone it contains other photochemical oxidants,including peroxyacetyl nitrate (PAN) and NO2. It also contains the particulates.

Some other secondary pollutants are : -(a) NO: It is formed by dissociation of NO2 to atomic oxygen and NO.

(b) NO2: It is formed in sunlight from NO (NO + O NO2)

(c) Hydroxyl radical (OH) : It is formed in sunlight from hydrocarbons and nitrogen oxides. It reactswith other gases to form acid droplets.

(d) Nitrous acid (HONO) : It is formed from NO2 and water vapours.

(e) Nitric acid (HNO3) : It is formed from NO2 and is a major component of acid rain.

Q. 6. Write the effects of hydrocarbons (HCs), SO2 and NO2.

Ans. Effects of hydrocarbons : 1. Benzene and its derivatives are carcinogens.

2. Formaldehyde causes indoor pollution.

3. Some reactive HCs contribute to formation of secondary pollutants.

Effect of SO2

SO2 is released into atmosphere from various factories which use ores of Cu, Zn,

Pb, Ni and Fe. The sulphur present in these ores is oxidised and SO2 is given out. Besides thisvehicle exhaust, burning of coal and oil refineries also give out SO2.

SO2 have harmful effects on man and plants. High concentration of SO2 destroys chlorophyll inplants (Chiorosis disease), lysis of the cell occurs, parts of the plant are destroyed and it may resultin the death of the whole plant (Necrosis). Even if death does not occur, it results in prevention of growth and productions plasmolysis and various metabolic diseases.

Effects of Oxides of nitrogen

Nitrogen monoxidc lowers the oxygen-carrying capacity of the blood. Hence NO2 irritates the eyes,nose, bronchial tubes and lungs. Its high concentration proves fatal. Being a strong reducing agent,NO2 attacks metals, textiles and other materials. Nitrogen oxides damage plants also.

Q. 7. Write a note on the air pollution caused due to combustion.


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Ans. The mobile combustion sources are the main sources of air pollution especially in the cities.They include the locomotives, automobiles and aircrafts.

The air pollutants from these are

1. (i) Carbon monoxide (ii) oxides of nitrogen and (iii) a mixture of hydrocarbons.

2. If the petroleum used as fuel in these sources contains lead as an impurity in the form of tetraethyllead Pb(C2H5)4 and tetramethyl lead Pb(CH3)4 the gaseous discharge mentioned above containsparticulate lead compounds.

Even if not inhaled, lead is absorbed by the body and causes serious damage to the tissues. It alsohampers the haemoglobin formation.

3. Smog. In the presence of sunlight, various unburnt hydrocarbons produced from the automobilecombustion react with oxides of nitrogen to form ozone,

peroxyacyl nitrates and aldehydes. They are called photochemical oxidants. Together with smokeand fog they constitute smog which has a harmful effect on mans respiratory and nervous system; italso harms the plants and rubber

goods.

4. Aerosols. Aerosols are certain chemicals released in the air with force in the form of mist or vapour. The important source of aerosols is the jet aeroplane

emissions in the outer atmosphere. The aerosols contain fluorocarbons which deplete the ozonelayer in atmosphere.

Q. 8. What is water pollution? List various water pollutants.

Ans. Water pollution

Addition of harmful materials to water is termed water pollution. The sources of inland water pollution are community waste water (sewage) and wastes from industries and agriculturalpractices.

Water pollutants include organic matter, pathogens, chemical and minerals, solid

particles, radioactive wastes and heat.

(i) Organic matter reaches water in sewage and effluents of certain industries.

Decomposers breakdown organic matter, using up the oxygen of water. This kills the animals. Anaerobic bacteria then produce foul-smelling gases.

(ii) Pathogens are also brought by sewage. They include bacteria, protozoans and

helminth eggs. They cause diseases if taken up with polluted water.

(iii) Chemicals and minerals reaching water include fertilizers and pesticides in farm run-off,detergents in bathroom water, and toxic materials (arsenic,

cadmium, lead, zinc, copper, mercury and cyanides) in effluents of some

industries.

(iv) Detergents and Fertilizers. The term detergent is applied to washing materials.


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Detergents are composed of complex phosphates, which eventually break down

into phosphates usable by aquatic plants. The use of detergents has been

responsible for increase in the phosphorus in sewage effluents.

Although detergent are not highly toxic to fishes, they do damage to gills and

remove protective mucous from gills, skin and intestine. Aquatic invertebrates and cray fish mayalso be affected by detergents.

(v) Toxic metals. Wastes containing different concentration of heavy metals, either individually or incombination, may be toxic to aquatic organisms. For example, Cd is toxic to many organisms after their exposure to low concentration toxicity of chromium to insects and other aquatic formsalso varies. Copper is relatively quite acutely toxic to fishand its toxic effect also dependson the hardness of water. Toxic metals responsible for air pollution (e.g., lead, nickel, Cd)may also reach water and harm the aquatic organisms. Lead poisoning of children hasbeen reported from many countries. Adult may also suffer adverse effects includingdamage to kidney and nervous system and high blood pressure other serious adverse effects areinfertility and anaemia.

Mercury is also an important toxic pollutant. The Hg (mercury) of waste products is converted byanaerobic bacteria into CH3Hg (methyl mercury) and (CH3)2Hg, (dimethyl mercury), which arepoisonous molecules. The effects of mercury poisoning include thermosomal damage and toxiceffects on liver, kidney and gills of fishes.

(vi) Solid particles of clay and metal dust settle in water from the air. They reduce light needed for photosynthesis and this may disturb food chains and result in loss of water life.

(vii) Radioactive dust from mining and processing of uranium enters water.

(viii) Thermal pollution of water is caused by the discharge of hot water from power plants and other industries.

Q. 9. What are the effects of water pollution?

Ans. Effects of Water Pollution

1. Water pollutants reach the sea directly from the coastal cities and ships, and

indirectly with river water from distant places. Oil spilled in tanker accidents is a major

threat to ocean life.

2. Pollutants impart colour, turbidity, unpleasant smell and taste, and foaminess

to water, making it unfit for use. They are detrimental to aquatic plants and animals.

Some of them are highly toxic and kill the aquatic organisms. Many infectious diseases

spread through contaminated water.

Diseases caused by polluted water.

1. Bacterial diseases. Cholera, Typhoid, Diarrhoea, Dysentery.

2.. Viral diseases. Jaundice, Polio etc.


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3. Protozoanal diseases. Diseases associatd with stomach and intestines e.g.

Amoebic dysentery, Giardiasis etc.

4. Helminthic diseases. Infection of some intestinal parasites like Ascaris lumbricoides

is through drinking water only. Guinea worm diseases is through Cyclops present in

the drinking water. Through contaminated water they reach to another host i.e. man.

5. Some Elements and their Toxicity

6. Water ways becomebiologicallybarren.

Aquaticorganismscan toleratepoisons andother pollutants onlyin low

concentrations. Excesses may prove lethal. Different (a) Eutrophication (b) Biological magnification

organisms have different levels of tolerance or sensitivity to various effluents or poisons and toxicityof most poisons is also affected by environmental factors such as temperatures pH, oxygen content,calcium contets etc. Water ways polluted with zinc and

often become biologically barren.

Q. 10. Write critical notes on(a) Eutophication.

(b) Biological magnification

(c) Ground water depletion and ways for its replenishment.

Ans. (a) Eutophication. The process by which a body of water becomes barren either by naturalmeans or by pollution extensively rich in dissolved nutrients. It results in the increased primaryproductivity that often leads to seasonal deficiency in dissolved oxygen.

Phosphorus and nitrates dissolved in water acts as nutrients and accelerates the growth of algaethat may form a mat on the water surface. The algae use oxygen at night and may deoxygenate thewater enough to kill the fish and other animals. The algal mat at the water surface may block light tothe submerged plants. The algae may die and sink, and feed the oxygen consuming bacteria. Theymay be pushed on to the shore by wind and decompose, releasing foul gases such as hydrogen


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sulphide. Silt and decaying matter may accumulate and finally fill the lake or pond. This process iscalled senescence. It is a natural stage in the change of a lake into dry land and it becomes barren.

Biological magnification of DDT in an aquatic food chain.

(b) Biological magnification. The phenomenon in which the harmfulpollutants (such as pesticides) enter the food chain and getconcentrated more and more at each successive trophic level of organism is called biological magnification.

This phenomenon is well known for mercury and DDT. Figure on theside shows biomagnification of DDT in an aquatic food chain.Zooplankton (tiny floating animals) in the food chain, accumulatedmodest levels of DDT. However, small fish, forming the next level of the food chain, must eat zooplankton several times their own weightand thus they accumulated more of DDT. In this manner, theconcentration of DDT magnified at successive trophic levels, starting

with 0.003 ppb (ppb = parts per billion) in water it ultimately reached25 ppm (ppm parts per million) in fish-eating birds. Highconcentrations of DDT disturb calcium metabolism birds, whichcauses thinning of egg shell and their premature breaking eventuallycausing decline in bird population.

(c) Ground water depletion and ways for its replenishment.Underground water is more pure and safe for drinking. It is getting polluted particularly in industrialtowns. The common sources of underground water pollution are sewage and industrial effluentsspilled over the ground. The fertilizers and pesticides used in fields also act as pollutants. Pollutionis also increased due to seepage from refuse dumps, septic tanks and seepage pits.

Method to control. Sewage and factory wastes should be treated to clean them before their releaseinto water sources.

Q. 11. What is soil pollution? how is solid waste generated

Ans. Soil Pollution. Alteration in soil leading to reduced productivity is called soil pollution. The soilpollutants include chemicals, fertilizers, organic manure, pesticides radioactive wastes anddiscarded household materials. Contamination of soil with human and animal excreta is a serioushealth hazard. Air and water pollutants also reach the soil and pollute it too.

Flow

chart of soil pollution

Solid wastes are also generatedin industries.

1. Thermal power plantsgenerate tremendous amount of fly ash that is made up of oxides

of silica, iron and aluminium, andlow concentrations of toxic heavymetals. Fly ash can be used incement and construction industry,or buried in landfills. There isalso a possibility of using it for


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soil amendment because itincreases moisture retention andaeration of a soil.

2. Industries producing metals,pesticides paper, rubber, dye,chemicals, etc. also generatelarge amount of hazardous solid

wastes that are corrosive, highly inflammable and toxic to humans and other organisms.3. Hospitals generate hazardous wastes that contain disinfectants and other harmful chemicals, andalso pathogenic microorganisms. Such wastes also require careful treatment and disposal.

4. Defuncts ships.

5. e-wastes.

Q. 12. Discuss briefly the following:

(a) Radioactive wastes

(b) Defunct ships

(c) Municipal solid wastes.

Ans. (a) Radioactive wastes. Use of nuclear energy has two most serious problems. The first isaccidental leakage and the second is safe disposal of radioactive wastes. Wastes from atomicpower plants come in the form of spent fuels of uranium and plutonium. People working in suchpower plants, nuclear reactors, fuel processors1 etc. are vulnerable to their exposure. These alsoundergo biological magnification and may reach to 75,000 times in birds.

Radio isotopes. Many radioactive isotopes like and their compounds are used inscientific researches. The waste water of these research centres contain theradioactive elements which may reach the human beings through water and foodchains.

Such wastes are first concentrated to educe the volume and then kept for 50-100 years in smallponds within the premises of nuclear power plants. This interim storage causes considerable decayof radioactivity and lessening of heat problem. It has been recommended that subsequent storageshould be done in suitably shielded containers buried within the rocks, about 500 m deep insideEarth. However, this method of disposal is meeting stiff opposition from the public.

(b) Defunct ships and e-wastes. Defunct ships are a kind of solid waste requiring proper disposal.Such ships are broken down in developing countries because of cheap labour and for scrap metal.They often contain toxic substances such as asbestos, polychlorinated biphenyls, tributyltin, leadand mercury.

(c) Municipal Solid Wastes. Solid wastes refer to everything that goes out in trash. Municipal solidwastes are wastes from homes, offices, stores, schools, etc. that are collected and disposed by themunicipality. The municipal solid wastes generally comprise paper, food wastes, glass, metals,rubber, leather, textile, etc. Burning reduces

the volume of the wastes, although it is generally not complete arid open dumps often serve as thebreeding ground for rats and flies.

Q. 13 What initiatives were taken for reducing vehicular air pollution in Delhi? Has the air quality improved in Delhi?


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Ans. Automobiles are the major sources of air pollution in Delhi because it has

very high number of cars. Some specific measures taken to reduce vehicular air pollution are asfollows

1. Use of CNG (Compressed Natural Gas) for its public transport system.

2 Phasing out of old vehicles

3. Use of unleaded petrol.

4. Use of low sulphur petrol and diesel.

5. Use of catalytic converter in vehicles.

6. Application of Euro II norms for vehicles.

Because of above mentioned steps taken up by the Government, the air quality of Delhi hasimproved with a substantial fall in carbon monoxide, oxides of sulphur and nitrogen level between1997-2005.

Q. 14. What is nuclear fall-out? Suggest a few protective measures against nuclear fall-out.

Ans. Nuclear Fall-Out. The release of radio-active isotopes into the atmosphere after a nuclear explosion is called nuclear fall-out. The latter has both immediate and delayed effects. Theimmediate effect is through iodine-131 and strontium-90, which enter the human body either directlyor through food chain. Radio-active iodine-131 gets concentrated in the thyroid gland like ordinaryiodine (1-127). It is used similarly in the synthesis of thyroxine. Through the latter, it reaches everybody part and causes damage to white blood coijucles, bone marrow, spleen, lymph nodes, etc. Itimpairs eye sight and produces sterility, skin cancer and lung tumours.

Radio-active strontium (Sr-90) is mistaken for calcium and enters the bones. Here, it causes bonecancer. The isotope also degenerates body tissues.

Nuclear fall-out passes on to other areas through air currents. Radio-active isotopes mix up withclouds and reach the soils. Thus an atmospheric nuclear explosion in China was found to haveincreased background radio-activity in Japan. After entering the food chain, the radio-activeisotopes induce mutations in both plants and animals.

Protective Measures. There is no mechanism to offset the effect of ionising radiations. All theprotective measures are, therefore, preventive in nature. In the first step it is extremely impartant tosee that the background radiation does not increase. Prevention of leakage in the nuclear reactors,dumping of nuclear wastes deep in the earth, renunciation of atomic explosions or development of non-radioactive explosion technology are important for the survival of mankind.

Q. 15. Write a note on control of radioactive pollution.

Ans. Control of Radioactive Pollution. The radioactive wastes which come out from industry,medicinal plants, nuclear reactors should be stored either in closed drums or in very, largeunderground airtight cemented tanks. Moreover, the intermediate radioactive wastes should bedisposed off into the environment after diluting it with some inert material. There should be a ban onnuclear explosions throughout the whole world. Concerted efforts are being made in this direction byseveral countries, including India.

Industrial wastes may be discharged into the environment, only after the necessary treatment so thatthe radioactivity is at a lower level. Wastes may be discharged into sewer system or into thestreams. Before discharge, it is said that low activity wastes are stored for some time, so as toreduce the activity. In case of high activity wastes, they cannot be discharged. Now-a-days, small


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quantities of high activities wastes are converted into solids such as concrete and then it is buriedunderground or in sea. According to recent survey, these wastes may also be converted into glassyor ceramic material which is then calcined to alumina or zirconia and leached. Disposal of wastesat sea has also been tried.

Q. 16. Describe role of individual in reducing pollution.

Ans. Role of individual in reducing pollution.

1. Use of unleaded petrol or CNG in vehicles as fuel.

2. Use of reformulated gasoline to save ozone in the atmosphere.

3. Use of generators in residential areas should be avoided.

4. Plantation of trees.

5. Excessive and unplanned use of fertilizer should be avoided.

6. Biodegradable material should be used.

7. Do not blow horn with jarring sound.

8. Radio, transistors, T.V., Music system should be kept at low volume to control noise pollution.

Q. 17. How are solid wastes generated?

Ans. Solid wastes are also generated in industries.

1. Thermal power plants generate tremendous amount of fly ash that is made up of oxides of silica,iron and aluminium, and low concentrations of toxic heavy metals. Fly ash can be used in cement

and construction industry, or buried in landfills. There is also a possibility of using it for soilamendment because it increases moisture retention and aeration of a soil.

2. Industries producing metals, pesticides, paper, rubber, dye, chemicals, etc. also generate largeamount of hazardous solid wastes that are corrosive, highly

inflammable and toxic to humans and other organisms.

3. Hospitals generate hazardous wastes that contain disinfectants and other harmful chemicals, andalso pathogenic microorganisms. Such wastes also require careful treatment and disposal.

4. Defuncts ships.5. e-wastes.

Long Answer Type Questions

Q. 1. Describe briefly environmental pollution and pollutant.

Ans. Pollution. Pollution is any change in physical, chemical or biological characteristics of theenvironment that has the potentiality to harm human life, life of other desirable species, naturalresources, cultural assets and industries. Contamination is presence of harmful organisms or their

toxins that cause discomfort or disease.Natural pollution is pollution caused by natural sources, e.g., volcanic eruptions, release of methaneby paddy fields and cattle, release of carbon monoxide by plants and animals, emission of naturalgas, ozone, nitrogen oxides, soil erosion, dust storms, cosmic rays, ultra-violet rays, etc.


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Man-made pollution is pollution resulting from human activities like burning of fossil fuels,deforestation, mining, sewage, industrial effluents, pesticides, fertilizers, etc. Amount of man madeatmospheric pollution is hardly 0.05% of total but is more dangerous because of its concentration incertain localities,

Pollutant. It is a substance (e.g. dust, smoke), chemical (e.g. SO2) or factor (e.g. heat, noise) that onrelease into the environment has an actual or potential adverse effect on human interests. Pollutantcan also be defined as a constituent in the wrong amount, at a wrong place or at a wrong time.

Types of pollutants :

Pollutants can be of following types :

(a) Biodegradable pollutants : The pollutants which are degraded by natural factors and aredecomposed by natural activities are biodegradable pollutants.

(b) Non-biodegradable pollutants : There are pollutants which cannot be purified by natural methods.Plastic products, many chemicals, long chain detergents, glass, aluminium and many other artificialsynthetic products manufactured by man come under this category.

Pollution according to physical nature of pollutants.

According to the physical nature of the pollutants, the categories include : gases, particulate matter,temperature, noise, radioactivity, etc. These categories can be named as gaseous pollution, dustpollution, thermal pollution, noise pollution, radioactive pollution, etc.

Types of pollution according to the part of environment.

1. Air pollution (Atmosphere)

2. Water pollution (Hydrosphere)

3. Soil pollution (Lithosphere)

Types of pollution on the basis of origin

1. Natural e.g. volcanic eruption.

2. AnthropogeniC e.g. Man made such as industrial pollution.

Air pollution. Release of harmful materials into the air is called air or atmospheric pollution. It is thedegradation of air quality and atmosphere condition. Air pollutants include gaseous materials,

suspended particles and radioactive substances.

Water pollution. Pollutants in surface run off (and storm water) vary according to the nature of landover which it flows. The run off from agricultural land is contaminated with pesticide residues andresidues of inorganic fertilizers. The run off from Urban areas mainly contains biodegradableorganic pollutants. Industrial sites may contribute to varied types of pollutants like heavy metals,acids and various inorganic compounds. All these pollutants in the run off heavily contaminate our surface water and groundwater resources.

Soil pollution. Alteration in soil leading to reduced productivity is called soil pollution. The soilpollutants include chemicals, fertilizers, organic manure, pesticides, radioactive wastes and

discarded, household materials. Contamination of soil with human and animal excreta is a serioushealth hazard. Air and water pollutants also reach the soil and pollute it too.

Noise pollution. Unbearable sound is called noise. When sound takes the form of noise then it iscalled as noise pollution. Sound above 60-70 decibels comes in the noise category. Noise pollution


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is the contribution of metropolitan culture and industrial development. The main sources of noisepollution are loudspeakers, pressure horns, supersonic jets etc.

Noise pollution causes mental tensions, physical tiredness, loss in learning capacity or completedeafness. To help protect against sound pollution formation of green belts in metropolitan cities andone of the sound proof materials come in use.

Q. 2. (a) What are reasons for depletion of ozone layer?

(b) List the adverse effects of depletion of ozone layer. Suggest measures to prevent it.

Ans. (a) Ozone Depletion. Ozone layer or shield is present in the stratosphere. It protects the earthfrom short-wave ultra-violet rays (below 300 nm) by changing the same into infra-red rays. A largehole has appeared in ozone shield over Antarctica (first detected by Farman, 1982) and a smaller one over North Pole. Size of the holes varies with the seasons.

Ozone hole. During the period 1956-1970 the spring time 03 layer thickness above Anarcticavaried from 280-325 Dobson unit. Thickness was sharply reduced to 225 DU in 1979 and 136 DUin 1985. Antarctic air is completely isolated from rest of world by natural circulation of wind called as

polar vertex. The decline in spring time, ozone layer thickness is called ozone hole. It was first notedin 1985 over Antarctica. Thinning of ozone shield has also been reported elsewhere (e.g., 8%between 3050NP).

Depletion of ozone layer allows harmful ultra-violet radiations to reach earth. It is the major cause of skin cancer, cataract, dimming of eye sight, decrease in immune system and increasedsusceptibility to herpes.

Thinning of ozone shield is being caused by a number of pollutants like chlorofluorocarbolls (14% of total depletion), nitrogen oxides (3.5% depletion), sulphur dioxide, halon, carbon tetrachloride,methyl chloroform, chlorine, etc. Many of these are being released by jets flying in the stratosphere

and rockets being fired into space. Others are persistent in the troposphere and gradually pass intostratosphere.

(1) Ozone layer as protective layer. The ozone layer in the stratosphere is very useful to humanbeings because it absorbs the major part of harmful ultraviolet radiation coming from the sun.Therefore, it is called protective layer. However, i.t has been observed that

the ozone layer is getting depleted. One of the reasons for depletion of ozone layer is action of aerosols spray propellants. These are the chemicals such as fluorocarbons andchloro_fluorocarbons. These compounds react with ozone gas in the atmosphere thereby depletingit. Scientists all over the world are worried at the destruction of ozone layer. If the ozone layer in theatmosphere is significantly decreased, these harmful radiations would reach the earth and wouldcause many damages such as skincncergenetic disorders in man and other living forms. Efforts arebeing made to find substitutes of these chemicals which do not react with ozone.

effects of UV radiations on human.

1. In humans, the increased UV radiation increases the incidence in cancer (including nelanoma).

2. Reduces the functioning of immune system.

3. Cornea absorbs UV-B radiations, and a high dose of UV-B causes inflammation of cornea calledsnow blindness, cataract etc. Exposure may permanently damage cornea and cause cataract.

Q. 3. What is air pollution ? Write the main sources, preventive and control measures.


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Ans. Air Pollution. Air pollution refers to the release into the atmosphere of materials that areharmful to man, other animals, plants and buildings or other objects.

Sources of Air Pollution

The major sources of air pollution are fossil fuels (coal and petroleum) and industries.

Human Sources. Many activities done by man are the main source of air pollution. These activitiescan be divided into following categories

1. Combustion activities.

2. Industrial activities.

3. Agricultural works.

4. Use of solvetits.

5. Activities concerned with atomic energy.

Preventive measures for air pollution

To prevent and control air pollution, two types of measures can be adopted.

1. Instead of releasing poisonous gases containing various pollutants into the atmosphere theycould be destroyed or used by some other measures.

2. Converting harmful pollutants to harmless products and then releasing them into the atmosphere.

Control measures for minimising air pollution.

1. Simple combustible solid wastes should be burnt in incinerators.2. Automobiles must be either made to eliminate the use of gasoline and diesel oil or completecombustion is obtained in the engine so that harmful products are omitted.

Catalytic converter. Automobiles need to be well maintained so that they do not emit muchpollutants. Catalytic converters, having expensive metals namely platinum-palladium and rhodium asthe catalysts, are fitted into automobiles for reducing emission of gases. As the exhaust passesthrough the catalytic converter, unburnt hydrocarbons are converted into carbon dioxide and water and carbon monoxide and nitric oxide are changed to carbon dioxide and nitrogen gas,respectively. Motor vehicles equipped with catalytic converter should use unleaded petrol because

leaded petrol inactivates the catalyst.

It has been established that installation of catalytic convertors can slash carbon monoxide emissionfrom 90 grams to 3.4 grams per mile run. So if half the vehicles on Delhi and Mumbai roads aremade to install such catalytic convertors, then total CO emission in India can be reduced by 70 per cent.

3. There should be cut in the use of agricultural sprays.

4. Excessive and undesirable burning of vegetation should be stopped.

5. Smoking should be stopped.6. Use of electrostatic precipitators and filters in the factories to minimise atmospheric pollution.

7. Use of tall chimneys can substantially reduce the concentration of pollutant at ground level.


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8. Weather forecasts can help in controlling air pollution as the meteorological conditions affect thedispersion, dilution and mixing of various emission and proper operation of factory schedule e.g.when atmospheric stagnation or calm is predicted, a power plant should switch over from coal togas.

9. Separation of pollutants from harmless gases.

10. Dispersion of pollutants to innocuous products before releasing into atmosphere.

11. Use of electrostatic precipitator and scrubber.

An electrostatic precipitator. It removes over 99% particulate matter present in the exhaust from athermal power plant. It has electrode wires and a stage of collecting plates. The electrode wires aremaintained at several thousand volts, which produce a corona that releases electrons. Theseelectrons attach to dust particles and give them a net negative charge within a very small fraction of a second. The collecting plates are grounded and attract the charged dust particles. The velocity of air between the plates must be low enough to allow the dust to fall.

Electrostatic precipitator

Scrubber. A scrubber can removegases like sulphur dioxide. In ascrubber, the exhaust is passed througha spray of water or lime. Water dissolves gases and lime reacts withsulphur dioxide to form a precipitate of calcium sulphate or suiphite.

Scrubber

Q.4. Make a flow chart of water pollutants.

Ans. Water pollutants

Flow chart of water pollutants

Q. 5. Discuss the harmful effects of water pollution.

Ans. Effects of Water Pollution

1. Effect on animals. Oxygen contents become less inpolluted water. As a result of this, fishes and other aquaticanimals experience fatal effects andthe water begins to stink. When thesuspended impurities settle down atthe bottom of rivers, ponds etc., thenalgae and other aquatic plants aredestroyed. Human beings feeding onpoisoned animals developed acrippling deformity called minimatadisease.

2. Effect on plant life. If polluted water


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(a) Industrial effluents give colour and turbidity to the receiving waters.

(b) Acids and alkalies present in effluent render the water corrosive and damage

the pipes.

(c) Heavy metals and other toxic substances may kill fish and other aquatic life,

animals and vegetables. -

(d) The effluents undergo putrefaction to form evil odours and objectionable tastes.

(e) The toxic substances may kill the friendly bacteria and the natural purification

processes of the streams are thus inhibited.

(f) Heated effluents discharged into rivers may cause harmful rise in the

temperature of the stream and thus ecosystem of the water course may possibly

be changed.

(g) Some of the trade substance may contain pathogenic bacteria.

Q. 6. Give a brief account of purification of water for public use.

Ans. Purification of Water for Public Use

The destruction of water-borne pathogens like bacteria, viruses and amoebic cysts

by different methods is called disinfection. The process of disinfection involves the killing of those

living organisms which can spread or transmit infection through or inwater. There are several methods for disinfection of drinking water. The various

processes are as follows

1. Disinfection by light. Sunlight is a natural disinfectant. The ultraviolet light is

a good source for this purpose. The common source of UV light is a mercury lamp

made of quartz.

2. Disinfection by heat. The drinking water can be disinfected by heating it to its

boiling point. High temperature kill bacteria.

3. Disinfection by alkalies and acids. The bacteria die in a very short time in

highly acidic or alkaline waters.

4. Disinfection by surface active chemicals. In this process, detergents, i.e., surface activesubstances are used.

5. Disinfection by gases. For routine disinfection and purification of drinking

water, chlorine is generally used as it is both efficient and cheap. In India, generally

chlorine gas or bleaching powder is used. Besides chlorine, other substances which can


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be used for disinfection are bromine and iodine.

Ozone is used for disinfecting drinking water in countries like USA, West Germany, France andsome African countries. It serves as a disinfectant, removes turbidity and colour producingsubstances. As ozone is a toxic substance, it is handled very carefully within certain limits.

6. Disinfection by metal ions. Silver ions are bactericidal (kill bacteria) and disinfection occurs evenif I part of silver is present in one hundred million parts of water. Moreover, copper ions and zinc

ions are also used, as they kill a number of viruses and other micro-organisms.Leaves of tulsi are also responsible of killing viruses and other micro-organisms

both in water and milk.

7. Purification by coagulation. Several coagulants like alum, ferric chloride, lime are used, wherebyall colloidal particles present in drinking water coagulate. they settle down and thus water can bedecantated.

8. Potassium permanganate is a good disinfectant and an oxidising agent. It is added to water of tube well etc. so that bacteria in water die. But being costlier than chlorine, it cannot be used on acommercial scale.

Q. 7. What is noise pollution ? List the sources of noise pollution.

Ans. Noise pollution. The sound that we hear goes into our brain by way of our ears. Normally, thesound which is pleasing to the ears may be termed as music. The same music may be called noise,if quiet is desired. So, we can define noise as an unwanted sound.

Noise is produced due to congestion in urban areas, vehicles, railways, helicopters, jets, rockets,radio, T.V., call bells, alarm clocks, telephone rings, pressure horns, machines or factories, coolers,loudspeakers, mixer grinders, public broadcasting by religious institutions etc. The waves left bysupersonic jets give rise to sonic booms or sudden rattling of doors and windows.

There are two main characteristics of sound, viz., (a) Pitch and frequency of sound waves and (b)Loudness or intensity of sound waves.

The pitch of a sound depends on its frequency. A sound of higher frequency has a higher pitch. Thepitch of womans voice is higher than that of a man. The human ear can detect sounds over a widerange of intensities and frequencies. Normally, the human ear is sensitive to sounds havingfrequencies varying from 17 to 20,000 Hz (1 Hz = 1 cycle per second). Those sound waves whichhave frequency lower than 17 Hz are termed infrasonic and waves which have frequency higher than20,000 Hz are termed ultrasonic.

The unit of loudness or sound intensity is called decibel or dB with zero as the limit of hearing. Atenfold increase in sound intensity increases loudness by 10 dB, e.g., 100 or 102 by 20 dB, 1000 or i0 by 30 dB, 10000 or 10 by 40 dB, 10 by 70 dB, 1012 by 120 dB. An instrument called sound levelmeter is used. Sound becomes polluting noise at about 80 dB. It becomes uncomfortable above100 dB.

Sources of noise pollution

Noisepollutionoriginatesfrom anumber of sources like:


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agriculture,industry,

defence,vehicular traffic,communityfunctions,

domesticchorus andpersonal

entertainments.

1. Domestic Gadgets. Mixers pressure cookers, washing m chines, desert coolers, fans, exhaustfans, air conditioners, vacuum cleaners, telephones, etc.

2. Personal Entertainment. Transistor, radio, record/ cassette player, T.V.

3. Community Functions. Festivals, marriages, politicai social and religious functions, publicannouncements, crackers.

4. Defence Equipment. Tanks, artillery, practice firing, explosions, rocket launching.

5. Industries. Textile mills, rolling mills, printing presses, engineering establishments, shellers,expellers, stone crushers, saw mills.

6. Builders. Bull dozers, road rollers, dynamite blasting, oncrete mixers, trollies, concrete breakers,scrapers, etc.

7. Agricultural Operations. Harvesters, threshers, tractors, pump sets, lawn mowers, etc.8. Transport Vehicle. Scooters, motor cycles, mopeds, cars, buses, trucks, trains, helicopters,aeroplanes. Road transport is the major source of noise pollution in towns and cities. Intra-city railtransport causes a lot of noise along the railway lines. Airports produce the maximum noise duringlanding and take off of aeroplanes.


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9. Commercial Establishments. Music, T.V., telephones, exhaust fans, type writers, coolers, air conditioners, etc.

Q. 8. Discuss the effects of noise pollution. Explain various measures to control noisepollution..

Ans. Effects of Noise Pollution. Noise affects man adversely in several ways, i.e., having ability tocommunicate, behaviour etc. Unlike smoke pollution, noise pollution is not visible. Normally, thepeople remain unaware of noise pollution, till it is too late to overcome it. The human ear has asafety mechanism to protect itself from the damage, provided the exposure to noise is notcontinuous or for a long period. Excessive noise causes loss of hearing and disturbs mental peace.

1. Impairment of Hearing. The city noise is generally more than the loudness. Therefore, citydwellers are prone to deafness with advancing age. Impairment of hearing is slow at a noise of 80dB. It is rapid at 90 - 100 dB. An exposure to 90 dB noise for eight hours causes a temporary lossof hearing upto 35 dB. Workers engaged in noisy factories lose the ability to hear soft sounds andwhispers within 2-3 years.

2. Damage to Ear Drum and Ear Bones. A sudden loud noise can damage ear drum and displaceear bones. This results in partial or complete deafness.

3. Interference in Conversation and Hearing. Noise of a passing truck or bus

interferes in class room teachingif the class room happens to by near the road.

You cannot have intimate conversation in a social gathering due to noise.

4. Anxiety and Stress. Long exposure to noise above 90 dB brings about stress

and anxiety in many persons. It may lead to fright (sudden and extreme fear).

5. Hypertension. Sound pollution stimulates increased adrenaline hormone secretion rulting innarrowing of blood vessels of the body except brain.

This produues high blood pressure or hypertension, over working of heart and abnormal heartrhythm.

6. Eye Sight. Noise pollution causes dilation of eye pupil, impairment of night vision and colour perception. Unwanted light enters the eyes producing glare.

The latter may lead to accident.

7. Insomnia. Constant high level noise (e.g., from a nearby function) or noisy

interruption (e.g., flights from nearby airport) result in insomnia

(sleeplessness), lack of concentration and headache.

Control of Nois Pollution

1. Construction of sound-proof rooms for noisy machines in industries.

2. Radios and transistors should be kept at low volume.

3. Use of hornswith jarring sound should be banned.

4. Noise producing industries, aerodromes, railways stations, etc. should be shifted away from theinhabited areas.


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5. Proper laws should be enforced to check the misuse of loudspeakers and public announcementsystems.

6. Need to enforce silence zone around institutions like educational institutes, residential areas,hospitals, etc.

7. Sound absorbing techniques like acoustical furnishing should be extensively employed.

8. Noise should be deflected away from the receiver by using mechanical devices.

9. Green muffler scheme involves the growing green plants along roadsides to

reduce noise pollution.

Q. 9. Describe harmful effects of non-ionising radiation, and ionising radiations.

Ans. Harmful effect of non-ionising radiation.

1. Eye Sight. Eyes are highly sensitive to ultra-violet radiations. Damage is caused by reflections

from coastal sand, snow and directly looking towards sun during eclipse. UV radiations damage thecells of cornea. Cornea has the power to repair the damage in the initial stages but prolongedexposure leads to permanent blindness.

2. Sunburn. UV-radiations injure the cells of germinative layer of the skin and cause rupturing of subcutaneous blood capillaries. It produces blisters and reddening of skin.

3. Mutation and Cancers. Ultraviolet rays increase the incidence of cancers and mutations in man.They effect every part and process of the living beings by inactivating organic molecules (proteins,enzymes, RNAs, DNA) that absorb the rays. Some n1olecules are more sensitive than the others. Afew revert back to their original form after initial alteration. The effect of ultraviolet radiations is due

to polymerisation and breakage of linkges. Organisms have an inbuilt mechanism to correct or replace the changed molecules by the activity of DNA. However, DNA is itself sensitive to ultravioletradiations. Its sensitivity is due to its bases, especially pyrimidines which form dimers in thepresence of UV radiations. The reaction is reversible in low doses. DNA is also able to repair itself to some extent in the presence of longer wavelengths of light. It is known as photo-reactivation. Aphoto-reactivating enzyme is. thought to take part in this process. Another repair processindependent of light also occurs in DNA.

Harmful effects of ionising radiations.

Harmful Effects. The effects were first noted in 1909 when it was found that uranium miners suffer

from skin burn and cancer due to radiations from the radioactive minerals. Different organismsshow different sensitivity to ionising radiations. For example, tests have shown that pine trees arekilled at radiations in which oak trees continue to thrive comfortably. It has also been reported thathigh altitude plants have developed polyploidy (increase in the number of chromosome sets) as aprotective mechanism against radiations. Parts of coastal areas in South India have a high degreeof background radiation which was formerly considered to be quite harmful to human beings.

lonising radiations have both immediate or short-range and delayed or long- range effects.

(i) Short Range (Immediate) Effects. They appear within days or a few weeks after exposure. Theeffects include loss of hair, nails, subcutaneous bleeding, change in number and proportion of blood

cells, changed metabolism, etc.(ii) Long Range (Delayed) Effects. They appear several months or even years after the exposure.The effects are caused by development of genetic changes,

mutations, shortening of life span, formation of tumours, cancers, etc. The effect of mutations can


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persist in the human race. Most of the mutations are harmful. Any increase in their number is,therefore, bound to increase the harmful genetic changes in man. Previously, most of the harmfulmutations in man were eliminated through death in the infant or foetus stage. Modern medicinesand surgery have increased the survival chances of harmful mutations. They will, therefore, persistand accumulate in human race. Ultimately, the whole human race shall degenerate genetically onaccount of

the cumulative effect of harmful mutations.

Q. 10. Write a note on Control of Thermal Pollution.

Ans. Control of Thermal Pollution. Though the effects of thermal pollution are not so severe, controlof thermal pollution is necessary since in future the effects may worsen. The use of water from awater course for cooling purposes, with subsequent return to the waterway after passage throughthe condenser is termed as once-through cooling. To reduce the magnitude of the pollution, theoutlet water can be made to give up some of its heat to the atmosphere and then may bedischarged into the water course. To make it effective, cooling towers are primarily used in manypower plants and artificial lakes or cooling ponds are situated in some of the places.

1. Cooling towers. Cooling towers transfer some of the heat from cooling water to the atmosphere,most probably through the evaporation of water. Evaporative cooling towers are of the following twotypes

(a) Natural draft towers. In such towers, hot water is sprayed down through a rising current of air. Thewater vapour gives its heat to the counter-current air and gets cooled. The cooled water is collectedat the bottom and returned to the water body. However, the installation and operation costs of suchtowers are high.

(b) Mechanical draft towers. In such towers, air flow is forced or induced by fans. Hot water during itspassage to water course gets cooled by the action of air. However, these towers are not preferred,

as they create annoyable noise due to the operation of fans and operation cost is also high.Evaporative cooling towers cool the water by 10C or more, but they. evaporate nearly 2 per cent or more of water during evaporation. One of the demerits of such towers is that they may form fogunder cold weather, creating driving hazards over an extended area. Similarly, in non-evaporativecooling towers, heat is transferred directly to the air by means of heat exchangers. It, however,involves high operational cost.

2. Artificial lakes or cooling ponds. These are the man-made bodies of water which offer onepossible alternative to one-through cooling. The heated effluents can be discharged into the lake atone end and the water for cooling purposes may be drawn at the other end since the heat would

eventually be dissipated through evaporation, the cooling pond would have to be replenishedcontinuously. Such cooling ponds are in use in some locations, but they are not a very attractivealternative since they require so much space. -A one megawatt plant, for example, would requirecooling pond with 1000-2000 acres of surface area. In many areas, the cost of using land for thispurpose would be too great to justify the procedure.

Q. 11. Write a note on Disaster Management.

Ans. Disaster is any sudden event of calamity which causes great effect on the human population,plants, animals and property. Disasters are of two types

Natural Man made

Natural Disasters


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1. EarthquakeS. Sudden tremors of the earths surface ar produced due to movement of tectonicplates under the earth. This displacement of earths crust releases energy stored within the earthsinterior which produces vibratory waves. The intensity of earthquake is measured by Richter, Scalewhich ranges from 0 to 9. The point from which the earthquake originates is called as epicentre.

Prevention, Control & Mitigation

(i) Constructing earthquake resistant building in the known earthquake prone zones e.g. wooden

houses are preferred in Japan.(ii) Installation of earthquake study centres studying seismic ;activities and analysis of seismiczones.

(iii) There must be insurance policies for earthquake victims o rehabilitate them.

(iv) Creation of special task forces, fully trained and equipped, to manage such calamities withinshortest possible time.

2. Tsunami. The impact of earthquake is high at sea area of origin. In this, most serious form of earthquake, giant seismic tidal waves of as high as 10 metre or more travel at the speed of 1,000km/hour or faster, away from the epicentre of, the earthquake. Tsunamis may also be caused due tounderwater volcanic eruptions or seafloor slumping.

Prevention, Control & Mitigation

(i) Planting more trees on the coastal areas.

(ii) Timely warning and speedy evacuation of people.

(iii) Conservation of mangroves in the coastal areas.

(iv) Construction of embankments in inhabitable areas.

(v) Immediate relief and rehabilitation to the affected people.

3. Drought. A drought is the drying up condition of the land due to insufficient or absence of rainfallfor a long period affecting the vegetation1 animal and human life.

Control Measures

(i) Rain water harvesting and canal irrigation.

(ii) Improvement of agricultural practices like dryland forming to conserve water in drought proneareas.

(iii) Stopping paddy cultivation in areas of water scarcity and growing drought resistant variety of crops.

(iv) Promoting social forestry and wasteland reclamation, growing species according to theecological requirements of the area.

(v) Supplying food, fodder and water to drought-hit people and their rehabilitation with all essentialrequirements of life.

4. Flood. A flood occurs due to continuous heavy rainfall in an area, overflowing of rivers andsubmerging the surounding areas damaging life and property.

Control


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(i) Various preventive measures are proper embankment of water bodies, building check dams onflood-prone streams, prohibiting cultivation in flood plain of rivers and growing forests and perennialtrees, interlinking of river of the country and constructing houses on raised platforms and supportedby reinforced stilts.

(ii) Floods can be controlled by collecting data from meteorological department and alerting thepeople of affecting area.

(iii) Educating the people about the steps to be taken in the event of disaster.(iv) Hill slopes and catchment areas of rivers must be afforested and reforested.

5. Cyclones. A cyclone is powerful circular or oval swirling storm of high velocity wind in the coastalregions of Indian ocean. It is called hurricane in Atlantic

ocean, typhoon in Western Pacific and Willy-willy in sea around Australia.

Control

(i) Afforestation of coastal areas is the best measure.

(ii) Construction oldams, embankments, wind breakers etc.

(iii) Conservation of mangrooveS in coastal plains.

(iv) Better forecast, warning systems with the help of remote sensing satellites.

(v) Construction of cyclone proof houses and building in coastal areas.

6. Landslides. Landslide is the sudden downslope movement of a mass of rock or soil due togravitational pull, generally in the rainy season.

Control

(i) Afforestation and reforestation in the landslide prone areas is the best measure.

(ii) There should be no construction activity in slopy areas.

(iii) Proper drainage of surface and sub surface water.

(iv) Making concrete support at the base of slope along the road.

(v) Construction of curved stone blocks in the risky areas.

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