Pollution and its Factors Chapter 5

 

CHAPTER:-5

Environmental Science : Pollution and its Factors

INTRODUCTION

Pollution may be defined as an undesirable change in the physical, chemical or biological characteristics of air, water and land that may be harmful to human life and other animals, living conditions, industrial processes and cultural assets. Pollution can be natural or man- made. The agents that pollute are called pollutants.

Pollutants

Pollutants are by-products of man’s action. The important pollutants are summarised below:

• Deposited matter—Soot, smoke, tar or dust and domestic wastes.

• Gases—CO, nitrogen oxides, sulphur oxides, halogens (chlorine, bromine and iodine).

• Metals—Lead, zinc, iron and chromium.

• Industrial pollutants—Benzene, ether, acetic acid etc., and cyanide compounds.

• Agriculture pollutants—Pesticides, herbicides, fungicides and fertilizers.

• Photochemical pollutants—Ozone, oxides of nitrogen, aldehydes, ethylene, photochemical smog and proxy acetyl nitrate.

• Radiation pollutants—Radioactive substances and radioactive fall-outs of the nuclear test.

Classification of Pollutants

On the basis of natural disposal, pollutants are of two types:

(i) Non-degradable pollutants

These are the pollutants, which degrade at a very slow pace by the natural biological processes. These are inorganic compounds such as salts (chlorides), metallic oxides waste producing materials and materials like, aluminium cans, mercuric salts and even  DDT. These continue to accumulate in the environment

(i) Biodegradable pollutants

These include domestic sewage that easily decomposes under natural processes and can be rapidly decomposed by natural/ artificial methods. These cause serious problems when accumulated in large amounts as the pace of deposition exceeds the pace of decomposition of disposal.

On the basis of the form in which they persist after their release into the environment, pollutants can be categorized under two types:

(i) Primary pollutants : These include those substances, which are emitted directly from some identifiable sources. This include-

(a) Sulphur compounds: SO2, SO3, H2S produced by the oxidation of fuel.

(b) Carbon compounds:  Oxides  of  carbon  (CO+CO2)  and  hydrocarbons.

(c) Nitrogen compounds: NO2 and NH3.

(d) Halogen compounds: Hydrogen fluoride (HF) and hydrochloric acid (HCl).

(e) Particles of different size and substances: These are found suspended in air. The fine particles below the diameter of 100u are more abundant and include particles of metals, carbon, tar, pollen, fungi, bacteria, silicates and others.

(ii) Secondary pollutants. The secondary pollutants are produced by the combination of primary emitted pollutants. in the atmosphere. In bright sunlight, a photochemical reaction occurs between nitrogen oxides; oxygen and waste hydrocarbons from gasoline that forms peroxyacetyle nitrate (PAN) and ozone (O3), Both of them are toxic components of smog and cause smarting eyes and lung damage.

(iii) Smog. The fog deposited with smoke and chemical fumes forms a dark and thick covering, the smog. Smog is very common in almost all the industrial areas as the smog is trapped for many days by the stagnant air. It is harmful both for animals and plants.

AIR POLLUTION

The WHO defines air pollution as the presence of materials in the air in such concentration which are harmful to man and his environment. A number of ingredients find their way in the air and these are mostly gases, which rapidly spread over wide areas.

SOURCES OF AIR POLLUTION

Various sources of air pollution are fossil fuels, industries, agricultural activities, wars, natural causes arid emissions from vehicles.

(i) Burning Fossil Fuels

Burning of wood, charcoal and other fossil fuels causes air pollution by the release of carbon dioxide (CO2), carbon sulphur dioxide etc. Petroleum consists mainly of hydrocarbons, sulphur and nitrogen.

(ii) Emissions from Automobiles

Vehicles are  mainly  responsible  for  more  than  80%  of  total  air  pollution.  The  major

pollutants released from automobiles, locomotives, aircraft etc., include CO, unburnt hydrocarbons and nitrogen oxide.

(iii) Industries

Paper and pulpfactories, petroleum refineries, fertilizer plants, and steel industries, thermal power plants are the main sources of air pollution. They add various harmful gases like CO, SO3, NO, Hydrocarbons etc., to the atmosphere. Textile factories release cotton dust into the air. Cities experiencing this type of pollution are Kanpur, Surat and Ahmedabad. The pesticide and insecticide industries are posing serious threat to the environment. Food processing industries and tanneries emit offensive odors. Release of poisonous gases from accidents also poses serious threats. e.g. Bhopal Gas Tragedy in which methyl isocynate (MIC) gas leakage killed several people. In Tokyo, about 34 tones of carbon particles mixed with other suspended particles settle per square kilometer every day.

(iv) Agricultural Activities

Spraying of insecticides and weedicides also cause air pollution. These,  when  inhaled create severe problems to both animals and man.

(v) Wars

Various forms of explosives used in war pollute  the  air  by  releasing  poisonous  gases. This greatly disturbs the ecology of the area. Nuclear  explosions  pollute  air  by  radioactive rays. The effects of nuclear explosions on Hiroshima and Nagasaki are well-known examples.

(vi) Natural Causes

Gas emissions from active volcanoes, marsh gas, spores of fungi and pollens are the natural causes of air pollution.

COMMON AIR POLLUTANTS

Air pollutants are of two main types ~gaseous and particulate. Oxides of carbon. Nitrogen and sulphur are gaseous pollutants. Particulate pollutants may be solid or  liquid  particles, larger particles settle down quickly viz., sand and water droplets whereas small dust particles remain suspended in air for a long time. These are added  into  the  atmosphere  by  the processes of blasting, drilling, crushing, grinding and mixing.

(i) Carbon Dioxide

CO2  content of air has increased by 20% during the last century. CO2 causes nausea and headache. It’s increase in the air may cause green house effect, rise in the atmospheric temperature. This may melt the polar ice resulting in rise in level of oceans and flooding of coastal regions.

(ii) Carbon Monoxide

It is a very poisonous gas and is produced by incomplete combustion of fuel. If inhaled. it combines with hemoglobin and reduces its oxygen-carrying capacity. This leads to laziness, reduced vision  and  death.

(iii) Oxides of Nitrogen

These include NO and NO2, which are released by automobiles and chemical industries as waste gases and also by burning of materials. These are harmful and lower the oxygen carrying capacity  of  blood.

(iv) Oxides of Sulphur

SO2 and SO3 are produced by burning of coal and petroleum and are harmful to buildings, clothing, plants and animals. High concentration of SO2 causes chlorosis (yellowing of leaves), plasmolysis, damage to mucous membrane and metabolic inhibition. SO2 and SO3 react with water to form Sulphuric and sulphurous acids. These may precipitate as rain or snow producing acid rain or acid precipitation.

(v) Photochemical Oxidants

Formed by the photochemical reactions between primary pollutants, viz.  oxides  of nitrogen and hydrocarbons. Nitrogen oxides in the presence of sunlight react with unburnt hydrocarbons to form peroxyacyl nitrate (PAN), Ozone, aldehydes and some other complex organic compounds in the air.

(vi) Hydrocarbons

These are unburnt discharges from incomplete combustion of fuel in automobiles. These form PAN  with  nitrogen  oxides, which  is  highly  toxic.

(vii) Particulate Matter

Industries and automobiles release fine solid and liquid particles into the air. Fly ash and soot from burning of coal, metal dust containing lead, chromium, nickel, cadmium, zinc and mercury from metallurgical processes; cotton dust from textile mills; and pesticides sprayed on crops are examples of particulate pollutants in the air. These are injurious to respiratory tract.

(viii) Aerosols

Aerosols are chemicals released in the air in vapour form. These include fluorocarbon (carbon compound having fluorine) present in emissions from the Jet aeroplanes. Aerosols deplete the ozone layer. Thinning of ozone layer results in more harmful ultraviolet rays reaching the earth, which are harmful to skin, and can lead to skin cancer also.

(ix) Radioactive Substances

These are released by nuclear explosions and explosives. These are extremely harmful for health.

(x) Fluorides

Rocks, soils and. minerals containing fluorides release an extremely toxic gas called hydrogen fluoride on heating. This gas is highly injurious to livestock and cattle.

POLLUTION IN INDIA

India supports a large network of factories and industries. These factories are generally localized in eight or ten large industrial centres. These are also a great source of air as well

water pollution. To be on a safer side  delocalisation  of  industries  is  the  need  of  the  time. This would lead to an even distribution of pollutants and faster degeneration of pollutants. The major pollutants coming out from these industries are -

(i) Industrial  Pollutants.  The  common  air  pollutants  from  industries   are   SO2,   CO, CO2, H2S and hydrocarbons together with dust, smoke and grit. These are produced by the burning of coal and petroleum and by the combustion of lignite at thermal power stations. The chemical industries release HCl, chlorine, nitrogen oxide and oxides of copper, zinc, lead and arsenic.

The fertilizer factories at Gorakhpur and Ahmedabad; the steel industries at Bhilai, Rourkela, Jamshedpur and Durgapur pollute the air with above-said gases.

(ii) Automobile Exhausts. Automobiles run by petrol and diesel produce CO,  nitrogen oxides and hydrocarbons. Hundreds and  thousands  tons  of  hydrocarbons  and  CO are emitted into air daily. Metropolitan cities harbour lakhs  and  crores  of automobiles. Every gallon of petrol consumed by automobiles produces 3 pounds of carbon monoxide and 15 pounds. of nitrogen oxide.

(iii) Ionizing Radiations from Radioactive Substances. Ionizing radiations include alpha, beta particles and the gamma rays etc. These are produced by atomic explosions and testing of atomic weapons.

Effects of Air Pollution

Effect on Plants

(i) SO2 causes  chlorosis  and  also  results  in  the  death  of  cells  and  tissues.

(ii) Fluorides and PAN damage leafy vegetables such as lettuce and spinach.

(iii) Oxides of  nitrogen  and  fluorides  reduce  crop  yield.

(iv) Smog bleaches and blaze foliage of important leafy plants.

(v) Hydrocarbons cause premature yellowing, fall of leave and flower buds, discoloration and curling of sepals and petals.

(vi) Smoke and dust cover the leaf surface and reduce photosynthetic capacity of plants.

(vii) Ozone damages cereals, fruits, and cotton crop.

Effect on Man

The effect of pollutants on animals and man are as follows-

(i) Ozone causes dryness of mucous membranes, changes eye vision, causes headache, pulmonary congestion and oedema.

(ii) Ozone has been reported to produce chromosomal aberrations.

(iii) SO2 causes drying of mouth, scratchy throat, smarting eyes and disorders  of respiratory tract.

(iv) SO3, CO and NO2 diffuse into  blood  stream  and  reduce  oxygen  transport.  CO damages cardiovascular system. Hydrocarbons and other pollutants  act,  as carcinogens and lead to different cancers.

(v) Cotton dust  leads  to  respiratory  disorders  e.g.  bronchitis  and  asthma.

(vi) Smoking of  tobacco  causes  cancerous  growth  in  lungs.

Change in Climate

CO2 content of air is increasing due to deforestation and combustion of fuel. This increase is affecting the composition and balance of gases in the atmosphere. Increase in CO2 concentration may increase the atmospheric temperature, producing green house effect A rise of global temperature by more than 2-3 degrees may melt glaciers and polar ice. This would lead to a rise in ocean level and consequent flooding and submergence of coastal areas. Rainfall pattern may also change, affecting agricultural output in various regions of’ the world. Aerosols deplete the ozone layer in the stratosphere. Thinning of ozone layer would permit more of the harmful ultraviolet rays to reach the earth. This may cause, sunburn, blindness and inactivation of proteins, RNA, DNA and plant pigments.

Aesthetic Loss

Dust and smoke spoils the beauty of nature. Especially the mountain environments, which serve as a great attraction for tourists. Foul odours emitted by industries, automobiles, dirty drains and garbage heaps in cities are a great nuisance.

Control of Air Pollution

Following measures  have  been  suggested  to  control  air  pollution-

(i) Some gases, which are more soluble in a particular liquid than air, for example, ammonia in water, can be separated by dissolving in it

(ii) Particles larger than 50 mm are separated in gravity settling tanks. Using cyclone collectors or electrostatic precipitators separates fine particles.

(iii) The height of chimneys should .be increased to the highest possible level to reduce pollution at the ground level.

(iv) SO2 pollution can be controlled by extracting sulphur from the fuel before use.

(v) Pollution control  laws  should  be  enforced  strictly.

(vi) Trees should be planted on the roadside, riverbanks, parks and’ open places as they keep the environment fresh.

(vii) Population growth,  which  is  the  main  cause  of  pollution  should  be  checked.

(viii) Nuclear explosions  should  be  restricted.

Water Pollution

Water is extremely essential for life, this common fact is known to all. It is required to meet our basic needs in day to day life viz., cooking, drinking, bathing, disposal of sewage, irrigation, generating electricity in power plants, cooling and manufacturing different products in industries and the disposal of industrial wastes. During all these processes the undesirable substances are added to the water resources to a great extent. This alters the basic chemistry of water in rivers and streams.

Sources of Water Pollution

(i) Domestic sewage

This includes household’s wastes like food wastes, synthetic detergents used for washing clothes and cleaning bathrooms and  latrines and water based paints.

(ii) Industrial effluents

The industrial wastes are discharged in the adjoining rivers and streams through flush lines of factories. The textiles, sugar and fertilizers factories, oil refineries, drugs manufacture, rubber, and rayon fibers, the paper industries and the chemical factories all produce Chemical pollution.

(iii) Agricultural source

Increased use of fertilizers has become essential for high yielding crop plants. Excess of nitrates used as fertilizers seep into ground water is carried into lakes and pond. On entering the drinking water supply system these create several health problems.

(iv) Pesticides

These include insecticides, fungicides, nematicides, rodenticides, herbicides and soil fumigants. These contain chlorinated hydrocarbons, organophosphates, metallic salts, carbonates, acetic acid derivatives etc. many pesticides are non-degradable. They pass through the food chains and accumulate in fatty tissues thus causing several health hazards.

(v) Thermal pollution

Power plants and nuclear power stations are the main sources of thermal pollution of water where water is used for cooling and becomes hot. The hot water on entering the main water body raises its temperature, which kills fishes and other aquatic animals and increases the rate of respiration in aquatic plants.

(vi) Pathogenic organisms

Sewage and domestic waste from houses introduces pathogenic organisms viz., protozoa, worms-eggs and bacteria into water. This contaminated water if consumed causes jaundice, typhoid, dysentery, cholera, tuberculosis etc.

(vii) Mineral oils

Oil from oil spills and washings of automobiles finds  way  into  river  water  through sewers.

(viii) Underground water pollution

Underground water particularly in cities and industrial areas is no more pure and safe. The sources of underground water pollution are sewage, seepage, pits, industrial effluents, septic tanks, fertilizers and pesticides, garbage etc.

(ix) Marine water pollution

River and stream network sources of water ultimately  end  up  ocean  and  seas.  Thus, these acts as the  sink  of  all  natural  and  man-made  water  based  pollutants.  The  main sources of oceanic pollution are discharges of oil, greases, petroleum products, detergents, sewage and garbage including radioactive wastes.

Effect of Water Pollutants

The main effects of water pollutants are:

1. Compounds of mercury, arsenic and lead are poisonous and chemically harmful as they even affect water treatment plants e.g. organic sulphur compounds interfere with nitrification.

2. Mercury when dissolved in water is absorbed by aquatic plants and enters the food chain. Lead impairs metabolism and brings  about  congenital  deformities,  anaemia etc.

3. Cadmium damages kidneys and liver.

4. Inorganic nitrates and phosphates promote growth of oxygen-consuming algae, which result  in the death of  fishes  and other  aquatic animals.

5. Presence of dyes and compounds in the discharged water changes the colour  of water.

6. Soap, detergents and, alkalis result in foam formation.

7. Industrial effluents containing iron, free chlorine, phenol, manganese, oils, hydrocarbons, ammonia, algae and microorganisms impair the taste and odours of water.

8. The nitrates and phosphates dissolved in water accelerate the growth of microorganisms, which consume much of the dissolved oxygen depriving fish  and other aquatic life (Eutrophication).

9. Biomagnifications is the increase of toxic materials at each tropic level of a food chain.

For example, DDT after reaching a water system is absorbed by the microorganisms on which smaller fishes feed. From them, DDT reaches the  carnivorous  animals.  Since  bigger fishes consume more food, large amounts of DDT accumulates in their body.

CONTROL OF WATER POLLUTION

(i) Separate ponds and tanks to be used for cattle and animals.

(ii) Use of pesticides, insecticides and fertilizers should be done judiciously. Rapid biodegradable substitutes for pesticides should be employed.

(iii) In towns where sewage facilities are not available, septic tanks should be made in the houses.

(iv) Rivers and lakes should not be used for bathing or washing as it contaminates water. .

(v) Domestic sewage and industrial wastes should be treated before discharging them into drains.

Treatment of waste Water

Domestic sewage and industrial wastes should be properly treated before these are drained in the mainstream water. Treatment involves the following two steps:

(i) Sewage treatment

It involves  following  steps:

Primary treatment. It involves physical processing of sedimentation, flotation and filtration where sewage water is passed through screens to remove larger particles and then through grinding mechanism to reduce the larger particles to smaller size. The sewage is finally passed through settling tanks to remove suspended impurities.

Secondary treatment. Sewage obtained after primary treatment is sent to aeration tank where it is mixed with air and sludge laden with bacteria and algae. The algae provide oxygen to the bacteria and decompose organic matter into simple compounds. Chlorination is finally done to remove bacteria.

Tertiary treatment. In the third and last step water is passed through ion exchangers to remove dissolved salts.

(ii) Treatment of industrial effluents

Treatment of industrial effluents involves neutralization of acids and bases, removal of toxic compounds, coagulation  of  colloidal  impurities,  precipitation  of  metallic  compounds and reducing the temperature of effluents to decrease thermal pollution.

SOIL POLLUTION

Soil Pollution

Like water and air,  soil  is  also  equally  important  for  living  organisms.  It  supports plants on which. all other living organisms depend. The process of soil formation is so slow that the soil may be regarded as a non-renewable source. Therefore, the study and control of soil pollution is important. Any substance that reduces soil productivity is called soil pollutant.

Sources of Soil Pollution

There are several materials, which adversely affect physical, chemical and biological properties of the soil and thus reduce its productivity. These are

1. Chemicals present in industrial waste.

2. Pesticides and insecticides that are sprayed on crops. .

3. Fertilizers and manures that are added to the soil to increase the crop yield.

Effect of Soil Pollutants

Chemicals and pesticides affect the structure and fertility of soil by killing the soil microorganisms. Pesticides are absorbed by the plants and then transferred to other organism. Hence, they affected food chains and food webs. Excretory products of livestock and human beings used as manure pollute the soil besides giving high yield. The faulty sanitation and unhygienic practices of the people add to the soil pollution. Pathogens present in the wastes and excreta contaminate the soil and vegetable crops causing diseases  in  man  and domesticated animals.

Types of Soil Pollution

It is of the following types-

(i) Positive soil pollution

Reduction in the productivity of soil due to the addition of undesirable substances like pesticides, herbicides, fertilisers, etc. is called positive pollution. These pollutants have cumulative effect and  kill the soil organisms.

(ii) Negative soil pollution

It is caused by the removal 01 useful components from soil by erosion, deforestation and improper methods of agriculture.

Salination of Soil

Increase in the concentration of soluble salts is called salination. This adversely affects the quality and productivity of soil. It takes place in two ways: accumulation of salts dissolved in irrigation water on the soil surface due to intensive farming and poor drainage,  and deposition of salts as white crust during summer months drawn by capillary action from the lower surface to the top surface.

Control of Soil Pollution

Various measure to control soil pollution are-

1. Transfer stations for bulk shifting of refuse should be constructed in cities and big towns.

2. Pneumatic pipes  should  be  laid  for  collecting  and  disposing  wastes.

3. Materials like paper, glass and plastics can be recycled.

4. Metals should  be  recovered  from  scrap  and  disposed  materials.

5. Use of chemical fertilizers should be reduced by the use of bio fertilizers and manures.

6. Use of pesticides can be reduced by adopting biological control of pests.

7. Use of cattle dung and agricultural wastes in biogas plants should be encouraged.

8. Deforestation can  check  soil  erosion  to  a  great  extent.

Land Degradation

Besides pollution, land and soil face several other problems. Removal of topsoil is called soil erosion. Soil erosion factors are water, wind, ocean, waves and glaciers, felling of trees, overgrazing by cattle, over-cropping etc. Erosion occurs both in wet and dry regions. It leads to floods.

Soil Erosion in India

Soil erosion is a worldwide phenomenon, but it is especially high in Central Africa, China, India, Nepal, Australia, Spain, USA and USSR. India loses about 40,000 hectares of land every year as an effect of wind and water erosion. Damage to the topsoil is 18.5% of the total world’s loss. This is due to overgrazing by livestock. The population of livestock in India is the highest in the world. Overgrazing damages the topsoil, which reduces soil fertility.

(i) Deforestation of overgrazing

Over-grazing is the main cause of soil erosion in India. Roots of grasses act as binding material and keep the soil intact, which upon grazing are destroyed.

(ii) Desertification

Loss of soil productivity by erosion of top soil results in the formation of deserts. Deserts are spreading in all continents. Desertification takes place by shifting of sand dunes

by wind and .over-grazing. That desert in India is spreading at the rate of 12,000 hectares of land every year.

(iii) Shifting cultivation

Tribal communities follow the practice of cutting down trees and setting them on fire and then raising the crops on the resulting ash. This is called Jhuming in northeastern India. It is harmful if the Jhuming cycles are longer than ten years but short cycles destroy forests and cause soil erosion. e.g. Asia and Africa. .

(iv) Developmental activities

Large areas of fertile and productive croplands, woodlands and grasslands are lost to various developmental activities such as rapid urbanization, building of airports, industries, railways, roads, mining and construction of dams.

Control of Land Degradation

Following ways  can  control  Land  degradation

1. Restoration of forests and grass cover can help in prevention of soil  erosion  and floods.

2. By replacing shifting cultivation with crop rotation, mixed cropping or plantation cropping. Providing adequate drainage to irrigated and flood-prone lands can prevent salinity.

3. Desertification can be controlled by spread of appropriate plant  species  and  by raising trees as wind breaks.

Noise Pollution

Noise can be defined as unwanted/unpleasant sound. So noise pollution  is  unwanted sound dumped into the atmosphere  without  regard  to  the  adverse  effects  it  may  have.  In our country urbanization and industrialization have become twin problems. Cities and towns have sprouted up where industries are concentrated. Lack of town’ planning had led to residential, commercial and industrial areas being  mixed  up.  Houses,  schools  and  hospitals are situated near industries. All  the  boons  of  industrialization  and  civilization  such  as motors, horns, heavy and light machinery, work and movement, blaring radios, supersonic aeroplanes have become disturbing and irritant. Our ears can hear ordinary conversation between 30-60 decibels. Modern conversation has a noise  value  of  60  decibels.  A  decibel value greater than 80 decibels causes noise pollution. Noise becomes troublesome above 140 decibels.

Effect of Noise Pollution

1. Constant noise  affects  a  man  physically  and  mentally.  Physical  effects  include blood vessels to contract, skin to become pale, muscles to constrict and rise in blood pressure leading to tension and nervousness.

2. High intensity sound emitted by industrial plants, bottling machines, supersonic aircrafts, when continued for long periods of time not only disturbs but also permanently damages hearing.

3. Offices, industries and crowded places where constant noise prevails can produce temper tantrums, headaches, fatigue and nausea. .

4. Loud and sudden noise affect the brain. Intermittent noise leads higher incidence of psychiatric illness and also a danger to health of pregnant mothers and small infants.

5. Noise has harmful effects on nonliving materials too, e.g. cracks develop under the stress of explosive sound.

Control of Noise Pollution

Following methods  can control noise  pollution:

1. Limited use  of  loudspeakers  and  amplifiers.

2. Excursing control  over  noise  producing  vehicles.

3. Industrial workers should be provided with ear plugs.

4. Delocalisation of noisy industries far away from dwelling units.

5. Within a radius of 10 miles of airport, no buildings or factories should be allowed.

6. Plants and trees should be planted all around the hospitals, libraries and schools and colleges.

7. Personal protection against noise can be taken by using, cotton plugs in the ear.

Radiation

The radiations from  the  atomic  blasts  cause  several  health  hazards.  The  radiations carry high energy and remove electrons from atoms and attach them to other atoms producing positive and negative ion pairs. Hence, they are known as ionizing radiations. The ionization property of these radiations proves to be highly injurious to the protoplasm. The ionizing radiations of ecological concern are classified as follows:

Corpuscular Radiations

These consist of streams of atomic or subatomic particles, which transfer their energy to the matter they strike.

(i) Alpha particles

These particles are large and travel  few  centimeters  in  the  air.  These  cause  large amount of local ionization.

(ii) Beta particles

These are small particles characterized by having high velocities. They can travel a few meters in space. These are capable of entering into the tissues for few centimeters.

Since alpha and beta particles have low penetration power they can produce  harmful effects only when absorbed, ingested or deposited in or near living tissues.

(iii) Electromagnetic radiations

Electromagnetic radiations include waves of shorter wavelengths. These are capable of traveling long distances and can readily penetrate the living tissue. These include gamma rays. These can penetrate and produce effect even without being taken inside.

Other Types of Radiations

Besides radioactive radiations, some other radiations are also present in the atmosphere.

(i) Neutrons

These are large uncharged particles, which do not  cause  radiation  by  themselves,  but they produce radioactivity in non-radioactive materials through which they pass.

(ii) X-rays

These are electromagnetic waves very similar to gamma  rays,  but  originate  from  the outer electron shell of radioactive substances, which are not dispersed in nature.

(iii) Cosmic rays

These are radiations from the outer space, which contain alpha and beta particles together with gamma rays.

Sources of Radiations

The radiations are produced from the radioactive elements, which are known as radionuclides or radioactive isotopes, e.g. Uranium. Radium, Thorium, and Carbon-14. These contribute to background radiation. But isotopes of certain metabolically important elements like Carbon-14, Cobalt-60, Calcium 45, Iodine-131, Phosphorus-32, etc. are not ecologically harmful but are used as tracers. The third category of radionuclides comprises of fission products of uranium and certain other elements. These are cesium, strontium, and plutonium etc.

Biological Effects of Radiation

The effects of radiation have revealed that acute doses are found to be deleterious and may kill  the  organisms,  whereas  the  increase  in  radiation  in  biological  environment  leads to different kinds of mutations. The effects  of  Cobalt-60  or  Cesium-137  gamma  radiations have now been studied on communities and on ecosystems at different places. The research concludes that Irradiations eliminate varieties in species. The sensitivity of cells, tissues and organisms to radiation varies. The cells with larger chromosomes are more sensitive. Herbaceous communities and early stages of succession are resistant than the mature forest.

Nuclear Fall Outs or Radioactive Fall Outs

The atomic blasts not only produce the local ionizing radiations at that time but the radioisotopes produced as a result of explosion enter the atmosphere and continue to fallout gradually over broad geographic areas for a very long  time.  These  are  known  as  nuclear fallout or radioactive fallout. These are dangerous for life as they also produce ionizing radiations.

Biological Effects of Fall outs

The fallout of radionuclides combines with various metals and dust and from colloidal suspension combines with organic compounds to form complexes. The smaller particles of radionuclides adhere tightly to the leaves of plants and produce radiation damage to leaf tissue besides entering the tissues also. Through grazing animals these enter the food chain directly at the primary consumers level. Radionuclides, which combine with organic substances, enter the food chain through producer tropic level. Therefore, the radionuclides fall out manages to enter the body of all living organisms. Radioactive Strontium-90 poses a health hazard in human beings and other higher vertebrates. It continues to deposit in the bones and causes bone cancer and leukemia. Radioactive Cesium-137 is known to cause

irreversible genetic changes in different organisms. The fallout radiations do cause changes in the genetic constitution of organisms, resulting in gene mutations and chromosomal aberrations. Their considerable, doses may kill, cripple and alter the animals and plants in the areas.

Control of Radiation Pollution

Following measures can help in controlling the radioactive pollution:

(i) Workers in nuclear plants should be provided with nuclear gadgets and safety measures against accidents.

(ii) Leakage of radioactive elements from nuclear reactors, laboratories,  transport, careless handling  and use  of radioactive  fuels should  be checked.

(iii) Level of  radiation  pollution  should  be  monitored  regularly  in  risk  areas.

(iv) Disposal of  radioactive  wastes  deserves  special  attention.

Case studies

Hiroshima and Nagasaki Episode

The tale of Hiroshima and Nagasaki is a painful experience. It is for the first time that an atomic bomb has been exploded over human population. The incident took place on August 6,1945 at 8:15 a.m. The bomb with an approximate temperature of around 100 million 0°C was exploded on a fine morning in Hiroshima (Japan). The temperature of the city hiked like anything, almost like an oven. After three days, Nagasaki too suffered the ravages of a nuclear attack. More than 1,00,000 people were reported to die just after the event took place. Since radiations from nuclear elements remain active even after, the generations to follow up also suffered from various diseases. Even the babies in the mother’s womb were affected and a few perished. Blindness, deafness, skin diseases and cancers, distortion of bones and other parts became the fortune of human civilization.

Chernobyl Accident

This incident took place in Ukraine on April 26, 1986. There was a Chernobyl nuclear power plant in Ukraine after which the event has been named. Approximately four million people had been reported to suffer from the accident. The accident contaminated neighboring environment up to several kilometers. The sites were evacuated and resettlement was done for the affected people. The radiations released affected ground water and surface waters, affecting large areas of Europe. 131 Iodine and 137 Cesium are the most dangerous amongst the 20-odd radioactive elements released during Chernobyl disaster. As per the Soviet Health Ministry, 31-persons died shortly after the disaster. Of the 276,614 people who worked for rehabilitation and cleaning operations, a total of 1065 died by the end of 1990.

Marine Pollution

All river drainages end up in the seas. On the way to sea, rivers carry large amounts of sewage, garbage, and agricultural discharge, biocides, including heavy metals. Besides this discharge of oils and petroleum products and dumping of radionuclides waste into sea also cause marine pollution. Huge quantity of plastic is being added to sea and oceans. Over 50 million lb plastic packing material is being dumped in sea of commercial fleets. Many marine birds ingest plastic that causes gastro-intestinal disorders. The chemical principle in

PCBs causes more damage as thinning of eggshell and tissue damage of egg. Radionuclide waste in sea includes Sr-90, Cs-137, Pu-239, and And Pu-240.

The pollutants in sea may become dispersed by turbulence and ocean currents and finally becomes a part of food chain. Bioaccumulation in food chain may result into loss of species diversity. The pollution in Baltic sea along the coast of Finland, took place largely from sewage and effluents from wood industries. This pollution effect brought changes. in species diversity in the bottom fauna. In less polluted water there was rich species diversity, which tended to decrease with increasing pollution load. In heavily polluted areas, macroscopic benthic animals were absent, but chirognomy larvae occurred at the bottom. In marine water the most serious pollutant is oil. Spill of oil or petroleum products due to accidents/ deliberate discharge of oil polluted waste brings about pollution. About 285 million gallons of oil are spilled each year into ocean, mostly from transport tankers. Oil pollution causes damage to marine fauna and flora including algae, fish, birds, and invertebrates. About 50,000 to 2,50,000 birds are killed every year by oil. The oil is soaked in feathers, displacing the air and thus interferes with buoyancy and maintenance of body temperature. Hydrocarbons and benzpyrene accumulate in food chain and consumption of fish by man may cause cancer. Detergents used to clean up the spill are also harmful to marine life.

Thermal Pollution

The increase in water temperature by industrial units such as steel and iron factories, electric powerhouses and atomic power plants may be called as thermal pollution. Some of the industries generate their own power supply where water is used to cool the generators. This hot water is released into the main stream, causing a warming trend of surface waters. If the drainage is poorly flushed, a permanent increase in the temperature may result.

Many  organisms  are  killed  instantly  by  the  hot  water  resulting  into  a  high  mortality. It may  bring  other  disturbance  in  the  ecosystem.  The  eggs  of  fish  may  hatch  early  or  fail to hatch at all. It may change the diurnal and seasonal behaviour and metabolic responses of organisms” It may lead to unplanned migration of aquatic animals. Macrophysics population may also be changed. As  temperature  is  an  important  limiting  factor,  serious  changes  may be brought  about  even  by  a  slight  increase  in  temperature  in  a  population.  Heat  stress (5-1 one above the normal growing temperature of organism) induces expression of specific gene families called heat shock genes, which lead to the synthesis of a new set of proteins called heat shock proteins. Heat shock proteins have been found in every organism from unicellular prokaryotes to multicultural organisms including Homo sapiens.  Heat  Shock Proteins synthesis lead to acquired thermo tolerance, i.e. the ability of  an  organism  to withstand a normally lethal temperature. Thermo tolerant genotypes show adaptations at various levels of organization  besides  showing  qualitative  and  quantitative  differences  in heat shock  proteins as  compared to  the thermo sensitive  genotypes.

Solid Waste Management

Environmental problems also include solid waste disposal. At all levels of development human beings produce domestic  wastes.  These  comprises  of  kitchen  wastes,  ashes  from fires, broken utensils and worn-out clothing. The industrial revolution leads  to  the concentration of people in urban areas with very high population density. This resulted in addition of new sources of wastes from shops, institutions and factories. In developed countries

services for the regular removal of domestic and trade wastes have been in operation for last many years.

Many changes have taken place in our society. The character of the wastes has altered with rising living standards, changes  in  retail  distribution  methods  and  fuel  technology. Grave environmental concerns have come up with rise in construction of new buildings, supermarkets, and industrial wastes of many kinds. In the industrialized countries, therefore, basic health and environmental problems have been solved in the storage and collection of solid wastes, although major problems remain in regard to resource recovery and disposal. The technology of wastes handling is now highly  developed.  The  substantial  sectors  of industry are engaged in the production  of  equipment  with  regard  to  removal  of  wastes. Many institutions  give  technical  training  and  support.  However  developing  nations  like India are facing the problems of urbanization with high population densities. The developing countries are aware of the importance of avoiding the environmental pollution. The quality of urban environment is a matter of growing concern and the importance of solid wastes management is increasingly being recognized.

Sources and Characteristics

Solid wastes generally refer to describe non-liquid waste materials arising from domestic, trade, commercial, industrial, agriculture and mining activities and from the public services. Disposal of sludge’s (liquid waste) of some kind fall within the scope of  solid  waste management. These arise primarily from industrial  sources  and  from  sewage  treatment plants. Solid wastes comprise countless different materials;  dust,  food  wastes,  packaging  in the form of paper, metals, plastics or glass, discarded clothing and furnishing, garden wastes and hazardous and radioactive wastes. The method and capacity of storage, the correct type of collection vehicle, the optimum size of crew and the frequency of collection depend mainly on volume and density. Just as solid wastes comprise a vast number of materials, they arise from a multitude of separate sources as well as many kilometers of streets upon which solid wastes accumulate. Thus, the four main aspects of solid wastes management are: (i) storage at or  near  the  point  of  generation,  (ii)  collection,  (iii)  street  cleansing, (iv)  disposal.

The main constituents of solid wastes are similar throughout the world,  but  the proportions vary widely. As personal income rises, paper increases, kitchen wastes decline, metals and glass increase, total weight generated rises and the density of the wastes declines. Clearly, the amount of work involved in refuse collection  depends  upon  the  weight  and volume of wastes generated and the number of collection points from which the wastes have to be removed.

Health and environmental implications

Improper handling of solid wastes results in increased potential risks to health and to the environment both. Direct  health  risks  concern  mainly  the  workers  in  this  field,  who need to be protected, as far as possible,  from  skin  contact  with  wastes.  For  the  general public, the main risks to health are indirect and arise from the breeding of disease vectors, primarily flies and rats. More serious, however, and often unrecognized, is the transfer of pollution to water, which occurs when the leach ate from a refuse dump enters surface water or wastes, either in the open air, or in plants that lack effective treatment facilities for the gaseous effluents. Traffic accidents can result from wastes accumulated and dispersed on to

streets and roads. They have caused death and injury to people  in  the  surrounding  areas. There also persists the specific danger  of  the  concentration  of  heavy  metals  in  the  food chain. These metals can be taken up  by  the  plants  growing  on  land  on  which  sludge  has been deposited, creating risks to the animals which  graze  and  the  humans  who  consume these animals.

Economic implications

Labour and transport absorb the major part of the operating cost of solid wastes management services. The level of mechanization that should be adopted for solid wastes management systems relates directly to the cost of labour, as compared to that of plant and energy. There is not much variation, worldwide, in energy or mechanical plant costs, but there is wide variation in the range of labour costs. Thus, there are no universally applicable solid wastes management systems. Every country must evolve indigenous technology based on the quantity and character of the wastes, the level of national wealth, wage rates, equipment, manufacturing capacity, energy costs etc. It is necessary to deploy a complete set of technical skills, which derive from several professional disciplines. These include civil and mechanical engineering, chemical engineering, transport organization, land use planning and economics.

Refuse Collection

A refuse collection service requires vehicles and labour. For their efficient development, three components are basic:

(1) Travel to and from the work area,

(2) The collection process, and

(3) The delivery  process.

The use of large, widely spaced communal storage sites is usually a failure because the demand placed on the householder goes beyond his willingness to cooperate. Communal storage points should, therefore, be at frequent intervals, Madras and Bangalore provide fixed concrete containers. They are fairly successful because they place reasonable and acceptable duty on the residents, thus very little domestic waste is thrown in the street.

In another system of block collection, a collection vehicle travels a regular route at prescribed intervals, usually every two days or every three days, and it stops at every street intersection, where a bell is rung. At this signal the residents of all the streets leading from that intersection bring their wastes containers to the vehicle and hand them to the crew to be emptied. A crew of one or two men is adequate in number, as they do not need to leave the vehicle.

Sanitary Landfill Disposal

Land disposal (burying of wastes) is the only approved method of disposal, which is performed at a single site. Incineration, composting, and salvage are either a form of refuse handling or processing. They are not complete methods of disposal, and they require disposal of residue. Sanitary landfill can be defined as the use of solid wastes for land-reclamation, a typical example being the restoration, by filling to the original level of man made surface dereliction such as a disused surface, mineral excavation. Solid wastes may also be used to improve natural features by raising the level of low-lying land to enable it to be used or

cultivation or industrial development. Thus, sanitary land filling has two essential features, which differentiate it from crude dumping:

(i) Only sites  that  will  be  improved  not  degraded,  by  a  change  of  level  are  selected.

(ii) Simple engineering techniques are used to control the manner in which the wastes are deposited,  so that  dangers to  public health  and the  environment are  avoided.

Unfortunately most of the world’s wastes are disposed off by uncontrolled dumping which blights the land for any future use and causes serious risks of water pollution and vector breeding. Very few cities operate sanitary land filling to standards, which totally control health and environmental dangers; most of those that do are in the industrialized countries.

Control of Hazards

(i) Control over pathogens is dependent upon a rigorous policy of covering the wastes soon after deposit. This serves both to isolate the wastes  and  to  retain  the  heat, which is quickly generated during aerobic decomposition.

(ii) The main source of insects will be the eggs of flies. Which have been deposited in the wastes before they arrive at the site. Most of these will be buried deep in the wastes and will  succumb to the temperature increase.

(iii) Fire at a sanitary landfill can arise from innumerable causes, hot ashes in a vehicle delivering wastes: a cigarette thrown by a worker; the sun’s ray though a fragment of glass on the surface. With some kinds of wastes the consequence of fire may be very serious and underground fires have been known that ultimately caused the collapse of the surface into voids caused by the fire.

(iv) The pollution of static water, ditches,  river  or  the  sea  occurs  when  a  sanitary landfill adjoins a body of water. The normal source of the leach ate causing this pollution is rain falling on the surface.

Incineration

Open burning, barrel burning, and other related uncontrolled forms of burning have a long history of use. Many liquid wastes and pathological wastes are best disposed of by incineration. Originally, solid waste incineration was practiced to reduce the quantity of refuse or disposal. After it was proven that heat could destroy most pathogens, incinerators were used in hospitals for destruction of pathological wastes. With few exceptions, incinerators are not “good neighbors,” and the environmental nuisances of dust. Noise and air pollution have provoked communities to an anti-incinerator philosophy. To overcome this negative community feeling is going to require that incineration prove its worth and that imagination be used in the design of future units. Incineration of solid wastes yields the highest percent of volume reduction except for Pyrolysis. Unlike a sanitary landfill, incineration of solid wastes can be performed on the premises of apartments, supermarkets, departments’ stores, and similar establishments.

Composting

Composting involves the biological stabilization of solid matter either under aerobic or anaerobic conditions. The end product of composing is an organic material, which could have beneficial value as a soil conditioner or plant mulch. In addition to producing a modified

solid waste material, which can be useful in land reclamation, composting does yield a volume reduction of solid waste by about 40-60% of the compost able fraction pyrolysis

Pyrolysis is a thermal process where oxidation of the organic fraction is not allowed to occur. Instead, the organic matter is evolved from the refuse with heat,  leaving  an  ash consisting mostly of carbon and any inorganic matter, e.g. metal and glass are not removed before Pyrolysis. Some of the gases, which have been volatized, are condensed while the remainder is burned to supply the heat (energy) needed to pyrolyze the material.  Since oxidation is prevented, the Pyrolysis process must be performed in an atmosphere of argon, helium or nitrogen.

Role of an Individual in Prevention of Pollution

Which are the most viable, efficient and economical ways to eliminate pollution problems? We very often see people blaming public and government sectors to control pollution through controlling market mechanisms and government blaming people to avoid and check pollution. Who would control whom? Many ecologists and environmental scientists believe in that pollution problems can be overcome by using market mechanisms to reduce pollution rather than rigid rules and regulations. However, on the other hand man should identify and gear up his own potential to curb down pollution. Man could achieve this by identifying his own role at individual level in prevention of pollution. This is possible through environmental awareness, education and enlightenment.

Ways and means by which pollution problems can be greatly reduced at individual level

are:

1. Masses at personal level should determine to consume optimum level of resources, which would lead a comfortable life. Because excessive resource consumption is in someway related to pollution problems and hazards (natural  and  anthropogenic both).

2. Waste disposal at personal level should be optimally reduced as waste destruction by any means causes pollution.

3. Maintenance of vehicles should remain proper as to avoid introduction of harmful gases and other pollutants in to the atmosphere.

4. Generators and other household gadgets that add to pollution of environment should be kept well maintained.

5. Use of chemical fertilizers should be limited as to avoid water pollution e.g. DDT

6. Timely disposal of waste to prevent decomposition of household refuge as to check foul odours and spread of disease by insects, flies and other pathogenic bacteria.

7. Industrialists should check for proper disposal of treated water from factory units as to avoid thermal pollution of water bodies. They should also deploy a water treatment plant to prevent the flow of hazardous material.

8. Service centres of vehicles should minimize the disposal of organic solvents into the main drains.

9. Music lovers should listen and operate their music systems at optimum levels as to avoid noise pollution.

Disaster Management

Loss of life and property due to natural disasters like tropical cyclones, floods, droughts, tornadoes, earthquakes, volcanic eruptions etc,  is  very  large.  Fortunately  warning  facilities are available today and by mitigation measures, loss of lives and properties can be minimized. National Meteorological Services of the world to provide warnings to the public for some of the weather related natural disasters. It is not possible to forecast  a  long  period  ahead precisely when and where a dangerous natural phenomenon will take place. While natural disasters cannot be prevented, taking proper long-term and short-term disaster mitigation measures can minimize the loss of life and property.

Some common disasters known to occur in our country are as under:

Floods

Floods are defined as a relatively high flow of water discharged from river and stream network, which sets the riverbank margins to  overflow  and  lead  to  the  inundation  of  low land areas surrounding the riverbed. It is essentially  a  physical  phenomenon.  Floods  arise from abnormally heavy  rains,  dam  failures,  snow  melts,  river  blockages.  Flood  disasters rank second only to droughts in the total number of people affected worldwide.

Types of Floods

Floods can  be  classified  into  three  categories  as  under:

(i) River floods

Rivers get charged due to heavy rains  over  large  catchments  areas  or  by  melting  of snow or sometimes both especially in the mountainous tracts. The floods take place in river systems with tributaries that may drain into large geographic areas and encompass many independent river basins. Amount of flooding depends on moisture  in  the  soil,  vegetation cover, and depth of snow and size of catchments basin.

(ii) Coastal floods

Coastal flooding is associated with tropical cyclones/ harsh winds arising at the ocean surface. Coastal floods are often aggravated by wind induced storm surges along the coastline. Sea and ocean ‘water floods the inland coasts affecting kilometers of tracts. Ocean tides, storm surges or tsunamis play a definite role. Prolonged and indefinite rains in the rainy season marked from June-September results in extreme flood in coastal river basins.

(iii) Flash floods

These floods occur within six’ hours of the beginning of rainfall and; are characterized with rising clouds, thunderstorms and tropical cyclones. These result from runoff from a torrential downpour, particularly if the catchments slope is unable to absorb and hold a significant part of water. Other causes of flash floods include dam failure, sudden break up of glaciers etc. These offer potential threats in the areas where the terrain is steep, surface runoff is high, water flows through canyons and where severe rainstorms are likely.

General Characteristics of Floods

1. Man made structures and forest vegetation exhibits different levels of tolerance towards effects of  floods.

2. Intensity of  damage  is  governed  by  the  time  interval  of  standing  floodwaters.

3. High velocity  of  running  water  may  uproot  or  weaken  foundations  of  buildings.

4. Rate of rise and discharge of a river is important as a basis for flood control.

5. Frequency of occurrence estimated over a length of  period  would  determine  the kind of activities the flood plain should be put to.

6. Generally the rainy season is characterized by the floods during which agricultural economy suffers a huge loss.

Effects of Floods

1. Rising water, erosion and the force damages the residential and commercial building. They are dangerous for villages lying in the coastal areas as it  sweeps  away everything, which  comes  into  its  path.  In  mountainous  areas  it  is  the  chief  cause of landslides.

2. Fisherman, local people, cattle,  animals  and  vegetation  suffer  a  great  loss  of  life and property. Most of the deaths are reported to be from drowning.

3. Fresh water supplies by all sources are nearly destroyed and contaminated hence the areas falling under its impact bear a great risk of suffering from water borne diseases.

4. The destruction of food and fodder crops result in acute food shortage.

5. Floods also  make  soil  infertile,  as  the  topsoil  is  lost  due  to  erosional  activity.

6. Floods are  also  known  to  preserve,  wetlands  and  recharge  ground  water.

Flood Control

1. Depth and width of the riverbed could be increased as its capacity to carry larger loads increases  manifold and thus  reduce the area  of the flood  plain.

2. A network of canals can be  established  from  the  river  systems,  which  generally leads to floods. This would  also  benefit  the  agricultural  economy/  section.  Care must be taken in the design and construction because of the possible environmental impact and necessary safety features.

3. Reservoirs should be made for storing floodwater and releasing them at manageable rates. This would require careful engineering. Dams, and reservoirs would further lead to generation of resources.

4. Newly constructed residential as well commercial buildings should have foundations, which are strong enough to respond to flood conditions.

5. Rivers and streambeds should be  stabilized  with  stone,  masonry  or  vegetation  at the banks. This should strictly be followed where rivers pass through cities, specially near bridges.

Post Disaster Requirements

The initial response to flooding authorities/community should include: Search  and  Rescue  operations, water provision,

Medical assistance, Disaster epidemiological surveillance assessment, food and

and temporary shelter.

The secondary  response  should  include:

Reconstruction  of  houses, equipment and tools, supply Creation  of  employment, of animals, and assist with Assistance  to  farmers, recovery of  small business

Distribution of farm and fisheries.

Flood Problem In India

The nature of flood problem varies from one river system to another. Two great river systems are discussed below considering the flood problems in India:

Brahmputra River

The main problem of flooding in the northeastern region arises from the Brahmaputra river and its tributaries. The river in monsoon season overflows its banks and causes a great damage to life and property both. Several times it has affected Kaziranga wildlife sanctuary where rhinoceros population died due to rising floods. In recent years, the erosion along the banks of the Brahmputra has assumed serious proportions. The rivers also carry considerable amount of silt and have a tendency to change its course.

Ganga River System

In  this  region  the  northern  tributaries  of  the  Ganga,  namely  the  Rapti,  the  Sharada, the Ghaghra and the Gandak cause extensive flooding along their banks. Drainage congestion is confined to the northwestern parts of U.P., Meerut, Mathura  and  Agra  suffers  the  most. Bihar suffers a considerable amount of damage due to the flooding of the Burhi Gandak, the Baghirati, the Kamla Balan, the Kosi and the Mahananda. In addition to the crop submergence the area experiences  traffic  dislocation  also.  In  the  Bengal  region  Baghirati,  the  Ajoy  and the Damodar cause extensive flooding.  Here  the  tidal  effect  of  Bay  of  Bengal  also  plays  a role in flooding. In Delhi and Haryana it is the Yamuna, the biggest tributary of the Ganga, which causes a marginal amount of flooding. Most of these flooding regions suffer from inadequate channel capacity as well as regulation of river water flow in these channels.

Earthquakes and Seismology

An earthquake is a major demonstration of the power of the tectonic forces caused by endogenetic thermal conditions of the interior of the earth. An earthquake is a motion of the ground surface, ranging from a faint tremor to a wild motion  capable  of  shaking  buildings apart and causing gaping fissures to  open  in  the  ground.  The  Richter  scale  devised  by Charles F. Richter in 1935 measures the magnitude or intensity of energy released by an earthquake. Good Friday Earthquake of March 27, 1964 in Alaska (USA) measuring 8.4 to

8.6 on  Richter  scale  is  among  the  greatest  earthquakes  of  the  world  ever  recorded.

The science that studies the behaviour and patterns of seismic waves is called seismology. The place of origin of an earthquake is called focus, which is always hidden inside the earth, but its depth varies from place to place. The place of the origin of an earthquake is called ‘focus’ which is always hidden inside the earth. The deepest earthquake may have its focus at a depth  of  even  700  km  below  the  ground  surface.  Major  Himalayan  earthquakes,  such as the Bihar-Nepal earth quake of August 2, 1988, have their focus around 20-30 km deep. The place on the ground surface, which is perpendicular to the buried ‘focus’ or ‘hypocenter’,

recording the seismic waves for the first time is called ‘epicenter’. The waves generated by an earthquake are called ‘seismic waves’ which are recorded by an instrument called seismograph. The lines joining the places of equal intensity of seismic waves on the maps are called is oseismallines.

Causes of Earthquakes

Earthquakes are caused mainly due to disequilibria in any part of the crust of the earth. A number of causes have been assigned to cause disequilibria in the earth’s crust such as volcanic eruptions, faulting and folding, gaseous expansion and contraction inside the earth, hydrostatic pressure of man-made water bodies like reservoirs and lakes, and plate movements.

(1) Vulcan City

Volcanic activity is considered to be one of the major causes of earthquakes. Vulcan city and seismic events are so intimately related to each other that they become cause and effect for each other. Earthquakes follow each volcanic eruption and many of the severe earthquakes cause volcanic eruptions. The explosive violent gases during the process of Vulcan city try to escape upward and hence they push the crystal surface from below with great force and thus is’ caused severe earth tremors of high magnitude.

(2) Faulting and Elastic Rebound Theory

The horizontal and vertical movements caused by end genetic forces result  in  the formation of faults and folds which in turn cause isocratic disequilibria in the crystal rocks which ultimately causes earthquakes of varying magnitudes depending on the nature and magnitude of dislocation of rock blocks caused by faulting and folding. The 1950 earthquake of Assam was believed to have been caused due to disequilibria in crystal rocks;

(3) Hydrostatic Pressure and Anthropogenic Causes

Certain human activities such as pumping of ground water and oil, deep underground mining, blasting of rocks by dynamites for constructional purposes, nuclear explosion, storage of huge volume of water in big reservoirs etc. also cause earth tremors of serious consequences. The introduction of additional load through the construction of large dams and impounding of enormous volume of water in big reservoirs behind the dams cause disequilibria of adjusted rocks below the reservoirs.

(4) Plate Tectonic Theory

The earth is composed of solid and moving plates having either continental crust or oceanic crust or even both continental oceanic crusts. The earth’s crust consists of 6 major plates (Eurasian plate, American plate, African plate, Indian plate, Pacific plate and Antarctic plate) and 20 minor plates. These plates are constantly moving in relation to each other due to thermal convective currents originating deep within the earth. All sorts of disequilibria are caused due to different types of plate motions and consequently earthquakes of varying magnitudes are caused.

CLASSIFICATION OF EARTHQUAKES

Each earthquake differs from the other and thus it becomes difficult to classify all the earthquakes into certain categories.

(1) Classification on the Basis of Causative Factors

(A) Natural Earthquakes are  those,  which  are  caused  by  natural  processes  i.e.  due to end genetic forces. These are further divided into four subcategories.

(i) Volcanic Earthquakes  are  caused  due  to  volcanic  eruptions  of  explosive and fissure types and are confined  to  volcanic  areas.  Severe  earthquake caused by violent explosions of Etna volcano in 1968.

(ii) Tectonic Earthquakes are caused due to dislocation of rock blocks during faulting activity. Such earthquake is very severe and disastrous i.e. 1906 earthquake of California (USA).

(iii) Isostatic Earthquakes are triggered due to sudden disturbance in the Isostatic balance at regional scale due to imbalance in the geological processes.

(iv) Plutonic Earthquakes are in fact, deep focus earthquakes, which occur at greater depths.

(B) Anthropogenic Earthquakes are caused by human activities such as pumping of water and mineral oil from  underground  aquifers.  and  oil  reserves  respectively, deep underground mining, blasting of rocks by dynamites for constructional purposes

e.g. Koyna  earthquake  of  Maharashtra  of  1967  due  to  Koyna  reservoir  etc.

(2) Classification on the basis of Focus

On the basis of the depths of their  foci these have  been divided into 3 types.

(i) Moderate Earthquake: Foci are located at the depths between 0-50 km.

(ii) Intermediate Earthquake: Foci at the depths between 50-250 km.

(iii) Deep Focus Earthquake: Foci at the depths between 250-700 km.

Classification on the basis of Human casualties

(i) Moderately Hazardous Earthquakes: If deaths of human range below 50,000 due to seismic tremors e.g. Tabas earthquake of Iran 1978 A.D. (death toll 25,000).

(ii) Highly Hazardous Earthquakes: If deaths of human range between 51,000- 1,00,000 due to seismic tremors e.g. in 1935, Quetta, Baluchistan, (death toll 60,000).

(iii) Most Hazardous Earthquakes: If deaths of human casualties are above 1,00,000 mark e.g., in 1976 Tang-Shan, China (death toll 7,50,000).

World Distribution of Earthquakes

Earthquakes are, in fact associated with the weaker and are statically distributed areas of the world. Most of the world earthquakes occur in the zones of young folded mountains, the zones of faulting and fracturing, the junction  of  continental  and  oceanic  margins,  the zones of active volcanoes and along the different plate boundaries. The world map of the distribution of earthquakes prepared by seismologists show the occurrence of  earthquakes along the following belts.

(i) Circum-Pacific Belt: surrounding the Pacific Ocean.

(ii) Mid-Continental Belt: representing epicenters located along the Alpine-Himalayan Chains of Eurasia and northern Africa and epicenters of East African Fault zones.

(iii) Mid Atlantic Belt: representing the earthquakes located along the mid-Atlantic Ridge-and its offshoots.

Effects of Earthquake hazardous

Earthquakes and their hazards are determined on the basis of the magnitude of seismic intensity as determined by Richter scale but are decided in the basis of quantum of damages done by a specific earthquake to human lives and property.

(i) Landslides

Weaker landmasses and tectonically sensitive land margins cause landslides and debris falls, which damage settlements and transport systems on the lower slope segments.

(ii) Damage to Life and property

Structures such as buildings, roads, rails, factories, dams, bridges suffer a huge damage thus causing a heavy loss of  human  life  and  property  both.  The  vibrations  of  earthquakes last longer and the amplitudes of seismic waves are greater artificially in filled and leveled depressions, swamp deposits etc. than in the structures of consolidated materials and bedrocks. Two major earthquakes of Bihar-Nepal border in 1934 and 1988 explain the impact of earthquake disasters on human  structures  and  human  lives.  The  damage  caused  by  the Bihar earthquake of 15 January 1934, measuring 8.4 on Richter scale, include 10,700 human deaths, landslides and slumping in an area of 250 km length and 60 km width, ruptures and faults in the ground surface etc.

(iii) Damages to Government Infrastructure

Cities and towns are worst affected due to large concentration of human population, commercial complexes and residential areas. Due to  collapse  of  large  buildings  there  is greater loss of life and property. Due to collapse of buildings ground water pipes are bent and damaged thus water supply is disrupted, electric and telephone poles are uprooted and there is total disruption of power and communication. Other side effects are collapsed sewer system causing epidemics, roadblocks etc.

(iv) Fire Hazard

Earthquakes strongly  shake  the  buildings  and  thus  strong  oscillations  cause  severe fires in houses, mines and factories because of overturning of cooking gas cylinders, contact of live electric wires, churning of blast furnaces, displacement  of  other  electric  and  fire- related appliances.

(v) Landmass Deformation

Severe earth tremors and resultant, vibrations caused by severe earthquakes result in the deformation of ground surface because of crusts and troughs in the ground surface and faulting activity.

(vi) Flash Floods

Strong seismic events result in the damages of  dams  and  cause  severe  flash  floods. Severe floods are also caused because of blocking of water flow of rivers due to rock blocks and debris produced by severe tremors on the hill slopes facing the river valleys.

(vii) Tsunamis

The seismic waves, caused by the earthquakes traveling through seawater, generate high sea waves and cause great loss of life and property. Since the pacific Ocean is girdled by the earthquakes and volcanoes tsunamis are more common in the pacific with a minimum frequency of 2 tsunamis per year.

A CASE STUDY

U.P. Earthquake of 1991

A severe earthquake occurred in Garhwal region of Uttar Pradesh on 20th Oct. 1991. Intensive tremors were felt at 2.53 a.m., which lasted for about 45 seconds. The magnitude of earthquake was measured 6.6 on Richter scale and  its  epicenter  was  at  Angola,  a  place near Uttarkashi, Mild tremors are a  regular  feature  of  the  area.  The  worst  affected  areas have been in the district of Uttarkashi, Tehri Garhwal and  Chamoli  while  it  also  caused sizeable damage in the districts of Dehradun, Pauri Garhwal and Nainital.  The  roads  and bridges are the chief means of communication in hill region, which underwent heavy damage. The economy of such places is  based  on  tourism  to  a  great  extent,  which  suffered  a  great set back. The overhead drinking tanks and pipelines  had  developed  cracks.  Sources  of drinking water had been damaged. The earthquake caused intensive damage to the building of various government departments, Forest, Home, Finance and Rural Development.

Cyc8lones

Cyclones are the centers of low pressure surrounded by closed isobars having increasing pressure outward and closed air circulation from outside towards the central low pressure in such a way that air blows inward in anticlockwise on northern hemisphere and clockwise in southern hemisphere. They range in shape from circular, elliptical to V  shape.  From locational viewpoint cyclones are classified into two principal types e.g. i) extra-tropical cyclones/temperate cyclones ii) tropical cyclones.

(I) Temperate Cyclones

Temperate cyclones are atmospheric disturbances having low pressure in the centers produced in the middle latitudes characterized by converging and rising air, cloudiness and precipitation. They are formed in the regions extending between 350- 65" latitudes in both hemispheres due to convergence of two contrasting air masses e.g. After their formation temperate cyclones move in easterly direction under the influence of westerly  winds  and control the weather conditions in the middle latitudes.

(i) Shape, Size and Speed

Temperate cyclones are of different shapes e.g. circular, semi-circular, elliptical, elongated or V, but all of them are characterized by low pressure in their centres and closed isobars. The pressure difference between the centre and periphery is about 10-35 mb. It means that pressure increases from the centre towards outer margin. Average large diameter of an ideal cyclone is about t 900 km while short diameter measures t 000 km. The temperate cyclones move eastward under the influence of westerly winds with average velocity of 32 km per hour in summer and 48 km per hour in winters

(ii) Wind Systems

Since there is low pressure in the centre of temperate cyclone and air pressure increases outward and hence winds blow from the periphery towards the centre but these winds do not reach the centre straight rather they cut the isobars at the angle of 20° to 400 due to friction and Coriolis force and thus wind direction becomes anticlockwise in the northern hemisphere and clockwise in the southern hemisphere. Since temperate cyclones are formed due to convergence of two contrasting air masses and hence it is natural that there  are variations in the nature and direction of winds in different parts of the cyclones.

(iii) Temperature

Different temperatures are noted in different  parts  of  temperate  cyclones  because  of their origin due to convergence of two thermally contrasting air masses. The southern part of cyclone records higher temperature because of the dominance of warm air while the north-eastern, northern and north-western parts record low temperature because of the dominance of cold polar air mass. The western part records lowest temperature.

(iv) Source Regions and Tracks of Movement

The areas frequented by temperate cyclones mostly lie in the middle and high latitudes extending between 350-650 latitudes in both the hemispheres. These cyclones move, on an average, in easterly direction. (1) Cyclones after originating in the north Pacific off  the north-east and eastern coasts of Asia move in easterly and north-easterly direction towards the Gulf of Alaska and ultimately merge with Aleutian Lows from where they follow southerly direction and reach as far south as southern California. The cyclones moving inland dissipate and are  occluded  at the  windward  western slopes  of  the Rocky  Mountains.

(v) Origin of Temperate Cyclones

Though the formation and development of temperate cyclones is a quick process but it passes through a series of successive stages. The period of a cyclone from its inception

(cyclogenesis) to its termination (proteolysis or occlusion) is called the ‘life cycle of cyclone’; which is  completed through  six successive stages.

(a) The first stage involves the convergence of two air masses of contrasting physical properties and directions. Initially, the air mass (warm and cold) move parallel to each other and a stationary front is formed. This is called initial stage.

(b) The second stage is also called  as  ‘incipient  stage’,  during  which  the  warm  and cold air masses penetrate into the territories of  each  other  and  thus  a  wave-like front is  formed.

(c) Third stage: This is the mature stage when the cyclone is fully developed and isobars become almost circular.

(d) Fourth stage: Warm sector is narrowed in extent due to the advancement of cold front than warm front, as cold front comes nearer to warm front.

(e) Fifth stage: Starts with the occlusion of cyclone when the advancing cold front finally overtakes the warm front and an occluded front is formed.

(f) Sixth stage: Warm sector completely disappears, occluded front is eliminated and ultimately cyclone dies’ out.

(II) Tropical Cyclones

(i) General Characteristics

Cyclones developed in the regions  lying  between  the  tropics  of  Capricorn  and  Cancer are called Tropical Cyclones which are not regular and uniform like extra tropical or temperate cyclones. There are numerous forms of  these  cyclones,  which  vary  considerably  in  shape, size, velocity and weather conditions. The weather conditions of low latitudes mainly rainfall regimes are largely controlled by Tropical Cyclones.

(a) Size of tropical cyclones varies considerably. On an average their diameters range between 80 km and 300 km.

(b) Weak cyclones move at the speed of about 32 km per hour while hurricanes attain the velocity of 180 km per hour or more.

(c) Tropical cyclones become more vigorous over the oceans  but  become  weak  and feeble while moving over land areas. This is why these  cyclones  affect  only  the coastal areas e.g. Tamil Nadu, Orissa and West Bengal coasts of India.

(d) The centre  of  the  cyclone  is  characterized  by  extremely  low  pressure.

(e) Tropical cyclones are not characterized by temperature variations in their different parts because they do not have different fronts.

(f) There are no different rainfall cells hence each part of the cyclones yields rainfall.

(g) Tropical cyclones are not always mobile. Normally, they move from  east  to  west under the influence of trade winds

(h) Tropical cyclones are confined to a particular period of the year (summer season).

(ii) Types of Tropical Cyclones

Generally they  are  divided  into  4  major  types:

(a) Tropical disturbances  or  easterly  waves

(b) Tropical depressions

(c) Tropical storms

(d) Hurricanes or  typhoons

(iii) Origin of Tropical Cyclones

On an average, tropical cyclones are formed due to development of low pressure of thermal origin. They develop when the following requirements are fulfilled:

(a) There should be continuous supply of abundant warm and moist air. Tropical cyclones originate over warm oceans having surface temperature of 27°C.

(b) Higher value  of  Coriolis  force  is  required  for  the  origin  of  these  cyclones.

(c) They are associated with inter-tropical convergence (lTC), which extends from 50

-300N latitudes during summer season.

(d) There should be anti-cyclonic circulation at the height of 9000 to 15000 m above the surface disturbance.

(iv) Distribution of Tropical Cyclones

There are 6 major regions of the tropical cyclones e.g. (1) West Indies, Gulf of Mexico, and Caribbean Sea. (2) Western North Pacific Ocean including Philippines, Islands, China Sea, and Japanese Islands. (3) Arabian Sea and Bay of Bengal. (4) Eastern Pacific coastal region off Mexico and Central America. (5) South Indian Ocean of Madagascar (Malagasi), and (6) Western South Pacific Ocean, in the region of Samoa and Fiji Island and the east and north coasts of Australia.

(v) Environmental Impact of Tropical Cyclones

Tropical cyclones are very severe disastrous natural hazards which inflict heavy loss to human lives and property in terms of destruction of buildings, transport systems, water and power supply systems, disruption of communication system, destruction  of  standing agricultural crops, domestic and wild animals, natural vegetation, private  and  public institutions etc. Through damages  caused by  high velocity  winds, floods  and storm  surges.

ANTICYCLONES

General Characteristics

Surrounded by circular isobars anticyclone is such a wind system which has highest air pressure at the centre and lowest at the outer margin and  winds  blow  from  the  centre outward in clockwise direction in the northern hemisphere and anticlockwise in the southern hemisphere fig.13. Thus, anticyclones are high-pressure systems and more common in the subtropical high pressure belts but are practically absent in  the  equatorial  regions. Anticyclones were classified into (i) warm anticyclones, and  (ii)  cold  anticyclones  by Hanzilk in 1909.

Figure 5.2:  Generalized  representation  of  air  pressure  and  wind  system  in  an  anticyclone.

They are  characterized  by  the  following  properties.

(1) They are usually circular in shape. The  difference  of  pressure  between  the  centre and periphery of anticyclone ranges between 10-20 mb.

(2) They are much larger in size and area than temperate cyclones.

(3) Anticyclones follow cyclones. They move very sluggishly. The average velocity of anticyclones is 30-50 km per hour.

(4) Winds descend from above at the centre and thus weather becomes clear and rain less because the descending winds cause atmospheric stability.

(5) Temperature in anticyclones depends on weather, nature of air mass and humidity in the air.

(6) Anticyclones do  not  have  fronts.

1. Wind Systems and Temperature

Wind system is not fully developed in anticyclones because of weak pressure gradient. On an average, wind circulation is of divergent system wherein winds spread in all directions from high-pressure centre to low-pressure periphery. The winds are very much sluggish in the rear portion in comparison to the front portion. The  centre  is  characterized  by  light breeze.

These arise due to the descent of either polar cold air mass or warm tropical air mass. Cold anticyclones are associated with extremely low temperature and they cause cold waves during winter season but when they come in summer season, weather becomes pleasant.

2. Shapes and Size

Anticyclones are generally of circular shape but are very large in size. They become so large in size that their diameters become 9,000 km.

3. Weather Conditions

Generally, anticyclones are rainless and sky is free of clouds because of the fact that descending air in the centre of anticyclone is warmed up at dry adiabatic rate due to subsidence. This causes rise in temperature, which reduces normal lapse rate of temperature, with the result the stability of air increases resulting into marked increase in the aridity of air. This is why anticyclones are indicative of dry weather.

4. Landslides

Among physiographic units, the two northern units of the Greater Himalayas (7500- 8500m), and the Inner Himalayas (Trans-Himalayan zone), an intervening system of high plateau and valleys lying between the two great mountain ranges, are considered along with middle mountains, the traditional centres of population. The upper northern section of these middle mountains remains largely’ under upper montane forest (2900-4000 m), below which is the belt of intensive agriculture. Lithology is highly varied, including sedimentary, metamorphism, and granites. However, there are extensive areas of phyllites and schists; these are deeply weathered and the prevailing steep slopes render them highly susceptible to erosion and slope failure (mostly through landslides). Presently, according to gross yet reliable estimate, the landslides occupy about 1% of land surface in only five central districts of Himachal Pradesh. They have a total volume of more than 2.2 x 106 m3 and a mean age of 6.5 years. This helps to evaluate the denudation rate, which is about 12 mm/year (all erosive processes). Landslides have about 2.5-mm/ year denudation rates. One of the main causes of landslides is road construction.

Suggestions

Various studies indicate that for each linear kilometer of mountain road, 10 small to medium landslides occur. Prior  to  the  1962  border  war  with  China,  the  Himalayan  section in India was in most parts accessible only  on  foot.  The  shock  of  the  Chinese  military presence, the three India-Pakistan wars of 1947, 1965, and 1971,  the  continued  border tensions (especially along the Kashmir ceasefire line), and several other problems led to accelerated construction of up to 10,000 km of highways and connecting roads. The poor alignment and ill-considered design are causing a total soil loss of 0.199 t of sediment per linear meter of road per annum. Valdiya (1973) indicated that during the construction phase an average kilometer of road requires the removal of 40,000-80,000 m3 of debris. These enormous volumes are dumped on the roadsides and damage ecologically fragile slopes by depriving them of natural vegetation and at times destroy the terraces.