Unit-I PGDEM-03

WATER POLLUTION

Rajesh Kumar

STRUCTURE

1.0. OBJECTIVES

1.1. INTRODUCTION

1.2. WATER QUALITY STANDARDS

1.2.1 Drinking Water Standards

1.2.2 Stream Standards

1.2.3 Irrigation Standards

1.2.4 Effluent Standards

1.2.5 Minimum National Standards (MINAS)

1.3 SOURCES OF WATER POLLUTION

1.3.1 Municipal and Domestic Wastes

1.3.1.1 Harmful Effects of Domestic Wastes

1.3.2 Industrial Wastes

1.3.2.1 General Effects of Domestic Wastes

1.3.3 Agricultural Wastes

1.3.3.1 General Properties of Pesticides

1.3.3.2 The Effects of Pesticides on Target and Non-

target Organisms.

1.3.4 Heat and Radioactive Wastes

1.4 SUMMARY

1.5 KEYWORDS

1.6 SELF ASSESSMENT QUESTIONS

1.7 SUGGESTED BOOKS

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1.0 OBJECTIVE:

After shedding this unit, you will be able to:

• Understand what are the main causes of water pollution.

• Understand why there is a need of establishing different

water quality standards.

• Become familiar to different water quality standards

• Become familiar to different sources of water pollution

and their characteristics and harmful effects.

1.1 INTRODUCTION

Water exists in various forms in various places. Water can exist in

vapour, liquid or solid forms and exists in the atmosphere

(atmospheric water), above the ground surface (surface water), and

below the ground surface (sub-surface water). Both surface and

sub-surface water originate from precipitation, which includes all

forms of moisture from clouds, including rain and snow. A portion

of the precipitated liquid water run off over the land (surface

runoff), infiltrates and flows through sub-surface (sub-surface

flow) and eventually finds its way back to the atmosphere through

evaporation from lakes, rivers, and ocean, transpiration from trees

and plants; or evapo-transpiration from vegetation. This chain is

known as Hydrological Cycle.

2

Fresh water accounts for just 1/10000 of the total water available

on the planet, yet this quantity seems immense when the volume

is expressed as 1,25,000 km3 . On global scale, this amount is

quite constant year to year, being constantly replenished by

precipitation of reviously evaporated from the ocean (3,50,000 km3

) and from land (70,000 km3). Unfortunately, most of the

precipitation fall back into the ocean and only area 1,10,000 km3

falls on the land. More than half of the 40,000 km3 of water that

does not evaporate run off to the ocean in flood events and is not

available for use throughout the year.

Lakes contain almost all of the fresh surface water on the planet.

The water in rivers and streams make up less than one percent of

the volume in lakes. This fact alone suggests that lakes require

special protection from contamination.

Another fact to consider is that it takes many years to replenish

lakes owing to the relatively small amount of precipitation that falls

on the lake and the small amount of stream water that runs

directly into lakes. On average, lake replenishment takes 100

years, whereas the replacement time for water in streams and

rivers is 11 days. Thus, if contaminants are distributed throughout

the average lake, the incoming water cannot restore the lake to its

initial quality for a long time.

Water quality characteristics of aquatic environment arise from a

multitude of physical, chemical and biological interaction. The

water bodies (rivers, lakes and estuaries) are continuously subject

to a dynamic state of change with respect to their geological age

and geochemical characteristics. This is demonstrated by

continuous circulation, transformation and accumulation of energy

and matter through the medium of living things and their

activities.

3

The water stored in reservoir and lakes, together with the water

that flows perennially in stream, is subject to heavy stress;

because it is used for water supplies, agriculture, industries and

recreation, it can be easily misused. Most cities and industries

discharge wastewaters to streams and rivers, rather than to lakes

and reservoirs. Even though wastewaters are treated, large

quantities of contaminants flow down steam on the way to the

ocean as the water is used over and over again.

Pollution is a qualitative term. It describes the situation that

occurs when the level of contaminants is such that intended water

use is impaired. It takes just a small amount of contaminant to

pollute a water body intended for a drinking water supply. But the

same water might not be considered polluted if the water were to

be used, for example for agriculture. Pollution is not restricted to

contaminants. Physical factors of the environment can also

contribute to pollution. For example, heated water discharged from

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a power plant can change the temperature of an aquatic

environment. It might not be a problem in a lake or a river during

the winter, but it can certainly be a problem in the summer time.

The major sources of surface water contamination are

construction, municipalities, agriculture, and industries. However,

the water delivered to earth in the forms of precipitation in not

necessarily pure to begin with. Near the coast, it may contain

particulate and dissolved sea salts; further inland; it may contain

organic compounds and acids scrubbed from contaminants added

to the atmosphere both by natural processes and by anthropogenic

(human) activities. Gases from plant growth and decay and gases

from geological activities are example of naturally derived

atmospheric contaminants that can be returned to earth via

precipitation. The acid rain problem of the New England states is a

classic example of anthropogenically derived atmospheric

contaminants that contribute to surface water pollution.

The Environmental Pollution Panel of the U.S. Presidents Science

Advisory Committee defines environmental pollution as the

unfavorable alteration of our surrounding, wholly or largely as a

by-product of man’s actions, through direct or indirect effects of

changes in energy patterns, radiation levels, chemical and physical

constitution and abundance of organisms. These changes may

affect man directly or indirectly through his supplied of water and

of agricultural and other biological products, his physical objects

or possessions, or his opportunities for recreation and appreciation

of nature.

The substances which cause pollution are known as pollutants.

Pollutants may be defined as any substance that is released

intentionally or unintentionally by man into the environment in

such concentration that may cause adverse affect on environment

health. The Indian Environment (Protection) Act, 1986 defines 5

pollutant as any solid, liquid or gaseous substance present is such

concentration as may be or tend to be injurious to environment.

However, nature by itself treats, recycles and makes good use of

these pollutants. But as the 20th century comes to a close, the

large volume and increasing poisonous nature of man made

pollutants threats the integrity of nature and cultural development

of man.

The term water pollution is referred to the addition to water of an

excess of material (or heat) that is harmful to humans, animals or

desirable aquatic life, or otherwise causes significant departures

from the normal activities of ‘various living communities in or near

bodies of water. The National Water Commission (1973) stated that

‘water gets polluted if it has been not of sufficiently high quality to

be suitable for highest uses; people wish to make of it at present or

in the future.

1.2 WATER QUALITY STANDARDS

All sort of pollutants are added to the water bodies. We have

limited resources of water and the requirements are numerous, so

there lies the demand of conserving and minimizing the pollution

of water.

Polluted water is hardly of any use for most purposes. It cannot be

utilized for drinking due to health risk. Water with high salt

content is unsuitable for agriculture and industrial purposes. The

quality of water interferes with the aesthetic and economic

pursuits of water bodies by affecting the fish and other aquatic

organisms. However, the water which is not suitable for drinking

may be good for irrigation, or water unsuitable for irrigation may

be quite suitable for industrial cooling or fish growth. Thus it can

be seen that each use of water has its own limits on the degree of

pollution it can accept.

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The achievement for this minimum quality of water for diverse uses

has led to the formation of water quality criteria, water quality

objectives and water quality standards. Water quality criteria can

be considered as specific requirement on which a decision to

support a particular use will be based. The criteria for various uses

are developed based on experimental data, our current knowledge

of health and ecological and economic effects of water quality.

Water quality objectives can be defined as aim or goal with regard

to the water quality which is to be achieved. It is not as rigid and

authoritative as a standard and does not have the enforcement

element of requirement. The term standard applies to any definite

principle or measure established by an authority by limiting

concentration of constituents in water which ensure safe use of

water and safeguard the environment. However, sometime

standards may not be fair due to lack of sound scientific

knowledge. Thus, standard may change with the accumulation of

more scientific knowledge and on other consideration.

To attain desired water quality objectives, the standard can be

applied in two ways. One type called ‘effluent standards’ are

applicable for municipal, agricultural or industrial wastes

discharge into water resources and on land. Second type

concerned with water receiving or affected by the effluents.

1.2.1 Drinking Water Standards

Raw water quality and standards depends upon the end use. The

four main uses are municipal, industrial, agricultural and

recreational (fish and wildlife). As water quality is degraded day by

day, so, it become very important to set the drinking water

standards for the safety of water of our limited resources. Different

agencies have set environment standards for safe drinking water

like Bureau of Indian Standards (BIS), World Health Organization

(WHO), European Economic Community (EEC) etc. 7

Drinking water standards, are regulation that Bureau of Indian

Standards (BIS) set to control the level of contamination in the

drinking water. Bureau of Indian Standard consider the inputs

from many organization i.e. Central, State, Semi Government,

Municipal Corporation, Public Health Organization, etc.

throughout the standard setting process.

Indian Water Standards (ISI)

Property/Consti

tuent

Desirable

Limit

Permissible

Limit

Undesirable effects outside the

desirable limit

Physico-chemical Characteristics

Turbidity (NTU) 2.5 10 Aesthetically undesirable

Colour (Platinum

Cobalt Scale) 5.0 25 Aesthetically undesirable

Taste and Odour Unobjectio

nable

Unobjection

able Aesthetically undesirable

Major Chemical constituents

pH 6.5-8.5 6.5-9.2 Affects taste

Total dissolve

solids (mg/1) 500 1500 Causes gastrointestinal problems.

Hardness (mg/1) 300 600

May cause urinary concretion,

disease of kidney, bladder and

stomach disorder.

Calcium (mg/1) 75 200

Essential for nervous and muscular

system, cardiac function and

coagulation of blood. Deficiency

causes rickets. Excess concentration

causes kidney or bladder stone and

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irritation in urinary passage.

Magnesium

(mg/1)

<30 if SO4

is 250

mg/1

100

Essential as an activator for may

enzyme system. Excess concentration

may have laxative effects.

Magnesium salts are cathartic and

diuretic.

Chloride (mg/1) 250 1000

Affects taste and potability, causes

indigestion, may be injurious to

people suffering from heart and

kidney diseases.

Sulphate (mg/1) 200 400 Causes laxative effects in presence of

Magnesium.

Nitrate (mg/1) 45 100

Causes infant methemoglobinemia

(blue babies). May cause gastric

cancer and affects central nervous

system and cardiovascular system.

Fluoride (mg/1) 1.0 1.5

Essential for teeth and bones,

reduces dental caries in

concentration range of 0.8-1.0 mg/1.

At high level teeth mottling, skeletal

and crippling fluorosis occurs.

Iron (mg/1) 0.3 1.0 Give bitter sweet astringent taste

Manganese

(mg/1) 0.05 0.5 Unpleasant taste

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Copper (mg/1) 0.05 1.5

Astringent taste, deficiency results in

nutritional anemia in infants, high

concentration may damage lever and

cause central nervous system,

irritation and depression.

Zinc (mg/1) 5.0 15

Very small amount beneficial Impart

astringent taste at higher

concentration.

Toxic Constituents

Arsenic (mg/1) 0.05 0.05 Skin disease, circulatory system

problem, risk or cancer.

Cadmium (mg/1) 0.01 0.01 Kidney damage

Chromium

(mg/1) 0.05 0.10 Lung tumor, allergic dermatitis.

Cynide (mg/1) 0.05 0.05 Causes nervous damages and

thyroid problem

Lead (mg/1) 0.05 0.05 Serious commutative body position.

Selenium (mg/1) 0.01 0.10 Small amount beneficial, large

amount toxic.

Mercury (mg/1) 0.001 0.001 Large amount causes brain and

kidney damage

PAHs (mg/1) 0.20 0.20 Toxic

Physical and Chemical Quality of Drinking Water (BIS)

Quality Highest Desirable Maximum Permissible

PHYSICAL

10

Turbidity (NTU Units) 5 10

Colour (Hazen Units) 5 25

Taste Agreeable Agreeable

Odour Unobjectionable Unobjectionable

CHEMICAL

PH 6.5 - 8.5 NO relaxation

Total Dissolve Solids

(mg/1)

500 2000

Total hardness as CaCO3

(g/1)

300 600

Alkalinity as CaCO3

(mg/1)

200 600

Calcium (mg/1) 75 200

Magnesium (mg/1) 30 100

Iron (mg/1) 0.3 1.0

Manganese (mg/1) 0.1 0.3

Copper (mg/1) 0.05 1.5

Zinc (mg/1) 5.0 15.0

Aluminum (mg/1) 0.03 0.20

Chloride (mg/1) 250 1000

Sulphate (mg/1) 200 Upto 400 if Mg does not

exceeds 30 (mg/1)

Boron (mg/1) 1.0 5.0

Phenolic Substances

(mg/1)

0.001 0.002

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Fluorides (mg/1) 0.6-1.2 1.5

Nitrates (mg/1) 45 100

Arsenic (mg/1) 0.05 No relaxation

International Standards for Drinking Water

Parameter Max. Permissible

USPH standards

WHO standards European

standards

PH 6.0-8.5 6.5-9.2 6.5-8.5

Sp. Conductivity

(µmho cm -1)

300 - 400

Arsenic 0.05 0.05 -

Ammonia 0.5 0.5 -

DO 6.0 6.0 -

Boron 1.0 - -

Calcium 100 200 100

Cadmium 0.01 0.01 -

Chromium (vi) 0.05 0.01 -

Copper 1.0 1.0 -

Chloride 250 600 250

Cyanide 0.05 0.05 -

COD 4.0 10 5.0

Iron 0.3 1.0 -

Lead 0.05 0.1 -

Magnesium 30 150 -

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Manganese 0.05 0.5 -

Mercury 0.001 0.001 -

Nitrate + Nitrite 10 45 -

Polynuclear Aromatic

Hydrocarbons (PAH)

0.002 0.002 0.002

Pesticides (Total) 0.005 - 0.005

E.Coli 100/100ml 10/100ml -

Total Hardness as

CaCO3

- 500 -

Total dissolve solids 500 - -

Phenol 0.001 0.002 0.005

1.2.2 Stream Standards

Fresh water is used for irrigation, drinking, industry, power

generation, recreation and even for discharging waste water into

water bodies. This has lead to the concept of classification and

zoning of water bodies which indicate that their quality has to meet

the requirement of one or more of the above potential uses.

The water resources can be classified or zoned depending upon the

designated best use of the water. The Central Pollution Control

Board (CPCB) along with State Pollution Control Boards (SPCB)

has adopted a scheme of classification and zoning of water bodies.

The water quality criteria for this classification are given for fresh

water as below.

Water Quality Criteria for Freshwater Classification (CPCB,

1979)

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Classes Criteria

Class A Dissolve oxygen (>6 mg/1), BOD <2 mg/1),

MPN of coliforms (<50 per 100 ml), pH (6.5-8.5)

Class B Dissolve oxygen (>5 mg/1), BOD (<3 mg/1),

MPN of coliforms (<500 per 100 ml), pH (65-8.5)

Class C Dissolved oxygen (>4 mg/1), BOD (<3 mg/1),

MPN of coliforms (5000 per 100 ml), pH (6.0-9.0)

Class D Dissolved oxygen (>4 mg/1), pH (6.5-8.5)

Free ammonia as N (<1.2 mg/1)

Class E PH (6.0 - 8.5), Electric conductivity

(<2,250µ mhos/cm), sodium absorption ratio

(SAR) (<26), Baron (<2 mg/1)

Note: Class A Drinking water source without conventional

treatment but after disinfection.

Class B Outdoor bathing.

Class C Drinking water source with conventional

treatment followed by disinfection.

Class D Propagation of wildlife, fishery.

Class E Irrigation, industrial cooling, and controlled

waste disposal.

1.2.3 Irrigation Standards

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Major parameters of concern of irrigation water quality are salinity

(dissolved solids and conductivity), potential trace elements and

herbicides.

Class

of

water

TDS

(ppm)

Sulphate

(ppm)

Chloride

(ppm)

Sodium

(%)

Boron

(ppm)

E.C.

(µmho/cm)

Suitability for

Irrigation

I 0-700 0-192 0-142 0-60 0-0.5 0-750 Excellent to good for

irrigation

II >700-

2000

192-480 142-355 60-75 0.5-2.0 >750-2250 Good to injurious,

suitable only with

permeable soil and

moderate leaching,

harmful to sensitive

crops.

III >2000 >480 >355 >75 >2.0 >2250 Unfit for irrigation.

Suitability of Water for Different Constituents for Irrigation

Suitability of Water for Irrigation with Different Values of

Sodium Absorption Ratio (SAR)

SAR Suitability for Irrigation

0-10 Suitability for all crops and all types of soils except for those

crops which are highly sensitive to sodium.

10-18 Suitable for coarse textured or organic soil with good

permeability. Relatively unsuitable in fine textured soil.

18-26 Harmful for almost all types of soil. Required good drainage,

high leaching and gypsum addition.

>26 Unsuitable for irrigation.

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Trace Elements Limit for Irrigation Water in mg/I, Used

Continuously for Crops

Element Limit

Aluminum 1.0

Arsenic 1.0

Boron 0.75

Cadmium 0.005

Chromium 5.0

Cobalt 0.2

Copper 0.2

Lead 5.0

Manganese 2.0

Molybidenum 0.005

Nickel 0.5

Selenium 0.05

Zinc 5.0

1.2.4 Effluent Standards

The effluent standards pertain to the quality of waste water

originating from community agricultural operations and industry.

In general, these standards control the quality of pollutants in the

effluent through effluent treatment at the desired degree.

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BIS (ISI) Standards for discharge of sewage and industrial

effluents in surface water sources and public sewers.

Tolerance Limit for

Industrial Effluents

Discharged into

Sr.

No.

Characteristics of

Effluents

Tolerance

Limit for

Sewage

Effluents

Discharged

into Surface

Water

Sources as

per IS 4764-

1973

Inland

Surface

Water, as

per IS

2490-

1974

Public

Sewer as

per IS

3396-

1974

1. BOD5 (mg/1) 20 30 500*

2. COD (mg/1) - 250 -

3. pH - 5.5 to 9.0 5.5 to

9.0

4. Total suspended

solids (TSS) (mg/1)

30 100 600

5. Temperature 0C - 40 45

6. Oil and grease (mg/1) - 10 100

7. Phenolic compounds

(mg/1)

- 1 5

8. Cyanides (mg/1) - 0.2 2

9. Sulphides (mg/1) - 2 -

10. Fluorides (mg/1) - 2 -

11. Total residual

chlorine (mg/1)

- 1 -

17

12. Insecticides (mg/1) - Zero -

13. Arsenic (mg/1) - 0.2 -

14. Cadmium (mg/1) - 2 -

15. Chromium (VI)(mg/1) - 0.1 2

16. Copper (mg/1) - 3 3

17. Lead (mg/1) - 0.1 1

18. Mercury (mg/1) - 0.01 -

19. Nickel (mg/1) - 3 2

20. Selenium (mg/1) - 0.05 -

21. Zinc (mg/1) - 5 15

22. Chloride (mg/1) - - 600

23. % Sodium - - 60

24. Ammonical Nitrogen

(mg/1)

- 50 50

25. Radioactive materials.

i) α-emitters

(micro curie

/ ml)

ii) β-emitters

(micro-

curie/ml)

-

-

10-7

10-6

-

-

*Subject to relaxation or lightening by the local authorities.

1.2.5 Minimum National Standards (MINAS)

The MINAS are industry specific effluent standards which are

being evolved at the National level. Hence, State authorities are not

required to relax them except when the ambient water quality

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criteria warrants their alteration to suit the location. This suggests

treatment of all wastewater to certain minimum standards

regardless of the type of wastewater and locations. The minimum

treatments is provided to any wastewater aim at the removal of

pathogens, toxic substances, colloidal and dissolve organic solids,

mineral oils and adjustment of pH.

1.3. SOURCES OR WATER POLLUTION

The sources of water pollutants can be classified as :

1. Municipal and domestic oxygen demanding wastes which

contains decomposable organic matter and pathogenic

agents.

2. Industrial wastes which contains toxic agents ranging from

metal salts to complex synthetic organic chemicals.

3. Agriculture wastes which comprises fertilizers, pesticides etc.

and

4. Radioactive wastes and heat.

1.3.1 Municipal and Domestic Wastes

It includes waste water from homes and commercial

establishment, consist of domestic refuge, municipal garbage and

other wastes like animal wastes, crops and yard wastes and

garbage’s are mainly of organic origin. Domestic waste water arises

from many small sources spread over a fairly wide area but is

transmitted by sewer to a municipal waste treatment plant.

Generally, the impurities in domestic wastes get diluted and

seldom total more than 0.1% of the total mass. Some of the main

constituents of sewage are given below in Table.

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Some of Primary Constituents of Municipal Sewage

Constituents Potential Sources Effects in water

Oxygen-demanding

substances

Mostly organic

materials,

particularly human

faces

Consume dissolve

oxygen.

Refractory Organics Industrial wastes,

household products

Toxic to aquatic life.

Pathogens (Bacteria

viruses etc.)

Human wastes Cause diseases.

Detergents Household

detergents

Esthetics, prevent

grease and oil

removal, toxic to

aquatic life.

Phosphates Detergents Algal nutrients.

Grease and Oil Cooking, food

processing,

industrial wastes

Esthetics, harmful to

some aquatic life.

Salts Human wastes,

water softeners,

industrial wastes

Increase water

salinity

Heavy Metals Industrial wastes,

chemical

laboratories

Toxic

Chelating Agent Detergent and

industrial wastes

Heavy metal ion

stabilization and

transport.

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Solids All sources Esthetics, harmful to

aquatic life.

The origin of these wastes is clearly connected with human

metabolism and vital activities.

As these wastes are largely of organic nature thus get oxidized by

bacterial decomposition to nitrate, phosphate, carbon dioxide and

water. This type of decomposition consumes the oxygen and places

an oxygen demand on the system which can be monitored by a

common indicator test, known as BOD test. In this analysis the

amount of oxygen for decomposition is measured over a 5 day or 3

day period at 20 0C. If waste contain significant amount of organic

material, the bacterial decomposition will remove large amounts of

dissolve oxygen, which causes oxygen depletion.

Inorganic impurities are sand, clay, particles of ore, chalk, mineral

salt, mineral oils and many other substances which are used by

man for various purposes. Public sewage also contains various

micro-organism like bacteria, yeasts and other moulds, algae, eggs

of helminthes, viruses etc, which spread disease like typhoid and

paratyphoid fever, dysentery, cholera, polio etc. and other human

health problems.

Sewages and run off from agricultural land provide plant nutrients

in natural setting, particularly lakes lead to eutrophication (Greak

:well nourished) which lead to algal blooms and large amount of

other aquatic weeds, causing serious problem of oxygen depletion

in addition to foul smell (due to H2S gas), unaesthetic scene and

even death of the lake. When sewage is discharged into a natural

water body, the receiving water gets polluted due to waste product

present in sewage effluents. But the condition do not remain so

forever, because the natural forces of purification, such as dilution,

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sedimentation, oxidation, reduction etc., bring back the waste

water into its original state. This natural purification of polluted

water is called as self purification. However, the self purification

can not be achieved when environmental conditions are not

favorable.

1.3.1.1 Harmful Effects of domestic Wastes

1. Increased in incidence of water borne disease, as sewage

contain many type of pathogenic organisms.

2. Water becomes totally unfit for drinking and domestic

purpose.

3. Oxygen depletion leads to death of aquatic organisms and

even death of aquatic ecosystem.

4. Water becomes extremely anesthetic and foul smelling.

1.3.2 Industrial Wastes

Most of the Indian rivers and fresh water streams are seriously

polluted by industrial wastes or effluents which come along waste

water of different industries such as petro-chemical complexes,

fertilizer factories, oil refineries, pulp and paper, textile, sugar and

steel mills, tanneries, distilleries, coal washeries, synthetic

material plants for drugs, fibres, rubber, plastic etc. The industrial

wastes of these industries and mills include metals (copper, zinc,

lead, mercury, cadmium, etc.), detergents, petroleum, acids,

alkalies, phenols, carbonates, alcohols, cyanide, arsenic, chlorine

and many other organic and inorganic toxicants. All these

chemicals of industrial origin have been toxic to animals and many

bring about death or sub-lethal pathology of the liver, kidney,

reproductive system, respiratory system or nervous disorder in

both the vertebrate and invertebrate aquatic animals (Wilpur,

22

1969). Important characteristics of waste water from some of major

industries are given below

Sr. No. Industries Important Characteristics

1. Acid Manufacturing Low pH.

2. Sugar High BOD and COD.

3. Coal Wahery Low pH, high suspended

solids.

4. Coke manufacturing &

phenol & oils

High suspended solids,

ammonia, hydrogen peroxide.

5. Distillery High BOD and COD, brown

colour, disagreeable odour,

high dissolve solids.

6. Electroplating Low pH, high COD, heavy

metals & toxic substances.

7. Paint High BOD, contains synthetic

resins, solvents, pigments and

heavy metals like aluminum,

chromium and lead.

8. Petrochemical High BOD/COD ratio,

hydrocarbon, alcohols, phenols,

oil etc.

9. Plastic Manufacturing Acid, formaldehyde and

phenols.

10. Paper and Pulp High pH, high coloured and

odour, high total solids.

11. Tannery High BOD, COD, total solids, oil

and grease, heavy metals like

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chromium.

12. Textile High BOD, dyes, acids,

phenolic substances, chlorine

and chromium.

Industrial waste discharge into water body lead to pollution of

water and polluted water results into following:

A. Organic substances deplete the oxygen content of water

body.

B. Inorganic substances make water unfit for drinking and

other purposes.

1.3.2.1 General Effects of Industrial Effluents

A. Industrial water contains coloured material like dyes make

water unaesthetic and objectionable.

B. Effluents having acid and alkalies adversely affects the

growth of fish and other aquatic life.

C. Toxic substances like cyanide, phenol and heavy metals like

Hg, Pb Ar cause damage to flora and fauna.

D. Oil and other greasy floating substances interfere with self

purification mechanism of water bodies and also lead to

suffocation to aquatic life.

E. The polluted water body become unfit for swimming due to

presence of chemical irritants.

F. The presence of dissolve salt contribute to water hardness

and make it unsuitable for industrial use as hard water lead

to scale formation.

G. High pollution in rivers will interfere with navigation by

causing corrosion of ships, boats and form the sludge 24

mounds at the bed i.e. coal washery waste causes extensive

deposits in river and removal of which is very expensive.

H. Thermal pollution will interfere with life cycle of aquatic life.

I. Phosphates and nitrates bring about excessive growth of

vegetation and lead to eutrophication in water bodies.

J. Chemical pollutants can even enter the aquatic human food

chain through bio-accumulation and bio-magnification and

results in serious health problem.

In India, all the 14 major rivers have become polluted. The river

Damodar is perhaps the most heavily polluted river. River Mini-

Mahi in Baroda has been another heavily polluted river which is

having variety of industrial and petrochemical wastes. The river

Ganga from Haridwar to Calcutta is regarded as one unending

sewer which is fit only to carry urban liquid wastes, half burnt

dead bodies, pesticides and insecticides. The 27 cities contribute

about 1000 million liters of waste water to the river each day. The

water of Ganga affects the health of about 250 million people of

Northern Indian. Many or our lakes, Notably the Dal Lake, are

becoming darkened, smelly and choked with excessive growth of

algae.

Some of major hazards of industrial effects are given below:-

1. The “itai-itai disease in Japan due to cadmium poisoning

was traced due to the discharge of waste water from a mine

processing Cu, Pb, Zn in “Jintsu River”. The river water is

used in paddy crop irrigation. Similarly Minmata was caused

by mercury poisoning (1955).

2. Lake Zurich in Switzerland and lake Erie in Canada are

classic examples of induced eutrophication.

25

3. Hoogly at Calcutta is receiving waste from power station,

paper, jute, textile and chemical mills at an average rate of

52 tones /day. The water quality is worst than 4th grade as

proposed by WHO.

4. The water of ‘Yamuna at Okhala industrial area for about 48

kms stretch is unfit ever for irrigation purposes.

5. Discharge of untreated waste from a group of dye industries

into the Kalu River near Mumbai, resulted in lowering of pH

to 4.0.

1.3.3. Agricultural Wastes

It includes sediments, fertilizers, pesticides and farm animals

wastes, which reach the water bodies through runoff and leaching.

Very broadly, agricultural pollution is caused by refuse of any form

from agricultural operations of any kind. Agricultural refuse

generally includes the following type of wastes:

1. Manure and other wastes from farms and the operation of

feed lots or poultry houses.

2. Slaughter house wastes.

3. Fertilizers runoff from cropland.

4. Harvest wastes

5. Pesticides that escape in the atmosphere or into the water

supply.

6. Salt and silt drained from irrigated land or eroded land.

Until the mid 1950s animal wastes posed little problem, because

they were, for most part reused as fertilizers or other uses. With

advancement of agribusiness, the large numbers of animals are

kept in small areas which lead to excess of animal waste in and

confined to a given area and thus, it become economically

26

impossible to distribute wastes for reuse as fertilizers. This waste

finds its way into water bodies through runoff during the period of

heavy rainfall. As these wastes are organic, they increase the BOD

of the receiving water bodies.

Inorganic fertilizers, being plant nutrients, lead to over fertilization

of water bodies when they inter water bodies through runoff or

during irrigation. Excess plant nutrients lead to excessive plant

growth, the process called eutrophication. When plant dies they

settle to the bottom, since they are organic, increases the BOD of

the water bodies.

Soil erosion is a serious problem. It increases the normal rate of

filling of water bodies and decreases the amount of fertile land for

crop production. Sediments decrease the transparency of water,

which limit the photosynthesis. It addition, sediments into fresh

water bodies tends to clog the gills of adults fish and settles out

over incubating eggs, causing suffocation.

A remarkably large number of pesticides have come into

widespread use in recent time. Many of these compounds have

been not only non-biodegradable but also only slightly soluble in

water. Consequently, when sprayed on crop land they remain in

soil for long period of time. During the period of high rainfall or

irrigation, they tend to be carried into surface, marine or ground

water system. In both fresh and marine water bodies they enter the

food chain, undergo bio-concentration in non-target organisms and

increase in animal tissue to alarming level. Excessive use of the

pesticides like BHC, PCBS, DDT etc., made them an integral part

of chemical and bio-chemical cycles of the earth. Even these

pesticides have been detected in Artic region.

1.3.3.1 General properties of pesticides

27

1. They often strike not only the intended parts but also

several non-target organisms.

2. Many of these chemicals are persistent and cannot be

disposed off.

3. They cause unintended affects like resistance, faunal

displacement and other population changes.

4. They are carried away to place far away from the

points of application.

5. They tend to bioaccumulation and bio-magnification.

1.3.3.2 The effects of pesticides on target and non-target

organisms.

1. Increase disease susceptibility in host.

2. Development of pesticide tolerance.

3. Bio-accumulation and bio-magnification.

4. Disturbance in equilibrium, existing between pests

and their parasites (Pray-Predator relationship)

5. Disturbance in reproductive physiology.

6. Food contamination, and

7. Effects on beneficial living organism.

1.3.4. Heat and Radioactive Wastes

Thermal power plants, nuclear power plants and many chemical

industries use lot of water for cooling purpose and return this

water to stream at higher temperature. Increased temperatures

increase the rate of chemical and biochemical reactions. Biological

systems have the optimum temperature at which enzymes

function.

28

Thus increased temperature affects the enzyme catalysis and even

death of aquatic organisms. Increased temperatures of a water

body also decrease solubility of dissolve gases.

Radio active substances are the most toxic substances, whose

injurious effects are tremendous. Nuclear war material, test

explosions, increased use of power reactor and radioactive

materials in medical, industrial and research purposes are the

principle source of ratio active exposure that threaten the

environment.

1.4 SUMMARY

Water exist in three forms i.e. vapour, liquid or solid. It is present

in atmosphere (atmospheric water), surface (surface water) and

below the ground (sub-surface or ground water). On the earth

water is constantly replenished by precipitation through

hydrological cycle. We have limited resources of water in ice cap,

river, lakes etc and the requirement are numerous, so there lies

the demand of conserving and minimizing the pollution of water.

Polluted water is hardly of any use for most purposes that’s why,

water quality standards are required. The main sources of water

pollution are municipal and domestic wastes, industrial wastes

and agriculture wastes. Impacts of different sources are different

because characteristics of wastes are different for different sources.

Compositions of municipal and agricultural wastes are more less

constant but it vary from one industry to another in case of

industrial wastes.

1.5 KEYWORDS

Water pollution: Water can be regarded its changes its quality or

composition either naturally or as a results of human activities

thus becoming less suitable for drinking, domestic, agricultural,

industrial, recreational, wildlife and other uses.

29

Standards: The term standard applies to any definite principle or

measure established by an authority by limiting concentration of

constituents in water which ensure safe use of water and

safeguard the environment.

Oxygen demanding waste: The wastes which deplete the

dissolved oxygen of a water body are called oxygen demanding

waste.

Municipal wastes: It consist mainly the domestic sewage i.e. water

born waste of community contain of 99% water and 1% solids. Of

the solids 70% are organic 30% are inorganic in nature.

Industrial wastes: The wastes from industry like sugar, dairy,

paper tannery etc. industrial waste have the greatest potential of

the receiving water.

Domestic wastes: The waste generated in household like kitchen,

toilet etc. is called as domestic waste.

1.6 SELF ASSESSMENT QUESTIONS

1. What are Environmental Standards? Give BIS

standards of drinking water and industrial effluent

and sewage discharge in surface water, and public

sewer.

2. Give details of sources of water pollution.

3. How industrial effluents effect the water quality?

4. How the Municipal and domestic wastes effects the

dissolved oxygen of a water body?

5. Give important characteristics of industrial wastes.

6. What is thermal pollution and how it affects the water

quality of receiving water body?

30

7. Water is the water borne diseases and how they

spread?

1.7 SUGGESTED BOOKS

Aggarwal K C (1999). Environmental pollution. Agro Botanica,

Bikaner.

Aggarwal S K (2002). Pollution management-II water pollution.

APH Publishing Corporation, New Delhi.

Coler R A and Rockwood J P (1989). Water pollution biology (A

laboratory /field hand book). Technomic Publishing Co. Inc.,

Pennsylvania (U.S.A.)

Gaur D (2005). Water pollution and its management. Sarup &

Sons, New Delhi.

Goel R P (1997). Water pollution: causes, effects and control. New

Age International (Pvt.) Ltd, New Delhi.

Kumar A (2004). Water pollution – assessment and management.

Daya Publishing House, New Delhi. Manivasakam N (1984).

Environmental pollution. National Book Trust India, New

Delhi.

Mishra P C and Trivedy (1993). Ecology and pollution of Indian

lakes. Ashish Publishing House, New Delhi.

Smith R J (1996). Introduction to water pollution. Asian Books Pvt.

Ltd., New Delhi.

Thakur K (1999). Environmental protection law and policy in India.

Deep and Deep Publication, New Delhi.

Tripathi A K (1995). Water pollution. Ashish Publishing House,

New Delhi.

Tripathi B D and Govil S R (2001). Wate pollution – an

experimental approach. CBS Publisher, New Delhi.

31

32

Unit-I PGDEM-03

WATER POLLUTION

Rajesh Kumar

STRUCTURE 2.0 OBJECTIVES

2.1 INTRODUCTION

2.2 MAJOR POLLUTANTS

2.2.1 Oxygen Demanding Waste

2.2.2 Disease Causing Agents

2.2.3 Plant Nutrients

2.2.4 Synthetic Organic Compounds

2.2.4.1 Soap, Detergents and Detergent

2.2.4.2 Hydrocarbons

2.2.4.3 Pesticides

2.2.5 Oil Pollution

2.2.5.1 Sources of Oil Pollution

2.2.5.2 Fate and Movement of Oil in Marine Environment

2.2.5.3 Effects of Oil on Organisms

2.2.5.4 Control of Oil Pollution

2.2.6 Inorganic Chemical and Minerals

2.2.6.1 Heavy Metals

2.2.6.2 Toxicity of Metals to organisms

2.2.7 Sediments

2.2.7.1 Detrimental Effects of Sediments 2.2.8 Radioactive Materials

1

2.2.8.1Effect of Radiations

2.2.9 Thermal Pollution

2.2.9.1Effects of Thermal Pollution

2.3 SELF PURIFICATION

2.3.1 Oxygen-Sag Cruve

2.4 SUMMARY

2.5 KEYWORDS

2.6 SELF ASSESSMENT QUESTIONS

2.7 SUGGESTED BOOKS

2.0 OBJECTIVE

After studying this unit, you will be able to:-

• Understand the types of pollutants those responsible for water

pollution.

• Become familiar with different sources of different pollutants

and their harmful effects.

2.1 INTRODUCTION

The sign of water pollution are bad taste, massive weed growth in many

water bodies, emission of disgusting odour, decrease in number of fishes,

Oil can be seen floating on the surface of some water bodies or deposited

as scum on beaches etc. The origin of these problems could be attributed

to many sources and types of pollutants. The substance which causes

pollution is defined as pollutants.

2.2 MAJOR POLLUTANTS

The major water pollutants can be classified into 9 categories as given

below:

2

Oxygen demanding wastes.

Disease causing agents.

Plant nutrients.

Synthetic organic compounds.

Oil.

Inorganic chemicals and minerals.

Sediments.

Radioactive materials.

Thermal Pollution (Heat)

2.2.1 Oxygen Demanding Wastes

These are primarily organic materials that are oxidized by bacteria to

carbon dioxide and water and reduce the amount of available oxygen.

Microorganisms

Organic matter + O2 → CO2 + H2O + New cells + Stable product.

Glucose oxygen carbon dioxide water As dissolve oxygen (DO) drops, fish and other aquatic life are threatened

and in extreme case, killed. In addition, as DO levels fall, undesirable

odours, tastes, and colours reduce the acceptability of water as a

domestic supply and reduce its attractiveness for recreational uses.

Oxygen demanding wastes are usually biodegradable organic substance

contained in municipal waste or in effluents from certain industries,

such as food processing and paper production. In addition, the oxidation

of certain inorganic compounds may also contribute to the oxygen

demand. Even naturally occurring organic matter, such as leaves and

animal droppings, that find way into surface water add to the DO

depletion.

A common measurement of this type of pollution is biochemical oxygen

demand (BOD). BOD is amount of oxygen required for oxidation of

3

organic matter over a 5 day period at 200C and expressed in mg oxygen

per liter (mg/1). Fish and other aquatic life required about 5 mg/1 of DO

for their survival (higher in cold water, especially in spawning areas,

which require at least 7 mg/L ). The DO level of water saturated with

oxygen is 9.2 mg /1 at 200C. If sufficient DO is available, micro

organisms are able to oxidize the nitrogen compound and certain

inorganic compounds such as ferrous salts, sulphides and sulphites.

Another important test for this type of pollution is chemical oxygen

demand (COD). COD measurement have been carried out using strong

oxidizing compounds, like potassium dichromate, to oxidize even some

materials that have been biologically degradable and expressed as

milligram per liter (mg/L). COD value will be higher than BOD value.

2.2.2 Disease Causing Agent

It has long been known that contaminated water is responsible for the

spread of much contagious disease. Pasteur in later nineteenth century

established the germ theory of disease, that the role of pathogenic micro-

organisms in epidemic diseases. Pathogens are disease producing

organisms that grow and multiply within the host. Examples of

pathogens associated with water include bacteria responsible for cholera,

bacillary dysentery, typhoid and paratyphoid fever; viruses responsible

for infectious hepatitis and poliomyelitis; protozoa causes dysentery and

giardiasis and helminthes or parasitic worm cause schistosomiasis etc.

The intestical discharges of an infected individual, a carrier, may contain

billions of these pathogens, which, if allowed to enter to water supply,

can cause epidemics of immense proportions.

Contaminated water caused by poor sanitation can lead to both water

borne and water contact diseases. Water borne diseases are those

acquired by ingestion of pathogens not only in drinking water, but also

from water that make its way into the mouth from washing food, utensils

and hands. In developing countries like India, particularly in rural areas,

water is often taken from open wells or streams that are easily polluted.

4

Water contact diseases do not even require that individual ingest the

water Schistosomiasis is most common water contact disease.

Water also plays an indirect role in other diseases, common in

developing countries. Insect that bread in water, or bite near water, are

responsible for the spread of malaria, affecting some 160 million people

and killing 1 million each year. Yellow fever and sleeping sickness are

spread in this same way. Table given below summaries some of these

water related problems.

Type Spread by Example Prevalance

Water

borne

Drinking water

contaminated by

pathogen, or washing

hands, food or

utensils in

contaminated water.

Typhoid,

Cholera,

Dysentery,

Diarrhea,

Hepatitis,

Guinea worm

disease

6 million children

under five die from

diarrhea each year. 10-

20 million children die

each year from all types

of diarrheal disease. 10-

48 million annual

guinea warm cases.

Water

Contact

Invertebrates living

in water which act as

carrier (vectors).

Schistosomiasi

s (bilharzias),

leptospirosis,

tularemia.

Over 200 million people

infected world wide with

schistosomiasis.

Water

hygiene

Inadequate supplies

of water for personal

hygiene

Skin diseases,

scabies,

leprosy, yaws,

eye disease,

trachoma,

conjunctivitis.

500 million infected

with trachoma

(blindness occur in

sever cases; prevalence

of skin diseases

approaches 80% of

population in some

areas.

Source: Adopted from Marrison (1983)

5

The identification of pathogens in water needs very large samples and

many sophisticated techniques and is too time consuming and expensive

for routine pollution test. The standard method involves determination of

most probable number (MPN) of coliform organisms in the water sample.

Coliform bacterial like Escherichia Coli have been normal inhibitants of

human and animal intestine, and the daily per capita excretion in

human faces may number from 125 to 400 billion. Although coliforms

organisms have not been pathogens and are not affected by water

environment in exactly the same manner as pathogens, their existence

and density has proved to be a fairly reliable indicator of the adequacy of

treatment for reducing pathogens and coliform tests are therefore, widely

used.

2.2.3 Plant Nutrients

Nutrients are chemicals, such as nitrogen, phosphorous, carbon,

sulphur, calcium, potassium, iron, manganese, boron, and cobalt that

are essential to the growth of living beings. Aquatic species require a long

list of nutrients for growth and reproduction, but from water quality

perspective, the three most important ones are carbon, nitrogen and

phosphorous. Plant requires relatively large amounts of each of these

three nutrients and unless all three are available, growth will be limited.

The nutrient that is least available relative to plant’s needs is called the

limiting nutrient. This suggests that algal growth can be controlled by

identifying and reducing the supply of that particular nutrient. Carbon is

usually available from a number of natural sources including alkalinity,

dissolved carbon dioxide from atmosphere and decaying organic matter,

so it is not often the limiting nutrient. Rather, it is usually either nitrogen

or phosphorous that control algal growth rates. Major sources of both

nitrogen and phosphorous include municipal discharge, run off from

animal feed lots, chemical fertilizers and detergents.

Plant nutrients like nitrogen and phosphorous are able to estimate

growth of aquatic weed, particularly algae, which got interfere with water

uses and later decay to produce disagreeable odour and add to BOD of

6

water. The enrichment of water with nutrients is a naturally occurring

biological process called eutrophication. The term comes from two Greek

words meaning “Well nourished”. This enrichment leads to other slow

processes collectively referred as-natural aging of lakes. The steps in

eutrophication and aging of a lake have been as follow:

1. Streams from a drainage basin gradually bring soil and

nutrients to a newly formed lake, increasing the fertility of the

lake water.

2. The increased fertility lead to an accumulating growth of

aquatic organism, both plant and animal.

3. As living matter increases and organic deposits pile up on the

bottom of the lake, it become more shallow, warmer, and richer

in nutrients.

4. Plant take root at the bottom and gradually occupy more and

more of the place. Their remains accelerated the filling of the

basin.

5. The lake gradually become a marsh and finally a field or forest

as it has been over-taken by vegetation.

The time needed for this process to be completed could be in

thousands of years, but due to addition of nutrients by man’s activity

in water source increase the speed of this process.

Not only is nitrogen capable of contributing to eutrophication, but

also pose a serious public health problem. Nitrogen in water is

commonly found in the form of nitrate (NO3), which itself is not

harmful. However certain bacteria commonly found in intestinal tract

of infants can convert nitrate to highly toxic nitrite (NO2), which

combine hemoglobin in blood stream. When they replace that needed

oxygen a condition known as methemoglobinemia results ( blue baby

syndrome ). In extreme cases the victim die from suffocation. It occurs

in children of below 6 months age.

7

Essential Plant Nutrients: Sources and functions.

Nutrient Source Function

Macro-nutrient

Carbon (CO2) Atmosphere, decay Biomass constituent

Hydrogen Water Biomass constituent

Oxygen Water, Atmosphere Biomass constituent

Nitrogen (NO3) Decay, atmosphere

(from nitrogen fixing

organisms), pollutants

Protein constituents

Phosphorous (PO4) Decay, minerals

pollutants

DNA/RNA constituent

Potasium (K+) Minerals, pollutants Metabolic function

Sulphur (SO4) Minerals Proteins, enzymes

Magnesium Minerals Metabolic function

Calcium Minerals Metabolic function

Micro-nutrients

B, Cl, Co, Cu, Fe, Mo,

Mn, Na, Si, V, Zn.

Minerals, pollutants Metabolic function and

/ or constituent of

enzymes.

2.2.4 Synthetic Organic Compounds:

Organic chemicals can be considered to be any compound that contain

one or more carbon atoms in its molecular structure. Organic that

commonly enter water ways are pesticides, detergents and hydrocarbons.

The exotic organic chemicals includes surfactants in detergents,

pesticides various industrial products and the decomposition products of

other organic compounds. Analysis of polluted waters reveal the presence

of a wide variety of these compounds and many others have been

8

probably not being detected. Some of these compounds have been found

to be toxic to fish at very low concentration such as I ppm phenol. Many

are not biologically degradable, or are degraded only very slowly. As

many new chemical compounds get introduced each year without much

knowledge of their effects on natural ecosystems.

2.2.4.1 Soap, Detergents, and Detergents

These chemicals are potential sources of organic pollutants. These

pollutants are discussed briefly here.

Soaps: Soaps are salt of higher fatty acids, such as sodium Stearate, C17,

H35, COO-Na+. The cleaning action of soap results largely from its

emulsifying power caused by dual nature of the soap anion. A soap ion

consists of an ionic carboxyl ‘head’ and a long hydrocarbon ‘tail’.

In presence of oils, fats, and other water insoluble organic materials, the

‘tail’ of anion tends to dissolve in the organic matter, whereas the ‘head’

remains in aquatic solution. Thus, the soap emulsifies or suspends,

organic material in water. Soap lowers the surface tension of water, thus

making the water ‘wetter’.

The primary disadvantage of soap as a cleaning agent comes from its

reaction with divalent cations to form insoluble salts of fatty acid:

2 C17H35 COO-Na+ + Ca2 → Ca (C17H35CO2)2(S) + 2Na+

These insoluble products, usually salts of magnesium or calcium, are not

at all effective as cleaning agents and generally precipitate as calcium

and magnesium salts. Therefore, aside from the occasional formation of

unsightly scum, soap does not cause any substantial pollution problems.

9

Detergents

Synthetic detergents have good cleaning properties and do not form

insoluble salt with hardness ions (calcium and magnesium). It includes

as a part of its formulation a petrochemical or other synthetically derived

surfactant (10-30%) (to improve the action of surfactant) and other

ingredients like anti-corrosive sodium silicate, amide, foam stabilizers,

soil-suspending carboxymethyl cellulose sodium sulphate etc.

The surfactant lowers the surface tension of the liquid and it gives a

stable emulsion with soil particles. The builder, added to detergents,

complex with Ca2+ and Mg2+ and react with H2O to form alkaline solution

for functioning of surfactant. Sodium triple-phosphate Na5P3O10 is most

popular builder.

Until the early 1960s, the most surfactant used was alkyl benzene

sulphonate (ABS).

ABS is persistent surfactants and interfered with waste treatment

processes by Stabilizing small particles in colloidal suspension and

decreasing the activity of biological filter beds and activated sludge. The

foam formed by the detergent is visible and unaesthetic for all people.

These problems were solved by modifying the structure of surfactant so

as to make them more readily biodegradable. The linear alkyl sulphonate

(LAS) surface are now used.

10

Most of the environment problems later attributed to detergents arise

from builder rather than surface-active agents. Polyphosphate builder

undergo fast biodegradation by hydrolysis:

P3 O10-5 + 2H2O → 2HPO4-2 + H2PO4-

These hydrolysis products do not pose any threat to aquatic animal life.

However, phosphate act as nutrient for plants and thus cause

eutrophication by excessive growth of plants, particularly algae.

The most promising substitute for poly phosphate builders is the sodium

salt of nitrite-triacetic acid, N(CH2CO2Na)3. It is readily biodegradable

and relatively cheap. But it is hygroscopic

2.2.4.2 Hydrocarbons:

Hydrocarbons in the form of gasoline and motor oil, altogether insoluble

in water, have been carried from motorways and parking areas in rain

water, have been carried from motorways and parking areas in rain

water runoff. These wastes percolate into ground water and /or goes into

steam, rivers and lakes and affect the water quality.

2.2.4.3 Pesticides:

The term pesticides is used to cover a range of chemicals that kill

organisms that consider undesirable and includes the more specific

categories of insecticides, herbicides, rodenticides, and fungicides. There

are three main groups of synthetic organic insecticides: organo chlorines,

organophosphate and carbonates. In addition, number of herbicides,

including the chlorophenoxy compounds 2, 4,5-T and 2,4-D are common

water pollutants. Pesticides are classified as:-

Insecticides – designed to kill insect in crops

Herbicides – meant for killing weeds or undesirable vegetation.

Fungicides – toxic to moulds (fungi) and act to check plant diseases.

Other specific pesticides e.g. rodenticides , nematiocides etc.

11

At present there are more than 10,000 different pesticides. The use of

pesticides has helped in eradication of diseases such as malaria and

typhus and also increased production of food.

Pesticides: nomenclature and uses

Trade Name Uses Fresh

water

permissio

n limit

Chlorinated Hydrocarbon

Aldrin-Dieldrin Soil insecticide for control of

ants, beetles and cotton pests.

0.003

µg/1

Chlordane Effective against termites,

potential carcinogenic.

0.01 µg/1

Lindane Control of cotton insects and

nice stem borer.

0.01 µg/1

Dichloro Diphenyl Trichloro

ethane (DDT)

Broad spectrum-cotton,

soyabean, peanut pests,

mosquito control. Persistant in

environment accumulates in

food chain.

0.001

µg/1

Toxaphene Insect control on crops and

livestock, carcinogenic in nature

5 µg/1

Heptachlor Pest control in soil, carcinogenic. 0.001

µg/1

Eldrin Effective against black current

mud-mit- also used as a zoo-cide

precautions to be taken to avoid

skin contact-during application

0.004

µg/1

Methoxychlor Popular DDT –substitute-

bl bi d d bl l

0.03 µg/1

12

reasonably biodegradable-low

toxicity to mammals

Organophosphate

Malathion Control some pests of fruits and

vegetables little hazard to

mammals

0.1 µg/1

Parathion Larvicide for mosquito control,

also broad, spectrum insecticide

for fruit and vegetable pests.

Methyl parathion Control of plant pests.

Diazinor Control of may fruit and

vegetable pests.

Carbamates

Carbaryl Used on crops-cotton, forage,

fruits and vegetable, lawn and

garden insecticide, lawn toxicity

to mammals.

Baygon Control of flies, mosquitoes, ants

and cockroaches.

Dimetilan Control of house and fruit flies.

Chlorophenoxy acid

2,4-dichlorophenoxy acetic

acid (2,4-D)

Herbicide-control of broad leaved

weeds, aquatic vegetation,

defoliant.

100 µg/1

2,4,5-Trichlorophenoxy acetic

acid (2,4,5-T)

Weed control, defoliant

13

Most of organochlorine are now banned. The well known organochlorinie

pesticide is DDT, widely used to control insect that carry disease like

malaria, typhoid and plague and saved the life of millions of people

worldwide. It is persistent in nature and in term of human toxicity DDT

is considered to be relatively safe. It has its impact on food chain. DDT is

quite soluble in lipids, which means easily accumulated into fatty

tissues. Accumulation of organochlorine pesticides in fatty tissue means

that organisms at successive higher trophic levels in a food chain are

consuming food that has higher concentration of pesticides. At the top of

the food chain are consuming food that has higher concentration of

pesticides. At it is there that organochlorine toxicity has been

recognizable. For example, fish has higher concentration of pesticide

than water body and birds eating on fishes have much higher

concentration than fishes in their body. This phenomenon in which the

concentration of a chemical increase at higher levels in the food chain is

known as “biomagnifications or bio-concentration’.

Some of organochlorine are carcinogenic. Many insects species have

developed biological resistance to these pesticides. Organophosphates

are much more toxic than organochlorine pesticides as they are rapidly

absorbed through skin, lungs and gastro intestinal tract. Human

exposure to excessive amount has shown a range of symptoms including

tremor, confusion, slurred speech, muscle twitching and convulsions.

Acute human exposure to corbamates has lead to a range of symptom,

such as nausea, vomitting, and blurred vision and in extreme case,

convulsions.

Much more work is needed to determine the relationship to environment

of many of synthetic organic compounds. The following facts are known

about them:

1. Some have been resistant to biochemical breakdown by natural

water bacteria or waste treatment processes and therefore,

persist for extended period of time in water.

14

2. Some have been responsible for objectionable and offensive

taste, odors and colours of some fish and shellfish taken from

polluted water.

3. Some have been toxic to fish and other aquatic life when

present in very low concentration.

2.2.5 Oil Pollution

Oil pollution is a special problem due to unique property of oil to form a

thin film over a vast area. Oil pollution has been an almost inevitable

consequence of the dependence of a rapidly growing population on oil-

based technology. The use of natural resources such as oil on grand

scale, without losses, has been almost impossible. At present refined

petroleum products meet more than 62% of global energy requirements.

The extent of losses, intentional or accidental, has been steadily

increasing and has been becoming a great cause of concern. It has been

estimated that total oil influx into the ocean has been between 5-10

million tons annually.

2.2.5.1 Sources of oil pollution

1. Cargo tanker washing at sea.

2. Bilge pumping at sea.

3. In-port oil losses during loading and unloading procedures.

4. Vessel accidents i.e. One of the largest spill “Torrey Canyon

at the off coast of England in March of 1967. The oil spill

amounted to 1, 00,000 tons.

5. Losses during exploration and production of oil.

6. Oil leakage from pipe lines.

2.2.5.2 Fate and movement of oil in Marine Environment

Petroleum pollutants in the ocean may occur at any concentration and

oil in very small quantities, which can remain in the following forms:

1. Floating material

15

2. Emulsions dispersed in sea water

3. Dissolved in sea water

4. Adsorbed on sediments

5. Locked in marine organisms.

The freshly-spilled oil in sea water, after interacting with prevailing

physical chemical conditions and biological factors, undergo

compositional and chemical changes. Lighter fraction of oil evaporated

into the atmosphere by wind-spray and brusting of water bubbles.

Photoxidation form a variety of toxic and non-toxic materials such as free

radicals, carboxylic acids, esters, oxygenated aromatic, and carbonyl

compounds. Due to wave action, some oil droplets form oil in water

emulsion and sink at the bottom by incorporating silt and suspended

particles.

Rest of residual oil form film on the water surface as water-in-oil

emulsion (80% water). Microbial degradation of oil by some bacteria and

fungi results in formation of variety of products.

2.2.5.3 Effect of oil on organisms

Oil effects the organisms in a number of ways depending upon the

characteristics of the oil fraction and their concentration in water and

ranged from mechanical to various toxic effects. Some important effects

are described below:

1. Oil has smoothing effects (suffocation) on most of the aquatic

animals.

2. Effects the buoyancy and thermal insulation of birds and other

animals like seal.

3. Small animals can be caught in oil envelops and die.

4. Oil layer increase the temperature, which may be critical for

several organisms, particularly in Tropics.

16

5. A few aromatics like benezene and its derivatives have a very

high penetration power into the body of organisms and effects

the permeability by modifying the spacing of protein molecules

on each side of lipid layer. Brain and nerve cells are also

effected, which depend upon fatty substances. A few straight

chain and cycloparaffins also cause damage to the nervous

system.

6. Effect of oil on lipids cause maldevelopment of eggs and larvae.

7. Toxic constituents like non-hydrocarbons of oil (naphthanic

acid and those containing nitrogen, sulphur and oxygen with

carbon and hydrogen are more soluble) can affect the enzyme

system and other vital biomolecules in the body.

8. Effect the feeding and mating behavior in several species.

9. Embryo toxicity and disruption of ion regulation in sea birds.

10. Some polyaromatic hydrocarbons (PAHs) are carcinogenic to a

number of animals and PAHs are mutagenic and taratogenic.

11. Oil effect the migration behaviour in salmon.

12. The bioassay tests carried out by different workes reveal that

lighter oil and water soluble fractions (WSF) of fuel oil are

comparatively more toxic than heavy oil.

13. Algal cell division is inhibited at oil concentration as low as 0.01

ppm. At 0.02 ppm photosynthesis is inhibited.

14. Oils promote anaerobic conditions in water by preventing

diffusion of oxygen from air.

2.2.5.4 Control of oil pollution

1. Mechanical Containment

Oil Spill can be controlled from spreading by using containment barrier

(made up of polyethylene, polyurethane, polyvinyl chloride etc.) Another

17

technique is use of bubble and current barrier which generate surface

current in opposite direction of spread.

2. Mechanical Recovery

After containment oil can be removed by a number of means such as use

of weir, suction devices or by lifting surface.

3. Application Agents

Use of application agents help in dispersion, sinking, collection,

hardening, or burning of floating oil slicks.

4. Biodegradation

Several components of oil can be degraded by the microorganisms.

2.2.6 Inorganic Chemicals and Minerals

This category of water pollutants have been including inorganic salts,

mineral acids and finely divided metals or metal compounds. These

substances enter into water body through various activities like smelting,

metallurgical and chemical industries, mine drainage and various

natural processes and bring these general effects: acidity, salinity and

toxicity.

2.2.6.1 Heavy Metals

One of the major problem of inorganic chemical is due to heavy metals.

Sources of heavy metals are

1. Domestic wastewater and urban runoff: Use of detergent add

Fe, Mn Ni, Zn, Co, Cr and As to wastewater. Sewage sludge

contain Cu, Ag, Cd, Zn and Pb. Runoff from urban areas during

rainy season is rich heavy metals like Cu, Cr, Zn and Pb.

2. Industrial wastewater: Industry is important source of heavy

metals. A number of heavy metals are used by various

industries and a proportion of that find their way into effluents.

Industrial wastes contain toxic heavy metals like Zn, Cu, Cr, Ni,

Cd, etc. and generated from industries like Bakery, Brewery,

18

Fish processing, Ice-cream, Laundry, Metal processing,

Chemicals, textile etc.

Occurrence and Significance of Trace Elements in Natural Water

Element Sources Effects and

Singnificance

Arsenic Mining by-product,

pesticides, chemical

wastes.

Toxic possibly

carcinogenic

Beryllium Coal, nuclear power

and space industries

Acute and chronic

toxicity, possibly

carcinogenic

Boron Coal, detergent

formulations,

industrial wastes

Toxic to some plants

Cadmium Industrial discharge,

mining waste, metal

plating, water pipes

Replaces zinc

biochemically, cause

high blood pressure

and kidney damage,

destroys testicular

tissue and red-blood

cells, toxic to aquatic-

biota.

Chromium Metal plating, cooling-

tower water additive

(chromate), normally

found as Cr+6

Essential trace

element (glucose

tolerance factor),

possibly carcinogenic

as polluted water Cr

(VI)

Copper Metal plating,

industrial and

Essential trace

element, not very toxic

19

domestic wastes,

mining, mineral

leaching

to animals, toxic to

plant and algae at

moderate levels

Iron Corroded metal

industrial wastes, in

contact with iron

minerals.

Essential nutrient

(component of

hemoglobin), not very

toxic, damages

materials (bathroom

fixtures and clothing).

Lead

Industrial sources,

mining, plumbing, fuel

(coal)

Toxicity (anemia,

kidney disease,

nervous system),

wildlife destruction

Manganese Mining, industrial

waste, acid mine

drainage, microbial

action on manganese

minerals at low redox

potential (pE)

Relatively nontoxic to

animals, toxic to

plants at higher levels,

stains materials

(bathroom fixtures and

clothing).

Mercury Industrial wastes

mining, coal.

Acute and chroninc

toxicity.

Molybdenum Industrial waste,

natural sources,

cooling tower water

additive.

Toxic to animals,

essential for plants.

Selenium Natural geological

sources, coal.

Essential at low levels,

toxic at higher levels,

possible carcinogenic.

Silver Geological sources,

i i l t l ti

Causes blue-gray

di l ti f ki

20

mining, electroplating,

film-processing wastes

discoloration of skin,

mucous membrane,

eyes.

Zinc Industrial waste,

electroplating

Essential element in

many metallo-

enzymes, aids wound

healing, toxic to plants

at higher levels, major

component of sewage

sludge, limiting land

disposal of sludge.

Agricultural Activities: Use of fertilizer, pesticides, organic manure

cause the problem of heavy metals.

Mining Activities: Most of mineral ores contain varying quantities of

different heavy metals that tend to become free in the environment by

almost all mining and ore processing activities e.g. acid mine drainage is

rich in metal like Fe, Mn, Zn, Cu, Ni, and Co.

2.2.6.2 Toxicity of metals to organisms

Metal ions and their complex exhibit a wide range of toxicity to the

organisms that ranges from sublethal to lethal depending upon the time

of exposure and the prevailing conditions in the ambient water. Toxicity

is also determined by biological factor like the age and size of organisms.

Toxic responses of some of heavy metals are given below;

Metal Toxic Response

Lead (Pb) Anemia and disruption of hemoglobin synthesis,

damage to nervous system and kidneys, brain

damage. Acute lethal dose to man is 300-700 mg/kg.

In mild cases, insomnia, restlessness, loss of

appetite- and gastrointestinal problems.

21

Mercury (Mg) Brain damage.

Cadmium (Cd) Disorder of respiratory system, kidney and lungs,

cadmium salt consumption causes cramps, nausea,

vomiting and diarrhea, general decline in health.

Chromium (Cr) Occupational hazards of chromium (Cr+6) cause skin

and respiratory disorder, ulceratin of skin, inhaled

Cr+6 can cause cancer of respiratory tract.

Arsenic Skin cancer, hyper-pigmentation, black foot disease.

2.2.7 Sediments

Sediments are soil and mineral particles which are washed from land by

storms, and flood water, from cropland, unprotected forest soils,

overgrazed pastures, strip mines, roads and bulldozed urban area. It

represents the most extensive pollutants of surface water. Suspended

solids reaching natural water are about 700 times as large as the solid

loading from sewage discharge.

Bottom sediments are important sources of inorganic and organic matter

in streams, lakes, estuaries and ocean. The bottom sediments are

subjected to anaerobic conditions. The level of organic matter in

sediments are usually higher than in soils. Bottom sediments have the

ability to exchange cations with surrounding aquatic medium. Sediments

and suspended particles are important source of trace metals like Cr,

Cu, Mo, Ni, Co and Mn.

2.2.7.1 Detrimental Effects of Sediments

1. Stream channels, harbors and reservoirs are filled.

2. Destroys aquatic animals like fish and selfish by

blanketing fish nests and food supply.

3. Reduce light penetration into water. Hence reduce

the photosynthesis.

22

4. Increase the cost of water treatment.

2.2.8 Radioactive materials

Four human activities are responsible for radio active pollution.

23

1. Mining and processing of ores to produce unstable radioactive

Isotope Emitted particle Half-life

Americium-241 Alpha 433 yrs

Americium-243 Alpha 7370 yrs

Bismuth-210 Beta 5 days

Carbon-14 Beta 5730 yrs

Curium-245 Alpha 8500 yrs

Cobalt-60 Beta 5.27 yrs

Cesium-135 Beta 3 x 106 yrs

Cesiu yrs m-137 Beta 30.17 yrs

Tritium-3 Beta 12.33 yrs

Iodine-129 Beta 1.6 x 107 yrs

Krypton-85 Beta 10.7 yrs

Neptunium-237 Alpha 2.14x106 yrs

Lead-210 Beta 22.3 yrs

Plutonium-239 Alpha 29000 yrs

Plutonium-240 Alpha 6570 yrs

Radium-226 Alpha 1630 yrs

Radon-222 Alpha 3.82 days

Strontium-90 Beta 28.8 yrs

Thorium-230 Beta 8000 yrs

Uranium-234 Alpha 2.45 x 105 yrs

Uranium-235 Alpha 7.04 x 108 yrs

Uranium-238 Alpha 4.47 x 109 yrs

Xenon-133 Beta 5.25 days.

24

substances.

2. Use of radioactive material in nuclear weapon.

3. Use of radioactive material in nuclear power plants.

4. Use of radioactive isotopes in medical, industrial and research

application.

Massive production of radionucleotide by weapon and nuclear reactors

since World War-II has been accompanied by increasing concern about

effects of radioactivity upon health and the environment. Radionuclides

differ from other nuclei in that they emit ionizing radiation alpha particle

β- particles and gama rays. Some common radio isotopes often

concerned with environmental pollution, with their half life times are

given below in table

Alpha, beta and gamma rays are called ionizing radiation because they

produce ions in materials. Penetration power of gamma ( γ) rays is

highest, and alpha rays (α) have the lowest penetration power out of

these three.

2.2.8.1 Effects of Radiaions

The movement of radioactive material in the environment ultimate effects

the man. The radioactive pollutants reaching the freshwater resources of

ocean are rapidly lost to the sediments and bioaccumulated in plants

and animals directly or through food chain (bio-magnification). e.g.

accumulation of P-32 and Zn-65 is substantial higher in fish than water

source. Which are eaten by the man and these radioactive materials

affects the health of human being.

As α-particles are positive charge, it attracts the electron when pass

through material and bring ionization. β-rays repulsed the electron due

to negative charge and lead to ionization. Whereas, gamma rays directly

colloids the electron and eject the free electron.

These radiations produce the free radicals which interact with double

bonds, hydrogen bonds and sulphahydryl group (SH) present in proteins,

25

DNA, RNA and other bio-molecules. These interaction causes

deactivation of enzymes, mutation, inhibition of cell division, disruption

of cell membrane and overall damage to all cell performance.

Human response to various radiation which are given in short time span

are given below:

Radiation Dose

(Rads)

Human Response

650 or above Death in few fours or in days.

400 30 days LD 50 (death of 50 % humans within 30

days).

100-250 Sub-lethal dose, causes nausea, vomiting and

diarrhea within hours, itching, burning and

ulceration of skin, loss of hair, hemorrhages just

below skin, decline of red and white blood

corpuscles and loss of ability to fight diseases,

genetic mutations.

Less than 100 Delayed effects such as cancer, leukemia, sterility,

cataracts and reduction of life span, genetic

mutation.

26

2.2.9 Thermal Pollution

Thermal pollution can be defined as an accumulation of unstable heat from

human activities that disrupt ecosystem in the natural environment.

The most important anthropogenic sources of thermal pollution are the

industries which discharge vast quantity of heat in the environment. The heat

producing industries includes thermal power plant, nuclear power plant,

petroleum refineries, steel mills, chemical plants, pulp and paper mills etc.

2.2.9.1 Effects of Thermal Pollution

1. Effects the physical property of water, like decrease in solubility of

gases and increase in solubility of liquids and solids, toxicity of

pollutants etc.

2. Increase the evaporation of water and sedimentation.

3. Increase the rate of chemical reactions.

4. As different species favour different temperature. Thermal pollution

decline population of one species and growth of another.

5. Effect the protein and enzymes so effect the behaviors, reproduction

cycle, respiration rates etc. of many aquatic organisms.

6. At higher temperature, dissolve oxygen level decrease which effects the

aquatic life.

2.3 SELF-PURIFICATION

In natural water, self-purification exists in the form of a biological cycle

which is able to adjust itself, within limits, to changes in the environmental

conditions.

27

In a low organic-content stream there is little nutrients material to support

life so that, although, many different organisms may be present, there is

only relatively low number of each type. In streams with high organic

content it is likely that the DO level will be severely depressed producing

conditions unsuitable for animals and higher plant life. In these conditions

bacteria will predominate although given sufficient time the organic matter

will be stabilized, the oxygen demand will fall and full range of life form will

appear again.

Self-purification involves one or more or the following processes:

1. Sedimentation, possibly assisted by biological or mechanical

flocculation. The deposited solids will form benthic deposits which, if

organic, will decay an aerobically and which, if resuspended by flood

flow, can exert sudden high oxygen demands on the system.

2. Chemical oxidation of reducing agents such–as sulphides.

3. Bacterial decay due to the generally inhospitable environment for

enteric and pathogenic bacteria in natural waters.

4. Biochemical oxidation which is normally by far the most important

process. To prevent serious pollution it is important that aerobic

conditions are maintained; this means that the balance oxygen

28

consumed by BOD and that supplied by reaeration from the

atmosphere is not drastically disturbed.

2.3.1 Oxygen-Sag Curve

In streams, the addition of organic wastes results in the formation of a typical

‘oxygen sag curve’. It indicates that the maximum deoxygenation occurs at a

considerable distance away from the outfall because of slow process. According

to Klein (1962), the deoxygenation is influenced by a number of factors such as

the dilution of the organic pollutants after mixing, BOD of the organic wastes

and that receiving waters, the total organic load in the river, the nature of

organic material, temperature, initial dissolve oxygen in the stream extent of

reaeration from the atmosphere, and nature and density of the bacteria. By the

time the oxygen reaches to minimum, most of the organic matter is already

decomposed, and the process of reaeration takes over deoxygenation resulting

in the build-up of oxygen in the stream there after.

2.4 SUMMARY

Polluted water is unfit for different uses become of bad taste and odour,

massive weed growth, harmful effects etc. The substances which cause

pollution of water is defined as pollutants. There are classified as oxygen

29

demanding wastes, disease causing agents, plant-nutrients, synthetic organic

compounds, oil & grease, inorganic chemicals, radioactive substances, heat

etc. Oxygen demanding wastes decrease the D.O level of water bodies which

have harmful effects in aquatic fauna. Oxygen demanding wastes are measured

in the form of BOD. Disease causing agents are different pathogen i.e. viruses,

bacteria, helminthes, protozoa etc. which causes water born diseases. Plant

nutrients are nitrogen and phosphorus which causes eutrophication. Synthetic

organic substances are soap, detergents, pesticides etc responsible for different

human health problems and have harmful effect an aquatic and terrestrial

flora and fauna. Oil & grease causes suffocation because it acts as barrier for

diffusion of oxygen to water. Inorganic substances are mainly heavy metals

which causes toxicity in aquatic and terrestrial flora and fauna in addition to

human being.

Polluted water is self purified by sedimentation, chemical oxidation, bacterial

decay and biochemical oxidation. If pollution level is very high than water

cannot be self-purified or it takes long time. Thus treatment of polluted water is

required.

2.5 KEYWORDS

Water pollutants: A water pollutants can be defined as a physical, chemical or

biological factor causing aesthetic or detrimental affects on aquatic life and on

those who consume water.

Biological Oxygen Demand (BOD): The amount of oxygen used by

microorganisms to oxidize the oxydisable organic matter at 20 0C in 5 days is

known as BOD.

Heavy metals: Heavy metals are the metals which have a density above 5g per cm3.

Plant nutrients: These are the chemicals like nitrate, phosphate etc required

by the plant for their growth and cause eutrophication in a water body.

Eutrophication: It means the enrichment of nutrients in a water body. Which

lead to excessive plant growth in the water body.

30

Water pollution: Water can be regarded its changes its quality or composition

either naturally or as a results of human activities thus becoming less suitable

for drinking, domestic, agricultural, industrial, recreational, wildlife and other

uses.

Standards: The term standard applies to any definite principle or measure

established by an authority by limiting concentration of constituents in water

which ensure safe use of water and safeguard the environment.

Oxygen demanding waste: The wastes which deplete the dissolved oxygen of a

water body are called oxygen demanding waste.

Municipal wastes: It consist mainly the domestic sewage i.e. water born waste

of community contain of 99% water and 1% solids. Of the solids 70% are

organic 30% are inorganic in nature.

Industrial wastes: The wastes from industry like sugar, dairy, paper tannery

etc. industrial waste have the greatest potential of the receiving water.

Domestic wastes: The waste generated in household like kitchen, toilet etc. is

called as domestic waste.

2.6 SELF ASSESSMENT QUESTIONS

1. What are Pollutants? Give different type of water pollutants which

lead to pollution of water.

2. Why the D.O. level of water body falls when high-organic load

discharged into it?

3. What are water borne diseases? Why MPN test is conducted?

4. What is eutrophication and how it lead to aging of a lake?

5. What is biomagnification and bioaccumulation of pesticides? Give the

toxicity effects of different groups of pesticides.

6. What is marine pollution? Describes effects of oil pollution on marine

organisms.

31

7. Give the source of heavy metal pollution and effect of heavy metals on

plants and animals.

2.7 SUGGESTED BOOKS

Aggarwal K C (1999). Environmental pollution. Agro Botanica, Bikaner.

Aggarwal S K (2002). Pollution management-II water pollution. APH Publishing

Corporation, New Delhi.

Coler R A and Rockwood J P (1989). Water pollution biology (A laboratory /field

hand book). Technomic Publishing Co. Inc., Pennsylvania (U.S.A.)

Gaur D (2005). Water pollution and its management. Sarup & Sons, New Delhi.

Goel R P (1997). Water pollution: causes, effects and control. New Age

International (Pvt.) Ltd, New Delhi.

Kumar A (2004). Water pollution – assessment and management. Daya

Publishing House, New Delhi. Manivasakam N (1984). Environmental

pollution. National Book Trust India, New Delhi.

Mishra P C and Trivedy (1993). Ecology and pollution of Indian lakes. Ashish

Publishing House, New Delhi.

Smith R J (1996). Introduction to water pollution. Asian Books Pvt. Ltd., New

Delhi.

Thakur K (1999). Environmental protection law and policy in India. Deep and

Deep Publication, New Delhi.

Tripathi A K (1995). Water pollution. Ashish Publishing House, New Delhi.

Tripathi B D and Govil S R (2001). Wate pollution – an experimental approach.

CBS Publisher, New Delhi.

32

UNIT-II PGDEM-03

AIR POLLUTION: AMBIENT AIR QUALITY STANDARDS & MAJOR ATMOSPHERIC POLLUTANTS

Prof. C.P. Kaushik

STRUCTURE

1.0 OBJECTIVES

1.1 INTRODUCTION

1.2.1 NATIONAL AMBIENT AIR QUALITY STANDARDS

1.2.2 CLASSIFICATION OF AIR POLLUTANTS

1.2.3 SUSPENDED PARTICULATE MATTERS

1.2.4 HYDROCARBONS

1.2.5 INORGANIC GASES

1.2.5.1 Oxides of Carbon

1.2.5.2 Oxides of Nitrogen

1.2.5.3 Photochemical Oxidants

1.2.5.4 Fly Ash

1.3 SUMMARY

1.4 KEY WORDS

1.5 SELF-ASSESSMENT QUESTIONS

1.6 SUGGESTED READINGS

1.0 OBJECTIVES

After going through this unit you would understand the following :

- National ambient air quality standards used for comparison with

observed air quality parameters.

- Primary and secondary air pollutants.

1

- Type, characteristics and health effects of :

* Suspended particulate matter

* Hydrocarbons

* Oxides of carbon

* Oxides of nitrogen

* Photochemical oxidants

* Fly ash

1.1 INTRODUCTION

Pure air is odourless and colourless and has specific composition.

However, many substances, natural or anthropogenic (man-made) in

origin enter the atmosphere and upset the equilibrium which affects man

and his environment. Air pollution can, therefore, be defined as an

atmospheric condition in which some substances are present in such

concentrations which affect human, animal, livestock and plant life or

interfere in enjoyment of property. Air pollution is not a new

phenomenon. In the year 1307 King Edward- I banned the burning of

coal in lime kiln in London. There was a prohibition on use of coal in

London while Parliament was sitting. Queen Elizabeth was allergic to coal

smoke. In more recent times several air pollution episodes have attracted

the attention towards harmful effects of air pollution. London alone has

experienced about 10 air pollution episodes of which the one of Dec.

1952 was the worst and caused 4000 excess deaths. Other important air

pollution episodes occurred in Donora, Belgium, British Columbia,

Pennsylvania, Los Angeles (California) and Bhopal (India).

Most of the air pollution episodes were a result of inversions some of

which-contained high concentrations of SO2, particulate matters, CO,

oxides of nitrogen, various hydrocarbons etc.

2

1.2.1 NATIONAL AMBIENT AIR QUALITY STANDARDS

The concentration of six criteria pollutants i.e. CO, NO2, O3, SO2, PM10

(10 µm dia) and lead are to be maintained at certain permissible level

beyond which these show harmful effects. The concentration of these

criteria pollutants as given in Table - 1 should not exceed more than once

in a calendar year.

Table 1: National Ambient Air Quality Standards (NAAQS)

3

1.2.3 CLASSIFICATION OF AIR POLLUTANTS

The diverse variety of matter emitted into the atmosphere by natural and

anthropogenic sources is usually divided into two categories namely,

primary pollutants and secondary pollutants.

The primary pollutants are those that are emitted directly from the

sources e.g. particulate matter such as ash, smoke, dust, fumes, mist

and spray; inorganic gases such as sulphur dioxide, hydrogen sulphide,

nitric oxide, ammonia, carbon monoxide, carbon dioxide, and hydrogen

fluoride; olefinic and aromatic hydrocarbons; and radioactive

compounds. Of the large number of primary pollutants emitted into the

atmosphere, only a few are present in sufficient concentrations to be of

immediate concern. These are the five major types : particulate matter,

sulphur oxides, oxides of nitrogen, carbon monoxide, and hydrocarbons.

Carbon dioxide is generally not considered an air pollutant but because

of its increased global background concentration, its influence on global

climatic change causing global warming is of great concern. The

radioactive pollutants are of specialized nature and they can cause

mutations and affect plants, animals as well as human beings at genetic

level, if present beyond a threshold concentration.

The secondary pollutants are those that are formed in the atmosphere

by chemical interactions among primary pollutants and normal

atmospheric constituents. Pollutants such as sulphur trioxide nitrogen

dioxide, PAN (peroxyacetyl nitrate), ozone, aldehydes, ketones, and

various sulphate and nitrate salts are included in this category.

Secondary pollutants are formed from chemical and photochemical

reactions in the atmosphere. The reaction mechanisms and various steps

involved in the process are influenced by many factors such as

concentration of reactants, the amount of moisture present in the

atmosphere, degree of photo-activation, meteorological factors and local

4

topography.

1.2.3 SUSPENDED PARTICULATE MATTER (SPM)

In general the term "particulate" refers to all atmospheric substances that

are not gases. They can be suspended droplets, solid particles or

mixtures of the two. Particulates can be composed of inert or extremely

reactive materials ranging in size from 100 µm down to 0.1 µm and even

less. The inert materials do not react readily with the environment

whereas the reactive materials could be further oxidized or may react

chemically with the environment. The particulates may be of the following

types:

• Dust: The particle size ranges from 1 to 200 µm. These are formed by

natural disintegration of rock and soil or by the mechanical processes

of grinding and spraying. They have large settling velocities and are

removed from the air by gravity and other inertial processes. Fine

dust particles- act as centres of catalysis for many of the chemical

reactions taking place in the atmosphere.

• Smoke: It contains fine particles of the size ranging from 0.01 to 1

µm which can be liquid or solid, and are formed by combustion or

other chemical processes. Smoke may have different colours

depending on the nature of material burnt.

• Fumes: These are solid particles of the size ranging from 0.1 to 1 µm

and are normally released from chemical or metallurgical processes.

• Mist: It is made up of liquid droplets generally smaller than 10 µm

which are formed by condensation in the atmosphere or are released

from industrial operations.

• Fog: It is the mist in which the liquid is water and is sufficiently

dense to obscure vision.

5

• Aerosol: Under this category are included all air-borne suspensions

either solid, or liquid; these are generally smaller than 1 µm.

Particles in the size range 1-10 have measurable settling velocities but

are readily stirred by air movements, whereas particles of size: 0.1-1µm

have small settling velocities. Those below 0.1 µm, submicroscopic size

found in urban air, undergo random Brownian motion resulting from

collisions among individual molecules. Most particulates in urban air

have sizes in the range 0.1-10 µm. The finest and the smallest particles

cause most significant damage to health.

The chemical composition of particulate pollutants varies over a wide

range.

Particles from soils and minerals primarily contain calcium, aluminium

and silicon compounds. Smoke from combustion of coal, oil, wood, and

solid waste contains many organic compounds. Insecticide dusts and

certain fumes released from chemical plants also contain organic

compounds; Hydrocarbons themselves can coalesce into aerosol droplets

that constitute one kind of particulate matter. The most harmful

components of incomplete combustion are generally grouped as

particulate polycyclic organic matter (PPOM). These materials are

derivatives of benzopyrene, a potent carcinogen. Some trace metals such

as cadmium, lead, nickel and mercury present in the air may be the

cause of the greatest health hazard.

1.2.4 HYDROCARBONS

Hydrocarbons are compounds containing the elements of carbon and

hydrogen. By linking together in various ways, the carbon atoms form a

great variety of chain and ring molecules called Aliphatics and Aromatics

which number more than 1 million. Volatile compounds (VOC's), that

exist in the atmosphere primarily as gases because of their low vapor

6

pressures are the most important polluting hydrocarbons. However, it is

important to note that solid hydrocarbons can also cause an

environmental and health threat. For example, Benzopyrene, a well

known carcinogen, exists in the air as a fine particulate.

More hydrocarbons (HC) are emitted from natural sources than from the

activities of man. The one in greatest abundance is methane which has an

average background concentration of 1.55 ppm. This is produced in the

decomposition of dead material, mostly of plant origin. Methane is joined

by a class of compounds of a more intricate molecular structure known as

terpenes. These substances are emitted by plants, and are most visible as

the tiny aerosol particulates or the “blue haze” found over most forested

areas. Other hydrocarbons found in large concentrations in the ambient

air besides methane (CH4), are Ethane (C2H6), Propane (C3H8) acetylene

(C2H2), butane (C4H10) and isopentane (C5H12). Transportation sources are

by far the largest emitting sources of these hydrocarbons. About 15

percent of all atmospheric hydrocarbon is due to man’s activity. However,

the impact of man made hydrocarbons, by themselves, in air have

relatively low toxicity. They are of concern because of their photochemical

activity in the presence of sunlight and oxides of nitrogen (NOx). They

react to form photochemical oxidants. The primary pollutant is ozone

however, other organic pollutants like peroxyacetyl nitrate (PAN) have been

identified as the next highest component. Background levels of SO2 are

very low, about I ppb (parts per billion). In urban areas maximum

concentrations vary from less than 0.1 to over 0.5 ppm. SO2 itself is a lung

irritant and is known to be harmful to people who suffer from respiratory

disease. However, It is the sulfuric acid aerosol that causes the most

damaging health effects in urban areas. Oxides of Sulfur dioxide (SO2) is a

colorless gas with a concentration range of 0.3 to 0.1 ppm. Above 3 ppm it

has a pungent, irritating odor. Although SO2 emissions may occur from

volcanic eruptions, Most S02 (and sulfur trioxide, SO3) is due to the-

burning of coal and crude oils for electric power and heating.

7

The sulfur content of refined petroleum is usually quite low. At the high

temperatures of combustion, the sulfur in these fuels is converted to SO2

by the reaction:

S+O2 =SO2

1.2.5 INORGANIC GASES

The chemistry of the lower atmosphere is controlled by the reactivity of

oxygen. In the presence of molecular oxygen O2, the stable forms of

almost all of the elements are oxides, with the notable exception of

nitrogen. Thus, many of the major pollutants are oxides (i.e. CO, SO2,

SO3, NO, NO2) and their associated reactive by-products.

1.2.5.1 Oxides of Carbon

Significant amounts of carbon oxides, carbon monoxide (CO) and carbon

dioxide (CO2) are produced by natural and anthropogenic (man made)

sources. CO is considered a major atmospheric pollutant because of its

significant health effects, whereas, CO2 is a relatively non-toxic, present

in troposphere (lower atmosphere) and is, therefore, not usually

described as a major atmospheric pollutants However, anthropogenic

emission of CO2 is of significant concern because of its greenhouse effect

causing global warming.

Carbon monoxide (CO) is a colorless, odorless, tasteless gas formed by

the incomplete combustion of fossil fuels and other organic matter.

During combustion, carbon is oxidized to CO by the following reactions.

2 C + O2 → 2CO

2 CO + O2 → 2CO2

CO, formed as an intermediate in the combustion process, is emitted if

there is insufficient O2 present for reaction to proceed. CO is also

produced naturally by volcanic eruptions, forest fires, lightening and

8

photochemical degradation of various reactive organic compounds.

Biologically, CO is formed by some lower plants during incomplete

decomposition and various microorganisms in the oceans.

Major anthropogenic sources include transportation due to burning of

gasoline, industrial processing, solid waste disposal, agricultural burning

and cigarette smoking. Background concentrations of CO average 0.1

ppm, with peak concentrations in the northern hemisphere during the

autumn months due to the decomposition of fallen leaves. The residence

time for, CO in the atmosphere is estimated to be 0.1 to 0.3 years.

Cigarette smoke contains especially high levels of CO (15,000 to 55,000

ppm) which bind to approximately 3 to 10% of a smoker’s hemoglobin.

The effects of these high levels would be extremely harmful if it were not

for the intermittent nature of the exposure. The inhalation of air between

drags greatly reduces the toxic dose. The major effect of CO in cigarette

smoke appears to be to increase the risk of angina pectoris patients to

myocardial infarction and sudden death. However, cigarette smoke

contains many harmful substances and it is difficult to specifically assess

the harmful effects of CO and its exact role in cardiovascular diseases.

Oxides of sulfur : The sulfuric acid aerosols formed are usually less than

2 microns in diameter can quite effectively penetrate the inner most

passages of the lung as the pulmonary region.

SO2 in atmosphere is converted into sulfuric acid aerosols.

2 S02 + O2 = 2 SO3

SO3 + H2O = H2SO4

1.2.5.2 Oxides of Nitrogen

There are five major gaseous forms of nitrogen in the atmosphere;

nitrogen ammonia (NH3), nitrous oxide (N2O), nitric oxide (NO), and

nitrogen dioxide (NO2). N2 is the major gaseous component in the

9

atmosphere and accounts for 78% of the atmosphere’s mass. NO and

NO2 are important pollutants of the lower atmosphere and because of

their inter-convertibility in photochemical reactions, are usually

collectively grouped as NOx.

Nitric Oxide: It is a colorless, odorless, tasteless, relatively non-toxic gas.

sources include anaerobic biological processes in soil and water,

combustion and photochemical destruction of nitrogen compounds in the

stratosphere worldwide basis, natural emissions of NO are estimated at

approximately 5 x 108 tons per year. Major anthropogenic sources

include automobile exhaust, fossil fuel fired electric generating stations,

industrial boilers, incinerators, and home space heaters. All of these

sources are high temperature combustion processes which follow the

reaction:

N2 + O2= 2NO

This reaction is endothermic, which means that the equilibrium shifts to

the right at high temperatures and to the left at low temperatures.

Therefore, as the combustion temperature of a process increases, so will

be the amount of NO emitted. Background concentrations of NO are

approximately 0.5 ppb. Atmospheric levels of NO are highest during the

peak morning and evening hours. Emissions of NO are also greater in the

winter months since there is an increase in the use of heating fuels. NO

is a relatively non-irritating gas and is considered to pose no health

threat at ambient levels. It is rapidly oxidized to nitrogen dioxide, which

has a much higher toxicity.

Nitrogen dioxide: It is a gas with light yellowish orange colour at low

concentrations and reddish brown colour at high concentrations. It has a

pungent, irritating odor. It is relatively toxic and has a rapid oxidation

rate which makes it highly corrosive as well. The oxidation of NO to N02

follows the reaction:

2NO + O2 → 2N02

10

This reaction is slow at low atmospheric levels and accounts for about

25% of all NO conversion. The major NO conversion processes are

photochemical, involving hydrocarbons, ozone, aldehydes, carbon

monoxide, and other compounds. Background concentrations of NO2 are

approximately 0.5 ppb. Peak morning concentrations of NO are followed

several hours later by peak levels of NO2 produced by the chemical and

photo-chemical oxidation of the NO. Since the conversion of NO to NO2 is

related to solar intensity, more NO2 is produced on warm, sunny days.

1.2.5.3 Photochemical Oxidants

These are secondary pollutants which result from a series of complex

atmospheric reactions involving organic pollutants, NO, O2 and sunlight.

The main photochemical oxidants are ozone, NO2 and to a lesser extent,

peroxyacetyl nitrate.

Ozone (O3) is the most important and widely reported of the photo-

chemical oxidants. It is a bluish gas that is 1.6 times heavier than oxygen

and is normally found at elevated levels in the stratosphere where it

functions to absorb harmful ultraviolet radiation. Ground level ozone is

one of the major constituents of photochemical "smog" which is a

widespread, urban phenomenon. It is formed when nitrogen dioxide

absorbs ultraviolet light energy and dissociates into nitric oxide and an

oxygen atom;

NO2 + hv → O+NO

These oxygen atoms, for the most part, react with oxygen to form ozone:

O + O2 → O3

In addition, the oxygen atoms can react with certain hydrocarbons to

form free radical intermediates and various products such as

peroxyacetyl nitrate (PAN). Since photochemical oxidants are secondary

11

pollutants formed in the atmosphere as result of primary pollutants

reacting, their concentration in the atmosphere will vary proportionally to

the amount of hydrocarbons and NO2 in the air and the intensity of

sunlight. PAN is a very potent eye irritant in addition to being a strong

lung irritant like ozone. O3 is relatively insoluble in respiratory fluids and

can be transported into the pulmonary system where it can damage the

central and terminal pulmonary units such as the respiratory

bronchioles and alveolar ducts. Exposure in excess of ambient levels

affects lung function causing increased respiratory rates and decreased

lung capacity. Prologed low-level exposure may result in decreased lung

elasticity. Studies on micro-organisms, plants and tissue cultures

indicate that O3 is mutagenic, i.e., it can cause permanent, inheritable

changes in genes. Since mutagens and carcinogenes appear to be related,

it is possible that O3 is also carcinogenic.

1.2.5.4 Fly Ash

When any ash-containing fuel is burned fly ash is generated. It is

particularly troublesome in the case of pulverized coal. Everything else

being equal, the quantity of fly ash emitted varies with the ash content of

the coal. For this reason, coal cleaning or washing for ash reduction may

be regarded as a means of air pollution abatement. The problem of fly

ash is not different and the same principles apply that has been able to

govern the control of other types of particulate matter in stack emissions.

Millions of tons or more of fly ash per year is produced.

The disposal has been a problem. Considerable research has been carried

out to find uses for the material. Small quantities are used as a

constituent of Portland cement mixes.

• Removing NOx after combustion by reacting with isocyanic acid

(RCNO). It removes up to 99% NOx but it is yet to be

commercialized.

12

• Removing NOx after combustion in flue gas scrubbers. This would

remove 70-90% NOx but is expensive and has the problem of

sludge disposal.

1.3 SUMMARY

Air pollution is an atmospheric condition in which some substances are

present in such concentrations which affect the living beings and

property. There had been many air pollution episodes which have taken a

heavy toll of life. Bhopal gas tragedy is one of them. There are the

National Ambient Air Quality Standards (NAAQS) with which the

observed air quality parameters are compared. Primary pollutants are the

ones which are emitted from the source and secondary pollutants are

formed in the atmosphere by various combinations.

The suspended particulate matter ranges from 108 to 0.1 µm or smaller

and may of be of various types depending upon their size. Very small

particles are in Brownian movement. Chemical composition of particulate

matter varies depending on their origin. They could be formed from soil,

minerals, combustion smoke, insecticide dust, organic compounds. Some

of the particulate polycyclic organic matter may be carcinogenic. Trace

metals in air are of great health hazard.

Hydrocarbons are emitted naturally and by human activities.

Atmospheric hydrocarbons themselves have low toxicity but they play a

major role in the photochemical reactions leading to formation of

photochemical smog.

Carbon monoxide is formed during combustion, if O2 is insufficient. It

combines with smoker’s haemoglobin and increases the risk of angina

pectoris patients. CO2 is not a pollutant but increasing levels increase the

problem of global warming. SO2 changes to SO3 and to sulfuric acid mist

which may penetrate lungs and cause damage.

13

Oxides of nitrogen are formed from nitrogen at high temperatures. Nitric

oxide (NO) is converted to nitrogen dioxide (NO2) which takes part in

photochemical oxidation. Photochemical oxidants like O3, NO2, and PAN

form photochemical smog. Fly ash is emitted when ash containing fuel is

burnt especially the pulverized coal. Disposal of fly ash is a problem.

1.4 KEY WORDS

Air pollution : Atmospheric condition in which some

substances are present in such

concentration which affect various life

forms and materials.

Primary Pollutants : Pollutants which are emitted from the

source.

Secondary Pollutants : Harmful pollutants formed by the

reaction of two or more primary

pollutants in the air.

NAAQS : Standard limits recommended by the

Central Pollution Control Board for

individual air pollutants, the presence of

such pollutant beyond which amounts

cause of concern.

Hydrocarbons : Organic compounds of hydrogen and

carbon.

Suspended particulate matter: Particulate matter upto 10 µm which

remain suspended in the air.

Fly-ash : Ash formed by burning of the ash

containing fuel. It’s disposal is a

problem.

1.5 SELF ASSESSMENT QUESTIONS

1. Discuss the National Ambient Air Quality Standards.

14

2. What are primary and secondary pollutants? Give examples.

3. Discuss the important inorganic gases in the atmosphere that act

as pollutants.

4. Write a brief note on fly ash.

5. What is suspended particulate matters (SPM)? Name the different

types of SPM.

1.6 SUGGESTED READINGS

Kaushik, A and Kaushik CP (2004) : Perspectives in Environmental

Studies, New Age International Publishers, New Delhi.

Miller & Tyler Jr. 1999. Environmental Science : Working with the Earth,

7th edition. Wedsworth Publishing Company.

Murali Krishna KVSG (1995) : Air Pollution and Control.

Masters, Gilbert M (1994) Introduction to Environmental Engineering and

Science. Prentice-Hall of India- Private Ltd., New Delhi.

15

UNIT-II PGDEM-03

AIR POLLUTION: METEOROLOGY, DISPERSION, AUTOMOBILE POLLUTION AND AIR POLLUTION IMPACTS

Prof. C.P. Kaushik

STRUCTURE

2.0 OBJECTIVES

2.1 INTRODUCTION

2.2.1 METEOROLOGY

2.2.2 PLUME DISPERSION

2.2.3 AUTOMOBILE POLLUTION

2.2.4 EFFECTS OF AIR POLLUTANTS

2.2.4.1 Effects on Human Health

2.2.4.2 Effects on Vegetation

2.2.4.3 Effects on materials

2.2.4.4 Effects on buildings

2.3 SUMMARY

2.4 KEY WORDS

2.5 SELF ASSESSMENT QUESTIONS

2.6 SUGGESTED READINGS

2.0 OBJECTIVES

After reading this unit you would be able to :

1. Role of environmental conditions, environmental lapse rate,

adiabatic lapse rate, plume dispersion.

2. Various types of pollutants emitted by automobiles, their

composition, reasons for poor quality of emission.

3. Effects of air pollution on human health, systems of human body

affected by various pollutants, effects of air pollution on vegetation

and buildings.

1

2.1 INTRODUCTION

Meteorology of the place play a vital role in dispersion of air pollutants.

The plume follows particular path (shape) depending on adiabatic lapse

rate and environmental lapse rate. The extent of pollution near the point

source depends upon dispersion of pollutants.

Automobile pollution is of great concern in the developing countries like

India where the number of vehicles is on an increases. Various types of

vehicle fuels emit a variety of pollutants which affect human health,

vegetation and materials. Increase in number of diseases specially the

pulmonary diseases, in due to increase in air pollution. Plant life is also

affected by air pollution. Various types effects in the leaf leading to

necrosis affects photosynthesis and crop yield. Air pollution damages

materials like metals, buildings paints, dyes, rubber, paper etc. are

affected by air pollution. Various buildings and monuments in various

countries have been affected. In India the quality of the marble of Taj

Mahal is affected by air pollution.

2.2.1 METEOROLOGY

Various environmental factors like wind force, direction in which they are

blowing, temperature profile, availability of sunlight to cause

photochemical reactions, precipitation to clear the air determine the air

quality on day to day basis even if the emission in an area remains

relatively constant. Air quality therefore, depends upon dynamics of

atmosphere, the study of which is called meteorology.

Vertical dispersion of pollutants in the atmosphere is determined the

change of air temperature with altitude. If the physical forces acting on

air help to retain it at that elevation for some temperature profiles, the air

is stable. This discourages dispersion and dilution of pollutants.

The dispersion of a parcel of air depends upon the surrounding

2

environmental temperature. The decrease in temperature with increasing

altitude is called environmental-lapse rate (ELR). If the air parcel does

not exchange heat with the surrounding air, the decrease in temperature

with upward movement of air parcel because of its expansion is at a fixed

rate of 1°C/100 meters. This rate is called as adiabatic lapse rate (ALR).

These two factors determine dispersion of air pollutants, if the

temperature of a parcel of air is same as that of the surrounding air and

it is raised upwards it will cool at adiabatic lapse rate and may remain

denser than the surrounding air. It will try to sink. If the same parcel of

air is lowered, it will compress and will follow adiabatic lapse rate. Its

temperature may be more than the surrounding air. This will result in

upward movement of the parcel. This temperature profile corresponds to

stable atmosphere. The environmental lapse rate is called subadiabatic.

In other conditions the air parcel at the same temperature as that of

surrounding and is moving upwards its temperature is more than the

surrounding, it is buoyant and will try to rise further. If by moving

downwards its temperature remains less than the surrounding, it is

denser and will try to sink. The air is unstable and the environmental

lapse rate is called superadiabatic. Such conditions favour mixing and

dilution of pollutants.

In extreme case of atmospheric stability, upward movement of air is

hindered. It may result if a cold air mass passes under a warm air mass.

Such conditions ate called inversion and result in the build up of

pollution in the inversion layer and may cause severe health problems.

The severity of Bhopal Gas Episode was due to the occurrence of such

conditions in the winter night.

2.2.2 PLUME DISPERSION

'The shape of stack plume is a function of the vertical temperature and

wind profiles. From the plume shape the stability condition and the

3

dispersive capacity of atmosphere can be judged. The behaviour and

dispersion of a plume depend on the environmental lapse rate, (ELR). A

parcel of air released from a stack into the atmosphere follows the dry

adiabatic lapse rate (DALR). If the temperature attained by the parcel is

less than the surrounding environmental temperature, the parcel of air

will be denser and would not rise upwards in the warmer and lighter

atmosphere. Thus, inversion is the most unfavourable condition for the

dispersion of pollutants in atmosphere. Similarly, in superadiabatic

atmospheres the temperature in the environment would decrease at a

faster rate i.e. more than DALR whereas the plume temperature would be

decreasing at the standard rate of 1°C/100 m. Due to this, a plume or

parcel of Air released from a stack is at a higher temperature than its

surrounding environmental temperature. Thus, the parcel of air owing to

its lower density is buoyant and continuously moves upwards. Such

atmosphere is called unstable atmosphere in which the pollutant

dispersion is good and ground level concentrations are less. The plume

behaviour is shown in Figure-1. The plume behaviour in a given

environment may be different for stacks of different heights.

Looping

Coning

Fanning

Lofting

Fumigation

Fig. 1 : Various shapes of plume

4

• Looping: It is associated with turbulent air during warm seasons

with clear skies. It occurs under super-adiabatic conditions and

during day time with clear or partly cloudy skies and intense solar

heating. In this, irregular loops dissipate in patches and relatively

rapidly with distance. It occurs due to light to moderate wind

speeds on a hot summer afternoon when large scale thermal eddies

(small whirls) are present. These eddies carry portions of the plume

to the ground level for short time periods, carrying momentary high

surface concentration of pollutant near stack. Though looping

occurs in unstable atmospheres which are favourable for thorough

mixing higher stacks may be needed to prevent premature contact

with the ground.

• Coning: When the ambient lapse rate is sub-adiabatic the

atmosphere is neutral (or) slightly stable. Under such conditions,

there is limited vertical mixing and the probability of air pollution

problems in the area increases. The typical plume in such situation

is called coning. The visible plume is cone shaped roughly 10

degrees with a horizontal axis. It dissipates further down wind than

a looping plume. In this, small scale mechanical turbulence

dominates since the thermal heating effect is much lower than in

the case of plumes. Coning occurs when skies are overcast during

either the day or night with moderate to strong winds. Unlike in

looping in coning, the major part of the pollutant concentration is

carried fairly far downwind in significant amounts before reaching

the ground level. This is a specially good condition for estimating

pollutant dispersion by the diffusion models. Dispersion is slower

than looping and the pollutant touches at a large distance.

• Fanning: A 'fanning plume' occurs in the presence of large negative

lapse rates (inversion and isothermal lapse rate), so that a strong

surface inversion takes place at a considerable distance above the

5

stack height. The atmosphere is extremely stable, with very little

turbulence and light winds. The typical occurrence of the plume is

at night and in early morning conditions when the earth is cooled

by outgoing radiation. A fanning plume may appear as a narrow

horizontal fan without any vertical spreading for several kilometers

downwind. If the effluent is warm, plume rises slowly and then

drifts horizontally. The dispersion of plume is very slow, and

concentration aloft high - at relatively great distance downwind. A

small probability of ground contact exists, though turbulence can

result in considerable ground contact.

• Lofting: It prevails in the late afternoon and early evening under

clear skies. In the evening (sun sets) radiation from the surface

leads to an inversion layer near ground level. As the inversion layer

deepens, a lofting plume will change to a fanning plume. Due to the

inversion, adiabatic lapse rate forms at stack top which makes the

lower layer stable and the upper layer neutral or unstable. The

plume is in the form of loops or cone with well defined bottom and

diffuses to top. In the upper layer, the winds are of moderate, and

considerable turbulence and they have very little influence in the

layer below. In lofting probability of ground contact is small unless

inversion layer is shallow. It is considered to be the best condition

for dispersion since pollutants are dispersed in upper air with

small probability of ground contact.

• Fumigation: 'Fumigation plumes occur when a stable layer of air

lies a short distance above the release point of the plume and an

unstable air layer lies below the plume. It occurs during changes

from inversion to normal condition and also with sea breeze in late

morning or early afternoon. It stays temporarily for maximum 30

minutes except in case of sea- breeze conditions, in which case it

stays for several hours. The morning sun heats the ground, which

6

in turn leads to the development of a negative temperature gradient

from the ground upward. Once the newly formed unstable layer

reaches the height of the stack, large concentrations of stack gas

will be carried downwind to the surface. The winds are light to

moderate aloft and light below, but thermal turbulence is observed

in lower layer only. The ground level concentrations are high

especially when plume his stagnated aloft. Fumigation is formed

usually under clear skies and light winds, and is more prevalent in

the summer. It usually starts when a fanning plume breaks up into

a looping plume.

• Trapping: It occurs in a stable atmosphere, both above and below

stack with an unstable atmosphere in between the two inversion

layers and can diffuse only in the limited vertical height. It may

occur at any time of the day in any season. If associated with

subsidence inversion it may persist for months as in Los Angeles

and if associated with warm frontal inversions it lasts for less than-

a day. It is probably one of the worst pollution situations.

2.2.3 AUTOMOBILE POLLUTION

Urban growth has resulted in tremendous increase in automobile

pollution. About 60% of the atmospheric pollution in urban areas is

contributed by automobiles. The problem becomes more alarming in view

of the fact that the number of automobiles is increasing day by day. Due

to unprecedented growth of human population as well due to modern life

style, this increase, in vehicular population is occurring. The number of

two, three and four wheelers has increased enormously. The number of 4

wheelers in increasing by 10% each year while the number of 2-wheelers

and 3-wheelers in increasing by 20-25%. The developed, nations have

still more automobile pollution problem where every family has a number

of cars one for each member.

7

Vehicles playing is major metropolitan cities are estimated to account for

a large proportion of air pollution due to various pollutants:

Types of Pollutant Contribution (%)

Carbon monoxide 80%

Hydrocarbons 50%

Oxides of Nitrogen 30-40%

Lead >90%

Vehicular emissions include unburned hydrocarbons, carbon monoxide

(CO), oxides of Nitrogen (NOx), oxides of Sulphur (SOx), particulate

matter, lead and its derivatives etc.

Based on their origin, these pollutants can be grouped into three

categories as discussed below:

A. Exhaust Emissions

Complete oxidation of hydrocarbon fuel, yields only carbon dioxide and

water as the products of chemical combination. When air is used as the

source of the oxygen required for combustion, some of the oxygen and

nitrogen combine to from nitric oxide. Under the conditions of

combustion in an internal combustion engine, other products are also

formed. These include carbon monoxide, hydrogen and partially oxidized

materials primarily in the aldehyde family. Some of the fuel is chemically

rearranged by cracking or synthesizing reactions, both absolute and

relative concentrations of combustion products are influenced by

numerous factors. Some of the prominent factors include air fuel ratio,

ignition timing, absolute charge density combustion chamber geometry

and variable engine parameters such as speed, load and engine

temperature.

Carbonmonoxide: Ideally, gasoline engines could be made to operate

with CO levels near zero. Although the zero limit is not a reasonable

8

target less than 1/2% CO is a reasonable goal. This low level of CO

emission can be achieved only some sacrifice in auto-deriveability or

engine performance. Typically, concentrations of CO in emissions are

high during the engine idle mode and decrease as engine speed is

increased outside of the idle ranges. About 2 ppm of CO being a desirable

value; many cities all-over the world including Bombay, Calcutta and

Delhi are suffering from high CO concentrations of 20-70 ppm. CO is

emitted mostly by vehicles run on petrol like most of the cars, three

wheelers and two-wheelers. In Bombay alone, nearly 300 tonnes of

carbon-monoxide are released from vehicular exhaust everyday.

Unburned Hydrocarbons: Concentrations of unburned hydrocarbons are

influenced by air-fuel ratio in the same manner as; CO is influenced i.e.,

lowest-emission levels are associated with an air-fuel ratio near

stoichiometric. Further as with CO, higher levels of hydrocarbon-

emissions are associated with idle and low-speed operation. Exceptionally

high values of hydrocarbons in the exhaust, usually, are indicative of

misfiring:

Oxides of Nitrogen : This pollutant is generated first as nitric-oxide (NO)

with conversion to nitrogen dioxide (NO2) subsequent to the combustion

event. Other nitrogen oxides are involved in much lesser amounts. The

aggregate of the variable mixture including NO and NO2 is commonly

designated as NOx. Factors that tend to increase combustion

temperature and to increase oxygen availability also tend to increase NOx

emissions. Air-fuel ratio is found to 'be the dominant influence upon NOx

emissions and the highest emissions are associated with air-fuel ratios

slightly on the lean side of stoichiometric. The other factors relevant in

NOx generation engine compression ratio, spark timing and intake air

temperature and humidity.

Particulate Matter: Exhaust emissions produce large numbers of

9

extremely fine particles with approximately 70% by count in the size

range of 0.02-0.06 µm. These particulate materials consist of both

inorganic compounds and organic compounds of high molecular weight.

The most significant fractions of automotive particulate emissions used

to be lead compounds before these were banned, resulting from the use

of tetraethyl lead as a fuel additive to provide the anti-knock

characteristics necessary for high-compression engines.

Lead and other Heavy Metals: Combustion of gasoline containing lead

additives was a primary source of lead in urban atmosphere. Tetraethyl

lead is added to petrol to improve its antiknock quality and after

combustion, lead was released through the exhaust Lead is also emitted

through petrol tanks and while fuelling in the petrol bunks. Lead is

highly toxic even at trace levels. Children should not be exposed to more

than 100-150 µm of Pb per day. Infact many urban children ingest upto

200 µm of Pb everyday. Similarly persons working in petrol bunks are

prone to 'occupational diseases' caused by lead ingestion.

B. Evaporative Emissions

10 to 30% of the hydrocarbons in vehicular emissions belong to this

category. The estimate is uncertain because techniques for measuring

evaporative emissions involve large uncertainities. However, even at the

lower limit of the estimate, these losses are significant. Fuel tank losses

consist primarily, of the more volatile fractions of gasoline displaced from

the vapor space above the liquid fuel in the gas tank. Depending upon

the direction of temperature changes, tank fill and tank agitation, the

vapors may be discharged at any time, with vehicle either operating or

stationary.

C. Crank Case blow-by

Crankcase blow-by accounts for about one-fifth of the hydrocarbons in

10

all vehicle emissions. Vehicles with badly worn engines may discharge

blow-by in much larger quantity to account for upto one-third or more of

the total. Experimental evidence fully establishes that the blow-by gases

are primarily (i.e. about 85%) carburetted fuel air mixture that flows past

the piston during the compression stroke and prior to the passage of

flame through the mass.

2.2.4 EFFECTS OF AIR POLLUTANTS

The effects-of the main air pollutants namely CO, SOx, NOx, oxidants,

Hydrocarbons and particulates on man, material and vegetation are

described in detail of follows:

2.2.4.1 Impact on Human Health

Carbon Monoxide (CO) : The sources of CO are both natural and

anthropogenic. Oxidation of methane gas from decaying vegetation,

human metabolism and gasoline powered internal combustion engines

lead to CO emission. Carbon-monoxide, present at ambient levels, has

little effects on property, vegetation or materials. ‘CO’, when inhaled,

passes through the lungs and diffuses directly into the blood stream

where it combines with the red blood pigment called hemoglobin forming

carboxyhemoglobin, COHb.

The affinity of carbon monoxide for hemoglobin is 210 times greater than

that of oxygen and as a result amount of hemoglobin available for

carrying oxygen to body tissue is considerably reduced. The body tissues

are thus deprived of their oxygen supply. Heart patients may lack

sufficient cardiac reserve to compensate. Patients with angina pectoris

require less exertion to induce chest pain. Carbon-monoxide

concentrations are especially high in congested urban areas where traffic

is heavy and slow moving. A person trapped in traffic at such a location

for an hour would show a COHb blood level close to 2-3 percent. This

11

exposure would affect the central nervous system, impairing a person's

time interval discrimination, brightless discrimination and other psycho-

motor function. The absorption of CO by the human system increases

with its concentration, exposure time and the activity being performed.

The chronic effects of CO are not full known but they may induce heart

and respiratory disorders. While CO itself has not been found to be

carcinogenic, there is concern that it may increase the carcinogenic effect

of other air pollutants by inhibiting the mucociliary clearance mechanism

in the lungs. 1-2% of COHb levels have an evident effect on the

behavioral performance of the humans. If COHb levels exceed 5%,

cardiac and pulmonary functional changes are observed. 10% and more

COHb levels may cause headaches, fatigue, drowsiness, coma,

respiratory failure and death.

Oxides of Sulfur: The burning of fossil fuels contributes more than 80

percent of anthropogenic S02 missions. Fuel combustions in stationary

sources and industrial processes are the principal contributors of SOx.

Combination of these oxides with water (H2S03 and H2S04 and the salts

derived from these acids) when combined with other elements are well-

known at atmospheric pollutants. Intense irritation and reduction of

visibility have also been recorded from epidemiological studies pertaining

to sulfur oxides. Sulfur dioxide (S02) and sulfate salts tend to irritate the

mucous membrane of the respiratory tract and expedites the

development of chronic respiratory diseases, particularly bronchitis and

pulmonary emphysema.

Oxides of Nitrogen : Some oxides of nitrogen are produced naturally.

Small concentrations of NOx produced in the upper atmosphere by solar

radiation reach the lower atmosphere through downward diffusion. Small

amounts of NOx are produced by lightning and forest fires. Bacterial

decomposition of organic matter also releases NOx into the atmosphere.

The implementation of more stringent controls for carbon monoxide and

12

hydrocarbons resulted in the increased emissions of NOx. The greatest

significance of NO is related to its tendency to undergo oxidation to NO2.

Affinity of hemoglobin for absorbing, NO2 is 3,00,000 times that for O2.

This affinity drastically reduces the O2 carrying capacity of the blood. NO

is a relatively inert gas and only moderately toxic. NO2 irritates the alveoli

of the lungs. The response of the human respiratory system to long-term

exposure to nitrogen dioxide depends upon the concentration of NO2. The

olfactory threshold value of NO2 is about 225 µg/m3 (0.12 ppm).

Exposure, to 9.4 mg/m3 for 10 minutes has produced transient increase

in air way resistance and occupational exposure to 162 mg/m3 for 30

minutes has produced pulmonary oedema. NO2 is the basic pulmonary

irritant. Long term exposure, to NO2 at concentrations between 100 and

200 µm3 and mean suspended nitrate level at 3.8 µg/m3 results in acute

respiratory disease. It has been stated that 95 percent of nitrogen oxides

inhaled remain in the body where they can also produce mutations in

cells. Nitrogen oxides cause lung tissues to become leathery and brittle

and may cause lung cancer.

Oxidants: Ozone contributes about 90% of the total oxidants.

Concentrations of ozone exceeding 200µg/m3 will cause eye irritation.

The threshold for both nasal and throat irritation is set higher at 0.3 ppm

over an 8-hour period. Some states permit 0.15 ppm for 1-hour periods.

When the level of ozone in the ambient air is more than 0.7 ppm over a

20 to 90 minutes period, coughing, checking and severe fatigue will

result. Exposure to oxidants causes severe chest pains, headache,

damage to red blood cells, loss of coordination and difficulty in

articulation. Other important oxidants are nascent oxygen, '0'; excited

molecular oxygen, O2; peroxy acetyl nitrate, PAN; peroxy propionyl

nitrate, PPN; peroxy butyl nitrate, PBN nitrogen dioxide, NO2 and

hydrogen peroxide (H2O2). The desirable ambient air levels of

photochemical oxidants are 240 µg/m3 for 1 hour duration.

13

Hydrocarbons: Hydrocarbons are evolved into the atmosphere from

crankcase of automobile, various refrigerants, decay of several organic

matters and from trees. Methane is the major naturally occurring

hydrocarbon emitted into the atmosphere. Human activities contribute

nearly 20% of the hydrocarbons emitted to the atmosphere every year.

Animals contribute about 80-85 million tonnes of methane in the

atmosphere every year. The hydrocarbons on reacting with nitric oxide

and sunlight form photochemical smog which causes irritation to eye end

decrease in visibility. Formaldehyde and peroxy acetyl nitrate (even at 1

ppm) are eye irritants. PAN also causes plant damage. The oxidation

reactions accompanied by formation of aerosols or haze also result in eye

irritation and plant damage. Hydrocarbons at high concentrations have

carcinogenic effects on lungs. They cause swelling when they enter the

lungs. Aromatic hydrocarbons are more dangerous than a cyclic and

alicyclic hydrocarbons. The inhalation of their vapours cause acute

irritation to the mucous membrane. Excess of hydrocarbon increases

mucous secretion as a result of which respiratory tracks are blocked and

man coughs regularly. Because of continuous cough much pressure is

caused on the trachea of lungs due to which the lining membrane of

alveoli bursts and very small area is left for exchange of oxygen and

carbon dioxide, Benzopyrene, which is present as trace amounts in

tobacco, charcoal, boiler stacks and gasoline exhausts etc. is a

dangerous cancer inducing hydrocarbon pollutant. Methane also is a

severe gas pollutant and occurs in air by volume of 0.0002 percent: Its

higher levels in absence of oxygen create narcotic effects on human

beings. A group of hydrocarbons, especially the carcinogenic

hydrocarbons, cause cancer in man and animal affecting DNA and cell

growth.

14

TABLE-I: HAZARDS OF CARCINOGENIC HYDROCARBONS

Sr. No. Compound Health Hazards

1. Benzene Bladder cancer

2. Naphthylamine Cancer in urinary bladder

3. Bichloromethyl ether Lung cancer

4. Ethylene dichloride Stomach, spleen and lung cancer,

5. Vinyl chloride Liver cancer

6. Ethyleneamine Cancer

7 . Propiolacetone Potential carcinogen

8. Naphthylamine Bladder cancer

9. Nitrophenol Bladder cancer

10. 3-3' dichlorobenzidine Cancer

Particulates : The effect of particulates on human beings depends

mainly on their size and characteristics. Size is one of the most important

physical parameters of particulates. Particle sizes are measured in

micrometers. Particle sizes larger than 50 µm can be seen with unaided

eye. Particulates smaller than 1 µm do not tend to settle out rapidly.

Settling is the major natural self-cleansing process for the removal of

particulates from atmosphere. Particulates can generally be classified as

suspended or settleable. Suspended particulates vary in size from less

than 1 µm to nearly 20 µm. Settleable particles or dust, are larger and

heavier and settle out close to their sources. They are generally greater

than 10 µm in size. Particulates greater in size (over 10 µm) are easily

removed by hairs at the front of nose.

Generally, coarse dusts, fly ash etc. are greater in size and seldom enter

the human system. Particulates with size range in between 2 to 10 µm

like fumes, dusts and smoke particles, are removed as movement of cilia

sweeps mucous upward, carrying particles from wind pipe to mouth

where they are swallowed. If the size of the particulates is less than 2 µm

(like aerosols and fumes) they will enter the lungs easily. Lymphocytes

15

and phagocytes in the lung attack some submicron particles, but all of

them cannot be removed effectively. Similarly, there is a great variation in

the chemical composition of the particulates found in the atmosphere.

Atmospheric particulates contain both organic components like phenols,

organic acids and alcohols and inorganic components like dusts. The

biological particles include protozoa, bacteria, viruses, fungi, spores,

pollens and algae. Their life time is very small due to lack of nutrients

and presence of UV rays from sun. However certain bacteria and fungi

can survive for longer periods.

Effects of Particulates : The success or failure of respiratory defense

system depends, in part upon the size of the particulates inhaled and the

depth of their penetration into the respiratory tract. About 40 percent of

the particles 1-2 µm in size are retained in bronchioles and alveoli

Particles ranging in size from 0.25 to 1 µm show a decrease in retention.

2.2.4.2 Air Pollution Effects on Vegetation

The most obvious damage caused by air pollutants to vegetation occurs

in leaf structure. The surface of leaf is covered by a waxy layer known as

cuticle. Between the waxy layers, epidermis is present, which is a single

layer of cells forming the surface skin of the leaf. The epidermis protects

the inner tissues from excessive moisture loss and prevents the

admission of CO2 and oxygen to these internal tissues. The leaf surface

has a large number of openings called the stomata. Guard cells protect

the stomata and also control the opening and closing of stomata. A

typical plant cell has three components-the cell wall, the protoplasm and

the non-living inclusions within the cell. Because the cell wall is

extremely thin during the formative stage, new growth is very much

susceptible to air pollution damage. The protoplasm is composed of

several chemical compounds, water and the central nucleus which

contains the hereditary and reproductive mechanism. The leaf also

16

contains the chloroplasts, which are the key structures in the

photosynthesis process of food manufacture in the green plant. These

plant inclusions are the store house for food and waste material. A cross

section of a leaf shows four principal layers, the upper epidermal cells,

the palisade parenchyma, the spongy parenchyma and the lower

epidermal cells. The excess oxygen generated in this process escapes

from the plant into the atmosphere and helps to purify the air. Many of

the atmospheric pollutants act as phytotoxicants (plant damaging

substances) and result in various injuries to the plants:

• Bifacial Necrosis: Tissues are killed on both upper and lower

surfaces of the leaf.

• Pigmented Lesions : Dark brown, black, purple or red spots

appear on the leaf surface.

• Epinasty : The rapid growth of the upper side of the leaves,

causing the leaf blade to curl under.

• Acute injury: Results from short term exposure to high

concentrations of pollutants. A severe visible damage to leaf tissues

is often associated with plasmolysis and tissue collapse.

• Chronic Injury: Resulting from long-term exposure, to low levels of

pollutants and often, shows up as a colour change or chlorosis

because of destruction of chlorophyll with no apparent cell damage.

• Chlorosis: The loss of the green plant pigment chlorophyll is called

chlorosis. The loss of chlorophyll results in yellow pattern.

Chlorosis indicates a deficiency in some nutrient required by the

plant.

• Abscission : Leaf abscission is the dropping of leaves. This will

decrease the life of the plant.

17

• Necrosis: It is the killing or collapse of the plant tissue. Tissue

injured by phytotoxicants often has a characteristic colour. For

example, bleaching is associated with SO2, yellowing with

ammonia, browning with fluoride and silvering or bronzing of

under surfaces of some leaves with PAN.

2.2.4.3 Air Pollution Effects on Materials

Air pollution damage to property is a very important economic aspect of

pollution. Air pollution damage to property covers a wide range of

corrosion of metals, soiling and eroding of building surfaces, fading of

dyed materials, rubber cracking etc. The processes responsible for the

effects of air pollution on materials are:

• Abrasion: Solid particles of considerable size travelling at higher

speeds cause abrasive action, Large sharp edged particles

embedded in fabrics can accelerate wear.

• Chemical Action : Some air pollutants react directly and

irreversibly with materials to cause deterioration. SO2 bleaches

marble, hydrogen sulfide tarnishes silver and acidic mists cause

etching of metallic surfaces.

• Absorption: Certain materials absorb some pollutants and get

damaged when the pollutants undergo chemical changes. SO2

absorbed by leather will be converted to sulfuric acid, which

deteriorates leather.

• Corrosion : Action of air pollutants facilitated by the presence of

moisture causes corrosion. The atmospheric deterioration of

ferrous metal is due to corrosion by an electrochemical process.

• Deposition and Removal : Solid and liquid particles deposited on

surface may damage the material by spoiling its appearance.

18

2.2.4.4 Effects of Air Pollution on Buildings

Polluted air containing oxides of sulfur and nitrogen and particulates,

deteriorate building materials and may ultimately result in a loss in

structural integrity. When buildings dating from antiquity and structures

of great artistic and historic values are disfigured the loss is irreparable.

Less than 100 years of exposure to air pollutants in London has done

more damage to the Cleopatra's Needle than what was caused by nature

during 3500 years in the dry atmosphere of Egypt. The miraculous and

historical monuments built by long years of hard labour are losing their

faces. This shows how materialistic man has become, in years where he

is giving importance to industrial production even at the cost of the art

treasures brought up by his ancestors. Disintegration of stone caused

largely by the expansion of iron by corrosion had badly damaged the

houses of parliament in London in 1920. The Parthenon of Athens, the

Coliseum and Arch of Titus in Rome and the San Marco Basilica in

Venice are fast deteriorating. The situation in Florence, Italy has been

described as disastrous. The massive twin aspired cologne cathedral, the

most magnificent church building of German High Gothic era is facing

the threat of corrosion. Similar is the case in Japan wherein most of the

industrial areas, the century-old shrines and temples are facing the

threat. Taj Mahal at Agra, in India, a miracle in marble is facing the grave

danger from pollution caused by existing foundries, power houses,

railway yards and other industrial units. The problem now seems to be

more aggravated because of the commissioning of the Mathura refinery,

within 30 km. range of the priceless monument which is emitting SO2 in

the air and the wind direction is such that Taj at Agra is under direct

corrosion by the acidic fumes. Some alternative solutions must be

considered. One of the methods that may prove successful is to transport

the corrosive gases form the refinery through a set of anticorrosive

pipelines bye passing Agra, purify the gases and release the emission into

atmosphere at a safest place on the down-wind side of Taj Mahal.

19

Plantation of trees around Taj will give a cover which may absorb atleast

a part of the pollution. The renowned temple of Sri Channakeshava at

Belur (Hasan district, Karnataka State) India is threatened with a similar

hazard. A plywood factory located close to the temple emits soot-laden

fumes which get deposited on the sculptures in the temple and discolour

the surface, inside and outside. Jagannath temple, at Puri and the

Konark Sun temple situated on the East Coast of India are badly hit by

particulates present in air. The abrasive action of the sea sprays is

threatening the longevity of these temples. The Statue of Liberty is also

badly affected by air pollution. Sensitive art objects displayed inside

buildings can be placed in hermetically sealed containers. Air

conditioning can also be used as a protective measure. The sides of books

kept in closely packed rows with restricted air circulation remain in good

conditions for a much longer period, than their exposed backs.

Bacteriocides may be used to protect stones as some bacteria convert

atmospheric SO2 to sulfuric acid which they use as a digestive fluid in

attacking the carbonate stone. Thus air pollution can result in serious

health impacts to humans, plants as well as affect and degrade various

types of materials and buildings.

2.3 SUMMARY

Study of dynamics of atmosphere is called meteorology. Atmospheric

conditions prevailing at a time determine air quality. Decrease in

temperature with increasing altitude is called environmental lapse rate

(ELR). Air parcel, if it despoil exchange heat with the surrounding will

experience decrease of 1°C/100 m due to expansion. This is called

adiabatic lapse rate (ALR). ELR and ALR will determine the dispersion of

air pollutants. In relation to prevailing environmental conditions the

plume will experience. Various shaped like looping, coning, fanning,

lofting, fumigation and trapping.

20

Automobiles contribute to urban air pollution to a great extent.

Hydrocarbons, Co, NOx, SOx and particulate matter are the major

pollutants in the vehicular exhaust of these various pollutants CO forms

about 80% of the total exhaust. Petrol driven vehicles contribute more

CO. The concentration of unburned hydrocarbons are influenced by air-

fuel ratio and is lowest near the stiochiometric ratio.

NO is generated first due to oxidation of nitrogen which changes into

NO2. Mixture of oxides of nitrogen is represented as NOx. Higher

emission of NOx results from the air-fuel ratio on the lean side of the

stiochiometric ratio, enquire compression ratio, spark timing and intake

air temperature and humidity. 70% of particulate matter is in the range

of 0.02 – 0.06 µm. It consists of both organic and inorganic compounds

with high molecular weight. Lead used to form a significant part in the

leaded petrol.

Hydrocarbons that are emitted due to evaporation form 10 to 30% of the

hydrocarbons of the vehicular emission, and 1/5 by the crank case blow

by. Air pollutants have adverse effects on the living beings and materials.

CO combines with haemoglobin (210 times more than oxygen) and

causes problem for people suffering from angina pectoris. Chronic effect

of CO may result in heart and respiratory problems. It may increase the

carcinogenic effects of other pollutants. Symptoms associated with CO

exposure are headache, fatigue, drowsiness, coma and respiratory failure

and death.

Oxides of sulfur may cause intense irritation and reduction of visibility.

Exposure irritates mucous membrane of the respiratory tract and chronic

respiratory diseases like bronchitis and emphysema may develop. Oxides of

nitrogen adversely affect health. NO2 is absorbed by haemoglobin much

more than O2. NO2 irritates the alveoli and lungs. High concentration and

occupational exposure may produce pulmonary oedema.

21

Oxidants like O3 may cause coughing, and severe fatigue, severe chest

pain, headache, damage to RBC, loss of co-ordination and difficulty in

articulation. Hydrocarbons result in eye irritation, lung swelling and

plant damage. May have carcinogenic effects at high concentrations. May

result in excess mucous secretion. Particular matter may carry other

pollutants absorbed on them and enter the respiratory system.

Various pollutants affect the plants by causing injuries. Necrosis may of

the tissue may be on both the sides of the leaf, lesions on the leaf

surface, plasmolysis and tissue collapse. Pollutants may destroy

chlorophyll, result in dropping of leaves. Materials are also affected by

pollutants by causing corrosion of metals, erosion of the building

materials, fading of dyed materials, cracking of rubber.

Various buildings like in Egypt, Athens, Rome, Venice, Italy, India etc.

have been affected.

2.4 KEY WORDS

Meteorology : Study of dynamics of atmosphere

ELR : Decrease in temperature with increase in

altitude is called Environmental Lapse Rate

(ELR).

ALR : Decrease in temperature in the air parcel in

upward movement became of expansion. It is

1°C/100 meters.

Plume Dispersion : Movement of stack plume depending upon

vertical temperature and wind profile.

Chronic Bronchitis : Persistent inflammation and damage to the

cell lining the bronchi and bronchides

causing building up of mucus, painful,

coughing and shortness of breath.

Emphysema : Irreversible damage to air sacs alveoli leading

22

to abnormal dilation of air spaces, loss of

lung elasticity and acute shortness of breath.

Epinasty : The rapid growth of the upper side of the

leaves, causing the leaf blade to curl under.

2.5 SELF ASSESSMENT QUESTIONS

1. Define adiabatic and environmental lapse rate.

2. Discuss Sub adiabatic and Superadiabatic conditions.

3. Discuss various types of plumes in relation to environmental

conditions.

4. Write a short note on automobile pollution.

5. Discuss the major effects of atmospheric pollutants on human

health.

6. Discuss the impact of air pollutants on plants.

2.6 SUGGESTED READINGS

Kaushik, A and Kaushik CP (2004) : Perspectives in Environmental

Studies, New Age International Publishers, New Delhi.

Miller & Tyler Jr. 1999. Environmental Science : Working with the Earth,

7th edition. Wedsworth Publishing Company.

Murali Krishna KVSG (1995) : Air Pollution and Control.

Masters, Gilbert M (1994) Introduction to Environmental Engineering and

Science. Prentice-Hall of India- Private Ltd., New Delhi.

23

Unit-III PGDEM-03

Noise Pollution

Dr. Krishan Kumar

STRUCTURE

1.0 Objectives

1.1 Wave Motion

1.2 Sound Waves

1.3 Audible, Infrasonic and Ultrasonic sound

1.4 Definition of Noise

1.5 Sound Pressure Level – The Decibel Scale

1.6 Sources of Noise

1.7 Measurement of Noise

1.8 Indices of Noise Pollution

1.9 Standards of Noise Pollution

1.10 Summary

1.11 Key words

1.12 Review Questions

1.13 Suggested Readings

1.0 Objectives

After studying this unit, you will be able to understand:

• What is the nature of sound waves?

• The concept of noise and the sound pressure level

• How do we measure noise?

• What are various parameters/indices of noise pollution in which standards

of noise pollution are often expressed?

1.1 Wave Motion

We are everyday exposed to sounds of different kinds. Our ears are able to characterize a

sound on the basis of its properties. This ability allows us to discriminate between

different kinds of sounds. What makes these sounds so different from each other? To

know this, we first must understand wave motion. In the following section, we shall

introduce our readers to the fundamentals of wave motion.

What is a wave?

Well a wave is a perturbation/disturbance that travels onwards through a medium due to

the periodic motion of its particles from their mean position. A medium must possess

three important properties for the propagation of wave motion through it : (i) elasticity so

that it tries to return to its original position after being disturbed; (ii) inertia so as to be

able to store up energy and (iii) small frictional resistance so that there is very little

damping of the oscillating particles of the medium.

Based upon the manner in which particles oscillate about their mean position, waves can

be classified into two distinct categories – (i) transverse waves and (ii) longitudinal

waves.

Transverse Waves are the one in which particles of the medium oscillate simple

harmonically up and down about their mean position at right angles to the direction of

propagation of wave. This type of wave motion travels in the form of crests and troughs,

e.g. waves generated in a pond of water when a stone/pebble is thrown into it.

Longitudinal Waves are the one in which the particles oscillate simple harmonically to

an fro about their mean position along or parallel to the direction of propagation of wave.

This type of wave travels in the form of compressions (or condensations) and

rarefactions, e.g. waves produced in air by a source of sound.

To further develop our concepts about wave motion, it is relevant here to define certain

terms related to it.

Wavelength (λλλλ) – It is defined as the distance between two nearest particles of the

medium in the same phase, i.e. the distance between centers of two nearest crests or

troughs in case of transverse waves (fig. ) or that between two nearest condensations and

rarefactions in case of longitudinal waves. Alternatively, it may be defined as the distance

traveled by the wave during the time particles of the medium complete one full

oscillation.

Time Period – The time taken by the wave to complete one full oscillation/cycle is

called its time period. It is reciprocal of frequency (νννν) which means the number of

oscillations/cycles occurring per second.

Wave Velocity (v) – This is the distance traveled by the wave in one second. If λ is the

wavelength of the wave and ν its frequency, then the distance traveled by the wave in one

second is equal to νλ. Thus, the wave velocity may be related to the wavelength and

frequency of the wave by the following expression:

v = νλ

Finally, certain clarifications need to be given regarding wave motion to remove any

doubts from reader’s minds.

• A wave is only a disturbance or a condition that travels through the medium. It

does not involve transfer of any part of the medium from one place to the other.

• Each particle of the medium receives the disturbance a little later than its

predecessor, repeats its movements and passes the disturbance on to the next

succeeding particle. This means that there is a definite phase lag between one

particle and the next i.e. two adjacent particles do not reach their mean and

extreme positions at the same time.

• The velocity with which particles of the medium oscillate is entirely different

from the velocity of the wave.

1.2 Sound Waves

Sound waves are longitudinal in nature and thus travel in the form of condensations

(compressions) and rarefactions in the medium. To understand how a sound wave travels

in a medium, let us consider a vibrating tuning fork (fig. 1.1) whose two prongs move to

and fro about their mean position. As the prongs move to the right of their mean position,

they compress the air in their immediate neighborhood, which in turn, compress the

layers next to them due to the tendency of the medium to regain its original volume

because of its volume elasticity. Therefore, a pulse of compression travels onwards. As

the prongs move backwards to the left of their mean position, the air to the right gets

more space and expands thus producing a rarefaction. Again due to the property of

volume elasticity possessed by the medium, the rarefaction produced also travels towards

the right. Thus, as the tuning fork vibrates, it generates an alternating pattern of

compressions and rarefactions, which travels through the medium. This constitutes what

we call as a sound wave.

Fig. 1.1 Sound wave emission from a tuning fork

So, a sound wave is basically a pressure perturbation that travels through a medium

whose particles oscillate in a to and fro motion along the direction in which the

perturbation travels. During compressions, particles of the medium experience a push in

the positive direction (i.e. the direction in which wave travels) and are closer to each

other. For this reason, compressions are regions of higher pressure. On the contrary,

particles of the medium experience a pull in the negative direction (i.e. opposite to the

direction of wave travel) during a rarefaction and hence are farther apart from each other.

As a result, rarefactions are regions of lower pressure. Mathematically, the sound

pressure at any point (or at any instant of time) may be expressed by the following

equation:

Pt = P0 sin(wt-φ) [N/m2

or Pa] ……………….(1.1)

Where,

P0 = amplitude of sound pressure (N/m2)

t = time (s)

w = 2πf, angular frequency (rad/s)

f = frequency of oscillation (Hz)

φ = phase difference (dependent on initial conditions) (rad)

From the above equation, it may be inferred that two sound waves may be different in

terms of their frequency (or wavelength), amplitude and phase angle. In real life

situations, the sound field at a given point is a combination of sound waves which are

different from each other in all the above aspects.

1.3 Audible, Infrasonic and Ultrasonic Sound

Are we able to hear all the sounds that are incident upon a point. Well, not necessarily.

Our ears are able to hear sounds only within a certain frequency interval. This interval

starts from 20Hz and ends at 20,000Hz for a normal healthy human ear. This frequency

interval is called the audible range of sound frequencies. Even within this range, our ear

is not equally sensitive to all the frequencies. It is less sensitive at the extremes and more

sensitive in the middle of the audible range. Sounds having frequencies less than 20Hz

are called the infrasonic sounds while those having frequencies greater than 20,000Hz are

called the ultrasonic sounds. Our ear is not able to detect sounds outside the audible

range. However, many animals are able to hear sounds belonging to a much wider

frequency interval. For instance, bats can hear sounds even up to 100000Hz. In fact, they

locate their prey in the night with the help of their highly developed capability of hearing.

What makes us sense a sound? To understand this, it is necessary for us to understand the

structure and function of the human ear. The human ear basically consists of three parts-

the outer ear, the middle ear and the inner ear (fig.1.2). The outer ear is comprised of the

pinna and the ear canal leading to the ear drum. The pinna is basically a sound collecting

and focusing device for the incident sound energy. Though most animals can move the

pinna in the direction of the sound source, humans have lost this ability and hence they

have to move their head to identify the direction of a sound source. The ear canal is about

¼ inch in diameter and 1 inch in length. This length supports resonance for sound waves

of the order of 1000Hz frequencies and this is the reason why human ear is more

sensitive at middle frequencies of the audible spectrum. The ear canal terminates at the

ear drum which oscillates when the sound energy is incident upon it. The ear drum

consists of a very sensitive and delicate membrane. After this starts the middle ear which

contains a number of bones connected to each other in a manner that they transmit the

vibrations of ear drum to the inner ear. The inner ear is a complex bony cavity called the

cochlea which is filled with a colorless fluid. The cochlea is divided in the middle by

membranes that are partly gelatinous and partly bony. These membranes have fine hair

like cells which move when the cochlear fluid vibrates. This motion is sensed by nerve

cells and processed by the brain to give us a sensation we call as sound. These hair-cells

become stiff in people who are exposed to high noise levels for a long period and are the

major cause of hearing loss in such people.

Fig. 1.2 Structure of human ear

1.4 Definition of Noise

Noise means any irritating sound which affects the physiological and psychological well

being of a person in an adverse manner. It is now established that repeated exposure to

noise may either result in temporary or permanent hearing loss which in extreme cases

may lead to total deafness. Further, noise may interfere with speech communication,

disturb sleep and affect work performance, thus, causing anxiety in a person.

Human responses to a sound may be different for different persons. Also, a person may

respond to same sound differently at different times. Thus, the identification of a sound as

noise becomes a subjective problem, even though there are some sounds that may be

universally regarded as noise. The degree of annoyance and discomfort experienced by a

person depends on the frequency spectrum and intensity of sound, the aural sensitivity of

the listener and upon the time and surrounding environment when the individual is

exposed to noise.

1.5 Sound Pressure Level – The Decibel Scale

Since the range of sound pressures commonly encountered by the human ear is very

wide, it has been condensed into a more manageable logarithmic scale by the acoustical

scientists by devising the concept of sound pressure level ( Lp ), given by

L p pp re= 10 10

2 2log ( / ) [dB] or

L p pp re= 20 10log ( / ) [dB] ..........(1.2)

where

pre = international reference pressure of 2 10 5× − Pa which represents the

average threshold of hearing for the normal healthy human ear.

p = root mean square (rms ) sound pressure (N/m2)

In terms of equation (1.1), the root mean square pressure can be given by

pT

t dtrmsT

T

= −→∞ ∫lim

1

0

p sin ( ) 0

2 2 ω φ ...............(1.3)

Fig. 1.3 The decibel scale

An average normal human ear can respond to sound waves in a frequency range of 20Hz

to 20,000Hz and to pressures ranging from 20µPa (~ 0 dB) which represents the

threshold of hearing to more than 100Pa which corresponds to the threshold of pain. A

scale showing the sound pressure levels (in decibels) of certain common noise

phenomena in relation to sound pressures (in micropascals) is depicted in fig. 1.3.

1.6 Sources of Noise

Noise sources may be classified differently.

(i) Point Source

If the dimensions of a source are small compared with the distance to the

listener, it is called a point source, for example, fans and chimney stacks. The

sound energy spreads out spherically, so that the sound pressure level is the

same for all the points equidistant from the source and decreases by 6dB per

doubling of distance. This holds true until ground and air attenuation

noticeably affect level.

(ii) Line Source

If a noise source is narrow in one direction and long in the other compared to

the distance to the listener, it is called a line source. It can be a single source

such as a pipe carrying a turbulent fluid, or it can be composed of many point

sources operating simultaneously, such as a stream of vehicles on a busy road.

Here, the sound energy spreads out cylindrically, so that the sound pressure

level is the same at all points at the same distance from the line and decreases

by 3 dB per doubling of the distance. This holds true until ground and air

attenuation noticeably affect the level.

Another way to categorize noise is on the basis of type of activity producing the noise.

Thus noise can be classified as traffic noise, industrial noise, commercial noise,

community noise etc.

Noise assessment is generally about evaluating the impact of one specific source, for

example, the noise from a specific production plant. This is not always an easy task. In

reality, a large number of different sources contribute to the ambient noise at a particular

point. Ambient noise is the noise from all sources combined – e.g. factory noise, traffic

noise, birdsong, running water etc. Specific noise is the noise from the source under

investigation. The specific noise is a component of the ambient noise and can be

associated with a specific source. Noise levels emitted by different types of sources are

shown in fig.

1.7 Measurement of Noise

The job of measuring the sound field at a given point is accomplished with the help of a

sound level meter. The principal components of a typical sound level meter are shown in

the schematic diagram of fig. 1.4. The microphone senses a sound pressure signal and

converts it to an analog electrical signal. The preamplifier is used for impedance

matching. Different frequency weighting networks (fig. 1.5) namely, A, B, C are used to

modify the frequency response characteristics of the measuring instrument. This is done

to improve the correlation between sound sensation and instrument reading in accordance

with the sensitivity of human ear in the audible range. The selection of the appropriate

frequency weighting network is dependent upon the type of measurements being made.

For most common steady noises A- weighting network is considered to be most

appropriate. The root mean square detector is the most common detector used in sound

level meters. It provides the running time average of the square of the sound pressure

signal. Finally, display is the component where the results of the measurements are

displayed. The display may be digital or analog in nature.

Fig. 1.4: Schematic Diagram showing the major component of a Sound Level Meter

Fig. 1.5 Different weighting networks used for measuring noise pollution

1.8 Indices of Noise Pollution

Since noise levels in actual field conditions may fluctuate quite wildly, certain

statistically derived indices have been used by acoustical scientists. Few of the most

commonly employed indices in the studies of noise pollution are discussed below:

1. Statistical Percentiles:

The percentile index, Ln , is defined as that level of noise which is exceeded n%

of the time in the total data points obtained for a certain interval of time. L1 is

used as a measure of peak noise levels , L10 , as a representative of levels during

periods of intense noise, L50 , as an indication of the average noise level and

L90 gives an idea of the background noise levels.

2. Traffic Noise Index TNI

In studies related `to traffic noise , another index TNI is also used . This is usually

expressed in terms of L10 and L90 (Magrab 1975 ) as follows :

TNI L L L= − + −4 3010 90 90( )

Where the term L L10 90− indicates the range of "noise climate" and describes the

variability of noise, L90 as mentioned above represents the background noise

level and the third term 30 is introduced to give convenient numbers. It

emphasizes that a significant degree of annoyance arises from the variable

character of noise.

3. Equivalent Continuous Sound Level Leq

One of the most important and widely used index to characterized noise is the

Equivalent Continuous Sound level Leq .This is the level of a theoretical constant

noise equivalent in energy content to the actual fluctuating noise over a given

period of time. Mathematically

LT

p

pdt

Tdteq

T

L

T

=

=

∫ ∫10

110

11010

0

2

0

10

10

0

log log ( / )

where L = sound pressure level

T = time interval of observation.

If the sound levels are measured over discrete time intervals ∆Ti s, then Leq can be

given by

LT

Teq i

L

i

n

i=

=

∑101

1010

10

1

log ( / )∆

1.9 Standards of Noise Pollution in India

Following are the ambient noise pollution standards prescribed by CPCB in India.

Area Code Category of Areas Day Time Leq

Levels

Night Time Leq

Levels

A Industrial Area 75 70

B Commercial Area 65 55

C Residential Area 55 45

D Silence Zone 50 40

Here, day time refers to 6.00a.m. to 9.00p.m. while the night time means 9.00p.m. to

6.00a.m. Silence zone includes the areas upto 100meters around certain premises like

hospitals, educational institutions and courts. Honking of vehicle horns, use of

loudspeakers, bursting of crackers etc. are banned in these zones.

1.10 Summary

A wave is a perturbation/disturbance that travels onwards through a medium. A

wave is characterized by its frequency, wavelength and amplitude. Sound waves

are longitudinal waves that travel in the form of condensations (compressions)

and rarefactions in the medium. A normal healthy human ear can hear sounds in

the frequency interval 20 Hz to 20,000 Hz. Noise means any irritating sound

which affects the physiological and psychological well being of a person in an

adverse manner. Since the range of sound pressures commonly encountered by

the human ear is very wide, it has been condensed into a more manageable

logarithmic scale by the acoustical scientists by devising the concept of sound

pressure level, which is expressed in decibels. Sources from which sound is

emitted may be typically classified as the point source and the line source. The

sound pressure level in a sound field is measured with the help of a sound level

meter. The data collected by a sound level meter is then used to compute various

indices of noise pollution, some of which are utilized to formulate standards of

noise pollution at a given place.

1.11 Key Words

Sound Waves: Longitudinal waves that travel in the form of condensations

(compressions) and rarefactions in the medium.

Noise: Any irritating sound which affects the physiological and psychological

well being of a person in an adverse manner.

The percentile index, Ln : The level of noise which is exceeded n% of the time

in the total data points obtained for a certain interval of time

Equivalent Continuous Sound Level Leq : The level of a theoretical constant

noise equivalent in energy content to the actual fluctuating noise over a given

period of time

1.12 Review Questions

1. Define the following:

(i) Transverse waves

(ii) Longitudinal waves

(iii) Wavelength

(iv) Frequency

(v) Time period

2. What is sound? Explain audible, infra-sonic and ultra-sonic sounds?

3. What is noise? Explain the decibel scale with the concept of sound

pressure level.

4. Differentiate between point source and line source.

5. What are different indices of noise pollution?

6. How is noise pollution measured? What are the standards of noise

pollution in India?

1.13 Suggested readings

1. Bell, L. H. and Bell, D. H. (1994), "Industrial Noise Control", Marcel

Dekker, Inc.

2. Kryter, K. D. (1985), “The Effect of Noise on Man”, New York, Academic

Press.

3. Stephens, R. W. B. (1986),"Noise Pollution Effects and Control", SCOPE

John Wiley and Sons.

4. Singal, S. P. (2005), “ Noise Pollution and Control Strategy”, Narosa

Publishing House.

5. Aggarwal, S. K. (2005), “ Noise Pollution” APH Publishing Corporation.

Unit-IV PGDEM-04 Noise and Air Pollution Control-I

Dr. Krishan Kumar

STRUCTURE

1.0 Objectives

1.1 Introduction

1.2 Particulate Control Devices

1.2.1 Electrostatic Precipitators

1.2.2 Fabric Filters

1.3 Strategies for Noise Pollution Control

1.3.1 Silencers

1.4 Summary

1.5 Key words

1.6 Review Questions

1.7 Suggested readings

1.0 Objectives

To sensitize the students about the following major devices for the control of air

and noise pollution

• Electrostatic precipitators

• Fabric Filters

• Silencers

1.1 Introduction

Air pollutants are of two types: gaseous and particulates. Gaseous pollutants are

the pollutants in gas phase. They have the property of filling any available space

until their concentrations reach equilibrium by diffusion. If the space is too large,

the resulting concentration may be negligible. On the other hand, if space is small,

the resulting concentration may reach significant levels e.g. concentrations of

carbon dioxide due to continuous running of a motor vehicle in a closed garage.

Particulates are finely divided solids and liquids, such as dusts, fumes, smoke, fly

ash, mist and spray.

• Dusts are small particles (1.0 to 1000µm) of solids created from the break up

of larger particles by operations such as crushing, grinding and blasting.

• Fumes are fine solid particles (0.03 to 0.3µm) that condense from vapors of

solid materials.

• Smoke is unburned carbon (0.5 to 1.0 µm) that results from the incomplete

combustion of carbon containing substances.

• Fly ash (1.0 to 1000µm) is the noncombustible particle admixed with

combustion gases in the burning of coal.

• Mists are the particles (0.07 to 10µm) formed from the condensation of liquid

vapors.

• Sprays are particles (10 to 1000µm) formed from the atomization of liquids

through nozzles.

Air pollution control may be defined as the various measures taken to meet certain

emission standards. These measures may include changes in processes/raw

materials or modification of equipment. Another method is the installation of

devices at the end of process equipment to treat the exhaust gas stream. These

devices are called air pollution control equipment. In the coming section, we shall

focus on the equipments that are used for the control of particulate matter.

1.2 Particulate Control Devices

There are three general types of particulate control equipment: force-field settlers,

fabric filters, and scrubbers. Force-field settlers are equipments that use a field of

force for the collection of particulate. There are three types of force fields:

gravitational, centrifugal, and electrical. Equipments that make use of gravitational

field for settling particulates are called gravitational settling chambers. Settlers

that utilize centrifugal force for the collection of particulates are called centrifugal

collectors. Devices, which utilize an electric field of force to collect particulates,

are called electrostatic precipitators (ESPs). Fabric filters are devices that use the

principle of filtration for the removal of particulates. Scrubbers remove

particulates from the exhaust gas stream by using water droplets for capturing

them. Of all the devices mentioned above, electrostatic precipitators (ESPs) and

the fabric filters possess the highest collection efficiencies. Particularly, they are

very effective for the collection of small particulates that can be respired by

human beings. Other devices mentioned above are often used for pretreatment of

the effluent gas before directing it ESPs or fabric filters.

1.2.1 Electrostatic Precipitators

Electrostatic precipitators make use of electric field force for the collection of

particulate matter. This is done by applying a high voltage pulsating direct current

to an electrode system consisting of a small diameter discharge electrode which is

usually negatively charged, and a collection plate electrode which is grounded.

This produces a unidirectional, nonuniform electric field whose magnitude is

highest near the discharge electrode. A corona (a kind of glow) is generated near

the discharge electrode, a condition that is essential for the process of charging.

The electric field near the wire (discharge electrode) accelerates electrons present

in the gas to velocities sufficient to cause ionization of the gas in the region near

the wire. The ions produced as a result of the corona migrate toward the collection

electrode and in the process collide with and become attached to particles

suspended in the gas stream. The attachment of ions results in a build up of

electric charge, the magnitude of which is determined by the number of ions

attached.

The charge on the particles in the presence of an electric field results in a new

force in the direction of the collection electrode. The magnitude of the force is

dependent upon the charge and the field. This force causes particles to be

deposited on the collection electrode where they are held by a combination of

mechanical, electrical and molecular forces.

Once the particles are collected, they can be removed by coalescing and draining,

in case of the liquid aerosols, or by periodic impact or rapping, in case of solid

material. In case of rapping, a sufficiently thick layer of dust must be collected so

that it falls into the hopper in coherent masses to prevent excessive re-entrainment

of the particles in the gas stream.

Fig.1.1 A typical ESP installed in an industrial set up

Fig 1.2 Schematic diagram of an Electrostatic Precipitator

1.2.1.1 Components of Electrostatic Precipitator

An electrostatic precipitator is composed of the following components:

(i) Discharge Electrodes

The discharge electrodes are thin round wires varying from 0.05 to 0.15

inch (0.13 to 0.38 cm.) in diameter. Most common designs use wires

approximately 0.1 inch (0.25 cm) in diameter. The discharge electrodes

consist of vertically hung wires supported at the top and held taut and

plumb by the weight at the bottom. The wires are usually made from

high-carbon steel, or of stainless steel, copper, titanium alloy and

aluminum. The weights are made of cast iron and are generally 11.4 Kg

or more. The weights at the bottom are attached to guide frames to help

maintain wire alignments.

(ii) Collecting Electrodes

Most precipitators use plate collection electrodes. The plates are

generally made of carbon steel, stainless steel, or some kind of alloy,

depending upon the gas stream conditions. The plates range from 0.02

to 0.08 inch (0.05 to 0.2cm) in thickness. Plates are spaced from 4 inch

(10 cm) to 12 inch (30 cm) apart. Normal spacing for high efficiency

units is 20-23 cm. Plates are usually 20 to 50 ft (6 to 15 m ) high.

(iii) Shells

The shell structure encloses the electrodes and supports the precipitator

component in a rigid frame. This is done to maintain proper electrode

alignment and configuration. Providing supporting structures to the

precipitator component is a very important aspect of design. Collecting

plates and discharge electrodes are supported at the top so that elements

hang vertically under the force of gravity. This allows the elements to

expand or contract with temperature changes without binding or

distorting.

(iv) Rappers

Removal of accumulated dust deposit on collection electrode is

accomplished by rapping. Dust deposits are dislodged by mechanical

impulses or vibrations imparted to the electrodes. A rapping system is

designed so that rapping intensity and frequency can be adjusted for

varying operational conditions. Rapping of collection plates can be done

by a number of methods. One of the popular methods of mechanical

rapping uses hammers mounted on a rotating shaft. As the shaft rotates,

hammers drop by gravity and strike anvils attached to the collection

plates. Rapping intensity is governed by the weight of hammers and

length of the hammer mounting arm. The frequency of rapping can be

changed by altering the speed of the rotating shafts.

(v) Transformer-Rectifier Sets

The T-R sets are required to control the strength of electric field

generated between the discharge and collection electrodes. They step up

the normal service voltages from 400 to 480V to approximately

50,000V and convert alternating to direct current.

1.2.1.2 Efficiency Of Electrostatic Precipitator

The efficiency of an electrostatic precipitator is given by the Deutsch-Anderson

equation given below:

)/( 1 QwAeE

−−=

Where E is the collection efficiency of the precipitator, A is the effective

collecting plate area of the precipitator, Q is the gas flow rate of the precipitator

and w is the drift velocity i.e. the velocity with which particles migrate towards the

collecting electrode.

The efficiency of an electrostatic precipitator is greatly affected by the particle

resistivity. Therefore, discussion about the performance of electrostatic

precipitator would remain incomplete if no mention is made about it. Rsistivity

refers to the resistance offered by the collected dust layer to the flow of electric

current. By definition, resistivity is the electrical resistance of a dust sample 1.0

cm2 in cross-sectional area, 1.0 cm thick, and recorded in units of ohm.cm. Dust

resistivity values can be classified roughly into three groups:

1. Between 104 and 10

7 ohm.cm – low resistivity

2. Between 107 and 10

10 ohm.cm – normal resistivity

3. Above 1010

ohm.cm – high resistivity

Particles that have low resistivity are difficult to collect since they are easily

charged and lose their charge upon arrival at collection electrode. This happens

very fast and the particles can take on the charge of collection electrode. Particles

thus bounce off plates and are re-entrained in the gas stream.

Particles that have normal resistivity do not rapidly lose their charge upon arrival

at collection electrode. These particles leak their charge to ground and are retained

on the collection plates by intermolecular adhesive and cohesive forces. This

allows a particulate layer to build up, which is then dislodged into hopper through

rapping. At this range of resistivity (i.e. 107 to 10

10 ohm.cm ), therefore, particles

are collected most efficiently.

Particles that exhibit high resistivity are difficult to charge. Once they are finally

charged, they do not readily give up the acquired negative charge upon arrival at

the collection electrode. As the dust layer builds up on the collection electrode, the

layer and the electrode form a high potential electric field.. This produces a

condition called as back corona which produces small holes or craters in the dust

layer, from which back corona discharges occur. Positive ions are generated

within the dust layer and are accelerated toward the negative (discharge) electrode.

This counteracts the process of ion generation at the discharge electrode and thus

results in the reduction of collection efficiency.

1.2.2 Fabric Filters

Fabric filters remove dust from a stream of gas by means of a porous fabric and a

cake of dust as the filter media. These systems are commonly called as baghouses

since the fabric is usually configured in cylindrical bags installed within a housing.

The basic principle of baghouse operation involves the removal of dust from the

dust laden gas by passing the dirty gas through a filtration medium. The cleaned

gas emerges from one side of the medium while the dust is collected on the other

side. Periodically, the collected gas is removed from the fabric.

The type of filter fabric used depends on the temperature and acidity of the gas

stream, the characteristics of the dust, the gas-to-cloth filtration ratio, and the type

of bag cleaning used.

Because all baghouses impose extra pressure drop on any operating process, a fan,

blower, or compresser of some kind must be used to draw the process gases

through the system. Usually, such devices are installed on the baghouse outlet,

which is the clean side of the filtration process. This location has the advantage

that it does not subject the fan to the dust so that the possibility of dust leakage

into the clean gas coming out of the baghouse is reduced. This becomes

particularly important when the dust is toxic.

There are a number of mechanisms through which the fabric filter traps the dust.

Interception takes place when a particle traveling along a stream line in a gas

stream approaches a fiber in the filter. The path of the particle is such that it strikes

the fiber and gets stuck on it. In case of inertial impaction, a gas stream bends its

direction if it comes across a fiber in its path. However, the dust particle being

heavy, can not change its path (due to the property of inertia) and bangs the fiber

where it gets stuck. This collection mechanism is effective for particles about

10µm or larger. For particles below 10µm, this is not a very effective mechanism.

For smaller particles, there is another mechanism that is effective. This is the

process of diffusion. When the particles are too small, their motion can be affected

by collisions with gas molecules. Frequent collisions with gas molecules make the

path of a small particle erratic or random. The random motion of these small

particles continues until they bump into the fiber and collected. Electrical

entrapment can be another mechanism through which particles are collected in a

fabric filter. Often, fibers and particles, both are charged. If these charges are of

opposite sign, the particles are attracted to the fiber and collected on it. Another

mechanism is sieving in which the particles larger than the pore size of the fabric

cannot pass through the fabric. Sieving is a very important mechanism particularly

after the building of dust cake on the surface of fabric. Without the dust cake, the

efficiency of a fabric filter would be just 60 to 70%. It is the dust cake on the

surface of the fabric, which reduces the pore size and thereby, increases the

efficiency of a fabric filter to 99 percent.

Fig. 1.3 A typical baghouse assembly

1.2.2.1 -Types of Fabric Filters

Fabric filters can be classified into different groups in a number of ways. One such

is to group the fabric filter designs by their cleaning methods. There are three

major cleaning methods: shakers, reverse-air, and pulse jets. Another approach is

to group fabric filters as per their capacity to deal different volumes of exhaust

gases. There are three groupings: low volume, medium volume and high volume

fabric filters. Yet another way is to classify the fabric filters according to the type

of filter media they use i.e. woven or felted. Still another way is to categorize on

the basis of temperature applications i.e. high temperature (>400°F), medium

temperature (200 to 400°F) and low temperature (<200°F) applications group.

1.2.2.2 -Cleaning Methods of Fabric Filters

(i) Shakers

Shakers remove the collected dust from the surface of bag by

mechanically shaking it. This is done manually in small dust collectors.

In large size collectors, this process is motorized. The bag is generally

open at the bottom and close at the top where it is attached to the

shaking mechanism. In this configuration, the dust is collected on the

inner sides of the bags. Shaking is done at a frequency of several cycles

per second with the amplitude of a fraction of an inch to a few inches.

The duration of shaking may be 30s to a few minutes. Common bag

diameters are 5, 8 and 12 inches. The operation of shaking is performed

in the off-stream mode.

(ii) Reverse_Flow Cleaning

Reverse-air cleaning involves the removal of dust from the bags by

backflushing them with a low-pressure reverse flow. In the case of high

temperature applications, the just cleaned hot gas is employed to

backflush rather than the ambient air. Woven filter media are generally

employed in conjunction with reverse-air cleaning. Dust is collected on

the inners side of the bags, which are closed at the bottom and open at

the top. Most often, reverse flow systems are comprised of isolatable

compartments. Normally, cleaning is done one compartment at a time.

Duration of cleaning may vary from 1-2minutes. Cleaning is performed

in the off-stream mode. Common bag diameters are 8, 12 inch.

(iii) Pulse Jet Cleaning

Pulse-jet cleaning employs high pressure compressed air, with or

without a venturi, to backflush the bags vigorously. This method creates

a shock wave that travels down the bag, knocking the dust away from

filter medium. This method is generally employed in conjunction with

felted filter media. The duration of cleaning is lower than that of other

two methods. The pulse/shock wave lasts only for a fraction of a

second. The baghouse is often not subdivided into compartments when

pulse-jet cleaning is employed. The bag is closed at the bottom and open

at the top. Dust is collected on the outside of the bag. Usually, a row of

bags is cleaned simultaneously by introducing compressed air briefly at

the top of each bag.

1.2.2.3 -Baghouse Selection

A baghouse is selected on the basis of certain basic information about the

process, the gas stream, and the dust to be collected. Following are the

factors that go behind the selection of a baghouse for a particular

application:

(i) Description of Application – What is the application? It is

important to know fully the application for which the fabric filter

is required.

(ii) The gas volume - An important aspect is the gas flow rate to be

filtered. Normal gas flow, as well as surges and maximum flows,

must be established in order for a properly sized baghouse.

(iii) The gas temperature – Maximum and minimum temperatures

determine to a large degree the selection of bag fabric and other

materials of construction.

(iv) Chemical properties of the gases – It is important to identify the

corrosive gases, combustible gases, and condensable vapors at

inlet conditions. These inputs can greatly influence the selection

of fabric and materials of construction.

(v) Description of dust – Knowledge of dust concentration (grains

per cubic feet of gas), properties of dust such as particle size

distribution, shape, chemical composition, tendencies to

agglomerate or develop electrostatic charges, abrasive

characteristics, and bulk density are all very important factors in

the selection of baghouse and auxiliary equipment.

(vi) Available space – Availability of space is another important

criterion that determines the size of a baghouse to be installed for

a particular application.

(vii) Other equipment in the dust collection system – The dust

collection system may include other equipment, which may

influence the selection of baghouse.

Selection of filter media is another very important aspect of baghouse selection.

The filter media should be able to withstand temporary heat surges. Depending

upon the specific applications, a particular filter media may be selected. The fiber

must also be able to resist degradation from exposure to acids, alkalies, solvents or

oxidizing agents found in the dust laden gas stream. Dimensional stability of the

filter medium is another important factor. The fiber may shrink or stretch within

the application environment. However, these effects must be controlled to

maintain the dimensional stability of the fiber. Finally, cost of the fiber is a very

important factor in the selection of filter medium. Generally, the least costly

selection that satisfies the above mentioned requirements, is preferred. Table 1.1

presents the characteristics of some of the widely used filtration media.

Table 1.1- Characteristics of some common fabric filter media.

Fabric Max.

Temp.

Acid

Resistance

Fluoride

Resistance

Alkali

Resistance

Abrasion

Resistance

Cotton 180°F Poor Poor Good Very Good

Polypropylene 200°F Excellent Poor Excellent Very Good

Polyester 275°F Good Poor to

Fair

Good Very Good

Nomex 400°F Poor to

Fair

Good Excellent Excellent

Teflon 450°F Excellent Poor to

Fair

Excellent Fair

Fiberglass 500°F Fair to

Good

Poor Fair to

Good

Fair

1.2.2.4 Performance of a Baghouse

Despite several sophisticated formulae that have been developed, there is no

satisfactory set of published equations that allows a designer to calculate the

efficiency of a prospective baghouse. One parameter that helps the baghouse

designers is the Gas-to –Cloth (G/C) ratio. This is a measure of the amount of gas

driven through each square foot of fabric in the baghouse. It is given in terms of

the number of cubic feet of gas per minute passing through one square foot of

cloth. Factors influencing the appropriate G/C ratio for a baghouse include the

cleaning method, filter media, dust size, dust density, dust loading, and other

factors that are unique to each situation. Because of their variability, however, it

has not been possible to satisfactorily quantify each of these factors for

application. One approach to overcome this problem is to collect all empirical data

available for the source in question. If there are no data for the industry at hand,

then go to a similar industry, which is using a baghouse and determine the G/C

range successfully employed in that industry and conservatively apply it to your

case.

1.3 Strategies for Noise Pollution Control

There are four general methods of controlling noise: enclosing the noise source,

enclosing the noise receiver, putting a barrier between the noise source and the

receiver, and controlling the noise generator.

Noise is transmitted by vibration. Hence the property of the enclosure must be

such that it should not vibrate when a sound wave hits its surface; otherwise, the

enclosure itself becomes the source of noise. Since vibration is inversely related to

the mass of the material, in the use of enclosures, the effectiveness of control is,

therefore, a function of the mass of the enclosure. Thus, by the mass law, the ideal

enclosure is the heavy enclosure (materials of high density). Table 1.2 shows

surface densities of some common materials of construction.

Table 1.2 – Densities of some common materials of construction.

Material Surface Density in kg/m2/cm of thickness

Brick 19-23

Concrete Blocks 15

Dense Concrete 23

Wood 4-8

Common glass 29

Lead sheets 125

Gypsum board 10

Steel 108-112

Putting a barrier between the source and the receiver is generally used for

controlling highway noise. The effectiveness of a barrier is dependent on the

geometry of the source, barrier and receiver, and on the ground cover. Studies on

different kind of noise barriers reveal that noise attenuation up to 8-14 dBA may

be achieved using barriers 8ft high and 4 inches thick.

1.3.1 Silencers

Control of noise at points of generation may be done with the help of mufflers or

silencers and isolation of noise source by vibration control. There are three basic

types of silencers:

(i) Absorptive Silencers

In these silencers, a lining of some acoustic material is provided directly

on the interior of the duct. The duct may be straight or may have bends,

or the duct may be expanded into plenum lined with the acoustic

material. The acoustic material absorbs the noise, thus attenuating it.

The absorptive silencer is a type of dissipative muffler since it dissipates

the noise by absorbing it.

(ii) Reactive Silencers

These have no lining of absorptive acoustic materials. In them,

attenuation of noise is achieved by reflecting the sound waves so as to

cancel the waves of incoming noise. This process is called destructive

interference. Reactive silencers are found in trucks and automobiles.

(iii) Diffusers

High velocity mass of air impinging on stationary air or solid objects

produces noise due to the turbulence created. Diffusers attenuate noise

by reducing this velocity. The source flow is diffused out into a

multitude of tiny flows having lower velocities using some appropriate

mechanism. The diffuser is an exhaust muffler, since it attenuates noise

by installing it at the end of a duct or pipe.

1.4 Summary

Due to their obvious adverse effects on the physiological as well as

psychological health of human beings, air and noise pollution control are two of

the major components of any pollution management program. Control of

particulate matter, emitting from an industrial process, is one of the important

objectives of any air pollution control initiative. Two of the most efficient devices

used for this purpose are the Electrostatic Precipitators (ESP’s) and Fabric Filters

or the Baghouses. Whereas, electrostatic precipitators work on the principle of

electrostatic charging and subsequent collection of particles by employing a strong

non-uniform electric field, fabric filters use the simple mechanisms of inertial

impaction, diffusion, and sieving for trapping particulate matter. As far as control

of noise pollution is concerned, two of the main strategies in this regard are (i)

controlling noise at the source itself and (ii) isolating the source from the receiver

using a barrier. Silencers and mufflers are important devices used for controlling

the noise at the source itself. Different types of silencers use different principles

for controlling noise.

1.5 Key Words

Particulates: Finely divided solids and liquids, such as dusts, fumes,

smoke, fly ash, mist and spray.

Electrostatic Precipitator: A device that makes use of a strong non-

uniform electric field for the removal of particulate matter from the effluent

gas.

Baghouse: Systems consisting of assemblies of bags which remove dust by

means of a porous fabric and a cake of dust as the filter media.

Silencers: Devices consisting of ducts designed to reduce the level of sound.

1.6 Review Questions

1. What is the principle on which electrostatic precipitator works?

2. What are different components of an electrostatic precipitator?

Explain their significance.

3. How do you calculate the efficiency of an electrostatic

precipitator?

4. What is resistivity? How does it affect the efficiency of a

precipitator?

5. What are different mechanisms through which a baghouse traps

dust?

6. What are different types of cleaning methods used for the

removal of dust from the fabric in the baghouse filters?

7. What are the factors that must be considered before selecting a

baghouse for a particular application?

8. What are different ways of achieving noise control?

9. What are different types of silencers used for noise control?

1.7 Suggested readings

1. Masters, G. M. (1998), “Introduction to Environmental Engineering and

Science” – Prentice Hall of India

2. Boubel, R.W., Fox, D.L., Turner, B. and Stern, A.C. (2005), “

Fundamentals of Air Pollution” – Academic Press.

3. Bell, L. H. and Bell, D. H. (1994), "Industrial Noise Control", Marcel

Dekker, Inc.

4. Stephens, R. W. B. (1986),"Noise Pollution Effects and Control", SCOPE

John Wiley and Sons.

5. Singal, S. P. (2005), “ Noise Pollution and Control Strategy”, Narosa

Publishing House.

UNIT-IV PGDEM-03

RADIOACTIVITY IN ENVIRONMENT

Written by Dr. Hardeep Rai Sharma, SIM conversion by Prof. Anubha Kaushik

STRUCTURE

1.0 OBJECTIVES

1.1 INTRODUCTION

1.2 RADIO ACTIVITY

1.2.1 Radio nuclides

1.2.1.1 Kinds of Radiations

a) Electromagnetic radiation b) Particulate radiation c) Ionizing radiation d) Non-ionizing radiation

1.2.1.2 Sources of Radioactivity in Environment

a) Natural sources b) Man made sources

1.2.1.3 Fate and Movement of Radioactivity in Environment

- Physical and biological half-lives of radio nuclides

1.2.1.4 Biological Effects of Radiations

1.3 SUMMARY

1.4 KEY WORDS

1.5 SELF ASSESSMENT QUESTIONS

1.6 SUGGESTED READINGS

1.0 OBJECTIVES

After studying this unit you should be able to know :

* About radionuclides

* About various kinds of radiations

* Natural and man made sources and fate and movement of

radioactivity in environment.

* Biological effects of radiations.

1.1 INTRODUCTION

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The smallest unit of an element (as hydrogen carbon, oxygen) that can

exist while retaining the characteristics of that element is called atom.

Each atom has proton (+), neutron (uncharged) and electron (-). Atom of

each element has characteristic numbers of protons, neutrons and

electrons. Most elements, however, in nature contain atoms that are not

exactly like the predominant form. These atoms have different number of

neutrons. These different forms of the same element are called isotopes.

Some isotopes of common elements are stable under ordinary conditions

while others have various degrees of instability, and some of them

disintegrate with the emission of radiations of one kind or the other.

1.2 RADIOACTIVITY

1.2.1 RADIO NUCLIDES

Radioactive isotopes are isotopes that emit ionizing radiation. Since the

radiations are highly energetic (as x-rays) and these tend to split

substances, including living matter, into ions, they are called ionizing

radiation. The term isotope has been used loosely and the appropriate

general term for a particular kind of atom is nuclide. Natural radioactivity

occurs only in elements whose atoms hold a nuclear charge more than

83. The nuclei of such atom are quite, unstable due to large positive

charges on it and emit α (alpha) and β (beta particles). The atomic

nucleus attains an excited state in this manner and emits X-rays or

γ (gamma) rays in order to relieve this energy state .

When the α rays are given off, a new element is formed whose nuclear

charge is reduced by 2 units and whose nuclear mass is reduced by 4

units. For example, the element radium (Ra) is transformed into the rare

gas radon (Rn). 226 4 226

Ra -- He → Rn + energy 88 2 86

If a nucleus loses beta particles of electrons the element receives an

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additional positive charge on its nucleus without changing the mass of

the nucleus. For example, the lead (isotope) 214Pb is transformed into the

element bismuth (Bi): 214 214

Pb – e– → Bi + energy 88 83

The ions that form in α and β decay proceed quickly into a neutral state

by giving or receiving electrons. The unstable elements which forms from

α and β decay in turn form new elements by further decay, until a-stable

element is found.

Nuclear rays are high energy rays while α rays have 4-9 million electron

volts (MeV) of energy, β rays have usually 0.5-2 Me.V and γ-rays about

0.1-2 MeV of energy. The unusually high energy of the nuclear rays

decreases progressively as they pass through air, water or other media,

because collisions with other materials occur during such passage and

with every collision the atom is excited or ionized. The electron moves

temporally to a higher energy level as it takes an additional energy, and

then again releases that energy and return to its original level. The

energy released can be harnessed for chemical reactions or one can

harness the light it emits, e.g. in a scintillation counter.

The larger the particles of the nuclear rays are, the more frequently they

will collide with molecules and the more quickly they will lose their

energy. The distance that the ray travels is affected by this. (The photons

of γ-rays travel a greater distance than helium nuclei, though their

ionization strength is less than helium nuclei. β-rays lie between α-rays

and γ-rays both in distance they travel and their ionization strength. In

the air γ-rays travel a distance of several to many metres depending on

their energy content. They penetrate entirely the soft tissues of

organisms, as do free neutrons. β rays can travel about 150-850 cm in

the air; they penetrate at most a few centimeters into the soft tissues of

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organisms. Helium nuclei travel 2.5-9 cm in the air and penetrate only

fractions of millimeters into soft tissues, α-rays and β rays therefore

release their entire energy during their short passage through the tissue.

That implies that the cells suffer severe damage at the point at which

these rays penetrate them.

As radioactive elements decay more frequently, they become more

hazardous to body tissue; for that reason the number of instances of

decay in a ,given quality of food is a matter of importance. The Becquerel

is the unit of measurement; I Becquerel (Bq) = 1 decay per second. The

number of rays, or the dose, is determined by reference to the ion pairs

generated. Rontgen (R) is the unit of measurement; I R = number of rays

that produces 2.082 billion ion pairs in 1 cm3 of air. The number of rays

that is absorbed by body tissue and that is responsible for the biological

effect is measured in “radiation absorbed dose” (rad) i.e. as the number of

rays that is absorbed by a given mass of material, 1 rad =0.01 J/kg. The

rad is usually replaced by the Gray (Gy) in present day measurements.

The relationship between the two is 1 Gy. 1 J/Kg = 100 rad.

Metabolism of radio nuclides

If a radio nuclide absorbed into the body is an isotope of element

normally present (e.g. Na, K or Cl), it will behave like the stable element.

Also, if it has chemical properties similar to an element normally present,

it will tend to follow the metabolic pathway of the natural metabolite (e.g. 137Cs and K or 90Sr and Ca). For other radio Nuclides, their metabolism

will depend on their affinity for biological ligands and for membrane

transport systems.

Calcium has an important function as a major component of bone,

although bone also act as a reservoir of calcium in the body : in man

about 17% of calcium in the skeleton is recycled each year. About 30% of 45Ca is absorbed from the gut and about 65% of that is deposited in the

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skeleton. 90Sr follows a similar route, although urinary excretion is

greater.

Plutonium mainly enters the body by inhalation. Its compounds can may

be soluble in water (e.g. plutonium nitrate or chloride), or chemically

inert and insoluble (plutonium dioxide). The soluble component is rapidly

absorbed from the lungs and transported in the blood to be either

excreted through the kidneys or deposited in tissues (bones and liver).

Out of plutonium entering the blood, about 45% is deposited in the liver,

45% in the skeleton, and the remainder either excreted or deposited in

other tissues. Biological half-life of Plutonium in the bone and liver are

about 100 years and 40 years, respectively. From animal studies, it is

apparent that the lungs, the cells of inner surface of bone, the bone

marrow and the liver are at the most at risk from accidental intake of

plutonium.

1.2.1.1 Kinds of Radiation

There are different types of radiation discussed below:

a. Electromagnetic Radiations

This form is similar to light in its physical properties. These include a

broad spectrum of energy. These are : a) Ultraviolet rays ; b) X-rays c)

Gamma rays; d) Infra Red rays; e) Radio waves; f) Visible light rays. All

the different kinds of electromagnetic radiations are nothing more than

light rays of different wave length and frequency.

• Ultraviolet Rays

The wavelength of UV rays extends from 0.1 µm (100 nm) to 0.4 µm (400

nm). Ultraviolet radiation is divided into UV-C (wavelength of 200-280

nanometers), UV-B (280-320 nm), and UV-A (320-400 nm). The most

biologically damaging is UV-C and the least damaging is UV-A, with UV-B

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having intermediate efficiency of biological action. The solar spectrum at

the earth's surface contains only the UV-B and UV-A radiations.

Stratospheric ozone strongly absorbs UV-C radiation and the shorter

wavelength portion of UV-B radiation, thus providing some biological

protection.

• X-rays

X-rays are also a form of electromagnetic radiation, but differ from

gamma radiation in that they result from extra-nuclear loss of energy of

charged particles, for example electrons, but having shorter wavelengths

than ultraviolet radiation. They may be emitted when an electron of an

atom jumps from one orbit to another orbit of lower energy. This

difference in energy is radiated as electromagnetic radiation. If the energy

is high enough to cause ionization the emission is called X-rays.

• γ-Rays

Gamma radiation is emitted only in conjunction with other types of decay

and belongs to the class known as electromagnetic radiation (like radio

waves and visible light, but of very much shorter wavelength and higher

energy). It is emitted when the nucleus produced following radioactive

decay is in an excited state, and then returns to the ground state by

emitting this radiation to carry away excess energy.

• Radiowaves/Microwaves

These are the waves in or near the extremely high frequency or shorter

wavelength range (3 mm to 200 cm). Microwave energy is too low to

disrupt living tissues by ionization. Instead, the energy gets absorbed as

oscillation energy and is converted to heat. This makes it possible to use

microwaves for cooking.

b) Particulate Radiations

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They consist of the particles ejected from atoms at high speed and often

with tremendous energy. These have electrons, proton or neutron.

Whether the radiation emitted from nuclear disintegration is

electromagnetic or particulate, the emanations are so energetic and

forceful that they can do great damage to living tissues. The radiation

include β-particles, α-particles, proton, neutron and cosmic rays.

• α-radiation

α radiation has been shown to be composed of helium nuclei, consisting

of two protons and two neutrons bound together very tightly to give a

very stable unit. Consequently each particle possesses a positive charge

of 2 units, and a mass of 4 units. One electron volt (eV) is defined as the

energy gained by an electron passing through an electric potential of 1

volt. One gram of radium emits 3.7 x 1010 α-particles and 2 x 109 cal,

which is 2 X 105 times the calorific value of coal.

• β-Radiation

Normally the term beta particle or radiation refers to the high speed

negative electrons of kinetic energy up to more than 3 MeV originating in

the nucleus. One further type of beta particle, is also known, having

same mass as an electron, but is, positively charged and known as

positron radiation Indicated by β+.

• Neutron

Neutron is very common particle, being a basic constituent of the

nucleus and having a mass almost identical to the proton but carrying no

charge. There are no significant naturally occurring neutrons emitters,

but radio nuclides that emit neutrons can be produced artificially. The

neutrons are of great importance both in nuclear fission reactors and in

the production of radio nuclides not available naturally.

• Proton

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Protons are 1,835 times heavier than electrons. Beta-particle drives into

a tissue like a tiny particle of sand, while the proton lumbers along like a

rock, knocking off pieces of atoms and molecules as it goes. The proton

does not penetrate as far as an electron of the same energy, but it causes

more disruption in a small area.

• Cosmic Rays

The extremely penetrating radiation falling upon the earth's surface

beyond the atmosphere are called cosmic rays. The cosmic rays which

are just entering on earth's atmosphere from outer space are called

primary cosmic rays. They are almost composed of positively charged

atomic nuclei, mostly proton about 89% and about 9% are α-particles

and rest are heavy nuclei such as carbon, nitrogen, oxygen, iron etc.

They have energies ranging from 109 to 1018 eV.

As the primary cosmic rays enter the earth's atmosphere from outer

space, its constituent charged particles collide with the nuclei of

atmospheric gases and splits into smaller nuclear fragments. These

fragments move with high speed and collide with other nuclei and

produce high speed particles and some elementary particles. When these

short lived elementary particles decay, electrons and highly penetrating

γ-rays are emitted. These protons and other high speed particles that are

produced are called as secondary cosmic rays.

Types of radiation on the basis of ionization

Radiation is energy being propagated from one place to another through

space. There are mainly two types of radiation on the basis of ionization:

• Ionising Radiation.

lonising radiation is sufficiently energetic to cause ionizations. An atom

gets ionized when it gains sufficient energy for one or more of its

electrons to get separated from the atom. Ionisation of a molecule might

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yield two charged fragments, such as H2O → H+ + OH–. If the fragments

are uncharged, then they are referred to as ‘free radicals' as H20 → H +

OH.

• Non-Ionising Radiation

Radiations of shorter wavelength but having greater energy may be able

to harm the microorganisms but are able to injure only the surface

tissues of higher plants and animals. These radiations includes

ultraviolet radiation, microwaves and extra low frequency (ELF)

electromagnetic radiation.

1.2.1.2 Sources of Radioactivity in Environment

Man is exposed to different sources of radiation. These are :

a) Natural sources

These include: a) cosmic rays; b) environment (rocks, water, air); c) living

organisms (internal).

Radio nuclides of radium, thorium, uranium and isotopes of potassium

(40K) and carbon (14C) are very common in soil, rocks, air and water.

Marine sediments generally have higher concentrations of radio nuclides.

On an average, man receives about 50 m rads/yr from terrestrial

radiations and it may be as high as 2000 m rads/yr in areas where

uranium containing rocks exist as in Kerala.

Radiations from atmosphere are also common. For instance, radioactive

gases like radon are present in air through with low values of roughly 2

m rad/yr.

Man is also exposed to internal radiations from radioactive substances in

the body tissues. For instance, uranium, thorium and isotopes of

potassium, strontium and carbon exist in small amounts in the body.

Internal radiation values vary from 25 to 75 m rads/yr.

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b) Man made sources

These include :

(i) Use of X-ray machines and laser beam (diagnostic and radio

therapeutic) is one such source.

(ii) Radioactive fall out (nuclear test) : Explosion of nuclear weapons

would generate small particles that would drift in the atmosphere

as an aerosol, and in the course of months and years would settle

on the earth's surface as fallout and is the cause of fairly uniforml

release of radioactivity.

(iii) Nuclear reactor wastes: The use of radioactive substances like 233U, 235U or 239Pu in nuclear power plants is another source of

radioactivity in the environment. The risk of melting down of a

reactor is a major risk in case of atomic power plants. Two very

serious instances have already occurred : one in Harrisburg in

1979 and another in the super reactor in Chernobyl in 1986. An

area of at least 100,000 km2 of the soil has been so intensively

polluted with radioactive material that in future no agriculture will

be possible on it. A nuclear power plant must be stopped after

about 30 years because of the constant contamination it sustains.

The process of dismantling a retired plant and of removing the

contaminated parts is hazardous and is a cause of radioactivity in

environment. The disposal of the tritium contaminated Water in

the reactor is also a problem. If the release of water is uncontrolled

the tritium enters the air and drinking water and eventually

reaches humans through the food chain.

(iv) Industrial and research uses of radioactive materials : Radio active

material are used in R & D activities and from there enter into

environment.

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(v) Miscellaneous, (fulminous watch dials) : Several radioactive

materials find use in daily life and emit the radiations.

1.2.1.3 Fate and Movement of Radioactivity in Environment:

The radioactive pollutants reaching the freshwater resources or oceans

are rapidly lost to the sediments and may bio-accumulate in the body of

plants and animals directly or through food chains (bio-magnification). In

the body of the organisms, they behave chemically as their stable

counterparts, but are more dangerous because of the radiation which

they emit internally. Algae, macrophytes and fish concentrate the radio

nuclides in greater amounts from ambient water.

Man is the ultimate sufferer who consumes the contaminated food and

water. However dose radioactive waste extremely low. The irrigation by

contaminated water will pollute the soil from where the radio nuclides are

transferred to the crops. Soils also get polluted by a direct release of low

activity waste waters and by radioactive fall out. The radioactivity from

the soil moves through the food chains and reaches man after

consumption of crops, meat, milk, eggs etc. The underground water may,

also receive radio nuclides after leaching from the soil.

The radioactivity released into the atmosphere is rapidly diluted by

atmospheric processes, but it may be of concern to man in certain highly

contaminated areas, for example, in the vicinity of atomic explosions or

in atomic power plants. The atmospheric fall out depositing directly onto

the leaves is efficiently passed into the grazing animals, such as cattle,

and reach to us. Cesium-I37 and Strontium-90 are two most important

radio nuclides found to reach humans in this manner.

Physical and Biological half-lives of Radio nuclides

The amount of a radioactive element that decays in a unit of time is

always proportional to the remaining amount. Every element has a

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constant decay time, so different elements have different decay times. For

practical purposes time in which· the number of radioactive atom of a

nuclide is reduced by half called half-life is used.

To assess the time during which a radioactive element contaminates the

body after its incorporation, the biological half-life is relevant. The term

biological half-life is the time span during which half of the received

material is eliminated from the body, since radio nuclides do not

decompose in the body. From the biological half-life Tb. and the physical

half-life Tp, the effective half-life (Teff) for the entire organism or for a

specific organ can be calculated; this figure indicates how long the

organism or a specific tissue has been exposed to radiation.

Teff = Tb Tp Tb+Tp

The physical, biological and effective half lives of a few radioactive

elements are given in Table 1.

Table-1: Physical, biological and effective half-life of some radionuclides. For plutonium and half-life refer to bones. In the lung (as a non-water-soluble compound) the value is one year.

Element Half-life Type of ray

Physical Biological Effective

H-3 12.26 Years 19 Days 19 Days β-

C-14 5730 Years 35 Days 35 Days β-

P-32 14.3 Days 10 Years 14.1 Days β-

K-40 1.25 x 109 Years 37 Days 37 Days β-, β+

Ca-45 165 Days 50 Years 163.5 Days β-, γ

Sr-90 28.1 Days 11 Years 7.9 Days β-

1-131 8.07 Days 138 Days 7.6 Days β-, γ

Cs-137 30.23 Years 70 Days 69.6 Days β-, γ

Ba-140 12.8 Days 200 Days 1.2 Days β-, γ

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Rn-222 3.824 Days α

Ra-226 1600 Years 55 Days 53.2 Years α, γ

U-233 1.62 x 105 Years 300 Days 300 Days α, γ

Pu-239 2.44 x 104 Years 120 Years 120 Years α, γ

Source : The Chemistry of Pollution, Gunter Fellenberg, pp. 164

1.2.1.4 Biological Effects of Radiations

Radioactive substances are among the most toxic substances known.

Radium is 25,000 times more lethal than arsenic. The most tragic early

evidence of the potency of radiation toxicity was the death of Marie Curie,

while working with her husband; Pierre Curie. She died of leukemia due

to radiation exposure.

Ionizing radiations bring about more dangerous effects than other

toxicants. Their effect may continue in subsequent generations. They

bring about following two types of undesirable effects in organisms.

i) Somatic Effects

These are the direct results of action of radiation on the body cells and

tissues. Radiologists, uranium mine workers and painters of radium dials

suffer the most. More evidence of degree and kind of damage from

radiation comes from studies of the Nagasaki and Hiroshima survivors.

The somatic effects may be immediate or delayed.

High radiation exposures have much acute toxicity and can kill animals

quickly. A dose of 400 to 500 roentgen on whole body is fatal in about

50% cases of man, and 600-700 roentgen in practically every case. The

victim declines in vitality and dies from anemia, infection and

hemorrhage. Parts of body differ in sensitivity. The most sensitive tissues

are intestine, lymph nodes, spleen and bone marrow.

The radiations destroy the body's immune response. The effects of low

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penetrating radiations are less severe than the penetrating ones.

In delayed effects the patient may survive for months or years. Delayed

effects of radiations include eye cataracts, leukemia, malignant tumors,

cardiovascular disorders, premature ageing and reduced life span.

Diagnostic X-rays exposure of pregnant women may increase the risk of

cancer in child.

ii) Genetic Effects

Both, natural and man-made radiations bring about genetic effects.

Studies on Drosophila (fruit fly) have shown that mutation rates go very

high due to radiation exposures. Most genetic effects are brought about

by man-made radiations mostly from medicare and exposure from

nuclear power plants. People in industry, research and medicine using

radio nuclides are exposed more than others. The greatest damage is in

dividing cells, chiefly the gonads. The effects include mutation or lethal

effects on egg or embryo. The intensity of radiation affects the rate of

mutation. Generally higher animals are more susceptible to genetic

damage than lower animals as insects. Genetic effects also occur in

plants.

1.3 SUMMARY

Radioactive isotopes are the ones that emit ionizing radiations, which are

highly energetic and tend to split substances including living matter.

There is emission of alpha (α), beta (β) and gamma (γ) particles, each

having characteristic charge, penetrating power and energy. Radioactive

elements are more hazardous to body tissue as they decay more

frequently and Bequerel (Bq) is the unit of measurement of 1 decay per

second. Radionuclides, when absorbed into the body, behave like a stable

element and follow the metabolic pathway of a natural metabolite e.g. 90Sr behaves like calcium. Radiations can be of various types. The

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electromagnetic radiations include ultra-violet rays (UV), X-rays, gamma

rays, radio waves and infrared rays. UV-B and UV-C rays are very

hazardous for biological systems. We are exposed to radiations from

natural sources like cosmic rays, rock, air, water etc. or from man-made

sources like X-rays, nuclear reactor wastes or nuclear fall-outs. The

radioactivity also moves through the food chain and reaches man’s body.

Half life of the radionucleides is very important to know how long the

radioactive substance will remain in the tissue or in the environment.

Radiations have adverse effects on living organisms causing damage to

body cells and tissues, destruction of immune response, genetic effects,

cancer and even death.

1.4 KEY WORDS

Isotopes : An element having atoms with different

number of neutrons.

Radioactive isotopes : Isotopes that emit radiations

Becquerel : Unit of measurement of decay (1 Bq = 1 decay

per second).

Rontgen (R) : Unit of measurement of X-ray

Rad : Radiation absorbed dose i.e. the number of

rays absorbed by a given mass of material.

UV rays : Ultraviolet rays with wavelength 0.1 µm to 0.4

µm. UV-C and UV-B are very harmful.

Alpha rays : Positively charged particles consisting two

protons and two neutrons

Beta rays : High speed negatively charged electrons.

1.5 SELF ASSESSMENT QUESTIONS

1. What are the different sources of radioactivity in environment?

15

2. Explain the somatic effects and genetic effects caused by

radiations.

3. Describe various types of electromagnetic and particulate radiation.

4. Differentiate between ionizing and non-ionizing radiations.

5. Write a brief note on :

i) α-rays ii) β-rays iii) χ-rays iv) γ-rays v) Radionuclides vi) Cosmic rays

1.6 SUGGESTED READINGS

1. Environmental Science, the natural environment and human

impact by Andrew R. W. Jackson and Julle M. Jackson. Addison

Wesley Longman Limited, England, Page No.295-296.

2. Water pollution : causes, effects and control by P.K.Goel, New Age

International (P) Publishers, Delhi. Page No. 143-150.

3. Radioactivity. In "The Chemistry of Pollution" Gunter Fellenberg,

John Wiley & Sons Ltd., pp 161-172 (2000).

4. Radiation biology "McGraw Hill Encyclopedia of Environment

Science & Energy" 3rd Edition (Eds.) Sybil. P. Parker and Robert

A.Corbitt. Mc Graw Hill, Inc., (I 993), pp 424-429.

5. Non-ionizing Radiations In “Encyclopedia of Environment Science

& Engineering" 3rd Edition (Eds.) James R. Pfafflin and Edward

N.Ziegler, VoL-II (J-Z) Gordan & Breach Science Publishers, S.A.

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UNIT-IV PGDEM-04

NUCLEAR, THERMAL, INDOOR & ELECTROMAGNETIC POLLUTION

Written by Dr. Hardeep Rai Sharma, SIM conversion by Prof. Narsi Ram Bishnoi

STRUCTURE

2.0 OBJECTIVES 2.1 INTRODUCTION 2.2 SOURCES OF NUCLEAR WASTE 2.2.1 Mining of ores 2.2.2 Milling of ores 2.2.3 Feed material preparation and fuel fabrication 2.3 NUCLEAR POWER 2.3.1 Some major nuclear disasters 2.3.1.1 Hiroshima 2.3.1.2 The Fire of Windscale 2.3.1.3 Chernobyl 2.4 THERMAL POLLUTION 2.4.1 Impact of thermal pollution 2.4.2 Standards for thermal pollution 2.5 INDOOR POLLUTION 2.5.1 Indoor pollutants sources 2.5.2 Precaution/preventive measures of indoor pollution. 2.6 ELECTROMAGNETIC POLLUTION 2.7 SUMMARY 2.8 KEYWORDS 2.9 SELF ASSESSMENT QUESTION 2.10 SUGGESTED READINGS 2.0 OBJECTIVES

While studying this unit, you will be able to understand:

Major nuclear disaster and impact of thermal pollution and

electromagnetic pollution.

Sources of indoor pollution, precaution and measures for indoor pollution.

2.1 INTRODUCTION

Nuclear waste management is the field where most stringent possible

degree of quality control is required to be achieved. Unlike other waste

management problems in industry, no compromise is made against safety

standard due to its high cost incurring figure. In most countries regulations lay

down the maximum permissible exposure to radiation for workers in nuclear

industry and also for the general population. The thermal power industry in India

has an important role in development of industry as well as development of rural

India. But in the wake of its coming it also brings the dangers of pollution which

unless controlled can have short-term and long-term effects.

2.2 SOURCES OF NUCLEAR WASTE

Nuclear waste is generated in the multifarious fields of nuclear energy

systems and also in different stages of operations.

2.2.1 Mining of Ores. Mining of uranium and thorium ores generate scant liquid

radioactive waste. Dry mining is generally employed. Where drainage is required,

the activity has generally been sufficiently low for permitting direct discharge into

the environment.

However, the underground mining of uranium causes gaseous release

and insufficient ventilation results in lung cancer among the miners due to radon

products.

2.2.2 Milling of Ores. The first potentially serious waste generation starts with

milling operation. The specific process of milling operation for extraction of the

desired mineral is dependent on the composition and nature of the ore itself.

In the uranium mills, both acid and alkaline leaching processes are utilised

for separating the uranium from the extraneous matrix. As the ores are milled

and leached, only about fourteen percent of the total radioactivity in the ore fed to

the mill is recovered in the uranium concentrate. The process waste water

containing trace quantities of radium and thorium ends up in a tailing pond.

Leaching and seepage from the tailing ponds have caused concentrations of

Ra226 and Th230 greater than permissible below some of the tailing piles. The

radium 226 is in an undissolved form when it is discharged from the plant.

The milling operations also produce hazardous radioactive silica dust as

gaseous waste.

2.2.3 Feed Material Preparation and Fuel Fabrication. Feed material

preparation and fuel fabrication also entail radioactivity though of very low level.

The principal product is metallic uranium which is processed from high grade

uranium concentrates. Uranium trioxide is reduced to uranium hexafluoride for

the purpose of enrichment. The fluoride of uranium is finally converted to metallic

uranium.

The filters used in the intermediate steps are contaminated with uranium dust

and both solid and organic contaminated wastes and produced in the various

other steps in the processing operations.

2.3 NUCLEAR POWER Conventional steam electric power plants use fossil fuel such as coal, oil

or natural gas. The fuel is burnt in a boiler that produces steam which, in turn,

drives a steam turbine generator, called a turbo generator. Heat in commercial

quantities can also be produced indirectly involving atomic nuclei, this energy

sources is called nuclear energy. There are two processes by which energy is

obtained from atomic nuclei, fission and fusion. In fission, the collision of a

certain type of heavy nuclei is (having many neutrons and protons) with a

neutron results in the splitting of the nucleus into two smaller sized fragments.

Since together the fragments are more stable energetically than was the original

heavy nucleus, energy is released by the process.

The combination of two very light nuclei to form one combined nucleus is

called fusion and also results in the release of huge amounts of energy (E=mc2)

again since the combined nucleus is more stable than the lighter ones. Since

nuclear forces are much stronger than chemical forces, the energy released in

nuclear reactions is immense as compared to those obtained in combustion

process.

In a nuclear power plant, the heat is produced in a device called a nuclear

reactor instead of a boiler. Nuclear power is a modern means of generating

electricity. The fuel of a nuclear electric generator is atomic pellets of uranium

metal. Uranium contains 3 million times as much potential energy as coal. One

gram of fissionable material releases 23,000 K watt hours of heat. One ton of

uranium would provide as much energy as 3 million tons of coal or 12 million

barrels of oil.

Both, natural and man-made atomic fuels are used for reactors. These

fuels have the ability of fission. Uranium-235 (235U) is a natural fuel, containing

0.71% of the uranium found in nature, the rest being. 238U which does not

undergo fission spontaneously. It can be changed to fissionable material by

bombarding with neutrons called conversion. Thus atoms of U-238 are changed

through decay to plutonium-239 a man-made substance.

2.3.1 Some Major Nuclear Disasters of Historic Importance 2.3.1.1 Hiroshima The group of people from whom the most reliable data have been

gathered concerning radiation hazards are the survivors of the atom bomb

dropped at Hiroshima at 8:15 am on Aug. 6, 1945. Exhaustive studies have

shown that the heavily exposed people, called the hibakusha had a 29% greater

chance of dying from cancer than normal. Excess numbers of leukemia cases

began appearing in the late 1940’s and peaked in the early 1950’s, but by the

early 1970’s they had dropped to levels near those of unexposed Japanese. One

of the most feared hazards of radiation is that of congenitally deformed in infants

because of radiation induced genetic defects in the mothers.

Dozens of mentally retarded infants were born in the areas around

Hiroshima and Nagasaki in the months following the blasts. Abortions were also

numerous.

2.3.1.2 The fire at Windscale (Oct. 8, 1957)

This occurred in the plutonium production reactor and was the result of

human error coupled with inadequate operating instructions. A major fire had

taken hold and was consuming the uranium metal fuel and the graphite

moderator. The operators attempted to maintain secrecy for 24 hours after the

fire was discovered. It was estimated that the most hazardous release was that

of 20,000 curies of I131 and the Govt. ordered the disposal of all milk from dairy

herds within radius of about 25 miles. The full report of the subsequent enquiry

was never published.

2.3.1.3 Chernobyl The most recent and highly publicized nuclear disaster was Chernobyl,

Ukrane in April of 1986. Explosions from runaway nuclear reactor burst through a

4000 tonne steel concrete cover. The reactor core temperature was shown to be

more than 2000°C. Fuel and radioactive debris spread into air and hit the

surrounding areas. Radioactive particles spread out but in a volcanic cloud along

with streams of gases from molten mass in the core. In less than a week, deadly

debris and gases had drifted over most of Europe. The neighbouring countries

such as Poland had banned sale of cow milk as there were chances of

contamination of grass with long lived isotopes, due to radioactive fall-out.

Twenty per cent of the reactor radioactive iodine escaped along with 10-20% of

its radioactive cesium and other isotopes. 1,35,000 people lived in a 30 km

radius, of the power plant. There were 30 deaths and 237 cases of severe

radiation injury. Russian scientists estimated an increase in the cancer rate of

0.04% over the next 20 years. Thousands of reindeer had to be destroyed in

Northern Scandinavia because they had grazed on contaminated pasture. Stress

and fear created an understandable desire in these people to be moved out of

the area causing psychological damage.

2.4 THERMAL POLLUTION Water is able to absorb large quantities of heat without changing from its

liquid state. The high heat capacity means, that it is extensively used as a

coolant in many industries. Thermal pollution can be defined as an accumulation

of unusable heat from human activities that disrupts ecosystems in the natural

environment. Much of the heat produced by industries is in the form of condenser

cooling water. The principal user of water as a coolant include the electricity

generating industry, thermal power plants, nuclear power plants, petroleum

refineries, steel mills, chemical plants, paper and pulp mills etc.

The coolant water required by industry is drawn directly from water bodies,

frequently rivers. After use of water, the warmed water is often directly

discharged back into the original water body. This results in thermal water

pollution. The increase in heat contributes to the physical, chemical and

biological changes in the receiving water bodies.

Soil erosion and shoreline deforestation also contribute to thermal water

pollution but upto less extent. The soil erosion makes the water muddy, which in

turn increases the light absorbed and thus the water temperature is raised.

Deforestation of shorelines further contributes to the problem in two ways. First, it

increases soil erosion and secondly, it increases the amount of light that strikes

the water, both of which increase the temperature of water.

2.4.1 Impacts of thermal pollution (Physical, chemical and biological)

1. Temperature influences the viscosity, density, vapour pressure, surface

tension, gas solubility and gas diffusion rates.

2. Heated water has low density and spreads on the surface of water bodies

causing them to stratify thermally. The stratification is barrier to the oxygen

penetration into the deeper layers.

3. At elevated temperature, the sedimentation of suspended materials

increased due to reduction in density and viscosity of water.

4. Evaporation rate of water increased at high temperature.

5. Rate of chemical reactions normally increased with rise in temperature

which is about two-fold with every rise of 10ºC. BOD is also increased with

temperature.

6. The species composition changes as species tolerant of warmer water

replace those that are unable to adapt. This transition is often

accompanied by on overall decrease in species richness. For example,

attached algae in heated effluents were reported to show an increase in

biomass but a decrease in the number of species represented.

7. The rates of photosynthesis and plant growth are increased. An increase

in plant growth may seem to be a good thing at first glance but more live

plant means more dead plants. The pile up of dead plants leads to an

increase of bacterial population which consume oxygen along with dead

plants. There is now less oxygen and a greater demand for it.

8. The warmer water also increased the metabolic rate of fish, which leads

to, a sharp decrease in the life expectancy of aquatic insects. The

enhanced metabolism required more oxygen. However, the amount of

dissolved oxygen present in water is inversely related to its temperature.

On the other hand with the lack of aquatic insects, fish faces shortage of

food.

9. The disease resistance in fishes decreased and pollutants become more

toxic at elevated temperature. The species become more vulnerable to

parasites.

10. Thermal pollution can also interfere with the natural reproductive cycles of

fish. For example, premature hatching of eggs by artificially raised

temperatures may lead to mass mortality of the young fish through

starvation. Mass killing of fish and other aquatic organisms can occur

when there is a very rapid changes in water temperature. This is known as

thermal shock.

11. A continuous exposure to heat leads to the development of a new

ecosystem comprising of thermally adapted species. Sudden stoppage of

the industrial plants will again disrupt the system. Thousands of warm

water fishes and other animals were found dead when a thermal power

plant in New Jersey, U.S.A. was stopped for repairing for one day in

February 1972.

12. Natural migration of fish is also affected due to the formation of thermally

polluted zones which act as barrier to the migration.

2.4.2 Standards for thermal pollution

The Central Pollution Control Board (CPCB) in India has specified the

standards for thermal discharges from thermal power plants. The condenser

cooling water should not have temperature more than 5ºC higher than the intake

water temperature. Thermal water pollution can be avoided by pre-cooling the

warm water prior to its discharge. The major principles involved in heat loss are

conduction, convection, radiation and evaporation. For example, cooling ponds

and cooling towers are often used for cooling water in the electricity generating

industry. In cooling ponds the water from condensers is stored in earthen ponds

where natural evaporation brings down the temperatures. The water after cooling

is recirculated or discharged to the nearby water body. Alternatively, the warm

waste water can be effectively used by other industries. The potential uses of

waste heat may be in green houses, agriculture, aquaculture and space heating

beside others.

2.5 INDOOR POLLUTION

In the last several years, a scientific evidences has clearly indicated that

the air within homes and other buildings can be more seriously polluted than the

outdoor air. People spend approximately 90% of their time indoors. Thus, for

those people the risks to health may be greater due to exposure to air pollution

indoor than outdoors. Peoples like the young, the elderly and the chronically ill

people especially those suffering from respiratory or cardiovascular disease who

may be exposed to indoor air pollutants for the longest periods of time are often,

the most susceptible to the effects of indoor air pollution.

Indoor pollution sources that release gases or particles into the air are the

primary cause to indoor air quality problem in homes. Inadequate ventilation can

increase indoor pollutant levels by not bringing in enough outdoor air to dilute

emissions from indoor sources and by not carrying indoor air pollutants out of the

home.

2.5.1 Pollutant Sources

There are many sources of indoor air pollution in any home. These include

combustion sources, such as oil, gas, kerosene, coal, wood and tobacco

products building materials and furnishings, asbestos-containing insulation, wet

or damp carpet, furniture made of pressed wood products, products for

household cleaning and maintenance, personal care or hobbies central heating,

cooling in humidification devices, radon, pesticides and outdoor air pollution.

Some sources such as building materials, furnishings and household

products like fresheners, release pollutants more or less continuously. Other

sources related to activities carried out in the home, release pollutants

intermittently. These include smoking the use of unvented or malfunctioning

stoves, furnaces, space heaters, the use of solvent in cleaning and hobby

activities and the use of cleaning products and pesticides in housekeeping.

a) Radon

The most common source of indoor radon is uranium in the soil or rock

from which homes are built. As uranium naturally breaks down, it releases radon

gas which is colorless, odorless, radioactive gas. This gas enters homes through

dirt on floors, Cracks in concrete walls and floors, flow drains and sumps. Any

home may have a radon problem. This means new and old homes, well-sealed

and drafty homes and homes with or without basements will have radon problem.

Sometimes radon enters the home through well water. In a small number of

homes, the building materials can give off radon. The predominant health effect

associated with exposure to elevated levels of radon is lung cancer. Smoking

increase the risk of lung cancer in homes already having high radon levels.

Environment Protection Agency (EPA) estimates that radon causes about 14,000

death per years in U.S.A. only.

b) Environmental Tobacco Smoke (ETS)

It is the mixture of smoke that comes from the burning end of a cigarette,

pipe or cigar and smoke exhaled by the smoker. It is a complex mixture of over

4000 compounds, more than 40 of which are known to cause cancer in humans

or animals. According to EPA, ETS is responsible for approximately 3,000 lung

cancer deaths each year in non-smoking adults and impairs the respiratory

health of hundreds of thousands of children. Infants and young children whose

parents smoke in their presence are at increased risk of lower respiratory tract

infections (pneumonic and bronchitis) and are more likely to have symptoms of

respiratory irritation like cough, excess phlegm and wheeze.

c) Biological Environments

Biological environments include bacteria, molds, mildew viruses, house

dust mites, cockroaches and pollen grains. Pollens originate from plants, viruses

are transmitted by people and animals and bacteria are carried by people,

animals, soil and plant debris. Household pets are sources of saliva and animal

dander. The protein in urine from rats and mice is a potent allergen.

Contaminated central air conditioning systems can become breeding grounds for

mold, mildew and sources of other biological contaminants.

By controlling the relative humidity level in a home, the growth of some

sources of biological environment can be minimized. A relative humidity of 30-

50% is generally recommended for homes. Standing water, water damaged

materials or wet surfaces also serve as a breeding ground for mold, mildews,

bacteria and insects. House dust mites the source of one of the most powerful

biological allergens grow in damp, warm environments.

Some biological contaminants trigger allergic reactions, including

hypersensitivity pneumonitis, allergies and some types of asthma. Infectious

illnesses, such as influenza, measles and chickenpox are transmitted through the

air. Molds and mildews release disease causing toxins. Biological pollutants

include sneezing, watery eyes, coughing, shortness of breath, dizziness,

lethargy, fever and digestive problems.

d) Stove heaters, fireplaces and chimneys

In addition to environmental tobacco smoke, other sources of combustion

products are unvented kerosene and gas space heaters, woodstoves, fireplaces

and gas stoves. The major pollutants released are carbon monoxide (CO),

nitrogen dioxide (NO2) particles and acid aerosols. CO is a colorless, odorless

gas that interferes with the delivery of O2 throughout the body. At high

concentration, it can cause unconsciousness and death. Lower concentration

can cause a range of symptoms from headaches, dizziness, weakness, nausea,

confusion, and disorientation, fatigue in healthy people and episodes of

increased chest pain in people with chronic heart disease. Fetuses, infants,

elderly people, and people with anemia or with a history of heart or respiratory

disease can be especially sensitive to co-exposures.

NO2 is a colorless, odorless gas that irritates the mucous membranes in

the eye, nose and throat and causes shortness of breath after exposure to high

concentration.

Particles are released when fuels are incompletely burnt which can lodge

in the lungs and irritate or damage lung tissue. A number of pollutants including

radon and benzo-α-pyrene, both of which can cause cancer, attach to small

particle that are inhaled and then carried deep into the lung.

e) House-hold Products

Organic chemicals are widely used as ingredients in household products.

Paints, varnishes and wax contain organic solvents, as many cleaning,

disinfecting cosmetic, degreasing and tubby products. Eye and respiratory tract

irritation, headache, dizziness, visual disorders and memory impairment are

among the immediate symptoms that some people have experienced soon after

exposure to some organics.

Paint strippers, adhesive remarks and aerosol spray paints contain

methylene chloride which is carcinogenic in animals. Laboratory studies showed

that perchloroethylene, the chemical widely used in dry cleaning is causing

cancer in animals. Benzene, a known human carcinogen has its source in

tobacco smoke, stoved fuels and paint supplies and automobile emissions in

attached garages.

Formaldehyde is an important chemical used widely by industries to

manufacture building materials and numerous household products. It is also a

by-product of combustion and certain other natural processes. It is used to add

permanent press qualities to clothing and draperies, as a component of gases

and adhesives and as a preservative in some paints and coating products. In

houses, the most significant source of formaldehyde are adhesives containing

urea formaldehyde (UF) resins and phenol formaldehyde (PF) resins used in

pressed wood products. Besides this, the other sources are building materials,

smoking, household products and use of unvented, fuel burning appliance like

gas stoves or kerosene space heaters. Formaldehyde, a colorless pungent smell

of gas, can cause watery eyes, burning sensations in the eyes and throat,

nausea and difficulty in breathing in some humans and carcinogenic in animals.

In homes, insecticides and disinfectants are often used to control insects,

termites, rodents, microbes, fungi and contaminated soil or dust that floats or its

trapped in from outside. They are sold as spray, liquids, sticks, powders, crystals,

balls and foggers. Exposure to high levels of pesticides produced symptoms like

headaches, dizziness, muscle weakness, nausea, damage to liver and central

nervous system as well as an increased risk of cancer.

f) Lead

Lead has long been recognized as a harmful environmental pollutant.

Humans are exposed to lead through air, drinking water, lead contaminated soil,

deteriorating paint and dust. Airborne lead enters the body through inhalation

swallowing of lead particles or dust.

High concentration of airborne lead particles in houses can also result

from outdoor sources, including contaminated soil trapped inside and use of lead

in certain indoor activities such as soldering and stained glass making.

Lead affects practically all systems within the body. At high levels it can

cause convulsions, coma and even death. Lower levels of lead can adversely

affect the brain, central nervous system, blood cells and kidneys. The effects of

lead exposure on fetuses and young children can also be severed and may lead

to delay physical and mental development, lower IQ level, shortened attention

spans and increased behavioral problems. Fetuses, infants and children are

more vulnerable to lead exposure than adults since lead is more easily absorbed

into growing bodies and the tissues of small children are more sensitive to the

damaging effects of lead.

g) Asbestos

Asbestos is mineral fiber commonly used in a variety of insulating and

building construction materials. Today, asbestos is most commonly found in older

houses, in pipes and furnace insulation materials, millboard, textured paints and

floor tiles.

The most dangerous asbestos fibers are too small to be visible. After

inhalation they can remain and accumulate in the lungs. Asbestos can cause

lung cancer, mesothelioma (a cancer of the chest and abdominal linings) and

asbestosis (irreversible lung scarring that can be fatal).

2.5.2 Precautions/Preventive measures for Indoor Pollution

i) Scientific evidence indicates that smoking combined with radon is especial

source causing health risk. Stop smoking and lower radon level to reduce

lung cancer risk.

ii) Open windows or use exhausts fans, Ventilation, a common method of

reducing exposure to indoor. Air pollutants will also reduce but not

eliminate exposure to environmental tobacco smoke.

iii) Do not smoke if children are present, particularly infants.

iv) Use thoroughly clean carpets.

v) Keeping the house clean. House dust mites, pollens and other allergy

causing agents can be reduced, although not eliminated through regular

cleaning.

vi) Install and use exhaust fans or chimney over gas cooking stoves and keep

the burners properly adjusted.

vii) Follow label instruction carefully in case of household chemicals.

viii) Throw away partially full containers of old or unneeded chemicals safely.

ix) Ventilate the area well after pesticide use. Use non-chemical methods of

pest control when possible.

x) Limit exposure to repellents to a minimum.

xi) Keep areas where children play as dust free and clean as possible.

2.6 ELECTROMAGNETIC POLLUTION

Electromagnetic radiation consists of electric fields produced by voltages

and magnetic fields produced by electrical currents. Although electrical field can

be shielded by conducting materials, magnetic fields can penetrate almost

anything that stands in their way, including the human body. Power lines give off

extra low frequency (ELF) electric and magnetic fields whose waves vibrate back

and forth 60 times per second. The magnetic fields can be particularly strong in

houses that are close to high voltage transmission lines and to the ordinary high

current distribution lines. We are inundated with radiation from television, radio,

microwaves, cellular phones, heaters, dryers, clocks, electric appliances and the

wiring in the walls. In some locations additional frequencies are generated by

video display terminals (VDT, computer monitors, televisions, etc) on the top of

electrically heated water beds and under electric blankets and heating pots.

Because the magnetic fields from these sources vibrate back and forth at 60

times per second, the same to and fro movement will occur in brain and body

molecules of exposed human beings.

Recent research indicates that regular chronic exposure to

electromagnetic fields (EMF) can have adverse impacts on our health and well-

being and on biological systems in the environment. Electromagnetic radiation

can affect physiology and create chronic conditions producing symptoms like

fatigue, headache and vision problem, short term memory loss, sleep

disturbances, confusion, ringing in the ears and irritability. Electromagnetic

radiation have been found to cause an increase incidence of leukemia,

lymphoma, brain cancer and breast cancer (in women). Many of workers suspect

that extra low frequency radiation impairs the ability of the T-lymphocyte cells,

the infection fighting “soldiers” of the immune system to combat cancer. The

central nerves system, cellular process, the immune system and the human

psychic infrastructure all are the most vulnerable to electromagnetic radiation.

To protect ourselves

1. Avoid use of electric blankets, heating pads, heated waterbeds.

2. Keep the dial face electric clocks at least three feet away from bed, desk

or chair.

3. Pressure must be brought on local, state and federal officials to measure

electromagnetic radiation near power lines and substations. In areas

where the radiation is unacceptably high, wires will have to be re-routed,

buried and shifting of substations.

2.7 SUMMARY

Nuclear reactors are also major source of radioactive pollution, whereas

Hiroshima and Chernobyl are major nuclear disasters that effected huge

population. Unusable heat from human activity disrupts ecosystems in the natural

environment. Thermal pollution is another type of pollution caused by the heat

released in coolant waters, which affects physical, chemical and biological

properties of water. The central pollution control Board in India has specified the

standards for thermal discharge from thermal power plants. In the last several

years, a scientific evidences has clearly indicated that air within house and other

building can be more seriously polluted than the outside air, people spend

approx. 90% of their times indoors. Our indoor environment is also polluted by

several sources like, radon, microorganisms, tobacco smoke, smoke from

kitchen or fire-place, paints, varnish, wax etc. Household products release

formaldehyde, benzene etc. which also affect the health. These days we are

using several electronic gadgets like, TV, clocks, microwave, cellular phones,

vide etc. which release are electromagnetic pollution. This type of pollution can

affect our physiology, nervous system and immune system.

2.8 KEYWORDS

Thermal Pollution: It can be defined as an accumulation of unusable heat from

human activities that disrupts natural ecosystems in the natural environment.

Nuclear Fission: It is a collision of a certain type of heavy nucleus with a

neutron results in the splitting of the nucleus into two smaller sized fragments

and three neutrons. A huge amount of energy is released in this process

(E=mc2).

Nuclear fusion: The combination of two very light nuclei to form one combined

nucleus.

Electromagnetic radiation: It consists of electric fields produced by voltages

and magnetic fields produced by electrical currents.

2.9 SELF ASSESSMENT QUESTIONS

1. What are different types of indoor air pollutants?

2. What short of pollution is associated with electric and magnetic fields

described along with health effect caused by it.

3. Write in brief causes and effects of thermal pollution.

4. Write down the preventive measures to be taken for indoor pollution.

5. Enumerate major nuclear disasters of historic importance.

6. What are the sources of nuclear waste?

2.10 SUGGESTED READINGS:

Jackson, A.R.W. and Jackson, J.M. (2004). Environment Science, the

natural environment and human impact by Addison Wesley Longman

Limited, England.

Goyel, P.K. (2001). Water pollution causes, effects and control, New Age

International (P) Publishers, Delhi.

Fellengerg, G. (2000). Radioactivity in “The Chemistry of Pollution”, John

Wiley & Sons Ltd., New York.

Parker, S.P. and Cobitt, R.A. (1993). Radiation biology “Mc Graw Hill

Encyclopedia of Environment Science & Energy” 3rd Edition (Eds.). Mc

Graw Hill, Inc. New York.

Spiro, T.G. and Stigliani, W.M. (2006). Chemistry of Environment 2nd

Edition. Prentice Hall of India Pvt. Ltd., New Delhi.

Miller, G.T. (2004). Environment Science, Thomson Press, U.K.