1. INTROL.J UCTIDN

1. Air Pollution - General review.

2. Classification & sources of Air.

Pollutants.

3. t:ffects of Air Pollution.

4. Air Pollution in India.

Atmospheric pollution is a major problem facing

all nations of the world. The technological revolution

and ever increasing trend towards urbanisation and indus­

trialisation have contributed to the deterioration of

the environment.

The word 'pollution' is derived from Latin. It

is known as npqlluon in Latin, pollution means something

for washing, that is dirty. Environmental pollution gen­

erally includes the polluting elements as well as the

process of pollution {Sharma, 1977).

Air an@ water pollution have come to be recognised

as the major problems of the modern technolo~ical society.

The societies have been reluctant to accept and have

simply failed to recognise, the limitations of the clea­

nsing properties of the atmosphere. The earth's atmos­

phere is finite and its capacity to clean itself or dilu­

te the pollutants upto harmless levels seems to be limi­

ted at least in some places and with respect to certain

pollutants. As the world population grows and indus­

trias expand to mass manufacture the increasingly diverse

products the emission of some toxic pollutants will

inevitably increase. Increased emissions have already

on several occasions and in several places led to influ­

ence ground level concentrations that resulted in dramatic

rises in mortality and morbidity rates.

The high levels of air pollutants may be harmful

to the human beings. The long term exposure affects

even at low concentrations du~ to synergistic or additive

effects of particulate matters, sulphur-oxides, carbon

mono-oxide, photochemical oxidants and hydro carbons.

These pollutants may prove serious teratogenic, carci­

nogenic, or mutagenic, besides causing many other respi-

2..

ratory ailments, because in a course of an average life, a

human being breat~s about 250,000 m3 of air without any

oppo rt unity for personal choice or protect ion. In addition

to affecting hsalth, the pollutants are found to be res­

ponsible for the decrease in atmospheric visibility, soil-

ing of buildings and metal corrosions etc. The air pollu­

tarlts also effect non-living components of nature, inclu-

ding water, soil and the landscape in general.

The transport of pollutants over long distances has

created international and global pollution problems. The

acid rain threatens irreversible damage to sensitive aqua-

tic and terrestrial ecosystems. The increase of atmos-

pheric carbon dioxide may lead to an increase in mean

ground level temperature. The increase in the mean ground

level temperature by 0.5 °C could .lead to melting of polar

ice and snow. The concentration of carbon dioxide in the

earth's atmosphere is not the only factor affecting the

temperature of t'he atmosphere, but the finest dust parti-

cles have greatest effect on a global seals as they do

not settle out and remain in upper layers of the atmos-

phere from which they cannot be removed either by rain

or by other means. These dust clouds reflect sunlight,

and a further increas8 in the, content of particulate

matter in the atmosphere, could lead in the future to

an abnormal decrease in the man ground level temperature

3

of the atmosphere. The cholorofluoro carbons may deplete

stratospheric ozone (Derek Elsom, 1987).

"Air pollution" is defined by (WHO) World Health

Organisation as follow :

"Air pollution occurs when one or several air

pollutants are present in such amounts for such a long

period in the outside air that they are harmful to humans,

animals, plants or properties, contribute to damage or may

impair the well beiny or use of property to a measurable

degree". (Leitha, 1971).

The composition of clean and dry air is as

fallows :

Compon~i§_

Nitrogen

Oxygen

Argon

~ Carbon dioxide

Table 1.1

78.08%

20.9 5%

0.9 34%

0.033%

Neon

He li UTI

Methane

Krypton

Hydrogen

N it r o us ox i d e

Xenon

(Hougen & Dodge, 1947)

18. 2 ppm

5. 24 ppm

·2.0 ppm

1.14 ppm

0. 5 ppm

o. 5 ppm

0. 87 ppm

The atmosphere is composed primarily of nitrogen,

4-

oxygen and several noble gases. However, there are a number

of gases and that occur in relatively small and sometimes

highly variable amounts. Water vapour, carbon dioxide and

ozone fall in the latter category, and so do the gases

considered to be the coffillllon urban air pollutants.

The air pollution problem can be simply depicted

as a system consisting of three basic components :

1--_,P,....o........,-11.---.,ut,.....a-n'"""t,.....s--~> 2 mixing & chemical transformation'> 3

Emission Sources Atmosphere Receptors

The major emission sources are (1) transportation

(2) electric power generation (3) refuse bur-ning (4) in­

dustrial and domestic fuel burning (5) industrial proce­

sses. (Seinfeld, 1985).

The wa5te products produced by the above sources

mainly comprise of sulphur dioxide, suspended particulate

) I p

matter, oxides of nitrogen, carbon monoxide, hydrocarbons

and lead, which add greatly to the pollution of urban

areas. The development of new industries introduce the

problem of toxic chemicals, while nuclear power production

and atomic-weapons testing highlighted ionizing radiation

as a pollutant (WHO, 19 72).

Classification of air pollutants : The air pollutants

are classified according to chemical composition. They

are further c~assified according to physical state, that

is, gaseous, liquids or solids. Air pollutants are cla-

ssed according to the manner in whi~h they reach the atmos-

ph ere.

1. P r i rna ry p o 11 ut ant s the source

Those emitted directly from

2. Secondary pollutants : Those formed in the atmoso. phere by chemical interactions among primary pollutants and normal atmospheric constituents

The first recognized type air pollution was that,

typified by high concentrations of sulfur compunds (so 2

& Sulfates) and particles resulting from combustion.

The second· type of air· pollution has been called

• smog • ( 11 P hot o c he m i c a 1 s m o g 11 ) • T his p hot o c hem i c a 1 smog

occurs with high temperatures, bright sun light and low

humidity. The main primary pollutants in photochemical

smog are nitric oxide and hydrocarbons, which are rapidly

coverted to secondary pollutants, Ozone, Organic nitrates,

S.

oxidized hydrocarbons and so-called photochemical aero-

sols (Seinfela, 1985).

Air pollution is judged by the presence of five

important components : Oxides of Sulphur, Suspended Par­

ticulate Matter, Oxides of Nitrogen, Uxides of Ca~bon

and Hydrocarbons~

Oxides·£!. sulphu~: Sulfur occurs primarily as metal

sulfides and pyrites in the earth surface, as sulfate

<t, salts in the oceans and as sulphur dioxide, hydrogen-

sulfide and sulfate aerosol in the atmosphere. The

chemistry associated with the global sulfur cycle in-

volves sulfide oxidation byweathering processes to sul-

fates, microbiological reduction of sulrates to organic

sulfides and atmospheric oxidation of organic sulfides

t o s u 1 f u r d i ox i d e an d t hen to s u 1 fat e aero s o ls •

Oxides of sulfur are emitted during petroleum and

metal refining, mobile sources, sulphuric acid production,

coking and forest fires. On a world wide basis, in

volcanoes and geothermal activity, sulphur dioxide and

sulphur trioxide are produced during combustion. Hydro-

gen sulfide is emitted in large quantities in nature from

biological decay processes (Lamb, 1984).

Sulphur trioxide in air has a very short life

time, because of its rapid reaction with water vapour

to form sulfuric acid. This sulfur dioxide can react

G

catalytically or photochemically with other pollutants

to form sulfur trioxide, rapidly hydrating to sulphuric

acid and sulphates (Derek Elsom, 1987).

Suspends~ particulate matter : The term 'suspended par­

ticulate matter' refers to the wide range of finely divi­

ded sol(ds or liquids dispersed into the air from com­

bustion processss (heating and power generation) 1ndus-

trial activities; and natural sources. These particul2te

matter range in size from 0.1 upto about 25 urn in dia-

meter. The constittients of particulate matter vary over

time and space although typical constituents in urban

areas include carbon or higher hydrocarbons formed by

incomplete combustion of hydrocarbon fuels (Derek Elsom,

1987). Particulate matter is unique in its complexity.

Airborne particulate matter results not only from Oirect

emissions of particles but also from emissions of certain

gases that either condense as particles directly or

undergo ·chemical transformation to a species that con-

denses as a particle,

Particles less than 2.5 um in diameter are gen-

erally referred to as 11 fine 11 • and those greater than

2. 5 un diameter as 11 coarse 11 • The particle size ranges

from a few tens of Angstroms to several micrometers (Sein-

feld, 1985).

Aerosol sources can be classified as primary and

7

secondary. The particles which are directly emitted in

to the atmosphere is known as primary particulates. The

secondary aerosols are formed by chemical reactions. The

particulates emitted due to extensive wood burning is of

primary nature. In contrast, at the peak of one severe

photochemical smog episode, well over half of the parti­

culate mass was·attributed to secondary reactions in the

atmosphere (Grosjean and Friedlander, 1975). The primary

sources yield particles of all sizes and the secondary

sources pr'?duces mainly submicron sized particles •

.§.ources of Suspended particulate~§.!. The natural

sources of particles include soil and rock debris, vol­

canic action, sea spray, wild fires and reaction with

natural gaseous emissions.

The amiss ions of particulate matter attributable

9

to the activities of humans arise primarily from four

sources : fuel combustion and industrial processes, indus­

trial process fugitive particulate emissions, non-indus­

tria 1 f ug it i v e so ur c e s such as roadway d us t from paved

and unpaved roads, wind erosion of cropland and trans­

portation sources (automobiles etc) (U.So Environmental

Protection Agency, 1982).

Oxides £! uitro~en : Diatomic nitrogen constitutes appro­

ximately 78% of our atmosphere. Nitrogen plays a dominant

role in the chemistry of all living organisms. In the

atmosphere, ~itrogen exists at trace levels as ammonia,

nitrous oxides, nitric oxide and nitrogen dioxide. Only

nitric oxide and nitrogen dioxide exist as important air

pollutants.

The oxides of nitrogen are produced by natural

processes, including bacterial action in the soil, ligh­

tning and volcanic eruptions. The principal emissions

from human activity are from the combustion of fossil

-fuels in stationary sources like heating, power generation

and in motor vehicles (WHO, 1977a; Derwent & Stewart, 1973).

Oxides of £arbon : Carbon compounds that are important

in local or regional air pollution problems ar~ carbon

monoxide and the number of hydrocarbons emitted as a

result of fossil fuel combustion. Carbon cycle revolves

aro~nd the photosynthetic conversion of atmospheric car-

bon dioxide to oxygen and carbohydrates with subsequent

decomposition of the organic material back to carbon dioxide.

The carbon dioxide effectively absorbs reflected long wave

radiation from the earth's surface, the presence of

carbonidloxide in the atmosphere acts as a blanket to de­

crease the heat loss of the E::arth. The 'green house'

effect of C0 2 is thus an important temperature regulator

for the globe. Anthropogenic co 2 is considered as a

global pollutant. Carbon monoxide is the most widely

distributed of all air pollutants. It is formed during

combustion when carbon is burned with deficient oxygen.

On global basis, motor vehicles contribute 55% of carbon

monoxide (Brain Lamb, 1984).

Hydrocarbons : In the atmosphere, volatile hydrocarbons

typically range from c1

to c10

compounds. The aiiiibient

hydrocarbon composition includes the unburned hydrocar­

• bans from fuela, which are formed during combustion and

natural hydrocarbons emitted by vegetation.

The hydrocarbons are emitted from motor vehicles,

stationary combustion devices and industrial processes. ~ .

10

The hydrocarbons are typically classified in terms of their

atmospheric reactivity with respect to specific reactive

gases. The United States Environmental Protection Agency

has grouped hydrocarbons in three classes : 1. low react-

ivity, 2. moderate reactivity, 3. high reactivity (Sein-

feld, 198~)·

Hydrocarbons and carbon monoxide exhibit a diurnal

pattern in urban areas. During the early morning traffic

period, cono:entration are elevated. As the sun rises,

the hydrocarbons begin to be consumed in the production

of photochemical oxidants and the concentrations decrease.

The night concentrations are relatively low (Lamb, 1984).

A particular group of hydrocarbons causing increa­

sing environmental concern is the polynuclear arowatic

hydrocarbons, PAH.. These are Lnsaturated fused benzene rings varying from napthalene (2 rings) to corene (8 rings).

The PAH compounds are associated with fine particulate

matter pres em t in air.

incomplete combustion.

These compounus originate during the

The major ca~ses of PAH pollution in

cities are emission from motor cars, burning of coal for domestic

cooking, innumerable small factories, very frequent traffic jams

are major sources of polycyclic aromatic hydrocarbons (Chakraborti,

et al, 1988). Particulate matter emiLted from vehicular engines

contains organic compounds, some of which are carcinogens (Kotin,

et al, 1954, 1955; Hoffman, et al, 1965; Grimmer, 1977, Stupfel,

1976; Shabald, 1977). The classes of carcinogen indentified thus

far include unsubstituted PAH and nitrogen heterocyclic compounds.

These carcinogens and their analogues are-active in the Ames

Salmonella/microsome mutagen bioassay (Mccann and Ames, 1976;

Me Mohon, et al, 1979).

Diesel exhaust particulates contain chemicals which

are directly mutagenic in Ames test. Although, the direct

acting mutagen, pyrene-3, 4 dicarboxylic acid anhydride,

from a samjble of diesel exhaust particulates, is only weakly

mutagenic in the Ames test (-Rappaport, et al, 1980). lJHO

in 1971 has branded six of these PAH compounds as potential

carcinogens, out of these four, viz Fluoranthene, Benzo (b)

fluoranthene, Benzo (a) pyrene and Benzo (ghi) perylene are

common components of automobile exhaust.

fmission .Source~: Air pollutants are emitted from various

sources, viz. natural sources and manmade sources as indicated

in Table 1.2

Table 1.2 Classification of Air Pollution Sources and Emissions

-------------------------------------------------·-----·-·· "" .... _ Source type

1. Dust producing processes

2. Combust ion

Category

Crushing, grinding Screening uemo 1i tion l'i.i llin g

Fue 1 burning

Motor vehicles Refuse burning

3. Manufacturing Processes Metallurgincal plants

Chemical plants

waste recovery

4. Agricultural Activities Crop spraying and dusting Fie 1 d burn in g

5. Solvent

6. N uc lear Energy Activities

frost damage

Spray painting

Inks

Solvent cleaning

Ore r1reparation

Fuel fabrication N.uclear fission Spent fuel processing Nuclear device testing

Examples

Road Mix plants Urban renewal Grain elevator

Pollutants

------Mineral and organic particulates

Harne heating units paws r plants

an d 0 x ide s a f s u 1 f u r ca..Yho-1\ oxides of nitrogen,~~ monoxide, smoke, flyash organic vapour metal-

Auto, buses and trucks Community and ho~se incinerators, open burning dumps

Smelters, steel mills, a 1 urn i n i urn r e f i n e r i e s ~etroleum refineries, pulp mills, fertili­sers plants c e me n t m i 11 s Metal scrap yards

oxide particles and odor

a. 'Y"se "'- '·G Metal fumes (lead,~ariQR andzinc) fluorides and oxides of sulfur H S, oxides of sulfur, ffuoride, organic vapour particles etc J

Smoke, soot, organic ~ va.poc-o.,..., ·ii;

Pest and weed control Organic phosphates 1 Stubble & slash burningChlorinated hydrocarbonsJ

arsenic; lead Smudge pots

A ut om obi le as s e m b 1 y , furniture and appli­ances finishing Photogravure & print­ing Dry c le ani n g , d e g r e a­sing

Crushing, grinding, screening Gaseous diffusion Nuclear reactors Chemica 1 s StJa rat ion Atmospheric explosions

Smoke, flyash, soot

Hydrocarbons and other organic vapors

U rani u m an d be r y 11 i urn ~ c::Lu..s.: t:; .

Fluoride, Argon-41 Iodine-131 R ad i o a c t i v e fa ll o ut (strontium-90, CS-137, carbon-14)

The atmospheric pollution occurs primarily in

the lower layers of the atmosphere and the long term

changes due to pollution affect the entire atmosphere

of the earth.

The period for which a pollutant remains in the

at~osphere is also important in the evaluation of atmos-

pharic pollution~ The average residence time of some

substance in the atmosphere is indicated in Table 1.3.

Table 1.3 Time of residence of substance in the

Atmosphere

Average residence time

in the atmosphere

-He 107 years

N2 106 to 2 X 10

7 years

02 .;, 5 X 10 3 to 1 o4 years

co 2 5 to 10 years

H2 4 to 8 years

CH 2 4 to 7 years

N 20 2. 5 to 4 years

03 o.3 to 2 years

co o.2 to 0 • 5 years

NO 2 8 - 11 days

H 20 10 days

so 2-4 10 days

NO 9 days

1'3

NH 3 5 - 6 days

NH+ 4 6 days

No; 5 days

so 2 2 to 4 days

H2S 0. 5 t 0 4 days

0 rg-anic- carbon 2 days

It is stated that the amount of SO 2 in the atmosphere

decreases to one half within 24 hrs, i.e. only about 6%

of the original amount remains in the atmosphere after

4 days. This time is shortened by washing out during

rainy weather (Bretschneider & Kurfurst, 1987).

<t. The time that the fine particles remain in the

atmosphere varies from one to five days in the immediate

vicinity of the earth surface, five to ten days in the

t r o p o s p he r e , and o f t he order o f one y e a r in t h a up p e r

layers.

t:ft'ects of the Air E_oll!:!,tion

There are four main types of.damages caused to the

enviornroont by air pollutants.

1. Damage to human health

2. Dam3ge to_vegetation

3. Damage to the materials

14-·

4. Weather and climatic changes (Atmoshpheric

effects)

1. Q~mage to human health : Acute air pollution

episodes represent abrupt and unusual exposures to high

pollution concentrations and ~reduce the most obvious

15

effects on health. The long term or chronic exposure to

moderate levels of suspended particulate matter and sulphur

dioxide also appear to impair health. The chronic bronchitis,

asthma and pulmonary emphysema have been considered to be

due to suspended particulate matter and sulphur dioxide.

An additional consideration with fine particulates

in health studies is that the type of particle is impor­

tant. Sulphates ·exist in 5 to 20 percent of suspended

particulate matter in urban areas. Ths s u~phates may be

responsible for increased asthma attacks, aggravation of

heart and lung disease, lowered resistance to respiratory

disease in chi·ldren (Lave & Seskin, 1977). The photo­

chemical oxidants, as expressed in tha form of nose and

eye irritation. Oxides of nitrogen anhance suscepti­

bility to respiratory infections, nitrogen oxides may

lead to increased airway resistance and increased sensi­

tivity to bronchoconstrictors in sensitive individuals.

Carbon monoxide is absorbed through lungs and reacts with

haemo proteins, especially with haemoglobin of the blJod.

This in turn results in a reduction of the oxygen carrying-

capacity of blood and also interferes with the r8lease

of oxygen which is carried to tissues. Carbon monoxide

has an affinity for haemoglobin, that is 200-240 times

greater than that of oxygen and carboxy haemoglobin is

therefore a more stabl8 compound than oxyhaemoglobin.

These are some of the major effects· on the human health

caused by the -air pollutants (Derek ~lsom, 1987).

2. Qama~ 12 vegetation : Vegetation may be adver­

sely affected by excessive quantities of air borne par­

ticles. Particles cover leaves and plug stomata, thereby

both reducing the absorption of carbon dioxide from the

atmosphe!'e and the intensity of sunlight reaching the

interior of th3 leaf, and suppressing growth of some

plants •. Specific particles such as fluorides cause addi­

tional damage. Sulphur dioxide cause acute injury to

the plants. the long term exposure causes mild chlorosis

of leaf in many plants (Derek Elsom, 1987).

The photochemical oxidants cause acute and chronic

injury to plants, causing necrotic patterns of leaves,

growth alterations, reduced yields and reductions in

the quality of the plant products. Prolonged exposure

to the oxides of nitrogen will suppress the plant growth.

(Wark & Warner, 1981). These are some of the effects

caused by air pollutants on vegetation.

IG

3. Q~~ to~ater~~~ : Soiling of buildings in

cities is one 'of the more obvious manifestation of atmos-

pheric pollution.

Suspended particulate matter soils or blackens the

surface of material. Sulphur dioxide can produce subs-

tantial damage to materials. Lime stone, sandstone, roof-

ing slats and mortar of buildings, and monuments can be

severely damaged. The calcium carbonate in lime stone

and other building materi~l is readily coverted into solu-

ble calcium su:lphate. The increased volume associated

with this chemical change cause scaling, blistering and

disintegration of surface, With the loose material being

<t washed away by rain.

Fabrics, leather, paper, electrical equipment,

paints are all adversely affected by sulphur dioxide.

The textiles such as nylon ·are especially susceptible

to suliJhur dioxide and sulphuric acid aerosols. Carro-

sian of metals~ especially iron, steel, zinc, copper and

nickel is accelerated by the presence of sulphur dioxide

Which encourages the formation of s.ulphuric acid on metal

surface under moist conditions.

IT

These are some of the affects caused by air pollutants

to materials (Derek Elsom, 1987).

4. ~tmos£~~£1£ ~f~£~~ : One of the most obvious

effects of pollutants in the atmosphere is the reduction in

visibility caused by the absorption and scattering of

solid and liquid aerosols.

18

Sulphates and nitrates arise from combustion proce­

sses. Sulphates tend to be smaller than nitrates and

therefore play the major role in reducing visibility in

urban ar~as (Eggleton, 1969). Suspends~ particulate matter

and sulphur dioxide are often regarded as the traditional

pollutants of urban areas. The highest levels of these

pollutants occur during the sulphurous smogs to which

most ·large industrial cities have been subjected to in the

past.

Nitrog'l:!n dioxide absorbs visible light (and strongly

absorbs ultra violet radiation) and will cause an appre­

ciable reduction in visibility. An increase of nitrous

oxi9e concentration in the atmosphere may also lead to a

decrease in the stratospheric Ozrine concentration which

may also affect surface temperatures (Derek Elsom, 1987).

The presence of carbon dioxide in the atmosphere acts

as a blanket td decrease the heat loss of the planet. The

'green house' effects of carbon dioxide is thus an impor­

tant temperature regulator for the globe (Lamb, 1984).

These are some of the effects caused by the air pollu­

tants on atmosphere.

.I

/

19

~ir follution in India

·In India, air pollution is becoming an increasingly

important aspect of environmental pollution in the wake of

rapid industrialisation, and has reached a stage of concern

in many cities.

In addition to various important industries, the

other important source of air pollution in the Indian

environment is the domestic consumption of low grade fuels,

resulting in intensely smoky atmosphere, affecting visibi­

lity. Contribution of the fine dust by the deserts and

other open dry fi,elds and unpaved streets is none less

compared to others which has resulted in a disproportion­

ally higher pollution due to dust. These· natural factors

combined with human activities have caused heavy pollution

of the urban a'ir with the suspended particulate matter.

National air quality monitoring network launched

in 10 major cities of India shows the following air

quality status. This work was carried out by National"

Environmental Engineering Research Institute, Nagpur.

Table 1.4 Air Quality Status of Ten cities - 1985

--------....----------~-·-------- --------Cities SPM sox NOx

ug/m 3 ug/m 3 ug/m 3

----- --- --------------1. ·Ahmedabad 350.71 21.0 9.34

2. Bombay 227.2 22.o 77.97

3. Calcutta~ 356.9 6 48.48 140.24

2.0

4. Coc hin 103.99 10.04 10.26

s. Delhi 409. 8 6 61.34 43.86

6. Hyderabad 235.38 8.9 5 10.74

7. Ja ip ur 33 4. 52 .3.1 11. 36

8. Kanpur 30 1· 34 5.0 7.3

9 • Madras 119.47 s. 37 11.0

10. Nag pur 197.83 3 5. 0 5 12.8 2

(So urea . Air Quality Status of Ten Cities, 1985 - NEERI) •

Automobile traffic adds significantly to the air

pollution in city roads. There are three main types of

vehicles plying on Indian toadso They are powered by

internal combustion engines, which_can be grouped into

three general classes (Pundir, e.t al,19B·:S.) viz. -

1. Pas~enger cars powered by 4-stroke gasoline

eng ina s.

2. Two and three Wheelers powered mostly by small

crank case, scavenged by 2-stroke. gasoline engines.

3. Buses and trucks equipped mostly with 4-stroke

diesel engines.

90% of the pollution in Inoian cities is due to

automobile exhaust. The worst offenders are not the diesel

powered buses and trucks, but the two stroke vehicles.

The two and three wheelers constitute three-fourth of

vehicle popul(:l.tion Table 1.5 (Mathur, 1983; Surface Trans­<t.

port, 1989- Personal communication).

T A 8 LE. 1. 5

Registered motor vehicles in metropolitan cities of India (category-wise) as on 31st March 1989

Metropolitan all two Three wheelers cities vehicles wheelers Passen- Goods

gers cars

Bombay 588158 221531 24577 14774 235707

calcutta 424372 167813 3082 13067 169

Delhi 1465592 1008924 54736 292853

Madras 485029 338486 5700 751 107020

/

Source: Ministry of Surface Transport (unpublished data)

jeeps Taxis Buses Trucks Trac- Trai- OtheFs tors lers

13250 34338 7127 32528 977 927 2422

537 16883 12190 32140 4?l14 5246

9210 16622 83277

320 6964 2192 17296 413 420 5467

The diesel engine has a substantial emission pro­

blem which is quite different than that of gasoline en­

gines. It ·produces large amounts of particulates com­

prising of soot and adsorbed organics (Mathur, 1983).

The particulate matter is a complex mixture of

pure carbon plus hundreds of organic compounas. The

particulate is· extremely fine and light with a flour.­

like .consistency. More than 50/& of it is less than 0.5

microns in size (Howitt & Montierth, 1981).

Wilson, ~tal., (1973) proposed that partially de_

composed fuel vapors mix with hot combustion products

and form acetylene. The acetylene is then believed to

combine with oxygen to for~ water and carbon particleso

These particles grow through continu~ reactions with

acetylene and ultimately agglomerate to rarm soot par­

ticles. The individual particle diameters varied within

the range of 150-500 A0

with 250 A0 being the approxi­

mate average (Vuk, et al, 1976).

The study conducted by National C::nviranmental

Engineering Research Institute, Nagpur, revealed that

high level of pollution at traffic intersections is

attributed to the fallowing factors :

1. traffic conditions

2. law speed of vehicles during peakhours

3. law grade fuels

zz.

4. average age of vehicles a.re more than ten years

5. poor maintenance of vehicles

a. tail pipe blockage

b • c lo g g e d a i r f i 1 t e r s

c. poorly tuned curburettors

d. leaking piston rings

6. multiRlicity of vehicles with slow and fast

moving vehicles in the same lane

All these factors will increase the level of pollu­

tants in exhaust (Swaminathan & Sunderesan, 1982; Central

Board fa~ the preventlon and control of water pollution,

New Uelhi, 1982).

Delhi has the highest rate of vehicular traffic

compared with other cosmopolitan cities in the country.

It has twice the number of vehicles as Bombay, three

times more than Calcutta and Madras Table- 1.6 (Ministry

a f S u r f 3 c e T ran s p a r t , 1 9 8 9 - P e r s on a 1 c o mm un i c a t ion ) •

The motor vehicles discharge through the tail pipe

significant amounts of pollutants like carbon monoxide,

23

unburnt hydrocarbons, lead compounds, oxides of nitrogen,

soot, aldehydes, ketones and polyaromatic hydrocarbons and

many 'Other pollutants. (Tamakuwala, 1983).

As has be 8 n me n t ian e d e a r 1 i e r , P A H a r 8 c a us in g <t

increasing environmental concern because of their

potential cancinogenicity mut~genicity. In the present

T A B LE ·: ... J .. !.§.

Registered motor vehicles in the four metropolitan cities of India 1980-1989

Metropolitan cities

Delhi

Bombay

Calcutta

Madras

·1980

487

283

161

104

(in thousands)

Year as on 31st March

1985 1986 1987

841 961 1112

441 480 524

286 321 351

201 288 373

Source: Minis~ry of Surface Transport

*(unpublished data)

1989*

1465

588

424

485

A

~ \)

I !1)

> u. 0

IIOO

1000

BAR 'DIA612.AM :514011\liN<:=, IHE. t-4UWlBE'-Q.. OF VEHic:::.t...es 12.ECSI:STE.P-e..:P

FouR. IVlE.-rQ.os , "'BOIV\8AY, c:..AL..c.u-r-rA. J :OEL...H a, a. MA"D~.

yeo A QS __,.....

IN THE

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study, an attempt has been made to obtain the ambient profile

and also to ascertain the possible contribution of automo-

bile exhaust to this profile in Delhi. The study involves

1. Assessing'the concentration of PAH at representative

busy traffic intersections

2. Assessing the PAH concentration in ambient air

3~ Ascertaining the effects of the meteorological

parameters of PAH concan trations

4. Assessing the seasonal and diurnal variation in the

PAH concentration

6. Photochemical degradation of PAH compounds

Since they are contributed in the atmos~here by

automobile exhaust, the ambient profile of PAH depends

on the traffic density. ~