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Atmospheric Environment 39 (2005) 59–71

www.elsevier.com/locate/atmosenv

Air toxics in ambient air of Delhi

Anjali Srivastavaa,�, A.E. Josepha, S. Patila, A. Morea, R.C. Dixitb, M. Prakashb

aMumbai Zonal Laboratory, National Environmental Engineering Research Institute (NEERI), 89/B, Dr. A.B. Road,

Worli, Mumbai-18, IndiabDelhi Zonal Laboratory, NEERI, Chandarwal Waterworks. No. II, Lala Shamnath Marg, Delhi-54, India

Received 28 May 2004; accepted 14 September 2004

Abstract

Volatile organic compounds (VOCs) are major group of air pollutants which play critical role in atmospheric

chemistry. It contributes to toxic oxidants which are harmful to ecosystem human health and atmosphere. Data on

levels of VOCs in developing countries is lacking. In India information at target VOCs as defined in USEPA

compendium method TO-14 is almost totally lacking. The present work deals with estimation of target VOCs at 15

locations in five categories namely residential, industrial, commercial, traffic intersections and petrol refueling stations

in Delhi, the capital of India. The monitoring was carried out during peak hours in morning and evening each month

for a year in 2001. Ambient air was adsorbed on adsorbent tubes, thermally desorbed and analyzed on GC–MS. The

results show that levels of VOCs are high and stress the need for regular monitoring programme of VOCs in urban

environment.

r 2004 Elsevier Ltd. All rights reserved.

Keywords: Air toxics; VOCs; Delhi; Ambient air

1. Introduction

Urban air pollution is rapidly becoming an environ-

mental problem of public concern from the last few

decades. Industrial growth, increased transportation,

fossil fuel burning and high rate of urbanization in

developing countries have resulted in increase of

pollutants concentrations as well as the category of

pollutants. Volatile organic compounds (VOCs) are a

major group of pollutants, which have now become a

cause of concern worldwide. VOCs are harmful to

ecosystem, human health and atmosphere (Edgerton et

al., 1989; Atkinson, 2000; Derwent, 1995; Kuran and

Sojak, 1996; Dewulf and Van Langenhove, 1997). Many

VOCs like benzene and tetrachloroethylene have been

e front matter r 2004 Elsevier Ltd. All rights reserve

mosenv.2004.09.053

ing author.

ess: srivastv@vsnl.com (A. Srivastava).

proved to be a potent carcinogen (USEPA, 1990;

Wallace, 1986; Tancrede et al., 1987). Some VOCs are

highly toxic and mutagenic (Duce et al., 1983; Sweet and

Vermette, 1992; Kostianen 1995; Mukund et al., 1996).

Large numbers of VOCs undergo complex photochemi-

cal reactions giving rise to highly toxic secondary

pollutants, such as tropospheric ozone (Aikin et al.,

1982) and PAN (Crutzen, 1979), which are injurious to

human health and vegetation. In the United States,

VOCs are regulated under the criteria pollutant program

because they are precursors of ozone. USEPA has

identified 189 hazardous air pollutants (HAPs) out of

which 97 are VOCs (US Clean Air Act, Amendment,

1990; Ruddy and Carroll, 1993). Sources of VOC

emission are both anthropogenic and natural. It is thus

essential to control anthropogenic emissions of VOCs.

Knowledge of ambient levels of VOCs is necessary to

evolve a proper strategy to control tropospheric ozone

d.

ARTICLE IN PRESSA. Srivastava et al. / Atmospheric Environment 39 (2005) 59–7160

build up and maintain healthy air quality. Information

on VOC levels for Indian cities is lacking. Levels of

benzene, toluene, xylene and ethylbenzene at few

locations in some cities of India are available (Srivastava

et al., 2000; Chattopadhyay et al., 1997; MohanRao et

al., 1996). However, total VOCs and concentrations of

target VOCs specified in the USEPA Compendium

Method TO-17 are almost totally lacking. An attempt

has been made to determine the ambient levels of target

VOCs in the urban atmosphere of Delhi, the capital of

India, during the year 2001.

2. Study area

Delhi, the capital and one of the largest cities in India,

lies at an altitude of between 700 and 1000 ft. It covers

an area of approximately 1500 km2 situated on the

banks of Yamuna River. Delhi is bordered on the east

by the state of Uttar Pradesh and on the north, west and

south by Haryana, with a population of 13.79 million.

Delhi has become a nucleus of trade, commerce and

industry in the northern region of India. Government

office complexes are a major source of employment and

the city is also home to important radical, agricultural

and educational institutions. Steady increase in indus-

trial units has been witnessed despite the introduction of

planning restrictions on large industries.

Delhi sprawls an area of 1500 km2. Its east–west

length is approximately 51.9 km and the northwest

width approximately 48.48 km. The spread of Delhi is

somewhat circular. The transportation network in Delhi

is predominately road based. Delhi has the largest road

length of 1284 km/100 km2 of area in India. The road

network in the city is 22487 km long. Fig. 1 gives the

composition of registered vehicles in Delhi in 2002.

Engineering, clothing and commercial activities pre-

dominate, although electrical goods are gaining impor-

tance. Most industries are located in the west, south and

southwest of the city. Northwesterly winds often drag

pollution from western industrial areas across the city. It

has been recommended that all future industrial devel-

opments are limited to the southeast to avoid such

Fig. 1. Composition of registered vehicle during 2002.

problems and the Okhla industrial estate has recently

been built in this area. Increasing industrial productivity

combined with rapid urbanization means that there is a

greater demand for energy in Delhi that can be supplied;

therefore, the industry cannot generate at full capacity.

Delhi has two major thermal power plants, which

are not sufficient to cater to the total power need of

the city. Generator sets are thus used in commercial,

residential and industrial areas as backup power. All

these activities have led to increased fuel demand and

accrued into deteriorating air quality. Cooking, gen-

erator sets, various internal combustion engines, burn-

ing of organic wastes landfill, sewage treatment plants,

slums and open defecation are some of the sources of

VOCs in Delhi.

Delhi has a tropical steppe climate. The general

prevalence of continental air leads to relatively dry

condition with extremely hot summers. Monthly mean

temperature ranges from 14.3 1C in January (minimum

3 1C) to 34.5 1C in June (maximum 47 1C). The annual

mean temperature is 25.3 1C. The main seasonal climatic

influence is that of monsoon, typically from June to

October. The mean annual rainfall total is 71.5mm.

Maximum rainfall occurs in July (211mm). The heavy

rains of the monsoon act as a ‘‘scrubber’’. Wind speeds

are typically higher in summer and monsoon periods; in

winter, clams are frequent. Annual windrose is given in

Fig. 2.

3. Sampling locations

Fifteen locations in five categories namely residential,

commercial, industrial, traffic junctions and petrol

pumps were selected for monitoring of VOCs (Fig. 3).

The sites were selected on the basis of predominant

activities in the area. The residential areas selected were

Janakpuri, Kalkaji and Mayur Vihar Phase II. At

Janakpuri, the sampler was located on the boundary

wall of a central school situated in the middle of

residential colonies. At Kalkaji, sampling was carried

out opposite the municipal primary school within

residential blocks, and at Mayur Vihar Phase II,

sampling was done at a primary school. All these

locations are typically residential and air quality is

influenced mainly by domestic activities, vehicular

movement, roadside eatouts and open burning of leaves

and solid waste.

Locations in the commercial area include Karol

Baugh, opposite the National Restaurant, which is a

middle class market area. Karol Baugh is a very busy

market place with vehicular traffic consisting of heavy-

duty trucks, buses, two wheelers, three wheelers and

cars. Cannaught Place (in front of Regal Cinema) is a

market area with broad roads. This is a posh market

place and traffic consists of three wheelers, two wheelers,

ARTICLE IN PRESS

Fig. 2. Annual wind rose pattern for Delhi.

Fig. 3. Sampling locations in national capital region—Delhi.

A. Srivastava et al. / Atmospheric Environment 39 (2005) 59–71 61

ARTICLE IN PRESSA. Srivastava et al. / Atmospheric Environment 39 (2005) 59–7162

buses and cars. Cinema halls, restaurants, roadside

eatouts and markets are in plenty. Lajpat Nagar is a

crowded market place in South Delhi. Air quality is

mainly influenced by generator sets, vehicular move-

ment, roadside eatouts and markets.

In the industrial category the three notified industrial

areas namely Jhilmil, Okhla Phase I and Mayapuri were

chosen in the study. All the three sites are purely

industrial with no mixing of residential or commercial

areas. The location of monitoring carried out in Jhilmil

industrial area was opposite to Para Sheild Cables

manufacturing industry. The area is surrounded by

other cable and tyre manufacturing industries. Monitor-

ing in Okhla Phase I was carried out at the open terrace

of Enviro Tech Pvt Ltd. This industry is also surrounded

by other industries. In Mayapuri, the sampling was

conducted in an industry behind Car Service Centre near

the Delhi Transport Corporation bus stand and metal

forging company.

Locations at traffic intersections include ITO, Raja

Garden (Raja Garden Flyover Crossing at Police help

post), Shakarpur Crossing (Shakarpur Crossing oppo-

site police post). All these traffic intersections are very

busy intersections. Monitoring was carried out at the

kerbsides near traffic intersections. During peak hours

traffic jams are frequent in these locations. The average

vehicular speed is atmost 20–25 kmh�1 at these loca-

tions.

The refueling stations selected for the study were

petrol pumps at Cannaught Place at Janapath next to

Imperial Hotel, IIT Crossing and Race course. Sampling

was carried out in the center of petrol pump where

vehicles halt for refueling.

4. Sampling and analytical

4.1. Methodology

Levels of VOCs in ambient air have been determined

by adsorbing ambient air at a uniform flow rate on

specially fabricated activated-charcoal cartridge fol-

lowed by thermal desorption and detection on Varian

GC–MS in accordance with TO-17 compendium of

methods for the determination of toxic organic com-

pounds (USEPA, 1999).

A battery-operated personal air sampler (model

Staplex PST 3000 A) was used to sample air at the rate

of 20mlmin�1 through adsorption cartridge containing

activated charcoal. Uniform flow rate was maintained

using a rotameter. The monitoring schedule followed 4

hourly samples during peaks hours, i.e. 08.00–12.00 and

17.00–21.00 h every month during the period August,

2001–July 2002. Sorbent carbon cartridges were fabri-

cated from stainless-steel pipes (SS-316) having a length

of 15 cm with internal diameter of 4mm and external

diameter of 6mm with caps on both sides. Analytical

grade activated carbon was heated at 200 1C for 12 h and

cooled in vacuum desiccators. Approximately 800mg of

preheated cooled activated charcoal was filled in the

cartridge with glass wool plugs on either side of the

sorption cartridge. Desorption from sorbent cartridge

was carried out by heating at 200 1C for 20min. Two

tubes were connected in series. When the concentration

in the second tube was more than 5% of total

concentration it was assumed that break through

occurred.

As soon as the pump was turned off the cartridges

were removed and capped tightly and sealed in plastic

bags. The tubes were stored in refrigeration. Blank

cartridges were also stored in identical condition.

Varian GC–MS (Model Saturn 3) with injection mode

of sample introduction with DB 624 capillary column of

30m length, 0.32mm interval diameter and 1.8 micro-

film was used. Helium gas with flow rate of 1mlmin�1

was used as carrier gas with split ratio 1:25, GC oven

was programmed for 35 1C hold for 2min and ramped

to 210 1C with rate of 10 1C. Ion trap temperature was

maintained at 125 1C while acquisition mass range was

from 35 to 260 amu in E1 model 100 ml of desorbed

sample was injected into the GC.

Quantification of VOCs was carried out using VOC

Mix 15 of Dr. Erhenstrofer as standard with an accuracy

of 715%.

5. Results and discussions

Table 1 presents the list of VOCs identified in different

categories of locations in Delhi. As many as 52 VOCs

have been identified in residential areas. Eleven VOCs

amongst these are included in the list of HAPs of CAAA

Title III of USEPA and seven of them are identified as

mobile source air toxics. In commercial areas, 59 VOCs

have been identified out of which 12 are HAPs and eight

mobile air toxic. In industrial areas 61 VOCs have been

identified including 13 HAPs and five mobile air toxics.

At traffic intersections 54 VOCs have been identified,

which include 15 HAPs and seven mobile source air

toxics. At the petrol pumps 50 VOCs were identified out

of which 12 are HAPs and four are mobile source air

toxics.

5.1. Residential areas

At Janakpuri, concentrations of total VOCs ranged

from 23.74 to 52.16mgm�3. The concentration of total

VOCs at Kalkaji ranges from 92.46 to 162.68 mgm�3. At

Mayur Vihar concentrations ranged from 1.13 to

30.45mgm�3. Seasonal and annual averages are

presented in Fig. 4. Higher concentrations are

observed during winter; however, at Janakpuri, higher

ARTICLE IN PRESS

Table 1

VOCs identified at various locations at Delhi

Case no. Compound name Residential Commercial Industrial Traffic intersection Petrol pump EPA–MS

56-23-5 Carbon tetrachloride (M J K)a (Ka L)a (I S)a (Rc Ca IT)a b

57-14-7 1,5-Dimethylydrazine (O My) b

67-66-3 Chloroform (M J K)a (Ka C L)a (My)a (I R S)a (Rc Ca IT)a b

71-43-2 Benzene (M J K)a (Ka C L)a (J O My)a (I R S)a (Rc Ca IT)a b,c

71-55-6 1,1,1–Trichloroethane (J)a (R S)a (Ca)a

74-34-2 Ethane 1,1,2,2 tetrachloride (Ka C)a (S)a

74-86-2 Acetylene (M) (R S) (Ca IT) b,c

74-87-3 Chloromethane (M J K) (Ka C) (O My) (I S) (Rc Ca) b

74-97-5 Bromochloromethane (J K)a (Ka C)a (R)a (Ca)a

74-98-6 Propane (M) (C) (O My) (Rc IT)

75-07-0 Acetaldehyde (M J K) (Ka C L) (I R S) (Rc Ca IT)

75-09-2 Methylene chloride (M J K)a (Ka C L)a (I R S)a (Rc Ca IT)a b

75-15-0 Carbon disulfide (M J) (J) (R S) (Rc Ca) b

75-34-3 1,1–Dichloroethene (M J)a (Ca IT)a

75-55-6 1,1,1-Trichloroethane (Ka C L)a

75-69-4 Trichloro fluoromethane (M K) (C) (S)

75-83-2 2,2-Dimethylbutane (M J K) (Ka C L) (Rc Ca IT)

78-78-4 2-Methylbutane (Ka) (O) (I R S) (Rc Ca IT)

79-01-6 Trichloroethylene (K)a (IT)a b

79-29-8 2,3-Dimethylbutane (R)

91-20-3 Naphthalene (M J K)a (Ka C L)a (I R S)a (Rc Ca IT)a b,c

95-47-6 o-Xylene (M J K)a (C L)a (I R S)a (Rc IT)a b

95-63-6 1,2,4-Trimethylbenzene (M J K)a (Ka C L)a (I R S)a (Rc Ca IT)a

96-14-0 3-Methylpentane (R S)

96-37-7 Methylcyclopentane (M J K) (C L) (R S) (IT)

98-06-6 t-Butylbenzene (L)a (IT) a

98-82-8 Isopropylbenzene (M J K)a (Ka C L)a (I R S)a (Ca IT) a b

99-87-6 p-Isopropyltoluene (M)a (C)a (I)a (Rc Ca IT)a

100-41-4 Ethylbenzene (M J K)a (Ka C L)a (J O My)a (I R S)a (Rc Ca IT)a b,c

103-65-1 n-Propylbenzene (M J K)a (C L)a (My)a (I R)a (Rc IT)a

104-51-8 n-Butylbenzene (IT)a

105-05-5 1,4-Diethylbenzene (My) (I) (Rc)

106-42-3 p-Xylene (M K)a (Ka C L)a (J O My)a (I R S)a (Rc Ca IT)a b

107-06-2 1,2–Dichloroethane (Rc)a

108-38-3 m-Xylene (M J K)a (Ka C L)a (J O My)a (I R S)a (Rc Ca IT)a b,c

108-67-8 1,3,5-Trimethylbenzene (M J K)a (Ka C L)a (J O My)a (I R S)a (Rc Ca IT)a

108-87-2 Methylcyclohexane (C L) (O My) (Rc Ca)

108-88-3 Toluene (M J K)a (Ka C L)a (I R S)a (Rc Ca IT)a b,c

110-54-3 n-Hexane (M J K)

111-66-0 1-Octene (M) (O) (S)

115-07-1 Propene (Ka C L) (I R S)

115-11-7 2-methyl 1-Propene (M K) (Ka C L) (J My) (I R S) (Ca IT)

120-21-4 n-Undecane (Ka C L)

124-18-5 n-Decane (M J K) (Ka C L) (I R S) (Rc Ca IT)

135-98-8 Sec butyl benzene (K)a (C L)a (Rc)a

141-93-5 1,3-Diethylbenzene (M J K)a (Ka C L)a

142-28-9 1,3–Dichloropropane (R)a (Rc)a

513-35-9 1,2,3,5-Tetramethylbenzene (M) (My) (Rc)

541-05-9 Hexamethylcyclotrisiloxane (M J K) (Ka) (J O My) (R S) (Rc Ca IT) b

563-46-2 2-Methyl-1-butene (M) (Ka C) (J O My) (I R S) (Rc Ca)

565-59-3 2,3-Dimethylpentane (M J K) (Ka C L) (I S) (Rc Ca)

584-94-1 2,3-Dimethylhexane (M J) (C) (O My) (R) (Rc)

589-43-5 2,4-Dimethylhexane (M J) (O My) (I R S)

591-76-4 2-Methylhexane (J K) (Ka C) (My) (R S) (Rc)

592-41-6 1-Hexene (M J) (Ka C L) (J O My) (I R S)

594-20-7 2,2–Dichloropropane (K)a (R S)a (Rc)a

611-14-3 1-Ethyl –2-Methyl benzene (M J) (C) (J O My) (Rc Ca)

A. Srivastava et al. / Atmospheric Environment 39 (2005) 59–71 63

ARTICLE IN PRESS

Table 1 (continued )

Case no. Compound name Residential Commercial Industrial Traffic intersection Petrol pump EPA–MS

616-12-6 3-Methyl-2-Pentene (C)

619-99-8 3-Ethylbenzene (J)

620-14-4 1-Ethyl-3-Methylbenzne (C) (I R) (Rc)

622-96-8 1-Ethyl-4-methyl benzene (K) (C L) (J O) (R)

629-50-5 Tridecane (C)

674-76-0 (E) –4-Methyl-2-Pentene (C) (My)

691-38-3 (2)-4-Methyl-2-Pentene (M) (Ka C L) (My) (R S)

763-29-1 2-Methyl-1-Pentene (I)

933-98-2 1-Ethyl –2, 3-dimethyl benzene (M) (C) (My)

1120-21-4 n-Undecane (M J K)

1502-38-1 Methylcyclooctane (C) (J) (R)

1640-89-7 Ethylcyclopentane (Ka C) (O My) (I RS)

1678-91-7 Ethylcyclohexane (M) (C) (My)

1730-94-9 4-Methylnonane (My)

2213-23-2 2,4-Dimethylheptane (M) (C) (J O My) (R S) (IT)

2216-34-4 4-Methyloctane (M) (C) (J O) (I R S) (Rc Ca)

2532-58-3 Cis-1,3-Dimethylcyclopentane (My)

4461-48-7 4-Methyl-2-Pentene (C) (My)

7642-09-3 (Z)-3-Hexene (C)

13269-52-8 (E) –3-Hexene (C) (Ca)

Residential—M=Mayur Vihar, J=Janakpuri, K=Kalkaji; commercial—Ka=Karol Baugh, C=Cannaught Place, L=Lajpat Nagar;

industrial—J=Jhilmil, O=Okhla Phase II, My=Mayapuri; traffic intersections—I=ITO Crossing, R=Raja Garden Crossing,

S=Shakarpur Crossing; petrol pump—Rc=Race course, Ca=Cannaught Place, IT=IIT Gate.aVOC appearing in the USEPA list of Hazardous Air Pollutants in CAAA Title III.bVOC quantified using VOC Mix-15.cMobile source air toxic.

A. Srivastava et al. / Atmospheric Environment 39 (2005) 59–7164

concentration was observed during summer. This may

be due to some local activity during the period of

monitoring which has also led to the presence of carbon

tetrachloride and bromodichloromethane. Concentra-

tions of chlorinated compounds indicate open defeca-

tion, garbage rotting and sewage main hole breathing.

Use of generator sets is indicated by pollutants

associated with diesel internal combustion engines.

HAPs constitute 78.7%, 80.51% and 94.12% of total

observed VOCs and 58.84%, 52.22% and 64% of HAPs

can be classified as mobile source air toxics at Kalkaji,

Janakpuri and Mayur Vihar, respectively.

5.2. Commercial areas

At Karol Baugh concentrations of VOCs varied from

259.7 to 382.90mgm�3. The VOCs concentrations in the

commercial area of Cannught Place near Regal Cinema

was observed to range from 1167.22 to 1369.42 mgm�3.

At Lajpat Nagar, total VOCs ranged from 528.58 to

1336.87 mgm�3. Seasonal and annual averages of

observed VOCs concentrations are presented in Fig. 5.

Highest concentrations are observed during winter

followed by monsoon and summer. VOCs associated

with emissions due to diesel internal combustion engines

have been identified at all the three commercial

locations. The HAP component in total VOC annual

averages at commercial sites of Cannaught Place, Karol

Baugh and Lajpat Nagar are 88.85%, 94.73% and

97.68%, respectively. Mobile source air toxics compo-

nent of HAPs have been found to be 85.84%, 92.85%

and 93.44% at Cannaught Place, Karol Baugh and

Lajpat Nagar, respectively.

5.3. Industrial area

At Jhilmil industrial area, total VOC ranged from

174.74 to 367.55 mgm�3. At Okhla Phase I, TVOC

values in the range of 361.15–656.80 mgm�3 were

observed. TVOC concentrations at Mayapuri industrial

area ranged from 284.25 to 572.52mgm�3. Seasonal and

annual averages of observed VOC concentrations are

presented in Fig. 6. Higher concentrations are observed

in winter followed by monsoon and summer. The

industries in these areas are non-chemical. However,

degreasing activity is observed in considerable scale as

most of these are engineering units. Open defecation in

slums around the industrial area contributes to emis-

sions, which are classically considered to originate from

sewage sludge. Large-scale use of generators result

ARTICLE IN PRESS

Residential - Janakpuri

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Values of Benzene, Chloroform, Methylene chloride, Toluene, Carbon tetrachloride and Methane bromodichloro at Jankapuri, Benzene, Toulene, Chloroform and Methylene chloride at Kalkaji, Benzene, m-Xylene, Toluene, Methylene chloride and Chloroform at Mayur Vihar are expressed as 1/10 of observed values.

Fig. 4. Seasonal and annual average concentrations at Delhi residential areas.

A. Srivastava et al. / Atmospheric Environment 39 (2005) 59–71 65

in VOCs associated with diesel internal combustion

engines. HAPs constitute 87.16%, 97.61% and 99.83%

of TVOCs observed at Jhilmil, Mayapuri and Okhla

industrial areas, respectively. Mobile source air toxics

constitute 81.52%, 89.63% and 94.09% of HAPs at

these locations, respectively.

5.4. Traffic intersection

Monitoring at traffic intersections were carried out

not exactly at the intersection signal but on the kerbside

close to the traffic intersections. The distances of the

monitoring location from the traffic intersection was

approximately 100–200m. Seasonal and annual

averages of observed VOC concentrations are presented

in Fig. 7. ITO Crossing showed the least concentration

of TVOC amongst the traffic intersections. The con-

centrations observed ranged from 240.79 to

451.31mgm�3. Amongst the traffic intersections, Raja

Garden intersection showed maximum concentration of

total VOC as 733.82mgm�3 and minimum concentra-

tion of 541.38mgm�3. Shakarpur Crossing showed the

ARTICLE IN PRESS

Commerical - Karol Baugh

0

0.5

1

1.5

2

2.5

3

Ben

zene

Ben

zene

, 1,2

,4-

trim

ethy

l

Ben

zene

, 1,3

,5-

trim

ethy

l

Car

bon

Tet

rach

lori

de

Chl

orof

orm

Eth

ylbe

nzen

e

isop

ropy

lben

zene

Met

hane

brom

ochl

oro

m-X

ylen

e

Nap

htha

lene

Tol

uene

o-X

ylen

e

p-X

ylen

e

Monsoon

WinterSummerAnnual

Commercial - Cannaught Place

00.5

11.5

22.5

33.5

44.5

55.5

66.5

77.5

88.5

9

Ben

zene

Ben

zene

, 1,2

,4-

trim

ethy

l

Ben

zene

, 1,2

-di

chlo

ro-

Ben

zene

, 1,3

,5-

trim

ethy

l

Chl

orof

orm

Eth

ane,

1,1

,2,2

-te

trac

hl

Eth

ylbe

nzen

e

isop

ropy

lben

zene

Met

hane

brom

ochl

oro

met

hyle

nech

lori

de

m-X

ylen

e

Nap

htha

lene

n-P

ropy

lben

zene

o-X

ylen

e

sec-

buty

lben

zene

Tol

uene

Eth

ane1

1 1

tric

hlor

o

Car

bon

Tet

rach

lori

de

p-X

ylen

e

Tri

chlo

roet

hyle

ne

Monsoon

Winter

SummerAverage

Commerical - Lajpat Nagar

00.5

11.5

22.5

33.5

44.5

55.5

66.5

77.5

8

Ben

zene

Ben

zene

, 1,2

,4-

trim

ethy

l

Ben

zene

, 1,3

,5-

trim

ethy

l

Car

bon

Tet

rach

lori

de

Chl

orof

orm

Eth

ylbe

nzen

e

isop

ropy

lben

zene

met

hyle

nech

lori

de

m-X

ylen

e

Nap

htha

lene

n-P

ropy

lben

zene

o-X

ylen

e

sec-

buty

lben

zene

t-bu

tylb

enze

ne

Tol

uene

Eth

ane

1 11

tric

hlor

o

Met

hane

brom

odic

hlor

o

p-X

ylen

e

Monsoon

Winter

SummerAverage

Concentrations of Benzene, Ethylbenzene, Methane bromochloro, m-Xylene and Toluene at Karol Baugh, Benzene, m-Xylene and Toluene at Cannaught Place, Benzene and Toluene at Lajpat Nagar are expressed as 1/100 of observed values. Values of chloroform at Karol Baugh, Benzene 1,2,4 trimethyl, Benzene 1,3,5 trimethyl, Chloroform, Ethylbenzene, iso-Propylbenzene, Methane bromochloro, Methylene chloride, Naphthalene, n-Propylbenzene, o-Xylene and Carbon tetrachloride at Cannaught Place, Carbon tetrachloride, chloroform, Methylene chloride, m-Xylene and Methane bromodichloro at Lajpat Nagar are expressed as 1/10 of observed values.

Fig. 5. Seasonal and annual average concentrations at Delhi commercial areas.

A. Srivastava et al. / Atmospheric Environment 39 (2005) 59–7166

maximum concentration of 691.81mgm�3 and minimum

of 510.97mgm�3. Higher concentrations were obtained

during winter followed by monsoon and summer.

Higher temperatures during summer have led to

emissions associated with road asphalts. Emissions

pointing to diesel internal combustion engines are

observed. HAP component of observed TVOC at Raja

Garden, Shakarpur and ITO constitute 97.71%, 99.52%

and 97.61%, respectively. Mobile source air toxics

component of HAPs at these sites are found to be

93.38%, 92.96% and 88.01%.

5.5. Petrol pumps

At Cannught Place petrol pump TVOCs ranged from

651.51 to 787.89mgm�3. Total VOC concentrations at

IIT Crossing petrol pump were observed in the range of

388.30–639.44mgm�3. Maximum VOC concentration

ARTICLE IN PRESS

Industrial - Jhilmil

0

0.5

1

1.5

2

2.5

Ben

zene

Ben

zene

, 1,2

,4-

trim

ethy

l

Ben

zene

, 1,3

,5-

trim

ethy

l

Car

bon

Tet

rach

lori

de

Eth

ane

1 1

1tr

ichl

oro

Eth

ylbe

nzen

e

isop

ropy

lben

zene

Met

hane

brom

ochl

oro

met

hyle

nech

lori

de

m-X

ylen

e

Nap

htha

lene

n-P

ropy

lben

zene

sec-

buty

lben

zene

Tol

uene

Chl

orof

rom

p-X

ylen

e

Tri

chlo

roet

hyle

ne

MonsoonWinter

SummerAnnual

Industrial - Okhla

0

0.5

1

1.5

2

2.5

3

3.5

4

4.5

Ben

zene

Ben

zene

, 1,2

,4-

trim

ethy

l

Ben

zene

, 1,3

,5-

trim

ethy

l

Ben

zene

, 1,4

-di

chlo

ro-

Car

bon

Tet

rach

lori

de

Chl

orof

orm

Eth

ane1

1 1

tric

hlor

o

Eth

ene,

tric

hlor

o-

Eth

ylbe

nzen

e

isop

ropy

lben

zene

met

hyle

nech

lori

de

m-X

ylen

e

Nap

htha

lene

n-P

ropy

lben

zene

o-X

ylen

e

Tol

uene

p-xy

lene

MonsoonWinterSummerAnnual

Industrial - Mayapuri

0

0.5

1

1.5

2

2.5

3

3.5

4

4.5

5

Ben

zene

Ben

zene

, 1,2

,4-

trim

ethy

l

Ben

zene

, 1,3

,5-

trim

ethy

l

Ben

zene

, n-b

utyl

-

Car

bon

Tet

rach

lori

de

Chl

orof

orm

Eth

ane1

1 1

tric

hlor

o

Eth

ene,

1,1

-di

chlo

ro-

Eth

ylbe

nzen

e

isop

ropy

lben

zene

met

hyle

nech

lori

de

m-X

ylen

e

Nap

htha

lene

n-P

ropy

lben

zene

Pro

pane

, 1,2

-di

chlo

ro-

$

t-B

utyl

benz

ene

Tol

uene

Met

hane

brom

odic

hlor

o

o-X

ylen

e

p-X

ylen

e

Tri

chlo

roet

hyle

ne

Monsoon

Winter

SummerAnnual

Concentrations of Benzene, m-Xylene, Toluene at Jhilmil, Benzene, Ethylbenzene and Toluene at Okhla, Benzene and Toluene at Mayapuri are expressed as 1/100 of observed values. Carbon tetrachloride, Ethane 1,1,1 trichloro, Ethylbenzene, Methane bromochloro, Methylene chloride, n-Propylbenzene and Chloroform at Jhilmil, Carbon tetrachloride, Chloroform, Methylene chloride, m-Xylene and Napthalene at Okhla, Chloroform, Ethylbenzene Methalene chloride and Methane bromodichloro at Mayapuri are expressed as 1/10 of observed values.

Fig. 6. Seasonal and annual average concentrations at Delhi industrial areas.

A. Srivastava et al. / Atmospheric Environment 39 (2005) 59–71 67

observed at Race Course petrol pump was 819.02 mgm�3

and minimum concentration was 560.80mgm�3. Seaso-

nal and annual averages of observed VOC concentra-

tions are presented in Fig. 8. VOCs which can be

associated with evaporative emissions of petrol, com-

bustion of natural gas, and diesel internal combustion

engines have been identified at these locations. Degreas-

ing activities can also be traced close to petrol

pumps. Higher concentrations are observed during

winter. Minimum concentrations are observed during

summer. HAPs constitute 99.09%, 91.17% and

99.69% of observed TVOCs at IIT Crossing, Race

Course and Cannaught Place petrol pumps, respectively.

Mobile air source toxic component of HAPs at these

locations are found to be 89.24%, 89.88% and 94.96%,

respectively.

At all the locations total VOC concentrations are

dominated by benzene concentration.

ARTICLE IN PRESS

Traffic Intersection - ITO Crossing

00.5

11.5

22.5

33.5

4

4.55

5.56

Ben

zene

Ben

zene

, 1,2

,4-

trim

ethy

l

Ben

zene

, 1,2

-di

chlo

ro-

Ben

zene

, 1,3

,5-

trim

ethy

l

Car

bon

Tet

rach

lori

de

Chl

orof

orm

Eth

ylbe

nzen

e

isop

ropy

lben

zene

met

hyle

nech

lori

de

m-X

ylen

e

Nap

htha

lene

n-P

ropy

lben

zene

o-X

ylen

e

Tol

uene

Met

hane

brom

odic

hlor

o

p-X

ylen

e

MonsoonWinterSummerAnnual

Traffic Intersection - Raja Garden

00.5

11.5

22.5

33.5

44.5

55.5

66.5

77.5

8

Ben

zene

Ben

zene

, 1,2

,4-

trim

ethy

l

Ben

zene

, 1,3

,5-

trim

ethy

l

Ben

zene

, 1,3

-di

chlo

ro-

Chl

orof

orm

Eth

ylbe

nzen

e

isop

ropy

lben

zene

Met

hane

brom

ochl

oro

met

hyle

nech

lori

de

m-X

ylen

e

Nap

htha

lene

n-P

ropy

lben

zene

Pro

pane

2 2

dich

loro

Tol

uene

Eth

ane

1 1

1tr

ichl

oro

Car

bon

Tet

rach

lori

de

p-X

ylen

e

Tri

chlo

roet

hyle

ne

Monsoon

WinterSummerAnnual

Traffic Intersection - Shakarpur Crossing

00.5

11.5

22.5

3

3.54

4.5

55.5

6

Ben

zene

Ben

zene

, 1,3

,5-

trim

ethy

l

Car

bon

Tet

rach

lori

de

Chl

orof

orm

Eth

ylbe

nzen

e

isop

ropy

lben

zene

m-X

ylen

e

Nap

htha

lene

o-X

ylen

e

Pro

pane

2 2

dich

loro

Tol

uene

Eth

ane

1 11

tric

hlor

o

met

hyle

nech

lori

de

Met

hane

brom

odic

hlor

o

p-X

ylen

e

Monsoon

Winter

SummerAnnual

All values of Benzene are expressed as 1/100 of observed values and chloroform, Ethylbenzene, Methylene Chloride, m-Xylene and Methane bromodichloro at ITO Crossing, Chloroform, Ethylbenzene, Methylene chloride, m-Xylene and Toluene at Raja Garden Crossing, Carbon tetrachloride, Chloroform, Ethylbenzene, m-Xylene, Toluene and Methylene chloride at Shakarpur Crossing are expressed as 1/10 of observed values.

Fig. 7. Seasonal and annual average concentrations at Delhi traffic intersections.

A. Srivastava et al. / Atmospheric Environment 39 (2005) 59–7168

6. Directional dependence

Fig. 9 shows pollution rose for different locations

monitored in this study. Pollution rose for residential

site Janakpuri shows that pollutants are carried over

from north and northwest and at Kalkaji from north

and east. At Mayur Vihar concentrations of TVOCs

show the affect of activities in north, east and northwest

quadrant. In the north, all the three residential locations

are residential areas, important traffic intersections, and

industrial pockets. Thus, appreciable concentrations of

ethylbenzene, toluene, naphthalene and bromochloro-

methane, which are expected to originate from industrial

activity and traffic movement, are observed.

Amongst the commercial areas at Karol Baugh

pollutants are carried over from east, north and north-

west. At Cannught Place pollutants are carried over

from north and northwest, while concentrations at

Lajpat Nagar are predominately affected by the carry

over of pollutants from north. The commercial locations

ARTICLE IN PRESS

Petrol Pump - Cannaught Place

00.5

11.5

22.5

33.5

44.5

55.5

66.5

77.5

8

Ben

zene

Ben

zene

,1,

2,4-

trim

ethy

l

Ben

zene

,1,

3,5-

trim

ethy

l

Car

bon

Tet

rach

lori

de

Chl

orof

orm

Eth

ane,

1,2

-di

chlo

ro-

Eth

ylbe

nzen

e

met

hyle

ne

chlo

ride

m-X

ylen

e

Nap

htha

lene

p- I

sopr

opyl

tolu

ene

Pro

pane

2 2

dich

loro

Pro

pane

, 1,3

-

dich

loro

-

p-X

ylen

e

sec-

buty

lben

zene

Tol

uene

Monsoon

Winter

Summer

Annual

Petrol Pump - IIT Crossing

00.5

11.5

22.5

33.5

44.5

55.5

66.5

77.5

8

Ben

zene

Ben

zene

, 1,2

,4-

trim

ethy

l

Ben

zene

, 1,3

,5-

trim

ethy

l

Eth

ane

1 1

1tr

ichl

oro

Eth

ane

1 1

dich

loro

Eth

ylbe

nzen

e

Isop

ropy

lben

ezen

e

met

ane

brom

ochl

oro

met

hyle

nech

lori

de

m-X

ylen

e

Nap

htha

lene

n-P

ropy

lben

zene

p-Is

opro

pyl

Tol

uene

Tol

uene

Car

bon

Tet

rach

lori

de

Chl

orof

orm

p-X

ylen

e

Monsoon

Winter

SummerAnnual

Petrol Pump - Race Course

00.5

11.5

22.5

33.5

44.5

55.5

66.5

77.5

8

Ben

zene

Ben

zene

, 1,2

,4-

trim

ethy

l

Ben

zene

, 1,3

,5-

trim

ethy

l

Ben

zene

, ter

t-bu

tyl-

Car

bon

Tet

rach

lori

de

Chl

orof

orm

Dic

hlor

omet

hane

Eth

ane

1 1

dich

loro

Eth

ylbe

nzen

e

Isop

ropy

lben

ezen

e

m-X

ylen

e

Nap

htha

lene

n-bu

tylb

enze

ne

n-P

ropy

lben

zene

o-X

ylen

e

p-Is

opro

pyl

Tol

uene

Tol

uene

Tri

chlo

roet

hyle

ne

met

hyle

nech

lori

de

MonsoonWinterSummerAnnual

All values of Benzene are expressed as 1/100 of observed values. Values for Chloroform, Methylene chloride and Toluene at Cannaught Place, Methylene Chloride, Toluene, Carbon tetrachloride and Chloroform at IIT Crossing, Chloroform, Toluene and Trichloroethylene at Race Course Petrol pumps are expressed as 1/10 of observed values.

Fig. 8. Seasonal and annual average concentrations at Delhi petrol pumps.

A. Srivastava et al. / Atmospheric Environment 39 (2005) 59–71 69

are surrounded by road network and pollutants

originating from traffic movement (viz. benzene, to-

luene, etyhlbenzene, 1,3,5-trimethylbenzene and xylene

isomers are observed in considerable concentrations.

Directional dependence of concentrations in indus-

trial areas show carry over of pollutants mainly from

north and to some extent from northwest at all the three

industrial areas and from east at Mayapuri and Okhla.

The air quality at industrial locations is affected by

pollutants from the city activities and local activity.

Besides, solvents of specific industrial usages like

bromochloromethane, methylenechloride, VOCs which

can be associated with urban activity viz. traffic move-

ment and dry cleaning (benzene, carbontetrachloride,

ethylbenzene, toluene, trichloroethylene) have been

identified.

Directional dependence of observed concentrations

at traffic intersections show that carry over of

pollutants from north quadrant is predominant at all

the sites.

ARTICLE IN PRESS

04

8

12

1620

24

28N

NE

E

SE

S

SW

W

NW

Karol BaughCannught PlaceLajpat Nagar

048

12162024283236

N

NE

E

SE

S

SW

W

NW

ITO CrossingRaja GardenShakarpur Crossing

048

121620242832

N

NE

E

SE

S

SW

W

NW

JanakpuriKalkajiMayur Vihar

048

12162024283236404448

N

NE

E

SE

S

SW

W

NW

JanakpuriOkhla Ph-IMayapuri

048

12162024283236

N

NE

E

SE

S

SW

W

NW

Canught PlaceIITRace Course

Residential

Areas

Commercial

Areas

Industrial Areas

Petrol

Pumps

TrafficIntersections

Fig. 9. Pollution rose for different categories at Delhi.

A. Srivastava et al. / Atmospheric Environment 39 (2005) 59–7170

The pollution rose for petrol pumps sites show carry

over of pollutants from the northwest quadrant,

predominately from north at all the three sites. At

traffic intersections and petrol pumps the carry over of

pollutants from north is also reflective of city activity.

VOCs which can be traced to industrial activity have

also been identified.

In the process of long-range transport, the primary

pollutants such as VOCs and NOx react in atmosphere

to produce secondary pollutants such as ozone and

PAH, etc. with different reaction rates. Highly reactive

species react near the vicinity of the sources, while slow-

reacting species may be transported to large distances.

Toluene has a much shorter lifetime than benzene (Singh

and Zimmermon, 1992). So higher benzene-to-toluene

(B/T) ratio is expected to be found in aged air via a long-

range transport. B/T ratio can be thus used as a tracer to

predict long-range transport. In the present work B/T

ratios at residential (1.43), commercial (1.41), industrial

(1.66), traffic intersection (1.04) and petrol pumps (2.05)

show that beside the local activity concentration of

benzene is high due to long-range transport. The

directional dependence shows that the long-range

transport is from north.

7. Conclusions

The levels of VOCs observed in this study is

appreciably high. Most of the VOCs can be associated

ARTICLE IN PRESSA. Srivastava et al. / Atmospheric Environment 39 (2005) 59–71 71

with mobile sources and diesel internal combustion

engines. This is the first study reporting target VOCs

concentrations in the urban area of Delhi. However, as

per the auto fuel policy of Govt. of India, buses, taxis

and autorickshaws have switched over to CNG as fuel

and benzene content in petrol has been reduced to 1%

(Auto Fuel Policy, Govt. of India, 2001). There is a need

to monitor VOCs again in changed scenario to assess the

effect of actions taken. This work is in progress.

Acknowledgement

The authors are thankful to Dr. Sukumar Devotta,

Director, NEERI, for his encouragement, and the

Central Pollution Control Board for funding this study.

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