atmospheric polycyclic aromatic hydrocarbons in mumbai, india

Atmospheric Environment 34 (2000) 2785}2790

Technical note

Atmospheric polycyclic aromatic hydrocarbonsin Mumbai, India

Pramod Kulkarni, Chandra Venkataraman*

Center for Environmental Science and Engineering, Indian Institute of Technology (Bombay), Powai, Mumbai-400 076, India

Received 19 October 1998; accepted 21 June 1999

Abstract

Atmospheric particulate PAH concentrations were measured at two locations in Mumbai (formerly Bombay), India.Total PAH concentrations (seven compounds) at Saki Naka and Indian Institute of Technology (IIT) were 38.8 and24.5 ng m~3. Pyrene and benz(a)anthracene#chrysene were abundant at both sites while benzo(b)#uoranthene andbenzo(k)#uoranthene were abundant, in addition, at the IIT site. The large amount of pyrene in the ambient samples inMumbai is likely from cooking-fuel combustion (animal manure, kerosene and lique"ed petroleum gas) in addition tovehicular emissions. Pyrene and chrysene are also emitted from industrial oil burning while the low concentrations ofbenzo(a)pyrene indicate that wood burning is not a signi"cant source. At the IIT site, primarily vehicular emissions alongwith cooking fuel emissions are the likely contributors while industrial oil burning is an additional contributor at SakiNaka, accounting for the higher concentrations of pyrene and chrysene/benz(a)anthracene. In urban areas vehicularemissions are likely to be the primary contributor to PAH concentrations with additional local contributors like cookingfuel or industrial emissions. ( 2000 Published by Elsevier Science Ltd. All rights reserved.

Keywords: Urban aerosols; PAH; Vehicular emissions; Biomass-burning stoves; Industrial-oil burning

1. Introduction

Polycyclic aromatic hydrocarbons (PAHs) were ori-ginally studied in ambient air because of their carcino-genicity and pro-mutagenicity in animal and bacterialassay tests (Finlayson-Pitts and Pitts, 1986). PAH pro-"les, or the relative abundance of the di!erent species inparticulate emissions from di!erent combustion sources,have been suggested as reliable source signatures whereinorganic marker elements are not available. Forexample, PAH pro"les have been used to identify vehicu-lar emissions following the use of unleaded gasoline inmany countries and the loss of lead as a vehicular sourcemarker (Daisey et al., 1986; Miguel and Pereira, 1989; Liand Kamens, 1993; Venkataraman and Friedlander,1994a). PAH pro"les were recently seen to perform as

*Corresponding author. Fax:#91-22-578-3480.E-mail address: [email protected] (C. Venkataraman)

reliably as inorganic compound pro"les in a multivariatePAH source apportionment study in Birmingham, UK(Harrison et al., 1996).

Sources of PAHs in the urban atmosphere of indus-trialized countries include automobiles, re-suspendedsoils, re"neries and power plants (Venkataraman andFriedlander, 1994a; Harrison et al., 1996). In addition, inthe Indian urban environment, cooking fuel combustionis a likely source of PAH. High concentrations of PAHshave been measured in smoke from solid-fuel stovesburning wood, coal and dried cattle manure (Raiyani etal., 1993a) which along with kerosene stoves (Saksena etal., 1996) are used as the primary cooking device byurban slum residents.

In India, ambient concentrations of particulate ben-zo(a)pyrene have been measured in Mumbai (formerlyBombay) (Mohan Rao et al., 1983) and Ahmedabad(Aggarwal et al., 1982), with a view to evaluate the car-cinogenic risk from PAH exposure. Recent studies ofPAH concentrations in ambient aerosol in Ahmedabad,Mumbai, Nagpur and Kanpur, show that total PAH

1352-2310/00/$ - see front matter ( 2000 Published by Elsevier Science Ltd. All rights reserved.PII: S 1 3 5 2 - 2 3 1 0 ( 9 9 ) 0 0 3 1 2 - X

concentrations in Indian cities are 10}50 times higherthan those reported internationally and range 23}190 ng m~3 (Raiyani et al., 1993b; Pandit et al., 1996;Vaishali et al., 1997; Thakre et al., 1997; Kulkarni,1997).

The objectives of the present study were to (i) measureparticulate PAH concentrations at ambient locations inMumbai to assess their concentrations, and (ii) compilePAH pro"les for relevant sources in the Indian urbanatmosphere and qualitatively assess contributions fromvarious sources.

2. Experimental methods

Mumbai is situated about midway on the westerncoast of India and is a peninsular city joined to themainland at its northern end. Large petrochemicalplants, fertilizer plants and a power plant are located atthe southeastern corner. Several thousand medium- andsmall-scale industries are located in the city includingchemical, textile and dyeing, pharmaceutical, paint andpigment and metal working industries. The land-use pat-tern is mostly industrial-cum-residential with a totalpopulation of over 10 million and a population density of16,500 km~2. Particulate samples were collected fromtwo ambient sites in Mumbai during the winter of1996}1997, located at Regional TelecommunicationsTraining Center at Saki Naka (SN) and at the IndianInstitute of Technology (IIT). The ambient site at SakiNaka was situated on the third story of the building(about 13 m height) and roughly 0.5 km away froma busy roadway intersection, surrounded by slum resi-dences amidst a dense cluster of medium- and small-scaleindustries. At the Indian Institute of Technology, sam-plers were situated on the roof of an entry kiosk (about4 m height and 6 m from the roadway), surrounded byresidential areas, along with a few slum residences. A beltof small-scale industries is located about 1}2 km to theeast in a north-south stretch (Fig. 1).

Samples were collected over 72-h average samplingperiods at the two locations using an eight-stage Ander-sen impactor (Andersen Instruments Inc., USA). Theimpactor has 50% cut-o! aerodynamic diameters of 10,9, 5.8, 4.7, 3.3, 2.1, 1.1, 0.65 lm for stages 1}8, respectively,and collects all particles smaller than 0.43 lm on anafter-"lter. The impactor was connected to a continuousduty, carbon-vane vacuum pump and a constant air #owrate of 28.8 lpm was maintained with an in-linerotameter. Low-volume impactor sampling was prefer-red to minimize volatilization losses of semi-volatilePAH species (Venkataraman et al., 1994b) which occurduring hi-volume PM-10 sampling on glass "ber "lters(Coutant et al., 1988). Impactors have near 100% collec-tion e$ciency for compounds of vapor pressures lowerthan 10~9 atm (Zhang and McMurry, 1991) which in-

cludes the PAH species reported here. The Vaseline coat-ing on the collection foil is expected to coat the depositedaerosol and further reduce volatilization losses (Ven-kataraman et al., 1994b). The PAH concentrations mea-sured on all stages (1}8 and after-"lter) were added toobtain the total PAH concentrations in the particle sam-ples. Sampling periods and average particle concentra-tions are given in Table 1.

The samples were collected on pre-treated aluminumfoils, cut to the size of impactor stages and on a glass-"ber after-"lter (Whatman, GF/C). Aluminum foils andafter-"lters were pretreated by (i) furnace baking for 4 hat 4003C to volatilize any organic contaminants; (ii)washing with dichloromethane; (iii) oven drying for 12 hat 1003C; and (iv) equilibrating at 233C and approxim-ately 50% RH (air conditioned room) for 24 h beforeweighing on a microbalance (Model BP-210D, Sartorius,Mumbai). Aluminum foil substrates for all eight impac-tor stages were Vaseline coated by solvent evaporation ofa 2% Vaseline in cyclohexane solution to minimize par-ticle bounce (Venkataraman et al., 1994b).

The aluminum foils and after-"lters were subjected toultrasonic extraction and analyzed using high-perfor-mance liquid chromatography and UV absorption detec-tion. Extracts were syringe-"ltered through 0.5 lmMillipore PTFE "lters (Millipore(I) Ltd., Mumbai), evap-orated to dryness using a stream of dry nitrogen andre-dissolved in 200 ll acetonitrile (Sisco Research Labs.,Mumbai). Fluoranthene, pyrene and chrysene andbenz(a)anthracene may experience losses during the sol-vent exchange procedure. To account for these, we sub-jected the SRM 1647c to the solvent exchange procedure.Losses were found to be less than 10% and we did notmake any corrections to the measured concentrations.Re-extraction of a fraction of the samples showed over95% of the PAH mass recovered by the "rst extractionfor two-thirds of the samples, and 85}95% recovery forthe remaining one-third, indicating near complete re-covery.

The HPLC was calibrated using an external standard(SRM 1647c, NIST, USA), diluted to ten times. Repeatinjections of samples showed variations of less than 4%for all species. Detection limits ranged 0.4}2 ng for di!er-ent PAH species. Field blanks were analyzed to ensurethat there was no signi"cant background interference.Compound identi"cation was done by retention timematching between standard and sample chromatograms.Individual compound injections were made for #uoran-thene, pyrene, chrysene and benzo(a)pyrene to verify theelution order. Abbreviations for the PAH compoundsmeasured at Mumbai and those in the compiled sourcepro"les are as follows: ACY } acenaphthylene, ACN }acenaphthene, FLR } #uorene, PHT } phenanthrene,ANT } anthracene, PYR } pyrene, FLT } #uoranthene,BAA } benz(a) anthracene, CHR } chrysene, B#C }benz(a)anthracene#chrysene (where they co-elute),

2786 P. Kulkarni, C. Venkataraman / Atmospheric Environment 34 (2000) 2785}2790

Fig. 1. Schematic of Mumbai city showing sampling sites and industrial belts, marked with hatching, which include medium- andsmall-scale industries like chemical, textile and dyeing, pharmaceutical, paint and pigment and metal-working plants.

Table 1Sampling periods and average concentrations of particles (0}10 lm aerodynamic diameter) and associated PAH at ambient sites inMumbai

Dates of sampling IIT Dates of sampling Saki Naka

Particles Total PAH Particles Total PAH(lg m~3) (ng m~3) (lg m~3) (ng m~3)

4}7 and 13}16 196.8 24.5 19}22 and 27}30 126.6 38.8Dec., 1996 Nov.,1996

P. Kulkarni, C. Venkataraman / Atmospheric Environment 34 (2000) 2785}2790 2787

Fig. 2. Ambient PAH concentrations in Saki Naka and IIT in Mumbai. The di!erence in relative abundances of di!erent PAH speciesindicates a di!erence in the sources a!ecting these sites.

BEP } benzo(e)pyrene, BAP } benzo(a)pyrene, BKF }benzo(k) #uoranthene, BBF } benzo(b) #uoranthene,DBA } dibenzanthracene, BGP } benzo(ghi)perylene,INP } indeno(123-cd)pyrene.

3. Results

3.1. Ambient PAH concentrations and sources in Mumbai

The total PAH concentration at Saki Naka was38.8 ng m~3 and that at IIT was 24.5 ng m~3 (Fig. 2)with individual PAH species concentrations rangingfrom 1}13 ng m~3. These concentrations are at the lowerend of the range of reported PAH concentrations(23}190 ng m~3) in Indian cities (Raiyani et al., 1993b;Pandit et al., 1996; Vaishali et al., 1997; Thakre et al.,1997; Kulkarni, 1997). The measured ambient PAH con-centrations show that pyrene and benz(a)anthracene#chrysene are abundant at both sites while benzo(b)#uoranthene and benzo(k)#uoranthene are abundant, inaddition, at the IIT sampling site. The di!erent ambientmix of PAH indicates a di!erence in the predominancesource classes a!ecting each site.

A 1992}1993 air-pollutant emission inventory forMumbai (Larssen et al., 1997) estimated 1.6]1010 g y~1

of PM-10 emissions with major contributions from ve-hicular exhaust plus re-suspension from roads (39%),non-combustion industrial sources (stone crushing, con-struction, refuse-burning) (26%), industrial oil-burning(18%) and domestic/commercial fuel-burning (wood,kerosene, lique"ed petroleum gas) (14%). In addition to

petrol and diesel-powered automobiles and industrial-oilburning, domestic/commercial fuel burning would emitparticulate PAH as well.

The Indian vehicle #eet, which almost entirely usesleaded petrol, consists of four-stroke engine cars andlight-duty gasoline vehicles, two-stroke engine scootersand motorcycles and heavy-duty diesel vehicles. TheMumbai vehicle #eet inventory in 1993 counted about650,000 vehicles with 48% cars and light-duty gasolinevehicles, 39% two-stroke engine vehicles (two- and three-wheeler scooters and motorcycles) and 13% heavy-dutydiesel buses and trucks (Golwalkar, 1993).

3.2. PAH proxles for emission sources in urban India

In this section we compile PAH pro"les for sources ofrelevance in the Indian urban environment and attemptto explain qualitatively, their relative importance inMumbai. PAH pro"les are compiled in this section(Table 2) for cooking fuels (Raiyani et al., 1993a) anddiesel bus emissions (Ravi Shankar, 1990). The PAHpro"les for urban cooking fuels, including wood, driedcattle manure, coal, kerosene and lique"ed petroleumgas, were measured in an indoor air characterizationstudy in slum houses in Ahmedabad (Raiyani et al.,1993a). These solid-fuel stoves burning along with kero-sene stoves (Saksena et al., 1996) are the primary cookingdevices used by urban low-income residents. The dieselbus emissions study was conducted by collecting emis-sions aerosol from tailpipes of idling diesel-poweredbuses in a bus-depot of the Delhi Transport Corporationin New Delhi (Ravi Shankar, 1990).


Table 2Predominant PAH species in locally measured PAH pro"les forcooking fuel and diesel bus emissions

Source/Fuel Predominant PAH species (%)

Cooking stoves!Wood BAP (35%), DBA (15%), INP (15%)Cattle manure PYR (18%), BAP (15%), FLT (12%)Coal PYR (21%), DBA (15%), BAP (12%)Kerosene BAP (22%), PYR (15%), DBA (15%)LPG PYR (27%), BAP (15%), DBA (12%)Diesel buses" PHT (60%), CHR (15%), BEP (15%)

!Compiled from Raiyani et al. (1993a)."Compiled from Ravi Shankar (1990).

PAH pro"les were developed from these measure-ments by normalizing each PAH species concentration tothat of the total PAH concentration (all species), presentin the particulate emissions (Table 2). Wood burning incooking stoves shows a predominance of benzo(a)pyrene(35%), in agreement with previous studies (Li and Ka-mens, 1993). Emissions from dried cattle-manure showa predominance of the low molecular weight species(#uoranthene, pyrene and chrysene), possibly because ofthe lower combustion temperature than wood, and ofbenzo(a)pyrene. All three fossil-cooking-fuel emissionsshow a predominance of pyrene and benzo(a)pyrene,while coal and kerosene show additional predominanceof dibenz-anthracene, benzo(ghi)perylene and indeno(123-cd)pyrene. The diesel emissions PAH pro"le showeda large predominance of phenanthrene (60%) along withsmall amounts of chrysene and benzo(e)pyrene.

3.3. Qualitative assessment of PAH sources in Mumbai

From previous studies (Daisey et al., 1986; Miguel andPereira, 1989; Li and Kamens, 1993; Venkataraman andFriedlander, 1994a; Khalili et al., 1995; Harrison et al.,1996; Rogge et al., 1993a,b), the following PAH have beenidenti"ed as markers for various sources in urban atmo-spheres: coal combustion } phenanthrene, #uorantheneand pyrene; coke production } anthracene, phenanthreneand benzo(a)pyrene; incineration } pyrene, phenanthreneand #uoranthene; wood combustion } benzo(a)pyreneand #uoranthene; industrial-oil burning } #uoranthene,pyrene and chrysene; petrol-powered vehicles } ben-zo(ghi)perylene, indeno (123-cd)pyrene and coronene;diesel powered vehicles } #uoranthene and pyrene withhigher ratios of benzo(b)#uoranthene and benzo(k)#uoranthene, plus thiophene compounds. As may benoted from the markers listed above, there is much sim-ilarity and overlap between pro"les from di!erent sourcecategories.

However, a qualitative source apportionment may bemade. The large amounts of pyrene in the ambient sam-

ples in Mumbai is likely from cooking fuel combustion (apredominant species in the PAH source pro"les for ani-mal manure, kerosene and LPG, described in Table 2) inaddition to vehicular emissions. Pyrene and chrysene arealso emitted from industrial-oil burning. The low concen-trations of benzo(a)pyrene indicate that wood-burning isnot a likely signi"cant source. Fluoranthene and pyreneare emitted from both petrol and diesel vehicles withadditional indeno (123-cd)pyrene from petrol vehiclesand chrysene, benzo(b)#uoranthene and benzo(k)#uoranthene from diesel powered vehicles.

The relative abundance of ambient PAH at the IIT siteindicates vehicular emissions with some cooking fuelcontribution to pyrene and benzo(a)pyrene. This is con-sistent with the sampling site being 5 m away from theroad at 3 m height and surrounded by residential areas.A vehicle count during peak tra$c estimated about3300 vehicles per hour with 43% two-stroke engine pet-rol-powered vehicles, 36% 4-stroke petrol-powered ve-hicles and 21% diesel vehicles. Industrial- oil burning isa likely additional source to PAH ambient concentra-tions at Saki Naka, accounting for the higher concentra-tions of pyrene and chrysene/benz(a)anthracene. TheSaki Naka site is located amidst a cluster of small-scaleindustries and near a major roadway intersection withtra$c density of over 5500 vehicles h~1 (Vinod Kumar,1998).

4. Discussion and conclusions

In early measurements of urban PAH concentrationsin Los Angeles, the strong correlation between the con-centrations of coronene, lead and particles indicated thatautomobiles were the predominant source of PAHs. Sitesin the proximity of re"neries were shown to have 70}95%contributions of PAH concentrations from this source,ones that were somewhat distant had 15}27% re"nerycontributions, while those that were distant and inlandwere primarily dominated by automobile emissions(Duval and Friedlander, 1980). More recently, using newsource pro"les and ambient data, it was shown that meatcooking contributed 20}75% of the semi volatile, 4-ringPAH at a residential site in Upland, while automobilescontributed to concentrations of the 5-ring and largerspecies (Venkataraman and Friedlander, 1994a).

Application of principal component analysis to a set ofurban "ne fraction air pollutant and meteorological datafrom Birmingham, UK (Harrison et al., 1996) identi"edsix components representing the source categories ofvehicular/road dust, oil combustion, secondary aerosol,incineration, metallurgical industries, and marine/roadsalt. The principal component patterns obtained, whenPAH compounds were included, corresponded veryclosely to those derived from solely inorganic aerosolconstituent concentrations plus meteorological data.

P. Kulkarni, C. Venkataraman / Atmospheric Environment 34 (2000) 2785}2790 2789

Road tra$c was shown to be the major source of PAH inthe Birmingham atmosphere.

In this work, we measured PAH concentrations at twosites in Mumbai, India, in the winter of 1996. The quali-tative source apportionment presented here indicatesthat automobile emissions are the likely primary con-tributor to PAH concentrations with additional localcontributors like cooking fuel combustion or industrialoil burning. Comprehensive measurements of inorganicand organic aerosol constituents in all seasons and oflocal source pro"les are needed to make quantitativesource apportionment estimates.

Acknowledgements

We appreciate the assistance of Salimol Thomas (IIT,Bombay) with the chemical analysis.

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