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Atmospheric Environment 34 (2000) 2785}2790

Technical note

Atmospheric polycyclic aromatic hydrocarbons in 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 and 24.5 ng m\. Pyrene and benz(a)anthracene#chrysene were abundant at both sites while benzo(b)#uoranthene and benzo(k)#uoranthene were abundant, in addition, at the IIT site. The large amount of pyrene in the ambient samples in Mumbai is likely from cooking-fuel combustion (animal manure, kerosene and lique"ed petroleum gas) in addition to vehicular emissions. Pyrene and chrysene are also emitted from industrial oil burning while the low concentrations of benzo(a)pyrene indicate that wood burning is not a signi"cant source. At the IIT site, primarily vehicular emissions along with cooking fuel emissions are the likely contributors while industrial oil burning is an additional contributor at Saki Naka, accounting for the higher concentrations of pyrene and chrysene/benz(a)anthracene. In urban areas vehicular emissions are likely to be the primary contributor to PAH concentrations with additional local contributors like cooking fuel 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 originally studied in ambient air because of their carcinogenicity and pro-mutagenicity in animal and bacterial assay tests (Finlayson-Pitts and Pitts, 1986). PAH pro"les, or the relative abundance of the di!erent species in particulate emissions from di!erent combustion sources, have been suggested as reliable source signatures where inorganic marker elements are not available. For example, PAH pro"les have been used to identify vehicular emissions following the use of unleaded gasoline in many countries and the loss of lead as a vehicular source marker (Daisey et al., 1986; Miguel and Pereira, 1989; Li and 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 multivariate PAH source apportionment study in Birmingham, UK (Harrison et al., 1996). Sources of PAHs in the urban atmosphere of industrialized countries include automobiles, re-suspended soils, re"neries and power plants (Venkataraman and Friedlander, 1994a; Harrison et al., 1996). In addition, in the Indian urban environment, cooking fuel combustion is a likely source of PAH. High concentrations of PAHs have been measured in smoke from solid-fuel stoves burning wood, coal and dried cattle manure (Raiyani et al., 1993a) which along with kerosene stoves (Saksena et al., 1996) are used as the primary cooking device by urban slum residents. In India, ambient concentrations of particulate benzo(a)pyrene have been measured in Mumbai (formerly Bombay) (Mohan Rao et al., 1983) and Ahmedabad (Aggarwal et al., 1982), with a view to evaluate the carcinogenic risk from PAH exposure. Recent studies of PAH 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

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concentrations in Indian cities are 10}50 times higher than those reported internationally and range 23} 190 ng m\ (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) measure particulate PAH concentrations at ambient locations in Mumbai to assess their concentrations, and (ii) compile PAH pro"les for relevant sources in the Indian urban atmosphere and qualitatively assess contributions from various sources.

2. Experimental methods Mumbai is situated about midway on the western coast of India and is a peninsular city joined to the mainland at its northern end. Large petrochemical plants, fertilizer plants and a power plant are located at the southeastern corner. Several thousand medium- and small-scale industries are located in the city including chemical, textile and dyeing, pharmaceutical, paint and pigment and metal working industries. The land-use pattern is mostly industrial-cum-residential with a total population of over 10 million and a population density of 16,500 km\. Particulate samples were collected from two ambient sites in Mumbai during the winter of 1996}1997, located at Regional Telecommunications Training Center at Saki Naka (SN) and at the Indian Institute of Technology (IIT). The ambient site at Saki Naka was situated on the third story of the building (about 13 m height) and roughly 0.5 km away from a busy roadway intersection, surrounded by slum residences amidst a dense cluster of medium- and small-scale industries. At the Indian Institute of Technology, samplers were situated on the roof of an entry kiosk (about 4 m height and 6 m from the roadway), surrounded by residential areas, along with a few slum residences. A belt of small-scale industries is located about 1}2 km to the east in a north-south stretch (Fig. 1). Samples were collected over 72-h average sampling periods at the two locations using an eight-stage Andersen impactor (Andersen Instruments Inc., USA). The impactor 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 an after-"lter. The impactor was connected to a continuous duty, carbon-vane vacuum pump and a constant air #ow rate of 28.8 lpm was maintained with an in-line rotameter. Low-volume impactor sampling was preferred to minimize volatilization losses of semi-volatile PAH species (Venkataraman et al., 1994b) which occur during hi-volume PM-10 sampling on glass "ber "lters (Coutant et al., 1988). Impactors have near 100% collection e$ciency for compounds of vapor pressures lower than 10\ atm (Zhang and McMurry, 1991) which in-

cludes the PAH species reported here. The Vaseline coating on the collection foil is expected to coat the deposited aerosol and further reduce volatilization losses (Venkataraman et al., 1994b). The PAH concentrations measured on all stages (1}8 and after-"lter) were added to obtain the total PAH concentrations in the particle samples. Sampling periods and average particle concentrations are given in Table 1. The samples were collected on pre-treated aluminum foils, cut to the size of impactor stages and on a glass"ber after-"lter (Whatman, GF/C). Aluminum foils and after-"lters were pretreated by (i) furnace baking for 4 h at 4003C to volatilize any organic contaminants; (ii) washing with dichloromethane; (iii) oven drying for 12 h at 1003C; and (iv) equilibrating at 233C and approximately 50% RH (air conditioned room) for 24 h before weighing on a microbalance (Model BP-210D, Sartorius, Mumbai). Aluminum foil substrates for all eight impactor stages were Vaseline coated by solvent evaporation of a 2% Vaseline in cyclohexane solution to minimize particle bounce (Venkataraman et al., 1994b). The aluminum foils and after-"lters were subjected to ultrasonic extraction and analyzed using high-performance liquid chromatography and UV absorption detection. Extracts were syringe-"ltered through 0.5 lm Millipore PTFE "lters (Millipore(I) Ltd., Mumbai), evaporated to dryness using a stream of dry nitrogen and re-dissolved in 200 ll acetonitrile (Sisco Research Labs., Mumbai). Fluoranthene, pyrene and chrysene and benz(a)anthracene may experience losses during the solvent exchange procedure. To account for these, we subjected the SRM 1647c to the solvent exchange procedure. Losses were found to be less than 10% and we did not make any corrections to the measured concentrations. Re-extraction of a fraction of the samples showed over 95% of the PAH mass recovered by the "rst extraction for two-thirds of the samples, and 85}95% recovery for the remaining one-third, indicating near complete recovery. The HPLC was calibrated using an external standard (SRM 1647c, NIST, USA), diluted to ten times. Repeat injections of samples showed variations of less than 4% for all species. Detection limits ranged 0.4}2 ng for di!erent PAH species. Field blanks were analyzed to ensure that there was no signi"cant background interference. Compound identi"cation was done by retention time matching between standard and sample chromatograms. Individual compound injections were made for #uoranthene, pyrene, chrysene and benzo(a)pyrene to verify the elution order. Abbreviations for the PAH compounds measured at Mumbai and those in the compiled source pro"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),

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

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

4}7 and 13}16 Dec., 1996

IIT

Dates of sampling

Particles (lg m\)

Total PAH (ng m\)

196.8

24.5

19}22 and 27}30 Nov.,1996

Saki Naka Particles (lg m\)

Total PAH (ng m\)

126.6

38.8

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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 was 38.8 ng m\ and that at IIT was 24.5 ng m\ (Fig. 2) with individual PAH species concentrations ranging from 1}13 ng m\. These concentrations are at the lower end of the range of reported PAH concentrations (23}190 ng m\) 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 concentrations show that pyrene and benz(a)anthracene# chrysene are abundant at both sites while benzo(b) #uoranthene and benzo(k)#uoranthene are abundant, in addition, at the IIT sampling site. The di!erent ambient mix of PAH indicates a di!erence in the predominance source classes a!ecting each site. A 1992}1993 air-pollutant emission inventory for Mumbai (Larssen et al., 1997) estimated 1.6;10 g y\ of PM-10 emissions with major contributions from vehicular exhaust plus re-suspension from roads (39%), non-combustion industrial sources (stone crushing, construction, 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-oil burning, domestic/commercial fuel burning would emit particulate PAH as well. The Indian vehicle #eet, which almost entirely uses leaded petrol, consists of four-stroke engine cars and light-duty gasoline vehicles, two-stroke engine scooters and motorcycles and heavy-duty diesel vehicles. The Mumbai vehicle #eet inventory in 1993 counted about 650,000 vehicles with 48% cars and light-duty gasoline vehicles, 39% two-stroke engine vehicles (two- and threewheeler scooters and motorcycles) and 13% heavy-duty diesel 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 of relevance in the Indian urban environment and attempt to explain qualitatively, their relative importance in Mumbai. PAH pro"les are compiled in this section (Table 2) for cooking fuels (Raiyani et al., 1993a) and diesel bus emissions (Ravi Shankar, 1990). The PAH pro"les for urban cooking fuels, including wood, dried cattle manure, coal, kerosene and lique"ed petroleum gas, were measured in an indoor air characterization study in slum houses in Ahmedabad (Raiyani et al., 1993a). These solid-fuel stoves burning along with kerosene stoves (Saksena et al., 1996) are the primary cooking devices used by urban low-income residents. The diesel bus emissions study was conducted by collecting emissions aerosol from tailpipes of idling diesel-powered buses in a bus-depot of the Delhi Transport Corporation in New Delhi (Ravi Shankar, 1990).

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

P. Kulkarni, C. Venkataraman / Atmospheric Environment 34 (2000) 2785}2790 Table 2 Predominant PAH species in locally measured PAH pro"les for cooking fuel and diesel bus emissions Source/Fuel

Predominant PAH species (%)

Cooking stoves Wood Cattle manure Coal Kerosene LPG Diesel buses

BAP (35%), DBA (15%), INP (15%) PYR (18%), BAP (15%), FLT (12%) PYR (21%), DBA (15%), BAP (12%) BAP (22%), PYR (15%), DBA (15%) PYR (27%), BAP (15%), DBA (12%) PHT (60%), CHR (15%), BEP (15%)

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

PAH pro"les were developed from these measurements by normalizing each PAH species concentration to that of the total PAH concentration (all species), present in the particulate emissions (Table 2). Wood burning in cooking stoves shows a predominance of benzo(a)pyrene (35%), in agreement with previous studies (Li and Kamens, 1993). Emissions from dried cattle-manure show a predominance of the low molecular weight species (#uoranthene, pyrene and chrysene), possibly because of the lower combustion temperature than wood, and of benzo(a)pyrene. All three fossil-cooking-fuel emissions show a predominance of pyrene and benzo(a)pyrene, while coal and kerosene show additional predominance of dibenz-anthracene, benzo(ghi)perylene and indeno (123-cd)pyrene. The diesel emissions PAH pro"le showed a large predominance of phenanthrene (60%) along with small amounts of chrysene and benzo(e)pyrene. 3.3. Qualitative assessment of PAH sources in Mumbai From previous studies (Daisey et al., 1986; Miguel and Pereira, 1989; Li and Kamens, 1993; Venkataraman and Friedlander, 1994a; Khalili et al., 1995; Harrison et al., 1996; Rogge et al., 1993a,b), the following PAH have been identi"ed as markers for various sources in urban atmospheres: coal combustion } phenanthrene, #uoranthene and pyrene; coke production } anthracene, phenanthrene and benzo(a)pyrene; incineration } pyrene, phenanthrene and #uoranthene; wood combustion } benzo(a)pyrene and #uoranthene; industrial-oil burning } #uoranthene, pyrene and chrysene; petrol-powered vehicles } benzo(ghi)perylene, indeno (123-cd)pyrene and coronene; diesel powered vehicles } #uoranthene and pyrene with higher ratios of benzo(b)#uoranthene and benzo(k) #uoranthene, plus thiophene compounds. As may be noted from the markers listed above, there is much similarity and overlap between pro"les from di!erent source categories. However, a qualitative source apportionment may be made. The large amounts of pyrene in the ambient sam-

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ples in Mumbai is likely from cooking fuel combustion (a predominant species in the PAH source pro"les for animal manure, kerosene and LPG, described in Table 2) in addition to vehicular emissions. Pyrene and chrysene are also emitted from industrial-oil burning. The low concentrations of benzo(a)pyrene indicate that wood-burning is not a likely signi"cant source. Fluoranthene and pyrene are emitted from both petrol and diesel vehicles with additional indeno (123-cd)pyrene from petrol vehicles and chrysene, benzo(b)#uoranthene and benzo(k) #uoranthene from diesel powered vehicles. The relative abundance of ambient PAH at the IIT site indicates vehicular emissions with some cooking fuel contribution to pyrene and benzo(a)pyrene. This is consistent with the sampling site being 5 m away from the road at 3 m height and surrounded by residential areas. A vehicle count during peak tra$c estimated about 3300 vehicles per hour with 43% two-stroke engine petrol-powered vehicles, 36% 4-stroke petrol-powered vehicles and 21% diesel vehicles. Industrial- oil burning is a likely additional source to PAH ambient concentrations at Saki Naka, accounting for the higher concentrations of pyrene and chrysene/benz(a)anthracene. The Saki Naka site is located amidst a cluster of small-scale industries and near a major roadway intersection with tra$c density of over 5500 vehicles h\ (Vinod Kumar, 1998).

4. Discussion and conclusions In early measurements of urban PAH concentrations in Los Angeles, the strong correlation between the concentrations of coronene, lead and particles indicated that automobiles were the predominant source of PAHs. Sites in 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"nery contributions, while those that were distant and inland were primarily dominated by automobile emissions (Duval and Friedlander, 1980). More recently, using new source pro"les and ambient data, it was shown that meat cooking contributed 20}75% of the semi volatile, 4-ring PAH at a residential site in Upland, while automobiles contributed to concentrations of the 5-ring and larger species (Venkataraman and Friedlander, 1994a). Application of principal component analysis to a set of urban "ne fraction air pollutant and meteorological data from Birmingham, UK (Harrison et al., 1996) identi"ed six components representing the source categories of vehicular/road dust, oil combustion, secondary aerosol, incineration, metallurgical industries, and marine/road salt. The principal component patterns obtained, when PAH compounds were included, corresponded very closely to those derived from solely inorganic aerosol constituent concentrations plus meteorological data.

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Road tra$c was shown to be the major source of PAH in the Birmingham atmosphere. In this work, we measured PAH concentrations at two sites in Mumbai, India, in the winter of 1996. The qualitative source apportionment presented here indicates that automobile emissions are the likely primary contributor to PAH concentrations with additional local contributors like cooking fuel combustion or industrial oil burning. Comprehensive measurements of inorganic and organic aerosol constituents in all seasons and of local source pro"les are needed to make quantitative source apportionment estimates. Acknowledgements We appreciate the assistance of Salimol Thomas (IIT, Bombay) with the chemical analysis. References Aggarwal, A.L., Raiyani, C.V., Patel, P.D., Shah, P.G., Chatterjee, S.K., 1982. Assessment of exposure to benzo(a)pyrene in the air for various population groups in Ahmedabad. Atmospheric Environment 16, 867}870. Coutant, R.W., Brown, L., Chuang, J.C., Riggin, R.M., Lewis, R.G., 1988. Phase distribution and artifact formation in ambient air sampling for polynuclear aromatic hydrocarbons. Atmospheric Environment 22, 403}409. Daisey, J.M., Cheney, J.L., Lioy, P.J., 1986. Pro"les of organic particulate emissions from air pollution sources: status and needs for receptor source apportionment modeling. Journal of the Air Pollution Control Association 36, 17}33. Finlayson-Pitts, B.J., Pitts Jr., J.N., 1986. Atmospheric Chemistry: Fundamentals and Experimental Techniques. WileyInterscience, New York. Golwalkar, V.M., 1993. Auto emission and its relation to ambient pollution in Mumbai. Proceedings of the Seminar on Prevention and Control of Pollution Due to Automobile Tra$c. Institution of Engineers, Mumbai. Harrison, R.M., Smith, D.T.J., Luhana, L., 1996. Source apportionment of atmospheric polycyclic aromatic hydrocarbons collected from an urban location in Birmingham, UK. Environmental Science and Technology 30, 825}832. Kulkarni, P., 1997. Chemical Mass Balance for Source Aportionment of Particulate Polycyclic Aromatic Hydrocarbons in Indian Cities. M.Tech. Thesis, Centre for Environmental Science and Engineering, Indian Institute of Technology, Bombay, 93pp. Khalili, N.R., Sche!, P.A., Holsen, T.M., 1995. PAH source "ngerprints for coke ovens, diesel and gasoline engines, highway tunnels and wood combustion emissions. Atmospheric Environment 29, 533}542. Larssen, S., Gram, F., Hagen, L.O., Jansen, H., Oltshoorn, X., Aundhe, R.V., Joglekar, U., 1997. Greater Mumbai report. In: Shah, J.J., Nagpal, T. (Eds.), URBAIR: Urban Air Quality Management Strategy in Asia. The International Bank of Reconstruction and Development/The World Bank, Washington DC.

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