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Establishing Criteria of Relative Abundance ofAlkyl Polycyclic Aromatic Hydrocarbons (PAHs) forDifferentiation of Pyrogenic and Petrogenic PAHs: AnApplication to Indian SedimentMahua Saha a , Hideshige Takada a & Badal Bhattacharya ba Laboratory of Organic Geochemistry (LOG), Tokyo University of Agriculture andTechnology , Fuchu , Tokyo , Japanb Institute of Ecotoxicology and Environmental Sciences , Kolkata , IndiaPublished online: 04 Dec 2012.

To cite this article: Mahua Saha , Hideshige Takada & Badal Bhattacharya (2012) Establishing Criteria of Relative Abundanceof Alkyl Polycyclic Aromatic Hydrocarbons (PAHs) for Differentiation of Pyrogenic and Petrogenic PAHs: An Application toIndian Sediment, Environmental Forensics, 13:4, 312-331, DOI: 10.1080/15275922.2012.729005

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Environmental Forensics, 13:312–331, 2012Copyright C© Taylor & Francis Group, LLCISSN: 1527-5922 print / 1527-5930 onlineDOI: 10.1080/15275922.2012.729005

Establishing Criteria of Relative Abundance of Alkyl PolycyclicAromatic Hydrocarbons (PAHs) for Differentiation of Pyrogenicand Petrogenic PAHs: An Application to Indian Sediment

Mahua Saha,1 Hideshige Takada,1 and Badal Bhattacharya2

1Laboratory of Organic Geochemistry (LOG), Tokyo University of Agriculture and Technology, Fuchu, Tokyo, Japan2Institute of Ecotoxicology and Environmental Sciences, Kolkata, India

Various source materials such as crude oil, automobile exhaust, coal, and wood combustion products were analyzed for polycyclicaromatic hydrocarbons (PAHs) and hopanes. Hopanes were detected in coal combustion-derived soot, along with petrogenic sources.Based on the correlation between the alkylated PAHs/parental PAHs ratio with their respective C30 hopane/PAHs ratio in these sourcematerials, the criteria for differentiating the petrogenic and pyrogenic sources of PAHs were established. This study concluded thatsediments contained exclusively pyrogenic PAHs when the following conditions were met: MP/P (methylphenanthrenes to phenan-threne) = 0.5, MPy/Py [(methylpyrenes + methylfluoranthenes) to (pyrene + fluoranthene)] = 0.15, and MC/C [(methylchrysenes +methylbenz[a]anthracenes) to (chrysene + benz[a]anthracene)] = 0.2. By contrast, the sediments contained exclusively petro-genic PAHs when the ratios of MP/P, MPy/Py, MC/C, and methyl PAHs (MPAHs)/PAHs exceeded 3.5, 1.5, 2.0, and 2.2, respec-tively. Based on these criteria, an intensive source apportionment of PAHs to sediments from three Indian metro cities, Chennai(n = 6), Mumbai (n = 6) and Kolkata (n = 12) (2003–2007), was determined. This investigation found that sedimentary PAHs fromIndia were depleted in alkylated PAHs with low MP/P ≈ 0.7, MPy/Py ≈ 0.14, and MC/C ≈ 0.3, which contrasted with other tropicalAsian countries, where elevated values of these ratios were detected. Among the three cities, Kolkata waters were more stronglyinfluenced by pyrogenic sources of PAHs with very low alkylated PAHs ratios than Chennai and Mumbai sediments. The compositionaldifferences were attributed to the dominant coal and biomass in Kolkata compared to the dominant usage of petrogenic cooking fuel(e.g., kerosene) and automobile-derived sources in Chennai and Mumbai.

Keywords: alkyl polycyclic aromatic hydrocarbons (PAHs), threshold value, pyrogenic, petrogenic, hopanes, sedimentary PAH, sourceidentification, geochemical indicator

Introduction

Polycyclic aromatic hydrocarbons (PAHs) consist of two or morefused aromatic rings and constitute an important class of ubiq-uitous persistent organic micro pollutants (Blumer, 1976). Theanthropogenic sources of PAHs are mainly classified into twotypes: petrogenic and pyrogenic. Crude oil and petroleum prod-ucts such as kerosene, gasoline, diesel fuel, lubrication oil, andasphalt are the petrogenic sources. Pyrogenic sources are formedby the incomplete combustion of organic matter (e.g., coal,petroleum, wood). PAHs are also derived from some naturalsources such as oil seeps, grass fires, forest fires, volcanoes,ancient sediment erosion, and early diagenesis. Because of thetoxic, mutagenic and carcinogenic properties of PAHs and theirmetabolic products (epoxides), they are listed as priority pollu-tants by national and international environmental agencies (e.g.,European Economic Area European Union, United States En-vironmental Agency) and thus the identification of the sourcesof PAHs is requisite for its regulation in waters.

Address correspondence to Hideshige Takada, Laboratory of Or-ganic Geochemistry (LOG), Tokyo University of Agriculture and Tech-nology, Fuchu, Tokyo 183-8509, Japan. E-mail: shige@cc.tuat.ac.jp

Previous investigations used the relative abundance of alky-lated PAHs to their respective parental PAHs to identify thesource of sedimentary PAHs (Saha et al., 2009). Compared withparental PAHs, the alkylated PAHs are thermodynamically un-stable, which leads to the lower abundance of alkylated PAHs atthe higher temperature of their generation (Blumer, 1976; Gar-rigues et al., 1995). To distinguish the petrogenic and pyrogenicsources of PAHs, the alkyl PAHs to parental PAHs ratios in threehomologue series, i.e., phenanthrene series, fluoranthene-pyreneseries and chrysene-benz[a]anthracene series were used togetherfor the first time in our previous work. Many molecular ratios inPAH homologous series have been considered as environmentalweathering ratios but here we are mainly emphasizing on the ra-tios of alkyl PAHs to parent PAHs from three homologous series,since individual homologues often can reflect different sourcesbecause of their differences in homologous compositions amongsources (Figure 1). The three ratios of alkylated PAHs totheir respective parental PAHs: methylphenanthrenes to phenan-threne (MP/P), methylpyrenes + methylfluoranthenes to pyrene+ fluoranthene (MPy/Py) and methylchrysenes + methyl-benz[a]anthracenes to chrysene + benz[a]anthracene (MC/C)and all alkyl PAHs to respective parental PAHs (MPAHs/PAHs)

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Figure 1. Structure of target alkylated polycyclic aromatic hydrocarbons (PAHs).

were examined based on the analysis of various source materi-als (crude oil, automobile exhaust, and coal combustion-derivedsoot from cooking and brick yards and wood-combustion-derived soot). The individual alkyl PAHs ratios are important todetermine more precise sources of PAHs. Especially, the lowermolecular weight PAHs can be more affected by environmen-tal weathering (e.g., microbial degradation) (Ambrosoli et al.,2005; Nieman et al., 2001), which may change the MP/P ra-tio whereas higher molecular weight PAHs are less affectedby degradation which makes the other two ratios MPy/Py andMC/C less prone to change by environmental weathering. There-fore, four alkyl PAHs ratios were examined in the present study.In the previous study (Saha et al. 2009), the number of sourcematerials was limited. Hence in the present paper, the extendedexploration of source materials leads to the reestablishment ofour earlier evaluated criteria on alkylated PAHs.

It is also possible to combine PAH fingerprinting with otherforensic methods (Pies et al., 2008). To characterize PAH con-taining samples, previous studies have used forensic methods in-cluding biomarkers such as isoalkanes and isoprenoids, steranesand terpanes (Kaplan et al., 2001; Murphy and Brown, 2005;Wang and Fingas, 2003). To understand the behavioral patternof petrogenic sources of PAH the unique petroleum biomarkerhopane was successfully used in the earlier research (Boonyatu-manond et al., 2006; Saha et al., 2009; Zakaria et al., 2000; 2001;2002). Hopanes, a group of triterpane hydrocarbons, are pro-duced through diagenesis during petroleum formation in mainlyancient sediments and are ubiquitously present in crude oil (Fig-ure 2). They consist of a range of C27 to C35, homologues withvarious stereoisomers (Peters et al., 2005) (Figure 2). Homo-hopanes contain more than thirty carbon atoms. Norhopanes(C29 hopanes) are hopanes that have lost a methyl group. The

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Figure 2. Chemical structures of pentacyclic triterpanes (hopanes).

petroleum formation process converts the biological 17β, 21β

configuration to the αβ configuration. Similarly, the 22R con-figuration can be eventually converted to an equilibrium mixtureof 22S and 22R diastereoisomers, as found in crude oils. Thusthe hopane compositions of specific crude oils vary, dependingon their original biomass (e.g., the sources of organic matterand the depositional environment) and the maturity of the oil(Volkman et al., 1997; Luellen and Shea, 2003). The distinctsignature of the petroleum biomarker often provides a chemicalfingerprint to identify source oils and allocate source contribu-tions towards the aquatic environment (Volkman et al., 1997).The hopane compositional pattern is used in the present studyto help confirm the presence of petrogenic PAHs.

So far, in most of the industrialized countries, such asthe United States, Europe and Australia, pyrogenic PAHswere found to be the predominant source of PAHs in aquaticsediments (Budzinski et al., 1997; Hites et al., 1980; McCreadyet al., 2000; Notar et al., 2001; Pereira et al., 1999; Stout

et al., 2004; Woodhead et al., 1999; Zeng and Vista, 1997).Pyrogenic sources also predominated in the East China Sea(Guo et al., 2006). Both petrogenic and pyrogenic sourceswere comparable in the coastal sediment of the Pearl River,China (Bixian et al., 2001). However, information on thesources of PAHs in tropical Asian countries is limited in spiteof the rapid progress and expansion of industrialization andurbanization in these regions. Recently, Zakaria et al. (2002)and Boonyatumanond et al. (2006; 2007) demonstrated thewidespread input of petrogenic PAHs to Malaysian waters anda mixture of pyrogenic and petrogenic sources of PAHs in thesediment of Thailand, respectively.

In our previous study (Saha et al., 2009) the preliminarysource identification of sedimentary PAHs from various tropi-cal Asian countries (Laos, Malaysia, Cambodia, the Philippines,Thailand, Indonesia, Vietnam, Japan, and India) was reported.The results depicted a dominance of pyrogenic sources in In-dian sediment, contrastive with other tropical Asian countries,

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where PAHs were generated mainly from petrogenic sources.Sediments from only one metro city, Kolkata, were analyzedfor PAHs as Indian sediment samples. The specific differencein the source of PAHs between India and other tropical Asiancountries required a more detailed analysis of PAHs in the In-dian sediments. However, analytical data from only one placein a vast country such as India can be misleading in identifyingthe source of PAHs in this country, since the energy usage andthe other responsible factors on PAHs input such as population,vehicular population, and sewage treatment procedure may di-verge among the different locations. To date, no fundamentaldata on aquatic pollution in terms of PAHs are available in In-dia. A few studies have been reported on the distribution andspecific source identification of PAHs (Agarwal et al., 2006;Agarwal et al., 2009; Ahmad et al., 1996; Malik et al., 2004).Hence to obtain a comprehensive picture of the source of PAHsthroughout India, in the present study sediment samples fromtwo other metropolitan cities Chennai and Mumbai were alsoincorporated along with those of Kolkata.

Materials and Method

Study Area and Sample Collection

Surface sediment samples were collected from the canals ofKolkata, Chennai, and Mumbai using the Ekman dredge (top0–5cm). The samples were stored at −30◦ C and freeze-dried be-fore analysis. Two types of source materials were also collected,i.e., petrogenic and pyrogenic materials were sampled. The pet-rogenic source sample included crude oil (n = 5). The pyrogenic

source samples included cooking soot from coal combustion(n = 8), wood combustion (n = 4), and brick production indus-tries (n = 6). Automobile exhaust soot from gasoline-poweredcars (n = 2) and diesel-powered cars (n = 6) was used as amixture of pyrogenic and petrogenic source material since inautomobile exhaust the pyrogenic black soot was mixed withnon-combusted fuel and engine oil. The crude oil samples wereobtained from a worldwide collection of samples held by theJapanese Coast Guard. The soot samples from coal and woodcombustion, brick industries, and automobiles were collectedfrom Kolkata. The detailed collection procedure was describedin our previous study (Saha et al., 2009).

Regional Site Description

From 2003 to 2007, 24 surface sediment samples were collectedfrom canals and rivers in three major metro cities of India, Chen-nai (n = 6), Mumbai (n = 6), and Kolkata (n = 12), located in thesouthern, western, and eastern part of India, respectively. Thesethree cities were selected for our studies because Chennai, Mum-bai, and Kolkata, the three most populated and economically im-portant cities of India are located near the coast of two main seas:the Bay of Bengal and Arabian Sea surrounding the East andWest Indian peninsula. The map of the sampling location anddetailed description of sites are specified in Figure 3 and Table 1.

Chennai Study Area

In Chennai, of a total of six sediment samples, each setof two sediment samples was collected from three urban

Table 1. Information about sediment samples collected from India

Coordinate

North latitude East longitude

City Stations Date of sampling Degree Minute Second Degree Minute Second Description of the locations

Kolkata CC.1 Nov. 07, 2003 22 31 32.3 88 20 29.6 South Canal in KolkataCC.2 Nov. 07, 2003 22 30 26.0 88 20 27.7 South Canal in KolkataCC.3 Nov. 07, 2003 22 34 31.8 88 22 39.9 North Canal in KolkataCC.4 Nov. 07, 2003 22 33 47.0 88 23 30.1 North Canal in KolkataKKNC2 May. 29, 2006 22 35 1.8 88 28 24.8 North Canal in KolkataKKNC3 May. 29, 2006 22 36 10.9 88 25 0.1 North Canal in KolkataKKNC4 May. 29, 2006 22 35 21.7 88 22 48.4 North Canal in KolkataKKNC5 May. 29, 2006 22 33 48.5 88 24 56.1 North Canal in KolkataKKSC1 May. 30, 2006 22 32 21.0 88 20 1.8 South Canal in KolkataKKSC2 May. 30, 2006 22 31 1.2 88 20 24.8 South Canal in KolkataKKSC3 May. 30, 2006 22 29 57.7 88 23 46.4 South Canal in KolkataKKSC4 May. 30, 2006 22 32 7.2 88 23 48.5 South Canal in Kolkata

Chennai INCH-3 Dec. 08, 2007 13 1 32.6 80 14 37.8 Adyar river, ChennaiINCH-4 Dec. 08, 2007 13 1 28.1 80 15 30.2 Bakingham canal, ChennaiINCH-6 Dec. 08, 2007 13 2 21.8 80 16 10.8 Bakingham canal, ChennaiINCH-9 Dec. 09, 2007 13 0 47.0 80 15 32.6 Adyar river, ChennaiINCH-11 Dec. 09, 2007 13 3 49.4 80 15 38.4 Kuam river, ChennaiINCH-13 Dec. 09, 2007 13 4 20.5 80 16 31.2 Kuam river, Chennai

Mumbai INMB-7 Dec. 10, 2007 19 8 16.6 72 49 54.1 city sewage canal, MumbaiINMB-8 Dec. 11, 2007 19 14 13.1 72 49 18.2 Manori creek, MumbaiINMB-1 Dec. 11, 2007 19 14 23.8 72 49 23.8 Manori creek, MumbaiINMB-3 Dec. 11, 2007 19 9 50.2 72 49 2.4 Malad creek, MumbaiINMB-9 Dec. 11, 2007 19 9 15.3 72 48 36.7 Malad creek, MumbaiINMB-11 Dec. 12, 2007 19 2 59.9 72 52 25.1 Mahim creek, Mumbai

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Figure 3. Map of the sampling locations in canals: (a) Chennai, (b) Mumbai, and (c) Kolkata. (color figure available online.)

canals—Adyar River, Cooum River, and Buckingham canal in2007 (Figure 3a). These three canals are the three most pol-luted water bodies in Chennai and the main source of coastalpollution (Shanmugam et al., 2007; Gowri and Ramachandran,2001; Bunch and Dudycha, 2004). The wastewaters from allthe various industries and residential zones, situated along theChennai coastal zone, are finally directed to the coastal stretchof the Bay of Bengal through the Adyar and Cooum outlets turn-ing their estuaries into two of the most highly vulnerable wa-ter zones (Gowri and Ramachandran, 2001; Shanmugam et al.,2007).

The 42.5 km long and 0.5–0.75 m deep Adyar River dis-charges approximately 190–940 million m3 water annually intothe Bay of Bengal. A total of 58 drain outlets discharge intoAdyar and approximately 0.775 million L/day of industrial ef-fluents and 8.1 million L/day of domestic sewage are allowedto flow into the Adyar River (Gowri and Ramachandran, 2001).The present capacity of the river is 39,000 m3/s whereas the an-ticipated flood discharge capacity is approximately 60,000 m3/s

(Gowri et al., 2008). The river is almost stagnant except duringthe rainy season. The sedimentation is not severe in this river.The width of approximately 480 m enables a tidal effect into thewaterway for approximately 4 km. The annual temperature rangein the river is 18◦C–42◦C (Rajkumar et al., 2008). Sedimentsin this region have high organic loadings ∼3%–9% by weight(Purvaja and Ramesh, 2001). This river transports 53.89–454.11tons/day of suspended solids, 0.06–19.64 tons/day of ammonia,15.95–123.24 tons/day nitrate, and 0.4–17.86 tons/day of phos-phate (Gowri et al., 2008).

Another urban river, the Cooum (65 km long), running paral-lel to the Adyar River, carries raw sewage and sullage water fromapproximately 158 sewage/storm water outlets. Approximately80 million L/day of domestic sewage and 0.4 million L/dayof industrial effluents have been allowed to flow into this river(Gowri et al., 2008). The capacity of the river is 19,500 m3/s,and the anticipated flood discharge is around 22,000 m3/s. Or-ganic (faecal) sludge has built up along the bottom of the riverto depths of 0.7 m and more and along the banks to an average of

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0.4 m (Mott MacDonald Ltd., 1994). As the mouth of the riveris not too wide, the impact of the high tide bringing sea wateris approximately 3 km in the river. The water temperature isapproximately the same as the Adyar River as mentioned previ-ously. The river transports 11.87–120.06 tons/day of suspendedsolids, 0.08–58.7 tons/day of ammonia, 6.11–29.25 tons/daynitrate and 0.66–10.73 tons /day of phosphate (Gowri et al.,2008).

A high concentration of nutrients, low dissolved oxygen,high biochemical demand, chemical oxygen demand and chloro-phylla (Chl a) were observed in both the Adyar and CooumRivers (Shanmugam et al., 2007). Compared with the Adyarand Cooum Rivers, Buckingham canal is narrow and used as ajoining canal between and the Adyar and Cooum Rivers. Thepollution level of this canal is almost the same as the other tworivers.

Mumbai Study Area

In Mumbai six canal sediments in total were collected in 2007;among them two sediment samples were taken from the Maladcreek (northwest of Mumbai), two from Manori creek (northernMumbai), one from Mahim creek (in the boundary between thecity and suburbs) and one sample was collected from a sewagecanal in the downtown city (Figure 3b). These creeks are threeof the major drainage basins in the Mumbai metropolis, trans-porting a bulk load of city sewage towards the west and mergewith the Arabian Sea (EnviroVision, 2002; Kumar et al., 2000).The water temperature of all of these three water bodies rangedfrom 26◦C–34◦C. Malad creek is 5 km long and covers an areaof 1.6 sq km. The turbidity of this creek ranges from 59–130NTU (at low tide) to 11–26 NTU (at high tide) (Sardar et al.,2010). Dissolved oxygen (DO) and Biochemical Oxygen De-mand (BOD) were found to be zero and 15–27 mg/L during lowtide and 2.5–3.0 mg/L and 3–7 mg/L during high tide, respec-tively. Among nutrients, ammoniacal nitrogen and phosphatewere found in the range of 1.2–3.9 mg/l and 0.16–0.56 mg/Lduring low tide and 0.4–2.5 mg/L and 0.04–0.16 mg/L dur-ing high tide, respectively. The 4.6 m deep Mahim creek isalso grossly polluted. The DO, BOD and NH3-N were foundto be 0.7–6.1 mg/L, 6.24–34.56 mg/l and 0.53–3.97 mg/l dur-ing high tide whereas these parameter values at low tide are0.45–5.45 mg/L, 7.0–35.71 mg/L and 0.9–7.82 mg/L, respec-tively (Dhage et al., 2006). In another creek (Manori), perco-lation of pollutants from neighboring dumping grounds remainthe prime cause of low amounts of DO (average 1.6 ml/l) andhigher BOD (2.43 mg/l) (Kulkarni et al., 2010). The averagewater temperature is 27.2◦C and average nitrate and phosphateconcentrations are 6.53 μ mol/L and 23.06 μ mol/L, respectively(Kulkarni et al., 2010).

Kolkata Study Area

In Kolkata, of 12 canal sediment samples, four samples weretaken from two canals in Kolkata in 2003. The other eight sam-

ples were taken in 2006, of which four samples were collectedfrom the North canal and four from the South canal (Tolly’s nul-lah) of Kolkata (Table 1, Figure 3c). Tolly’s nullah is 27.4 kmlong. The water quality parameters of individual canals are notavailable.

Analytical Procedure

The descriptive information of the extraction and purificationprocedures of surface sediment samples was described previ-ously (Boonyatumanond et al., 2006; Saha et al., 2009; Zakariaet al., 2001). In brief, freeze-dried sediment samples were ex-tracted in a ASE 200 (Dionex, US) accelerated solvent extractorwith a mixture of dichloromethane (DCM) and acetone (3:1,v/v). The extracts and solutions were spiked with deuteratedPAHs (anthracene-d10, p-terphenyl-d14, benz[a]anthracene-d12)as surrogates and purified by two-step silica gel columnchromatography. The first step silica gel (5% water deacti-vated) column chromatography was performed for elimina-tion of polar components from alkane and PAH fractions. Thealkane+hopane and PAHs were fractionated in a fully activatedsilica gel column in the next step. The alkane + hopane frac-tion and PAH fraction were analyzed by a gas chromatographequipped with a quadrupole mass-selective detector (GC-MS;HP5890, HP5972 [Agilent, Germany]) as described (Boonya-tumanond et al., 2006).

In the present study, 14 parental PAH species and 12 methy-lated PAH species were quantified. The parental PAHs and theirabbreviation in brackets are: phenanthrene (Phe), anthracene(Anth), fluoranthene (Fluo), pyrene (Pyr), benz[a]anthracene(BaA), chrysene (Chry), benzo[b]fluoranthene (BbF), benzo[j]fluoranthene + benzo[k]fluoranthene (BFs), benzo[e]pyrene(BaP), benzo[a]pyrene (BeP), indeno[1,2,3-cd]pyrene (IndPy),benzo[ghi]perylene (BghiP), and coronene (Cor). On GC-MS,they were monitored at m/z = 178 (phenanthrene, anthracene),m/z = 202 (fluoranthene, pyrene), m/z = 228 (benz[a]anthracene, chrysene), m/z = 252 (benzo[b]fluoranthene,benzo[j]fluoranthene, benzo[k]fluoranthene, benzo[e]pyrene,benzo[a]pyrene, perylene), m/z = 276 (indeno[1,2,3-cd]pyrene,benzo[ghi]perylene), and m/z = 300 (coronene). The massfragment gram for the parental PAH species was shown inSaha et al., 2009. Their identification was based on mass spec-trum, comparison of the retention time with corresponding au-thentic standard and/or retention indices listed in (Lee et al.,1979).

Four isomers of methylphenanthrenes were monitored atm/z = 192, which were identified as 3-methylphenanthrene(3-MP), 2-methylphenanthrene (2-MP), 9-methylphenanthrene(9-MP), and 1-methylphenanthrene (1-MP) in the order ofelution. The identification was based on the comparison of re-tention time with an authentic standard (1-MP) and of retentionindices listed in (Lee et al., 1979) and (Takada et al., 1990).Because anthracene is a minor component and its alkylatedhomologues are not positively identified in environmental

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Table 2. PAHs and hopanes in Crude oil, Automobile soot, soot from Brick yards and Cooking soot

∑25

∑13 PAHs∗ Pyr/Fluo Fluo/ Phe/Anth Anth/ BaA/

∑C30/

Type of Sample PAHs (μg/ MPy/ MPAHs/ (Anth+ (BaA+ IP/(IP+ Hopanes hopane/samples ID (μg/g-dry) g-dry) MP/P Py MC/C PAHs (Fluo+Pyr) Phe) Chry) BghiP) H/L (μg/g-dry)

∑13 PAHs

Crude oil Umm Shail 783 167 4.34 2.41 2.74 3.98 1.07 0.48 ND 0.00 0.00 0.11 0.24 899 0.86Mar ban 388 91 3.88 2.82 2.90 3.66 1.76 0.36 ND 0.00 0.05 0.01 0.26 333 0.59Labuan 3195 975 2.43 0.84 2.53 2.35 0.90 0.53 72.6 0.01 0.23 0.27 0.07 760 0.17Miri 551 200 2.45 1.49 2.14 2.24 1.65 0.38 3.60 0.22 0.32 0.25 0.21 1540 1.83Tapis 1040 271 3.17 1.31 2.95 3.04 0.73 0.58 32.5 0.03 0.13 0.00 0.18 626 0.53

Automobile soot(Diesel car)

AS2 149 123 0.42 0.19 0.05 0.27 1.69 0.37 15.3 0.06 0.30 0.39 0.38 14 0.01AS3 83 61 0.78 0.34 0.20 0.46 1.90 0.35 9.96 0.09 0.29 0.30 0.47 19 0.04AS12 200 124 2.89 0.53 0.34 0.77 3.65 0.22 4.64 0.18 0.17 0.32 0.62 97 0.09AS4 1339 1122 1.12 0.22 0.19 0.31 1.62 0.38 5.32 0.16 0.41 0.43 1.11 385 0.04AS6 766 682 1.05 0.13 0.10 0.20 1.40 0.42 3.98 0.20 0.25 0.51 1.43 97 0.02AS13 248 176 1.51 0.16 0.26 0.46 1.27 0.44 6.80 0.13 0.24 0.39 0.18 320 0.24

Automobile soot(Gasoline car)

AS8 301 151 3.38 1.41 1.77 2.05 2.94 0.25 5.43 0.16 0.28 0.10 1.67 1191 0.95AS9 661 533 1.45 0.26 0.71 0.51 2.46 0.29 4.74 0.17 0.38 0.18 1.46 2113 0.45

Cooking soot (coal) S2 42 40 0.20 0.07 0.12 0.14 0.88 0.53 4.53 0.18 0.53 0.43 3.37 0.51 0.00S5 83 77 0.31 0.48 1.01 0.83 1.44 0.41 6.88 0.13 0.33 0.26 33.50 0.27 0.00S6 619 572 0.43 0.25 0.19 0.23 1.42 0.41 3.57 0.22 0.34 0.49 4.05 0.65 0.00S7 1733 1630 0.36 0.21 0.37 0.31 1.24 0.45 3.99 0.20 0.44 0.45 7.82 1.25 0.00S1 30 27 0.46 0.15 0.35 0.29 1.14 0.47 4.52 0.18 0.43 0.37 3.05 1.52 0.01S3 51 42 1.09 0.33 0.62 0.56 1.29 0.44 4.98 0.17 0.39 0.34 3.05 1.82 0.01S4 426 371 1.09 0.74 1.43 1.26 1.37 0.42 6.45 0.13 0.29 0.23 25.64 2.63 0.00S10 1260 1004 1.83 0.28 0.38 0.44 1.22 0.45 3.20 0.24 0.46 0.45 1.88 4.05 0.00

Brick Manufact.Soot

Ut 100 96 0.06 0.02 0.09 0.05 0.51 0.66 21.4 0.04 0.35 0.43 0.52 0.07 0.00Kn 79 77 0.03 0.01 0.07 0.03 0.27 0.78 120 0.01 0.22 0.44 0.75 0.05 0.00Hm 97 95 0.03 0.01 0.06 0.03 0.23 0.82 66.1 0.01 0.18 0.50 0.52 0.07 0.00BS2 864 738 1.18 0.31 0.30 0.35 0.62 0.62 5.30 0.16 0.34 0.38 3.77 64.9 0.01BS4 360 319 0.41 0.13 0.31 0.26 0.54 0.65 21.3 0.04 0.34 0.53 3.13 11.2 0.00BS7 620 558 0.43 0.19 0.38 0.33 0.52 0.66 7.61 0.12 0.32 0.43 6.85 21.9 0.01

Cooking soot(Wood)

WS1 529 514 0.16 0.07 0.10 0.11 0.82 0.55 4.65 0.18 0.48 0.47 4.11 0.10 0.00WS2 1656 1621 0.07 0.05 0.06 0.05 1.06 0.49 3.30 0.23 0.52 0.48 2.00 0.05 0.00WS5 83 80 0.12 0.03 0.07 0.07 0.70 0.59 11.07 0.08 0.36 0.54 1.37 0.12 0.00WS8 736 702 0.14 0.06 0.07 0.09 0.80 0.56 4.54 0.18 0.48 0.51 1.21 0.07 0.00

Note: ∗∑13 PAHs is summation of 13 parent PAHs excluding peryene and coronene,∑

26 PAHs is summation of 13 parent PAHs and 12 methylated PAHs.

samples (Takada et al., 1990), methylanthracenes were not usedfor the source discrimination in the present study. Four peaksof methylpyrenes (MPy) and/or methylfluoranthenes wereobserved at m/z = 216 and five peaks of methylchrysenes (MC)and/or methylbenz[a]anthracenes were monitored at m/z =242. The details of peak identification were given in a previousreport (Saha et al., 2009).

Individual PAHs were quantified by comparing the integratedpeak area of the selected ion with the peak area of the internalinjection standard (IISTD). Acenaphthene-d8 and chrysene-d12

were used as the IISTD for the quantification of PAHs rang-ing from phenanthrene to 1-methylphenanthrene and for PAHsfrom fluoranthene to coronene, respectively. Corrections forrelative response at the corresponding mass/charge ratio weremade by analyzing a PAH standard (Phe, Anth, 1-MP, Fluo, Pyr,1-MPy, Chry, 1-MC, 5-MC, BbF, BeP, BaP, perylene, BghiP,Cor) under the same instrumental conditions such as the sam-ple analyses. As no benz[a]anthracene standard was available,an estimated response factor for benz[a]anthracene was basedon a response for chrysene. Similarly, benzo[j]fluoranthene +benzo[k]fluoranthene and indeno[1,2,3-cd]pyrene concentra-tions were based on the benzo[b]fluoranthene and benzo[ghi]perylene response, respectively. Also all the methylphenan-threnes, methylpyrenes and methylfluoranthenes, methylchry-senes and methylbenz[a]anthracenes were based on the

1-methylphenanthrene, 1-methylpyrene, and average of 1-methylchrysene and 5-methylchrysene, respectively. PAHs con-centrations were recovery-corrected using the spiked surrogates.Results were recovery-corrected with the recoveries of the sur-rogates (>80% throughout the analyses). We tested the repro-ducibility of the analyses by four replicate analyses of sediment;reproducibility ranged from 2.3% to 14.6% of the relative stan-dard deviation. Procedural blanks were run with every batch,and analytical values five times higher than the blank were con-sidered significant.

The sum of concentrations of 14 parental PAH species rang-ing from phenanthrene to coronene, excluding perylene, isexpressed as total parental PAHs or

∑14PAHs. The sum of

concentrations of all 26 PAH species except perylene is ex-pressed as

∑26PAHs. Because we measured four methylated

phenanthrenes in addition to the 14 parental PAHs in previousstudies (Zakaria et al., 2002), the sum of the 18 PAH speciesis expressed as

∑18PAHs to facilitate comparison. The ratio

of the sum of 3-methylphenanthrene, 2-methylphenanthrene,9-methylphenanthrene, and 1-methylphenanthrene to phenan-threne is expressed as MP/P. The ratio of the sum of three peaksof methylpyrenes/methylfluoranthenes to the sum of pyrene andfluoranthene is expressed as MPy/Py. The ratio of the sum offive peaks of methylchrysenes/methylbenz[a]anthracenes to thesum of chrysene and benz[a]anthracene is expressed as MC/C.

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Criteria of Relative Abundance of Alkyl PAHs 319

In addition, the ratio of the sum of all the methyl PAH speciesto the sum of phenanthrene, fluoranthene, pyrene, chrysene, andbenz[a]anthracene is defined as MPAHs/PAHs.

Individual hopanes were identified by comparing their re-tention times with those for the standards and their massspectra, which were obtained on a different GC-MS runon Scan mode, or in the literature. Triterpanes, includinghopanes, were monitored at a mass/charge ratio (m/z) of 191in selected ion monitoring mode. 17α(H)-22,29,30-trisnorhopane (Tm), 17α(H),21α(H)-norhopane (C2917α); 17β(H),21α

(H)-norhopane (C2917β); 17α(H),21β(H)-hopane (C3017α);17β(H),21α(H)-hopane (C3017β); 18α(H)-oleanane, 18β(H)-oleanane, and 17α(H),21β(H)-homohopane (C3117α) wereused as analytical standards. Individual hopanes were quanti-fied by comparing the integrated peak area of the selected ionwith the peak area of IISTD (17β,21(H)β - hopane). The re-sponse factor of 18α(H)-22,29,30-trisnorneohopane (Ts) wasassumed to be the same as Tm, 18α(H), 21β(H)-30-norhopane(C2918α) as C2917β, and homohopanes ranging from carbonnumber C31-C35 as C3117α.

Result and Discussions

Reestablishment of Criteria for Source IdentificationBased on PAHs and hopanes

Measurement of PAHs in potential source materialsThe total PAHs (

∑13PAHs, excluding perylene and

coronene, since in some crude oil samples, coronene could notbe detected) and alkyl PAHs concentration among the sourcematerials are shown in Table 2. Two types of crude oil hadthe highest values of MP/P (2.43–4.34), MPy/Py (0.84–2.82),MC/C (2.14–2.95) and MPAHs/PAHs (2.24–3.98), followedby soot collected from automobiles, having the second high-est value of MP/P (0.42–3.38), MPy/Py (0.13–1.41), MC/C(0.05–1.77) and MPAHs/PAHs (0.2–2.05). The lowest valuesof MP/P (0.07–0.16), MPy/Py (0.03–0.07), MC/C (0.06–0.10)and MPAHs/PAHs (0.05–0.11) were found in wood combustedsoot.

The soot samples taken from coal combustion for cookingdepict a range of low (27 μg/g dry wt) to high (1,630 μg/g drywt) concentrations of PAHs (Table 2). This wide range of PAHscan be explained in terms of geological maturity of coal. Theother factors such as temperature, oxygen concentration, mois-ture content and presence of other combustible materials canbe ignored because the soot samples were collected in the sameseason of uniform oxygen concentration and moisture content ofthe air. The temperature during combustion was also maintainedat almost the same level in all the cooking processes and no othercombustible materials were used during the cooking. So the totalPAHs in coal combustion derived cooking soot may have variedlargely due to the usage of different types of coal of differentmaturity, which is a scale of coal rank. During the geologicalcoalification processes, plant remains undergo a sequence ofphysical, biochemical, and chemical changes (diagenesis, thencatagenesis), which result in a series of coals with increasing

ranks of maturity. Low rank pure coals (i.e., lignite and browncoal) have less aromaticity and lower concentration of PAHsthan higher rank coals (i.e., bituminous, sub-bituminous and an-thracites) (Stout and Emsbo-Mattingly, 2008). After combustionalso, the higher rank coal produced higher PAHs concentrationin its derived product (e.g., coal smoke) in comparison to lowerrank coal (Oros and Simoneit, 2000) although PAH compositioncould be modified during combustion.

The ratio of individual alkylated PAHs/parental PAHs forcoal combustion-derived cooking soot has an overall lower valuethan that of automobile soot, with a range of MP/P = 0.2–1.83,MPy/Py = 0.07–0.74, MC/C = 0.12–1.43, and MPAHs/PAHs =0.14–1.26 (Table 1). Most of the coal soot samples have lowMP/P, MPy/Py, MC/C and MPAHs/PAHs ratio with a medianvalue of 0.44 (MP/P), 0.26 (MPy/Py), 0.37 (MC/C) and 0.37(MPAHs/PAHs), which demonstrate that this soot is basicallypyrogenic in nature, except for a few samples from cook-ing soot (S3, S4 and S10), which has a higher abundanceof alkyl PAHs. This noticeable difference in alkyl PAHs ra-tios also possibly suggests the usage of coal of different typesand nature in cooking. However, it was reported that compara-tively higher matured and highly volatile coal (e.g., bituminous)shows a higher abundance of alkyl PAHs (Oros and Simoneit,2000; Stout and Emsbo-Mattingly, 2008). Furthermore, as men-tioned above, in the higher combustion temperature (>300◦C),the abundance of alkyl side chains in PAHs decreases (Orosand Simoneit, 2000). Hence, comparatively lower matured coal(e.g., lignite) and a higher combustion temperature are the rea-sons behind the lower abundance of alkyl PAHs (Oros and Si-moneit, 2000; Simoneit et al., 2005) in most of the coal sootsamples.

Identification of hopane isomers in source materialsHopanes are generally found in petrogenic source samples.

They were also detected in low but traceable concentrations incoal combustion-derived soot. Total hopane concentration incoal combustion-derived soot during cooking and brick manu-facturing was 0.27-–4.05 μg/g dry wt and 0.05–64.9 μg/g drywt, respectively (Table 2). In a previous study (Saha et al., 2009),three brick soot samples (Ut, Kn and Hm) showed a very lowconcentration of hopane (0.05–0.07 μg/g dry wt), whereas theother three samples (BS2, BS4, and BS7) in the present studyexhibited comparatively high hopane concentrations in the rangeof 11.21–64.9 μg/g dry wt. This difference in hopane concentra-tion among the brick soot samples can also be explained in termsof maturity of the coal, which was possibly the chief contributorof hopane in both combustion processes, since the combustiontemperature, oxygen concentration, moisture content and com-bustion materials are almost the same at all brick manufacturingsites from where the samples were collected. Similar to thisstudy, petroleum biomarker hopanes in various types of coal ofdifferent maturity were used as biomarkers of coal as well as in aprevious work (Oros and Simoneit, 2000; Simoneit et al., 2007).The stereo chemical configurations at the C17 and C21 positionsof hopanes can be used to determine the maturity of a geological

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320 M. Saha et al.

sample, where hopanes with configurations of 17β(H),21β(H)(ββ) are immature, 17β(H),21α(H) (βα; C2917β and C3017β)are moderately mature and 17α(H),21β(H) (αβ: C2917α andC3017α) are fully mature (Oros and Simoneit, 2000). The chro-matogram of brick manufacturing soot has good similarity withthat of fully matured coal (bituminous coal in Oros and Simoneit,2000) where the dominance of C2917α over C3017α and relativelower abundance of β homologues (C29 17β and C30 17β) thanα homologues (C2917α and C3017α) were found (Figure 4). Thissimilarity affirms the possibility of the usage of a large amountof matured coal during the making of brick samples, which maybe the cause of the higher hopane concentration.

A definite demarcation between coal combustion relatedhopane and auto exhaust related hopanes can be shown by theirhopane profile with respect to the abundance of β homologuesand C31S (22S-17α(H),21β(H)-homohopane) and C31R (22R-17α(H),21β(H)-homohopane) (Figure 5). The β isomers werefound with higher abundance in coal combustion-derived sootthan in automobile-derived soot, which was also supported byearlier research by Oros and Simoneit (2000), where the β iso-mers of hopane were also found to be significant in coal. Inaddition, the lower value of the C31S/C31R ratio was found inless coal combustion-derived soot (e.g., S1, BS2 and BS7) thanin automobile soot (Table 3). Thus, the higher abundance of β

isomers together with the lower C31S/C31R ratio in the hopaneprofile of brick soot strengthens the fact that the hopane gener-

Sele

cted

Ion

Cur

rent

(m/Z

=191

)

Ts

Tm

C2917α

C2917β

C3017α

C3017β

C31S

C31R

C32SC32R

C33SC33R

C34SC34R

C35SC35R

IIS Brick manufacturing soot

Retention time (min)

(a)

Ts

Tm

C2917α

C2917

C3017α

C3017β

C31SC31R C32S C32R

C33SC33R

IIS

Coal combustion soot

Retention time (min)

(b)

β

Figure 4. Gas chromatogram for hopane in: (a) coal combustion soot inbrick manufacturing, and (b) coal combustion soot in cooking.

ated in the soot from brick manufacturing is mostly from coalinstead of any petrogenic source.

Correlation Between Alkyl Homologues Ratio and HopaneIndex: Differentiation of Pyrogenic and Petrogenic PAHs

To formulate the correlation between PAHs and hopanes, the ra-tio of C3017α to total parental PAHs (

∑13PAHs) for individual

source materials was calculated (Table 2), which is expressedas C30 hopane/PAHs. This ratio was found highest in crudeoil (0.165–1.831) followed by automobile soot (0.015–0.238).The C30 hopane/PAHs value is very low in coal combustion-derived cooking soot (0.0001–0.0057). In brick soot samplesC30 hopane/PAHs values vary from very low (0.0001) to mod-erately high (0.0126). The lowest value of this ratio was observedin wood combustion-derived soot samples (0–0.0001), which isalmost insignificant. The C30 hopane/PAHs ratio in the pyro-genic source material samples was consistently less than 0.013(Figure 6).

The correlation between the C30 hopane/PAHs ratio withthe alkyl homologous ratio: MP/P, MPy/Py, MC/C andMPAHs/PAHs is shown in Figure 7 (a, b, c and d, respec-tively). A positive correlation was observed between the C30

hopane/PAHs ratio and other alkyl PAHs/PAHs ratios. The C30

hopane/PAHs ratio approaches zero in samples with MP/P ra-tios < 0.5 (Figure 7a). This finding suggests that MP/P ratios< 0.5 are completely pyrogenic. Similarly, threshold ratios forMPy/Py, MC/C and MPAHs/PAHs ratio < 0.15, 0.2, and 0.3 cor-respond to C30 hopane/PAHs ratios approaching zero (Figure 4b,c, and d). Almost all of the petrogenic source materials, crudeoil, and automobile soot (except AS2) lie above these thresholdratios (Table 2). Although the automobile soot results from com-bustion, the petrogenic signature is likely due to the presenceof crankcase oil and uncombusted fuel. Some of the petrogenicsource materials and some of the coal combustion-derived soot(cooking soot and brick manufacturing soot) depicted mixedsignals among the MP/P, MPy/Py, MC/C and MPAHs/PAHsratios. For example, cooking soot such as:

� S3 (MP/P = 1.09, MPy/Py = 0.33, MC/C = 0.62 and MPAHs/PAHs = 0.56),

� S4 (MP/P = 1.09, MPy/Py = 0.74, MC/C = 1.43 and MPAHs/PAHs = 1.26), and

� S10 (MP/P = 1.83, MPy/Py = 0.28, MC/C = 0.38 andMPAHs/PAHs = 0.44),

and brick manufacturing soot such as:� BS2 (MP/P = 1.18, MPy/Py = 0.31, MC/C = 0.30 and

MPAHs/PAHs = 0.35), and� BS7 (MP/P = 0.43, MPy/Py = 0.19, MC/C = 0.38 and

MPAHs/PAHs = 0.33).

have higher alkyl homologue ratios with low C30 hopane/PAHsratios (Figure 7a–d; Table 3). Although these C30 hopane/PAHsratios are more elevated than the rest of the coal combustion-derived cooking soot and brick manufacturing soot samples,

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Criteria of Relative Abundance of Alkyl PAHs 321

Figure 5. Graph of the hopane profile in automobile and coal combustion related source materials.

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322 M. Saha et al.

Table 3. Total hopane and hopane indexes for potential source materials.

Total∑

13PAHs∗Type of Sample C30Hopane Hopanes (μg/g-

∑hopane/ C29/

∑C31-C35/ C31S/ Homohopane C30hopane/

samples code (μg/g-dry) (μg/g-dry) dry)∑

PAHs C30 C30 C31R index Tm/Ts∑

13PAHs

Crude oil Umm Shaif 143 899 167 5.38 1.56 2.30 1.32 11.2 0.76 0.86Marban 54.0 333 91.3 3.65 1.41 1.86 1.36 9.20 0.35 0.59Labuan 161 760 975 0.78 0.98 0.48 1.43 0.00 2.20 0.17Miri 366 1540 200 7.71 0.85 0.41 1.24 1.50 1.49 1.83Tapis 145 626 271 2.31 1.16 0.89 1.03 2.00 1.43 0.53

Automobile soot AS2 1.84 14.0 123 0.23 1.45 4.16 1.23 5.82 1.45 0.01(Diesel car) AS3 2.31 19.1 61.0 0.02 1.47 4.80 1.21 9.15 1.56 0.04

AS12 10.9 97.0 124 0.78 1.51 5.36 1.21 13.6 1.52 0.09AS4 46.3 385 1122 0.34 1.48 4.76 1.19 10.7 1.35 0.04AS6 11.6 96.9 682 0.14 1.63 4.64 1.24 10.0 1.88 0.02AS13 41.9 320 176 1.82 1.64 3.93 1.26 7.86 1.06 0.24

Automobile soot AS8 144 1191 151 7.90 1.49 4.69 1.17 12.2 1.39 0.95(Gasoline car) AS9 240 2113 533 3.96 1.76 4.89 1.20 10.2 1.52 0.45

Cooking soot S-2 0.00 0.51 40.1 0.01 1.44 2.11 1.00 1.96 1.00 0.00(coal) S-5 0.04 0.27 76.9 0.00 0.94 3.41 1.17 0.01 1.44 0.00

S6 0.08 0.65 572 0.00 1.38 3.49 1.26 0.02 2.10 0.00S-7 0.23 1.25 1630 0.00 0.93 2.25 1.25 4.85 7.34 0.00S1 0.16 1.52 27.3 0.06 1.56 3.68 0.93 0.04 3.82 0.01S3 0.22 1.82 41.5 0.04 1.38 4.16 1.30 5.25 1.02 0.01S4 0.52 2.63 371 0.01 0.87 1.68 1.32 0.02 3.89 0.00S10 0.67 4.05 1004 0.00 1.27 1.80 1.21 4.95 2.30 0.00

Brick Manufact. Ut 0.01 0.07 95.9 0.00 1.94 2.03 1.20 0.06 2.50 0.00Soot Kn 0.00 0.05 77.2 0.00 2.17 4.64 1.20 4.23 1.25 0.00

Hm 0.01 0.07 94.9 0.00 2.27 2.45 1.11 0.00 1.29 0.00BS2 9.33 64.9 738 0.09 1.55 1.60 0.80 4.11 32.4 0.01BS4 1.55 11.2 319 0.04 1.75 2.26 1.13 4.00 39.0 0.00BS7 3.10 21.9 558 0.04 1.48 1.99 0.83 5.15 31.5 0.01

Cooking soot WS1 0.00 0.10 514 0.00 1.94 5.43 1.26 0.45 1.58 0.00(Wood) WS2 0.00 0.05 1621 0.00 1.07 1.50 0.69 2.70 0.73 0.00

WS5 0.01 0.12 80.0 0.00 1.87 4.43 1.09 14.0 0.72 0.00WS8 0.00 0.07 702 0.00 2.22 4.82 1.33 0.27 0.43 0.00

Note: ∗∑13 PAHs is summation of 13 parent PAHs excluding peryene and coronene.

these are much lower than that of petrogenic samples, which in-dicated that these are mainly pyrogenic in nature. Neverthelessthe higher value of alkyl homologue ratios for these pyrogenicsource samples can be explained by the increase of the alkylside chain with the higher maturity of the coal combusted, asexplained in the previous section. In contrast, wood combustionsoot has a very low MP/P, MPy/Py, MC/C, and MPAHs/ PAHsratio as well as insignificant C30 hopane/PAHs ratios. This differ-ence in the alkylated PAHs ratios distinguishes wood (biomassburning) and coal (fossil fuel burning).

Overall, based on the threshold value for MP/P, MPy/Py,MC/C, and MPAHs/PAHs from the individual plot of these ra-tios versus the C30 hopane/PAHs ratio (Figure 7a–d), the criteriafor recognizing an exclusively pyrogenic signature for PAHswere confirmed. The threshold values are different than in ourprevious study. For MP/P, MPy/Py, MC/C and MPAHs/PAHs,it is 0.5, 0.15, 0.2, and 0.3, respectively. Below this value, thesource of PAHs is exclusively pyrogenic. The terminal values forthese four ratios, above which the source of PAHs is exclusivelypetrogenic, are: MP/P = 3.5, MPy/Py = 1.5, MC/C = 2.0 andMPAHs/PAHs = 2.2 (Table 2 and Figure 7a–d). Samples withPAHs from both pyrogenic and petrogenic sources exhibit inter-

mediate PAH ratios (i.e., MP/P>0.5 and <3.5, MPy/Py>0.15and <1.5, MC/C>0.2 and <2.0 and MPAHs/PAHs>0.3 and<2.2).

When the alkyl PAH ratios and their criteria are applied to theenvironmental samples, the effect of environmental alteration(e.g., microbial degradation) on the ratios should be considered.The lower molecular PAHs such as naphthalene, phenanthreneare reported to be oxidized in the aerobic condition (Ambrosoliet al., 2005; Yuan et al., 2000; Nieman et al., 2001), whereasthe alkyl PAHs are less susceptible to microbial degradationbecause of the presence of substitution in aromatic rings (Seoet al., 2009). Hence under the aerobic condition, the MP/P ratiocan increase due to degradation, whereas alkyl PAHs ratios ofhigher molecular weight PAHs (i.e., MPy/Py and MC/C) are lessvulnerable towards degradation, and hence remain unaffected.Therefore, to understand and characterize the source of PAHs,evaluation of all three ratios is necessary.

PAHs Measured in Indian Canal Sediments

The total parental PAHs (∑

14PAHs) concentration in the sedi-ment sample from Chennai, Mumbai and Kolkata ranged from

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Criteria of Relative Abundance of Alkyl PAHs 323

0.0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1.0 1.1 1.2 1.3 1.4 1.5 1.6 1.7 1.8 1.9 2.0

C30 hopane/PAHs

Crude oil

Coal cooking soot

Wood cooking soot

Coal brick soot

Gasoline car soot

Diesel car soot

C30 hopane/PAHs

0.000 0.002 0.004 0.006 0.008 0.010 0.012 0.014

Coal cooking soot

Wood cooking soot

Coal brick soot

Figure 6. Graph of the ratios of C30 hopane to total parent polycyclic aromatic hydrocarbons (PAHs) in source materials. (color figure available online.)

1.11–7.70 μg/g dry, 0.35–4.70 μg/g dry and 1.59–38.10 μg/gdry, respectively (Table 4). Among the three cities, the averagetotal PAHs concentration was found highest (15.91 μg/g dry) inthe surface sediment of Kolkata followed by Chennai (3.62 μg/gdry) and Mumbai (2.09 μg/g dry) (Figure 8).

Application of criteria for detailed PAHs source identificationin sediments

In our previous report (Saha et al., 2009) the MP/P, MPy/Py,MC/C and MPAHs/PAHs ratios in sediments from other tropicalAsian urban waters were found to be much higher than the es-tablished criteria ranging from MP/P ≈ 1–4, MPy/Py ≈ 0.3–1,and MC/C ≈ 0.2–1.0. The very high range of MP/P, MPy/Pyand MC/C for Malaysia and Indonesia suggests a ubiquitousinput of petrogenic PAHs and for the Philippines and Cambo-dian sediment mainly petrogenic PAHs were found (Saha et al.,2009).

In contrast, Indian urban sediment (MP/P: 0.26–2.05,MPy/Py 0.07–0.32, MC/C 0.09–0.64 and MPAHs/PAHs 0.16–0.62) (Table 4) has distinctively portrayed significant contri-bution of pyrogenic sources of PAHs in comparison to othertropical Asian countries, which were subjugated by petrogenicsource of PAHs.

Environmental alteration might contribute to this dramaticdifference in the alkyl PAH ratios between India and the otherAsian countries. However, the minimal effect of environmentalweathering can be expected, since the environmental conditionsof sampling locations in all tropical Asian countries were almostsimilar. Especially, anaerobic conditions in bottom sediments ofall the Asian urban waters depress microbial degradation. Actu-ally no depletion of lower molecular weight PAHs was observedin sediments from the tropical Asian countries. If environmentalweathering occurs, the lower molecular weight PAHs degradedfaster than higher molecular weight. The depletion of lowermolecular weight PAHs is normally associated with an increasein the MP/P ratio. However, no depletion of lower molecularweight PAHs was observed in the tropical Asian countries andno difference in the higher molecular weight PAHs to lowermolecular weight PAHs (H/L) ratios was observed between In-dia and the other tropical Asian countries (Saha et al., 2009).All these findings concluded that the source identification wasnot affected by environmental weathering.

In the present study, in conducting a more detailed studyin India, it was noticed that among the three cities, Kolkatasediment is strongly pyrogenic in nature with respect to theMPAHs/PAHs ratio (MPAHs/PAHs < 0.3), whereas Chennaiand Mumbai sediment appeared to be mostly pyrogenic PAHs

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324 M. Saha et al.

0.0

0.2

0.4

0.6

0.8

1.0

1.2

1.4

1.6

1.8

2.0

0.0 0.5 1.0 1.5 2.0 2.5 3.0 3.5 4.0 4.5 5.0

C30

ho

pan

e/P

AH

s

Crude oilDiesel car sootGasoline car sootCoal soot (cooking)Coal soot (brick)Wood soot (cooking)

0.0

0.2

0.4

0.6

0.8

1.0

1.2

1.4

1.6

1.8

2.0

0.0 0.2 0.4 0.6 0.8 1.0 1.2 1.4 1.6 1.8 2.0 2.2 2.4 2.6 2.8 3.0

C3

0 h

op

an

e/P

AH

s

Crude oilDiesel car sootGasoline car sootCoal soot (cooking)Coal soot (brick)Wood soot (cooking)

0.0

0.2

0.4

0.6

0.8

1.0

1.2

1.4

1.6

1.8

2.0

0.0 0.2 0.4 0.6 0.8 1.0 1.2 1.4 1.6 1.8 2.0 2.2 2.4 2.6 2.8 3.0 3.2

C30

hop

ane/

PA

Hs

Crude oilDiesel car sootGasoline car sootCoal soot (cooking)Coal soot (brick)Wood soot (cooking)

0.0

0.2

0.4

0.6

0.8

1.0

1.2

1.4

1.6

1.8

2.0

0.0 0.2 0.4 0.6 0.8 1.0 1.2 1.4 1.6 1.8 2.0 2.2 2.4 2.6 2.8 3.0 3.2 3.4 3.6 3.8 4.0 4.2

C30

ho

pan

e/P

AH

s

Crude oilDiesel car sootGasoline car sootCoal soot (cooking)Coal soot (Brick)Wood soot (cooking)

MP/P

MC/C MPAHs/PAHs

MPy/Py

(a) (b)

(c) (d)

Figure 7. Graph of the correlation of: (a) methylphenanthrenes to phenanthrene (MP/P), (b) methylpyrenes + methylfluoranthenes to pyrene +fluoranthene (MPy/Py), (c) methylchrysenes + methylbenz[a]anthracenes to chrysene + benz[a]anthracene (MC/C), and (d) methyl polycyclic aromatichydrocarbons (MPAHs)/PAHs with C30 hopane/PAHs in five types of source materials: crude oil, automobile soot, coal cooking soot, brick manufacturingsoot, and wood cooking soot. (color figure available online.)

with a small proportion of petrogenic PAHs (MPAHs/PAHs >

0.3) (Table 4 and Figure 9a). To identify a more distinctivesource of PAHs among the three major cities of Kolkata, Chen-nai and Mumbai, the relative abundance of three methylatedPAHs: MP/P, MPy/Py and MC/C was compared among thesethree cities. Figure 9b demonstrates that the MP/P ratio forKolkata sediment is lower (0.26–1.08) than that of the sedimentin Chennai and Mumbai, ranging from 0.53–1.61 and 0.6–2.05,respectively (Table 4). The average lower value of MP/P (aver-age: 0.46 and median: 0.35) for the Kolkata sediment shows that,with respect to the phenanthrene series, Kolkata canal sedimentis profoundly influenced by the pyrogenic source of PAHs sincealmost all the locations have MP/P<0.5. By contrast, the sedi-ments from Chennai (average: MP/P = 0.92 and median: 0.9)and Mumbai (average: MP/P = 1.30 and median: 1.22), exhib-ited comparatively greater petrogenic input in the sedimentaryphenanthrene (MP/P>0.5).

The MPy/Py ratios in Chennai, Mumbai and Kolkata rangedfrom 0.11–0.14 (median: 0.13), 0.13–0.25 (median: 0.19) and0.07–0.32 (median: 0.09), respectively (Table 4 and Figure 9c).The MPy/Py value in most of the locations from Kolkata andall locations in Chennai lies below the threshold value of 0.15,which signifies that the sediments from these two cities areexclusively pyrogenic with respect to the pyrene-fluorantheneseries. The Chennai sediments show a missed petrogenicphenanthrene signature and pyrogenic pyrene-fluoranthene sig-nature. This divergence indicates that the contributions ofpetrogenic and pyrogenic sources are uneven among the ho-mologues of PAHs, which likely reflects the relative abun-dance in the sources. Normally the phenanthrene series hada greater petrogenic contribution compared to other homolo-gous series possibly due to the presence of fossil fuel or itshigher propensity to degrade in the environment. The sedi-ment in Mumbai has higher MPy/Py (average: MPy/Py = 0.19)

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Tabl

e4.

PAH

san

dho

pane

sin

sedi

men

tofI

ndia

nm

etro

citi

es,C

henn

ai,M

umba

iand

Kol

kata

Ant

h/B

aA/

IP/

∑26

PAH

s∑

18PA

Hs

∑14

PAH

s∗M

PAH

s/P

yr/

Flu

o/P

he/

(Ant

h+

(BaA

+(I

P+

∑H

opan

eC

30ho

p/S

tati

ons

(μg/

g-dr

y)(μ

g/g-

dry)

(μg/

g-dr

y)M

P/P

MP

y/P

yM

C/C

PAH

sF

luo

(Flu

o+P

yr)

Ant

hP

he)

Chr

y)B

ghiP

)H

/L(μ

g/g-

dry)

∑PA

Hs

Che

nnai

INC

H3

3.07

2.68

2.58

0.83

0.12

0.29

0.33

0.81

0.55

3.91

0.20

0.47

0.52

0.74

2.94

0.16

INC

H4

9.59

8.51

7.70

0.53

0.12

0.41

0.34

0.64

0.61

6.24

0.14

0.45

0.43

0.42

13.7

0.25

INC

H6

3.45

2.95

2.62

0.97

0.14

0.47

0.46

0.72

0.58

5.17

0.16

0.49

0.43

0.47

4.93

0.25

INC

H9

3.08

2.69

2.56

1.03

0.14

0.33

0.35

0.77

0.57

3.13

0.24

0.44

0.38

0.71

6.83

0.37

INC

H11

1.27

1.12

1.11

0.57

0.11

0.21

0.26

0.82

0.55

5.46

0.15

0.46

0.52

0.98

1.37

0.17

INC

H13

6.59

5.84

5.14

1.61

0.13

0.40

0.41

0.75

0.57

2.43

0.29

0.52

0.44

0.32

18.4

0.46

AV

G4.

513.

963.

620.

920.

130.

350.

360.

750.

574.

390.

200.

470.

450.

618.

030.

28S

TD

EV

3.03

2.70

2.39

0.39

0.01

0.09

0.07

0.07

0.02

1.47

0.06

0.03

0.06

0.25

6.64

0.12

Med

ian

3.26

2.82

2.60

0.90

0.13

0.37

0.35

0.76

0.57

4.54

0.18

0.47

0.43

0.59

5.88

0.25

Mum

bai

INM

B1

0.49

0.42

0.35

2.05

0.18

0.40

0.62

0.85

0.54

2.95

0.25

0.43

0.51

0.70

1.54

0.62

INM

B3

1.05

0.85

0.83

1.14

0.25

0.64

0.49

0.93

0.52

2.44

0.29

0.46

0.46

0.88

4.67

0.83

INM

B7

5.90

5.13

4.60

1.04

0.15

0.41

0.44

0.87

0.53

4.90

0.17

0.45

0.55

0.55

13.0

0.37

INM

B8

0.45

0.38

0.35

1.31

0.20

0.43

0.50

0.94

0.52

3.30

0.23

0.45

0.58

0.98

0.74

0.32

INM

B9

1.99

1.69

1.73

0.60

0.13

0.24

0.27

0.88

0.53

4.98

0.17

0.46

0.55

1.22

0.90

0.07

INM

B11

6.45

5.22

4.70

1.70

0.23

0.51

0.62

0.92

0.52

4.58

0.18

0.47

0.46

0.90

13.2

0.38

AV

G2.

722.

282.

091.

300.

190.

440.

490.

900.

533.

860.

220.

450.

520.

875.

670.

43S

TD

EV

2.74

2.29

2.04

0.51

0.05

0.13

0.13

0.04

0.01

1.10

0.05

0.02

0.05

0.23

5.91

0.26

Med

ian

1.52

1.27

1.28

1.22

0.19

0.42

0.49

0.90

0.53

3.94

0.21

0.46

0.53

0.89

3.10

0.37

Kol

kata

CC

.l8.

127.

277.

060.

480.

120.

240.

280.

740.

585.

140.

160.

430.

460.

894.

530.

08C

C.2

22.7

20.9

20.2

0.29

0.09

0.19

0.20

0.73

0.58

7.41

0.12

0.41

0.45

0.58

6.44

0.04

CC

.330

.626

.623

.91.

080.

170.

320.

480.

790.

565.

260.

160.

410.

450.

7314

.30.

08C

C.4

11.5

9.47

9.28

0.98

0.32

0.36

0.48

1.07

0.48

3.29

0.23

0.43

0.46

1.28

10.1

0.14

KK

NC

22.

902.

642.

480.

410.

090.

180.

250.

530.

659.

420.

100.

400.

500.

512.

620.

11K

KN

C3

17.6

15.8

15.5

50.

350.

100.

220.

220.

700.

596.

220.

140.

400.

520.

7013

.10.

09K

KN

C4

29.5

27.0

26.6

0.32

0.09

0.16

0.19

0.71

0.58

5.87

0.15

0.41

0.52

0.75

12.8

0.05

KK

NC

53.

092.

782.

760.

350.

090.

180.

200.

740.

576.

670.

130.

400.

510.

691.

950.

08K

KS

C1

1.79

1.62

1.59

0.39

0.11

0.19

0.22

0.70

0.59

6.74

0.13

0.35

0.31

0.90

0.96

0.07

KK

SC

219

.817

.917

.70.

320.

070.

210.

190.

720.

587.

100.

120.

390.

370.

728.

750.

06K

KS

C3

28.9

26.6

25.7

0.27

0.07

0.18

0.18

0.66

0.60

6.53

0.13

0.42

0.50

0.39

9.73

0.04

KK

SC

442

.938

.338

.10.

260.

100.

250.

200.

690.

593.

340.

230.

440.

470.

5912

.10.

04A

VG

18.3

16.4

15.9

0.46

0.12

0.22

0.26

0.73

0.58

6.08

0.15

0.41

0.46

0.73

8.11

0.07

ST

DE

V13

.211

.911

.60.

280.

070.

060.

110.

120.

041.

700.

040.

020.

060.

234.

690.

03M

edia

n18

.67

16.8

516

.64

0.35

0.09

0.20

0.21

0.72

0.58

6.38

0.14

0.41

0.47

0.71

9.24

0.07

Not

e:∗∑

14PA

Hs

issu

mm

atio

nof

14pa

rent

PAH

sex

clud

ing

pery

lene

,∑

18PA

Hs

issu

mm

atio

nof

14pa

rent

PAH

san

d4m

ethy

leph

enan

thre

ne,∑

26PA

Hs

issu

mm

atio

nof

14pa

rent

PAH

san

d12

met

hyla

ted

PAH

s.

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326 M. Saha et al.

0 10000 20000 30000 40000 50000

Total parent PAHs (ng/g-dry)

Kolkata

Mumbai

Chennai

Figure 8. Graph of the concentration of total polycyclic aromatic hydro-carbons (PAHs) in canal sediments from Indian metro cities, Chennai,Mumbai, and Kolkata. (color figure available online.)

indicating that PAHs may come from pyrogenic and petrogenicsources.

Based on the chrysene series, all the locations of Chennai(MC/C: 0.21–0.47) and Mumbai (MC/C: 0.24–0.64) and somelocations in Kolkata (MC/C: 0.16–0.36) show a petrogenic sig-nature of PAHs (Table 4 and Figure 9d), since most of thesamples are higher than the threshold value of MC/C (>0.2).Figure 9b–d shows that Kolkata sediment has more pyrogenicsources of PAHs, even with respect to MPy/Py and MC/C as wellas the MP/P ratio. This finding again signifies that the effect of

environmental weathering is not so prominent since weather-ing such as microbial degradation would be greater in lowermolecular weight PAHs (e.g., phenanthrene). This degradationcan affect the MP/P ratio, whereas MPy/Py and MC/C ratios areless affected by degradation. If weathering were predominantlythe trend in the MP/P ratio, the MPy/Py and MC/C ratio wouldhave been different for the same city. Since the environmentalcondition is similar in the three cities, the effect of potentialweathering is negligible.

Regarding the difference in the source of PAHs among thethree selected cities, Chennai and Mumbai sediments have lesspyrogenic source-oriented PAHs and more petrogenic PAHscompared with Kolkata. This finding might be due to vari-ation in the combined contribution of petrogenic sources ofPAHs derived from cooking fuel and/or automobile exhaustamong these three cities. In between Kolkata and the othertwo cities, the types of fuels used for cooking are different.The fuel used for cooking in different states of India canbe categorized into two types: dirty fuel, containing mainlyfirewood, cow dung cake and coal/lignite/charcoal, and cleanfuel, which contains kerosene, electricity, and bio gas (Liq-uid Petrolium Gas). The two important states of India, Maha-rashtra, and Taminadu, having Mumbai and Chennai as capitalcities, have a larger share of clean fuel (mainly kerosene) con-sumption for middle to upper expenditure groups of people

Figure 9. Graph of the ratios of methylated polycyclic aromatic hydrocarbons (PAHs) to parent PAHs, (a) methyl PAHs (MPAHs)/PAHs (b) methylphenan-threnes to phenanthrene (MP/P), (c) methylpyrenes + methylfluoranthenes to pyrene + fluoranthene (MPy/Py) and (d) methylchrysenes + methyl-benz[a]anthracenes to chrysene + benz[a]anthracene (MC/C), in canal sediments of three Indian metro cities, Chennai, Mumbai, and Kolkata. (colorfigure available online.)

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Criteria of Relative Abundance of Alkyl PAHs 327

0.0 0.4 0.8 1.2 1.6 2.0 2.4 2.8 3.2 3.6 4.0

0.0 0.4 0.8 1.2 1.6 2.0 2.4 2.8 3.2 3.6 4.0 0.0 0.4 0.8 1.2 1.6 2.0 2.4 2.8 3.2 3.6 4.0 4.4

0.0 0.4 0.8 1.2 1.6 2.0 2.4 2.8 3.2 3.6 4.0 4.4 4.8

CO

CC

WC

BS

GC

DC

CO

CC

WC

BS

GC

DC

CO

CC

WC

BS

GC

DC

CO

CC

WC

BS

GC

DC

MP/P

MC/C MPAHs/PAHs

MPy/Py

(a) (b)

(c) (d)

Figure 10. Graph of the ratios of methylated polycyclic aromatic hydrocarbons (PAHs) to parent PAHs in source materials. CO, crude oil; DC, diesel carsoot; GC, gasoline car soot; CC, coal cooking soot; BS, brick manufacturing soot; WC, wood cooking soot. (color figure available online.)

from 1999–2000 (Pandit et al., 2001; Viswanathan andKavi Kumar, 2005, Census of India, 2001). In contrast in WestBengal, including Kolkata as its capital, dirty fuel (mainly coaland fuel wood) is a large share of consumption for all expendi-ture groups over the entire period from 1983–2000 (Viswanathanand Kavi Kumar, 2005). Therefore, one main reason behindthe higher petrogenic PAHs input in Mumbai compared withKolkata and Chennai might be the usage of more kerosene inMumbai compared to the other two cities, since the unburnt fuelgradually mixed with watershed increasing the petrogenic inputin the respective water bodies.

Furthermore, comparing the alkyl PAHs ratios of all Indianurban sediments (Figure 9a–d) with that of source materials inFigure 10a–d, it is comprehensible that the higher range of MP/P,MPy/Py, and MC/C for Chennai and Mumbai sediment musthave a significant contribution of automobile related sources,whereas in Kolkata the lower range of MP/P, MPy/Py, and MC/Cshows that the sediment might have substantial input of coal andwood combusted sources, which produces the overall reducedvalue of alkylated PAHs ratios.

The sedimentary PAH compositional pattern for all the citieswas checked to track the contaminant source and illustrate thefate and transport of PAHs in the multimedia environment. Asignificant difference in PAH profiles of Kolkata, Chennai and

Mumbai was shown with comparatively higher phenanthreneconcentration and lower methylphenanthrene concentration insediment from Kolkata than that of Chennai and Mumbai (Fig-ure 11). Comparing the sedimentary PAH profile of these threecities with the PAH profile of source materials from a previousstudy (Saha et al., 2009), a similarity was observed betweenthe Kolkata sediment PAH profile and the PAH profile of coalcombustion-derived soot from brick yards. Both of these PAHsignatures were dominated by phenanthrene with proportionallylower concentrations of fluoranthene and pyrene, and very lowmethylphenanthrene and other alkyl PAHs. This resemblanceindicates the possibility of bulk deposition of coal combustion-derived soot from a large number of brick manufacturing in-dustries, situated along the Gangetic plane adjoining the city ofKolkata (65% of all the brick factories in India), into the urbanwater bodies by means of direct disposal and atmospheric depo-sition. Compared with Kolkata, there are fewer brick factoriesaround Chennai and Mumbai (35% of India), which are situ-ated along the peninsula and coastal India (Singh and SarfarazAsgher, 2005). This finding may also explain the highest PAHconcentration in Kolkata sediment because of the high adsorp-tion affinity of PAHs for soot particles.

The PAH fingerprints of Chennai and Mumbai sediment arevery similar to each other, which signifies that the PAHs input

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0

5

10

15

20

25P

he

Ant

h

1-M

P

3-M

P

2-M

P

9-M

P

Fluo Pyr

b-M

pyr

c-M

pyr

d-M

pyr

BaA

Chr

y

e-M

chr

y

f-M c

hry

g-M

chr

y

h-M

chr

y

i-M c

hry

BbF B

F

BeP

BaP

Per

y

IndP

y

Bgh

iP

Cor

Rel

ativ

e co

mpo

sitio

n%

0

5

10

15

20

25

Phe

Ant

h

1-M

P

3-M

P

2-M

P

9-M

P

Fluo Pyr

b-M

pyr

c-M

pyr

d-M

pyr

BaA

Chr

y

e-M

chr

y

f-M c

hry

g-M

chr

y

h-M

chr

y

i-M c

hry

BbF B

F

BeP

BaP

Per

y

IndP

y

Bgh

iP

Cor

Rel

ativ

e co

mp

ositi

on%Chennai Mumbai

0

5

10

15

20

25

Phe

Ant

h1-

MP

3-M

P2-

MP

9-M

PFl

uo Pyr

b-M

pyr

c-M

pyr

d-M

pyr

BaA

Chr

ye-

M c

hry

f-M

chr

yg-

M c

hry

h-M

chr

yi-M

chr

yB

bF BF

BeP BaP

Pery

IndP

yB

ghiP

Cor

Rel

ativ

e co

mpo

sitio

n % Kolkata

(a) (b)

(c)

Figure 11. Graph of the sedimentary polycyclic aromatic hydrocarbons (PAHs) profile of canal sediment of: (a) Chennai, (b) Mumbai, and (c) Kolkata.

was influenced by identical sources in both these cities (Fig-ure 11). However, the PAHs profile does not exactly match withany particular source materials in this study, perhaps becausesediments in these two cities may not be affected by a particularsingle source. Instead multiple sources may be responsible forthe PAHs input. Comparing the sedimentary PAH profile in thethree cities, little depletion of lower molecular weight PAHs wasobserved, even in Chennai and Mumbai and also there was notmuch difference in the H/L ratios among the three cities (Ta-ble 4). This finding again signifies that the effect of microbialdegradation might be negligible.

Comparing isomer pair ratios, the present study alsosuggests a strong pyrogenic input for all samples in Chennai,Mumbai and Kolkata, since almost all the locations in thethree cities show Phe/Anth<10, Pyr/Fluo<1 (except CC4),Anth/(Anth+Phe)>0.1, Fluo/(Fluo+Pyr)>0.5, BaA/(BaA+Chry)>0.35 and some locations have IP/(IP+BghiP)>0.5(Table 4), which is consistent with coal, charcoal, grass andwood combustion (Yunker et al., 2002).

Hopanes in Sediments

Noticeable amount of hopanes were detected in the sediments ofKolkata, Chennai, and Mumbai. The average total concentration

of hopanes in the three cities is almost comparable; 8.03 μg/gdry for Chennai, 5.67 μg/g dry for Mumbai, and 8.11 μg/gdry for Kolkata (Table 4 and Figure 12). The exceptionallyuniform hopane patterns in all the sediment samples may be ex-plained by a single dominant source of hopane for all three cities(Figure 13). The sedimentary hopane profile of individual citiesis more similar to automobile exhaust sources (Saha et al., 2009)

0 5000 10000 15000 20000Total Hopanes (ng/g-dry)

Kolkata

Mumbai

Chennai

Figure 12. Graph of the total hopane concentration in canal sediments fromIndian metro cities, Chennai, Mumbai and Kolkata.

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Criteria of Relative Abundance of Alkyl PAHs 329

Figure 13. Graph of the sedimentary hopane profile in canal sediment of three Indian metro cities: (a) Chennai, (b) Mumbai, and (c) Kolkata.

with a dominance of α isomers over β isomers. Furthermore, thesimilar patterns of C31S and C31R (i.e., C31S>C31R), C2917α

and C3017α (i.e., C2917α > C3017α) and higher homohopaneindex for all samples with automobile related sources indicatehopane contribution in the sediment was more dominated by pet-rogenic sources such as automobile exhaust derived from dieseland gasoline combustions than hopanes derived from maturecoal.

To comprehend the dominance of pyrogenic and petrogenicPAHs in the sediments, C30 hopane/total PAHs was calcu-

0.0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9C30Hopane/Total PAHs

Kolkata

Mumbai

Chennai

Figure 14. Graph of the C30 hopane to total polycyclic aromatic hydrocar-bons (PAHs) ratio in canal sediments from Indian metro cities—Chennai,Mumbai, and Kolkata. (Color figure available online).

lated. Figure 14 shows a comparatively smaller range of C30

hopane/total PAHs for the Kolkata sediments (0.04–0.14) thanthat for the Chennai (0.16–0.46) and Mumbai (0.07–0.83) sed-iment. Some of the sediment samples in Chennai and Mumbaihave higher C30 hopane/total PAHs but they are much lower incomparison with C30 hopane/total PAHs for other tropical Asiancountries (0.04–3.04) (Saha et al., 2009). The relatively lowerC30 hopane/total PAHs value for Indian sediment supports onceagain the dominance of pyrogenic PAHs input over petrogenicPAHs. The comparatively higher value of C30 hopane/total PAHsin Chennai and Mumbai than in Kolkata could be explained bythe enormous growth of the automobile population in these twocities compared with Kolkata (Ministry of Surface Transport,Government of India, 1997–1998; Jalihal et al., 2005). Sincehopanes are mainly derived from automobile-related sources,the higher proportion of the automobile population in Mumbaiand Chennai could be responsible for the higher C30 hopane/totalPAHs in these two cities.

Conclusion

This study demonstrates the application of PAH ratios forsource identification. Specifically, it applies four PAH ra-tios (MP/P<0.5, MPy/Py<0.15, MC/C<0.2, and MPAHs/

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330 M. Saha et al.

PAHs<0.3). Petrogenic PAHs are recognized in samples withsignificantly higher PAH ratios (MP/P>3.5, MPy/Py>1.5,MC/C>2.0, and MPAHs/PAHs>2.2). PAHs from mixtures ofpyrogenic and petrogenic sources exhibit intermediate PAHsratios [MP/P, MPy/Py, MC/C, and MPAHs/PAHs between(0.5–3.5), (0.15–1.5), (0.2–2.0), and (0.3–2.2), respectively].

This study shows that Indian sewage canal sediments arehighly contaminated with PAHs. Kolkata sediments contain thehighest PAH concentrations. Source apportionment of PAHs,based on the relative abundance of alkyl PAHs, and C30 hopane/total PAHs ratio revealed an elevated input of pyrogenic PAHsin the canals of Kolkata with a very low range of MP/P, MPy/Py,MC/C, and C30 hopane/total PAHs ratio. Fingerprinting of sedi-mentary PAHs with source materials indicated that the PAHs arepossibly originated from the combustion of coal and biomass(grass and wood), used in domestic cooking and various indus-tries such as power plants and brickyards. The slightly higheralkyl PAHs/PAHs and C30 hopane/total PAHs ratios among theChennai and Mumbai sediments compared with the Kolkatasediments were attributed to the presence of minor amounts ofpetrogenic PAHs along with pyrogenic PAHs. Additionally, theChennai and Mumbai sediments may reflect the higher usageof clean cooking fuel (kerosene) and to some extent a compar-atively higher amount of automobile exhaust from gasoline anddiesel–powered vehicles.

Overall, the Indian sediments are more influenced by py-rogenic PAHs with minor contributions of petrogenic PAHs.These sediments exhibit significantly lower amounts of petro-genic PAHs compared to other tropical Asian countries. Theunique nature of Indian sediments is possibly due to massiveusage of fossil fuel (coal, coal products) and biomass (wood)as a major source of energy by most of the industries in India,whereas petroleum and its products are the major sources ofenergy in other tropical Asian countries. A more detailed in-vestigation of pyrogenic coal and wood sources in India is animportant task for future research.

Acknowledgement

We express special thanks to Mr. P. V. Unnikrishnan for his assis-tance during sampling in Chennai and Mumbai. This researchwas supported by the Environment Research and TechnologyDevelopment Fund (B-0904) of the Ministry of the Environ-ment, Japan, and Grant-in-Aid studies from the Ministry ofEducation and Culture of Japan (Project No. 22254001). Sev-eral graduates and undergraduates in LOG provided welcomeassistance with the fieldwork.

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