Pahs In India

ARTICLE IN PRESS

Chemosphere xxx (2006) xxx–xxx www.elsevier.com/locate/chemosphere

Polycyclic aromatic hydrocarbons (PAHs) concentrations and related carcinogenic potencies in soil at a semi-arid region of India Amit Masih, Ajay Taneja

*

School of Chemical Sciences, Department of Chemistry, St. Johns College, Agra, Uttar Pradesh 282 002, India Received 10 August 2005; received in revised form 7 December 2005; accepted 25 January 2006

Abstract A study of polycyclic aromatic hydrocarbons in surface soil was conducted at selected locations in Agra (semi-arid region of India) for a span of one year in order to ascertain the contamination levels. The concentrations of PAH were measured at four locations in the city of Agra, which covers industrial, residential, roadside and agricultural areas. The samples were extracted with hexane by ultrasonic agitation. The extracts were then fractioned on a silica-gel column and the aromatic fraction was subjected to HPLC. The average concentration of total PAH in all samples was 12.1 lg g1 and the range was from 3.1 lg g1 to 28.5 lg g1. The maximum concentrations of PAHs were found to be in winter season. The concentration of PAH decreased in the order chrysene > benzo(b)fluoranthene > fluoranthene. Factor analysis suggests that the mixed signature of all the sources are intermediate between vehicular and combustion activities. Ó 2006 Elsevier Ltd. All rights reserved. Keywords: HPLC; Polycyclic aromatic hydrocarbon; Semi-arid region; Surface soil

1. Introduction Polycyclic aromatic hydrocarbons (PAHs) are chemicals containing two or more fused benzene rings in a linear, angular or cluster arrangement. PAH contain only carbon and hydrogen. They are usually generated under inefficient combustion conditions, such as insufficient oxygen (Sorensen, 1994; Nam et al., 2003) by primary natural sources which are forest fires and volcanic activity, but most of the PAHs released into the environment arise from anthropogenic sources such as burning of fossil fuels, petroleum refinery, industrial processes, as a constituent of coal tar and motor vehicle exhaust. The lighter PAH (2–3 rings), which are generally not carcinogenic, are mostly found in the gas phase while the heavier ones are mainly associated with airborne particles. Heavier PAH (with more than three rings) are rapidly attached to existing particles, usu-

*

Corresponding author. Tel.: +91 562 2800882. E-mail address: [email protected] (A. Taneja).

0045-6535/$ - see front matter Ó 2006 Elsevier Ltd. All rights reserved. doi:10.1016/j.chemosphere.2006.01.062

ally soot particles, by adsorption or condensation upon cooling of fuel gas (Kamens et al., 1995). The environmental occurrence of PAHs has been associated with adverse effects on public health (Grimmer et al., 1983; Yang et al., 1991; Rost and Loibner, 2002). Persistent organic pollutants (POPs) are transported in the atmosphere at over short and long distances in both gaseous and particulate forms. Although some POPs are released slowly into the atmosphere (Harner et al., 1995), these omnipresent compounds are subject to redistribution and transformation processes (Reilley et al., 1996; Massei and Ollivon, 2004). Atmospheric deposition constitutes the main input of semi-volatile organic compounds to soil (Tremolada et al., 1996). Once entered in the soil they accumulate in horizons rich in organic matter where they are likely to be retained for many years due to their persistence and hydrophobicity (Krauss et al., 2000). Consequently, soils are an important reservoir for these compounds (Ockenden et al., 2003) and exchanges between soils and the atmosphere is a widely studied process (Bidleman and McConnell, 1995; Wania and Mackay, 1996). With the increase

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in fossil fuel combustion, resulting from the industrial expansion, traffic and population growth, over last few decades, the atmospheric concentrations of PAH in Asian countries are expected to be high. Thus it is important to acquire information about this environmental compartment and its role in micro pollutant cycle. In India, few studies have reported ambient PAH concentration in Ahmedabad (Raiyani and Shah, 1993), Mumbai (Sahu et al., 2001), Delhi (Kannan and Kapoor, 2004). To our knowledge there has been a shortage of soil PAH studies. Since PAHs are one of the most serious pollutants because of their carcinogenicity and mutagenicity (IARC, 1983; Yang et al., 1991; Massei and Ollivon, 2004) which have drawn attention of the scientific community, it is important to determine the amounts of PAHs in soil as their concentration in soil correlates significantly with the corresponding levels in air (Vogt et al., 1987; Nam et al., 2003; Massei and Ollivon, 2004) and is a good indicator of the surrounding air pollution and the proximity of sources. The aim of this study was to determine soil contamination by PAHs and to identify sources based on variations in PAHs profiles between the sites as well as to assess the carcinogenic potencies related to PAHs. 2. Materials and methods 2.1. Regional site description Agra, the city of Taj Mahal (27°10 0 N 78°02 0 E) is located in the north central part of India about 200 kms South of Delhi in the Indian state of Uttar Pradesh. Agra is considered as a semi-arid zone as two third of its boundary are surrounded by the Thar desert of Rajasthan. Three highways are crossing the city. The climate during summer is hot and dry with temperature ranging from 32 °C to 48 °C. In winter the temperature ranges from 5.5 °C to 30.5 °C. The down ward wind is south–south-east i.e. SSE 29% and north-east i.e. NE 6% in summers and it is west–north-west i.e. WNW 9.4% and north–north-west i.e. NNW 11.8% in winters. The atmospheric pollution load is high because of the down ward wind; pollutants may be transported to the different areas mainly from an oil refinery situated in Mathura (50 kms from the center of Agra City). Agra has 1 271 000 of population. 3 86 635 vehicles are registered and 32 030 generator sets are used. It has been indicated earlier that in Agra, 60% pollution is due to vehicles (CPCB, Amar Ujala, 2005). St. John’s College, which is situated in the heart of Agra city, is considered as a roadside area. It lies by the side of a road that carries a maximum traffic density of about 105 vehicles per day, which results in production of smoke, and total suspended particulate matter by engine idling and gear changes. Nunhai has being considered as an industrial zone because large number of diesel generator sets plants, iron processing and tanning industries are there. Towards the north is located Dayalbagh which is exclusively agricultural area. The Taj trapezium (area surrounding the Taj

Mahal 10 400  km2) located to the south of the site is considered to be a residential area, which is totally a green belt. 2.2. Sample collection For the purpose of sample collection Agra city was divided into four parts based on industrial, roadside, agricultural and residential locations. Samples were collected with the help of an auger from 0 to 6 cm of topsoil. A total of 319 soil samples were collected (80 from each location) for analysis. The collected samples were sieved through 20-mesh sieve and stored in polybags in a refrigerator. 2.3. Extraction and analysis of PAHs Twenty gram of soil sample was extracted for 45 min with hexane (30 ml) in an ultrasonic bath extractor. The extract was decanted at the rate of 3300 rpm in a decanter (Supelco) and then passed through silica-gel column for the purification (EPA, 1994). The obtained extract was evaporated by a flow of nitrogen and redissolved in 1 ml of Acetonitrile. The extract was analysed for PAH’s by using the HPLC with UV visible detector (Shimadzu LC-10AD). The analytical column was of 250 mm length and 4.6 mm i.d; packed with totally porous spherical RP-18 material (Particle size 5 lm) preceded by a guard column (10 mm long and 4.6 mm i.d.). Acetonitrile–water mixture (70:30) was used as mobile phase at a flow rate of 1.5 ml min1. Samples of 100 ll (0.1 ml) were injected into the column through the sample loop. For the detection of compounds UV detector was set at 254 nm for analysis. The data was processed with a CR7A chromatopac data processor. Standards were obtained individually (as the solids) from polyscience Chemical Company, USA. The following compounds were quantified: naphthalene, acenaphthene, acenaphthylene, fluorene, phenanthrene, anthracene, fluoranthene, pyrene, benzo(a)anthracene, chrysene, benzo(b) fluoranthene, benzo(k)fluoranthene benzo(a)pyrene and benzo(ghi)perylene. All these compounds are on the USEPA priority pollutants list. The procedure described above has been checked for recovery efficiencies using spiked PAH standards. Recoveries range between 30% and 70%, with the lower values corresponds to the lower molecular weight PAH compounds. Presented data are corrected accordingly with the means of triplicate analyses. Replicated analyses give an error between ±10% and ±20% for PAH in soils. 3. Results and discussion 3.1. PAHs in soil particles The average and standard deviation of individual PAH concentrations measured in soils at the various sites are presented in Table 1. The total PAH (t-PAH) concentrations were 13.72, 12.98, 9.37 and 6.73 lg g1 at industrial, roadside, residential and agricultural sites respectively. The

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Table 1 Mean concentration with SD of PAHs at different locations of Agra (lg g1) PAHs

Industrial

Roadside

Residential

Agricultural

Mean ± SD

Mean ± SD

Mean ± SD

Mean ± SD

NAP ACY ACE + FLU PHE ANT FLT PYR B(a)A CHR B(b)F B(k)F B(a)P B(ghi)P

1.18 ± 1.11 0.62 ± 0.54 1.06 ± 1.72 0.43 ± 0.51 1.29 ± 1.12 1.72 ± 1.02 ND 0.81 ± 1.06 4.07 ± 2.26 1.53 ± 1.47 ND ND 1.01 ± 1.09

1.07 ± 1.84 0.47 ± 0.62 0.97 ± 1.88 0.32 ± 0.37 1.02 ± 0.66 1.29 ± 1.17 1.23 ± 1.41 0.56 ± 0.45 3.19 ± 2.36 1.32 ± 1.20 0.30 ± 0.83 0.39 ± 0.36 0.85 ± 0.72

0.90 ± 1.16 0.33 ± 0.57 0.82 ± 1.20 0.47 ± 0.66 0.57 ± 0.39 0.89 ± 1.11 ND 0.45 ± 0.31 3.03 ± 2.91 1.27 ± 1.41 ND ND 0.64 ± 0.79

0.69 ± 0.77 0.42 ± 0.61 0.63 ± 0.60 0.14 ± 0.31 0.36 ± 0.21 0.58 ± 0.32 ND 0.26 ± 0.21 2.19 ± 2.18 0.92 ± 1.42 ND ND 0.54 ± 0.43

Total

13.72 ± 11.90

12.98 ± 13.87

9.37 ± 10.46

6.73 ± 7.12

NAP—Naphthalene, ACY—Acenapthylene, ACE—Acenapthene, FLU—Fluorene, PHE—Phenanthrene, ANT—Anthracene, FLT—Fluoranthene, PYR—pyrene, B(a)A—Benzo(a)fluoranthene, CHY—Chrysene, B(b)F—Benzo(b)fluoranthene, B(k)F—Benzo(k)fluoranthene, B(a)P—Benzo(a)pyrene, B(ghi)P—Benzo(ghi)perylene.

mean concentration of t-PAH was 12.14 lg g1 for all sites together. The industrial sites had the highest total PAH concentration followed by roadside, residential and agricultural site. High concentrations at industrial site can be due to the location of the site, which is well known for generator manufacturing, tanning and iron casting industries. Concentrations at roadside may result from the proximity of the busy road, which has very intense automobile traffic about 105 vehicles per day. Trapido (1999) estimated PAH content at agricultural site about 0.10 lg g1 which was considered as background value for PAH. Observed value (6.70 lg g1) of PAH at agricultural site is higher than the background levels may be due to the atmospheric transport of PAH from sources to remote sites. These results also indicate that PAH concentration are strongly linked to the land use of the site. The trends of the concentrations of the major PAH found in present study were chrysene > fluoranthene > benzo(b)fluoranthene at industrial site, chrysene > benzo(b)fluoranthene > fluoranthene at roadside and chrysene > benzo(b)fluoranthene > naphthalene at residential and agricultural sites. In all the sites chrysene and benzo(b)fluoranthene were the predominant compounds. This might be due to industrial-oil burning, wood combustion and emission coming from diesel powered vehicles (Ravindra et al., 2001). Table 2 shows a worldwide comparison of PAH concentration with the present study. The PAH concentration in soil of industrial (13.72 lg g1) and roadside (12.98 lg g1) area of Agra is less than the concentration found in Austria/ Germany (79.00/16.00 lg g1) and USA (58.60 lg g1), respectively, whereas residential (9.37 lg g1) and agricultural (6.73 lg g1) sites concentrations of PAH were found to be higher than in UK (4.20 lg g1) and Germany (1.90 lg g1), respectively. As evident from the Table 2 the concentrations measured in soils of various sites at Agra (industrial, roadside, residential and agricultural) show

Table 2 Soil PAH concentrations compiled from literature data Study area

PAH concentration (lg g1)

Number of PAH

Reference

Agricultural (rural) Brazil 0.096 UK 0.19 Germany 1.90 India 6.7

20 12 06 11

Wilcke et al. (1999a) Wild and Jones (1995) Tebaay et al. (1993) Present study

Residential (urban) Bangkok 0.38 Brazil 0.39 Germany 1.80 UK 4.20 India 9.3

20 20 06 12 11

Wilcke and Muller (1999b) Wilcke et al. (1999a) Tebaay et al. (1993) Wild and Jones (1995) Present study

Roadside (urban) Australia 3.30 USA 58.68 India 12.9

14 14 14

Yang et al. (1991) Rogge et al. (1993) Present study

Industrial (urban) UK 4.50 Germany 16.00 Austria 79.00 India 13.7

12 06 18 11

Wild and Jones (1995) Tebaay et al. (1993) Weiss et al. (1994) Present study

much difference between each other. In the present data, contamination in the urban industrial area appears to be two times higher than in agricultural areas; similar results have been reported in earlier studies (Tremolada et al., 1996; Wagrowski and Hites, 1997). Fig. 1 shows the relative contribution of 2-, 3-, 4-, 5-, and 6-ring PAHs in the soils of different locations investigated in this study. The average percentage of t-PAH based on the rings were 9.15% (2 ring), 23.1% (3 ring), 47% (4 ring), 13.4% (5 ring), and 7.15% (6 ring). The Fig. 1 also illustrates that 4-ring and 3-ring PAHs were found to be

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Fig. 1. Distribution of PAHs in the soil of different locations of Agra.

dominant in the soils of Agra region having 47% and 23.1% of the t-PAH whereas 5-ring compounds including benzo(a)pyrene (considered to be most carcinogenic compound) contributes only 13.4% of the t-PAH. 3.2. Seasonal variation The climate of Agra can be broadly classified into three seasons, winter (November–February), summer (March– June) and monsoon (July–October). Table 4 summarizes the seasonally averaged concentrations of all measured PAH in soil at four sites of Agra; i.e. industrial, roadside, residential and agricultural. The concentrations of PAH in winter, summer and monsoon are dominating in industrial area i.e. 20.45, 13.43 and 7.28 lg g1, respectively, whereas the lowest concentrations of PAH are formed to be in agricultural area i.e. 10.18, 6.21 and 3.80 lg g1, respectively. The concentrations of PAH in roadside as well as residential sites were found to be 17.07 and 13.04 lg g1 in winter, 12.12 and 9.25 lg g1 in summer and 9.75 and 5.82 lg g1 in monsoon. The differences in PAH concentration in soil is due to the characteristics of individual sites. Although the trend of seasonal variation of all PAH at all the sites is similar in nature i.e. maximum concentration of PAH were found to be in winter followed by summer and monsoon seasons. This trend can be easily visualized in Fig. 2. Differences in concentration of PAH in soil can be explained with the different meteorological conditions of these seasons. Temperature of soil is a very important factor in determining the leachability or mobility of soil PAH. In this region, summer is generally characterized by high temperature ranging from 35 °C to 47 °C. The leaching concentration of PAH at present site increases with increasing temperature as biodegradation and volatility accompanied by rising temperature (Kim and Osako, 2003), resulting the lower PAH in the summer than in winter season. In contrast, in the winter season at low temperature microbial breakdown of PAH is decreased resulting

the higher concentration of PAH at this season. While during the months of monsoon season the region is generally experienced with the frequent rain showers and washout effects of pollutants. In addition to dry deposition, wet deposition (rain) of PAH may also occur at soil surface in this season and should have resulted in higher soil PAH concentration. In contrast, the concentration of soil PAH was observed to be lower in monsoon. Lower concentration of PAH during the monsoon season in this region can be explained due to the percolation of PAH into the inner depth of the soil. Although, percolation of PAH depends on several factors like PAH molecular structure, water solubility, Henry’s constant, mode of transport and flow rate. The total PAH ratios of winter and Monsoon (W/M) seasons varied from 1.8 to 2.8 with the maximum (W/M) ratios observed for industrial followed by agriculture, residential and roadside. Lower (W/M) ratios of PAH at roadside soil may be due to the high vehicular emissions and the continuous deposition of PAH on roadside at all seasons. 3.3. Factor analysis A varimax rotated factor analysis was performed to identify the main sources influencing the PAH concentration at the sampling sites. In this statistical method a set of multiple inter correlated variables is replaced by small number of independent variables (factors) by orthogonal transformations (rotations). This is achieved by diagnosing the correlation matrix of the variable i.e. by computing their Eigen values and Eigen vectors. Factor loadings obtained after the rotation called varimax rotation gives the correlation between the variables and the factors. Each variable was also evaluated for its KMO value (Keiser Mayer Olvin), which gives sampling adequacy, and data was included in the matrix only if it had Eigen values greater than one. The varimax procedure was adopted for rotation of the factor matrix to transfer the initial matrix into one that was easier to interpret. In the present Table 3 Mean, range and TEFs of PAHs with BAP exposure at Agra (lg g1) PAHs NAP ACY ACE + FLU PHE ANT FLT PYR B(a)A CHR B(b)F B(k)F B(a)P B(ghi)P Total a

Range

TEFsa

BAPexposure

0.96 0.46 0.87 0.34 0.81 1.12 1.23 0.52 3.12 1.26 0.30 0.39 0.76

0.27–2.06 0.09–1.56 0.10–1.90 0.06–0.96 0.10–1.88 0.38–2.98 0.49–3.07 0.12–1.61 0.99–6.44 0.34–2.64 0.04–0.71 0.07–0.94 0.14–1.79

0.001 0.001 0.001 0.001 0.01 0.001 0.001 0.1 0.01 0.1 0.1 1 0.01

0.00096 0.00046 0.00087 0.00034 0.0081 0.00112 0.00123 0.052 0.0312 0.126 0.030 0.39 0.0076

12.14

3.19–28.54

1.33

0.65

Mean

TEFs compiled by Tsai and Shih (2004).

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Table 4 Seasonal average concentrations of PAHs in soil at different sites of Agra (lg g1) PAHs

Industrial

Roadside

Residential

S

M

W

Agricultural

S

M

W

S

M

W

S

M

W

NAP ACY ACE + FLU PHE ANT FLT PYR B(a)A CHR B(b)F B(k)F B(a)P B(ghi)P

1.28 0.59 1.14 0.22 1.31 1.61 ND 0.56 4.23 1.53 ND ND 0.96

0.63 0.41 0.72 0.45 0.79 0.68 ND 0.84 1.62 0.79 ND ND 0.35

1.63 0.86 1.32 0.62 1.77 2.87 ND 1.03 6.36 2.27 ND ND 1.72

0.92 0.41 0.83 0.28 0.91 1.24 1.19 0.53 3.21 1.12 0.25 0.39 0.84

0.87 0.27 0.72 0.14 0.89 1.12 1.11 0.36 2.24 0.87 0.15 0.31 0.70

1.42 0.73 1.36 0.54 1.26 1.51 1.31 0.79 4.12 1.97 0.50 0.47 1.01

0.83 0.32 0.73 0.41 0.57 0.80 ND 0.44 3.39 1.17 ND ND 0.59

0.74 0.21 0.68 0.37 0.32 0.78 ND 0.32 1.08 0.81 ND ND 0.51

1.13 0.46 1.05 0.63 0.82 1.09 ND 0.59 4.62 1.83 ND ND 0.82

0.66 0.36 0.53 0.12 0.28 0.55 ND 0.22 2.09 0.91 ND ND 0.49

0.49 0.12 0.39 0.08 0.21 0.40 ND 0.14 0.92 0.66 ND ND 0.39

0.92 0.78 0.97 0.22 0.59 0.79 ND 0.42 3.56 1.19 ND ND 0.74

Total

13.43

7.28

20.45

12.12

9.75

17.07

9.25

5.82

13.04

6.21

3.80

10.18

S—summer, M—monsoon, W—winter.

ROADSIDE

INDUSTRIAL

MONSOON

MONSOON

Concentration (µg g-1)

10 8 6 4 2

SUMMER

PAHs

B(ghi)P

B(a)P

CHR

B(k)F

B(ghi)P

B(k)F

B(a)P

B(b)F

CHR

B(a)A

PYR

FLT

B(ghi)P

B(k)F

B(a)P

B(b)F

CHR

PYR

B(a)A

FLT

ANT

PHE

ACE+FLU

0

ANT

2

PHE

4

WINTER

7 6 5 4 3 2 1 0 NAP

Concentration (µg g-1)

6

MONSOON

ACE+FLU

WINTER

ACY

MONSOON

8

ACY

B(b)F

AGRICULTURAL

10

NAP

B(a)A

FLT

PAHs

RESIDENTIAL

SUMMER

PYR

ANT

PHE

ACY

ACE+FLU

NAP

B(ghi)P

B(k)F

B(a)P

CHR

B(b)F

B(a)A

FLT

PYR

ANT

PHE

ACY

ACE+FLU

0

PAHs

Concentration (µg g-1)

WINTER

12

10 8 6 4 2 0

SUMMER

WINTER

14 12

NAP

Concentration (µg g-1)

SUMMER

PAHs

Fig. 2. Seasonal trends of PAH at different sites.

study, the SPSS (version 7.5) computer software was used to perform factor analysis. Results obtained by varimax rotated factor analysis are given in Table 5. Shown results in the table have loading > 0.5, because they are deemed to be statistically signif-

icant. As presented in Table 5, at all the sites only one factor is extracted except that of industrial site which is having two factors. Agricultural, residential and roadside contributed 89.9%, 91.6%, 86.6%, variance of data set, respectively, whereas at the industrial site total of 98.8%

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Table 5 Results of factor analysis with varimax rotation on PAHs in soil of Agra PAHs

NAP ACY ACE + FLU PHE ANT FLT PYR B(a)A CHR B(b)F B(k)F B(a)P B(ghi)P Eigen value % of variance Cumulative % Predicted sources

Agricultural

Residential

Roadside

Industrial

Factor 1

Factor 1

Factor 1

Factor 1

Factor 2

0.95 0.98 0.97 0.84 0.96 0.95 – 0.94 0.98 0.97 – – 0.89 8.9 89.9 89.9 Incineration

0.89 0.95 0.97 0.97 0.96 0.95 – 0.94 0.92 0.99 – – 0.98 9.1 91.6 91.6 Oil burning and incineration

0.96 0.97 0.96 0.97 0.95 0.95 0.93 0.95 0.81 0.98 0.97 0.71 0.91 11.2 86.6 86.6 Vehicular activities

0.99 0.91 0.99 0.19 0.97 0.94 – 0.96 0.98 0.97 – – 0.96 8.1 81.8 81.8 Coal combustion

0.01 0.34 0.01 0.97 0.19 0.31 – 0.97 0.18 0.25 – – 0.20 1.7 17.0 98.8 Oil combustion activities

Loading greater than 0.5 is significant.

data is extracted with the two factors, 81.8% and 17% loading of each group. In agricultural areas, incineration may be the main source of PAH in soil. Because all wastes are dumped out of the city which are very close to these agricultural sites and this dumped waste is incinerated time to time. Moreover, pumping sets is also used for the irrigation purpose, which is run by diesel. Similarly, in residential areas incineration as well as diesel burning might be the source of soil PAH. Diesel generators are used to generate electricity because of erratic supply of electricity in the residential areas. Whereas in roadside soil, the main source of PAH is vehicular activities. Number of the diesel and petrol vehicles especially two and three wheelers is used for local transportation of the public (traffic density is about 105 vehicles per day). In addition, ratios between pairs of individual PAH have also been calculated. A ratio of 1 for Flt/Pyr and 1–2 for B(a)A/B(a)P indicated the PAH origin is likely to be from combustion and motor vehicles exhaust, respectively (Yang et al., 1991; Nam et al., 2003). Concentration of Pyr and B(a)P are found to be below detection levels at residential, agricultural and industrial site, therefore ratios of these sites are not calculated. In the present study, Flt/Pyr and B(a)A/B(a)P ratios are found to be 1.0 and 2.4 at only roadside site, which is similar to the reported data by Nam et al. (2003) and Yang et al. (1991). Thus, it would be appear that at roadside site motor vehicle exhausts are the dominant source of PAH in the soil of Agra. In industrial area, coal burning and oil combustion may be the major source of PAH’s as they are used for heating the furnaces etc. In above all, Mathura refinery is situated at about 40 km of the Agra city. The unit must be emit significant amount of the PAH’s which can probably get transported to the Agra city. Thus, obtained results of factor analysis suggest

that the mixed signature of all the sources are intermediate between vehicular and combustion activities. 3.4. Assessing PAH exposure profiles Yet, occupational exposure limit for total-PAHs has not been established because of the complexity of PAHs in their chemical composition. Several PAH species including benzo(a)pyrene (as most carcinogenic compound) have been classified into probable (2A) or possible (2B) human carcinogens by the International Agency for Research on Cancer (IARC, 1987). BaP is a five ring (C20H12) compound, which is mutagenic for human cells in culture (Osborne and Crosby, 1987) and carcinogenic in whole animal assays (Cerna et al., 2000). According to the literature, the toxic equivalent factor for BaP is one (1), which is highest among all the PAHs. One approach in estimating the carcinogenic potency associated with the exposure of a given PAH compound can be obtained by calculating its BaPeq for each individual PAH species. In order to calculate the carcinogenic potencies associated with the total PAH exposures from soil; we pragmatically used the sum of each individual BaPeq (i.e., total-BaPeq) as a surrogate indicator. Therefore in the present study toxic equivalent factor (TEF) of the given species relative to BaP carcinogenic potency have been used. The above method has the main advantage of being relatively easy to apply in the environments affected by human sources, however, may underestimate risk due to not all PAH, but only limited compounds, are considered (WHO/IPCS, 1998). For pragmatic purpose, the list of TEFs compiled by Tsai and Shih (2004) was adopted in this study. Table 3 shows the concentrations of PAHs in soil which is below than 1 lg g1 indicating that soil PAH exposure is not carcinogenic at

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present level of emissions in Agra. It should be noted that the above inference was based on the exposure of soil to each individual PAH compound not for t-PAHs. 4. Conclusion Out of 16 EPA priority PAHs, 14 PAHs were found in the surface soils of Agra. The t-PAH concentrations were found to be 13.72, 12.98, 9.37 and 6.73 lg g1 at industrial, roadside, residential and agricultural sites, respectively. The mean concentration of t-PAH was 12.14 lg g1 for all sites together. In all the sites chrysene and benzo(b)fluoranthene were the predominant compounds as a result of anthropogenic activities. The industrial sites had the highest t-PAH concentration followed by roadside, residential and agricultural site. The average percentage of t-PAH based on the rings were 9.15%, 23.1%, 47%, 13.4%, and 7.15% for 2, 3, 4, 5 and 6 rings, respectively. The concentrations of PAH in winter, summer and monsoon are dominating in industrial area i.e. 20.45, 13.43 and 7.28 lg g1, respectively, whereas the lowest concentrations of PAH are formed to be in agricultural area i.e. 10.18, 6.21 and 3.80 lg g1, respectively. Results obtained by varimax rotated factor analysis are found to be statistically significant. The carcinogenic potency of PAH compounds were calculated and found to be insignificant at the present level of emissions in Agra. Acknowledgements We thank Dr. F.M. Prasad, Principal, St. John’s College for his encouragement. We also thank Dr. Ashok Kumar, (Head) Department of Chemistry, St. John’s College, Agra for providing us the necessary facilities and Dr. G.S. Satsangi for her valuable suggestions. References Amar Ujala, 2005. Agra dilemma (News item), November 29, P–9. Bidleman, T.F., McConnell, L.L., 1995. A review of field experiments to determine air water gas exchange of POPs. Sci. Total Environ. 159 (23), 101–117. Cerna, M., Pochmanova, D., Pastorkova, A., Bene, I., Lenicek, J., Topinka, J., et al., 2000. Genotoxicity of urban air pollutants in the Czech Republic Part I. Bacterial mutagenic potencies of organic compounds adsorbed on PM10 particulates. Mutat. Res.-Gen. Toxicol. 469, 71–82. Environmental Protection Agency (EPA), 1994. Test methods for evaluating solid waste, physical/chemical methods SW-846. Revision 2, Office of solid waste and emergency response, Washington, DC, USA. Grimmer, G., Jacob, J., Naujack, K.W., Detbarn, G., 1983. Determination of Polycyclic aromatic hydrocarbons emitted from brown-coalfired residential stoves by gas chromatography/mass spectrometry. Anal. Chem. 55, 892–900. Harner, T., Mackay, D., Jones, K.C., 1995. Model of the long-term exchange of PCBs between soil and the atmosphere in the southern UK. Environ. Sci. Technol. 29 (5), 1200–1209. IARC Monograph Evaluation, 1983. Carcinogens. Risks Humans, 32 pp.

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