Characterization of Atmospheric Polycyclic Aromatic Hydrocarbons in a Mixed-Use Urban Community in Paterson, NJ: Concentrations and Sources

ABSTRACT

Exposure to ambient polycyclic aromatic hydrocarbons (PAHs) is a potential health concern for communities because many PAHs are known to be mutagenic and carcinogenic. However, information on ambient concentrations of PAHs in communities is very limited. During the Urban Community Air Toxics Monitoring Project, Paterson City, NJ, PAH concentrations in ambient air PM₁₀ (particulate matter ≤ 10 μm in aerodynamic diameter) were measured from November 2005 through December 2006 in Paterson, a mixed-use urban community located in Passaic County, NJ. Three locations dominated by industrial, commercial, and mobile sources were chosen as monitoring sites. The comparison background site was located in Chester, NJ, which is approximately 58 km west/southwest of Paterson. The concentrations of all of the individual PAHs at all three Paterson sites were found to be significantly higher than those at the background site (P < 0.05). The PAH profiles obtained from the three sites with different land-use patterns showed that the contributions of heavier PAHs (molecular weight > 202) to the total PAHs were significantly higher at the industrial site than those at the commercial and mobile sites. Analysis of the diagnostic ratios between PAH isomers suggested that the diesel-powered vehicles were the major PAH sources in the Paterson area throughout the year. The operation of industrial facilities and other combustion sources also partially contributed to PAH air pollution in Paterson. The correlation of individual PAH, total PAH, and the correlation of total PAHs with other air co-pollutants (copper, iron, manganese, lead, zinc, elemental carbon, and organic carbon) within and between the sampling sites supported the conclusions obtained from the diagnostic ratio analysis.

IMPLICATIONS

The study provides a valuable approach to understand potential exposure in a mixed land-use urban community. Data obtained from the study (i.e., concentration and source profiles of PAHs at different sites in Paterson) are useful in helping to identify air pollution sources of concern. The findings of this research project may also be helpful in assisting regulatory agencies in developing effective strategies to control sources of air pollution and to better address community concerns.

INTRODUCTION

Polycyclic aromatic hydrocarbons (PAHs) are ubiquitous environmental pollutants and are generated by different combustion sources.1,2 In urban environments, the major sources of ambient PAHs are motor vehicle emissions, industrial operations, waste incinerators, and residential heating.3 Many PAHs are known animal carcinogens and are ranked as probable human carcinogens by the U.S. Environmental Protection Agency (EPA).4 Several epidemiologic investigations have shown increased incidence of lung cancer among workers with high PAH exposure.5,6 Hence, exposure to PAHs is a potential concern to local communities considering their proximity to possible local industrial sources and increased traffic density. However, ambient concentrations of PAHs at community settings are still limited. The impact of community exposure to PAHs on health effects remains to be determined.

The National Air Monitoring Strategy, which includes the Urban Air Toxic Monitoring (UATM) program, consists of an extensive network of fixed air pollution monitors throughout the country. However, it has been recognized that those monitors, although adequate for establishing trends, do not always reflect the various local air toxics problems that affect individual urban communities. In addition, PAHs are only measured in a few sites nationwide.

The Urban Community Air Toxics Monitoring Project, Paterson City, NJ (UCAMPP), which has been described elsewhere,7 was designed as an initial step in providing tools and methods for community-based monitoring in addition to valuable information on exposure and risk issues related to air toxics in an urban community. Paterson was chosen because it is a highly industrialized urban community with various land uses and mixed sources of air pollution. Previous studies conducted in Paterson reported that 21% of participating third-grade school children had been diagnosed with asthma or a related health problem,8 and the hospitalization rates because of asthma was more than 3 times higher than the state average.9 Thus, to better assess the impact of air pollution on community health and address the community concerns, the purposes of this paper are (1) to characterize and compare PAH concentrations at the industrial, commercial, and mobile monitoring sites in Paterson, NJ, and a background site in Chester, NJ; and (2) to identify major PAH sources at different study sites on the basis of the analysis of the diagnostic ratio between PAH isomers and the correlation of PAHs and other copollutants. The results of other air pollutants (e.g., elements, aldehydes, hexavalent chromium, organic carbon [OC]/elemental carbon [EC], and volatile organic compounds [VOCs]) measured in UCAMPP will be published elsewhere.

METHODS

Background of the Study Area

Paterson is the third largest city in New Jersey, with a high density of population. Paterson has the characteristics of an environmental justice community. According to the 2000 U.S. Census data, there are approximately 149,000 residents, of which one-third are white, one-third are black, and the balance are some other race. Fifty percent of the population considers themselves to be Hispanic or Latino,10 and 19% of the families in Paterson live at or under the poverty level, compared with 6.3% for the state. As previously stated, Paterson is a mixed land-use urban community that includes industrial (e.g., textiles. dyes; chemicals; metal fabrication, refinishing, and recovery; plastics; printing; electronics; paper and food products; etc.), commercial (e.g., dry-cleaning, fast food restaurants, photo laboratories, commercial heating/boilers, salons, print shops, etc.), and mobile sources (U.S. Interstate 80; Route 19; and County Routes 649, 639, and 648) that are interspersed with residential land use.

Sampling

Three monitoring sites in Paterson were selected for this study. Site selection was based on proximity to industrial, commercial, and mobile sources. Final selection of sites was judgment-based (i.e., accessibility and safety for field sampling staff and equipment). All of these sites contain and are fringed by residential land use, allowing for population-oriented air toxics monitoring. The commercial land-use/area-source-dominated site was surrounded by typical urban downtown sources such as fast food restaurants, commercial heating/boilers, and an active railway. The industrial land-use/stationary-source-dominated site was located in a highly industrialized area known as Bunker Hill with large industrial activities such as metal fabrication, refinishing, and recovery. The mobile land-use-dominated site was close to U.S. Interstate 80, a major New Jersey transit bus depot, and three county routes. Meanwhile, the background site was the New Jersey Department of Environmental Protection (NJDEP), designated the “background/rural” monitoring station, in Chester, NJ. This site is approximately 58 km west/southwest of Paterson and has been operating since 2001. There are no significant air pollution sources near (<1000 m) the background site. Detailed descriptions of the sampling sites are given in Table 1.

Table 1. Description of monitoring sites and background site

Monitoring Site	Monitoring Location	Dominant Source	Site Characteristics
Background	Chester, NJ	No identified local sources	58 km away from Paterson
			Designated background site for state UATM
Commercial	Paterson, NJ	Area sources	Typical urban downtown
			Close to the commercial district
			Near active railroad
Industrial	Paterson, NJ	Stationary sources	Heavily industrial impacted area
			Large industrial facilities
Mobile	Paterson, NJ	Mobile sources	Close to U.S. Interstate 80 and Route 19 and County Route 639, 673, and 648
			Near at New Jersey Transit Bus Depot and active railroad

The 24-hr integrated samples were collected every 6 days at all four sites from November 2005 to December 2006. The sampling frequency is the same as in the EPA ambient air monitoring program, which attempts to avoid collecting multiple samples that have been influenced by a single episode or event (e.g., release or inversion). One of the four-channel Partisol speciation samplers with a PM₁₀ (particulate matter ≤ 10 μm in aerodynamic diameter) sampling head (model 2300, Rupprecht & Patashnick, Co.) was used for PAH collection at all sites. Similar to EPA method TO-13, a 47-mm quartz fiber filter (QFF) and 1-in. diameter, 3-in. long polyurethane foam plugs were used for particle and gas PAH collection. The sampling flow rate was 16.7 L min⁻¹, yielding individual sample volumes of approximately 24 m³. After sampling, PUF plugs were placed in a prebaked glass jar with aluminum foil-lined lids whereas the QFFs were placed in aluminum foil pouches. All samples were transported in a cooler and stored in a freezer until analyzed.

PAH Analysis

The concentrations of the following 16 PAHs were quantified in the study: naphthalene (Nap), acenaphthylene (Ace), acenaphthene (Acen), fluorine (Flu), phenanthrene (Phen), anthracene (An), fluoranthene (Fluo), pyrene (Py), benzo(a)anthracene (BaA), chrysene (Chry), benzo(b)fluoranthene (BbF), benzo(k)fluoranthene (BkF), benzo(a)pyrene (BaP), indeno(1,2,3,-cd)pyrene (Indeo), dibenzo(a,h)anthracene (DiBa), and benzo(ghi) perylene (BghiP). After sample collection, filters and PUFs were Soxhlet extracted with 150 mL of dichloro-methane for 16 hr. To monitor the loss of PAHs during sample processing, 50 ng of deuterated surrogates (d_8- Nap, d₁₀-Phen, d₁₀-Pyr, d₁₂-BaP) were added to the sample before extraction. The extract was then concentrated to 100 μL under a gentle stream of nitrogen. After spiking with a known amount 5 ng of d₁₀-Ace and d₁₀-Acen as internal standards, the target PAHs were separated and analyzed on a Varian 3900 gas chromatograph coupled to a Saturn 2000 mass spectrometer ion trap detector operated in selective ion monitoring (SIM) mode. Compound separation was achieved using a 30 m × 0.25 mm inner diameter × 0.25 μm film thickness Equity-5 column. Oven temperature began at 50 °C, held for 1.1 min, increased to 125 °C at 25 °C/min, increased again to 260 °C at 8 °C/min, and finally increased to 300 °C at 3 °C/min and was held for 5 min. The injector temperature was 300 °C and the injection volume was 1 μL with splitless injection mode. Helium was used as the carrier gas and the flow rate was set at 1.2 mL/min. The detector interface was set at 200 °C. The mass spectrometry (MS) conditions were SIM mode, an ionization energy of 70 eV, and an ion source temperature of 200 °C. Data were collected using the Varian Chem-Station software 6.

Quality Control

All sampling and analysis in the UCAMPP program was subject to a rigorous quality assurance (QA) and quality control (QC) plan as described elsewhere.7 The QA/QC included internal standards, surrogate standard spikes, field blanks, duplicates, and daily standardization of instruments.

The method precision was evaluated by the average of percent absolute difference between regular field samples and duplicate samples (5% of valid regular samples). The overall precision of all of the PAHs was 29.9 ± 11.2% (n = 10). The recovery of the surrogates was 84 ± 45.8% for d₈-Nap, 86.7 ± 28.3% for d₁₀-Phen, 101.9 ± 40.9% for d₁₀-Py, and 100.3 ± 47.2% for d₁₂-BaP. Samples with average recovery less than 30%, which was less than 10% of the total sample, were excluded for data analysis. The PAH concentrations were corrected with the recoveries of the surrogates.

Twelve field blanks (i.e., 6% of the valid regular samples) were collected during the whole project. The blank level of Nap was relatively high, approximately 30 ng/filter. This value is equivalent to the concentration of 1.2 ng/m³ for the sampling volume of 24 m³ used in this study. Less than 10 ng/filter (equivalent to <0.4 ng/m³ of PAHs in a sampling volume of 24 m³) of two- to four-ring PAHs were detected in the field blank. No PAHs were detected for five- to seven-ring PAHs in filter or PUF field blanks. For the low-molecular weight (MW) PAHs (≤202), the method detection limits (MDLs) were estimated as 3 times the standard deviation (SD) of all of the field blanks collected for the entire project (n = 12). For the higher MW PAHs (MW > 202), which were nondetectable in the field blanks, the MDLs were derived from the SD of the seven repeat analyses of the lowest concentration of calibration standard. The final sample concentrations presented in this paper were obtained by the measured concentration of each sample subtracted by the average concentration of all of the field blanks.

Data Analyses

The sum of PAH concentrations determined in the filter and PUF samples were summed for data analysis because one of the main goals of this study was to characterize the impact of different land-use patterns on local PAH air pollution. In addition, the gas/particle concentration was not the primary interest of this study. Because of the potential sampling artifacts associated with the filter-PUF sampling system,11–13 the concentrations measured in the PUF/filter samples may not represent the true gas/particle concentration.

For this paper, the PAHs with concentrations below the MDL were replaced with a half of the MDL before statistical analysis. Because BghiP and Indeo had more than 50% nondetects, no substitution was conducted for these two species. The total PAHs (∑PAH; i.e., the sum of the concentrations of the 16 PAHs) were also calculated for analysis. For comparison with the PAH concentrations measured in this study to other urban/suburban areas, the sum of 13 PAHs (∑13PAH, excluding Nap, Ace and Acen from the 16 PAHs) were calculated for analysis. The selected 13 PAH species were found to be available from most previous studies. Because most measurements obtained from the study are non-normal and highly skewed (Shapiro–Wilk test; P < 0.05), a nonparametric approach (Wilcoxon rank-sum test) was used to examine the differences among the study sites.

The diagnostic ratio of PAH isomers, which is commonly used for source identification,14–16 was calculated in each season for each study site to help to characterize the main emission sources of PAHs. The ratios calculated include Fluo/(Fluo+Py), BaA/Chry, Phen/(Phen+An), and BaA/BaP. In addition, the correlations among PAH species and between PAHs and other co-pollutants were used to identify their possible PAH emission sources. Significant correlations may indicate the same or similar principal emission sources.17–19 In this study, Spearman correlation analysis was conducted among individual PAHs and between ∑PAH and trace elements (copper [Cu], iron [Fe], manganese [Mn], lead [Pb], and zinc [Zn]), EC, and OC to assist in determining the potential PAH sources at each monitoring site. These co-air pollutants, which were measured simultaneously during UCAMPP at each site,7 were selected for analysis because Cu, Fe, Mn, Pb, and Zn are reported to be related to traffic sources in most urban areas20–22 and EC is often used as an indicator for diesel emission.23,24 OC can be generated from primary emission sources and secondary formation processes.25 All statistical analyses were conducted by SAS (version 9.1).

RESULTS AND DISCUSSION

Ambient PAH Concentrations

The PAH concentrations measured at the three sites (commercial, industrial, and mobile sites) in Paterson and the background site are presented in Table 2. The concentrations of most individual PAHs (except for BghiP and Indeo, which had <50% of samples above detection) were found to be significantly higher at the Paterson sites than the background site. For example, the mean concentrations of the predominant species (i.e., Nap, Flu, and Phen) were in the range of 15–38 ng/m³ at the commercial, industrial, and mobile sites, 3–5 times higher than those at the background site (5–8 ng/m³). The mean concentrations of the heavier compound species (e.g., BaA and BaP) ranged from 0.08 to 0.12 ng/m³ at the Paterson sites whereas their concentrations were lower (0.04–0.05 ng/m³) at the background site. The ∑PAH concentrations were also higher at the three Paterson sites than the background site, with average ∑PAH concentrations of 98 ± 109.8, 75.5 ± 90.3, and 95.4 ± 156.3 ng/m³ for the commercial, industrial, and mobile sites, respectively, and 23.8 ± 23.8 ng/m³ at the background site.

Table 2. Ambient PAH concentrations (ng/m³) detected at the four sampling sites

	Background (n = 54)				Commercial (n = 50)				Industrial (n = 49)				Mobile (n = 44)
Compound	Mean	SD	Min	Max	Mean	SD	Min	Max	Mean	SD	Min	Max	Mean	SD	Min	Max
Nap	8.49	11.98	0.03	62.61	38.83	47.32	0.19	215	26.88	33.61	0.82	146	33.42	46.30	1.47	275
Ace	0.77	2.03	0.01	13.53	10.37	33.12	0.13	233	7.01	19.54	0.04	116	9.68	35.98	0.17	241
Acen	1.94	3.88	0.01	25.51	3.50	4.28	0.05	21.23	3.51	4.30	0.02	17.36	3.77	7.42	0.02	48.4
Flu	6.00	8.84	0.02	45.31	20.10	49.82	0.76	335	15.24	27.84	0.04	155	15.88	42.83	0.06	288
Phen	5.16	4.76	0.02	23.41	19.21	15.58	2.98	74.34	18.36	22.08	0.11	144	27.27	42.15	0.21	243
AN	0.23	0.70	0.01	5.10	2.02	6.81	0.09	48.68	0.98	1.54	0.05	10.1	1.07	1.65	0.03	10.6
Fluo	0.56	0.36	0.01	2.01	2.37	1.61	0.48	7.00	2.16	2.13	0.09	13.31	2.71	2.76	0.11	16.11
Py	0.22	0.18	0.03	0.94	1.51	1.06	0.22	5.63	1.27	1.38	0.03	8.56	1.43	1.57	0.08	7.91
BaA	0.04	0.04	0.01	0.21	0.08	0.09	0.01	0.38	0.12	0.21	0.01	1.00	0.12	0.22	0.01	1.35
Chry	0.06	0.07	0.01	0.34	0.13	0.11	0.01	0.50	0.18	0.28	0.01	1.50	0.16	0.29	0.01	1.79
BbF	0.08	0.13	0.01	0.68	0.13	0.23	0.01	1.00	0.16	0.34	0.01	2.25	0.16	0.31	0.01	1.7
BkF	0.04	0.06	0.01	0.38	0.07	0.11	0.01	0.55	0.10	0.23	0.01	1.23	0.08	0.12	0.01	0.48
BaP	0.05	0.07	0.01	0.41	0.08	0.12	0.01	0.58	0.10	0.23	0.01	1.57	0.10	0.16	0.01	0.77
BghiP	NA	NA	ND	0.77	NA	NA	ND	0.68	NA	NA	ND	1.38	NA	NA	ND	0.99
Indeo	NA	NA	ND	0.55	NA	NA	ND	0.51	NA	NA	ND	0.99	NA	NA	ND	0.59
DiBa	0.05	0.12	0.01	0.87	0.10	0.16	0.01	0.73	0.13	0.28	0.02	1.76	0.13	0.26	0.01	1.53
Notes: NA = not applicable, ND = not detected.

The higher PAH concentrations measured at Paterson indicated that there are significant local emission sources of PAHs. As reported by NJDEP,26 there are many potential sources of PAHs in Paterson, such as industrial facilities using smelters or furnaces for metal fabrication and recovery, heavy truck traffic on local highways and main roads, and combustion from local restaurants. PAHs are known to be emitted from these combustion sources, which can result in elevated levels of PAHs in Paterson. However, the background site is located in a rural area without nearby sources of PAHs. It has served as the NJDEP air toxics background/rural site since July 2001. Therefore, PAH levels in Chester are expected to be lower than in Paterson.

The PAH concentrations measured in this study were also compared with other urban areas in New Jersey and the United States to examine whether Paterson has a higher concentration of PAHs than other similar areas around the country. As shown in Table 3, the concentration of BaP in the ambient air in Paterson areas is 0.08–0.1 ng/m³, which is higher than those found at background sites such as Chest and Sandy Hook, NJ.27 The ambient standards regarding exposure to PAHs usually refer to BaP (indicator parameter for PAH). For example, the U.K. government's Expert Panel on Air Quality Standards (EPAQS) has recommended an annual average standard of 0.25 ng/m³ for BaP in ambient air.28 Although EPA has no regulatory values for BaP in ambient air, the similar atmospheric BaP levels are accepted in the United States (annual exposure in the range 0.3–0.7 ng/m³).29 The concentrations of BaP in the Paterson community were within the accepted level. However, it is found that the concentrations of other representative PAH species and the ∑13PAH at the three Paterson sites are similar or even higher than those measured in the urban areas with mixed sources of PAH air pollution, such as Jersey City, Camden, and Elizabeth in New Jersey and Houston, TX.30–32 The comparison results suggested that Paterson is an area with PAH air pollution and there are local PAH emission sources in the Paterson area.

Table 3. PAH concentrations (gas phase + particle phase, ng m⁻³) at various locations

Site	Phen	Py	BaP	BbF + BkF	∑13PAH
Chester, NJ ^a	5.16	0.22	0.05	0.12	12.5
Commercial, Paterson, NJ ^a	19.2	1.51	0.08	0.20	45.9
Industrial, Paterson, NJ ^a	18.4	1.27	0.1	0.26	38.9
Mobile, Paterson, NJ ^a	27.3	1.43	0.1	0.24	49.2
Jersey City, NJ31	15.0	2.1	0.19	0.55	50.0
CDS, Camden, NJ32	12.4	1.23	0.21	0.41	27.8
WFS, Camden, NJ32	15.5	1.47	0.36	0.61	34.8
Houston, TX30	19.0	2.3	0.025	0.15	46.0
Elizebeth, NJ30	26.0	3.6	0.14	0.22	53.0
Sandy Hook, NJ27	4.88	0.48	0.04	0.12	8.13
Sturgeon Point, NY33	4.01	0.58	0.06	0.09	6.70
Notes: ^aThis study.

The PAH concentrations measured in the background site of this study were compared with those reported for the suburban and background areas, such as Sandy Hook, NJ, and Sturgeon Point, NY (see Table 3).27,33 As expected, the PAH concentrations observed at the background site are similar to those measured in the areas with no significant PAH sources.

Seasonal Variation

The seasonal variation of PAH concentrations differed by species. For most compounds (e.g., Nap, Ace, Chry, BaA, BaP, BbF, BkF, and DiBa) the mean concentrations were elevated significantly in winter as compared with those in summer (P < 0.05) at all four sites. However, some lighter PAHs showed higher concentrations in summer. For example, a significantly higher concentration of Phen was observed in summer than in winter within each study site (P < 0.006). The level of Fluo was also higher in summer than in winter within each study site, although the difference in summer and winter was not significant.

The seasonal pattern (i.e., most compounds had a higher concentration in winter and a few lighter compounds had a higher concentration in summer) is consistent with literature data.34 The seasonal variations are most likely related to the emission source strength and photoactivity of PAHs in different seasons.33,34 PAHs in urban areas are primarily generated by combustion sources, such as vehicle exhaust and space heating. In winter, given the low temperature, incomplete combustion and a longer heating time of the engine will result in higher emissions of PAHs when compared with summer.34 Space heating in winter is an additional source of ambient PAHs. In addition to different sources of PAHs by season, the stability of PAHs in ambient air differs significantly by season. Higher concentrations, particularly of the heavier PAHs, occur in winter than in summer because of the much lower PAH photoactivity in winter that favors PAH accumulation in ambient air. Nonetheless, PAHs, especially lighter PAHs (Phen and Fluo), can be released to the ambient air by volatilization from environmental surfaces (e.g., soil and vegetation), leading to higher concentrations of some lighter PAHs in summer.35

Land-Use Patterns and PAH Pollution Levels

PAH profiles may serve as fingerprints of a particular site.36,37 They may also be used to identify potential sources of PAHs and assess the impact of land-use patterns on PAH pollution.38–40 The PAH profiles (i.e., percent contribution of each individual PAH to the ∑PAH) at the three sites in Paterson are shown in Figure 1.

Figure 1. Profiles of the contribution for each individual PAH to ∑PAHs at the commercial/industry/mobile site: (a) lighter PAHs and (b) heavier PAHs.

In general, the distribution was dominated by low-MW species, with the largest relative contributions to ∑PAHs from Nap (∼40% of ∑PAH), followed by Flu and Phen (∼20% each) at those sites. The contribution of the lighter PAHs (Py and lighter PAHs) to ∑PAH were found to be similar among the three Paterson sites, although slight differences were observed for Nap, Flu, Phen, and An (Figure 1a). In contrast, different profiles of heavier PAHs were observed (Figure 1b). The percentage of heavier compounds was found to be significantly higher at the industrial site than those measured at the commercial/mobile sites (P < 0.05), and the percent contribution was found to be lowest at the commercial site. These findings suggested that the predominant sources of the PAHs at each site might be different.

To trace the specific sources of PAHs, the profiles of PAHs at each site were compared with the PAH finger-prints of the principal PAH sources (i.e., diesel exhaust, gasoline emissions, coal combustion, and wood combustion).40 Khalili et al.40 reported that Ace, Acen, Flu, and Phen (10.6–14.9% each) contributed largely to ∑PAHs generated by diesel exhaust. The contribution of Nap to ∑PAHs was reported to be high for coal combustion (91%) and gasoline (81%), and a high contribution of Ace (52%) was found for wood combustion. At the three Paterson sites, the percent contributions from Ace (9.2–10.5%) and Flu (16–20%) were close to the emission of diesel exhaust, suggesting that the diesel emissions might be one of the main sources contributing to the PAH concentrations in the study area. On the other hand, the percent contributions of the main components (i.e., Nap [10–55%], Ace [1–15%], Flu [12–35%], and Phen [6–55%]) did not match the fingerprints of any single source, indicating the impact of the mixed sources of PAHs in the study area. Further source identification for each site is discussed in the next section.

Diagnostic Ratios of PAHs

The diagnostic ratios of PAH isomers are good indicators of PAH emission sources in ambient air.14–16,41However, alteration of the PAH ratios because of atmospheric transformation processes needs to be considered.42 Also, because there is the limitation that PAH isomer ratios show some intrasource variability and intersource similarity, several PAH ratios were examined together to distinguish their source origin. Table 4 lists the average diagnostic ratios of PAHs at each site along with the literature values for different combustion sources.40–44 Considering stability differences of PAHs in different seasons, the ratios were calculated for each site by season. Note that BaP measured in the summer at all locations had more than 50% nondetects, so the ratio of BaA/BaP could be biased higher than the true values for the summer season.

Table 4. Ratios of ambient PAHs at different monitoring site in different seasons

Site	Season	Fluo/(Fluo + Py)	BaA/Chry	Phen/(Phen + An)	BaA/BaP ^a
Commercial	Spring	0.63	0.65	0.93	1.01
	Summer	0.66	0.44	0.97	2.15
	Fall	0.59	0.69	0.95	3.21
	Winter	0.55	0.59	0.85	1.09
Industrial	Spring	0.68	0.79	0.95	1.17
	Summer	0.67	0.75	0.94	5.48
	Fall	0.62	1	0.94	2.77
	Winter	0.58	0.63	0.86	3.59
Mobile	Spring	0.7	0.87	0.95	1.52
	Summer	0.73	0.31	0.97	1.47
	Fall	0.68	0.87	0.97	6.79
	Winter	0.59	0.59	0.9	1.02
Background	Spring	0.71	0.92	0.94	1.21
	Summer	0.76	0.93	0.96	1.35
	Fall	0.66	0.61	0.91	2.51
	Winter	0.67	0.49	0.82	1.11
Reference40–44	Diesel	0.60–0.70	0.4–0.6	0.65	1
	Gasoline	0.4	–	0.5	0.5
	Wood	–	0.79	–	1
	Oil	0.62	–	>0.70	–
	Coal/Coke	–	1.0–1.2	–	–
Notes: ^aBaP measured in the summer at all locations had >50% nondetects, so the ratio of BaA/BaP could be biased higher than the true values.

At the commercial site, the ratios of Fluo/(Fluo+Py) for all seasons were in the range of 0.55–0.63. These values are similar to those measured for diesel emissions and oil combustion. The ratios of BaA/Chry are also similar to those reported for diesel emission. However, the ratios of Phen/(Phen+An) are closer to oil combustion emission. For the ratios of BaA/BaP, the ratios in spring and winter are close to 1, which is similar to diesel and wood burning emissions. Their ratios in summer and fall are higher than 1. This may be due to the faster degradation rate of BaP than BaA in addition to a potential difference in source by season. On the basis of these analyses, it can be concluded that the major sources of PAHs in the commercial area are diesel exhaust and oil combustion. These results are consistent with the authors' observations and the NJDEP inventory data. Truck traffic passing through the commercial area was observed during sampling. Also, there are many restaurants located near the sampling site. Thus, oil combustion and food preparation in local restaurants can contribute to ambient PAHs at the commercial site.

At the industrial site, the ratios of Fluo/(Fluo+Py) in all seasons were in the range of 0.58 – 0.68, matching well with the diesel exhaust signatures. On the other hand, the ratios of BaA/Chry and Phen/(Phen+An) are close to those for wood, coal, and oil combustion. The ratios of BaA/BaP varied largely, ranging from 1.17 to 5.48. Except the alteration of the ratio due to atmospheric reactions, the ratio in winter (3.59) differed from any values reported. These results suggest that there are mixed sources of PAHs in industrial areas, including combustion of diesel, oil, wood, coal, and other unknown combustion sources. As discussed earlier, there are approximately 50 industrial facilities operating near the industrial site.26 Factories that use smelters and furnaces for metal fabrication, refinishing, and recovery may contribute to ambient PAHs at this site.45 Further, there are many residential houses located in this area. Residents commonly use wood for fireplaces in cold seasons in New Jersey.

At the mobile site, the ratios of Fluo/(Fluo+Py) in all seasons were in the range of 0.59 – 0.73, closer to those reported for diesel exhaust. The ratio of BaA/Chry varied by season, but the winter value (0.59) was in the diesel emission range. For the ratio of BaA/BaP, they were lower than 2 in three seasons. These results indicated that diesel exhaust is the major source of PAHs in this area, with partial contribution from other combustion sources.

Regarding the background site, the diagnostic ratios were similar to those obtained from the mobile site. The results suggested that although the PAH concentrations were low, the measurable PAH concentrations at the background site might primarily result from local vehicle emissions. As a matter of fact, there are several local small roads surrounding the sampling site.

Correlations of PAHs and Other Co-Pollutants

The relationship between the concentrations of individual PAHs at each site and the correlation of the ∑PAHs among the study sites were investigated. Each study site in Paterson had moderate to strong positive correlations (r = 0.6 – 0.94, P < 0.05) that were found for most individual PAHs during the seasons of spring, fall, and winter. Also, significant correlations (r = 0.6 – 0.83, P < 0.05) were found for the ∑PAHs among the three Paterson sites during those seasons. These results indicated the presence of a predominant emission source that is most likely diesel emissions at all study sites as indicated by the diagnostic ratio analysis. The lack of correlations of PAH species in summer might result from the complicated photochemical reactions of PAH species.34 As discussed above, the photoreactivity of PAHs differs by species. Some undergo faster photo-degradation in ambient air, whereas some are relatively more stable. Therefore, the concentrations of PAH species after being emitted may be altered, which resulted in poor correlations in summer.

In the case of the background site, no significant correlations were found for individual PAHs during most seasons except winter, indicating that there are no predominant sources in this area. The significant correlations in the winter might also suggest the presence of a predominant emission source just in winter. In addition, significant correlations of the winter ∑PAHs were observed between the background and the commercial and mobile sites. These results further suggested that diesel-powered vehicular emissions might be primarily responsible for PAH pollution at the background site during the winter.

Table 5 lists the Spearman correlation coefficients of ∑PAH concentrations with elements, EC, and OC in different seasons for the four sites. At the commercial site, the ∑PAHs correlated strongly with EC, OC, and the five elements in most scenarios, except Mn, Pb, and OC in the summer and Mn in the winter. As introduced early, the five elements were selected because they are often related to traffic air pollution in urban areas. These results confirm that there were dominant sources of PAHs, likely diesel emissions and oil combustion, in the commercial area in all seasons. At the industrial site, those correlations were only found to be signifi-cant in the spring. At the mobile site, significant correlations of ∑PAHs and the co-pollutants were found in spring and winter. These observations indicated that there is more than one emission source of PAHs and that the major sources of PAHs varied by season in those areas.

Table 5. Spearman correlation coefficients between ∑PAHs and elements, EC, and OC in different seasons and monitoring sites

Site	Season	Cu	Mn	Zn	Pb	Fe	EC	OC
Commercial	Spring	0.767 ^a	0.750 ^a	0.750 ^a	0.733 ^a	0.750 ^a	0.733 ^a	0.700 ^a
	Summer	0.560 ^a	0.484	0.753 ^a	0.429	0.588 ^a	0.544 ^a	0.522
	Fall	0.771 ^a	0.718 ^a	0.600 ^a	0.564 ^a	0.739 ^a	0.679 ^a	0.611 ^a
	Winter	0.773 ^a	0.464	0.755 ^a	0.782 ^a	0.827 ^a	0.736 ^a	0.682 ^a
Industrial	Spring	0.867 ^a	0.867 ^a	0.883 ^a	0.883 ^a	0.950 ^a	0.893 ^a	0.857 ^a
	Summer	0.407	0.288	0.327	0.244	0.556 ^a	0.222	0.345
	Fall	0.350	0.379	0.229	−0.175	0.450	0.354	0.235
	Winter	0.381	0.595	0.405	0.381	0.476	0.233	0.083
Mobile	Spring	0.952 ^a	0.929 ^a	0.976 ^a	0.690 ^a	0.976 ^a	0.905 ^a	0.976 ^a
	Summer	0.190	−0.452	−0.048	0.000	−0.357	0.095	0.095
	Fall	0.244	0.323	0.059	0.165	0.292	0.240	0.138
	Winter	0.773 ^a	0.764 ^a	0.782 ^a	0.709 ^a	0.736 ^a	0.718 ^a	0.718 ^a
Background	Spring	0.164	−0.042	0.442	0.042	0.261	0.491	0.127
	Summer	0.248	0.073	0.125	−0.033	0.253	0.204	0.147
	Fall	0.632 ^a	0.441	0.688 ^a	0.538 ^a	0.518 ^a	0.638 ^a	0.168
	Winter	0.600 ^a	0.627 ^a	0.509	0.073	0.436	0.745 ^a	0.673 ^a
Notes: ^aSignificant at the 0.05 level.

As expected, there were no consistent significant correlations between PAHs and other species in any season at the background site. Also, the correlation coefficients were low (<0.5) in most cases. These findings confirmed that there were no significant PAH sources in the background area.

CONCLUSIONS

The concentrations of PAHs were found to be significantly higher at the three Paterson sites in comparison with the background site in Chester, NJ, and were comparable to other urban areas with mixed sources of PAHs in New Jersey and the United States. Also, a clear seasonal pattern was observed, with higher concentrations of most PAHs in winter. Only a few light PAHs had higher concentrations in summer at all study sites. Different PAH profiles were observed at different Paterson sites, indicating the impact from different land-use patterns on PAH levels in different areas.

Source identification was performed by comparing the PAH fingerprints of the principal PAH sources; analyzing diagnostic ratios of PAH isomers; and examining the correlation of individual PAHs within each study site, intercorrelations of ∑PAH concentrations among the study sites, and the correlation of the ∑PAH concentrations with trace elements, EC, and OC. Taking the results of all of these different analyses into consideration, it can be concluded that diesel emissions and oil combustion were the dominant PAH sources at the commercial site. At the industrial site, diesel emissions and combustion of oil, coal, and other fossil fuels during industrial operations and space heating contributed to PAH pollution. At the mobile site, in addition to diesel exhaust, other additional combustion sources also contributed partly to PAH levels. No significant PAH sources were found in the Chester background area.

ACKNOWLEDGMENTS

This study was supported by EPA (grant no. SR05-035). Dr. Fan is supported in part by the National Institute of Environmental Health Sciences (NIEHS)-sponsored University of Medicine and Dentistry of New Jersey Center for Environmental Exposures and Disease (grant no. NIEHS P30ES005022). The authors thank Drs. Qingyu Meng, Robert Stiles, Kathy Black, and Ms. Martha Hernandez for help with field sampling. The views expressed in this article are those of the authors and do not necessarily reflect the views or policies of the funding agency.