Polycyclic Aromatic Hydrocarbons in the New Jersey Coastal

as part of the New Jersey Atmospheric Deposition. Network (NJADN). PAH results from the first year of atmospheric sampling (Oct 1997-Oct 1998) at a su...
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Environ. Sci. Technol. 2000, 34, 3547-3554

Polycyclic Aromatic Hydrocarbons in the New Jersey Coastal Atmosphere CARI L. GIGLIOTTI, JORDI DACHS, ERIC D. NELSON, PAUL A. BRUNCIAK, AND STEVEN J. EISENREICH* Department of Environmental Sciences, Rutgers University, 14 College Farm Road, New Brunswick, New Jersey 08901-8551

Concentrations of polycyclic aromatic hydrocarbons (PAHs) were measured in the coastal New Jersey atmosphere as part of the New Jersey Atmospheric Deposition Network (NJADN). PAH results from the first year of atmospheric sampling (Oct 1997-Oct 1998) at a suburban site near New Brunswick, NJ and a coastal site at Sandy Hook, NJ are presented. PAHs (36) were analyzed at both sites including phenanthrene and benzo[a]pyrene whose concentrations ranged from 0.74 to 20.9 ng/m3 and 0.0020 to 0.62 ng/m3, respectively. PAH concentrations at the suburban site were 2× higher than concentrations measured at the coastal site, consistent with the closer proximity of NB to urban/industrial regions than SH. The seasonal trends of particulate PAH concentrations indicate that PAH sources such as fuel consumption for domestic heating and vehicular traffic drive their seasonal occurrence. While gaseous concentrations of methylated phenanthrenes and pyrene were higher during the winter and similar to high molecular weight PAHs, phenanthrene and fluoranthene show the opposite seasonal trend with concentrations peaking in the summer months. Because temperature accounted for less than 25% of the variability in atmospheric concentrations, seasonal variability could not be attributed to temperature-controlled air-surface exchange. PAH concentrations in the New Jersey coastal atmosphere indicate the importance of local and regional sources originating from urban/industrial areas to the N, NE, and to the SW.

Introduction Polycyclic aromatic hydrocarbons (PAHs) are ubiquitous compounds containing two to eight rings that arise from the incomplete combustion of fossil fuels and wood. Forest fires and volcanoes contribute to the PAH burden, but by far, anthropogenic sources are responsible for the majority of the PAH input to the atmosphere, which in turn contributes to depositional loadings to aquatic and terrestrial systems (1-6). The largest anthropogenic sources of PAHs are vehicular emissions from both gasoline and diesel powered vehicles, coal and oil combustion, petroleum refining, natural gas consumption, and municipal and industrial incinerators (7, 8). Once they enter the atmosphere, PAHs redistribute between the gas and particle phases (9-11) and are subject to removal mechanisms such as oxidative and photolytic reactions and wet and dry deposition (3, 7, 12-14). * Corresponding author phone: (732)932-9588; fax: (732)932-3562; e-mail: [email protected]. 10.1021/es9912372 CCC: $19.00 Published on Web 07/26/2000

 2000 American Chemical Society

The carcinogenic nature of PAHs in conjunction with their continual and widespread atmospheric emission has led to intense study of these compounds particularly in urban and/ or industrial areas (1-3, 5-7, 15, 16). Because the NY/NJ metropolitan area lacks a comprehensive database for PAH concentrations as well as other hazardous air pollutants (HAPs), the New Jersey Atmospheric Deposition Network (NJADN) was founded in 1997. NJADN was established to quantify the occurrence and fluxes of PAHs and other HAPs to the lower Hudson River Estuary and to apportion source contributions where possible. The objectives of this paper are (1) to assess the spatial and temporal variability of PAH concentrations in the New Jersey coastal atmosphere as part of NJADN and (2) to study the influence of environmental parameters such as temperature and air mass movement on PAH concentrations in the New Jersey coastal atmosphere of the Mid-Atlantic region.

Methodology Sampling and Site Characterization. Air samples were collected at New Brunswick, NJ (40.48°N/74.43°W) beginning October 1997 and at Sandy Hook, NJ (40.46°N/74.00°W) beginning February 1998 (Figure 1). New Brunswick is a suburban site in close proximity to major traffic arteries including the New Jersey Turnpike and the Garden State Parkway. Sandy Hook is located at the tip of a peninsula extending into the Lower Hudson River Estuary/Atlantic Ocean approximately 10 km south of New York City and 30 km southeast of the Newark/Jersey City urban/industrial complex. Sampling occurred for 24 h every sixth day from October 1997 to August 1998 (77 samples) and every ninth day thereafter (8 samples). At each site, Modified General Metal Works Hi-volume air samplers operated at a calibrated airflow rate of ∼500 L/min. The particulate phase was captured on precombusted (20.3 × 25.4 cm) quartz fiber filters (QFF), and the gas phase was captured on 10 cm medium-density polyurethane foam (PUF). Sample Processing. Prior to sampling, the PUFs were hand-washed with Alconox detergent and rinsed with Milli-Q water followed by acetone. The prewashed PUFs were extracted in Soxhlet units for 24 h in acetone followed by 24 h in petroleum ether after which they were placed into vacuum desiccators for approximately 48 h to evaporate any residual solvent. The PUFs were then transferred to precleaned glass jars covered with aluminum foil, sealed, and stored at 4 °C until sampling. The QFFs were individually wrapped in aluminum foil and precombusted at 450 °C for 6 h. The QFFs were preweighed in a temperature and humidity controlled room, wrapped securely in aluminum foil envelopes, and stored in plastic bags at 4 °C until sampling. After sampling, the QFFs were folded and sealed in aluminum foil envelopes until weighing for determination of total suspended particulate mass (TSP). All samples were spiked with 100 µL of surrogate standard containing anthracene-d10, fluoranthene-d10, and benzo[e]pyrene-d12 and extracted in Soxhlet apparati for 24 h, the PUFs in petroleum ether and the QFFs in dichloromethane. The sample extracts were concentrated by rotary evaporation (Bu ¨ chi Model RotoEvaporator111) to ∼2 mL, and the solvent was exchanged to hexane. Further concentration to ∼0.5 mL was carried out under a gentle stream of purified N2. Extracts were fractionated on 10 mL glass columns containing 4 g of 3% water deactivated alumina (Neutral Alumina, Brockman Activity I, A950-500, 60-325 mesh: VOL. 34, NO. 17, 2000 / ENVIRONMENTAL SCIENCE & TECHNOLOGY

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FIGURE 1. Locations of New Jersey atmospheric deposition network sites in the New Jersey coastal atmospheresshaded regions indicate urban areas based upon population density. Map adapted from the USGS Web Atlas.

FIGURE 2. Site comparison of annual average gas and particulate PAH concentrations at the New Brunswick and Sandy Hook sampling sites: ** coelutes with triphenylene. Fischer Scientific). Fraction 1, containing polychlorinated biphenyls (PCBs) and some chlorinated pesticides, was eluted with 13 mL of hexane (HEX). Fraction 2, containing PAHs and some chlorinated pesticides, was eluted with 15 mL of 2:1 dichloromethane-hexane (DCM-HEX). Fraction 2 was reduced in volume to ∼0.5 mL under purified N2 gas and spiked with 100 µL of internal standard consisting of phenanthrene-d10, pyrene-d10, and benzo[a]pyrene-d12. The PAHs were analyzed on a Hewlett-Packard 6890 gas chromatograph (GC) coupled to a Hewlett-Packard 5973 mass selective detector (MSD) operated in selective ion monitoring (SIM) mode. The column used was a 30 m × 0.25 mm i.d., J&W Scientific 122-5062 DB-5 (5% diphenyl-dimethylpolysiloxane) capillary column with a film thickness of 0.25 µm. Helium was used as the carrier gas and was regulated using a ramped flow rate program. The initial flow rate of 1.2 mL/ min was held for 20 min, then decreased to 0.3 mL/min, held 3548

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for 10.5 min, and increased again to 2.1 mL/min for the remainder of the run. The injection volume was 1.0 µL and was a pulsed splitless injection. The temperature program began at 50 °C, held for 1.10 min, increased to 125 °C at 25 °C/min, increased again to 260 °C at 8 °C/min, finally increased to 300 °C at 5 °C/min, and was held for 14 min. The identity and subsequent retention time of each PAH was confirmed by the use of a calibration standard which contained known concentrations of the surrogate compounds, internal standard compounds, and all of the PAH compounds of interest in this study. Samples were quantified by isotopic dilution and corrected for surrogate recoveries. Quality Assurance/Quality Control of the Method. Quality assurance and the quality control were determined using laboratory blanks, field blanks, split PUFs, and matrix spikes. All sample and field blank masses were corrected for laboratory contamination by subtraction of the laboratory

FIGURE 3. Seasonal distribution patterns of the 36 PAHs analyzed reported as the relative contribution of the individual PAH compound to total gas-phase and total particulate phase PAHs. used to determine PAH detection limits, were QFFs and PUFs placed into the samplers with air flowing for 1-3 min during calibration of the sampler. The method detection limits, defined as three times the standard deviation of the mass in the matrix-specific and site-specific field blank, were as follows: 0.00002 (perylene) to 0.034 ng/m3 (indeno[1,2,3cd]pyrene) for gas-phase PUFs at New Brunswick (n ) 7) and 0.0001 (indeno[1,2,3-cd]pyrene) to 0.017 ng/m3 (phenanthrene) for Sandy Hook (n ) 5). Individual QFF method detection limits ranged from 0.0001 (naphthacene) to 0.039 ng/m3 (fluorene) for New Brunswick (n ) 8) and from 0.001 (naphthacene) to 0.090 ng/m3 (fluoranthene) for Sandy Hook (n ) 5). Average QFF field blank masses accounted for 1.5% and 3.8% of the total sample masses for New Brunswick and Sandy Hook, respectively. Average PUF field blank masses accounted for 0.17% and 3.3% of the total sample masses. Split PUFs were used to quantify potential breakthrough of gas-phase PAHs into the second half of the PUF. The second half of the split PUF accounted for 12 ( 5% (n ) 3) of the total mass collected on the whole PUF with the greatest breakthrough by the lower molecular weight PAHs: fluorene (21%), 1-methylfluorene (25%), phenanthrene (33%), and methylphenanthrenes (30%). Surrogate recoveries were 79 ( 19% for anthracene-d10, 92 ( 18% for fluoranthene-d10, and 96 ( 17% for benzo[e]pyrene-d10.

Results and Discussion

FIGURE 4. The log of PAH concentration as a function of inverse temperature for phenanthrene and methylphenanthrenes. All data points above or below 1 SD of the least squares regression line are identified by triangles and squares, respectively. blank mass. PAH masses in the laboratory blanks were low relative to the masses in the samples. The laboratory blanks accounted for approximately 0.11% and 0.47% of the total PAH mass in PUF and QFF samples, respectively. Field blanks,

Occurrence and Temporal Trends. Annual average PAH measurements (total-PAHs) are defined as the sum of the concentrations of 36 PAHs. Figure 2 shows that the suburban New Brunswick total gas-phase PAH concentrations ranged from 3.5 to 84 ng/m3 and were on average 2.4 times higher than the values at coastal Sandy Hook which ranged from 2.8 to 42 ng/m3. Total particulate phase PAH concentrations were on average 2.5 times higher at New Brunswick where concentrations ranged from 0.38 to 11.6 ng/m3 than at Sandy Hook where total particulate PAH concentrations ranged from 0.15 to 4.0 ng/m3. Sandy Hook is less impacted than the New Brunswick site by PAHs due to its location on a peninsula away from the immediate impact of heavy traffic arteries, industry, or urbanization as seen at the New Brunswick site. VOL. 34, NO. 17, 2000 / ENVIRONMENTAL SCIENCE & TECHNOLOGY

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TABLE 1. Site Comparisons for Select Gas and Particulate PAH Concentration Dataa phenanthrene (ng/m3) site location

ref

New Brunswick, this NJ study Sandy Hook, NJ this study Eagle Harbor, (3 ) MIb Sturgeon Point, (3) NYb Wye, MD (17) Elms, MD (17) Haven Beach, VA (17) Chicago, IL (1) Lake Michigan (1) Baltimore, MD (19) Chesapeake Bay (19) a

gas

benzo[b+k]fluoranthene (ng/m3)

pyrene (ng/m3)

part

gas

part

0.69(0.46) 0.14(0.12)

gas 0.012(0.012)

part

8.9(4.6)

0.16(0.16)

0.32(0.30)

4.8(3.3)

0.083(0.052) 0.41(0.28) 0.070(0.052) 0.0027(0.0019) 0.12(0.12)

benzo[a]pyrene (ng/m3) gas 0.037(0.064)

part 0.088(0.096)

0.0023(0.00087) 0.033(0.035)

0.86(0.12) 0.019(0.069) 0.19(0.17) 0.022(0.016) 0.019(0.034)

0.022(0.016) 0.0093(0.023)

0.011(0.047)

4.0(0.068) 0.0060(0.077) 0.51(0.10) 0.074(0.071) 0.019(0.034)

0.074(0.071) 0.013(0.062)

0.044(0.076)

3.0(1.5) 3.7(3.2) 2.9(3.3) 64(46) 9.9(9.6) 13(11) 5.6(4.3)

0.18(0.29) 0.25(0.41) 0.11(0.16) 6.6(2.4) 0.59(0.74) 0.16(0.071) 0.085(0.054)

0.056(0.099) 0.069(0.12) 0.032(0.072) 3.0(5.9) 0.13(0.14) 0.071(0.041) 0.019(0.015)

0.061(0.062) 0.075(0.078) 0.041(0.031) 3.7(7.4) 0.14(0.15) 0.089(0.034) 0.051(0.057)

All concentration data reported as mean (SD).

b

0.64(0.78) 0.58(0.60) 1.2(1.4) 9.0(8.4) 1.6(1.8) 2.1(1.3) 0.55(0.46)

0.063(0.064) 0.070(0.077) 0.039(0.033) 5.9(11) 0.21(0.17) 0.14(0.070) 0.067(0.14)

0.0044(0.0036) 0.10(0.38) 0.0086(0.013) 0.29(0.38) 0.12(0.23) 0.0011(0.0029) NDc

0.00050(0.00029) 0.0024(0.084) 0.0044(0.0062) 0.080(0.082) 0.014(0.030) 0.00015(0.00055) NDc

Only benzo[k]fluoranthene is reported, not benzo[b+k]fluoranthene. c ND ) nondetectable.

FIGURE 5. Time series of PAH concentrations at New brunswick and Sandy Hook over 1 year. Bars are PAH concentrations; the dotted-line represents the average temperature over the sampling period for the data presented. Gas and particulate phase PAH data from NJADN are compared with data from other recent studies in Table 1. PAH concentrations at Sandy Hook are 2-10 times those reported at a remote site located at Eagle Harbor on Lake Superior for the Integrated Atmospheric Deposition Network (IADN), indicating that Sandy Hook should not be classified as a rural or remote site (3). PAH concentrations at Sandy Hook are comparable to those measured at the IADN Sturgeon Point (NY) site located on the eastern shore of Lake Erie ∼80 km from Buffalo, NY and Erie, PA (3). Similarly, Sandy Hook is influenced by emissions from local sources: New York City to the north, the New Jersey urban/industrial complex to the northwest, and the heavily populated New Jersey coast to the west, south, and southwest. Sandy Hook 3550

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is impacted by a mixture of PAH loadings from these areas, diluted by marine air and depositional losses during atmospheric transport. PAH concentrations measured during the Chesapeake Bay Atmospheric Deposition Study (CBADS) at Wye and Elms, MD and Haven Beach, VA were similar to Sandy Hook (17). The Wye site is located 45 km southeast of Baltimore, generally downwind of the Washington, DC/Baltimore Corridor. The Elms site is within 5 km of a naval air station and a coal-fired power plant. The Haven Beach site is located approximately 100 km east of Richmond, VA. Gas-phase phenanthrene and pyrene concentrations at the New Brunswick site were not statistically different from those measured during two of the AEOLOS (Atmospheric

FIGURE 6. Two-site comparison of particulate phase PAH concentrations normalized by total suspended particulate (TSP) concentration as a function of temperature. Exchange Over Lakes and Oceans) campaigns, one on Lake Michigan near urban Chicago, IL and industrial Gary, IN (1) and the other in Chesapeake Bay near Baltimore, MD (6, 18, 19). The New Brunswick, Chesapeake Bay, and Lake Michigan sites are considered “impacted” due to their location within or in close proximity to large urban/industrial source regions and observed concentrations. Air samples taken in Chicago, IL exhibited PAH concentrations significantly higher than those measured at New Brunswick (1). The seasonal distributions of gas and particulate phase PAHs at New Brunswick are presented in Figure 3. The gasphase distribution for all seasons was dominated by low molecular weight species with the largest relative contributions to total-PAHs from phenanthrene and the methylated phenanthrenes followed by fluorene and fluoranthene. The most apparent difference between the summer and winter distributions was the relative contributions of phenanthrene and the methylated phenanthrenes to total-PAHs. In the winter there was a larger relative contribution to total-PAHs by methylated phenanthrenes (46% of total-PAHs) than by phenanthrene (26%). In contrast, the opposite is true in the summer, with a higher relative contribution to total-PAHs by phenanthrene (44%) than by methylated phenanthrenes (21%), indicating different dominant sources in each season. Gas-phase fluoranthene and phenanthrene concentrations were found to be higher in the summer months, similar to other studies (1, 20). Gas-phase pyrene concentrations behaved similarly to the methylated phenanthrenes with the winter season having the highest concentrations, although other studies have reported pyrene concentrations to be highest during the summer (1, 20). Particulate phase PAH concentrations at New Brunswick are often more than an order of magnitude lower than the

gas-phase concentrations. The seasonal profiles show that particle-bound PAH concentrations are generally higher in the winter than in any other season. The winter particulate phase PAH distribution is dominated by high molecular weight compounds typically associated with atmospheric soot particles of combustion origin (21-23). Contributing to higher wintertime concentrations are lower atmospheric mixing heights, lower temperatures, and decreased photolytic oxidation. Previous studies have also suggested that increased fossil fuel usage causes elevated particulate PAH concentrations in the winter (24-26). The influence of temperature was examined to determine if increased particulate PAH concentrations during the winter is a function of emissions rather than purely enhanced partitioning from the gas to the particulate phase at lower temperatures. Temperature Dependence. The importance of temperature on atmospheric PAH concentrations was assessed by examining the log [PAH]gas, ng/m3, versus inverse temperature (1/T), K-1

log [SOC]gas ) a +

m T

(1)

where a and m are the intercept and slope obtained by a least squares linear regression. This technique has been applied to polychlorinated biphenyls (PCBs), hexachlorocyclohexanes (HCHs), and other HAPs (10, 27-29). The relationships of log [PAH]gas versus 1/T for this study are plotted in Figure 4 for phenanthrene (PHEN) and methylated phenanthrenes (MePHENs). The difference in sign of the slope of the regression line (m) demonstrates that the way in which the two compounds vary with temperature is quite different. The plot of log [PHEN]gas versus 1/T has VOL. 34, NO. 17, 2000 / ENVIRONMENTAL SCIENCE & TECHNOLOGY

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FIGURE 7. Back trajectory analysis plots A (SW air mass origin) and B (N, NE) show the directions which led to the highest PAH concentrations. Plots C (NW) and D (W) show the directions which led to the lowest PAH concentrations. All back trajectory plots were obtained from http://www.arl.noaa.gov/ready/hysplit4.html. a significant negative slope (m ) -815, p < 0.005), demonstrating that concentrations decrease with decreasing temperatures. Methylated phenanthrenes, in contrast, have a significant positive slope (m ) 1288, p < 0.001), and thus concentrations increase with decreasing temperature. The seasonal difference in the direction of the slope between methylated phenanthrenes and phenanthrene suggests that the relative contribution of sources to these two compounds is different and varies with season. Temperature accounts for 10% (p < 0.005) and 16% (p < 0.001) of the variability in phenanthrene and methylated phenanthrenes concentrations, respectively, at the New Brunswick site. At Sandy Hook, temperature accounts for 10% (p ) 0.025) and 1% (p ) 0.57, not significant) of the variability for phenanthrene and methylated phenanthrenes, respectively. Because the slopes of log [SOC]gas vs 1/T vary between positive and negative values for different PAHs, there is not a clear seasonal trend of increasing concentrations with increasing temperatures that applies universally to all PAHs. This indicates that gas-phase PAH concentrations are not driven by air-surface exchange as are PCBs whose slopes are consistently negative (29-31). Although the slopes for the majority of gas-phase PAHs at Sandy Hook are negative suggesting an influence on PAH concentrations by air-water or air-terrestrial exchange, the low correlations with temperature for both sites shows that temperature explains less than 25% (range: r 2 ) 0.001 (benzo[a]fluorene) to 0.24 (dibenzothiophene)) of the variability in gas-phase concentrations. Concentrations of PAHs are determined to a greater extent by the emissions from combustion-related activities than by air-surface exchange (19, 29). To better elucidate source-related seasonal differences, the time series of air concentrations are presented for four PAHs (gas + particulate phase): phenanthrene (PHEN), 3552

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methylated phenanthrenes (MePHENs), benzo[b+k]fluoranthene (B[bk]FLANT), and benzo[a]pyrene (B[a]P) at the New Brunswick site (Figure 5). The latter two PAHs are predominately found in the particulate phase and as such are normalized in Figure 5 by total suspended particulate (TSP) to eliminate the effect of particle mass (11, 22, 32). TSP concentrations averaged 39 ( 19 µg/m3 (range: 1.8-88) and 51 ( 28 µg/m3 (range: 11-220) at the New Brunswick and Sandy Hook sites, respectively. During the summer, methylated phenanthrenes concentrations decrease with increasing temperature, and unlike phenanthrene, the majority of the days with high methylated phenathrenes concentrations occurred during the coldest days of the year. Because the rates of oxidative and photolytic reaction of phenanthrene and methylated phenanthrenes are not appreciably different (23), changes in sources must account for this opposing seasonal trend between the two species rather than atmospheric transformations. Seasonal data from over-water samples taken on the Chesapeake Bay were compared to data from New Brunswick to determine if a similar increase in methylated phenanthrenes occurred in the winter in Chesapeake Bay (18). In the Chesapeake Bay and New Brunswick, the ratios of the concentrations of methylated compounds to their parent homologues were higher in the winter than in the summer. The ratios of MePHENs/PHEN and MeDBTs/DBT are 2.1 and 1.9, respectively, for Chesapeake Bay in the winter. The ratios of MePHENs/PHEN and MeDBTs/DBT for the New Brunswick site are 1.9 and 1.0, respectively, in the winter. In contrast, the ratios drop to 0.99 and 1.1 in the summer for Chesapeake Bay and 0.5 and 0.48 for New Brunswick. The increase in the concentrations of methylated compounds relative to their parent homologues is indicative of uncombusted fuel hydrocarbons and fossil fuel residues (23, 33).

The increased fossil fuel demand and subsequent consumption for home heating in the cold winter months likely accounts for the elevated relative contribution of methylated PAH concentration to total-PAH concentration seen in the Baltimore/Chesapeake Bay and New Jersey coastal atmosphere. The increase in methylated compounds in the winter follows a temporal trend similar to that for high molecular weight PAHs suggests that the source(s) of methylated and high molecular weight particulate PAHs are the same. Figure 5 demonstrates how the concentrations of two PAHs enriched in the particulate phase (B[bk]FLANT and B[a]P) increase with colder temperatures at the New Brunswick site. To assess if this trend applies to other high molecular weight particulate species, Figure 6 depicts the concentrations of four particulate PAHs normalized by TSP ([SOC]part/TSP) for phenanthrene, methylated phenanthrenes, benzo[b+k]fluoranthene, and benzo[a]pyrene versus temperature. For days with temperatures >10 °C at the New Brunswick site, there is little variability in particulate PAH concentrations. When temperatures drop below ∼10 °C at the NB site, a statistically significant (p < 0.001) increase in the PAH concentrations occurs. During low temperature periods, increased fossil fuel consumption for home heating is the likely major contribution source to this winter particulate PAH burden and may account for the increase in the number of high concentration days observed in the winter months. The observed winter increase in particulate PAH concentrations is consistent with observations in other urban areas (24, 25, 34). At Sandy Hook, there is increased variability in PAH concentrations during colder temperatures for benzo[b+k]fluoranthene/TSP and phenanthrene/TSP concentrations, though not for methylated phenanthrenes/TSP and benzo[a]pyrene/TSP concentrations. The proposed “winter influence” at New Brunswick by home heating is not observed to the same extent at Sandy Hook. This can likely be accounted for by dilution of the PAH signal due to dispersion/ mixing and depositional losses during transport. On 4 days at Sandy Hook, the benzo[b+k]fluoranthene/TSP and phenanthrene/TSP concentrations cause the data to resemble the New Brunswick trend. On those days, local winds came directly from the heavily populated New York City and Long Island area located to the N, NE of Sandy Hook. Influence of Large-Scale Air Mass Movement. Because the log [SOC]gas ) a + m/T relationship does not take into account all of the variables that determine SOC concentration, the variability in PAH concentration that is not explained by temperature may be attributed to emissions from local or regional source areas. To determine which source vectors influence PAH concentrations in New Jersey’s coastal atmosphere, back trajectory analyses were performed (35). Figure 4 reveals that temperature accounted for only a small portion of the variability in PAH concentrations (r 2 ) 10%: PHEN; r 2 ) 16%: MePHENs). We focused on those days with observed gaseous PAH concentrations that significantly deviated from the predicted concentrations based upon the partitioning model for air/surface exchange. A number of “outliers” were identified as occurring (1 SD from the least squares regression line of the equilibrium model in eq 1. Subhash et al. (35) found that back trajectory analysis of similar “outlier” days with extreme high or low concentrations lead to a determination of important transport vectors. In a similar manner, all data points with relative standard residuals (log [PAH]observed - log [PAH]predicted by eq 1)/ σ greater than 1 or less than -1 were considered “outliers”. Back trajectories were available for 16 out of 23 days. The highest gas-phase concentrations of phenanthrene and methyl phenathrenes occurred when air masses came from the SW (12 days) and the N/NE (4 days). The heavily urban/ industrialized Interstate-95 corridor through Baltimore, MD,

Wilmington, DE, Philadelphia, PA, and Camden, NJ is located to the SW of the New Brunswick site. Air masses from the N/NE of New Brunswick derive from New York City and the central NJ urban/industrial complex (see Figure 7). On three of the days with wind speeds less than 2 m/s, the back trajectories show that the air masses came from the N/NE. The high PAH concentrations measured at New Brunswick resulted from minimal dilution at low wind speeds. The results suggest that the New Brunswick site is impacted by local urban/industrial areas to the NE and to the SW. New Brunswick may also be subject to longer-range transport from the urban/industrial areas along the Interstate-95 corridor. Although the back trajectories target specific vectors leading to high or low concentrations, it should not be inferred that every day that the back trajectories derive from a specific vector will correspond to high or low concentrations since PAH concentrations are strongly influenced by anthropogenic activities. With the back trajectory data available for 8 of 14 days, the lowest PAH concentrations at New Brunswick occurred when the back trajectories showed the air masses came from the NW (7 days) and the W (1 day) (Figure 7). Less densely populated areas may account for the lower concentrations observed when trajectories came from the NW and W of New Brunswick.

Acknowledgments The authors wish to express our sincere appreciation to T. Glenn IV, D. Van Ry, and R. Pelleriti for laboratory and field assistance. This research is a result of work funded in part by Rutgers University, the Hudson River Foundation under Grant # 004/99A (Project Officer, D. Suszkowski), the NOAA Office of Sea Grant and Extramural Programs, U.S. Department of Commerce, under Grant # NA76-RG-0091 (Project No. R/E 9704; Project Officer, M. Weinstein), and the New Jersey Agricultural Experiment Station.

Supporting Information Available Raw PAH concentration data for the first year of atmospheric sampling at two sites in New Jersey as part of the New Jersey Atmospheric Deposition Network (NJADN). Section I, New Brunswick PAH raw concentration data; Part A, gas-phase PAH concentration data (ng m-3); Part B, particle phase PAH concentration data (ng m-3). Section II, Sandy Hook PAH raw concentration data; Part A, gas-phase PAH concentration data (ng m-3); Part B, particle phase PAH concentration data (ng m-3). This material is available free of charge via the Internet at http://pubs.acs.org.

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Received for review November 3, 1999. Revised manuscript received March 22, 2000. Accepted May 4, 2000. ES9912372