The eVect of wind direction on the observed size distribution of particle adsorbed polycyclic aromatic hydrocarbons on an inner city sampling site† Ju�rgen Schnelle-Kreis,*ab Thomas Ja�nsch,b Kathrin Wolf,a Istvan Gebefu�gia and Antonius Kettrupab aGSF—National Research Center for Environment and Health, Institute of Ecological Chemistry, Ingolsta�dter Landstrasse 1, D-85758 Neuherberg, Germany.E-mail: jurgen.schnelle@gsf.de bDepartment of Ecological Chemistry and Environmental Analytical Chemistry, Technical University Munich, D-85358 Freising, Germany Received 23rd February 1999, Accepted 13th May 1999 An investigation of the variability in the size distribution of particle adsorbed polycyclic aromatic hydrocarbons (PAHs) on an inner city sampling site showed diVerences depending on the wind direction.Particle size distributions of PAHs from outdoor air sampling were measured in Munich from 1994 to 1997. The sampling site is located northeast of a crossing with heavy traYc and southwest of a large inner city park. Depending on the wind direction, three diVerent size distributions of particle adsorbed PAHs were observed. The maximum PAH concentration on very small particles (geometric mean diameter 75 nm) was observed with wind from west to southwest coming directly from the crossing area or the roads with heavy traYc.The maximum PAH concentration on particles with geometric mean diameter of 260 nm was found on days with wind from the built-up area north of the sampling site. On particles with geometric mean diameter of 920 nm the maximum PAH concentration was found on days with main wind directions from northeast to east.On these days the wind is blowing from the direction of the city park nearby. The distribution of particle adsorbed PAHs within diVerent particle size classes is substantially influenced by the distance of the sampling site from strong sources of PAH loaded particulate matter.break between mechanically generated particles and combus- Introduction tion particles is at a point smaller than 2.5 mm. A particle size Recent epidemiological studies have convincingly of about 1 mm is stated to represent the break in particles demonstrated associations between ambient mass concen- from diVerent sources.10 Tuch et al. investigated the variation trations of small particles and a range of indices of health.1–4 in particle number and mass concentrations in the size range The results of these studies and animal toxicology and in vitro 0.01–2.5 mm on an inner city sampling site.They suggest that experiments support the hypothesis that both physical (particle ‘particles larger than 2.5 mm (or even larger than 0.5 mm) are size, shape, surface) and chemical (dissolved and leached rare in the European urban environment’.11 As PAHs are the chemicals, surface catalytic reactions) properties of the par- result of incomplete combustion, they are a potential marker ticles are involved in toxic, genotoxic and carcinogenic health for particles from combustion sources.12 eVect mechanisms of inhaled particulates.As particles with diameters <0.1 mm (termed ultrafine Pagano et al.investigated the mutagenicity of total (PM-10) particles) coagulate relatively fast ( lifetimes <1 h),13 diVerand particle size fractions of urban particulates.5 They found ences in particle size distributions with the distance of the no correlation between total or coarse particle concentrations sampling site from major sources such as busy roads are in air and the mutagenic activity but did find correlations with expected, especially for particles <1 mm.These changes in size smaller particle size; moreover, the finer the particles, the distributions are expected to be accompanied by changes in greater is the mutagenicity. Particle toxicity and carcinogenicity concentration of chemical compounds in the size classes.are enhanced by numerous organic constituents, e.g. PAHs Obviously, changes in observed particle size distributions are and oxy- and nitro-PAHs. In the urban atmosphere PAHs are influenced by meteorological conditions (e.g., wind direction strongly associated with fine particles.6,7 The emissions of and speed, relative humidity, temperature and ground level automobiles, especially of diesel engines, are a major source thermal inversions).14 The aim of this study was to investigate of fine and ultrafine particles in urban environments.The mass the variability in the observed size distribution of particle distributions of particulate emissions from modern diesel adsorbed PAHs on an inner city sampling site depending on engines usually exhibit three log-normal modes that are centred diVerent wind directions and on the distance from a crossing at aerodynamic particle diameters of 0.09, 0.2 and 0.7–1 mm,8 with heavy traYc.whereas spark ignition vehicles exhibit bimodal distributions with maximum particle numbers at 0.04–0.06 and 0.9–1.4 mm.9 Experimental Research by Noble and Prather indicates that a connection may exist between particle size, composition and source.The Sampling was performed in Munich in 1994 and 1996–97. The sampling site is located northeast of a crossing of roads with heavy traYc. North of the sampling site there is a railway and †Presented at AIRMON ’99, Geilo, Norway, February 10–14, 1999. J. Environ. Monit., 1999, 1, 357–360 357northeast of the site is a large inner city park.The environs are strongly correlated with each other (Person correlation coeYcient r0.84, p=0.0001). There are no statistically sig- of the sampling site are shown in Fig. 1. The oYcial data of the daily traYc census from the city administration at the nificant outliers detectable except pyrene in sampling period 2 (sample ID Pa2). In this summer period the pyrene concen- crossing are 36 000 cars plus 2400 trucks on one road and 13 000 cars plus 1000 trucks on the other.trations in the samples were significantly lower than those of the other PAHs than in the other samples. We assume that Samples were taken at two diVerent distances from the crossing, 10 m (site A) and approximately 80 m (site B). Six- photochemical reactions of pyrene and not evaporation losses during sampling are responsible for the relatively lower concen- stage Berner low-pressure cascade impactors at a flow rate of 79.8 l min-1 were used for sampling.Uncoated aluminum foils trations detected. This assumption is supported by the fluoranthene (b.p. lower than that of pyrene) concentrations, which were employed as the sampling substrate.The particles were separated into the size ranges 0.04–0.14, 0.14–0.49, 0.49–1.72, do not exhibit this reduction. The PAH concentrations are strongly correlated with the daily average concentrations of 1.72–6.0 and 6.0–21.0 mm with geometric mean diameters of 0.075, 0.26, 0.92, 3.2 and 11.2 mm, respectively. Owing to the NO (r=0.88, p=0.0001) and CO (r=0.82, p=0.0001). The constant PAH pattern we found for all our samples is an low PAH concentrations on coarse particles, the fractions >1.72 mm were combined for each sample.Parallel to sampling indicator that the same sources predominate in all the sampling periods. Although no significant diVerences in the PAH pattern the meteorological conditions of wind direction, wind speed, relative humidity and temperature and the concentrations of were observed even in the single size ranges of the sampled particulates, diVerent distributions of the PAHs within the size CO, O3, NO and NO2 (30 min averages) were measured.Table 1 lists the sampling periods and the average values of classes were obvious. the above parameters for each sampling period. Samples were extracted with dichloromethane in an Size distributions of the particle associated PAHs ultrasonic bath, fractionated by column chromatography and analyzed by HPLC according to a previously published In 1994 we took samples at site A at a 10 m distance from the crossing.In each sample from these sampling periods we found method.15 For this study quantitative data were measured for fluoranthene, pyrene, chrysene, benzo[b]fluoranthene, benzo[-e distribution of the particle associated PAHs in the particle size classes; 45–55% of the total amount of PAHs was k]fluoranthene, benzo[a]pyrene and benzo[ ghi ]perylene. found on the first impactor stage (0.04–0.14 mm, geometric mean diameter 0.075 mm).Hence we assumed that this distri- Results and discussion bution is typical of an inner city situation with freshly generated aerosol from motor vehicles.Concentrations of the PAHs In 1996 and 1997 we repeated the measurements at this The concentrations of the PAHs in the investigated samples sampling location. Unfortunately, we were not able to take are given in Table 2. The total concentration of the quantified the samples at exactly the same place until the end of 1997.PAHs ranged from 1.7 to 15.2 ng m-3. In order to identify The new sampling site was about 80 m from the crossing (site diVerences in the PAH patterns, we added the PAH concen- B). Surprisingly, in our sampling period in December 1996 we trations from the single impactor stages to the total concen- measured PAH distributions in the particle size classes similar trations of the individual PAHs.These total concentrations to those that we found to be more representative of sampling sites at the outskirts of cities.15,16 In these samples the maximum amount of PAHs was found in the size range 0.14–1.72 mm. The greater distance from the crossing area, which is a strong local source of PAHs and fine aerosol, could be a possible reason for these diVerences in the observed PAH distributions.In order to investigate the influence of the distance we ran another sampling period and took parallel samples at 10 m (site A) and 80 m (site B) from the crossing. The evaluation of the data we obtained from these samples led to no distinct result. The total concentrations of the PAHs were equal at both sites except on the last day (Pa4/8).On this day, with wind from the crossing the PAH concentrations are signifi- cantly lower at the sampling site further from the crossing. The diVerences in the size distributions of the PAHs in these parallel samples are very small and in most cases not crucial. Even on the only day with wind from the crossing area no significant diVerences in the size distribution were observed (Fig. 2b). Analyzing the data from all sampling periods, we found a strong connection between the observed PAH distribution in the particle size ranges and the wind direction. Depending on the wind direction, three diVerent distributions with maximum PAH concentration in a single size range were observed. The maximum PAH concentration on very small particles was observed with wind from west to southwest (Fig. 3). On these days the wind was blowing directly from the crossing area or the roads with heavy traYc; 45–55% of the total amount of PAHs was found on the first impactor stage with a geometric mean diameter of 75 nm. On days with changing wind directions from northeast to southeast we found the maximum Fig. 1 Environs of the sampling site. PAH concentrations on particles with a geometric mean diam- 358 J.Environ. Monit., 1999, 1, 357–360Table 1 Sampling periods, average values of temperature (T), relative humidity (RH), windspeed (WS) and concentrations of ozone, nitrogen oxides and carbon monoxide during the sampling Sample Sampling RH WS/ O3/ NO/ NO2/ CO/ ID period T/°C (%) ms-1 mg m-3 mg m-3 mg m-3 mg m-3 Pa1/1 02.03.94–03.03.94 6.8 72 2.1 31 53 33 1.5 Pa1/2 03.03.94–04.03.94 8.4 63 2.1 27 60 36 1.7 Pa2/1 16.08.94–17.08.94 20.8 46 0.9 63 41 47 1.4 Pa2/2 17.08.94–18.08.94 17.7 72 1.0 40 69 64 1.4 Pa2/3 18.08.94–19.08.94 17.0 54 1.0 26 76 48 1.5 Pa3/1 09.12.96–10.12.96 -1.9 87 1.4 4 67 46 1.2 Pa3/2 10.12.96–11.12.96 0.1 82 0.7 4 162 59 2.2 Pa3/3 11.12.96–12.12.96 -1.5 87 0.6 4 182 65 2.1 Pa3/4 12.12.96–13.12.96 0.5 79 0.5 4 381 89 3.7 Pa3/5 13.12.96–14.12.96 4.4 85 1.1 5 191 69 3.0 Pa3/6 16.12.96–17.12.96 1.1 78 1.0 5 160 61 2.1 Pa3/7 17.12.96–18.12.96 5.1 78 0.6 7 233 76 3.1 Pa4/1 28.10.97–29.10.97 -0.6 57 4.7 38 8 17 0.9 Pa4/2 29.10.97–30.10.97 0.6 54 4.0 31 8 24 1.0 Pa4/3 30.10.97–31.10.97 3.4 48 1.9 18 48 30 1.4 Pa4/4 02.11.97–03.11.97 3.5 71 0.0 5 130 20 2.9 Pa4/5 03.11.97–04.11.97 4.2 68 0.2 23 13 37 1.2 Pa4/6 04.11.97–05.11.97 3.5 74 0.0 1 138 9 2.5 Pa4/7 05.11.97–06.11.97 9.3 64 0.1 1 82 29 2.0 Pa4/8 06.11.97–07.11.97 17.5 47 0.1 16 51 30 1.6 Table 2 Total concentrations of fluoranthene (Fla), pyrene (Pyr), chrysene (Chr), benzo[b]fluoranthene+benzo[k]fluoranthene (Bbk), benzo[a]pyrene (BaP) and benzo[ ghi]perylene (Bgh) in the samples, totalled over all impactor stages Sample Sample Fla/ Pyr/ Chr/ Bbk/ BaP/ Bgh/ Total/ ID volume/m3 Site pg m-3 pg m-3 pg m-3 pg m-3 pg m-3 pg m-3 pg m-3 Pa1/1 113 A 880 1200 550 1000 510 1000 5140 Pa1/2 114 A 710 940 510 1000 520 900 4580 Pa2/1 103 A 560 100 390 660 290 630 2630 Pa2/2 110 A 640 240 550 740 330 560 3060 Pa2/3 115 A 500 200 490 810 350 710 3060 Pa3/1 103 B 970 850 500 1600 880 770 5570 Pa3/2 101 B 1600 1610 1900 3200 1400 1900 1610 Pa3/3 109 B 890 980 670 1900 820 1100 6360 Pa3/4 110 B 2100 2200 2000 4200 1700 3000 15200 Pa3/5 130 B 490 510 990 1500 760 1400 5650 Pa3/6 109 B 760 770 1100 1700 820 1300 6450 Pa3/7 108 B 750 850 1400 1800 1000 1800 7600 Pa4/1A 116 A 740 660 400 1000 360 510 3670 Pa4/1B 116 B 730 690 430 1000 370 440 3660 Pa4/2A 111 A 720 610 350 1000 300 370 3350 Pa4/2B 111 B 700 520 340 820 250 310 2940 Pa4/3A 112 A 1210 1100 680 1400 490 580 5460 Pa4/3B 112 B 1130 930 560 1300 410 490 4820 Pa4/4A 98 A 1010 1100 1000 1500 680 920 6210 Pa4/4B 98 B 1090 1100 1200 1900 810 940 7040 Pa4/5A 113 A 590 470 360 990 230 400 3040 Pa4/5B 113 B 620 490 360 1000 240 310 3020 Pa4/6A 107 A 1340 1200 1500 1800 850 960 7650 Pa4/6B 107 B 1370 1100 1700 2400 1000 1100 8670 Pa4/7A 112 A 1010 840 1100 4300 1600 2300 11150 Pa4/7B 112 B 1030 890 1000 4500 1600 1800 10820 Pa4/8A 111 A 450 570 450 610 300 400 2780 Pa4/8B 111 B 190 200 290 510 130 340 1660 Fig. 3 Average size distribution of particle adsorbed PAHs and wind Fig. 2 Comparison of size distributions of particle adsorbed PAHs with sampling at diVerent distances from the crossing (A=10 m, B= direction (number of 30 min averages) at the samplings Pa1/1, Pa1/2, Pa2/1, Pa2/2, Pa2/3, Pa4/8A and Pa4/8B.Wind coming from the 80 m). The mean wind directions were southeast to east with sampling Pa4/1 (a) and southwest to west with sampling Pa5/8 (b). crossing. PAH concentration range, 1.7–5.1 ng m-3. J. Environ. Monit., 1999, 1, 357–360 359The total PAH concentrations are not significantly influenced by the wind direction.The variability of the PAH concentrations detected with one wind direction is as high as the variability from direction to direction. The diVerent size distributions of particle adsorbed PAHs are correlated with the distance from the sampling site to sources of combustion aerosol. The shorter the distance to the source(s), the higher was the proportion of PAHs on small particles. With wind direct from the crossing area, a strong Fig. 4 Size distribution of particle adsorbed PAHs and wind direction local source of fine and ultrafine aerosol, the maximum PAH (number of 30 min averages) at the sampling Pa3/4. Wind coming concentration was found on the smallest particles. Wind from from built-up area. PAH concentration, 15.1 ng m-3.the built-up area near the sampling site, a diVuse and more distant source of aerosol, shows a shift in the PAH distribution to larger particles. A further shift to a higher proportion of the PAHs on larger particles was found with wind from the park and thus from the diVuse sources behind it. We conclude that the distribution of particle adsorbed PAHs within diVerent particle size classes is substantially influenced by the distance from the sampling site to strong sources of PAH loaded particulate matter.References Fig. 5 Average size distribution of particle adsorbed PAHs and wind direction (number of 30 min averages) at the samplings Pa2/1, Pa3/1, 1 J. Pekkanen, K. L. Timonen, J. Ruuskanen, A. Reponen and Pa3/2, Pa3/5, Pa3/6, Pa4/5A and Pa4/5B.Wind coming from the park A. Mirme, Environ. Res., 1997, 74, 24. nearby. PAH concentration range, 2.6–11.7 ng m-3. 2 P. Penttinen, K. L. Timonen, P. Tiittanen, M. Vallius, A. 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D. Bofinger and J. Hitchins, Environ. Sci. Technol., 1998, 32, 3845. 10 C. A. Noble and K. A. Prather, Environ. Sci. Technol., 1996, eter of 260 nm (Fig. 4). In this case the wind was blowing 30, 2667. from the built-up area near the sampling site. The third 11 T. Tuch, P. Brand, H. E. Wichmann and J. Heyder, Atmos. distribution with the maximum PAHconcentration on particles Environ., 1997, 31, 4193. 12 C. K. Li and R. M. Kamens, Atmos. Environ., Part A, 1993, with a geometric mean diameter of 920 nm we found on days 27, 523. with the main wind direction from northeast to east (Fig. 5). 13 D. Y. H. Pui and D. R. Chen, J. Aerosol Sci., 1997, 28, 539. On these days the wind was blowing mainly from the direction 14 A. Trier, Atmos. Environ., 1997, 31, 909. of the city park nearby. Distributions with no unique maximum 15 J. Schnelle, T. Ja�nsch, K. Wolf, I. Gebefu� gi and A. Kettrup, in PAH concentration in a distinct particle size range were Chemosphere, 1995, 31, 3119. observed on days with wind from the park and the main 16 J. Schnelle, K. Wolf, G. Frank, B. Hietel, I. Gebefu� gi and A. Kettrup, Analyst, 1996, 121, 1301. street. This is wind from northeast to south (Fig. 6). In this case we found a mixture of the distributions we observed on days with the wind mainly from northeast and southeast. Paper 9/01494B 360 J. Environ. Monit., 1999, 1, 357&nda