Linas
Kliucininkas
*a,
Dainius
Martuzevicius
a,
Edvinas
Krugly
a,
Tadas
Prasauskas
a,
Violeta
Kauneliene
a,
Peter
Molnar
b and
Bo
Strandberg
b
aDepartment of Environmental Engineering, Kaunas University of Technology, Radvilenu pl. 19, LT50254, Kaunas, Lithuania. E-mail: linas.kliucininkas@ktu.lt
bOccupational and Environmental Medicine, Sahlgrenska Academy at the University of Gothenburg, Box 414, SE-40530, Goteborg, Sweden
First published on 16th November 2010
This complex study presents indoor and outdoor levels of air-borne fine particles, particle-bound PAHs and VOCs at two urban locations in the city of Kaunas, Lithuania, and considers possible sources of pollution. Two sampling campaigns were performed in January–February and March–April 2009. The mean outdoor PM2.5 concentration at Location 1 in winter was 34.5 ± 15.2 µg m−3 while in spring it was 24.7 ± 12.2 µg m−3; at Location 2 the corresponding values were 36.7 ± 21.7 and 22.4 ± 19.4 µg m−3, respectively. In general there was little difference between the PM concentrations at Locations 1 and 2. PM2.5 concentrations were lower during the spring sampling campaign. These PM concentrations were similar to those in many other European cities; however, the levels of most PAHs analysed were notably higher. The mean sum PAH concentrations at Locations 1 and 2 in the winter campaign were 75.1 ± 32.7 and 32.7 ± 11.8 ng m−3, respectively. These differences are greater than expected from the difference in traffic intensity at the two sites, suggesting that there is another significant source of PAH emissions at Location 1 in addition to the traffic. The low observed indoor/outdoor (I/O) ratios indicate that PAH emissions at the locations studied arise primarily from outdoor sources. The buildings at both locations have old windows with wooden frames that are fairly permissive in terms of air circulation. VOC concentrations were mostly low and comparable to those reported from Sweden. The mean outdoor concentrations of VOC's were: 0.7 ± 0.2, 3.0 ± 0.8, 0.5 ± 0.2, 3.5 ± 0.3, and 0.2 ± 0.1 µg m−3, for benzene, toluene, ethylbenzene, sum of m-, p-, o-xylenes, and naphthalene, respectively. Higher concentrations of VOCs were observed during the winter campaign, possibly due to slower dispersion, slower chemical transformations and/or the lengthy “cold start” period required by vehicles in the wintertime. A trajectory analysis showed that air masses coming from Eastern Europe carried significantly higher levels of PM2.5 compared to masses from other regions, but the PAHs within the PM2.5 are of local origin. It has been suggested that street dust, widely used for winter sanding activities in Eastern and Central European countries, may act not only as a source of PM, but also as source of particle-bound PAHs. Other potential sources include vehicle exhaust, domestic heating and long-range transport.
Environmental impactThe paper addresses the issue of urban air quality, which becomes an increasingly important topic with tightening air quality requirements. Ambient air quality depends on number of factors and pollution sources, which often cannot be easily identified and managed. A complex urban air quality assessment study was conducted focusing on three key groups of urban air pollutants: particulate matter, PM-bound PAHs, and VOCs, estimating both local sources of pollution and contribution by a long distance transport. The paper reports information about the levels and distribution of the above compounds from the Baltic States, where such type of information is scarce. Our findings contribute to the sustainable management of the cities in the region as well as Europe and worldwide. |
In recent decades, much concern about indoor and outdoor air quality has also focused on volatile organic compounds (VOCs), such as benzene, ethylbenzene, toluene, and xylenes (BETXs).13–17 This is because VOCs can readily enter the body via inhalation. Consequently, long-term exposure to VOCs presents a substantial health risk, even at low concentrations.17 In economically developed countries the main outdoor source of VOCs is road traffic. For instance, studies performed in Denmark in 1997/1998 indicated that benzene emissions from traffic strongly contribute not only to urban concentrations but also to exposure and domestic concentrations.18 This study reports outdoor urban concentrations for benzene, toluene, and the sum of xylenes of 9.6, 25.7, and 27.6 µg m−3, and indoor air concentrations of 3.5, 25.3, and 9.4 µg m−3, respectively. Similarly, a study on air pollution in Germany concluded that in street canyons, high-density traffic is the primary source of BETX compounds in indoor air.15,19
Despite the concern regarding VOCs, data on their levels and distribution in Lithuania are sparse, and to our knowledge limited to information collected in two outdoor measurement campaigns.20 Thus, the aim of this study was to investigate indoor and outdoor levels of PM, particle-bound PAHs and VOCs at two urban locations in Kaunas, Lithuania. In addition to presenting the results, possible sources of these pollutants, such as road traffic, aerosolized street dust and long-range transport are discussed.
The second location (Location 2) was on a one-way three-lane street (Kestucio g.). This street is in the city centre, with an average daily traffic of approx. 19000 vehicles, including 450 diesel public buses and 1820 microbuses. The traffic peaks were less pronounced in this location.
In Location 1 air was sampled at an indoor site inside a room and an outdoor site on the balcony on the 3rd floor of a 5-storey university dormitory, located 12 m away from the street. The room was occupied by two non-smoking students who carried out their routine activities (no thermal aerosol generation was expected). Outdoor air was sampled at Location 2 from a storage facility on the first floor of a university faculty building, 3 m away from the street. The indoor site was an unoccupied room visited only occasionally by sampling crew and other university staff.
In order to estimate seasonal fluctuations in the atmospheric abundance of the two main PM size fractions (PM2.5 and PM10), and the particle-bound PAH content of these fractions, daily samples were taken at the outdoor sites over two-week periods in January and April of 2009 at Location 1, and in February and March of 2009 at Location 2. In addition, the levels of the PM4 fraction and VOCs at both indoor and outdoor sites were monitored in week-long daily sampling campaigns; at Location 1 samples were obtained in January and April of 2009, while at Location 2, samples were taken in February and March of 2009. In each case samples were collected (as described below) over eight hour periods during weekdays.
The PM10 and PM2.5 fractions were separated at an air sampling flow rate of 16.7 l min−1 (1 m3 h−1) by cyclones (URG Corp, Chapel Hill, NC, USA) with appropriate cut-off sizes, and separate rotary vane vacuum pumps equipped with flow-meters. To minimise indoor noise nuisance for residents, the PM4 fraction was sampled using a flow rate of 2.2 l min−1 (0.13 m3 h−1) by SKC Conductive Plastic Cyclones for respirable dust sampling with personal sampling pumps.
The samples were analyzed using a Unity Markes International Limited thermal desorber (Unity Ultra TD) connected to a gas chromatograph (6890, Agilent Technologies, Inc., Santa Clara, CA, USA), with a selective mass detector (5973, Agilent Technologies, Inc.). Each sample tube was thermally desorbed for 5 min at 320 °C, focused on a cold trap at −10 °C and desorbed at a maximum temperature of 320 °C for GC injection. The GC oven temperature was maintained at 50 °C, for 3 min, then raised at 10 °C min−1 to 180 °C, and finally at 10 °C min−1 to 300 °C, at which temperature it was held for 5 min. The VOCs (benzene, toluene, ethylbenzene, xylenes and naphthalene) were detected using SIM, including the two most abundant ions of each compound. Controls for the quantification and identification of target compounds were established by injecting standard solutions (5 µL) of all target compounds in methanol into Perkin Elmer tubes in a stream of helium (15 mL min−1).
Statistical calculations were performed using Wilcoxon's rank sum test implemented in SAS System for Windows, version 9.2.23 Statistical significance refers to p < 0.05 in two-tailed tests.
Kaunas, Lithuania | Oxford, Ohio | Madrid, Spain | Bern, Switzerland | Athens, Greece | Belgrade, Serbia | Beirut, Liban | Teheran, Iran | Istambul, Turkey | Barcelona, Spain | Berlin, Germany | San Paulo, Brazil | |||
---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
Location 1 | Location 2 | Automated monitoring station, EPA | ||||||||||||
a Winter sampling period. b Spring sampling period. | ||||||||||||||
PM2.5a | 34.5 ± 15.2 | 36.7 ± 21.7 | 26.81 ± 12.43 | 15.7 | 34 | 24.6 | 40.2 | 61 | 40 | 24.3 | 27.7 | 27.7 | 30 | 20.9 |
PM2.5b | 24.7 ± 12.2 | 22.4 ± 19.4 | 23.19 ± 11.75 | |||||||||||
PM10a | 35.2 ± 14.6 | 39.7 ± 20.3 | 33.91 ± 20.03 | 16.3 | 48 | 40.2 | 75.5 | 72 | 76 | 122.1 | 40.4 | 40.6 | 38 | 10.7 |
PM10b | 41.7 ± 11.8 | 34.2 ± 20.6 | 32.55 ± 22.88 | |||||||||||
Current study | ref. 24 | ref. 25 | ref. 26 | ref. 27 | ref. 28 | ref. 29 | ref. 30 | ref. 31 | ref. 32 | ref. 33 | ref. 34 |
The outdoor PAH concentrations measured at the two sampling locations in this study are presented in Fig. 1. High molecular weight PAHs with five to six rings, such as benzo(a)anthracene, chrysene, benzo(a)pyrene, benzo(g,h,i)perylene, predominated, while low molecular weight compounds were present only in smaller quantities. High concentrations of the 4-ring PAHs, fluoranthene and pyrene, were also observed. These findings are as expected, since 90% of 5–6 ring PAHs are adsorbed on particles and only 10% partition into the vapour phase, 4-ring PAHs are found in similar amounts in both phases, while PAHs with 2–3 rings are found predominantly (>90%) in the vapour phase.37 Five PAH components, i.e.acenaphthylene, 2,3,5-trimethylnaphthalene, 1-methylfluoranthene, 1-methylfluorene, and 2-methylchrysene, were not detected in any samples.
![]() | ||
Fig. 1 Mean concentrations of PAHs measured in the PM2.5 fraction in the winter sampling period. |
The mean sum PAH concentrations at Locations 1 and 2 in the winter campaign were 75.1 ± 32.7 and 32.7 ± 11.8 ng m−3, respectively. This difference is greater than expected from the difference in traffic intensity at the two sites, suggesting that there is another significant source of PAH emissions at Location 1 in addition to the traffic.
As shown in Table 2 the concentrations of most PAHs observed in this study are higher than those reported by other authors, particularly at Location 1. Comparison of benzo(a)pyrene levels in the PM2.5 fraction reported by Saarnio et al. (2008)4 showed that in Western European cities concentrations varied from 0.1 to 1.1 ng m−3 and in Eastern and Central European cities from 3.0 to 3.2 ng m−3. Benzo(a)pyrene levels at Location 2 were similar to those reported in Prague and Zagreb. It should be noted that the European limit value for benzo(a)pyrene is 1 ng m−3 in PM10.
Compound | This study, Location 1 | This study, Location 2 | Kurkimäki, Finland, Hellen et al., 2008 | Bologna, Italy, Stracquandanio et al., 2007 | Duisburg, Germany | Prague, Czech R. | Amsterdam, Netherlands | Helsinki, Finland | Zagreb, Croatia, Sisovic et al., 2005 | Atlanta, USA, Liet al., 2009 |
---|---|---|---|---|---|---|---|---|---|---|
Saarnio et al., 2008 | ||||||||||
Winter | Winter | Winter | Winter | Winter | Winter | Winter | Spring | Winter | Winter | |
Phenanthrene | 1.3 ± 0.6 | 1.2 ± 0.4 | 2.5 | 0.9 | 0.7 | 4.8 | 0.8 | 0.3 | 0.15 | |
Anthracene | 0.2 ± 0.1 | 0.2 ± 0.1 | 0.4 | 0.02 | ||||||
Fluoranthene | 7.6 ± 3.4 | 3.5 ± 1.2 | 4.4 | 1.6 | 6.4 | 1.3 | 0.5 | 3.7 | 0.14 | |
Pyrene | 9.5 ± 4.1 | 3.9 ± 1.3 | 4.0 | 1.4 | 1.3 | 5.6 | 0.9 | 0.4 | 4.7 | 0.17 |
Retene | 4.6 ± 1.3 | 1.4 ± 0.5 | 0.14 | |||||||
Benzo(a)anthracene | 7.0 ± 3.0 | 2.8 ± 1.1 | 1.3 | 1.1 | 0.19 | |||||
Chrysene | 9.2 ± 4.1 | 4.5 ± 1.7 | 1.6 | 2.2 | 0.23 | |||||
Benzo(b)fluoranthene | 5.8 ± 2.0 | 3.0 ± 0.7 | 2.5 | 3.5 | 0.61 | |||||
Benzo(k)fluoranthene | 5.6 ± 1.9 | 3.1 ± 0.9 | 0.9 | 2.1 | 0.18 | |||||
Benzo(a)pyrene | 6.2 ± 3.9 | 3.2 ± 1.0 | 1.3 | 1.7 | 1.1 | 3.0 | 0.3 | 0.1 | 3.2 | 0.42 |
Indeno(1,2,3-c,d)pyrene | 9.6 ± 1.8 | 2.6 ± 0.8 | 2.2 | 0.59 | ||||||
Dibenzo(a,h)anthracene | 2.3 ± 1.9 | 0.7 ± 0.2 | 0.4 | 0.02 | ||||||
Benzo(g,h,i)perylene | 6.1 ± 2.9 | 2.6 ± 0.8 | 1.5 | 2.7 | 4.1 | 0.31 | ||||
Sum PAHs | 75.1 ± 32.7 | 32.7 ± 11.8 | 3.17 |
The abundance of compounds such as benzo(a)anthracene, chrysene, benzo(a)pyrene, benzo(g,h,i)perylene that are characteristic of vehicular emissions suggests that traffic is probably one of the most important sources of PAH emissions at the investigated sites in Kaunas. However, although the traffic intensity is lower at Location 1 than at Location 2, levels of certain individual PAHs at Location 1 were found to be up to four times greater than at Location 2, possibly because most buildings are heated by the district supply system at Location 2, while at Location 1 most households have independent heating systems. To identify the sources of the various PAH emissions more clearly, the data were subjected to correlation analysis, factor analysis and a comparative analysis of indicative ratios and fractions. The intercorrelation matrix of the measured PAH concentrations is shown in Table 3.
Nap | 2MeNap | 1MeNap | Bph | Acy | Fl | Phe | Ant | 2MePhe | 1MePhe | 1MeAnt | 2PhNap | Fla | Pyr | MePyr | Ret | BaAnt | Chry | BbF | BkF | BaP | Per | IdP | DbA | BghiP | ||
Nap | 0.61 | 0.72 | 0.68 | 0.71 | 0.75 | 0.84 | 0.76 | 0.76 | 0.72 | 0.74 | 0.75 | 0.66 | 0.67 | 0.66 | 0.64 | 0.55 | 0.59 | 0.63 | 0.63 | 0.58 | 0.40 | 0.54 | −0.05 | 0.34 | Nap | |
2MeNap | 0.82 | 0.62 | 0.48 | 0.73 | 0.67 | 0.58 | 0.45 | 0.58 | 0.65 | 0.58 | 0.58 | 0.52 | 0.52 | 0.42 | 0.49 | 0.30 | 0.32 | 0.42 | 0.37 | 0.24 | 0.14 | 0.25 | 0.09 | −0.02 | 2MeNap | |
1MeNap | 0.83 | 0.97 | 0.79 | 0.34 | 0.59 | 0.46 | 0.13 | 0.30 | 0.25 | 0.27 | 0.28 | 0.14 | 0.14 | 0.11 | 0.12 | −0.04 | −0.03 | 0.08 | 0.06 | 0.00 | −0.22 | 0.20 | −0.41 | −0.21 | 1MeNap | |
Bph | 0.53 | 0.77 | 0.82 | 0.60 | 0.78 | 0.59 | 0.46 | 0.49 | 0.45 | 0.49 | 0.51 | 0.38 | 0.37 | 0.35 | 0.35 | 0.22 | 0.27 | 0.34 | 0.31 | 0.22 | −0.07 | 0.26 | −0.35 | −0.16 | Bhp | |
Acy | 0.77 | 0.90 | 0.93 | 0.72 | 0.92 | 0.92 | 0.88 | 0.85 | 0.82 | 0.80 | 0.77 | 0.71 | 0.70 | 0.66 | 0.69 | 0.60 | 0.64 | 0.65 | 0.63 | 0.57 | 0.45 | 0.37 | 0.21 | 0.38 | Acy | |
Fl | 0.75 | 0.92 | 0.97 | 0.73 | 0.93 | 0.87 | 0.75 | 0.68 | 0.59 | 0.61 | 0.58 | 0.49 | 0.45 | 0.41 | 0.39 | 0.35 | 0.41 | 0.35 | 0.37 | 0.37 | 0.21 | 0.07 | 0.17 | 0.13 | Fl | |
Phe | 0.75 | 0.92 | 0.95 | 0.73 | 0.98 | 0.97 | 0.95 | 0.95 | 0.91 | 0.93 | 0.92 | 0.87 | 0.85 | 0.84 | 0.82 | 0.79 | 0.80 | 0.81 | 0.82 | 0.77 | 0.65 | 0.65 | 0.15 | 0.60 | Phe | |
Ant | 0.75 | 0.92 | 0.95 | 0.73 | 0.98 | 0.97 | 1.00 | 0.98 | 0.97 | 0.97 | 0.96 | 0.94 | 0.93 | 0.92 | 0.89 | 0.87 | 0.90 | 0.89 | 0.90 | 0.81 | 0.71 | 0.64 | 0.20 | 0.65 | Ant | |
2MePhe | 0.75 | 0.92 | 0.95 | 0.73 | 0.98 | 0.97 | 1.00 | 1.00 | 0.98 | 0.99 | 0.98 | 0.96 | 0.95 | 0.93 | 0.91 | 0.91 | 0.91 | 0.92 | 0.93 | 0.87 | 0.78 | 0.70 | 0.21 | 0.70 | 2MePhe | |
1MePhe | 0.72 | 0.88 | 0.93 | 0.68 | 0.97 | 0.98 | 0.98 | 0.98 | 0.98 | 0.99 | 0.98 | 0.98 | 0.97 | 0.96 | 0.95 | 0.91 | 0.92 | 0.95 | 0.95 | 0.84 | 0.78 | 0.74 | 0.23 | 0.73 | 1MePhe | |
1MeAnt | 0.78 | 0.95 | 0.98 | 0.78 | 0.95 | 0.98 | 0.98 | 0.98 | 0.98 | 0.97 | 0.99 | 0.97 | 0.96 | 0.95 | 0.93 | 0.92 | 0.92 | 0.94 | 0.95 | 0.87 | 0.79 | 0.73 | 0.18 | 0.71 | 1MeAnt | |
2PhNap | 0.75 | 0.92 | 0.95 | 0.73 | 0.98 | 0.97 | 1.00 | 1.00 | 1.00 | 0.98 | 0.98 | 0.98 | 0.97 | 0.96 | 0.93 | 0.91 | 0.92 | 0.93 | 0.95 | 0.86 | 0.76 | 0.77 | 0.13 | 0.70 | 2PhNap | |
Fla | 0.75 | 0.92 | 0.95 | 0.73 | 0.98 | 0.97 | 1.00 | 1.00 | 1.00 | 0.98 | 0.98 | 1.00 | 0.99 | 0.99 | 0.97 | 0.95 | 0.96 | 0.97 | 0.98 | 0.85 | 0.84 | 0.83 | 0.23 | 0.81 | Fla | |
Pyr | 0.72 | 0.88 | 0.93 | 0.68 | 0.97 | 0.98 | 0.98 | 0.98 | 0.98 | 1.00 | 0.97 | 0.98 | 0.98 | 0.99 | 0.98 | 0.96 | 0.97 | 0.98 | 0.99 | 0.86 | 0.84 | 0.84 | 0.24 | 0.81 | Pyr | |
MePyr | 0.77 | 0.88 | 0.93 | 0.67 | 0.90 | 0.98 | 0.95 | 0.95 | 0.95 | 0.97 | 0.97 | 0.95 | 0.95 | 0.97 | 0.98 | 0.97 | 0.97 | 0.99 | 0.99 | 0.87 | 0.86 | 0.85 | 0.23 | 0.83 | MePyr | |
Ret | 0.75 | 0.92 | 0.95 | 0.73 | 0.98 | 0.97 | 1.00 | 1.00 | 1.00 | 0.98 | 0.98 | 1.00 | 1.00 | 0.98 | 0.95 | 0.93 | 0.93 | 0.97 | 0.97 | 0.84 | 0.82 | 0.83 | 0.20 | 0.78 | Ret | |
BaAnt | 0.73 | 0.85 | 0.90 | 0.62 | 0.93 | 0.97 | 0.97 | 0.97 | 0.97 | 0.98 | 0.95 | 0.97 | 0.97 | 0.98 | 0.98 | 0.97 | 0.99 | 0.97 | 0.98 | 0.93 | 0.95 | 0.74 | 0.38 | 0.88 | BaAnt | |
Chry | 0.73 | 0.53 | 0.58 | 0.33 | 0.62 | 0.63 | 0.63 | 0.63 | 0.63 | 0.65 | 0.62 | 0.63 | 0.63 | 0.65 | 0.73 | 0.63 | 0.75 | 0.97 | 0.98 | 0.92 | 0.93 | 0.75 | 0.38 | 0.87 | Chry | |
BbF | 0.72 | 0.83 | 0.87 | 0.53 | 0.90 | 0.95 | 0.93 | 0.93 | 0.93 | 0.97 | 0.92 | 0.93 | 0.93 | 0.97 | 0.97 | 0.93 | 0.98 | 0.73 | 0.98 | 0.88 | 0.88 | 0.82 | 0.24 | 0.84 | BbF | |
BkF | 0.73 | 0.85 | 0.90 | 0.62 | 0.93 | 0.97 | 0.97 | 0.97 | 0.97 | 0.98 | 0.95 | 0.97 | 0.97 | 0.98 | 0.98 | 0.97 | 1.00 | 0.75 | 0.98 | 0.90 | 0.89 | 0.83 | 0.27 | 0.85 | BkF | |
BaP | 0.73 | 0.53 | 0.58 | 0.33 | 0.62 | 0.63 | 0.63 | 0.63 | 0.63 | 0.65 | 0.62 | 0.63 | 0.63 | 0.65 | 0.73 | 0.63 | 0.75 | 1.00 | 0.73 | 0.75 | 0.88 | 0.57 | 0.25 | 0.69 | BaP | |
Per | 0.63 | 0.78 | 0.85 | 0.63 | 0.92 | 0.93 | 0.95 | 0.95 | 0.95 | 0.97 | 0.92 | 0.95 | 0.95 | 0.97 | 0.95 | 0.95 | 0.98 | 0.73 | 0.95 | 0.98 | 0.73 | 0.60 | 0.57 | 0.93 | Per | |
IdP | 0.73 | 0.85 | 0.90 | 0.62 | 0.93 | 0.97 | 0.97 | 0.97 | 0.97 | 0.98 | 0.95 | 0.97 | 0.97 | 0.98 | 0.98 | 0.97 | 1.00 | 0.75 | 0.98 | 1.00 | 0.75 | 0.98 | −0.06 | 0.72 | IdP | |
DbA | 0.53 | 0.45 | 0.47 | 0.10 | 0.63 | 0.57 | 0.58 | 0.58 | 0.58 | 0.65 | 0.50 | 0.58 | 0.58 | 0.65 | 0.58 | 0.58 | 0.67 | 0.67 | 0.75 | 0.67 | 0.67 | 0.63 | 0.67 | 0.59 | DbA | |
BghiP | 0.73 | 0.85 | 0.90 | 0.62 | 0.93 | 0.97 | 0.97 | 0.97 | 0.97 | 0.98 | 0.95 | 0.97 | 0.97 | 0.98 | 0.98 | 0.97 | 1.00 | 0.75 | 0.98 | 1.00 | 0.75 | 0.98 | 1.00 | 0.67 | BghiP | |
Nap | 2MeNap | 1MeNap | Bhp | Acy | Fl | Phe | Ant | 2MePhe | 1MePhe | 1MeAnt | 2PhNap | Fla | Pyr | MePyr | Ret | BaAnt | Chry | BbF | BkF | BaP | Per | IdP | DbA | BghiP |
As can be seen from the table, inter-correlation among PAH concentrations is generally very high for most of PAHs analysed. At Location 2 low molecular weight (LMW) compounds correlate with high molecular weight (HMW) compounds better than at Location 1, but the correlations of chrysene, benzo(a)pyrene and dibenzo(a,h)anthracene with other PAH concentrations are weaker. Diesel fuel reportedly contains high concentrations of LMW compounds, but because of pyrosynthesis during combustion in diesel engines the emission rate of HMW PAHs is greater than that of LMW PAHs.38,39 Therefore, the high correlations of LMW and HMW PAH concentrations may be due to emissions from diesel engines.
It should be noted that correlations of 1-methylphenanthrene with most of the other PAHs, including high molecular weight compounds, are very high. The high observed concentrations of alkylated PAHs relative to unsubstituted PAHs may indicate the presence of petrogenic sources.40–42 Although the concentrations of methylated compounds observed in this study were lower than those of the corresponding unsubstituted species, the above-mentioned correlations between the concentration of 1-methylphenanthrene and those of most of the other PAH analytes suggest that significant quantities of the observed PAHs were derived from unburned fuel.
Pyrene and chrysene are known to be emitted during industrial oil burning, fluoranthene and pyrene are typically emitted by both petrol and diesel vehicles, while chrysene, benzo(b)fluoranthene, benzo(k)fluoranthene are characteristic of emissions from diesel vehicles.10 The high correlations between the concentrations of chrysene, benzo(b)fluoranthene, benzo(k)fluoranthene, fluoranthene and pyrene corroborate the importance of traffic as a source of PAH emissions at the investigated sites. However, it should be noted that the correlation of retene with HMW PAHs is also very high. Retene has been suggested as an indicator of biomass burning and has a unique formation mechanism or environmental pathway.1,43 Wood and peat are very commonly used fuels for heating individual houses in Kaunas.
To obtain further indications of the likely origins of the detected PAHs, sum concentrations of nine major combustion-derived PAHs (CPAHs: fluoranthene, pyrene, chrysene, benzo(b)fluoranthene, benzo(k)fluoranthene, benzo(a)pyrene, benzo[e]pyrene, indeno(1,2,3-c,d)pyrene, benzo(g,h,i)perylene) and CPAH/Sum PAH ratios were calculated. These ratios are reported to be 0.51, 0.41, and 0.30 for emissions from automobiles with catalytic converters, other automobiles, and heavy duty diesel trucks, respectively.44 The CPAH:
Sum PAH ratio at Location 1 was as high as 0.78, suggesting that traffic is not the only important source of CPAHs in Kaunas.
Factor analysis of the measured PAH concentrations provided further insights into the influence of traffic and fuel combustion on the air quality in Kaunas (Table 4). The analysis revealed two factors influencing PAH concentrations at Location 2 and four factors at Location 1. It is apparent that the retene and dibenzo(a,h)anthracene observed at Location 1 arise from a different source from that of the other combustion PAHs. By contrast, at Location 2, it is likely that traffic is the major source of PAHs, with a small quantity of the most volatile PAHs arising from a different source.
Location 1 | Location 2 | ||||||
---|---|---|---|---|---|---|---|
Factor 1 | Factor 2 | Factor 3 | Factor 4 | Factor 1 | Factor 2 | ||
Nap | 0.65 | 0.50 | 0.54 | 0.07 | Nap | 0.31 | 0.85 |
2MeNap | 0.79 | −0.12 | 0.04 | 0.57 | 2MeNap | 0.35 | 0.92 |
1MeNap | 0.94 | −0.03 | 0.32 | −0.03 | 1MeNap | 0.62 | 0.76 |
Bph | 0.81 | 0.18 | 0.43 | 0.27 | Bph | 0.65 | 0.63 |
Acy | 0.99 | 0.12 | 0.04 | 0.03 | Acy | 0.86 | 0.49 |
Fl | 0.99 | 0.07 | 0.04 | −0.09 | Fl | 0.85 | 0.52 |
Phe | 0.98 | 0.16 | 0.11 | −0.04 | Phe | 0.90 | 0.41 |
Ant | 0.94 | 0.30 | 0.16 | 0.05 | Ant | 0.90 | 0.43 |
2MePhe | 0.95 | 0.26 | 0.14 | 0.00 | 2MePhe | 0.90 | 0.42 |
1MePhe | 0.95 | 0.28 | 0.12 | 0.07 | 1MePhe | 0.91 | 0.40 |
1MeAnt | 0.90 | 0.33 | 0.24 | 0.11 | 1MeAnt | 0.92 | 0.39 |
2PheNap | 0.93 | 0.32 | 0.18 | 0.07 | 2PheNap | 0.92 | 0.38 |
Fla | 0.82 | 0.53 | 0.13 | 0.18 | Fla | 0.91 | 0.41 |
Pyr | 0.64 | 0.73 | 0.12 | 0.21 | Pyr | 0.90 | 0.43 |
MePyr | 0.44 | 0.82 | 0.22 | 0.29 | MePyr | 0.88 | 0.47 |
Ret | 0.17 | 0.58 | 0.32 | 0.73 | Re | 0.92 | 0.38 |
BaA | 0.18 | 0.97 | 0.12 | 0.07 | BaA | 0.86 | 0.50 |
Chry | 0.28 | 0.95 | −0.02 | 0.14 | Chry | 0.90 | 0.35 |
BbF | 0.45 | 0.83 | 0.32 | 0.07 | BbF | 0.90 | 0.44 |
BkF | 0.37 | 0.86 | 0.33 | 0.05 | BkF | 0.89 | 0.46 |
BaP | 0.04 | 0.90 | 0.07 | 0.00 | BaP | 0.89 | 0.32 |
Per | −0.17 | 0.96 | −0.18 | −0.07 | Per | 0.87 | 0.48 |
IdP | 0.42 | 0.62 | 0.56 | 0.01 | IdP | 0.87 | 0.47 |
DbaA | −0.35 | 0.04 | −0.91 | −0.09 | DbaA | 0.92 | 0.18 |
BghiP | 0.05 | 0.88 | −0.24 | −0.09 | BghiP | 0.85 | 0.51 |
As discussed by Saarnio et al. (2008), neither the levels of individual PAHs nor the ratios of their concentrations can be regarded as highly specific indicators of emission sources for several reasons: PAHs originate from a large variety of combustion sources with only slightly different emission profiles; PAHs have widely differing vapour pressures and reactivities; and particulate PAH concentrations depend on the ambient temperature and solar radiation intensity as well as on the total particulate mass concentration.4 Furthermore, some compounds, especially those that are semi-volatile (2–4 rings), may be lost during long sampling campaigns. Nevertheless, their concentration ratios can give hints about the relative importance of possible sources (see Fig. 2).
![]() | ||
Fig. 2 Ratios of indoor to outdoor (I/O) PAH concentrations in PM4 at Locations 1 and 2. |
In addition, indicative PAH concentration fractions and ratios were calculated, and the results were compared to data from a comprehensive study of PAHs in size-segregated particulate matter from European urban sites performed by Saarnio et al. (2008) and from a similar study by Tang et al. (2005) in China, Japan and Russia.4,7 Only data from cold seasons were included.
The observed indeno(1,2,3-c,d)pyrene:
(indeno(1,2,3-c,d)pyrene + benzo(g,h,i)perylene) ratio is comparable to those reported in other studies, confirming that traffic is a significant source of PAH emissions at both locations examined. This conclusion is further supported by the benzo(a)anthracene
:
(benzo(a)anthracene + chrysene) and benzo(a)pyrene
:
(benzo(a)pyrene + chrysene) ratios. The influence of fossil fuel combustion on PAH levels in Kaunas is indicated by the benzo(a)pyrene
:
benzo(g,h,i)perylene and benzo(a)pyrene
:
chrysene ratios.
The ratio of air-borne PAH concentrations in indoor environments to those in outdoor environments (I/O ratios) can be used to determine whether the major PAH source(s) are located indoors (in which case I/O > 1) or outdoors (in which case I/O < 1). I/O ratios for PAHs bound to the PM4 fraction are presented in Fig. 2. The low observed I/O ratios may indicate that PAH emissions at the locations studied arise primarily from outdoor sources. It should be noted that the buildings at both locations have old windows with wooden frames that are fairly permissive in terms of air circulation. Thus, residents of older buildings that are close to roads may be significantly exposed to PAHs and PM in general.
Measurement week | |||||||||
---|---|---|---|---|---|---|---|---|---|
1a | 2b | 3c | 4d | ||||||
Outdoor | Indoor | Outdoor | Indoor | Outdoor | Indoor | Outdoor | Indoor | ||
a Location 1, winter. b Location 2, winter. c Location 1, spring. d Location, 2 spring. | |||||||||
Benzene | Mean | 0.9 | 0.7 | 1.0 | 0.7 | 0.7 | 0.5 | 0.4 | 0.8 |
Std. dev. | 0.5 | 0.4 | 0.5 | 0.3 | 0.3 | 0.2 | 0.2 | 0.4 | |
Min | 0.4 | 0.3 | 0.5 | 0.4 | 0.4 | 0.3 | 0.3 | 0.3 | |
Max | 1.7 | 1.3 | 1.6 | 1.3 | 1.0 | 0.7 | 0.6 | 1.4 | |
Toluene | Mean | 2.7 | 5.3 | 2.0 | 1.8 | 1.2 | 0.9 | 3.5 | 7.0 |
Std. dev. | 3.2 | 3.4 | 1.0 | 0.4 | 0.9 | 0.5 | 1.6 | 8.2 | |
Min | 0.8 | 2.0 | 0.7 | 1.3 | 0.4 | 0.5 | 2.1 | 0.6 | |
Max | 9.5 | 9.8 | 3.3 | 2.2 | 2.6 | 1.4 | 5.3 | 16.3 | |
Ethylbenzene | Mean | 0.2 | 0.1 | 0.3 | 0.3 | 0.2 | 0.2 | 1.3 | 0.3 |
Std. dev. | 0.2 | 0.1 | 0.1 | 0.1 | 0.1 | 0.1 | 1.8 | 0.2 | |
Min | 0.1 | 0.1 | 0.1 | 0.1 | 0.1 | 0.1 | 0.1 | 0.1 | |
Max | 0.6 | 0.2 | 0.4 | 0.4 | 0.4 | 0.3 | 2.0 | 0.5 | |
Σ Xylenes | Mean | 0.9 | 0.6 | 1.3 | 1.1 | 0.7 | 0.7 | 0.6 | 1.7 |
Std. dev. | 0.9 | 0.1 | 0.6 | 0.4 | 0.6 | 0.4 | 0.3 | 1.3 | |
Min | 0.2 | 0.4 | 0.3 | 0.5 | 0.3 | 0.4 | 0.3 | 0.1 | |
Max | 2.7 | 0.7 | 2.0 | 1.5 | 1.8 | 1.0 | 1.0 | 2.6 | |
Naphthalene | Mean | 0.2 | 0.2 | 0.2 | 0.1 | 0.1 | 0.1 | 0.1 | 0.1 |
Std. dev. | 0.1 | 0.1 | 0.1 | 0.1 | 0.1 | 0.1 | 0.1 | 0.1 | |
Min | 0.1 | 0.2 | 0.1 | 0.1 | 0.1 | 0.1 | 0.1 | 0.1 | |
Max | 0.3 | 0.3 | 0.3 | 0.2 | 0.2 | 0.2 | 0.2 | 0.2 |
The indoor concentrations of benzene ranged from 0.3 µg m−3 to 1.4 µg m−3, and no significant differences in benzene concentration between samples taken in January–February and March–April were found. Like the outdoor concentrations of toluene (see above) there were wide variations in indoor concentrations of toluene, from 0.5 µg m−3 to 16.3 µg m−3. The indoor concentrations of ethylbenzene ranged from 0.1 µg m−3 to 0.5 µg m−3. For the sum of xylenes, the average of the values measured during January–February was 40% lower than the March–April average. The average indoor concentrations of naphthalene ranged from 0.1 µg m−3 to 0.3 µg m−3, and there were no show substantial differences between measurements obtained during the winter and spring periods.
The VOC I/O values at both locations are summarized in Table 6. For benzene, it is apparent that at Location 1 the most significant sources are indoors; the I/O ratios observed in January and April were 1.3 and 2.2, respectively. By contrast, the results from Location 2 indicate that the main sources of benzene are outdoors, with I/O ratios <1 throughout the campaign. For toluene, both the I/O values and the correlation coefficients exhibited a high degree of variability. For ethylbenzene and xylenes the concentrations in the indoor air were almost equal to those in front of the windows, except during the sampling week in April, when evidence of strong indoor sources of all the studied VOCs was detected. Thus, for ethylbenzene and xylenes, the outdoor air determines the indoor air, leading almost to equilibrium between indoor and outdoor air. This conclusion is supported by the high correlation coefficients between indoor and outdoor air concentrations of ethylbenzene and xylenes, as shown in Table 6. The results obtained for toluene, ethylbenzene and xylenes correspond with the findings of German authors (Ilgenet al., 2001).19 The I/O ratios and correlation coefficients for naphthalene exhibited a high degree of variability.
Measurement week | ||||
---|---|---|---|---|
1a | 2b | 3c | 4d | |
a Location 1, winter. b Location 2, winter. c Location 1, spring. d Location, 2 spring. | ||||
Concentration ratio, indoor to outdoor air (I/O) | ||||
Benzene | 1.3 | 0.8 | 0.5 | 2.2 |
Toluene | 3.6 | 1.1 | 0.9 | 1.7 |
Ethylbenzene | 0.9 | 1.1 | 1.0 | 1.7 |
Σ Xylenes | 1.0 | 1.0 | 1.0 | 1.8 |
Naphthalene | 1.8 | 1.1 | 2.6 | 1.3 |
Correlation coefficients between indoor and outdoor air | ||||
Benzene | 0.10 | 0.20 | 0.89 | 0.50 |
Toluene | −0.15 | 0.26 | −0.11 | 0.56 |
Ethylbenzene | 0.87 | 0.57 | 0.68 | 0.95 |
Σ Xylenes | 0.79 | 0.62 | 0.66 | 0.73 |
Naphthalene | −0.88 | 0.41 | 0.52 | 0.66 |
PM2.5/µg m−3 | p-Value of the rank sum test | ||||
---|---|---|---|---|---|
Mean | Median | Russia | Western Europe | Nordic | |
Eastern Europe (9) | 45.7 | 42.0 | 0.0318 | 0.0119 | 0.0464 |
Russia (10) | 27.2 | 23.7 | 0.9575 | 0.4716 | |
Western Europe (6) | 23.3 | 24.9 | 0.8388 | ||
Nordic (13) | 25.5 | 15.4 | |||
Unclassified (5) | 25.3 | 16.8 |
The higher concentrations of PM2.5 on days when the air originated from Eastern Europe were expected because anthropogenic emissions in Eastern Europe are higher than in the other regions. However, no consistent differences in levels of PAHs in air originating from different regions were observed, suggesting that local sources contribute most of the sampled concentrations of the PAHs.
The levels of most PAHs analyzed in this study, especially at Location 1, are notably higher than those reported elsewhere in Europe. The mean sum PAH concentrations at Locations 1 and 2 in the winter campaign were 75.1 ± 32.7 and 32.7 ± 11.8 ng m−3, respectively. The experimental results corroborated the hypotheses that 5–6 and 4-ring PAHs originate from automotive emissions, are bound to street dust and dispersed over the area. Thus, street dust may not only emit fugitive dust, but also be a substantial source of particle-bound PAHs. A trajectory analysis showed that long-range transport is also a source of PM2.5 in the region, but the PAHs within the PM2.5 are of local origin.
VOC concentrations were mostly low and comparable to those reported from Sweden. The mean outdoor concentrations of the VOCs, benzene, toluene, ethylbenzene, sum of m-, p-, o-xylenes, and naphthalene, were: 0.7 ± 0.2, 3.0 ± 0.8, 0.5 ± 0.2, 3.5 ± 0.3 and 0.2 ± 0.1 µg m−3, respectively. The outdoor concentrations of benzene and xylenes measured during January–February sampling campaigns were up to 40% higher than those observed during March–April sampling campaign. Indoor concentrations of benzene did not differ significantly between the January–February and March–April campaigns, but the concentration of xylenes was found to be 40% higher in January–February than in March–April.
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