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F compounds in the atmosphere of Istanbul
Chemosphere 118 (2015) 246–252
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Gas/particle partitioning of PCDD/F compounds in the atmosphere of Istanbul Arslan Saral a, Gulten Gunes b,⇑, Aykut Karadeniz a, Bulent Ilhan Goncaloglu a a b
Yıldız Tekchnical University, Dept. of Environmental Engineering, Davutpasßa Campus, Esenler, Istanbul, Turkey Bartın University, Dept. of Environmental Engineering, Bartın, Turkey
h i g h l i g h t s 92 percent of PCDD/F compounds were detected in a particle phase. Gas/particle ratio of low and high chlorinated congeners showed a seasonal variation.
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Article history: Received 3 May 2014 Received in revised form 3 September 2014 Accepted 11 September 2014 Available online 4 October 2014 Handling Editor: H. Fiedler Keywords: PCDD PCDF Atmospheric sampling Gas/particle partitioning Urban atmosphere
a b s t r a c t Gas/particle partitioning of polychlorinated dibenzo-p-dioxin (PCDD) and polychlorinated dibenzofuran (PCDF) compounds in the ambient atmosphere were investigated at three different sites (urban-indus_ Average gas and particle phase concentrations were measured trial, urban and sub-urban) in Istanbul. as 133 fg m 3 and 1605 fg m 3, respectively. Gas phase concentrations of polychlorinated dibenzo-pdioxin/furan (PCDD/F) compounds were determined to be 128 fg m 3, 50 fg m 3, 153 fg m 3 during summer season and 204 fg m 3, 164 fg m 3, 154 fg m 3 during winter season for the respective three sampling sites. Particle phase concentrations were determined to be 287 fg m 3, 176 fg m 3, 160 fg m 3 during summer and 6586 fg m 3, 2570 fg m 3 and 1861 fg m 3 during winter season for those three sampling sites. Chlorination level and molecular weight of congeners affected gas/particle partitioning of PCDD/F compounds. Gas phase percentages of 2,3,7,8-TCDD and OCDD concentrations were determined to be 47% and 1% respectively. A relatively high correlation was found between total particle matter (TPM) and particle phase PCDD/F concentration during winter season. Ó 2014 Elsevier Ltd. All rights reserved.
1. Introduction Polychlorinated dibenzo-p-dioxin (PCDD) and polychlorinated dibenzofuran (PCDF) compounds are classified as semi-volatile organic compounds (SVOCs) due to their low vapor pressures. Although PCDD/F compounds found both in gas and particle phases in the atmosphere (Hites and Harless, 1991; Hippelein et al., 1996), they generally showed a tendency of existing in particle phase in higher percentages (Turpin et al., 1991; Kurokawa et al., 1998; Lohmann et al., 2000a; Correa et al., 2004; Kadowaki and Naitoh, 2005; Lee et al., 2008). Gas/particle partitioning of these compounds influences their environmental fate and behavior. For example, degradation mechanisms (OH radical reactions and photo degradation) in the gas phase are more effective than in particle phase (Brubaker and Hites, 1997) while atmospheric transport ⇑ Corresponding author. Tel.: +90 212 383 53 68; fax: +90 212 383 53 58. E-mail addresses: [email protected] (A. Saral), [email protected] (G. Gunes), [email protected] (A. Karadeniz), [email protected] (B.I. Goncaloglu). http://dx.doi.org/10.1016/j.chemosphere.2014.09.039 0045-6535/Ó 2014 Elsevier Ltd. All rights reserved.
mechanisms are more important for particle phase (Lohmann and Jones, 1998; Welsch-Pausch and McLachlan, 1998). The factors affecting gas/particle partitioning of SVOCs can be divided into 3 groups: (i) physico-chemical properties of compounds (congeners’ vapor pressures, octanol air coefficients, Henry’s constants, octanol water coefficients, subcooled liquid vapor pressures, molecular weights) (ii) properties of particles (size distribution, organic and elemental carbon contents, particle concentration) (iii) atmospheric conditions (ambient temperature, relative humidity) (Pankow, 1994; Lohmann et al., 2000a; Esen et al., 2008; Vardar et al., 2008). Ambient air temperature and vapor pressure may be stated as the main factors influencing gas/particle partitioning of PCDD/F congeners. Congeners with higher vapor pressures, i.e., less-chlorinated congeners, are generally found in gas phase (Foreman and Bidleman, 1987; Pankow, 1987; Lee et al., 2008). For a given congener, the fraction in gas phase increases with increasing ambient temperature and decreases with increasing particle concentration (Foreman and Bidleman, 1987; Pankow, 1987; Lee et al., 2008).
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Chlorination level and molecular weight are other important properties affecting the gas/particle ratio. Numerous studies have shown that particle phase concentration increases with increasing chlorination level (Eitzer and Hites, 1989; Lee and Jones, 1999; Lohmann et al., 2000a,b; Oh et al., 2001; Park and Kim, 2002; Chao et al., 2004; Correa et al., 2004; Kadowaki and Naitoh, 2005; Li et al., 2007). PM10 (coarse particles) and PM2.5 (fine particles) include inhalable particles that are small enough to penetrate the thoracic region _ of respiratory system (WHO, 2013). The atmosphere of Istanbul is affected by various anthropogenic sources such as industrial combustion processes, motor vehicles, commercial and residential heating processes. Industrial structures produce fine particles from combustion processes (Mishra et al., 2004; Kim et al., 2005) and vehicle emissions are also an important source of PM with a peak diameter of 0.1–0.2 lm (Kleeman et al., 2000). Mishra et al. (2004) reported that the size range of winter season PM gets the lowest values reflecting the fact of increased commercial and residential heating in this season. It has also been reported that the proportions of high chlorinated homologues and concentrations of PCDD/Fs were higher in fine particle sizes (Oh et al., 2002; Lee et al., 2008). In this study, gas/particle partitioning of PCDD/F compounds was investigated at three different regions in Istanbul. In addition, seasonal variations of gas/particle distribution were also monitored for each congener and possible sources of these compounds were estimated.
2. Materials and methods 2.1. Site description Ambient air samples were collected at three different sampling stations in Istanbul which is located on the north-western part of Turkey. Istanbul is a transcontinental city straddling the Bospho-
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rus, one of the world’s busiest waterways connecting the Sea of Marmara and the Black Sea (see Fig. 1). The city has about 14 million population with various anthropogenic activities in the sense of PCDD/F sources such as dense motor vehicle traffic and mixed groups of industrial facilities. Therefore, three different sampling locations were chosen in this study. Davutpasßa sampling region (latitude: 41.02 N; longitude: 28.82 E) involves residential and industrial structures together with Turkey’s biggest intercity bus terminal and foundry industrial zone which are located about 1.5 km NE and 9 km NW of the sampling point, respectively. Yıldız sampling station (latitude: 41.30 N; longitude: 29.00 E) is located in the city center which receives motor vehicle emissions due to dense public transportation and ship emissions from the Bosphorus marine traffic. Fenertepe sampling station (latitude: 41.90 N; longitude: 28.47 E) is located out of the city center and surrounded by large forest area. Although there is no industrial activity in the vicinity of this location, there are medical and hazardous waste incineration plants which are located about 8 km NE and 12 km SE of this sampling station, respectively. 2.2. Sampling and analysis Sampling and analysis were conducted in accordance with the reference method of EPA TO-9A. Gas and particle phase samples were collected simultaneously at three sampling points during May 2011 to May 2013 using high volume sampler. High volume air samplers were operated at 0.225 m3 min 1 flow rate. They were operated for a period of 5–7 d (120–168 h) at each sampling time. High volume samplers were placed at heights of about 10 m, 3 m and 15 m above ground level for Davutpasßa, Yıldız and Fenertepe sampling stations, respectively. Quartz fiber (QF) filters (10 cmdia, retention efficiency of 99.95% for 0.3 lm-particle size) and polyurethane foam (PUF) cylindrical filters (6.0 cm-dia, 8.0 cmthickness) were used for particle and gas phase samplings, respectively. Before sampling, QF filters were conditioned at 450 °C for 5 h and PUF filters were pre-cleaned with acetone in soxhlet
Fig. 1. Location of sampling stations.
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Fig. 2. Gas/particle partitioning of PCDD/F congeners.
extractor for 16 h. Extraction, clean up and fractionation were applied for QF and PUF filters after sampling. PUF and QF filter were extracted separately with toluene for 20 h using soxhlet extractor. After extraction, toluene extract is concentrated in rotary vacuum evaporator, re-dissolved in hexane and pre-cleaned by shaking with 10 mL concentrated sulfuric acid at laboratory temperature. Pre-cleaned hexane extract was transferred on top of multi-layer silica gel column and eluted with hexane. Extract was concentrated with modified Kuderna–Danish concentrator up to 0.5–1 mL. Fractionation is the separation of PCDD/F from other similar structures as a final step of the preparation procedure. 1 g florisil (magnesium silicate) column was used for fractionation and a combination of hexane and dichloromethane was used for the elution of PCDD/F and PCB fractions. Final extract containing PCDD/Fs is concentrated up to dryness under nitrogen stream and then 2-to-4 lL of samples were injected to high-resolution gas chromatography/high-resolution mass spectrometry (HRGC–HRMS, Thermo Gas Chromatograph Trace GC Ultra-HRMS) for the chromatographic analysis of PCDD/F congeners 37Cl-2,3,7,8T4CDD (3 ng) and 13C12-labeled standards (0.2 ng) were used to determine the recovery efficiency of sampling and extraction processes. Recovery values were determined in the ranges of 61–91%
and 60–118% for 13C12 and 37Cl-2,3,7,8 T4CDD, respectively. These values meet the reported sample recoveries of EPA Method TO-9A.
3. Results and discussion 3.1. Gas/particle ratio of PCDD/Fs in the ambient air Concentrations of gas and particle phase PCDD/Fs in the ambient air at three sampling sites were shown in Fig. 2. Although gas/particle partitioning of PCDD/F compounds varies in relation to many factors, PCDD/F compounds generally showed a tendency of existing in particle phase in higher percentages (Turpin et al., 1991; Kurokawa et al., 1998; Lohmann et al., 2000a; Correa et al., 2004; Kadowaki and Naitoh, 2005; Lee et al., 2008). Gas and particle phase concentrations of PCDD congeners were measured to be 19 fg m 3 and 642 fg m 3, respectively; while those for PCDFs were measured to be 114 fg m 3 and 964 fg m 3, respectively. Average concentrations of PCDD/Fs were calculated out of all sampling results as 133 fg m 3 in gas phase and 1605 fg m 3 in particle phase. The average percentages of particle phase concentrations were found to be 97% for PCDD and 89% for PCDF congeners. This
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Fig. 3. Seasonal variation of gas/particle distribution of PCDD/F congener concentrations (fg/m3) for each sampling station.
situation was explained by two main factors in the literature: (i) vapor pressures of PCDD congeners are lower than PCDF congeners (Rordorf, 1989) and (ii) molecular weights of PCDD congeners are higher than PCDF congeners (Mackay et al., 1992). Several previous publications have been reported that the particle phase concentration of PCDD congeners are higher than PCDF congeners (Lee and Jones, 1999; Chao et al., 2004; Correa et al., 2004; Li et al., 2008; Xu et al., 2009). Average gas phase concentrations of PCDD/F compounds at Davutpasßa, Yıldız and Fenertepe sampling stations turned out to be 175 fg m 3, 91 fg m 3 and 133 fg m 3 whereas average particle phase concentrations were as 2881 fg m 3, 1166 fg m 3 and 769 fg m 3, respectively. Although the lowest average concentration was detected for Fenertepe sampling station, the ratio of gas phase concentration to total gas phase concentration (399 fg m 3) at this station was higher than that at Yıldız sampling station. In
addition, the ratio of gas (33%) and particle (16%) phase concentrations to total average concentrations were very different at this sampling station in contrast to Davutpasßa (60% for particle phase, 44% for gas phase) and Yıldız (24% for particle phase, 23% for gas phase) stations. Gas/particle partitioning of PCDD/F congeners were given in Fig. 2. Although particle phase concentrations are dominant, lower chlorinated congeners have the tendency being in gas phase while higher chlorinated ones in particle phase. For example, gas phase ratio of 2,3,7,8-TCDD and OCDD total concentrations were determined to be 47% and 1% respectively. In addition to this, contributions of TCDD and OCDD congeners to total particle phase concentration were found to be 3% and 22%, respectively. This is compatible with the results reported by other researchers (Eitzer and Hites, 1989; Lee and Jones, 1999; Lohmann et al., 2000a; Lohmann et al., 2000b, 2007; Oh et al., 2001; Park and Kim,
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2002; Chao et al., 2004; Correa et al., 2004; Kadowaki and Naitoh, 2005; Li et al., 2007). I-TEQ concentrations of congeners having low chlorination levels were detected to have higher concentrations in gas phase (Fig. 2). For example, respective gas and particle phase ratios of 2,3,4,7,8-PeCDF were found to be 45% and 39%; those of 2,3,7,8TCDD were found to be 10% and 2%; and those of 2,3,7,8-TCDF were found to be 20% and 3%. Since I-TEQ factors of OCDD and OCDF are very small, their contributions to particle phase I-TEQ concentrations were calculated to be 1% and 0.2% while those in gas phase were negligible. 3.2. Seasonal variation of gas/particle partitioning Gas phase concentrations of PCDD/F compounds were determined to be 128 fg m 3, 50 fg m 3, 153 fg m 3 during summer season and 204 fg m 3, 164 fg m 3, 154 fg m 3 during winter season for Davutpasßa, Yıldız, Fenertepe sampling stations, respectively. In addition, particle phase concentrations were determined to be 287 fg m 3, 176 fg m 3, 160 fg m 3 during summer and 6586 fg m 3, 2570 fg m 3 and 1861 fg m 3 during winter season for Davutpasßa, Yıldız and Fenertepe sampling stations, respectively. Gas phase concentrations did not show significant seasonal variations while gas phase ratios showed seasonal variation (Fig. 3). Gas phase ratios were calculated as 31%, 22% and 49% during summer season and 3%, 3%, 8% during winter season for Davutpasa, Yildiz and Fenertepe sampling stations, respectively. Particle phase ratios were calculated as 69%, 78% and 51% during summer season and 97%, 97%, 92% during winter season for Davutpasa, Yildiz and Fenertepe sampling stations, respectively. In spring and autumn seasons, average ratio of particle phase concentration was 92% while gas phase was 8% at Davutpasßa and Yıldız. Fenertepe, on the other hand, has 84% for particle phase and 16% for gas phase contributions. Seasonal variation of gas/particle distribution of congeners was shown in Fig 3. Low and high chlorinated congeners showed a seasonal variation. For example, 2,3,7,8-TCDD was not detected in summer while it has 5% contribution in winter in particle phase. In addition to the gas phase ratio of this congener was detected as about 1% for summer season and this ratio was lower than winter season. Although high chlorinated congeners have the tendency being in particle phase, their gas phase ratios were detected to be higher in summer than in winter. For example, OCDD has 25% in summer, 14% in winter and 1,2,3,4,6,7,8-HPCDF has 49% in summer and 15% in winter as gas phase contributions. These results are consistent with the previous studies which were reported by Kouimtzis et al. (2002), Mandalakis et al. (2002), Lohmann et al. (2000a), Eitzer and Hites (1989), Oh et al. (2001), Chao et al. (2004). Therefore, temperature, vapor pressure, chlorination level and molecular weight were considered to be principal causes of gas/particle distribution of PCDD/F compounds according to the results of this study and previous studies (Foreman and Bidleman, 1987; Pankow, 1987; Lee et al., 2008). Considering the seasonal variation of congeners, gas phase ratio of high chlorinated congeners increased at Fenertepe sampling station in summer (Fig. 3). Highest gas phase values were detected for high chlorinated PCDD/F congeners (1,2,3,4,6,7,8-HpCDD/F, OCDD and OCDF) at Fenertepe sampling station. For example, summer/ winter ratio of 1,2,3,4,6,7,8-HpCDF for gas phase was calculated to be 3.8, 1.6, 12.4 for Davutpasßa, Yıldız and Fenertepe sampling stations while this ratio was calculated to be lower than 1 for particle phase. Interestingly, the lowest average value of summer/winter ratio for gas phase was detected to be 0.6 at Yıldız sampling station while the highest value was detected to be 3.9 for Fenertepe sampling station. Moreover, the ratio of all congeners was detected to be lower than 1 for particle phase. Therefore, it is esti-
mated that Fenertepe sampling station was affected by different emission source or sources except motor vehicles especially at certain times during summer season whereas one source type (strongly motor vehicles) was effective at Yıldız sampling station during all seasons. Highest value for gas/particle ratio was detected to be 0.96 at Fenertepe sampling station during summer season while the lowest values were detected for winter season at all sampling stations. Medical waste incineration plant and gasification plant which are located at respective distances of 8 km NE and 12 km SE of the station and usage of various pesticides (insecticide, herbicide) in the surrounding large forests and agricultural fields are considered to be principal causes of high correlation at Fenertepe sampling station during summer season. Homolog groups showed an increasing trend in gas phase in summer while a similar trend in particle phase in winter (Fig. 4). This result in accordance with the previous studies (Eitzer and Hites, 1989; Lohmann et al., 2000a; Oh et al., 2001; Kouimtzis et al., 2002; Mandalakis et al., 2002; Chao et al., 2004) that it can be explained by several reasons. For instance, vapor pressure that changes directly with temperature affects the gas/particle partitioning of SVOCs (Foreman and Bidleman, 1987; Pankow, 1987). It has been mentioned in Section 1, distribution of semi-volatile organic compounds in a gas and particle phases varies depending on the particle properties, compounds properties and atmospheric conditions (Pankow, 1994; Lohmann et al., 2000a; Esen et al., 2008; Vardar et al., 2008). In addition to adsorption and desorption kinetics show variation between the congeners (Pankow and Bidleman, 1992). For instance, less chlorinated congeners tend to have the gas phase due to high vapor pressures unlike high chlorinated ones (Lohmann et al., 2000a; Oh et al., 2001; Kouimtzis et al., 2002;
Fig. 4. Variations of gas/particle partitioning of homolog groups for summer and winter seasons.
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A. Saral et al. / Chemosphere 118 (2015) 246–252 Table 1 Correlation parameters between TPM and particle phase PCDD/Fs concentration (fg/m3). Davutpasßa
Spring Summer Autumn Winter
Yıldız
Fenertepe
2
TPM
PCDD/F
102 74 97 66
1354 176 691 2703
TPM
PCDD/F
R
R
114 69 69 77
2781 279 2077 7221
0.1 0.68 0.43 0.7
0 0.46 0.18 0.5
Mandalakis et al., 2002; Chao et al., 2004). As a similar previous studies, gas phase ratios of less chlorinated congeners increased during the summer in this study (Fig. 4). Therefore increasing ambient air temperature in summer may cause increase of volatilization and desorption of SVOCs into gas phase while the reverse way transfer of low chlorinated congeners in winter in this study.
3.3. Effect of TPM concentration on gas/particle distribution TPM concentration and physico-chemical properties of particles and congeners are important factors affecting gas/particle distribution of PCDD/F congeners. Average TPM concentrations for Davutpasßa, Yıldız and Fenertepe sampling stations were detected to be 82, 84 and 46 lg m 3, respectively. The values for Davutpasßa and Yıldız are higher than the 24 h limit value (50 lg m 3) reported by WHO (2005). Statistical parameters for the correlation between TPM and particle phase PCDD/F concentrations were given in Table 1. A relatively high correlation was found in all sampling points for winter season. This could be explained by two possible reasons as follows: first, TPM and PCDD/Fs are thought to have the same sources in winter such as fossil fuel consumption for heating purpose in this season. Second reason is the increase in the frequency of unfavorable meteorological conditions such as low ambient temperature, inversions, low mixing height and high pressure. These conditions together may have the potential of parallel increase in TPM and particle phase PCDD/F concentrations. High correlation coefficients were determined for Davutpasßa and Fenertepe sampling stations during the summer season as a similar to the winter season. Therefore it has been estimated that TPM and PCDD/F were emitted together and simultaneously from the source or sources both at Davutpasßa and Fenertepe sampling stations in contrast to Yıldız sampling station especially during summer season. It is expected that the sources of the TPM and PCDD/F are different at Yildiz sampling point. As a result, industrial combustion processes which are used of fossil fuels and solid waste incineration processes are estimated to be TPM and PCDD/ F sources at Davutpasßa and Fenertepe sampling stations during the summer. A positive correlation detected for Davutpasßa station in summer season may be explained by the emissions from industrial facilities surrounding the sampling station. In addition, possible emission sources were reported in Section 3.2 for Fenertepe sampling station. This idea is confirmed by increase of high chlorinated congeners (1,2,3,4,6,7,8-HpCDD/F, OCDD and OCDF) at this station. In addition, no meaningful correlation was detected for spring and autumn seasons. It has been thought that TPM may be generated from different sources, except combustion, such as tree pollens and desert dusts. TPM concentrations were found to be similar to those in summer and autumn seasons while PCDD/F concentrations were very different for those seasons. This case may be explained by seasonal variation of the dominant source types. For instance, motor vehicles are considered to be dominant source of both PCDD/F compounds and TPM in summer season while other TPM sources such as tree polens and long-distance transport of
R
R 0.18 0.21 0.22 0.98
2
0.03 0.04 0.05 0.96
TPM
PCDD/F
R
R2
65 36 29 56
861 160 410 1865
0.16 0.96 0.04 0.9
0.03 0.9 0 0.81
desert dusts. Moreover, fossil fuel used in stationary sources is dominant source for both TPM and PCDD/F compounds in autumn and winter seasons, and it is more effective than motor vehicle usage. Tree pollens which are effective in spring season and weed pollens which are effective in autumn season may be considered as principal cause of negative weak correlation between TPM and particle phase PCDD/F concentrations at Yıldız station. These outcomes reveal that only TPM concentration on itself could not affect the gas/particle partitioning as many researchers reported in the literature (Lee et al., 2007; Li et al., 2008; Xu et al., 2009). 4. Conclusions In this study, gas/particle partitioning of the PCDD/F compounds was investigated at three different areas in the metropoli_ tan city of Istanbul. PCDD/F compounds generally showed a tendency of appearing in particle phase in higher percentages. As the results of all samplings reveal, the percentages of PCDD/Fs in gas and particle phases were detected as 8% and 92%, respectively. Although particle phase concentrations were detected to be dominant, lower chlorinated congeners have the tendency of appearing in gas phase whereas higher chlorinated ones in particle phase. As a result, temperature, vapor pressure, chlorination level and molecular weight were detected to be the most important parameters affecting gas/particle distribution of PCDD/F compounds in accordance with the literature. A relatively high correlation was found between TPM and particle phase PCDD/F concentration in all sampling points for winter season. Fossil fuel consumption for residential and commercial heating purposes in this season was considered to be principal cause of this high correlation. Due to the largest amounts of particle-bound PCDD/Fs on small particles with aerodynamic diameters less than 1.1 lm, investigation of particle size distribution of PCDD/F compounds is suggested to assess the respiratory exposure and to assist local authorities in establishing plans for improving air quality. Acknowledgment This research has been fully supported by the research fund of TUBITAK (Project number: 110Y063) References Brubaker, W.W., Hites, R.A., 1997. Polychlorinated dibenzo-p-dioxins and dibenzofurans: gas-phase hydroxyl radical reactions and related atmospheric removal. Environ. Sci. Technol. 31, 1805–1810. Chao, M.R., Hu, C.W., Chen, Y.L., Chang-Chien, G.P., Lee, W.J., Chang, L.W., Lee, W.S., Wu, K.Y., 2004. Approaching gas–particle partitioning equilibrium of atmospheric PCDD/Fs with increasing distance from an incinerator: measurements and observations on modeling. Atmos. Environ. 38, 1501–1510. Correa, O., Rifai, H., Raun, L., Suarez, M., Koenig, L., 2004. Concentrations and vapor– particle partitioning of polychlorinated dibenzo-p-dioxins and dibenzofurans in ambient air of Houston, TX. Atmos. Environ. 38, 6687–6699. Eitzer, B.D., Hites, R.A., 1989. Polychlorinated dibenzo-p-dioxins and dibenzofurans in the ambient atmospheric of Bloomington, Indiana. Environ. Sci. Technol. 23, 1389–1395. Esen, F., Tasdemir, Y., Vardar, N., 2008. Atmospheric concentrations of PAHs, their possible sources and gas-to-particle partitioning at a residential site of Bursa, Turkey. Atmos. Res. 88, 243–255.
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Gas/particle partitioning of PCDD/F compounds in the atmosphere of Istanbul Arslan Saral a, Gulten Gunes b,⇑, Aykut Karadeniz a, Bulent Ilhan Goncaloglu a a b
Yıldız Tekchnical University, Dept. of Environmental Engineering, Davutpasßa Campus, Esenler, Istanbul, Turkey Bartın University, Dept. of Environmental Engineering, Bartın, Turkey
h i g h l i g h t s 92 percent of PCDD/F compounds were detected in a particle phase. Gas/particle ratio of low and high chlorinated congeners showed a seasonal variation.
a r t i c l e
i n f o
Article history: Received 3 May 2014 Received in revised form 3 September 2014 Accepted 11 September 2014 Available online 4 October 2014 Handling Editor: H. Fiedler Keywords: PCDD PCDF Atmospheric sampling Gas/particle partitioning Urban atmosphere
a b s t r a c t Gas/particle partitioning of polychlorinated dibenzo-p-dioxin (PCDD) and polychlorinated dibenzofuran (PCDF) compounds in the ambient atmosphere were investigated at three different sites (urban-indus_ Average gas and particle phase concentrations were measured trial, urban and sub-urban) in Istanbul. as 133 fg m 3 and 1605 fg m 3, respectively. Gas phase concentrations of polychlorinated dibenzo-pdioxin/furan (PCDD/F) compounds were determined to be 128 fg m 3, 50 fg m 3, 153 fg m 3 during summer season and 204 fg m 3, 164 fg m 3, 154 fg m 3 during winter season for the respective three sampling sites. Particle phase concentrations were determined to be 287 fg m 3, 176 fg m 3, 160 fg m 3 during summer and 6586 fg m 3, 2570 fg m 3 and 1861 fg m 3 during winter season for those three sampling sites. Chlorination level and molecular weight of congeners affected gas/particle partitioning of PCDD/F compounds. Gas phase percentages of 2,3,7,8-TCDD and OCDD concentrations were determined to be 47% and 1% respectively. A relatively high correlation was found between total particle matter (TPM) and particle phase PCDD/F concentration during winter season. Ó 2014 Elsevier Ltd. All rights reserved.
1. Introduction Polychlorinated dibenzo-p-dioxin (PCDD) and polychlorinated dibenzofuran (PCDF) compounds are classified as semi-volatile organic compounds (SVOCs) due to their low vapor pressures. Although PCDD/F compounds found both in gas and particle phases in the atmosphere (Hites and Harless, 1991; Hippelein et al., 1996), they generally showed a tendency of existing in particle phase in higher percentages (Turpin et al., 1991; Kurokawa et al., 1998; Lohmann et al., 2000a; Correa et al., 2004; Kadowaki and Naitoh, 2005; Lee et al., 2008). Gas/particle partitioning of these compounds influences their environmental fate and behavior. For example, degradation mechanisms (OH radical reactions and photo degradation) in the gas phase are more effective than in particle phase (Brubaker and Hites, 1997) while atmospheric transport ⇑ Corresponding author. Tel.: +90 212 383 53 68; fax: +90 212 383 53 58. E-mail addresses: [email protected] (A. Saral), [email protected] (G. Gunes), [email protected] (A. Karadeniz), [email protected] (B.I. Goncaloglu). http://dx.doi.org/10.1016/j.chemosphere.2014.09.039 0045-6535/Ó 2014 Elsevier Ltd. All rights reserved.
mechanisms are more important for particle phase (Lohmann and Jones, 1998; Welsch-Pausch and McLachlan, 1998). The factors affecting gas/particle partitioning of SVOCs can be divided into 3 groups: (i) physico-chemical properties of compounds (congeners’ vapor pressures, octanol air coefficients, Henry’s constants, octanol water coefficients, subcooled liquid vapor pressures, molecular weights) (ii) properties of particles (size distribution, organic and elemental carbon contents, particle concentration) (iii) atmospheric conditions (ambient temperature, relative humidity) (Pankow, 1994; Lohmann et al., 2000a; Esen et al., 2008; Vardar et al., 2008). Ambient air temperature and vapor pressure may be stated as the main factors influencing gas/particle partitioning of PCDD/F congeners. Congeners with higher vapor pressures, i.e., less-chlorinated congeners, are generally found in gas phase (Foreman and Bidleman, 1987; Pankow, 1987; Lee et al., 2008). For a given congener, the fraction in gas phase increases with increasing ambient temperature and decreases with increasing particle concentration (Foreman and Bidleman, 1987; Pankow, 1987; Lee et al., 2008).
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Chlorination level and molecular weight are other important properties affecting the gas/particle ratio. Numerous studies have shown that particle phase concentration increases with increasing chlorination level (Eitzer and Hites, 1989; Lee and Jones, 1999; Lohmann et al., 2000a,b; Oh et al., 2001; Park and Kim, 2002; Chao et al., 2004; Correa et al., 2004; Kadowaki and Naitoh, 2005; Li et al., 2007). PM10 (coarse particles) and PM2.5 (fine particles) include inhalable particles that are small enough to penetrate the thoracic region _ of respiratory system (WHO, 2013). The atmosphere of Istanbul is affected by various anthropogenic sources such as industrial combustion processes, motor vehicles, commercial and residential heating processes. Industrial structures produce fine particles from combustion processes (Mishra et al., 2004; Kim et al., 2005) and vehicle emissions are also an important source of PM with a peak diameter of 0.1–0.2 lm (Kleeman et al., 2000). Mishra et al. (2004) reported that the size range of winter season PM gets the lowest values reflecting the fact of increased commercial and residential heating in this season. It has also been reported that the proportions of high chlorinated homologues and concentrations of PCDD/Fs were higher in fine particle sizes (Oh et al., 2002; Lee et al., 2008). In this study, gas/particle partitioning of PCDD/F compounds was investigated at three different regions in Istanbul. In addition, seasonal variations of gas/particle distribution were also monitored for each congener and possible sources of these compounds were estimated.
2. Materials and methods 2.1. Site description Ambient air samples were collected at three different sampling stations in Istanbul which is located on the north-western part of Turkey. Istanbul is a transcontinental city straddling the Bospho-
247
rus, one of the world’s busiest waterways connecting the Sea of Marmara and the Black Sea (see Fig. 1). The city has about 14 million population with various anthropogenic activities in the sense of PCDD/F sources such as dense motor vehicle traffic and mixed groups of industrial facilities. Therefore, three different sampling locations were chosen in this study. Davutpasßa sampling region (latitude: 41.02 N; longitude: 28.82 E) involves residential and industrial structures together with Turkey’s biggest intercity bus terminal and foundry industrial zone which are located about 1.5 km NE and 9 km NW of the sampling point, respectively. Yıldız sampling station (latitude: 41.30 N; longitude: 29.00 E) is located in the city center which receives motor vehicle emissions due to dense public transportation and ship emissions from the Bosphorus marine traffic. Fenertepe sampling station (latitude: 41.90 N; longitude: 28.47 E) is located out of the city center and surrounded by large forest area. Although there is no industrial activity in the vicinity of this location, there are medical and hazardous waste incineration plants which are located about 8 km NE and 12 km SE of this sampling station, respectively. 2.2. Sampling and analysis Sampling and analysis were conducted in accordance with the reference method of EPA TO-9A. Gas and particle phase samples were collected simultaneously at three sampling points during May 2011 to May 2013 using high volume sampler. High volume air samplers were operated at 0.225 m3 min 1 flow rate. They were operated for a period of 5–7 d (120–168 h) at each sampling time. High volume samplers were placed at heights of about 10 m, 3 m and 15 m above ground level for Davutpasßa, Yıldız and Fenertepe sampling stations, respectively. Quartz fiber (QF) filters (10 cmdia, retention efficiency of 99.95% for 0.3 lm-particle size) and polyurethane foam (PUF) cylindrical filters (6.0 cm-dia, 8.0 cmthickness) were used for particle and gas phase samplings, respectively. Before sampling, QF filters were conditioned at 450 °C for 5 h and PUF filters were pre-cleaned with acetone in soxhlet
Fig. 1. Location of sampling stations.
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Fig. 2. Gas/particle partitioning of PCDD/F congeners.
extractor for 16 h. Extraction, clean up and fractionation were applied for QF and PUF filters after sampling. PUF and QF filter were extracted separately with toluene for 20 h using soxhlet extractor. After extraction, toluene extract is concentrated in rotary vacuum evaporator, re-dissolved in hexane and pre-cleaned by shaking with 10 mL concentrated sulfuric acid at laboratory temperature. Pre-cleaned hexane extract was transferred on top of multi-layer silica gel column and eluted with hexane. Extract was concentrated with modified Kuderna–Danish concentrator up to 0.5–1 mL. Fractionation is the separation of PCDD/F from other similar structures as a final step of the preparation procedure. 1 g florisil (magnesium silicate) column was used for fractionation and a combination of hexane and dichloromethane was used for the elution of PCDD/F and PCB fractions. Final extract containing PCDD/Fs is concentrated up to dryness under nitrogen stream and then 2-to-4 lL of samples were injected to high-resolution gas chromatography/high-resolution mass spectrometry (HRGC–HRMS, Thermo Gas Chromatograph Trace GC Ultra-HRMS) for the chromatographic analysis of PCDD/F congeners 37Cl-2,3,7,8T4CDD (3 ng) and 13C12-labeled standards (0.2 ng) were used to determine the recovery efficiency of sampling and extraction processes. Recovery values were determined in the ranges of 61–91%
and 60–118% for 13C12 and 37Cl-2,3,7,8 T4CDD, respectively. These values meet the reported sample recoveries of EPA Method TO-9A.
3. Results and discussion 3.1. Gas/particle ratio of PCDD/Fs in the ambient air Concentrations of gas and particle phase PCDD/Fs in the ambient air at three sampling sites were shown in Fig. 2. Although gas/particle partitioning of PCDD/F compounds varies in relation to many factors, PCDD/F compounds generally showed a tendency of existing in particle phase in higher percentages (Turpin et al., 1991; Kurokawa et al., 1998; Lohmann et al., 2000a; Correa et al., 2004; Kadowaki and Naitoh, 2005; Lee et al., 2008). Gas and particle phase concentrations of PCDD congeners were measured to be 19 fg m 3 and 642 fg m 3, respectively; while those for PCDFs were measured to be 114 fg m 3 and 964 fg m 3, respectively. Average concentrations of PCDD/Fs were calculated out of all sampling results as 133 fg m 3 in gas phase and 1605 fg m 3 in particle phase. The average percentages of particle phase concentrations were found to be 97% for PCDD and 89% for PCDF congeners. This
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Fig. 3. Seasonal variation of gas/particle distribution of PCDD/F congener concentrations (fg/m3) for each sampling station.
situation was explained by two main factors in the literature: (i) vapor pressures of PCDD congeners are lower than PCDF congeners (Rordorf, 1989) and (ii) molecular weights of PCDD congeners are higher than PCDF congeners (Mackay et al., 1992). Several previous publications have been reported that the particle phase concentration of PCDD congeners are higher than PCDF congeners (Lee and Jones, 1999; Chao et al., 2004; Correa et al., 2004; Li et al., 2008; Xu et al., 2009). Average gas phase concentrations of PCDD/F compounds at Davutpasßa, Yıldız and Fenertepe sampling stations turned out to be 175 fg m 3, 91 fg m 3 and 133 fg m 3 whereas average particle phase concentrations were as 2881 fg m 3, 1166 fg m 3 and 769 fg m 3, respectively. Although the lowest average concentration was detected for Fenertepe sampling station, the ratio of gas phase concentration to total gas phase concentration (399 fg m 3) at this station was higher than that at Yıldız sampling station. In
addition, the ratio of gas (33%) and particle (16%) phase concentrations to total average concentrations were very different at this sampling station in contrast to Davutpasßa (60% for particle phase, 44% for gas phase) and Yıldız (24% for particle phase, 23% for gas phase) stations. Gas/particle partitioning of PCDD/F congeners were given in Fig. 2. Although particle phase concentrations are dominant, lower chlorinated congeners have the tendency being in gas phase while higher chlorinated ones in particle phase. For example, gas phase ratio of 2,3,7,8-TCDD and OCDD total concentrations were determined to be 47% and 1% respectively. In addition to this, contributions of TCDD and OCDD congeners to total particle phase concentration were found to be 3% and 22%, respectively. This is compatible with the results reported by other researchers (Eitzer and Hites, 1989; Lee and Jones, 1999; Lohmann et al., 2000a; Lohmann et al., 2000b, 2007; Oh et al., 2001; Park and Kim,
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2002; Chao et al., 2004; Correa et al., 2004; Kadowaki and Naitoh, 2005; Li et al., 2007). I-TEQ concentrations of congeners having low chlorination levels were detected to have higher concentrations in gas phase (Fig. 2). For example, respective gas and particle phase ratios of 2,3,4,7,8-PeCDF were found to be 45% and 39%; those of 2,3,7,8TCDD were found to be 10% and 2%; and those of 2,3,7,8-TCDF were found to be 20% and 3%. Since I-TEQ factors of OCDD and OCDF are very small, their contributions to particle phase I-TEQ concentrations were calculated to be 1% and 0.2% while those in gas phase were negligible. 3.2. Seasonal variation of gas/particle partitioning Gas phase concentrations of PCDD/F compounds were determined to be 128 fg m 3, 50 fg m 3, 153 fg m 3 during summer season and 204 fg m 3, 164 fg m 3, 154 fg m 3 during winter season for Davutpasßa, Yıldız, Fenertepe sampling stations, respectively. In addition, particle phase concentrations were determined to be 287 fg m 3, 176 fg m 3, 160 fg m 3 during summer and 6586 fg m 3, 2570 fg m 3 and 1861 fg m 3 during winter season for Davutpasßa, Yıldız and Fenertepe sampling stations, respectively. Gas phase concentrations did not show significant seasonal variations while gas phase ratios showed seasonal variation (Fig. 3). Gas phase ratios were calculated as 31%, 22% and 49% during summer season and 3%, 3%, 8% during winter season for Davutpasa, Yildiz and Fenertepe sampling stations, respectively. Particle phase ratios were calculated as 69%, 78% and 51% during summer season and 97%, 97%, 92% during winter season for Davutpasa, Yildiz and Fenertepe sampling stations, respectively. In spring and autumn seasons, average ratio of particle phase concentration was 92% while gas phase was 8% at Davutpasßa and Yıldız. Fenertepe, on the other hand, has 84% for particle phase and 16% for gas phase contributions. Seasonal variation of gas/particle distribution of congeners was shown in Fig 3. Low and high chlorinated congeners showed a seasonal variation. For example, 2,3,7,8-TCDD was not detected in summer while it has 5% contribution in winter in particle phase. In addition to the gas phase ratio of this congener was detected as about 1% for summer season and this ratio was lower than winter season. Although high chlorinated congeners have the tendency being in particle phase, their gas phase ratios were detected to be higher in summer than in winter. For example, OCDD has 25% in summer, 14% in winter and 1,2,3,4,6,7,8-HPCDF has 49% in summer and 15% in winter as gas phase contributions. These results are consistent with the previous studies which were reported by Kouimtzis et al. (2002), Mandalakis et al. (2002), Lohmann et al. (2000a), Eitzer and Hites (1989), Oh et al. (2001), Chao et al. (2004). Therefore, temperature, vapor pressure, chlorination level and molecular weight were considered to be principal causes of gas/particle distribution of PCDD/F compounds according to the results of this study and previous studies (Foreman and Bidleman, 1987; Pankow, 1987; Lee et al., 2008). Considering the seasonal variation of congeners, gas phase ratio of high chlorinated congeners increased at Fenertepe sampling station in summer (Fig. 3). Highest gas phase values were detected for high chlorinated PCDD/F congeners (1,2,3,4,6,7,8-HpCDD/F, OCDD and OCDF) at Fenertepe sampling station. For example, summer/ winter ratio of 1,2,3,4,6,7,8-HpCDF for gas phase was calculated to be 3.8, 1.6, 12.4 for Davutpasßa, Yıldız and Fenertepe sampling stations while this ratio was calculated to be lower than 1 for particle phase. Interestingly, the lowest average value of summer/winter ratio for gas phase was detected to be 0.6 at Yıldız sampling station while the highest value was detected to be 3.9 for Fenertepe sampling station. Moreover, the ratio of all congeners was detected to be lower than 1 for particle phase. Therefore, it is esti-
mated that Fenertepe sampling station was affected by different emission source or sources except motor vehicles especially at certain times during summer season whereas one source type (strongly motor vehicles) was effective at Yıldız sampling station during all seasons. Highest value for gas/particle ratio was detected to be 0.96 at Fenertepe sampling station during summer season while the lowest values were detected for winter season at all sampling stations. Medical waste incineration plant and gasification plant which are located at respective distances of 8 km NE and 12 km SE of the station and usage of various pesticides (insecticide, herbicide) in the surrounding large forests and agricultural fields are considered to be principal causes of high correlation at Fenertepe sampling station during summer season. Homolog groups showed an increasing trend in gas phase in summer while a similar trend in particle phase in winter (Fig. 4). This result in accordance with the previous studies (Eitzer and Hites, 1989; Lohmann et al., 2000a; Oh et al., 2001; Kouimtzis et al., 2002; Mandalakis et al., 2002; Chao et al., 2004) that it can be explained by several reasons. For instance, vapor pressure that changes directly with temperature affects the gas/particle partitioning of SVOCs (Foreman and Bidleman, 1987; Pankow, 1987). It has been mentioned in Section 1, distribution of semi-volatile organic compounds in a gas and particle phases varies depending on the particle properties, compounds properties and atmospheric conditions (Pankow, 1994; Lohmann et al., 2000a; Esen et al., 2008; Vardar et al., 2008). In addition to adsorption and desorption kinetics show variation between the congeners (Pankow and Bidleman, 1992). For instance, less chlorinated congeners tend to have the gas phase due to high vapor pressures unlike high chlorinated ones (Lohmann et al., 2000a; Oh et al., 2001; Kouimtzis et al., 2002;
Fig. 4. Variations of gas/particle partitioning of homolog groups for summer and winter seasons.
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A. Saral et al. / Chemosphere 118 (2015) 246–252 Table 1 Correlation parameters between TPM and particle phase PCDD/Fs concentration (fg/m3). Davutpasßa
Spring Summer Autumn Winter
Yıldız
Fenertepe
2
TPM
PCDD/F
102 74 97 66
1354 176 691 2703
TPM
PCDD/F
R
R
114 69 69 77
2781 279 2077 7221
0.1 0.68 0.43 0.7
0 0.46 0.18 0.5
Mandalakis et al., 2002; Chao et al., 2004). As a similar previous studies, gas phase ratios of less chlorinated congeners increased during the summer in this study (Fig. 4). Therefore increasing ambient air temperature in summer may cause increase of volatilization and desorption of SVOCs into gas phase while the reverse way transfer of low chlorinated congeners in winter in this study.
3.3. Effect of TPM concentration on gas/particle distribution TPM concentration and physico-chemical properties of particles and congeners are important factors affecting gas/particle distribution of PCDD/F congeners. Average TPM concentrations for Davutpasßa, Yıldız and Fenertepe sampling stations were detected to be 82, 84 and 46 lg m 3, respectively. The values for Davutpasßa and Yıldız are higher than the 24 h limit value (50 lg m 3) reported by WHO (2005). Statistical parameters for the correlation between TPM and particle phase PCDD/F concentrations were given in Table 1. A relatively high correlation was found in all sampling points for winter season. This could be explained by two possible reasons as follows: first, TPM and PCDD/Fs are thought to have the same sources in winter such as fossil fuel consumption for heating purpose in this season. Second reason is the increase in the frequency of unfavorable meteorological conditions such as low ambient temperature, inversions, low mixing height and high pressure. These conditions together may have the potential of parallel increase in TPM and particle phase PCDD/F concentrations. High correlation coefficients were determined for Davutpasßa and Fenertepe sampling stations during the summer season as a similar to the winter season. Therefore it has been estimated that TPM and PCDD/F were emitted together and simultaneously from the source or sources both at Davutpasßa and Fenertepe sampling stations in contrast to Yıldız sampling station especially during summer season. It is expected that the sources of the TPM and PCDD/F are different at Yildiz sampling point. As a result, industrial combustion processes which are used of fossil fuels and solid waste incineration processes are estimated to be TPM and PCDD/ F sources at Davutpasßa and Fenertepe sampling stations during the summer. A positive correlation detected for Davutpasßa station in summer season may be explained by the emissions from industrial facilities surrounding the sampling station. In addition, possible emission sources were reported in Section 3.2 for Fenertepe sampling station. This idea is confirmed by increase of high chlorinated congeners (1,2,3,4,6,7,8-HpCDD/F, OCDD and OCDF) at this station. In addition, no meaningful correlation was detected for spring and autumn seasons. It has been thought that TPM may be generated from different sources, except combustion, such as tree pollens and desert dusts. TPM concentrations were found to be similar to those in summer and autumn seasons while PCDD/F concentrations were very different for those seasons. This case may be explained by seasonal variation of the dominant source types. For instance, motor vehicles are considered to be dominant source of both PCDD/F compounds and TPM in summer season while other TPM sources such as tree polens and long-distance transport of
R
R 0.18 0.21 0.22 0.98
2
0.03 0.04 0.05 0.96
TPM
PCDD/F
R
R2
65 36 29 56
861 160 410 1865
0.16 0.96 0.04 0.9
0.03 0.9 0 0.81
desert dusts. Moreover, fossil fuel used in stationary sources is dominant source for both TPM and PCDD/F compounds in autumn and winter seasons, and it is more effective than motor vehicle usage. Tree pollens which are effective in spring season and weed pollens which are effective in autumn season may be considered as principal cause of negative weak correlation between TPM and particle phase PCDD/F concentrations at Yıldız station. These outcomes reveal that only TPM concentration on itself could not affect the gas/particle partitioning as many researchers reported in the literature (Lee et al., 2007; Li et al., 2008; Xu et al., 2009). 4. Conclusions In this study, gas/particle partitioning of the PCDD/F compounds was investigated at three different areas in the metropoli_ tan city of Istanbul. PCDD/F compounds generally showed a tendency of appearing in particle phase in higher percentages. As the results of all samplings reveal, the percentages of PCDD/Fs in gas and particle phases were detected as 8% and 92%, respectively. Although particle phase concentrations were detected to be dominant, lower chlorinated congeners have the tendency of appearing in gas phase whereas higher chlorinated ones in particle phase. As a result, temperature, vapor pressure, chlorination level and molecular weight were detected to be the most important parameters affecting gas/particle distribution of PCDD/F compounds in accordance with the literature. A relatively high correlation was found between TPM and particle phase PCDD/F concentration in all sampling points for winter season. Fossil fuel consumption for residential and commercial heating purposes in this season was considered to be principal cause of this high correlation. Due to the largest amounts of particle-bound PCDD/Fs on small particles with aerodynamic diameters less than 1.1 lm, investigation of particle size distribution of PCDD/F compounds is suggested to assess the respiratory exposure and to assist local authorities in establishing plans for improving air quality. Acknowledgment This research has been fully supported by the research fund of TUBITAK (Project number: 110Y063) References Brubaker, W.W., Hites, R.A., 1997. Polychlorinated dibenzo-p-dioxins and dibenzofurans: gas-phase hydroxyl radical reactions and related atmospheric removal. Environ. Sci. Technol. 31, 1805–1810. Chao, M.R., Hu, C.W., Chen, Y.L., Chang-Chien, G.P., Lee, W.J., Chang, L.W., Lee, W.S., Wu, K.Y., 2004. Approaching gas–particle partitioning equilibrium of atmospheric PCDD/Fs with increasing distance from an incinerator: measurements and observations on modeling. Atmos. Environ. 38, 1501–1510. Correa, O., Rifai, H., Raun, L., Suarez, M., Koenig, L., 2004. Concentrations and vapor– particle partitioning of polychlorinated dibenzo-p-dioxins and dibenzofurans in ambient air of Houston, TX. Atmos. Environ. 38, 6687–6699. Eitzer, B.D., Hites, R.A., 1989. Polychlorinated dibenzo-p-dioxins and dibenzofurans in the ambient atmospheric of Bloomington, Indiana. Environ. Sci. Technol. 23, 1389–1395. Esen, F., Tasdemir, Y., Vardar, N., 2008. Atmospheric concentrations of PAHs, their possible sources and gas-to-particle partitioning at a residential site of Bursa, Turkey. Atmos. Res. 88, 243–255.
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