Environ Sci Pollut Res (2014) 21:3920–3935 DOI 10.1007/s11356-013-2353-y
RESEARCH ARTICLE
Air–soil exchange of PCBs: levels and temporal variations at two sites in Turkey Didem Yolsal & Güray Salihoglu & Yücel Tasdemir
Received: 31 July 2013 / Accepted: 7 November 2013 / Published online: 29 November 2013 # Springer-Verlag Berlin Heidelberg 2013
Abstract Seasonal distribution of polychlorinated biphenyls (PCBs) at the air–soil intersection was determined for two regions: one with urban characteristics where traffic is dense (BUTAL) and the other representing the coastal zone (Mudanya). Fifty-one air and soil samples were simultaneously collected. Total PCB (Σ82 PCB) levels in the soil samples collected during a 1-year period ranged between 105 and 7,060 pg/g dry matter (dm) (BUTAL) and 110 and 2,320 pg/g dm (Mudanya). Total PCB levels in the gaseous phase were measured to be between 100 and 910 pg/m3 (BUTAL) and 75 and 1,025 pg/m3 (Mudanya). Variations in the concentrations were observed depending on the season. Though the PCB concentrations measured in the atmospheres of both regions in the summer months were high, they were found to be lower in winter. However, while soil PCB levels were measured to be high at BUTAL during summer months, they were found to be high during winter months in Mudanya. The direction and amount of the PCB movement were determined by calculating the gaseous phase change fluxes at air–soil intersection. While a general PCB movement from soil to air was found for BUTAL, the PCB movement from air to soil was calculated for the Mudanya region in most of the sampling events. During the warmer seasons PCB movement towards the atmosphere was observed due to evaporation from the soil. With decreases in the temperature, both decreases in the number of PCB congeners occurring in the air and a change in the direction of some congeners were observed, Responsible editor: Leif Kronberg Electronic supplementary material The online version of this article (doi:10.1007/s11356-013-2353-y) contains supplementary material, which is available to authorized users. D. Yolsal : G. Salihoglu : Y. Tasdemir (*) Department of Environmental Engineering, Faculty of Engineering, Uludag University, 16059 Nilüfer, Bursa, Turkey e-mail: [email protected]
possibly caused by deposition from the atmosphere to the soil. 3-CB and 4-CB congeners were found to be dominant in the atmosphere, and 4-, 5-, and 6-CBs were found to dominate in the surface soils. Keywords Flux . Movement . Congeners . Temperature . Season
Introduction Persistent organic pollutants (POPs) are organic compounds of anthropogenic origin that can remain in nature without decomposing for long periods due to their resistance against photolytic, chemical, and biological decay. Polychlorinated biphenyl (PCB) compounds constitute a group that falls under the 12 groups of contaminants called POPs and has nonpolar features. Theoretically, 209 different PCB congeners exist (Carpenter 1998). PCBs threaten human health by accumulating in the food chain due to their lipophilic features and chemical stability (Lilienthal et al. 2000). The ability of PCBs to accumulate in non-polar matrices is relatively high (McIntyre and Lester 1982). Soils and sediments are the primary media for accumulation (WHO 1993). For these pollutants, the atmosphere acts as the most effective transfer medium, and the terrestrial soils act as the most significant receptive medium (Hippelein and McLachlan 1998). Once it was established that PCBs enter the food chain, cause environmental pollution, and threaten human health, their production was banned in many countries around the world and their use was restricted (Carpenter 1998). In Turkey, PCB usage in industries was restricted in 1973, and their use in open systems was completely prohibited on January 1st, 1996 (RCHC 1993). After the restriction of PCB production and usage, its emission into the atmosphere
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decreased in the 1970s and towards the end of the 1980s (Harner et al. 1995). However, the accumulation of PCBs in the soil until its prohibition had become so high that PCB movement from the soil to the air began as the atmospheric concentrations decreased (Harner et al. 1995). It is known that these substances can still be found in all phases and constitute a serious environmental problem. Determining the concentrations of these contaminant types in the air and soil and the exchange at the air/soil intersection provide significant contribution toward identifying the human health risks that PCBs may cause. The purpose of this study was (1) to determine the air and soil PCB concentrations, (2) to calculate the dry deposition and air/soil gas exchange fluxes, and (3) to investigate the direction of the PCB movement, in Bursa, and industrial city in Turkey. To reach these aims, studies were conducted by measuring the simultaneously collected air and soil samples at a high-traffic location, and a coastal location in the city, the Mudanya region. The movement of PCBs from the atmosphere to the soil occurs through dry and wet depositions and diffusion (Backe et al. 2004). Harner et al. (1995) reported that diffused transportation is the major process that determines the air–soil–air exchange. Diffused transportation is governed by the chemical potential between the soil and the atmosphere and is defined by the equilibrium distribution coefficient K SA (nondimensional) of a contaminant between the air and soil (Hippelein and McLachlan 1998), as shown in Eq. 1: K SA ¼ C S ρs =C A
ð1Þ
where C S indicates the contaminant concentration in the soil (pg/g dry weight), ρ S indicates the soil density (g/cm3), and C A indicates the contaminant concentration in the gaseous phase (pg/m3). K SA is dependent on temperature, moisture, and soil characteristics (Meijer et al. 2003). The octanol–air distribution coefficient (K OA) is used as a basic variable that explains the chemical distribution between the atmosphere and organic phases (Harner et al. 2001). Hippelein and McLachlan (1998) related K SA with K OA, the organic carbon fraction of the soil (f OC), and the soil density (ρ S): K SA ¼ 0:411 ρS f OC K OA
ð2Þ
K OA ¼ K OW =K H
ð3Þ
K H ¼ expð−ΔH H =RT þ ΔS H =RÞ
ð4Þ
The factor 0.411 depends on the correlation between K SA and K OA (Hippelein and McLachlan 1998; Bidleman and Leone 2004). Hansen et al. (1999) reported the octanol–water
distribution coefficients (K OW), while Bamford et al. (2000) reported ΔH H (measured enthalpy) and ΔS H (entropy) values, which are used to calculate the Henry law constant (K H) for each PCB congener. The ideal gas constant R is 8, 314 J/mol K, and the temperature T (K) is the soil temperature for each sample.
Materials and methods Sample collection Sampling was conducted between July 2008 and June 2009 at BUTAL and Mudanya regions of Bursa city in Turkey. Air and soil samples were collected concurrently from two regions, BUTAL and Mudanya, two or three times in a month during 1 year. One sample was collected per matrix each sampling date. Fifty air and soil sample pairs were collected from these two sites during the sampling campaign. BUTAL (N 40°11′54′′, E 29°02′55′′) is located at the Merinos junction on Ankara-İzmir Road. This region, where traffic is dense, is also located at the city center. Near the BUTAL sampling location, there are textile, automotive, leather, and marble processing industries, business firms, and repair shops. The region represents pollution originating from industries, albeit at low levels. Additionally, the Nilüfer Creek, where some industrial and domestic wastewater is discharged, surrounds the sampling region. Mudanya (N 40°22′24.76′′, E 28°52′ 42.85′′), however, is located on the coastline of the Marmara Sea. Industry is not developed within the boundaries of this region, though some small- and large-scale olive processing facilities exist in Mudanya. The Marmara Sea is surrounded by regions where numerous industries exist. The neighboring cities, İstanbul (distance to Mudanya, ∼70 km) and Kocaeli (∼90 km) host several petroleum, organic chemistry, pharmaceuticals, food, fertilizer, metal, paint, and shipyard industries. Closer neighboring cities, Gemlik (∼23 km) has various factories such as olive, oil, soap, fertilizer, steel, sheet iron, and chemical industries, and Bursa (∼20 km) hosts several automotive, textile, machine, and food industries. The samples in the gaseous phase were collected from the air using a high-volume air sampler (HVAS) (Thermo Andersen GPS 11 Model, USA), utilizing polyurethane foam (PUF) and filter units. The filters and PUFs were wrapped in aluminum foil and brought to the laboratory in airtight plastic bags. In BUTAL region, HVAS was placed on a platform approximately 2.5 m high, and in Mudanya region, HVAS was placed on the roof of a three story building (∼15 m). Average air volumes collected were 277±15 m3 and 191± 60 m3 for BUTAL and Mudanya, respectively. Dry deposition samples were obtained using a wet–dry deposition sampler (WDDS). The WDDS consists of two compartments made of stainless steel. In the first compartment, dry deposition
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samples are collected on the days without rain, and wet deposition samples from rainy days are collected in the second compartment (Günindi and Tasdemir 2010). Soil samples were obtained from the ground under a tree in the BUTAL garden, located in an area that is not subject to foot traffic, approximately 4 m from the roadside. In Mudanya, the soil samples were obtained from a sloping field adjacent to the building where HVAS was located, that contains olive trees and is close to the roadside, which does not have a large volume of traffic. The soil samples were collected from at least five different points within an area of 10 m2 from a depth of 0–5 cm in the surface soil. The samples were homogeneously mixed. Approximately 150 g of soil was collected for each sample. Large stones and plants were removed from these samples. The soil samples without grinding and drying were wrapped in aluminum foil, placed in airtight plastic bags, and brought to the laboratory. The soil and air samples were prepared for analysis without subjecting them to contamination. Blank samples were obtained from each region along with the samples. These samples were collected by leaving the mouth of a bottle containing 10 g of clean sodium sulfate open for the duration of the sampling. Meteorological parameters such as weather temperature, soil temperature, and humidity were measured during the sampling process. Samples were collected on non-rainy days, and some setbacks and delays occurred in the sampling schedule, especially during rainy periods. Sample preparation and analysis Air samples were passed through a GFF and then through PUF cartridge. After sampling, the PUF cartridges were extracted in the Soxhlet extractor with 1:4 (v/v) DCM/PE mixture. The soil samples (10 g) were placed in ultrasonic baths twice for 30 min each after the addition of 20 mL of a 1:1 DCM/PE mixture (Salihoglu et al. 2011). The sample was filtered using filter paper after the bathing process. The vial and filter were rinsed with 10 mL DCM/PE and this was added to the pooled extracted solvents. Extracts were passed through a sodium sulfate column to remove any residual water. The sample volume was reduced using a rotary evaporator and high-purity N2, and a hexane exchange was performed. The 2 mL sample was cleaned by passing it through a glass column containing 3 g of silicic acid (deactivated with 100 μL pure water), 2 g of alumina (deactivated with 120 μL of pure water), and 1 cm of height sodium sulfate (Tasdemir et al. 2005; Cindoruk et al. 2007; Bozlaker et al. 2008). PCBs were eluted with 25 mL of PE. The volume of the PCB samples was reduced to 2 mL using pure nitrogen gas. One milliliter of H2SO4 was added to the remaining ∼2 mL extract to eliminate sulfur in the soil samples (Batterman et al. 2009; Meijer et al.
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2002). After mixing the liquid thoroughly, it was centrifuged for a few minutes (Tasdemir et al. 2005; Cindoruk et al. 2007). The top layer of the sample including PCBs in HEX was removed carefully with a pipette. Half a milliliter of hexane was added to the acid twice to rinse and remove the any residual PCBs and this hexane was added to the sample. It was very important not to collect any acid (the bottom layer which was darker in color) because it could ruin the capillary column if injected to gas chromatograph (GC). This step removes all other soluble and probable problem causing organic compounds before GC analysis. After a final blowdown to 1 mL by N2 gas the sample was ready for injection. Samples that were ready for chromatographic analysis after the processes of extraction, volume reduction, and fractionation were kept in a deep freeze of −20 °C. Quantification of PCB congeners were conducted using a HP 7890A GC-μECD (Mikro-Electron Capture Detector; HewlettPackard, USA). The temperature program used in PCB analysis was as follows: 70 °C (2 min), with 25 °C/min to 150 °C, with 3 °C/min to 200 °C, with 8 °C/min reaching 280 °C and holding at 280 °C for 8 min, and with 10 °C/min reaching 300 °C and holding for 2 min. The inlet temperature was held at 250 °C and the detector temperature was 320 °C. Helium, the carrier gas (1.9 mL/min), was used with a makeup gas of high-purity nitrogen. Splitless (after 1 min, a separation vane was opened) injection was used with purge flow of 25 mL/min. A HP5-MS capillary column (30 m×0.32 mm× 0.25 μm; Agilent 19091J-413) was used. Five levels of standard solution between 0.05 and 25 ng/mL were used for calibration. The r 2 for each of the 83 PCB congeners was obtained over 0.99. System performance was verified by the analysis of the midpoint calibration standard after injection of 25 samples. The instrument detection limit was determined as 0.1 pg for an injection of 1 μL. The total organic carbon (TOC) contents of the soils were measured using the SSM-5000 module of Shimadzu TOC Analyzers TOC-VCPN, according to the 5310 B method listed in the Standard Methods. The mean organic carbon fraction was determined to be 2.0±0.7 % in BUTAL and 1.1±0.7 % in Mudanya. The soil density was measured to be 1.49 g/cm3 in the BUTAL region and 1.48 g/cm3 in Mudanya. Quality control and quality assurance The 82 PCB congeners investigated in the two regions were PCB# 4, 5, 6, 7, 8, 9, 10, 12, 13, 15, 16, 17, 19, 21, 22, 26, 28, 31, 32, 37, 41, 42, 44, 45, 47, 48, 49, 52, 53, 56, 60, 61, 64, 66, 70, 71, 74, 77, 81, 83, 84, 86, 87, 89, 91, 92, 95, 99, 100, 101, 105, 110, 114, 118, 119, 123, 126, 128, 131, 132, 135, 138, 144, 149, 153, 156, 163, 167, 169, 170, 171, 172, 174, 180, 190, 194, 199, 200, 202, 205, 206, and 207. Aluminum foil and Teflon materials were used during the collection of the samples, transportation to the laboratory, and storage.
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Glassware products used in the laboratory were first washed with tap water; then passed through pure water, methanol (MeOH), and DCM; and finally dried. After drying, they were wrapped with aluminum foil to prevent air contact. Surrogate standards were used to calculate the analytic efficiency of the samples, in other words, the losses that could occur during the analysis procedure. Approximately 4 ng/mL each of the congeners PCB# 14 (3,5-dichlorophibenyl), 65 (2, 3,5,6-tetrachlorophibenyl), and 166 (2,3,4,4′,5,6hexachlorophibenyl) were added to the samples. The average efficiency (%) values in the soil and air samples are given in Table 1. Prior to GC μ-ECD injection, 2 ng/μL of the internal standard (volume determinant) was added to each bottle. The standards of PCB# 30 (2,4,6 trichlorophibenyl) and 204 (2,2′, 3,4,4′,5,6,6′-octachlorobiphenyl) were used to determine the volume efficiency of the specimen in the sample bottle. Blank samples were collected to determine whether any contamination occurred after sampling. The limit of detection (LOD) value was obtained by taking the average of each PCB level (ng) measured in the blank samples and adding the standard deviation multiplied by 3 (LOD=avg.+3×SD). If the PCB congeners were greater than the LOD values in the samples, these were reported in the calculations. Furthermore, each sample was subjected to blank sample correction.
Results and discussion Soil and air concentrations in BUTAL region The total concentrations of PCBs found in the atmosphere and soils of BUTAL region are shown in Fig. 1a. The average PCB concentration in the gaseous phase in the atmosphere of the BUTAL region was found to be 360±210 pg/m3. The PCB levels measured in the urban atmosphere in this study were found to be both lower and higher than some other regions (Yeo et al. 2004; Tasdemir et al. 2004). Researchers have reported PCB levels ranging between 21 and 1,820 pg/m3 (Tasdemir et al. 2004) in the atmosphere. Some seasonal variations were observed in the PCB concentrations. The Table 1 Average recovery efficiencies for the samples (%)
BUTAL Soil samples PCB# 14 65±21 PCB# 65 66±24 PCB# 166 66±24 Air samples (PUF) PCB# 14 56±18 PCB# 65 57±17 PCB# 166 69±19
Mudanya
67±23 76±24 63±20 62±21 63±19 74±24
PCB levels, which varied between 225 and 830 pg/m3 (average 430±210 pg/m3) during the summer season, were determined to range between 230 and 910 pg/m3 (480±270 pg/m3) during autumn, 125 and 580 pg/m3 (335±195 pg/m3) during winter, and 100 and 415 pg/m3 (250±135 pg/m3) during spring. While high PCB concentrations were observed at the BUTAL region during the summer and autumn months, lower levels were observed during the winter months. The average PCB concentration measured in the soil samples collected from the BUTAL region was determined to be 2,010±1, 735 pg/g dm (26 samples). The total PCB levels detected in the BUTAL soils varied between 480 and 7,060 pg/g dm (summer), 265 and 5,370 pg/g dm (autumn), 105 and 1, 270 pg/g dm (winter), and 475 and 2,585 pg/g dm (spring). The average soil PCB concentrations were determined to be 2, 425 ± 2,060 pg/g dm (summer), 3,525 ± 2,055 pg/g dm (autumn) 625 ± 485 pg/g dm (winter), and 1,415 ± 720 pg/g dm (spring). The PCB levels found in the BUTAL soils fall at the lower end of the range of soil levels reported for various locations around the globe (Ren et al. 2007; Wilcke et al. 1999). The distributions and levels of PCB pollution in the soils of several urban, rural, and industrial regions are given in Table 2. Table 3 gives the variability in the levels of PCB congeners measured both in the atmosphere and soils of the regions investigated. Most of the 82 PCB congeners investigated were encountered in BUTAL’s atmosphere, and PCB# 81/87, 194, 205, and 206 were not detected. The ten PCB congeners/pairs with the highest concentrations (PCB# 4/10, 12/13, 16/32, 19, 21, 28, 31, 44, 49/48, and 52) accounted for 56.7 % of the average concentration in the BUTAL’s atmosphere. The largest groups among the homolog groups in the BUTAL atmosphere were found to be 3-CBs 38 % and 4-CBs 26 %.The industries, residential areas, evaporations from Nilüfer Creek, which is contaminated by wastewaters, and atmospheric transportation can be considered as possible PCB sources in the regional atmosphere. Among the 82 PCB congeners investigated, only PCB# 16/ 32, 131, 135/144, 167, 205, and 207 were not encountered in the soils of BUTAL region (Table 3). The ten PCB congeners/ pairs in the BUTAL region soils with the highest concentrations were determined to be PCB# 4/10, 84, 114/149, 123, 128, 153, 163/138, 169, 174, and 180. These congeners amount to 44.1 % of the average PCB concentration in BUTAL’s soils. Figure 2 shows the seasonal homolog group distributions in the soils of the two regions investigated. In BUTAL, the largest group consisted of 5-CBs with a percentage of 28.4 %, and the others were found to be as follows: 2CBs (6.5 %), 3-CBs (8.2 %), 4-CBs (20 %), 6-CBs (23.0 %), 7-CBs (11.4 %), 8-CBs (2.4 %), and 9-CBs (0.03 %). This distribution displays similarities to other studies in the literature (Aichner et al. 2007; Ren et al. 2007; Lead et al. 1997; Zhang et al. 2007b). Homolog distributions varied depending
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Fig. 1 PCB levels measured in the atmosphere and soils of a BUTAL region b Mudanya region
on the season (Fig. 2). While 5-CBs were dominant during the summer and autumn seasons in BUTAL region, 4-CBs and 6CBs were found to be higher during the winter and summer months. The soil levels of homolog groups measured in summer and autumn months were found to be statistically higher than that of winter months (paired samples test, p < 0.05; Table S1). General expectation would be lower PCB levels in warmer seasons due to evaporation, which is just the opposite situation observed in BUTAL. Possible reason might be the influence of local industries in the region dominating the seasonal effects. A significant correlation was observed between the air and soil PCB concentrations measured at the BUTAL region (R 2 =0.39, p 6-CBs> 7-CBs>3-CBs>8-CBs (Fig. 2). It was seen that soils of Mudanya region has a lower rate of high-molecular-weight (7-, 8-, and 9-CB) PCBs compared to the BUTAL region. Possible explanation could be the location of BUTAL region, which is closer to the industry and other sources; therefore, the heavy PCB congeners could have been deposited near their source. However, industrial settlement in Mudanya is not as developed as in BUTAL, and the soils were not as polluted as that of BUTAL soils. The PCB levels measured in the soils of Mudanya region in winter were found to be higher than that of summer and autumn (paired samples test, p 0.50, Mudanya) for either region.
Conclusions In this study, the PCB levels in the soils and in the air were measured at two different regions of Bursa city, BUTAL, a location consisting of local industries, and Mudanya, a location on the coastline of the Marmara Sea.
3-CBs and 4-CBs were found to be dominating in BUTAL atmosphere while the largest group in the soils was found to be 5-CBs. Seasonal variations were observed in terms of PCB levels. The soil PCB levels measured in summer and autumn months were found to be statistically higher than that of winter months in BUTAL region. General expectation would be lower PCB levels in warmer seasons due to evaporation, which is just the opposite situation observed in BUTAL. Possible reason might be the influence of local industries in the region dominating the seasonal effects. A significant correlation was observed between the air and soil PCB concentrations measured at this region inferring that both the atmosphere and soils of the region were influenced by the same sources. Atmospheric PCB levels in Mudanya were found to be comparable to that of BUTAL region although industry is not developed within the boundaries of this region. Possible reasons suggested were the influence of Marmara Sea and the industrial activities at the neighboring cities. The PCB levels measured in the soils of Mudanya region in winter were found to be higher than that of summer and autumn, as opposite to the situation in BUTAL. This implied possible evaporation from the soil into the air, thus causing a reduction in the soil PCB levels. Soil PCB levels of Mudanya were statistically lower than that of BUTAL region although no significant difference was determined between the air PCB levels of Mudanya and that of BUTAL. In BUTAL region, low-molecular-weight congeners were generally observed to move from soil to air and highmolecular-weight congeners transferred from air to soil. The number of PCB congeners detected in the soils of this region decreased as air temperature decreased. In Mudanya region, the PCB congeners generally had a tendency to move from air to soil. Thus, in Mudanya, the soil was the receptive medium and the air was the source.
3934 Acknowledgments This work was supported by TUBITAK (The Scientific and Technological Research Council of Turkey; project no: 108Y084) and by Uludag University (project no: 2008/7).
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Environ Sci Pollut Res (2014) 21:3920–3935 Salihoglu G, Salihoglu NK, Aksoy E, Tasdemir Y (2011) Spatial and temporal distribution of polychlorinated biphenyl (PCB) concentrations in soils of an industrialized city in Turkey. J Environ Manag 92:724–732 Simcik MF, Franz TP, Zhang H, Eisenreich SJ (1998) Gas-particle partitioning of PCBs and PAHs in the Chicago urban and adjacent coastal atmosphere, states of equilibrium. Environ Sci Technol 32: 251–257 Sweetman J, Cousins IT, Seth R, Jones KC, Mackay D (2002) A dynamic level IV multi-media environmental model: application to the fate of PCBs in the United Kingdom over a 60-year period. Environ Toxicol Chem 21:930–940 Sweetman AJ, Dalle Valle M, Prevedouros K, Jones KC (2005) The role of soil organic carbon in the global cycling of persistent organic pollutants (POPs): interpreting and modelling field data. Chemosphere 60:959–972 Tasdemir Y, Vardar N, Odabaşı M, Holsen TM (2004) Concentrations and gas/particle partitioning of PCBs in Chicago. Environ Pollut 131:35–44 Tasdemir Y, Odabasi M, Holsen T (2005) Measurement of the vapor phase deposition of polychlorinated bipheyls (PCBs) using a water surface sampler. Atmos Environ 39:885–897 Toan VD, Thao VD, Walder J, Schmutz HR, Ha CT (2007) Level and distribution of polychlorinated biphenyls (PCBs) in surface soils from Hanoi, Vietnam. Bull Environ Contam Toxicol 78: 211–216 Wang DG, Yang M, Jia HL, Zhou L, Li YF (2008) Levels, distributions and profiles of polychlorinated biphenyls in surface soils of Dalian, China. Chemosphere 73:38–42
3935 Wesely ML, Hicks BB (1977) Some factors that affect the deposition rates of sulfur dioxide and similar gases on vegetation. APCA J 27: 1110–1116 WHO (1993) Environmental Health Criteria No:682, Polychlorinated biphenyls and terphenyls (Second edition).World Health Organisation, Geneva. WHO (2000) PCBs, Regional Office for Europe, Copenhagen, Denmark, Chapter 5.10 Air Quality Guidelines—Second Edition. Wilcke W, Müller S, Kanchanakool N, Niamskul C, Zech W (1999) Urban soil contamination in Bangkok: concentrations and patterns of polychlorinated biphenyls (PCBs) in topsoils. Aust J Soil Res 37: 245–254 Wilcke W, Krauss M, Safronov G, Fokin AD, Kaupenjohann M (2006) Polychlorinated biphenls (PCBs) in soils of the Moscow region: concentrations and small-scale distribution along an urban–rural transect. Environ Pollut 141:327–335 Yeo HG, Choi M, Chun MY, Kim TW, Cho KC, Sunwoo Y (2004) Concentration characteristics of atmospheric PCBs for urban and rural area, Korea. Sci Total Environ 324:261–270 Zhang HB, Luo YM, Wong MH, Zhao QG, Zhang GL (2007a) Concentrations and possible sources of polychlorinated biphenyls in the soils of Hong Kong. Geoderma 138:244–251 Zhang JY, Qui LM, He J, Liao Y, Luo YM (2007b) Occurrence and congeners specific of polychlorinated biphenyls in agricultural soils from Southern Jiangsu, China. J Environ Sci 19:338–42 Zhang Z, Liu L, Li YF, Wang D, Jia H, Wan X, Xu D, Ren N, Harner T, Sverko E, Ma J, Pozo K (2008) Analysis of polychlorinated biphenyls in concurrently sampled Chinese air and surface soil. Environ Sci Technol 42:6514–6518
RESEARCH ARTICLE
Air–soil exchange of PCBs: levels and temporal variations at two sites in Turkey Didem Yolsal & Güray Salihoglu & Yücel Tasdemir
Received: 31 July 2013 / Accepted: 7 November 2013 / Published online: 29 November 2013 # Springer-Verlag Berlin Heidelberg 2013
Abstract Seasonal distribution of polychlorinated biphenyls (PCBs) at the air–soil intersection was determined for two regions: one with urban characteristics where traffic is dense (BUTAL) and the other representing the coastal zone (Mudanya). Fifty-one air and soil samples were simultaneously collected. Total PCB (Σ82 PCB) levels in the soil samples collected during a 1-year period ranged between 105 and 7,060 pg/g dry matter (dm) (BUTAL) and 110 and 2,320 pg/g dm (Mudanya). Total PCB levels in the gaseous phase were measured to be between 100 and 910 pg/m3 (BUTAL) and 75 and 1,025 pg/m3 (Mudanya). Variations in the concentrations were observed depending on the season. Though the PCB concentrations measured in the atmospheres of both regions in the summer months were high, they were found to be lower in winter. However, while soil PCB levels were measured to be high at BUTAL during summer months, they were found to be high during winter months in Mudanya. The direction and amount of the PCB movement were determined by calculating the gaseous phase change fluxes at air–soil intersection. While a general PCB movement from soil to air was found for BUTAL, the PCB movement from air to soil was calculated for the Mudanya region in most of the sampling events. During the warmer seasons PCB movement towards the atmosphere was observed due to evaporation from the soil. With decreases in the temperature, both decreases in the number of PCB congeners occurring in the air and a change in the direction of some congeners were observed, Responsible editor: Leif Kronberg Electronic supplementary material The online version of this article (doi:10.1007/s11356-013-2353-y) contains supplementary material, which is available to authorized users. D. Yolsal : G. Salihoglu : Y. Tasdemir (*) Department of Environmental Engineering, Faculty of Engineering, Uludag University, 16059 Nilüfer, Bursa, Turkey e-mail: [email protected]
possibly caused by deposition from the atmosphere to the soil. 3-CB and 4-CB congeners were found to be dominant in the atmosphere, and 4-, 5-, and 6-CBs were found to dominate in the surface soils. Keywords Flux . Movement . Congeners . Temperature . Season
Introduction Persistent organic pollutants (POPs) are organic compounds of anthropogenic origin that can remain in nature without decomposing for long periods due to their resistance against photolytic, chemical, and biological decay. Polychlorinated biphenyl (PCB) compounds constitute a group that falls under the 12 groups of contaminants called POPs and has nonpolar features. Theoretically, 209 different PCB congeners exist (Carpenter 1998). PCBs threaten human health by accumulating in the food chain due to their lipophilic features and chemical stability (Lilienthal et al. 2000). The ability of PCBs to accumulate in non-polar matrices is relatively high (McIntyre and Lester 1982). Soils and sediments are the primary media for accumulation (WHO 1993). For these pollutants, the atmosphere acts as the most effective transfer medium, and the terrestrial soils act as the most significant receptive medium (Hippelein and McLachlan 1998). Once it was established that PCBs enter the food chain, cause environmental pollution, and threaten human health, their production was banned in many countries around the world and their use was restricted (Carpenter 1998). In Turkey, PCB usage in industries was restricted in 1973, and their use in open systems was completely prohibited on January 1st, 1996 (RCHC 1993). After the restriction of PCB production and usage, its emission into the atmosphere
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decreased in the 1970s and towards the end of the 1980s (Harner et al. 1995). However, the accumulation of PCBs in the soil until its prohibition had become so high that PCB movement from the soil to the air began as the atmospheric concentrations decreased (Harner et al. 1995). It is known that these substances can still be found in all phases and constitute a serious environmental problem. Determining the concentrations of these contaminant types in the air and soil and the exchange at the air/soil intersection provide significant contribution toward identifying the human health risks that PCBs may cause. The purpose of this study was (1) to determine the air and soil PCB concentrations, (2) to calculate the dry deposition and air/soil gas exchange fluxes, and (3) to investigate the direction of the PCB movement, in Bursa, and industrial city in Turkey. To reach these aims, studies were conducted by measuring the simultaneously collected air and soil samples at a high-traffic location, and a coastal location in the city, the Mudanya region. The movement of PCBs from the atmosphere to the soil occurs through dry and wet depositions and diffusion (Backe et al. 2004). Harner et al. (1995) reported that diffused transportation is the major process that determines the air–soil–air exchange. Diffused transportation is governed by the chemical potential between the soil and the atmosphere and is defined by the equilibrium distribution coefficient K SA (nondimensional) of a contaminant between the air and soil (Hippelein and McLachlan 1998), as shown in Eq. 1: K SA ¼ C S ρs =C A
ð1Þ
where C S indicates the contaminant concentration in the soil (pg/g dry weight), ρ S indicates the soil density (g/cm3), and C A indicates the contaminant concentration in the gaseous phase (pg/m3). K SA is dependent on temperature, moisture, and soil characteristics (Meijer et al. 2003). The octanol–air distribution coefficient (K OA) is used as a basic variable that explains the chemical distribution between the atmosphere and organic phases (Harner et al. 2001). Hippelein and McLachlan (1998) related K SA with K OA, the organic carbon fraction of the soil (f OC), and the soil density (ρ S): K SA ¼ 0:411 ρS f OC K OA
ð2Þ
K OA ¼ K OW =K H
ð3Þ
K H ¼ expð−ΔH H =RT þ ΔS H =RÞ
ð4Þ
The factor 0.411 depends on the correlation between K SA and K OA (Hippelein and McLachlan 1998; Bidleman and Leone 2004). Hansen et al. (1999) reported the octanol–water
distribution coefficients (K OW), while Bamford et al. (2000) reported ΔH H (measured enthalpy) and ΔS H (entropy) values, which are used to calculate the Henry law constant (K H) for each PCB congener. The ideal gas constant R is 8, 314 J/mol K, and the temperature T (K) is the soil temperature for each sample.
Materials and methods Sample collection Sampling was conducted between July 2008 and June 2009 at BUTAL and Mudanya regions of Bursa city in Turkey. Air and soil samples were collected concurrently from two regions, BUTAL and Mudanya, two or three times in a month during 1 year. One sample was collected per matrix each sampling date. Fifty air and soil sample pairs were collected from these two sites during the sampling campaign. BUTAL (N 40°11′54′′, E 29°02′55′′) is located at the Merinos junction on Ankara-İzmir Road. This region, where traffic is dense, is also located at the city center. Near the BUTAL sampling location, there are textile, automotive, leather, and marble processing industries, business firms, and repair shops. The region represents pollution originating from industries, albeit at low levels. Additionally, the Nilüfer Creek, where some industrial and domestic wastewater is discharged, surrounds the sampling region. Mudanya (N 40°22′24.76′′, E 28°52′ 42.85′′), however, is located on the coastline of the Marmara Sea. Industry is not developed within the boundaries of this region, though some small- and large-scale olive processing facilities exist in Mudanya. The Marmara Sea is surrounded by regions where numerous industries exist. The neighboring cities, İstanbul (distance to Mudanya, ∼70 km) and Kocaeli (∼90 km) host several petroleum, organic chemistry, pharmaceuticals, food, fertilizer, metal, paint, and shipyard industries. Closer neighboring cities, Gemlik (∼23 km) has various factories such as olive, oil, soap, fertilizer, steel, sheet iron, and chemical industries, and Bursa (∼20 km) hosts several automotive, textile, machine, and food industries. The samples in the gaseous phase were collected from the air using a high-volume air sampler (HVAS) (Thermo Andersen GPS 11 Model, USA), utilizing polyurethane foam (PUF) and filter units. The filters and PUFs were wrapped in aluminum foil and brought to the laboratory in airtight plastic bags. In BUTAL region, HVAS was placed on a platform approximately 2.5 m high, and in Mudanya region, HVAS was placed on the roof of a three story building (∼15 m). Average air volumes collected were 277±15 m3 and 191± 60 m3 for BUTAL and Mudanya, respectively. Dry deposition samples were obtained using a wet–dry deposition sampler (WDDS). The WDDS consists of two compartments made of stainless steel. In the first compartment, dry deposition
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samples are collected on the days without rain, and wet deposition samples from rainy days are collected in the second compartment (Günindi and Tasdemir 2010). Soil samples were obtained from the ground under a tree in the BUTAL garden, located in an area that is not subject to foot traffic, approximately 4 m from the roadside. In Mudanya, the soil samples were obtained from a sloping field adjacent to the building where HVAS was located, that contains olive trees and is close to the roadside, which does not have a large volume of traffic. The soil samples were collected from at least five different points within an area of 10 m2 from a depth of 0–5 cm in the surface soil. The samples were homogeneously mixed. Approximately 150 g of soil was collected for each sample. Large stones and plants were removed from these samples. The soil samples without grinding and drying were wrapped in aluminum foil, placed in airtight plastic bags, and brought to the laboratory. The soil and air samples were prepared for analysis without subjecting them to contamination. Blank samples were obtained from each region along with the samples. These samples were collected by leaving the mouth of a bottle containing 10 g of clean sodium sulfate open for the duration of the sampling. Meteorological parameters such as weather temperature, soil temperature, and humidity were measured during the sampling process. Samples were collected on non-rainy days, and some setbacks and delays occurred in the sampling schedule, especially during rainy periods. Sample preparation and analysis Air samples were passed through a GFF and then through PUF cartridge. After sampling, the PUF cartridges were extracted in the Soxhlet extractor with 1:4 (v/v) DCM/PE mixture. The soil samples (10 g) were placed in ultrasonic baths twice for 30 min each after the addition of 20 mL of a 1:1 DCM/PE mixture (Salihoglu et al. 2011). The sample was filtered using filter paper after the bathing process. The vial and filter were rinsed with 10 mL DCM/PE and this was added to the pooled extracted solvents. Extracts were passed through a sodium sulfate column to remove any residual water. The sample volume was reduced using a rotary evaporator and high-purity N2, and a hexane exchange was performed. The 2 mL sample was cleaned by passing it through a glass column containing 3 g of silicic acid (deactivated with 100 μL pure water), 2 g of alumina (deactivated with 120 μL of pure water), and 1 cm of height sodium sulfate (Tasdemir et al. 2005; Cindoruk et al. 2007; Bozlaker et al. 2008). PCBs were eluted with 25 mL of PE. The volume of the PCB samples was reduced to 2 mL using pure nitrogen gas. One milliliter of H2SO4 was added to the remaining ∼2 mL extract to eliminate sulfur in the soil samples (Batterman et al. 2009; Meijer et al.
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2002). After mixing the liquid thoroughly, it was centrifuged for a few minutes (Tasdemir et al. 2005; Cindoruk et al. 2007). The top layer of the sample including PCBs in HEX was removed carefully with a pipette. Half a milliliter of hexane was added to the acid twice to rinse and remove the any residual PCBs and this hexane was added to the sample. It was very important not to collect any acid (the bottom layer which was darker in color) because it could ruin the capillary column if injected to gas chromatograph (GC). This step removes all other soluble and probable problem causing organic compounds before GC analysis. After a final blowdown to 1 mL by N2 gas the sample was ready for injection. Samples that were ready for chromatographic analysis after the processes of extraction, volume reduction, and fractionation were kept in a deep freeze of −20 °C. Quantification of PCB congeners were conducted using a HP 7890A GC-μECD (Mikro-Electron Capture Detector; HewlettPackard, USA). The temperature program used in PCB analysis was as follows: 70 °C (2 min), with 25 °C/min to 150 °C, with 3 °C/min to 200 °C, with 8 °C/min reaching 280 °C and holding at 280 °C for 8 min, and with 10 °C/min reaching 300 °C and holding for 2 min. The inlet temperature was held at 250 °C and the detector temperature was 320 °C. Helium, the carrier gas (1.9 mL/min), was used with a makeup gas of high-purity nitrogen. Splitless (after 1 min, a separation vane was opened) injection was used with purge flow of 25 mL/min. A HP5-MS capillary column (30 m×0.32 mm× 0.25 μm; Agilent 19091J-413) was used. Five levels of standard solution between 0.05 and 25 ng/mL were used for calibration. The r 2 for each of the 83 PCB congeners was obtained over 0.99. System performance was verified by the analysis of the midpoint calibration standard after injection of 25 samples. The instrument detection limit was determined as 0.1 pg for an injection of 1 μL. The total organic carbon (TOC) contents of the soils were measured using the SSM-5000 module of Shimadzu TOC Analyzers TOC-VCPN, according to the 5310 B method listed in the Standard Methods. The mean organic carbon fraction was determined to be 2.0±0.7 % in BUTAL and 1.1±0.7 % in Mudanya. The soil density was measured to be 1.49 g/cm3 in the BUTAL region and 1.48 g/cm3 in Mudanya. Quality control and quality assurance The 82 PCB congeners investigated in the two regions were PCB# 4, 5, 6, 7, 8, 9, 10, 12, 13, 15, 16, 17, 19, 21, 22, 26, 28, 31, 32, 37, 41, 42, 44, 45, 47, 48, 49, 52, 53, 56, 60, 61, 64, 66, 70, 71, 74, 77, 81, 83, 84, 86, 87, 89, 91, 92, 95, 99, 100, 101, 105, 110, 114, 118, 119, 123, 126, 128, 131, 132, 135, 138, 144, 149, 153, 156, 163, 167, 169, 170, 171, 172, 174, 180, 190, 194, 199, 200, 202, 205, 206, and 207. Aluminum foil and Teflon materials were used during the collection of the samples, transportation to the laboratory, and storage.
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Glassware products used in the laboratory were first washed with tap water; then passed through pure water, methanol (MeOH), and DCM; and finally dried. After drying, they were wrapped with aluminum foil to prevent air contact. Surrogate standards were used to calculate the analytic efficiency of the samples, in other words, the losses that could occur during the analysis procedure. Approximately 4 ng/mL each of the congeners PCB# 14 (3,5-dichlorophibenyl), 65 (2, 3,5,6-tetrachlorophibenyl), and 166 (2,3,4,4′,5,6hexachlorophibenyl) were added to the samples. The average efficiency (%) values in the soil and air samples are given in Table 1. Prior to GC μ-ECD injection, 2 ng/μL of the internal standard (volume determinant) was added to each bottle. The standards of PCB# 30 (2,4,6 trichlorophibenyl) and 204 (2,2′, 3,4,4′,5,6,6′-octachlorobiphenyl) were used to determine the volume efficiency of the specimen in the sample bottle. Blank samples were collected to determine whether any contamination occurred after sampling. The limit of detection (LOD) value was obtained by taking the average of each PCB level (ng) measured in the blank samples and adding the standard deviation multiplied by 3 (LOD=avg.+3×SD). If the PCB congeners were greater than the LOD values in the samples, these were reported in the calculations. Furthermore, each sample was subjected to blank sample correction.
Results and discussion Soil and air concentrations in BUTAL region The total concentrations of PCBs found in the atmosphere and soils of BUTAL region are shown in Fig. 1a. The average PCB concentration in the gaseous phase in the atmosphere of the BUTAL region was found to be 360±210 pg/m3. The PCB levels measured in the urban atmosphere in this study were found to be both lower and higher than some other regions (Yeo et al. 2004; Tasdemir et al. 2004). Researchers have reported PCB levels ranging between 21 and 1,820 pg/m3 (Tasdemir et al. 2004) in the atmosphere. Some seasonal variations were observed in the PCB concentrations. The Table 1 Average recovery efficiencies for the samples (%)
BUTAL Soil samples PCB# 14 65±21 PCB# 65 66±24 PCB# 166 66±24 Air samples (PUF) PCB# 14 56±18 PCB# 65 57±17 PCB# 166 69±19
Mudanya
67±23 76±24 63±20 62±21 63±19 74±24
PCB levels, which varied between 225 and 830 pg/m3 (average 430±210 pg/m3) during the summer season, were determined to range between 230 and 910 pg/m3 (480±270 pg/m3) during autumn, 125 and 580 pg/m3 (335±195 pg/m3) during winter, and 100 and 415 pg/m3 (250±135 pg/m3) during spring. While high PCB concentrations were observed at the BUTAL region during the summer and autumn months, lower levels were observed during the winter months. The average PCB concentration measured in the soil samples collected from the BUTAL region was determined to be 2,010±1, 735 pg/g dm (26 samples). The total PCB levels detected in the BUTAL soils varied between 480 and 7,060 pg/g dm (summer), 265 and 5,370 pg/g dm (autumn), 105 and 1, 270 pg/g dm (winter), and 475 and 2,585 pg/g dm (spring). The average soil PCB concentrations were determined to be 2, 425 ± 2,060 pg/g dm (summer), 3,525 ± 2,055 pg/g dm (autumn) 625 ± 485 pg/g dm (winter), and 1,415 ± 720 pg/g dm (spring). The PCB levels found in the BUTAL soils fall at the lower end of the range of soil levels reported for various locations around the globe (Ren et al. 2007; Wilcke et al. 1999). The distributions and levels of PCB pollution in the soils of several urban, rural, and industrial regions are given in Table 2. Table 3 gives the variability in the levels of PCB congeners measured both in the atmosphere and soils of the regions investigated. Most of the 82 PCB congeners investigated were encountered in BUTAL’s atmosphere, and PCB# 81/87, 194, 205, and 206 were not detected. The ten PCB congeners/pairs with the highest concentrations (PCB# 4/10, 12/13, 16/32, 19, 21, 28, 31, 44, 49/48, and 52) accounted for 56.7 % of the average concentration in the BUTAL’s atmosphere. The largest groups among the homolog groups in the BUTAL atmosphere were found to be 3-CBs 38 % and 4-CBs 26 %.The industries, residential areas, evaporations from Nilüfer Creek, which is contaminated by wastewaters, and atmospheric transportation can be considered as possible PCB sources in the regional atmosphere. Among the 82 PCB congeners investigated, only PCB# 16/ 32, 131, 135/144, 167, 205, and 207 were not encountered in the soils of BUTAL region (Table 3). The ten PCB congeners/ pairs in the BUTAL region soils with the highest concentrations were determined to be PCB# 4/10, 84, 114/149, 123, 128, 153, 163/138, 169, 174, and 180. These congeners amount to 44.1 % of the average PCB concentration in BUTAL’s soils. Figure 2 shows the seasonal homolog group distributions in the soils of the two regions investigated. In BUTAL, the largest group consisted of 5-CBs with a percentage of 28.4 %, and the others were found to be as follows: 2CBs (6.5 %), 3-CBs (8.2 %), 4-CBs (20 %), 6-CBs (23.0 %), 7-CBs (11.4 %), 8-CBs (2.4 %), and 9-CBs (0.03 %). This distribution displays similarities to other studies in the literature (Aichner et al. 2007; Ren et al. 2007; Lead et al. 1997; Zhang et al. 2007b). Homolog distributions varied depending
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Fig. 1 PCB levels measured in the atmosphere and soils of a BUTAL region b Mudanya region
on the season (Fig. 2). While 5-CBs were dominant during the summer and autumn seasons in BUTAL region, 4-CBs and 6CBs were found to be higher during the winter and summer months. The soil levels of homolog groups measured in summer and autumn months were found to be statistically higher than that of winter months (paired samples test, p < 0.05; Table S1). General expectation would be lower PCB levels in warmer seasons due to evaporation, which is just the opposite situation observed in BUTAL. Possible reason might be the influence of local industries in the region dominating the seasonal effects. A significant correlation was observed between the air and soil PCB concentrations measured at the BUTAL region (R 2 =0.39, p 6-CBs> 7-CBs>3-CBs>8-CBs (Fig. 2). It was seen that soils of Mudanya region has a lower rate of high-molecular-weight (7-, 8-, and 9-CB) PCBs compared to the BUTAL region. Possible explanation could be the location of BUTAL region, which is closer to the industry and other sources; therefore, the heavy PCB congeners could have been deposited near their source. However, industrial settlement in Mudanya is not as developed as in BUTAL, and the soils were not as polluted as that of BUTAL soils. The PCB levels measured in the soils of Mudanya region in winter were found to be higher than that of summer and autumn (paired samples test, p 0.50, Mudanya) for either region.
Conclusions In this study, the PCB levels in the soils and in the air were measured at two different regions of Bursa city, BUTAL, a location consisting of local industries, and Mudanya, a location on the coastline of the Marmara Sea.
3-CBs and 4-CBs were found to be dominating in BUTAL atmosphere while the largest group in the soils was found to be 5-CBs. Seasonal variations were observed in terms of PCB levels. The soil PCB levels measured in summer and autumn months were found to be statistically higher than that of winter months in BUTAL region. General expectation would be lower PCB levels in warmer seasons due to evaporation, which is just the opposite situation observed in BUTAL. Possible reason might be the influence of local industries in the region dominating the seasonal effects. A significant correlation was observed between the air and soil PCB concentrations measured at this region inferring that both the atmosphere and soils of the region were influenced by the same sources. Atmospheric PCB levels in Mudanya were found to be comparable to that of BUTAL region although industry is not developed within the boundaries of this region. Possible reasons suggested were the influence of Marmara Sea and the industrial activities at the neighboring cities. The PCB levels measured in the soils of Mudanya region in winter were found to be higher than that of summer and autumn, as opposite to the situation in BUTAL. This implied possible evaporation from the soil into the air, thus causing a reduction in the soil PCB levels. Soil PCB levels of Mudanya were statistically lower than that of BUTAL region although no significant difference was determined between the air PCB levels of Mudanya and that of BUTAL. In BUTAL region, low-molecular-weight congeners were generally observed to move from soil to air and highmolecular-weight congeners transferred from air to soil. The number of PCB congeners detected in the soils of this region decreased as air temperature decreased. In Mudanya region, the PCB congeners generally had a tendency to move from air to soil. Thus, in Mudanya, the soil was the receptive medium and the air was the source.
3934 Acknowledgments This work was supported by TUBITAK (The Scientific and Technological Research Council of Turkey; project no: 108Y084) and by Uludag University (project no: 2008/7).
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