Assessment of the Spatial Distribution of Coplanar PCBs, PCNs, and

Aug 29, 2008 - University of Toronto Scarborough, 1265 Military Trail,. Toronto, ON, Canada, M1C 1A4. Received April 12, 2008. Revised manuscript rece...
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Environ. Sci. Technol. 2008, 42, 7336–7340

Assessment of the Spatial Distribution of Coplanar PCBs, PCNs, and PBDEs in a Multi-Industry Region of South Korea Using Passive Air Samplers SONG-YEE BAEK,† SUNG-DEUK CHOI,‡ S E - J I N L E E , † A N D Y O O N - S E O K C H A N G * ,† School of Environmental Science and Engineering, Pohang University of Science and Technology (POSTECH), San 31, Hyoja-dong, Nam-gu, Pohang, 790-784, Republic of Korea, and Department of Physical and Environmental Sciences, University of Toronto Scarborough, 1265 Military Trail, Toronto, ON, Canada, M1C 1A4

Received April 12, 2008. Revised manuscript received July 01, 2008. Accepted July 13, 2008.

Coplanar polychlorinated biphenyls (PCBs), polychlorinated naphthalenes (PCNs), and polybrominated diphenyl ethers (PBDEs) were sampled using polyurethane foam (PUF) disk passive air samplers (PAS) at 19 sites in a heavily industrialized region of South Korea for 6 months (January-July 2006). The levels and spatial distribution of these three chemical groups were investigated to identify potential sources and transport in the study area, which can be divided into five regions: a steelmanufacturing complex, a residential area near the steel complex, a rural area, a semi-industrial area, and a petrochemicalmanufacturing complex. Air concentrations (pg · m-3) were estimated using an average sampling rate of 3.0 m3 · day-1 and ranged as follows: coplanar PCBs (0.8-16), PCNs (1.7-35), and PBDEs (3.8-24). The levels of coplanar PCBs and PBDEs were found to be the highest in the steel complex, followed by the petrochemical complex and the semi-industrial area. In addition, a high level of PCNs was measured near a petrochemical-processing plant. However, the residential area near the steel complex and the rural area showed relatively low concentrations of these chemicals, suggesting that the steel and petrochemical industries are probably important sources in the study area, but these potential sources do not strongly influence the surrounding areas.

Introduction Polychlorinated biphenyls (PCBs), polychlorinated naphthalenes (PCNs), and polybrominated diphenyl ethers (PBDEs) have all been used for commercial purposes (1-3). Because of their physicochemical properties, they are persistent in the environment and undergo long-range atmospheric transport (LRAT) via repeated evaporation and deposition. They can thus be found distant from their sources (4), and therefore, it is difficult to identify the locations and contributions of specific sources of these compounds. * Corresponding author phone: (82)-54-279-2281; fax: (82)-54279-8299; e-mail: [email protected]. † Pohang University of Science and Technology. ‡ University of Toronto Scarborough. 7336

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PCNs were widely used as dielectric fluids and insulators from the 1920s to the 1950s. Worldwide PCN mixture production was estimated to be 10% of PCB production at 150 000 metric tonnes (5). The production of PCNs decreased in the late 1970s, as they were replaced by other compounds, such as PCBs. PCNs are no longer manufactured commercially (2), but they occur as a byproduct in technical PCB formulations (6) and continue to be released from PCN and PCB products to the environment. As PCBs have similar properties to PCNs, they also function as dielectric fluids and insulators. It was estimated that more than 1.3 million tons of PCBs were produced in the world between 1929 and 1989 (7). The high toxicities of PCBs were confirmed in the 1970s, and the production of PCBs is now prohibited in most countries. However, PCB products manufactured before the prohibition are still in use and can contaminate the environment by evaporation and leakage from products and landfill. Thus, although PCNs and PCBs are no longer manufactured, they continue to be detected in the environment. Penta-, octa-, and deca-PBDEs have been used globally as flame retardants in many products, including computers, electronic equipment, plastic products, and textiles. PBDEs can thus be released from many products. Consequently, usage of PBDEs is banned in EU and some states within the United States. However, the manufacture and use of PDBEs continues in many countries (8). The sources of PCBs, PCNs, and PBDEs are concentrated in urban and industrial areas, and therefore, high levels of those persistent organic pollutants (POPs) have been detected in urban and industrial regions (9-11). While there is a little information on past usage and current inventories of chemicals in many countries, environmental measurements aid in better understanding the sources and transport of POPs. Passive air samplers (PAS) have been used for various monitoring studies from a local to global scale to investigate sources and distributions of POPs (12-16). Although high volume samplers (HVS) are a conventional tool for POPs sampling in air, they are impractical for sampling with a high spatial resolution as they require electricity and are expensive to purchase and operate. On the other hand, the PAS are simple devices based on the theory of physical diffusion and thus do not require electric power. For these reasons, they can be deployed at many sites for a long time (over several months) and are suitable to assess the source-receptor relationships of POPs. The study area, located on the south coast of Korea, is a heavily industrialized region with both a steel-manufacturing complex and a petrochemical-processing complex. Because there are residential areas between these industrial regions, possible adverse effects of pollutants from these industries on residents have been a significant concern. Previous studies have been conducted for assessing contamination status and sources in this region. Hong et al. (17) found that the sediment of this region was contaminated by PCBs and concluded that steel-manufacturing activity could be a source of these chemicals. In this study, PAS were deployed at 19 sites in this area to assess the levels of coplanar PCBs, PCNs, and PBDEs and to investigate source-receptor relations of these chemicals.

Materials and Methods Passive Air Sampling. Passive air sampling was conducted for two three-month periods: Period 1 was January-April 2006 (winter-spring), and period 2 was April-July 2006 (spring-summer). The sampling sites were divided into five 10.1021/es801019k CCC: $40.75

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FIGURE 1. Location of sampling sites: A, steel-manufacturing complex (n ) 9); B, residential area (n ) 4); C, rural area (n ) 3); D, semi-industrial region (n ) 1); E, petrochemicalmanufacturing complex (n ) 2). groups: (A) the steel-manufacturing complex, (B) the residential area adjacent to the steel complex, (C) rural areas, (D) semi-industrial areas, and (E) the petrochemical complex (Figure 1). Polyurethane foam (PUF) disks used in this study have a 14 cm diameter and 1.2 cm thickness. Details on the PUF disk PAS design, testing, and use can be found elsewhere (12, 18). The target compounds for analysis were coplanar PCBs (PCB numbers 77, 81, 105, 114, 118, 123, 126, 156, 157, 167, 169, and 189), tetra- through octachlorinated PCN homologues, and selected PBDE congeners (PBDE numbers 28, 47, 66, 99, 100, 153, and 154). The full description of cleanup, instrumental analysis, and QA/QC can be found in the Supporting Information. Calculation of Air Concentrations. In this study, average amounts of chemicals collected per day (pg · day-1 · PAS-1) were used to compare the levels of contamination between regions. However, to compare the levels of pollutants with previous results, the amounts of chemicals retained by the PUF (pg · PAS-1) must be converted to air concentrations (pg · m-3). Air concentrations can be estimated from the following equation: CPAS)CairRt

(1)

Where CPAS is the amount of chemical in a PAS (pg · PAS-1), Cair is the concentration of chemical in ambient air (pg · m-3), R is the sampling rate (m3 · day-1 · PAS-1), and t is the sampling period (day). As sampling rates are sensitive to meteorological conditions such as wind speed (19), it can be unwise to apply the same sampling rate to all sampling sites. However, wind speeds during the sampling periods were relatively mild (0.7-3.5 m · s-1) and uniform between sampling sites. Therefore, the use of an average sampling rate of 3.0 m3 · day-1 from previous studies (9, 18) can be justified for a rough comparison of air concentrations with those in previous studies.

Results and Discussion Spatial Distributions and Sources of Coplanar PCBs, PCNs, and PBDEs. Figure 2 shows the average amounts of the three chemical groups measured in each area over the study period. As there were no large differences in the total levels of PCBs, PCNs, or PBDEs between the two sampling periods, this figure represents the averaged data of both sampling periods. The steel complex results are divided into east (G1-6) and west parts (G7-9), because those locations showed large differences in the amounts of chemical measured. Coplanar PCBs. The measured masses of coplanar PCBs ranged from 0.25 to 40.1 (pg · day-1 · PAS-1) for the first

FIGURE 2. Time-averaged amounts of coplanar PCBs, PCNs, and PBDEs from the east part of the steel complex (Ae, n ) 6), the west part of the steel complex (Aw, n ) 3), the residential area (B, n ) 4), rural area (C, n ) 3), the semi-industrial region (D, n ) 1), and the petrochemical complex (E, n ) 2) for 6 months (January-July 2006). Error bars represent standard deviations. sampling period and from 1.15 to 53.0 for the second sampling period (Table S2 in the Supporting Information). Site G8, inside the steel complex, had the highest levels of coplanar PCBs at 40.1 and 53.2 for periods 1 and 2, respectively. The west part (G7-9) of the steel complex shows much higher levels of coplanar PCBs than other areas. The average amounts of coplanar PCBs decrease in the following order: the west part of the steel complex (Aw) . residential area (B) ≈ petrochemical complex (E) > east part of the steel complex (Ae) > semi-industrial area (D) > rural area (C) (Figure 2). PCB-118 was the dominant congener, accounting for 47% of the total of 12 coplanar PCBs, followed by PCB-105 and PCB-77. PCB 118 and the total coplanar PCBs were found to be highly correlated (p < 0.01). The high levels of PCB-118, -105, and -77 were detected in the air samples because commercial PCB mixtures such as Kanechlor (Japan) and Aroclor (US) contain a high proportion of those congeners (20). This congener pattern is similar to those measured in air samples taken urban, industrial areas of South Korea and rural, remote site of the United States (11, 21). There are three main sources of PCBs: (1) emission from commercial products, (2) re-evaporation of previously deposited PCBs from the surface soil and water, and (3) synthesis during thermal processes. The measured congener profiles can represent the relative contributions of the PCB sources. PCB-126 is formed during thermal processes such as incineration (20). In this study, PCB-126 was detected in many samples from the steel and petrochemical complexes, and the highest level of PCB-126 was found at site G3 during the second sampling period. Cleverly et al. (21) reported that increasing temperature lead to more active evaporation of PCBs from ground and water surfaces. Particularly, the levels of penta-CBs, such as PCB-105, -114, -118, and -123, have high correlations with temperature (22). In the present study, the average temperatures during the first and second sampling periods were 8.2 °C (winter-spring) and 19.3 °C (spring-summer), respectively. While the relative contributions of penta-CBs, especially PCB-118, decreased during the second period in the steel complex (Figure 3a), those of penta-CBs increased in the residential (Figure 3b) and rural areas. This result suggests that PCB levels in the steel complex might be constantly affected by local combustion sources, whereas residential and rural area levels were more influenced by evaporation of PCBs from the surrounding environment. Figure 4 shows the high levels of coplanar PCBs in the west part of the steel complex. Previous studies have already shown that sintering and steel-making processes are important sources of PCBs (23). Most of the processes implicated as PCB sources, such as coke production, sintering, and blast VOL. 42, NO. 19, 2008 / ENVIRONMENTAL SCIENCE & TECHNOLOGY

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FIGURE 3. Mass distributions of gaseous PCBs measured in the steel complex (a) and the residential area (b). furnace iron making are located in the east part, while in the west part of the steel complex only minimill plants are found. The average concentration of coplanar PCBs measured in the west part is four times higher than that in the east part of the steel complex, suggesting that the minimill plants may also be important sources of coplanar PCBs in the study area. Although the residential area was located on the downwind side of the steel complex during the second sampling period, the concentrations of coplanar PCBs in the residential area were much lower than those in the west of the steel complex. Furthermore, the residential area shows similar levels of coplanar PCBs between the two periods, despite easterly and westerly winds during the first period. The spatial distribution of coplanar PCBs in the steel complex and residential area indicates that the influence of the emission from the steel complex on the residential area seems to be not so significant; instead, other local sources such as residential buildings and transformers could be more important sources. In conclusion, the steel complex is likely to be an important source of coplanar PCBs in the study area, but the impact of the steel complex on the residential and rural areas seems to be small. PCNs. The measured amounts of tetra- through octaPCNs ranged from 6.28 to 165 (pg · day-1 · PAS-1) for the first sampling period and 6.54 to 48.9 for the second period with averages of 20.7 and 17.1, respectively (Table S2 in the Supporting Information). There are no significant differences in the average amounts of PCNs between the two sampling periods, nor between sampling sites with the exception of site G19. This site has very high levels of PCNs in both sampling periods. Notably, there is a vinyl chloride monomer (VCM) production plant located within several hundred meters from site G19. In the case of G18, which was close to site G19 (less than 5 km distant), it had a low PCN level. Because the prevailing wind blew from south to north for 6 months (Figure S1 in the Supporting Information), G18 might not have been particularly influenced by the VCM plant. This suggests that petrochemical processing, especially the VCM production process, could be a source of PCNs. The increased proportion of highly chlorinated CNs during the second sampling period well-reflects a temperature increase over 10 °C; tetra-CN and penta-CN accounted for 84 and 11% of the total PCNs, respectively, for the first sampling period, while 69% and 21% for the second sampling period. Site G19 had a high proportion of highly chlorinated CNs, such as hepta-CNs (12%) and octa-CNs (8%) compared to the averages of hepta-CNs (1%) and octa-CNs (1.8%) of all 7338

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FIGURE 4. Spatial distribution of coplanar PCBs, PCNs, and PBDEs over 6 months. sites for the second sampling period. A PUF disk normally retains compounds found in the gaseous phase, but when fine particles are collected on the PUF disk, less volatile compounds in the particulate phase can be also sampled. Therefore, the profile of PCNs measured at G19 could be affected by fine particles. PCNs can be formed during thermal processes; the production of PCN congeners PCN-50, -51, -54, -52/60, and -66/67 is related to such thermal processes. PCN-52/60 and -66/67 are dominantly present in the fly ash of incinerators and iron-sintering plants (24); therefore, high proportions of these congeners are believed to be an indicator of incineration and sintering processes. PCN-52/60 and -66/67 show the highest percentages of penta- and hexa-CNs in all samples collected in this study, showing that most sites in the study area were likely affected by sources related to thermal processes. In order to compare the influences of the sources, enrichment factors (EF) for each site for the two periods are shown in Figure S2 in the Supporting Information. EF is a similar concept to isomer fraction (IF ) mass of congener X/summed mass of all homologues) introduced by Helm et al. (25). The EF of a congener is calculated by dividing its IF

TABLE 1. Air Concentrations (pg · m-3) of Coplanar PCBs, PCNs, and PBDEs Derived by PUF Disk PAS for 6 Months compound

east part of the steel complex (n ) 6)

west part of the steel complex (n ) 3)

residential area (n ) 4)

rural area (n ) 3)

semi-industrial region (n ) 1)

petrochemical complex (n ) 2)

Σ12PCB ΣTe-OcPCN Σ7PBDE

0.81-3.93 1.69-3.67 4.71-7.68

6.38-15.6 4.14-4.51 9.81-23.6

2.37-3.08 3.98-5.48 5.14-9.03

1.06-1.96 1.99-3.37 3.76-5.18

1.69 5.60 15.5

1.02-4.42 4.80-35.0 6.81-13.9

for a site by the average IF of that congener for all sites. High EFs for PCN-52/60 and PCN-66/67 indicated that these two constitute high fractions of the penta- and hexahomologues, respectively. The EF of thermal-source-related congeners can be used to evaluate the relative inputs of combustion sources. A high EF indicates large inputs from combustion sources. A previous study reported that the high fraction of PCN66/67 in the region of the Great Lakes was related to high levels of industrial activity (9). Although the total concentrations of PCN were relatively low in the east part of the steel complex, high EFs of PCN-52/60 and -66/67 are found in those samples (G3, G4, G5), reflecting emissions from combustion sources such as coke making and sintering processes. Contrary to our expectations, the highest concentrations of PCNs were found in the west part of the steel complex, suggesting the influence of minimills located in this area. G19, with the highest PCN concentration, also shows a high EF of PCN-52/60, implying that this site is strongly affected by a specific PCN source. PBDEs. The average uptake of PBDEs ranged from 8.91 to 83.5 (pg · day-1 · PAS-1) for the first period and from 13.5 to 62.9 for the second period (Table S2 in the Supporting Information). Here, G5 data for the second sampling period were not considered because of an exceptionally high concentration of BDE-153. This can be caused by a large amount of atmospheric particles being trapped on the PUF disk. In addition, the PBDE concentration at G12 for the second sampling period is abnormally high; BDE-47, -99, and -100 for the second period were an order magnitude greater than those for the first period, suggesting potential contamination during sampling and analysis processes. Therefore, G12 data were not further considered. Meanwhile, the average amounts of PBDEs slightly increased from the first sampling period (21.95 pg · day-1 · PAS-1) to the second sampling period (29.40 pg · day-1 · PAS-1), but this is not statistically different (p > 0.05). BDE-47 is generally dominant in the gas phase. As temperature increases, evaporation of less brominated congeners from sources normally increases. In this study, we also found that BDE-47 was the most dominant congener, and the contribution of BDE-47 increased from 43% (period 1) to 53% (period 2). There have been no reports that PBDEs are emitted from steel production processes. Only a recent study reported that minimills could be a source of PBDEs, because they use scrap metal with PBDE residues; a high concentration of PBDEs was measured in bag-filter dust from electric arc furnaces of minimills (26). High levels of PBDEs were found at G8, and the average amount of PBDEs in the west part of the steel complex was 2.5 times higher than that in the east part of the steel complex. This result also suggests that minimills can be an important source of PBDEs in this area. The site G17 in the semi-industrial area had relatively high concentrations. There is a small-scale plate-steel production plant for automotive manufacturing near G17, which might be a source of PBDEs. In our previous study (27), we also found high concentrations of PBDEs in a steel complex located in a different city of South Korea. It was suggested that a minimill was responsible for the high levels of PBDEs.

As presented in Figure 4, the spatial distribution of PBDEs is similar to that of coplanar PCBs with a significant correlation (p < 0.01), indicating that the locations of emission sources and transport patterns for the two chemical groups were the same in the study area. Comparison with Other Studies. The summary of air concentrations estimated in this study is presented in Table 1, and those of previous studies are provided in Table S3 in the Supporting Information. Coplanar PCBs. The PCB concentrations in the rural area were 1.06-1.96 (pg · m-3) (Table 1), which is similar to 1.91 (six congeners) measured at Dunai, in the Canadian Arctic (28). Thus the PCB levels in the rural area of this study can be considered to be background levels. The highest level of total coplanar PCBs was found at G8 (15.6) in the steel complex, which is similar to the total concentration of six coplanar PCBs (13.3) measured in Chicago, IL (10). Because the concentration of PCBs in Chicago was measured using HVS, the reported concentration is the sum of the gas and particle phases. Therefore, the actual concentration (vapor + particle) of PCBs at G8 might be higher than that in Chicago. The levels of coplanar PCBs measured in the residential area near the steel complex ranged from 2.37 to 3.08, and those in the petrochemical complex ranged from 1.02 to 4.42 (Table 1). These levels are similar to those measured in a residential area of The Netherlands (3-5) (29). Even though various chemical plants are located in the petrochemicalmanufacturing area, the level of coplanar PCBs is similar to those in residential areas, suggesting that the emission of coplanar PCBs from the chemical plants is not significant. PCNs. The total PCN concentration of G19 in the petrochemical complex is 35.0 (pg · m-3) (tetra- through octaCNs, Table 1), which is lower than that (52.1: tri- to octaCNs) measured in Chicago during winter (9). However, since we did not consider tri-CNs in the calculation of the total PCNs, the level of PCNs in the petrochemical complex is probably not lower than that measured in Chicago. Also, the Global Atmospheric Passive Sampling (GAPS) study (16) showed that tri- through octa-CN concentrations were greater than 30 in urban/industrial regions. The range of PCN concentrations in the residential area (B) was 3.98-5.48. Site G17 in the semi-industrial area (D) had a slightly higher concentration (5.60) than the residential area. The rural area (C) had the lowest PCN levels (1.99-3.37). In the GAPS study (16), rural areas had PCN concentrations of less than 2.5. However, the GAPS study only analyzed 29 PCN congeners; thus, we cannot compare the concentrations of PCNs directly. PBDEs. The PBDE concentrations in this study ranged from 3.76 to 23.6 (pg · m-3), while those measured in Toronto were in the range of 3-30 (30). The levels of PBDEs in European countries varied widely from 0.5 to 250. The relatively even distribution of PBDEs is observed in the present study because of ubiquitous sources of PBDEs in industrial and residential areas. The highest concentration of PBDEs (23.6) is observed at G8, comparable with the gasphase PBDE concentration (22.1) in an industrial area in Izmir, Turkey (26). There are 3-fold differences of PBDE concentrations between the west and east part of the steel VOL. 42, NO. 19, 2008 / ENVIRONMENTAL SCIENCE & TECHNOLOGY

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complex; the average concentration of PBDE in the west part of the steel complex is 15.3, while the average concentration in the east part of the steel complex is 6.25. G17 in the semiindustrial region had a relatively high level of PBDEs (15.5). The concentrations of PBDEs in the residential area are 5.14-9.03. Those levels are under the ranges measured in a suburban region in the United Kingdom at 10.3-14 (31). The rural area of this study shows the lowest concentrations of PBDEs (3.76-5.18). In summary, the results showed an industrial-rural gradient for all three chemical groups, which suggests that industrial areas are the main sources of these chemicals. High levels of coplanar PCBs were detected in part of the steel complex. Until now, it has not been proven that a steel complex is a source of PBDEs. However, high levels of PBDEs measured in this study seem to be caused by the steel complex’s use of scrap iron. We also confirmed that a specific petrochemical process is likely an important source of PCNs. However, the influence of these chemicals on the air of residential and rural areas was not considerable. This study is one of case studies using PAS to assess the spatial distribution of POPs in a local area and demonstrates that PASmonitoringisusefulforunderstandingthesource-receptor relationships of POPs in multi-industry areas.

Acknowledgments This work was supported by the Brain Korea 21 project. We are grateful to Tom Harner at Environment Canada for providing passive air samplers.

Supporting Information Available A full description of the cleanup, instrumental analysis, and QA/QC; Tables S1-S3; Figures S1 and S2; and a list of references. This material is available free of charge via the Internet at http://pubs.acs.org.

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