Contamination Profiles of Polychlorinated ... - ACS Publications

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Chapter 9

Contamination Profiles of Polychlorinated Biphenyls (PCBs) in the Atmosphere and Soil of South Korea Tuyet Nam Thi Nguyen, Ho-Young Lee, and Sung-Deuk Choi* School of Urban and Environmental Engineering, Ulsan National Institute of Science and Technology (UNIST), Ulsan 44919, Republic of Korea *E-mail: [email protected]

This chapter provides an overview of polychlorinated biphenyl (PCB) contamination in the atmosphere and soil of South Korea. Variations in PCB trends were evaluated via spatial distribution, temporal variation, and gas/particle partitioning. In addition, information on the history of and future plans for PCB management in Korea was examined. Levels of PCBs in the atmosphere decreased gradually, whereas those in soil samples exhibited the opposite trend, which is a steady increase over time. For the atmospheric PCBs, no significant seasonal or spatial variations in the profiles of PCBs and dioxin-like PCBs were observed. In addition, low-molecular-weight PCBs (mono- to penta-CBs) mostly appeared in the gas phase and showed high contributions in the summer. Most high-molecular-weight PCBs (hexa- to deca-CBs) existed in the particle phase and were enriched in the winter. The major emission source of the atmospheric PCBs is believed to be re-emission from PCB-containing surfaces, such as soil, water, or PCB-containing equipment. There was also no significant difference in the spatial distribution and profiles of PCBs in soil. Most of the soil samples exhibited high fractions of pentaand hexa-CBs. Moreover, the heavy PCBs at the urban and industrial sites showed higher proportions compared to those at the rural sites. Remote areas, such as a forest site, showed

© 2016 American Chemical Society Loganathan et al.; Persistent Organic Chemicals in the Environment: Status and Trends in the Pacific Basin Countries I ... ACS Symposium Series; American Chemical Society: Washington, DC, 2016.

higher fractions of light PCBs. The major emission sources of PCBs in soil are likely leakage from commercial PCBs and the influence of local combustion.


Introduction Polychlorinated biphenyls (PCBs) are a group of persistent organic pollutants (POPs) that have been synthesized since the early 1880s (1) and produced as commercial products (also known as intentionally produced PCBs) since 1929 (2). Commercial PCBs have various trade names, such as Aroclor (produced by Monsanto, USA), Kanechlors (produced by Kanegafuchi, Japan), and Clophen (produced by Bayer AG, West Germany) (3). Mono- to hepta-CBs were identified as the predominant homologue compositions for the commercial PCB products (3). PCBs have 209 congeners; a difference in physicochemical properties among these congeners relates to the number and positions of the chlorine atoms on the benzene rings (2). Low-molecular-weight PCBs are soluble and volatile, while high-molecular-weight congeners are more hydrophobic (2). However, the general properties of PCBs are thermal stability and resistance to both acids and alkalis (4). Therefore, they had been widely used in industrial applications. For instance, PCBs had been used as plastic additives or pesticide extenders or added into capacitor and transformer oils for insulating electricity. PCBs can also be produced unintentionally as by-product POPs in chemical processes containing chlorine and hydrocarbons under a thermal process (5), such as ferrous production, waste incineration, and fuel combustion (6). By-product PCBs include mono-ortho and non-ortho congeners, which are known as coplanar PCBs or dioxin-like PCBs (DL-PCBs) because these congeners have dioxin-like behavior. PCBs can remain in the environment for a long time owing to their stable properties and then cycle between various environmental compartments, such as the atmosphere, soil, sediment, water, and living organisms (1). PCBs were listed as one of the original 12 POPs covered by the Stockholm Convention due to their extreme persistence, bioaccumulation, wide distribution, and serious health effects, such as birth defects, pigmentation of skin, and peripheral nervous system degeneration (4). Noticeably, DL-PCBs can cause cancer because they have the ability to bind to an arylhydrocarbon receptor (AhR), which is a transcription factor of many genes (2). South Korea, located in northeastern Asia, has never produced PCBs but did import them for industrial purposes (6). Korea ratified the Stockholm Convention in January of 2007 (6). One year later (January of 2008), the Korean Ministry of Environment (KMOE) enforced the POPs Control Act to implement the Stockholm Convention (6). Thereafter, PCBs have become one of the most concerning POPs in Korea. Moreover, many studies reported that PCBs have been detected in the various environmental compartments of Korea, such as the atmosphere (7), sediment (8), and soil (9). Some locations in Korea exhibit high levels of PCBs, such as Incheon and Busan (major source: harbor activities) 194 Loganathan et al.; Persistent Organic Chemicals in the Environment: Status and Trends in the Pacific Basin Countries I ... ACS Symposium Series; American Chemical Society: Washington, DC, 2016.


(8), Pohang (major source: iron and steel making plant) (10), and Ulsan (major sources: shipbuilding (8) and petrochemical activities) (11). A map showing the administrative boundaries of South Korea is presented in Figure 1.

Figure 1. Map of South Korea. The capital (Seoul) is marked in red.

PCB Management in South Korea The POPs Control Act was enacted in Korea in 2007. The contents of this Act included the following: (a) guidelines for checking PCB-containing stockpiles, (b) methods for resolving PCB-containing waste during collection and transportation, (c) guidelines for collection and storage of PCB-containing waste, and (d) methods for PCB waste treatment. In Korea, chemical reaction methods are encouraged to handle PCB waste, while high-temperature incineration has been restricted because this method can create dioxin (1), which is more toxic than PCBs. In Korea, PCBs were never produced but were imported for industrial usage (6). Since 1979, the restricted use of PCBs has been legally regulated by the Electricity Business Act (EBA) (6). Electric circuits containing PCBs in 195 Loganathan et al.; Persistent Organic Chemicals in the Environment: Status and Trends in the Pacific Basin Countries I ... ACS Symposium Series; American Chemical Society: Washington, DC, 2016.


their insulating oils should not be used (12); however, existing PCB-containing equipment could be used for other purposes until 1996, when PCBs or items containing PCBs at concentrations of over 50 ppm were banned from manufacture, import, and use (12). Moreover, waste containing PCBs at concentrations greater than 2 ppm was regarded as specific hazardous waste and needed to be treated with special methods regulated by KMOE (6). In 2003, the National Institute of Environmental Research (NIER) conducted a nationwide survey on transformers and industrial waste to review their PCB values in Korea (12). Starting in 2004, in an effort to dispose of PCB-containing products and waste, KMOE cooperated with the Korea Electric Power Cooperation (KEPCO) and non-government organizations (NGOs) (12) to develop PCB treatment technology and provide funds for the limitation of PCB contamination in Korea (6). In particular, since May of 2010, KEPCO built an integrated PCB system (http://pcbs.me.go.kr/) to prepare for a national inventory list of PCBs and supply guidelines for the safety and management of PCB-containing equipment (13). Transformers were reported as a major source of PCBs in Korea (14). From 2008 to 2011, the number of disposed transformers in Korea was 426,842 (12). Among them, transformers having concentrations of PCBs greater than 50 ppm accounted for approximately 1% of the total, and most of them were installed on poles (12). Moreover, approximately 25% of the total transformers in Korea contained concentrations of PCBs over 2 ppm, and most of them were located above ground (12). These transformers could be a significant emission source of PCBs in Korea because PCBs might be released when the transformers are stored or disposed. To achieve the target reductions in PCB contamination, KMOE established monitoring networks and scientific management of PCBs, such as continuous monitoring and risk assessment for areas having a high risk of PCB contamination (12). Analysis and treatment methods for transformers having PCB concentrations of over 50 ppm as well as transformers installed on poles before 1998 were established in 2015 (12). Other targets of KMOE are eco-friendly treatment methods for transformers having PCB concentrations over 2 ppm and plans to target transformers installed on poles between 1999 and 2008 until 2025 (12). This chapter provides an overview of PCB contamination in the atmosphere and soil of South Korea. A total of 44 references (27 for the atmosphere and 17 for the soil) including domestic/international articles, theses, and reports from governmental agencies were collected and summarized.

196 Loganathan et al.; Persistent Organic Chemicals in the Environment: Status and Trends in the Pacific Basin Countries I ... ACS Symposium Series; American Chemical Society: Washington, DC, 2016.

Polychlorinated Biphenyls (PCBs) in the Atmosphere of South Korea


Levels of PCBs and DL-PCBs in the Atmosphere of Korea Spatial distributions of PCBs and DL-PCBs in the atmosphere of Korea are illustrated in Figures 2 and 3, respectively. The levels of PCBs and DL-PCBs in the industrial and urban sites were higher than those in the rural sites (10, 15), indicating the emission sources of PCBs in Korea could be derived from industrial and urban activities. As shown in Figure 3, the north-west area of Korea exhibited high levels of DL-PCBs (16). A previous study reported the north-west area could be contaminated with a phenoxy-herbicide mixture (also known as Agent Orange) from 1967 to 1969 (16). In addition, DL-PCBs are likely to be associated with this herbicide (17), resulting in the high levels of DL-PCBs in the north-west area of Korea. Population density can also be related to PCB emissions (15). In Korea, Incheon and Seoul are two metropolitan cities, having the highest population density in the country. Thus, human activity and emission sources of PCBs in these two cities could be higher than those in other urban areas in Korea, resulting in the high levels of PCBs observed in these cities. Among industrial sites, Pohang, Siheung, Incheon, and Pocheon exhibited the highest levels of DL-PCBs (Figure 3). The Pohang industrial complex is famous for iron and steel production (10). This iron and steel making plant is an important emission source of DL-PCBs (18) because electric arc furnaces used for scrapping metal can act as a thermal source of DL-PCBs if organic compounds and chlorine are present (19). Siheung and Incheon are also very large industrial complexes in Korea. The majority of the industrial activities in these two areas include production of machinery and electronics (20). The electricity industry could use PCBs as stabilizing additives in plastic coatings of electric components (4). Additionally, both Siheung and Incheon are located in north-west Korea, where DL-PCB levels are high (16), as mentioned above. This might offer an explanation for the high levels of DL-PCBs in these two industrial areas as machinery and electric production should not be important emission sources of PCBs compared to steel production (5). To understand the magnitude of PCB contamination in Korea, the concentrations of PCBs in the atmosphere were compared with those in other countries (Table 1). The average concentration of PCBs in the atmosphere of Korea was 142 pg/m3, which was lower than those measured in China (1,100 pg/m3) and comparable to those obtained in Japan (184 pg/m3) (15). In addition, the average level of DL-PCBs in Gyeonggi-do, Korea (0.016 pg TEQ/m3) (29), was approximately 8 times higher than the concentrations found in an urban area of Italy (0.002 pg TEQ/m3) (30). However, it should be noted that the atmospheric levels of both PCBs and DL-PCBs in Korea exhibited a gradual decline during 2002-2009 (31). In fact, beginning in 2004, KMOE, together with KEPCO and NGOs, conducted several projects to limit the PCB contamination in Korea’s environment (12). The temporal decrease in atmospheric PCBs could be a positive result of these PCB elimination efforts. 197 Loganathan et al.; Persistent Organic Chemicals in the Environment: Status and Trends in the Pacific Basin Countries I ... ACS Symposium Series; American Chemical Society: Washington, DC, 2016.


Figure 2. Spatial distribution of total PCBs in the atmosphere of Korea. The PCB congeners found in Ansan, Pohang, and Cheongju were seven indicator PCBs, di- to hepta-CBs, and mono- to deca-CBs, respectively. Di- to octa-CBs were measured at the other sites. High volume air samplers were deployed in Cheongju, Namhae, Hadong, Anseong, and Seoul. Passive air samplers were used in the other cities. Sampling year: Anseong and Seoul (2001−2002), Cheongju (2003), Namhae and Hadong (2010), Pohang (2007), and the other cities (2008). Data source: Hogarh et al. (15), Baek et al. (18), Yeo et al. (21), Kim et al. (22), and Kim (23).



Figure 3. Spatial distribution of DL-PCBs in the atmosphere of Korea. Passive air samplers were deployed in Pohang and Gwangyang. High volume air samplers were used in the other cities. Sampling year: Gwangyang (2006), Pohang (2008), and the other cities (2009). Data source: Heo et al. (7), Choi et al. (10), Shin et al. (16), Min et al. (24) , Heo and Lee (25), Kim et al. (26), Baek et al. (27), and NIER (28).


Table 1. Levels of PCBs and DL-PCBs in the atmosphere of Korea and other countries Country (Location)

Year

Land use

Mean (range)

Sampling method

Ref


PCBs (Unit: pg/m3) Antarctica

19951996

Remote

33.2

Hi.Vol

(32)

Italy

2000

Background

26.4 (8.09-58.9)

Hi.Vol

(30)

Greece

2000

Rural

92

Hi.Vol

(33)

Italy

2000

Urban

163 (88.9-372)

Hi.Vol

(34)

Greece

2000

Urban

348.6

Hi.Vol

(33)

Germany

2001

Rural

110.57

Hi.Vol

(34)

Turkey

2004

Industrial

1,164

Hi.Vol

(35)

Spain

2006

Industrial

159 (76-297)

Hi.Vol

(36)

China

2008

Nationwide

1,100 (300-2,500)

PAS

(15)

Japan

2008

Nationwide

184 (40-760)

PAS

(15)

Taiwan

2008

Nationwide

317

PAS

(15)

Pakistan

2011

Industrial

120 (34-390)

Hi.Vol

(37)

Vietnam

2013

Nationwide

410.5

PAS

(38)

(Anseong)

19992000

Rural

16.3 a

Hi.Vol

(39)

(Seoul)

19992000

Urban

42.1 a

Hi.Vol

(39)

(Nationwide)

20002002

Urban, Industrial

1,700

-

(40)

(Anseong)

20012002

Rural

70.9

Hi.Vol

(21)

(Pohang)

2007

Semi-rural

48 b

PAS

(18)

PAS

(18)

PAS

(18)

Korea

(Pohang)

2007

Residential

31 (15-43)

b b

(Pohang)

2007

Industrial

152 (138-166)

(Nationwide)

2008

Rural

142 (36.2-350.3)

PAS

(15)

(Nationwide)

2008

Urban

160 (58.7-599.3)

PAS

(15)

(Suwon)

2010

Urban

233.6

Hi.Vol

(41)

(Ansan)

2010

Industrial

274.15

Hi.Vol

(41)

(Southern area)

2010

Industrial

331.5 (311.7-352.6)

Hi.Vol

(23)

Continued on next page.


Table 1. (Continued). Levels of PCBs and DL-PCBs in the atmosphere of Korea and other countries Country (Location)

Year

Land use

Mean (range)

Sampling method

Ref

(Jeonju)

-

Urban

703 (179-2,794)

-

(22)

(Sihwa & Banwol)

-

Industrial

3.26 (2.08-5.82)

Hi.Vol

(42)


DL-PCBs (Unit: pg/m3 and pg TEQ/m3) Canada

1993

Background

1.91

Hi.Vol

(43)

Netherlands

1994

Suburban

3-5

Hi.Vol

(44)

United States

1995

Industrial

13.29

Hi.Vol

(45)

c

Hi.Vol

(30)

Italy

2000

Urban

0.002

Algeria

20082009

Industrial

0.054 c

Hi.Vol

(46)

China

2009

Industrial

0.001-0.018 c

Hi.Vol

(47)

Italy

-

Industrial

0.022

Hi.Vol

(48)

2002

Urban

0.016 (0.019-0.029)c

Hi.Vol

(29)

Hi.Vol

(29)

(0.004-0.13)c

Korea (Gyeonggi-do) (Gyeonggi-do) (Nationwide) (Gyeonggi-do) (Gyeonggi-do) (Gyeonggi-do) (Gyeonggi-do) (Banwol) (Nationwide) (Gyeonggi-do) (Gyeonggi-do)

2002

Industrial

2002 2003 2003 2003 2003 2003

0.0183 Urban Residential Industrial Industrial Industrial

2003 2004 2004

0.097

c

Hi.Vol

(28)

0.010 (0.006-0.026)

c

Hi.Vol

(29)

0.011 (0.003-0.027)

c

Hi.Vol

(24)

0.038 (0.026-0.044)

c

Hi.Vol

(29)

0.039 (0.007-0.113)

c

Hi.Vol

(24)

Hi.Vol

(49)

0.024

c

0.0209 Urban Residential

c

c

Hi.Vol

(28)

0.011 (0.007-0.014)

c

Hi.Vol

(29)

0.011 (0.003-0.029)

c

Hi.Vol

(24)

c

Hi.Vol

(29)

(Gyeonggi-do)

2004

Industrial

0.044 (0.026-0.063)

(Gyeonggi-do)

2004

Industrial

0.041 (0.013-0.163) c

Hi.Vol

(24)

(Nationwide)

2004

0.0101 c

Hi.Vol

(28)

(Gyeonggi-do)

2005

Urban

0.012 (0.007-0.015) c

Hi.Vol

(26)

(Gyeonggi-do)

2005

Residential

0.013 (0.004-0.024) c

Hi.Vol

(24)

(Gyeonggi-do)

2005

Industrial

0.038 (0.031-0.049) c

Hi.Vol

(26)

(Gyeonggi-do)

2005

Industrial

0.044 (0.007-0.171) c

Hi.Vol

(24)





Year

(Nationwide)

2005

(Pohang)

2006

(Pohang)

Land use

Mean (range)

Sampling method

Ref

0.0025 c

Hi.Vol

(28)

Semi-rural

4.8 (0.1-1.5)

PAS

(10)

2006

Rural

1.06-1.96

PAS

(19)

(Gwangyang )

2006

Rural

1.35 (1.16-1.53)

PAS

(27)

(Gyeonggi-do)

2006

Residential

0.008 (0.004-0.024) c

Hi.Vol

(24)

(Pohang)

2006

Residential

2.37-3.08

PAS

(19)

(Pohang)

2006

Residential

3.3 (1.7-5.4)

PAS

(10)

(Gwangyang )

2006

Residential

2.19 (2.18-2.2)

PAS

(27)

Hi.Vol

(24)

c

(Gyeonggi-do)

2006

Industrial

0.028 (0.005-0.143)

(Pohang)

2006

Industrial

0.81-15.6

PAS

(19)

(Pohang)

2006

Steel complex

26.2 (6.1-61.8)

PAS

(10)

(Gwangyang)

2006

Industrial

1.77 (1.5-2.05)

PAS

(27)

(Nationwide)

2006

0.004 c

Hi.Vol

(28)

(Gyeonggi-do)

2007

Residential

0.005 (0.002-0.01) c

Hi.Vol

(24)

(Gyeonggi-do)

2007

Industrial

0.020 (0.007-0.077) c

Hi.Vol

(24)

(Ansan)

2008

Rural

1.42 (1.01-1.97)

Hi.Vol

(7)

(Gyeonggi-do)

2008

Residential

0.006 (0.002-0.013) c

Hi.Vol

(24)

(Ansan)

2008

Urban

4.05 (1.73-5.95)

Hi.Vol

(7)

(Nationwide)

2008

Urban

0.003 (0.002-0.008) c

Hi.Vol

(16)

(Ansan)

2008

Industrial

8.60 (3.82-16.47)

Hi.Vol

(7)

(Sihwa, Gumi, Ulsan, Pohang)

2008

Industrial

0.004 c

Hi.Vol

(50)

(Nationwide)

2008

Industrial

0.003 (0.002-0.007) c

Hi.Vol

(16)

(Gyeonggi-do)

2008

Industrial

0.023 (0.007-0.075) c

Hi.Vol

(24)

(Nationwide)

2008

0.001 (ND-0.016) c

Hi.Vol

(28)

(Gyeonggi-do)

2009

Residential

0.007 (0.003-0.016) c

Hi.Vol

(24)

(Gyeonggi-do)

2009

Industrial

0.013 (0.003-0.024) c

Hi.Vol

(24)

(Nationwide)

2009

0.002 (0-0.012) c

Hi.Vol

(28)

(Suwon)

2010

Urban

0.007 c

PAS

(25)

(Suwon)

2010

Urban

2.28 (0.006) c

Hi.Vol

(41)





Year

Land use

Mean (range)

Sampling method

Ref

(Ansan)

2010

Industrial

0.009 c

PAS

(25)

(Ansan)

2010

Industrial

4.24 (0.023) c

Hi.Vol

(41)

(Ansan)

20012012

-

0.048 c

Hi.Vol

(51)

(Gyeonggi-do)

20092013

Urban, Industrial

0.027 (0.021-0.032) c

-

(52)

“-”: No information; ND: Not detected; PAS: Passive air sampler; Hi.Vol: High volume air sampler. a PCB 28, 52, 101, 118, 138, 153, 180. b PCB 8, 28, 52, 101, 118, 138, 153, 180. c pg TEQ/m3.

Profiles of PCBs and DL-PCBs in the Atmosphere of Korea Spatial Distribution of PCBs and DL-PCBs in the Atmosphere The profiles of PCBs and DL-PCBs in rural, urban, and industrial sites of Korea are illustrated in Figure 4. Generally, the lighter PCBs were the dominant congeners in the atmosphere (18). In fact, the lightly chlorinated congeners, such as mono-, di-, tri-, and tetra-CBs, had high contributions to the total atmospheric PCBs in Korea (Figure 4a). These congeners have a high vapor pressure (53); therefore, the proportion of light PCBs tends to be higher than that of heavy PCBs in the atmosphere. The light PCBs accounted for a higher fraction of the total PCBs in rural areas than in urban areas (Figure 4a) (15, 39). Because the lowmolecular-weight PCBs (mono-, di-, tri-CBs) mostly appear in the gas phase (21), they can potentially move more easily to the remote areas of Korea. The rural, urban, and industrial areas showed relatively similar profiles of DL-PCBs, with a dominance of PCB 118, 105, and 77 (Figure 4b). The congener profiles of PCBs can provide insights into the source signature (10), so these similar profiles imply that these areas could be affected by the same PCB emission sources (10).

Seasonal Variation of PCBs and DL-PCBs in the Atmosphere Figure 5 shows the seasonal variation of PCBs and DL-PCBs in the atmosphere of Korea. The levels of total PCBs were highest in summer (samples were taken in Pohang by PAS, Figure 5a) (18). The warmer temperatures of summer could lead to more evaporation of light PCBs, which have higher vapor pressures and mostly occur in the gas phase. The same trend was also observed in the urban and industrial sites of Gyeonggi-do, South Korea (26). The levels of 203 Loganathan et al.; Persistent Organic Chemicals in the Environment: Status and Trends in the Pacific Basin Countries I ... ACS Symposium Series; American Chemical Society: Washington, DC, 2016.


atmospheric PCBs declined as chlorine substitutions increased (Figure 5a). The vapor pressure of PCBs decreases as the number of chlorine atoms increase (53); hence, the concentration of light PCBs in the atmosphere tends to be higher than that of heavy PCBs.

Figure 4. Composition of (a) total PCBs and (b) DL-PCBs in the atmosphere of Korea. Data for the entire country of Korea, Anseong, and Jeonju were gathered from Hogarh et al. (15), Yeo et al. (21), and Kim et al. (22), respectively. DL-PCB data for Suwon, Pohang, and Ansan were obtained from {Johnson, 2010 #2}Heo et al. (7), Heo and Lee (25), Choi et al. (10), and Heo et al. (7), respectively.

The profiles of PCBs and DL-PCBs showed no significant seasonal or spatial variation (16) (Figures 5b and c). In general, the light congeners (di-, tri-, tetra-, and penta-CBs) were predominant in summer because of volatilization, whereas the relative abundance of heavy PCBs (hexa- and hepta-CBs) was higher in the winter due to condensation. The fractions of tetra- and penta-CBs (PCB 105, 114, 118, and 123 for DL-PCBs) were higher in spring and summer than in winter because the octanol-air partitioning coefficients (KOA) of tetra- and penta-CBs are more temperature-dependent than other PCB congeners (54). Therefore, the fractions of those tetra- and penta-CBs tend to increase when the ambient temperature increases. Moreover, the high contributions of PCB 118, 105, and 77 suggest that evaporation of commercial PCBs could be a major source of DL-PCBs to the atmosphere of Korea (16, 19), as such congeners are the dominant composition of commercial PCBs (55).



Figure 5. Seasonal variation of (a) PCB levels, (b) fractional abundance of PCBs, and (c) fractional abundance of DL-PCBs in the atmosphere of Korea. Data for Pohang, Suwon, and Ansan were gathered from Baek et al. (18), Heo and Lee (25), and Heo et al. (7), respectively.

Gas and Particle Variations of PCBs and DL-PCBs in the Atmosphere Figure 6 illustrates the fractional abundance of PCBs and DL-PCBs in the gas and particle phases. Congeners with three to five chlorine substitutions (tri-, tetra-, and penta-CBs) exist mostly in the gas phase, while congeners having six to 10 chlorine atoms appear mostly in the particle phase (18, 21). This could be because of the differences in vapor pressure and log KOA for light and heavy PCB congeners mentioned above. Urban and industrial sites exhibited relatively similar profiles of DL-PCBs, with a dominance of gaseous PCBs in the summer and spring and particle PCBs in the winter (26). Previous studies reported particle and gas phase PCBs tend to have negative and positive correlations, respectively, with the ambient temperature (21, 26, 49), and indeed, higher temperatures in the summer 205 Loganathan et al.; Persistent Organic Chemicals in the Environment: Status and Trends in the Pacific Basin Countries I ... ACS Symposium Series; American Chemical Society: Washington, DC, 2016.


could lead to more volatilization, which forces the lighter PCBs into the gas phase. The low temperatures of winter favor condensation, which could result in higher contributions of PCBs to the particle phase.

Figure 6. Fractional abundance of the gas and particle phases present in total PCBs at (a) a rural site; DL-PCBs at (b) urban and (c) industrial sites; DL-PCBs in (d) summer and (e) autumn. Samples were taken in Gyeonggi-do using a high-volume air sampler. Data source: Yeo et al. (21) (rural site), Kim et al. (26) (urban and industrial sites), and Kang et al. (49) (summer and autumn).

Source Identification of Atmospheric PCBs Principal component analysis (PCA) has been frequently used for PCB source identification. According to Hogarh et al. (15), most rural and urban sites in Korea were characterized by the low-molecular-weight PCBs having high vapor pressures. The atmospheric PCBs in these areas were mainly derived from combustion and volatilization from contaminated environmental compartments. In warm seasons, the major source was re-emission from the surrounding environment(15, 56). On the other hand, in cold seasons, the main source of atmospheric PCBs was mostly from combustion. Baek et al. (19) and Choi et al. (10) reported that the PCBs at the Pohang industrial complex, the largest steel production plant in Korea, were mainly derived from local combustion. This result was supported by the high fraction of PCB 123, which is formed by combustion processes (19), at the industrial complex. The urban and rural areas of Pohang were believed to be affected by PCBs evaporating from the soil, water, or other surfaces containing PCBs (19).

Polychlorinated Biphenyls (PCBs) in the Soil of South Korea Levels of PCBs and DL-PCBs in the Soil of Korea Figure 7 illustrates the spatial distribution of DL-PCBs and PCBs in soil collected from Korea. In general, the PCB levels in the industrial areas, such as Ulsan, Pohang, Incheon, Sihwa, and Yeosu, were higher than those in the urban and rural areas (28). Among these industrial areas, Ulsan had the highest PCB levels (Figure 7). Ulsan is known as one of the largest industrial cities 206 Loganathan et al.; Persistent Organic Chemicals in the Environment: Status and Trends in the Pacific Basin Countries I ... ACS Symposium Series; American Chemical Society: Washington, DC, 2016.


in Korea, where the main industrial activities include petrochemical, chemical manufacturing, shipbuilding, and automobile production. Petrochemical and shipbuilding activities are regarded as the major PCB emission sources in Ulsan (8, 11). Stable electricity is extremely important to ensure production at the petrochemical plant. Thus, transformers could be widely used for transferring electricity. The transformers in Korea likely contain commercial PCBs, such as Aroclor 1242, 1254, and 1260 (14). Although the addition of PCBs to transformer oil has been restricted since 1979 (8), older transformers containing PCBs could be still in operation (12, 18). Therefore, the use or storage of these transformers could lead to a leakage or spillage of oils containing PCBs. Additionally, shipping and automobile activities in Ulsan were reported to be associated with Aroclor 1260 and 1254 (11). All of these reasons could help explain the extremely high levels of DL-PCBs in Ulsan compared to other places in Korea, as DL-PCB 118 and 105 are the predominant congeners in the commercial PCBs (55). Among the industrial areas, Incheon showed the second-highest levels of PCBs. The majority of industrial activities in Incheon are shipping and machinery production (20). Harbor activities were reported to be the main source of PCB contamination in Incheon (8). The PCB levels in soil collected from Korea and a few other countries are summarized in Table 2. Because the sampling sites, sampling time, and soil properties were different, this is an approximate comparison in an attempt to evaluate the degree of PCB contamination in Korea. Generally, the levels of PCBs and DL-PCBs in the rural, urban, and industrial areas of Korea were lower than those of other countries (28). For instance, the highest value of indicator PCBs measured in Ulsan, one of the largest industrial cities of Korea, was 50.6 ng/g (11). This value was nearly 2 times lower than that of the Seine river basin in France (100.2 ng/g) (57). The level of DL-PCBs in Seoul (urban site, mean: 0.143 pg TEQ/g) was also approximately 16 times lower than that of Iowa, USA (mean: 2.4 pg TEQ/g) (58). In addition, the average level of DL-PCBs in the Sihwa industrial complex (mean: 0.994 pg TEQ/g) (42) was nearly 1.4 times lower than that measured in Slovakia (mean: 1.37 pg TEQ/g) (59) despite Sihwa being one of the largest industrial complexes in Korea, where the main industrial activities include machinery, electronics, petrochemical, and steel production (20). The levels of PCBs could be consistently lower in Korea because PCB production does not occur in Korea (6); thus, the Korean environment has not been contaminated by PCB production compared to other countries where PCBs are produced, such as the USA, France, Italy, or Slovakia (3). The levels of DL-PCBs in Korean soil increased by approximately 100 times from 2002 to 2009 (28). An increasing trend was also noted in soil samples collected in Ulsan from 2011 to 2013 (11). Although the PCB levels in the atmosphere of Korea decreased over time (28), those in the soil exhibited the opposite trend (Table 2). Soil plays an important role in trapping PCBs (57). When being released into the soil, PCBs tend to bind strongly to organic compounds in soils and remain there for a long time, and they are not easily washed out by rain (60). Although PCBs in soil can be transferred into the atmosphere via volatilization (57), this mechanism mostly impacts the light PCBs, which have a lower molecular weight. Meanwhile, the heavy PCBs have a 207 Loganathan et al.; Persistent Organic Chemicals in the Environment: Status and Trends in the Pacific Basin Countries I ... ACS Symposium Series; American Chemical Society: Washington, DC, 2016.


lower vapor pressure (2); hence, they have a tendency to be retained in the soil. Most of DL-PCB congeners are the heavy PCBs (penta-, hexa- and hepta-CBs); therefore, their levels in the soil could increase over time.

Figure 7. Spatial distribution of DL-PCBs and PCBs in soil collected from Korea. Sampling year: Ulsan (2011−2013), Anseong (2015), and the other cities (2009). Data source: Kim et al. (9), Nguyen et al. (11), NIER (28), and Park et al. (42).


Table 2. Total concentrations of PCBs and DL-PCBs in soil collected from Korea and other countries Location

Year

Land use

Mean (Range)

Ref

France

Seine river basin

2000

Suburban

1.49 a

(57)

China

Hong Kong

2000

Urban

4.81 (1.62-9.87) a

Country


PCBs (ng/g)

(61)

France

Seine river basin

2000

Industrial

100.2

Turkey

Aliaga

2004

Rural

0.23

(35)

Turkey

Aliaga

2004

Industrial

805

(35)

Spain

Tarragona

2005

Industrial

4.673 a

(62)

USA

Iowa

2008

Urban

56 (3-1,200)

(58)

a

(57)

China

Beijing

2008

Urban

11.7 (

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