Environmental Geochemistry and Health

, Volume 39, Issue 2, pp 279–291 | Cite as

Monitoring and risk assessment of polychlorinated biphenyls (PCBs) in agricultural soil from two industrialized areas

  • Leesun Kim
  • Jin-Woo Jeon
  • Ji-Young Son
  • Min-Kyu Park
  • Chul-Su Kim
  • Hwang-Ju Jeon
  • Tae-Hoon Nam
  • Kyeongsoon Kim
  • Byung-Jun Park
  • Sung-Deuk Choi
  • Sung-Eun Lee
Original Paper

Abstract

For monitoring and risk assessment, levels and distributions of Σ29 PCBs in paddy soil samples collected from Gwangyang (10 sites) and Ulsan (20 sites), heavily industrialized cities in Korea, were investigated using high-resolution gas chromatography/high-resolution mass spectrometry. Overall, total concentrations of Σ29 PCBs in Gwangyang (216.4–978.6 pg g−1 dw) and Ulsan (273.8–1824.1 pg g−1 dw) were higher than those (106.6–222.6 pg g−1 dw) in agricultural soil from Anseong in Korea. The TEQ (toxic equivalency) values from Gwangyang (0.06–0.40 ng TEQ kg−1 dw) and Ulsan (0.06–0.22 ng TEQ kg−1 dw) were higher than those (0.04–0.11 ng TEQ kg−1 dw) in Anseong but lower than the WHO threshold level (20 ng TEQ kg−1). However, one of the most toxic congeners, PCB 126, gave the highest concentration, possibly posing a risk to the biota. Seven indicator PCB congeners contributed to 50–80% of the total concentration of Σ29 PCBs, indicating the 7 PCBs can be used as valuable indicators for monitoring. The principal component analysis and cluster analysis for the homologue profiles of PCBs indicated that all the samples from both cities had the similar PCB contamination patterns, and the major sources of the PCB contamination were most likely from the usage of Aroclor 1254 than those of Aroclors 1242 and 1260. These PCB technical mixtures were possibly significantly used by various industries including iron and steel industries in Gwangyang and petrochemical and shipbuilding industries in Ulsan.

Keywords

Industrialized area Monitoring Polychlorinated biphenyls Ulsan Gwangyang 

Introduction

The mixtures of polychlorinated biphenyls (PCBs), classified as persistent organic pollutants (POPs), had been synthesized for various electric products including transformer oils or hydraulic fluids since the late 1920s (Barbalace 2003). From 1930 to 1993, 1.3 Mt of PCB was globally produced in some countries (USA, Germany, Russian, France, UK, Japan, Italy, Spain, Czechoslovakia, China, and Poland) (Breivik et al. 2007). Despite the limited production or the ban of PCBs since the late 1970s’ due to their toxicity around the world including Korea, the industrial equipment containing PCBs has been still used for various purposes (Shin and Kim 2006; Devi et al. 2014). It should be noticed that the large amount of PCBs has been released into the environment, especially during the industrial activities, and the congeners readily accumulate in the environmental media (e.g., soil or sediment) especially in the surrounding areas due to their persistency. The total emission of PCBs (Σ22 PCBs) between 1930 and 2016 was globally 0.1 Mt (Breivik et al. 2007). In this context, the researchers in many countries have actively carried out the monitoring PCBs in the atmosphere, water, soil, and sediments (Zhao et al. 2016; Devi et al. 2014; Howell et al. 2011) to prevent harmful effects on human health as well as the ecological system.

Previous studies in many countries demonstrated that the concentrations of PCBs in surface soil were strongly linked with proximity to the source areas (Zhao et al. 2016; Devi et al. 2014; Nguyen et al. 2016). Many researchers demonstrated that the higher PCB levels in the environment were attributed to the historical usage or inadequate wastes management of PCBs-related goods. According to the report (Meijer et al. 2003), the levels of Σ29 PCBs in Greenland and mainland Europe were 26–97,000 pg g−1 dw (dry weight) in the background soil samples collected from the 191 sites far from industrialized/populated/agrochemical application regions. These results clearly demonstrated that background soil was also contaminated with various PCB congeners. An average concentration of Σ51 PCBs from 52 sites across China was 515 pg g−1 dw in the surface soil collected from background (4 sites), rural (39 sites), and urban (9 sites) areas in 2005 (Ren et al. 2007). The research on levels and distributions of PCBs in air and soils in Manipur, India, was performed to identify possible sources and examine the role of soils on atmospheric PCBs caused by ship dismantling facilities along the Indian Ocean (Devi et al. 2014). The study indicated that the level of Σ25 PCBs (34,740 pg g−1) in urban areas during pre-monsoon was higher than those in mountain (21,290 pg g−1) and rural areas (19,150 pg g−1), possibly attributed to high levels of soil organic carbon. Some sites with high PCB concentrations in rural areas were possibly because of the uncovered combustion of various solid wastes (Devi et al. 2014). The recent study from China showed the high concentrations, distribution, and toxic risks of PCBs in sediment/soil profiles from three different types of wetlands down the Pearl River estuary as a part of a 100-year chronosequence of reclamation (Zhao et al. 2016). The concentrations of Σ15 PCBs (17.7–169.3 ng g−1) determined in this estuary were much higher than those in background soils possibly due to rapid development and urbanization with a growing population. On the basis of the sediment quality guideline, the average concentrations of total PCBs surpassed the threshold effects level (21.6 ng g−1), indicating possible negative biological consequences, mainly caused by light PCB congeners (Zhao et al. 2016).

In Korea, 0.3 tons of Σ22 PCBs were released from 1946 to 2015; PCBs had been never manufactured in Korea but imported and used for various industrial purposes (Breivik et al. 2007). According to the National Institute of Environmental Research (NIER) in Korea, PCB concentrations in 33 transformer oils used in Korea ranged from ND (not detected) to 48.3 mg kg−1, and PCBs in the transformers were derived from technical mixtures, Aroclors 1242, 1254, and 1260 (Shin and Kim 2006). The PCB levels in soil (Nguyen et al. 2016), air (Baek et al. 2010), and marine sediment (Moon et al. 2008) from the industrial cities of Gwangyang, Ulsan, and Pohang in Korea have drawn attentions since the main industries in those cities (e.g., iron and steel plants and shipyard) are closely associated with the distribution and increased levels of PCBs in adjacent areas. The PCB research on soil from rural, urban, and industrial sites in Ulsan, Korea, demonstrated that the concentration of seven PCB indicator congeners were slightly higher than those in other nations or other places in Korea, and the contamination may be strongly related to the surrounding industrial complexes (Nguyen et al. 2016). However, not many studies did pay attention to PCB levels in specifically paddy soils even though rice is the main staple in Korea. Considering that PCBs can be moved into the grains, a better understanding of the levels and distributions of PCBs in paddy soils is required to contribute to reduce the risk of public health and ecosystems. The recent study on PCBs in agricultural soil samples from Anseong in Korea indicated that the concentrations of Σ29 PCBs nearby a transformer oil-related factory ranged from 106.65 to 222.67 pg g−1 dw (Kim et al. 2016).

This current research was designed to better understand the distribution and levels of PCBs in paddy soil sites in the vicinity of the heavily industrialized cities, Gwangyang (10 sites) and Ulsan (20 sites) in Korea. High-resolution gas chromatography/high-resolution mass spectrometry (HRGC/HRMS) was used to determine the concentration of Σ29 PCBs in rice paddy soil samples from both regions. The total concentrations of PCBs and the concentration of the selected individual PCB congener from these areas were compared with the paddy soil samples nearby a PCB-related factory from Anseong in Korea as background soil (Kim et al. 2016).

Materials and methods

Soil sampling

Soil samples (0–10 cm) were collected in rice paddies in Gwangyang (10 sites) and Ulsan (15 sites). In Gwangyang, with a population of 0.15 million, one of the world biggest steel and iron plants has been operated since 1987. On the other hand, Ulsan has been industrialized since 1972 and now is the industrial capital of South Korea with a population of 1.1 million. The world largest automobile assembly plant and shipyard as well as the world’s second largest oil refinery are located in Ulsan. Each site from both cities was located nearby industrial areas. The location of each site is shown in Fig. 1a (Gwangyang) and b (Ulsan), and grid references are listed in Tables S1 (Gwangyang) and S2 (Ulsan). According to the official test method for soil contamination suggested by the Korean Ministry of Environment, after removing overlying vegetation, soil samples (approx. 0.2 kg) were collected from 10 points in the ‘Z’ shape and placed into a plastic bag in March, 2016. In the laboratory, the air-dried samples were passed through a 2-mm sieve before the PCB analysis.
Fig. 1

Location of sampling sites from a Gwangyang and b Ulsan in Korea

Sample preparation

The analytical methods for the sample preparation and instrumental analysis were adopted from our previous study (Kim et al. 2016). Each soil sample (10 g) was mixed with 40 g of sodium sulfate to remove water trace from soil, and surrogate standards (68B-LCS, Wellington Laboratories, Canada) were added to the soil sample. The Soxhlet extraction was run with dichloromethane (350 mL) over 16 h. The extracts were then concentrated using a rotary evaporator and exchanged into n-hexane. For cleanup procedure, the extracts were eluted with n-hexane (150 mL) on multilayer silica gel (silica gel 60, Merck, Germany) columns—from bottom to top: 0.9 g of activated silica gel, 3 g of basic silica gel (2% KOH), 0.9 g of silica gel, 4.5 g of acidic silica gel (44% H2SO4), 6 g of acidic silica gel (22% H2SO4), 0.9 g of activated silica gel, 3 g of silver nitrate silica gel (10% of AgNO3), and 6 g of sodium sulfate. The eluate was evaporated using a rotary evaporator and a gentle stream of nitrogen and then exchanged into nonane. The final sample volume was 50 μL for the instrumental (HRGC/HRMS) analysis. Internal standards (68B-IS, Wellington Laboratories, Canada) were added to GC vials (2 mL) prior to GC injection.

Instrumental analysis and QA/QC

The sample analysis was carried out using a gas chromatograph (Agilent Technologies 7890A, USA) coupled with a high-resolution mass spectrometer (Waters Autospec Premier™, UK). A nonpolar capillary column (DB-5MS, 50 m × 0.25 mm i.d. × 0.25 μm film thickness, Agilent Technologies, USA) was used to separate the target compounds. The inlet temperature was 300 °C, and the oven temperature was initially set at 90 °C (held for 1 min), raised into 170 °C at 20 °C min−1 (held for 4 min), raised into 280 °C at 3.5 °C min−1, and lastly raised into 320 °C at 50 °C min−1 (held for 8.8 min). The temperatures of transfer line and source ion were set at 320 and 250 °C, respectively. The prepared sample (1 µL) was injected into the GC system in splitless mode. The carrier gas was helium, and flow rate was 1.1 mL min−1. With the electron impact ionization (EI) mode, mass spectra were obtained by 35 eV. The HRMS system was operated at a resolution of 10,000, and data were recorded in the selected ion monitoring mode. The concentrations of PCBs were determined based on the criteria reported by the US EPA (method 1668C) and quantified by the isotope dilution method using calibration standards (EC9605-CVS and 68C-CVS, Wellington Laboratories, Canada). The 29 PCB congeners with IUPAC numbers of PCB 18, 28, 33, 44, 52, 70, 77, 81, 101, 105, 114, 118, 123, 126, 128, 138, 153, 156, 157, 167, 169, 170, 180, 187, 189, 194, 195, 199, and 206 were analyzed, and the recoveries of the surrogate standards were in the range from 50 to 120%.

Calculation of toxic equivalency quantities (TEQ)

In this study, the formula of toxic equivalents (TEQ) defined by the World Health Organization (WHO 1998) was adopted for risk assessment of the PCB contamination in soil from Gwangyang and Ulsan. The TEF and TEQ notions were introduced to expedite the monitoring and risk assessment of dioxin-like compounds like PCBs in a wide range of research. TEQ is determined through addition of the concentrations of individual analytes (Ci) multiplied by its relative toxicity (TEFi: toxicity equivalent factors for individual compounds).
$${\text{TEQ}} = \varSigma [Ci] \times {\text{TEF}}i$$

Principal component analysis (PCA) and cluster analysis (CA)

Two hypotheses were formulated. First, each sampling site from each city has similarity, but two cities have less similarity in terms of the contamination source. Second, the major sources in both regions were possibly Aroclors 1254 and 1260 used by the industries in both cities. In order to test these hypotheses for soil samples, both principal component analysis (PCA) and clustering analysis (CA) were carried out using a statistical package for the social sciences (IBM SPSS 20, USA). They are commonly used multivariate statistical methods in a wide range of environmental analysis (Aly Salem et al. 2013; Motelay-Massei et al. 2004; Nguyen et al. 2016).

Using profiles of each PCB homologue group (tri-, tetra-, penta-, hexa-, hepta-, octa-, and nonaCBs) acquired from this study and those of Aroclors 1242, 1254 and 1260 obtained from the previous study (Frame et al. 1996), the statistical analyses (PCA and CA) were carried out. Different types of Aroclors 1242, 1254, and 1260 were used for the statistical analysis to confirm the similarity among the Aroclor products. The concentrations of each homologue were normalized by the concentration of Σ29 PCBs for each sample. The results from PCA and CA were used for the source identification of PCBs in both regions. In order to evaluate the PCB concentration differences between two cities, rank sum test was carried out using SigmaPlot 12.5 (Systat Software, USA).

Results and discussion

Total concentrations of PCBs in Gwangyang and Ulsan

The concentration of Σ29 PCBs is shown in Table 1, and the full data set is provided in Tables S3 (Gwangyang) and S4 (Ulsan), respectively. Overall, the concentrations of Σ29 PCBs (221–979 pg g−1 dw) in Gwangyang (Table 1) were lower than those (274–1824 pg g−1 dw) in Ulsan but higher than those (107–223 pg g−1 dw) in Anseong (Kim et al. 2016). The total concentrations from both cities were lower than that of Σ6 PCBs (950–3,340 pg g−1 dw) in agricultural land from Leipzig-Halle (Germany) (Manz et al. 2001) but similar to that of Σ6 PCBs (500–900 pg g−1 dw) in agricultural area from Yangtze River Delta (China) (Shi et al. 2015). Based on the high-risk PCB level for residential soil (0.23 mg kg−1) and industrial soil (0.94 mg kg−1) set by US EPA, the concentrations from both cities are not high-risk level (EPA 2016). However, considering that the sampling sites in Gwangyang are located nearby a large-scale iron and steel plant, open in 1987, the higher levels of PCBs in the soil samples compared with those in background soil were possibly attributed to historical release of the large quantities of PCBs into the environment. These results were consistent with the previous studies, showing the iron and steel making industry has been identified as a major source of dioxin-like (DL) PCBs in the atmosphere (Baek et al. 2010; Buekens et al. 2001). On the other hand, given that Ulsan has become an industrial city since 1972, the higher levels of PCB contamination than those in the background and Gwangyang soils were possibly due to a longer history of various industrial productions such as shipbuilding, petrochemical, and chemical processes (Nguyen et al. 2016; Shin and Kim 2006). The statistical test also confirmed that the concentration of PCBs in Ulsan were significantly higher than those in Gwangyang (Mann–Whitney rank sum test, p < 0.05).
Table 1

Concentrations of individual 7 indicator PCBs (28, 52, 101, 118, 138, 152, and 180) and total concentration of 29 PCBs obtained from Gwangyang and Ulsan sampling sites

Sampling site

Indicator PCB (pg g−1)

Σ7 PCBs (pg g−1)

Σ29 PCBs (pg g−1)

#28

#52

#101

#118

#138

#153

#180

Gwangyang

1

24.2

10.1

18.5

19.9

29.5

24.9

14.5

141.7

231.1

2

39.9

18.6

18.2

21.4

24.1

26.9

15.6

164.8

294.5

3

41.3

16.0

18.5

18.9

20.7

24.0

13.6

153.0

259.4

4

37.4

23.7

92.3

85.2

126.1

158.5

97.0

620.1

978.6

5

20.2

13.6

30.8

31.8

38.0

43.6

20.0

198.1

322.7

6

21.2

10.3

23.5

25.3

30.5

35.1

17.1

163.0

261.5

7

40.5

15.1

17.3

16.2

15.8

17.4

6.8

129.1

221.1

8

24.9

11.2

19.4

20.3

29.0

28.0

17.5

150.3

248.1

9

28.5

15.9

290.8

28.8

38.7

37.9

19.3

459.9

577.7

10

24.1

12.9

26.7

30.3

43.2

49.2

29.4

215.8

349.4

Ulsan

1

41.8

19.8

37.7

35.4

60.4

72.1

52.7

320.1

598.7

2

37.7

19.9

70.8

27.9

51.1

52.7

36.3

296.3

465.6

3

41.9

19.4

41.8

40.6

77.5

95.4

73.5

390.2

674.0

4

41.6

18.0

35.1

33.0

57.4

74.2

57.1

316.4

532.2

5

39.5

18.3

34.2

33.6

74.2

90.4

76.7

367.0

607.4

6

46.8

23.3

48.8

45.2

83.2

95.6

80.2

423.0

686.0

7

31.4

12.8

32.7

32.1

58.0

58.5

37.6

263.1

419.5

8

36.5

18.8

40.2

37.5

69.4

86.7

75.6

364.8

586.0

9

46.5

26.5

51.8

45.2

80.7

96.7

71.1

418.5

672.3

10

45.9

19.4

26.1

44.5

28.8

27.1

14.3

206.2

374.8

11

36.6

14.5

20.8

19.7

28.8

31.3

17.4

169.2

273.8

12

57.6

26.8

30.2

30.4

47.2

47.3

34.2

273.7

469.0

13

49.6

21.3

45.6

41.8

64.8

85.0

70.2

378.3

633.5

14

46.6

16.9

29.1

29.6

52.2

65.3

58.6

298.3

509.0

15

38.8

14.7

23.0

22.2

34.0

47.1

42.7

222.5

383.5

16

38.8

14.3

35.9

38.0

62.6

80.8

58.9

329.3

536.7

17

31.4

13.9

32.3

34.3

59.2

74.0

57.7

303.0

507.2

18

43.3

13.7

22.5

22.3

31.1

36.8

20.0

189.6

310.8

19

123.5

47.8

57.3

55.4

78.7

71.1

40.1

474.0

797.1

20

402.7

88.6

76.1

76.5

114.4

163.5

144.9

1066.7

1824.1

In Gwangyang, site 4 (979 pg g−1 dw) and site 9 (578 pg g−1 dw) showed the highest concentrations possibly due to the closest location to the industry. Among all PCB congeners detected, PCBs 101, 118, 138, 153, and 180 were dominant (mean: 26. 7–49.2 pg g−1 dw). It may be strongly related to the historical use of commercial PCB mixtures and unintentional emissions and also as a result of their lengthy half-life (approximately 10 years for PCB 101, 7 years for PCB 118, and 18 years for both PCB 138 and 153) (Sinkkonen and Paasivirta 2000). These PCBs with large numbers of chlorines are resistant to biodegradation, while light PCBs tend to be more water soluble or volatile, and more easily metabolized.

In Ulsan, the samples from sites 20 (1824 pg g−1 dw) and 19 (797 pg g−1 dw), located close to the shipbuilding and heavy industry, showed the highest concentrations. Out of 29 PCB congeners, PCB 28, 138, 153, and 180 were dominant in the most sampling sites. These congeners are known to persist in soil due to their long residence time (approximately 3 years for PCB 28) (Sinkkonen and Paasivirta 2000).

Toxic equivalency quantities of 12 DL PCBs and indicator PCBs

It is vital to determine the concentration of an individual PCB congener because the structure of individual congeners is intensely linked with their toxicological potency. TEQ values for 12 dioxin-like PCBs (DL PCBs) at each site from Gwangyang and Ulsan were calculated based on the TEQ calculation formulae. The TEF value of 12 DL PCBs ranged from 0.00001 to 0.1 designated by WHO because each congener has different degree of toxicity (Van den Berg et al. 2006). The TEQ values from Gwangyang ranged from 0.05 to 0.41 pg TEQ g−1 dw, while those from Ulsan ranged from 0.06 to 0.22 pg TEQ g−1 dw. The values from both cities were mainly due to 3,3′,4,4′,5-pentaCB (126), with TEF of 0.1, the highest value out of TEF values of 12 PCB congers. Each TEQ value is shown in Tables 2 (Gwangyang) and 3 (Ulsan). The TEQ values from both regions remained lower than the action level of 20 ng WHO-TEQ kg−1 (Andersson et al. 2011).
Table 2

Toxic equivalency quantities of 12 PCBs detected in Gwangyang

Compounds (IUPAC NO.)

PCBs concentration (pg TEQ g−1) for each sampling site

1

2

3

4

5

6

7

8

9

10

Non-ortho-substituted PCBs

3,3′,4,4′-TetraCB (77)

0.0005

0.0005

0.0005

0.0013

0.0007

0.0005

0.0004

0.0005

0.0005

0.0006

3,4,4′,5-TetraCB (81)

0.0001

0.0001

0.0001

0.0004

0.0003

0.0001

0.0001

0.0001

0.0001

0.0001

3,3′,4,4′,5-PentaCB (126)

0.0434

0.0859

0.0659

0.3542

0.2081

0.0726

0.0458

0.1436

0.0978

0.0881

3,3′,4,4′,5,5′-HexaCB (169)

0.0099

0.0160

0.0096

0.0463

0.0272

0.0116

0.0108

0.0221

0.0164

0.0082

Mono-ortho-substituted PCBs

2,3,3′,4,4′-PentaCB (105)

0.0001

0.0002

0.0002

0.0004

0.0002

0.0001

0.0001

0.0002

0.0002

0.0002

2,3,4,4′,5-PentaCB (114)

0.0000

0.0000

0.0000

0.0000

0.0000

0.0000

0.0000

0.0000

0.0000

0.0000

2,3′,4,4′5-PentaCB (118)

0.0006

0.0006

0.0006

0.0026

0.0010

0.0008

0.0005

0.0006

0.0009

0.0009

2′,3,4,4′5-PentaCB (123)

0.0000

0.0000

0.0000

0.0001

0.0000

0.0000

0.0000

0.0000

0.0000

0.0000

2,3,3′,4,4′5-HexaCB (156)

0.0001

0.0001

0.0001

0.0005

0.0002

0.0001

0.0000

0.0001

0.0001

0.0002

2,3,3′4,4′,5′-HexaCB (157)

0.0000

0.0000

0.0000

0.0001

0.0000

0.0000

0.0000

0.0000

0.0000

0.0000

2,3′,4,4′5,5′-HexaCB (167)

0.0001

0.0001

0.0000

0.0003

0.0001

0.0001

0.0000

0.0001

0.0001

0.0001

2,3,3′,4,4′,5,5′-HeptaCB (189)

0.0000

0.0000

0.0000

0.0001

0.0000

0.0000

0.0000

0.0000

0.0000

0.0000

Total

0.0548

0.1036

0.0771

0.4062

0.2378

0.0860

0.0578

0.1674

0.1162

0.0984

Table 3

Toxic equivalency quantities of 12 PCBs detected in Ulsan

PCBs

PCBs Concentration (pg g−1) for each sampling site

1

2

3

4

5

6

7

8

9

10

11

12

13

14

15

16

17

18

19

20

Non-ortho-substituted PCBs

77

0.0087

0.0008

0.0010

0.0006

0.0006

0.0009

0.0006

0.0008

0.0009

0.0008

0.0004

0.0008

0.0018

0.0010

0.0006

0.0017

0.0011

0.0008

0.0014

0.0030

81

0.0001

0.0001

0.0001

0.0000

0.0000

0.0001

0.0001

0.0002

0.0001

0.0001

0.0001

0.0001

0.0001

0.0000

0.0000

0.0000

0.0000

0.0000

0.0001

0.0001

126

0.1968

0.0690

0.0937

0.0816

0.1076

0.1279

0.0699

0.0975

0.1261

0.1189

0.0567

0.0706

0.1722

0.0798

0.0610

0.1279

0.0874

0.0546

0.1192

0.1721

169

0.0124

0.0052

0.0144

0.0000

0.0125

0.0129

0.0052

0.0051

0.0069

0.0000

0.0066

0.0000

0.0156

0.0066

0.0094

0.0139

0.0071

0.0088

0.0000

0.0170

Mono-ortho-substituted PCBs

105

0.0005

0.0004

0.0006

0.0004

0.0005

0.0006

0.0005

0.0005

0.0005

0.0007

0.0003

0.0005

0.0006

0.0004

0.0003

0.0005

0.0004

0.0003

0.0007

0.0012

114

0.0000

0.0000

0.0001

0.0000

0.0000

0.0000

0.0000

0.0000

0.0001

0.0001

0.0000

0.0001

0.0000

0.0000

0.0000

0.0000

0.0000

0.0000

0.0001

0.0000

118

0.0011

0.0008

0.0012

0.0010

0.0010

0.0014

0.0010

0.0011

0.0014

0.0013

0.0006

0.0009

0.0013

0.0009

0.0007

0.0011

0.0010

0.0007

0.0017

0.0023

123

0.0000

0.0000

0.0000

0.0000

0.0000

0.0000

0.0000

0.0000

0.0000

0.0000

0.0000

0.0000

0.0000

0.0000

0.0000

0.0000

0.0000

0.0000

0.0000

0.0000

156

0.0002

0.0002

0.0002

0.0002

0.0002

0.0003

0.0002

0.0002

0.0003

0.0002

0.0001

0.0001

0.0002

0.0002

0.0001

0.0002

0.0002

0.0001

0.0003

0.0004

157

0.0001

0.0000

0.0001

0.0000

0.0001

0.0000

0.0000

0.0000

0.0001

0.0001

0.0000

0.0000

0.0001

0.0000

0.0000

0.0001

0.0000

0.0000

0.0001

0.0001

167

0.0001

0.0001

0.0001

0.0001

0.0001

0.0001

0.0001

0.0001

0.0001

0.0001

0.0000

0.0001

0.0001

0.0001

0.0001

0.0001

0.0001

0.0000

0.0001

0.0002

189

0.0000

0.0000

0.0000

0.0000

0.0000

0.0000

0.0000

0.0000

0.0000

0.0000

0.0000

0.0000

0.0001

0.0000

0.0002

0.0004

0.0003

0.0002

0.0000

0.0001

0.2199

0.0766

0.1116

0.0840

0.1226

0.1444

0.0776

0.1056

0.1365

0.1224

0.0648

0.0733

0.1920

0.0892

0.0723

0.1461

0.0978

0.0655

0.1237

0.1965

*∑: total

However, it should be noted that a variety of previous research reported the toxicity of the DL PCBs in both humane and biota. The DL PCBs are able to bind the aryl hydrocarbon receptor (AHR), causing the full range of toxic responses displayed by dioxin, 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) (Van den Berg et al. 1998). The non-ortho-substituted PCBs (PCB 77, 81, 126, and 169) show dioxin-like toxicity in fish, birds, and mammals. In particular, the contribution of PCB 126 (a worldwide-spread dioxin-like pollutant) and 169 to TEQ values was dominant in Gwangyang, while the contribution of PCB 126 to TEQ values was dominant in Ulsan. Both congers have relatively high TEF values, i.e., 0.1 and 0.01, respectively. It was reported that exposure to PCB 126 in female rats damaged serum cholesterol levels, elevated blood pressure, and caused development of the myocardium (Lind et al. 2004). The mono-ortho chlorinated DL PCBs have lower TEF values (0.00001–0.00003) than PCB 126 and 169 but are also able to activate the AHR, causing dioxin-like responses in birds and mammals except fish. As the levels of these mono-ortho chlorinated DL PCB congeners in both cities were not high, they did not significantly contribute to the TEQ values.

Unlike DL PCBs, non-dioxin-like PCBs show different toxic characteristics, but seven indicator PCBs (PCB 28, 52, 101, 118, 138, 153, and 180) have been frequently monitored since they were selected mainly by ICES (International Council for the Exploration of the Sea) working groups due to their relatively uncomplicated identification, quantification in gas chromatograms, and higher contribution to the total PCB content in environmental samples. In addition, they are listed as compulsory contaminants that should be analyzed and reported within both the HELCOM (Baltic Marine Environment Protection Commission- Helsinki Commission) and OSPARCOM (Oslo and Paris Conventions monitoring programmes) conventions and classified as POPs under the Stockholm Convention. Indicator PCBs have been used as possible representatives for all the PCBs in the environmental or food samples in a wide range of research (Atuma et al. 1996; Nguyen et al. 2016; Fierens et al. 2007). In this study, indicator PCBs in both cities composed 50–80% out of the concentrations of Σ29 PCBs (Figs. 1, 2). Therefore, the congeners can be used as valuable indicators for risk assessment or monitoring. PCB 153 (2,2′,4,4′,5,5′-hexachlorobiphenyl) constituted 10–16% of the concentrations of Σ29 PCBs in both Gwangyang and Ulsan. This result was consistent with the results from the previous study about PCB concentrations in fish (11–14% in various fish such as white fish, sea trout, salmon, perch, eel, and char) from Sweden (Atuma et al. 1996). The result from the current study confirmed the possibility of using PCB 153 as a valued indicator for total PCB monitoring. Note that the congener (PCB 153) is a major component (15–30% of total PCBs) in most human samples (e.g., serum) as well as environmental media (Longnecker et al. 2003) (Fig. 3).
Fig. 2

Proportions of 7 PCB congeners (indicators) and PCB 153 concentrations of Σ29 PCBs from Gwangyang

Fig. 3

Proportions of 7 PCB congeners (indicators) and PCB 153 concentrations of Σ29 PCBs from Ulsan

Homologue patterns and possible source identification of PCBs

PentaCBs (mean 24.7%) and hexaCBs (mean 26.3%) were more abundant than other homologues determined at all the sites in Gwangyang (Fig. 4), and then, tetraCBs (mean 17.2%) and heptaCBs (mean 13.4%) were the second abundant. On the other hands, in Ulsan, hexaCBs (mean 27.5%) and heptaCBs (mean 19.4%) were the most abundant homologues (Fig. 5), and tetraCBs (15.7%) and pentaCBs (mean 17.3%) were the second most abundant.
Fig. 4

Profiles of each PCB congener group in Gwangyang

Fig. 5

Profiles of each PCB congener group in Ulsan

For source identification, the proportions of each homologue group in commercial mixtures, those in soil samples in Gwangyang and Ulsan, were compared. Among various commercial mixtures, Aroclors 1242, 1254, and 1260 (Frame et al. 1996) were selected because they were dominant in commercial products containing PCBs in Korea (Shin and Kim 2006). Considering that high percentages of pentaCBs were detected in the samples from Gwangyang (mean 24.7%) and Ulsan (mean 17.3%), the PCB homologue patterns of two cities were more similar to that of Aroclor 1254 than those of Aroclors 1260 and 1242.

The result of PCA is shown in Fig. 6, and the first and second principal components accounted for 65 and 27% of variance, respectively. The score plot indicated that the soil samples from both regions were closely related to each other and Aroclors 1254 (1 and 2). The loading plot indicated tetra-, penta-, and hexaCBs mostly contributed to the soil samples and Aroclors 1254. In these plots, Aroclors 1260 were characterized by octaCBs and Aroclors 1242 by triCBs and tetraCBs.
Fig. 6

Principal component analysis (PCA) performed based on profiles of each homologue group (tri-, tetra-, penta-, hexa-, hepta-, octa-, and nonaCBs) obtained from this study and those of Aroclors 1242 (1, 2, and 3), 1254 (1 and 2) and 1260 (1, 2, and 3) from the previous study (Frame et al. 1996). These Aroclors were produced from the different companies (1. AccuStandard, 2. Supelco, and 3.GE corporate R&D), even though they have the same number

The CA result (Fig. 7) was also obtained using profiles of both cities and Aroclors. The dendrogram indicated that Gwangyang, Ulsan, and Aroclors 1254 (1 and 2) were clustered (group 1). Aroclors 1260 (1, 2, and 3) and Aroclors 1242 (1, 2, and 3) were clustered groups 2 and 3, respectively, because the PCB composition of each Aroclor with the same number are slightly different (Buekens et al. 2001). Group 1 (Gwangyang, Ulsan, and Aroclors 1254) were further clustered with group 2 (Aroclors 1260). This result suggested that Gwangyang and Ulsan were more influenced by Aroclors 1254 rather than Aroclors 1260 and 1242. Therefore, the CA results were consistent with the result from PCA.
Fig. 7

Clustering analysis (CA) carried out using profiles of each homologue group (tri-, tetra-, penta-, hexa-, hepta-, octa-, and nonaCBs) obtained from this study and those of Aroclors 1242 (1, 2, and 3), 1254 (1 and 2) and 1260 (1, 2, and 3) from the previous study (Frame et al. 1996). These Aroclors were produced from the different companies (1. AccuStandard, 2. Supelco, and 3.GE corporate R&D), even though they have the same number

Considering that the soil samples were collected from rice paddies nearby one of the biggest shipping industrial plant, it is considered that the shipyard is one of the major sources for PCB contamination surrounding agricultural land and Aroclor 1254 was possibly used for shipping activities, automobile assembly plants, and shipyard. The result from this study was supported by the previous studies on Ulsan bay, indicating that pentaCB and hexaCBs were the most abundant homologues in marine sediments (Moon et al. 2008). Many studies also demonstrated the ship breaking, petrochemical refinery, and iron and steel processing plants were major sources for PCB contamination (Kaya et al. 2012; Moon et al. 2008; Nguyen et al. 2016). The recent study (Kaya et al. 2012) from Turkey showed that the major contributors to PCBs in air and soil from the industrial area were iron and steel plants and ship breaking activities.

Conclusions

In this research, the levels of Σ29 PCBs in paddy soil samples were determined in the vicinity of two heavily industrialized cities, Gwangyang and Ulsan in Korea. The PCB levels in Ulsan (20 sites) were statistically higher than those in Gwangyang (10 sites). This result clearly demonstrated that the accumulation of PCBs in paddy soils was derived from the long historical usages of PCB-related equipment by different types of heavy industries including shipbuilding, oil refinery, and car assembly plant. For source identification, both PCA and CA results confirmed that the PCBs contamination patterns in both cities were very similar and the contamination was most likely derived from Aroclors 1254 which have been possibly used by the industries including iron and steel (Gwangyang), petrochemical, and shipbuilding industries (Ulsan) in both cities. However, PCB contamination levels in both cities were not high-risk levels compared with the values US EPA suggested for the rural area, and the TEQ values from Ulsan and Gwangyang were also lower than the WHO action level. Considering that rice is the main staple in Korea, the findings can be used as important indicators for farmers because the PCBs in paddy soil can be possibly transferred into rice grown this area. In particular, as seven indicator PCBs have high proportions (50–80%) out of Σ29 PCBs in both industrial areas and PCB 153 contributed 10–16% to Σ29 PCBs, the determination of the PCB levels in rice harvested this area is strongly recommended. Given that PCBs can be bioaccumulated into food chain, posing a risk to the biota, the continuing monitoring of agricultural lands are also strongly recommended.

Notes

Acknowledgements

This research was carried out under the Cooperative Research Program for Agricultural Science & Technology Development (Project No. PJ010922032015), Rural Development Administration, Republic of Korea.

Compliance with ethical standards

Conflict of interest

The authors have declared that no competing interests exist.

Supplementary material

10653_2017_9920_MOESM1_ESM.docx (40 kb)
Supplementary material 1 (DOCX 39 kb)

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Copyright information

© Springer Science+Business Media Dordrecht 2017

Authors and Affiliations

  • Leesun Kim
    • 1
  • Jin-Woo Jeon
    • 2
  • Ji-Young Son
    • 2
  • Min-Kyu Park
    • 2
  • Chul-Su Kim
    • 3
  • Hwang-Ju Jeon
    • 1
  • Tae-Hoon Nam
    • 1
  • Kyeongsoon Kim
    • 4
  • Byung-Jun Park
    • 5
  • Sung-Deuk Choi
    • 2
    • 3
  • Sung-Eun Lee
    • 1
  1. 1.School of Applied BiosciencesKyungpook National UniversityDaeguRepublic of Korea
  2. 2.School of Urban and Environmental EngineeringUlsan National Institute of Science and TechnologyUlsanRepublic of Korea
  3. 3.UNIST Environmental Analysis CenterUlsan National Institute of Science and TechnologyUlsanRepublic of Korea
  4. 4.Department of Pharmaceutical EngineeringInje UniversityGimhaeRepublic of Korea
  5. 5.Chemical Safety DivisionNational Academy of Agricultural Science, Rural Development AdministrationJeonjuRepublic of Korea

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