Distribution patterns of polychlorinated dibenzo-p ...

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Dec 7, 2011 - in all soil samples, the selected dioxin sources include. PCP (Bao et al. 1995), PCP-Na (Bao et al. 1995), joss paper incinerator (Hu et al. 2009) ...
Environ Monit Assess (2012) 184:7083–7092 DOI 10.1007/s10661-011-2481-0

Distribution patterns of polychlorinated dibenzo-p-dioxins and polychlorinated dibenzofurans in sediments of the Xiangjiang River, China Zhiliang Chen & Bing Yang & Alessio Mengoni & Jiahua Dong & Xiaochun Peng

Received: 8 July 2011 / Accepted: 24 November 2011 / Published online: 7 December 2011 # Springer Science+Business Media B.V. 2011

Abstract We investigated the occurrence and distribution patterns of 2,3,7,8-substituted polychlorinated dibenzo-p-dioxins and dibenzofurans (PCDD/Fs) in six sediment samples from the Xiangjiang River, Hunan Province, People’s Republic of China. Total concentrations of PCDD/Fs ranged from 876 to 497,759 (mean 160,766) ng/kg dw, the highest of which exceeded that have ever been reported for sediment samples. World Health Organization total toxicity equivalent (WHO-TEQ) concentrations in three out of six samples were significantly higher than the guidance level (21.5 ng WHO-TEQ/kg dw) suggested by Canadian Sediment Quality Guideline. A predominance of octachlorodibenzo-p-dioxin (OCDD) was observed with an average contribution of 90.8% to Z. Chen : B. Yang : J. Dong : X. Peng (*) Ministry of Environmental Protection, South China Institute of Environmental Sciences, Guangzhou 510655, People’s Republic of China e-mail: [email protected] B. Yang e-mail: [email protected] A. Mengoni Department of Evolutionary Biology, University of Firenze, Via Romana 17, 50125 Florence, Italy B. Yang School of Life Sciences and State Key Laboratory of Biocontrol, Sun Yat-sen University, Guangzhou 510275, People’s Republic of China

the total PCDD/F concentrations, while 1,2,3,4,6,7,8heptachlorodibenzo-p-dioxin (HpCDD) was the major contributor to the PCDD/F WHO-TEQ concentrations in most of the sites. Such high levels of OCDD and HpCDD may be attributed to the presence of PCP/ PCP-Na pollution, although MB-WW, agricultural straw open burning, and boilers–hazardous wastes were also the potential sources of PCDD/Fs. This is the first report for the concentrations and congener profiles of PCDD/Fs in sediment samples from the Xiangtan, Zhuzhou, and Changsha sections of the Xiangjiang River, providing scientific evidence for establishing priorities to reduce ecological risks posed by PCDD/Fs in the rapidly developing areas of Hunan Province and elsewhere. Keywords OCDD . PCDD/F . Xiangjiang River . Sediment . WHO-TEQ

Introduction Some of the chlorinated aromatic compounds are important endocrine-disrupting contaminants, such as polychlorinated dibenzo-p-dioxins (PCDDs) and dibenzofurans (PCDFs), which belong to “dioxins” (PCDD/Fs, USEPA 1993). PCDD/Fs have received much attention due to their wide origins and their environmental persistence and toxicity (Bursian et al. 2006; Hilscherova et al. 2003). It is well-known that they ubiquitously exist as by-products in incomplete

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combustion processes of mining, rubbish incineration, and paper making (Sundqvist et al. 2006). Meanwhile, they are found as impurities in pesticides such as DDTs (Isosaari et al. 2000), herbicides such as pentachlorophenol (PCP) (Weber et al. 2008), and defoliants such as 2,4-D (Holt et al. 2008). On the other hand, PCDD/Fs exist as complex mixtures in the environment, with up to 210 congeners. There are 17 2,3,7,8-substituted congeners which are the most extensively studied PCDD/ Fs because of their high toxicity for many animals (Fiedler 2007; Giesy et al. 2001). Among the congeners, 2,3,7,8-TCDD is the most poisonous, which has been classified as a group 1 carcinogen by World Health Organization (WHO)’s International Agency for Research on Cancer since 1997 (Seike et al. 2007; WHO 2007). For facilitating the comparison of the overall toxicity of PCDD/Fs among different sites, it is generally suggested to use the values for total toxicity equivalent (TEQ) based on International Toxic Equivalency Factors (I-TEFs) or the WHO-TEFs (Van den Berg et al. 2006). In recent decades, the occurrence and sources of PCDDs and PCDFs have been investigated in many countries (Choi et al. 2008; Jou et al. 2007) and in various environment sinks, such as water, atmosphere, soil, and sediment (Creaser et al. 1989; Weber et al. 2008). It is well-known that sediments can preserve the historical record of pollution (Liaghati et al. 2003; Moon et al. 2009; Yamashita et al. 2000), making it possible to study the distribution and inputs of PCDD/ Fs over long periods of time (Sanchez-Cabeza and Druffel 2009). In China, the surveys for the PCDD/ Fs levels in sediments were carried out in the Yangtze River Delta (Wen et al. 2008), Pearl River Delta (Zheng et al. 2001), Taihu Lake (Zhang and Jiang 2005), Haihe River (Liu et al. 2007), Daliao River, and Bohai Bay (Zhang et al. 2008). However, such information in other areas is very limited. The Xiangjiang River, an important tributary of the Yangtze River, is a major river in Hunan Province of southern China. In the catchment of the river, mining and metallurgical industries have been developing rapidly, such as Zhuzhou Metallurgical Group Corporation, Shuikoushan Mining Bureau, and Xiangtan Steel Group (Zhang et al. 2009). Since 1980s, urban, agricultural, and industrial wastes have been often discharged into the river in an uncontrolled way. As a result, numerous studies have highlighted that the

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Xiangjiang River has been subjected to high levels of heavy metal pollution with arsenic, cadmium, and other metals (Chen et al. 2004; Wang et al. 2011; Zhang et al. 2009). Because mineral processing, smelting of non-ferrous, and other industries are also the main sources of dioxins, it is likely that dioxins may be present in the Xiangjiang River. This objective of this study was to perform a first assessment of 2,3,7,8-PCDD/Fs levels in sediments of the Xiangjiang River. The assessment was based on sediment samples collected from three sections of Changsha, Xiangtan, and Zhuzhou in the river. Profiles of the 17 PCDDs/Fs congeners in these samples were studied.

Materials and methods Sampling sites The Xiangjiang River catchment is characterized by a typical subtropical monsoon climate with an annual average temperature of 17°C and annual rainfall of 1,400 mm. The river flows from north to south along seven cities in Hunan Province: Yongzhou, Hengyang, Zhuzhou, Xiangtan, Loudi, Changsha, and Yueyang. It finally empties into the Dongting Lake. Changsha– Zhuzhou–Xiangtan (Chang-Zhu-Tan) urban agglomeration, located in the middle and lower reaches of the river, is a famous heavy industrial base in China. Because of improper land use and local protectionism in this area, many efforts devoted to restore and protect the environment of the Xiangjiang River have proved to be ineffective (Chen et al. 2004).

Sampling A total of six sediment samples (two samples per section) were collected from Changsha (CS), Xiangtan (XT), and Zhuzhou (ZZ) sections of the Xiangjiang River in 2008 (Table 1; Fig. 1). At each site, three subsamples were collected using a grab sampler from a 0–5-cm depth, mixed homogeneously to one sample, and then deposited into a pre-cleaned amber glass bottle with a polytetrafluoroethylene seal. Sediment samples were freeze-dried and passed through a 2-mm sieve in the laboratory and then preserved at 4°C or less for further analysis.

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Table 1 Site description of sediment samples from the Xiangjiang River Sample

Location

Latitude (N)

Longitude (E)

TOC (%)

ZZ1

Zhuzhou bridge, Zhuzhou section

27°48.024′

113°08.433′

1.81

ZZ2

Jianning bridge, Zhuzhou section

27°51.154′

113°04.170′

0.63

XT1

Shuangma industrial Park, Xiangtan section

27°49.122′

112°59.772′

2.38

XT2

Shaoshan, Xiangtan section

27°57.086′

113°00.313′

2.01

CS1

Monkey stone bridge, Changsha section

28°08.721′

112°56.905′

1.41

CS2

Moon island bridge, Changsha section

28°17.931′

112°56.402′

0.55

Analytical methods Concentrations of 17 2,3,7,8-substituted PCDD/F congeners were determined according to the US EPA method 1613 (USEPA 1993). Briefly, a weight of 20 g of homogenized sediment was extracted with toluene using accelerated solvent extraction (DIONEX ASE3000) for 16 min. The extracts were purified by chromatography glass columns containing multilayer silica gel (activated, acidic and basic) alumina and florisil. The purified extracts were concentrated with rotary evaporators (STUART RE300) and then analyzed using a gas chromatographic (GC) system (Agilent HP6890) coupled to a mass spectrometer (Waters zq4000). The

GC was equipped with a DB-5 ms capillary column, 0.25 mm film thickness, and 60 m length (Agilent). The oven temperature was programmed as follows: initial temperature of 140°C for 2 min, increased from 140°C to 220°C at 8°C/min, from 220°C to 260°C at 1.4°C/min, and from 260°C to 310°C at 4°C/min for 4 min. Injector and transfer line/ion source temperatures were maintained at 280°C. The mass spectrometer was operated in the electron impact mode at 35 eV, and the ion current was 600 mA. The PCDDs/F congeners were monitored by selective ion monitoring at a resolution R03,000. The total organic carbon (TOC; in percent) content was determined with a TOC analyzer (TOC-VWS, Shimadzu Corporation, Japan). For quality control, a laboratory blank, an ongoing precision and recovery, and a certified reference sample (DX-2, Wellington Labs) were used. Predefined amounts of 13C-labeled PCDDs and PCDFs (Wellington Labs, Guelph, ON, Canada) were added prior to the extraction as internal standards. The calculated concentrations were reported as less than the limit of detection if the observed isotope ratio was over 20% of the theoretical ratio or the peak area was not greater than the specified threshold (three times the standard deviation of the noise). The recovery rates of the standards used for all the compounds varied from 75% to 120%, which are acceptable according to the EPA 1613 method. The final chemical concentrations were presented on a dry weight basis. Statistical analyses

Fig. 1 Sampling locations along the Xiangjiang River

Statistical analyses were carried out using the SPSS v13.0 statistical package. Principal component analysis (PCA) was performed to simplify large data sets, and then a hierarchical cluster analysis (HCA) was adopted using squared Euclidean distance with Ward’s clustering method to find out the grouping of PCDD/F

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profiles among the sites. PCA was employed to compare the 17 2378-substituted congener profiles of soils samples in Table 1 with suspected dioxin sources in the literature. Paralleling the results that octachlorodibenzop-dioxin (OCDD) was the absolutely dominant congener in all soil samples, the selected dioxin sources include PCP (Bao et al. 1995), PCP-Na (Bao et al. 1995), joss paper incinerator (Hu et al. 2009), steel plant dust (Aries et al. 2004), agricultural straw open burning (Shih et al. 2008), ferrous metal smelting (Zhu et al. 2008), wastewater from polyvinylchloride production (Carroll et al. 1998), boilers–hazardous wastes, refuse derived fuel, utility and industrial boilers, diesel fuel vehicles, unleaded gas-fueled vehicles, black liquid recovery boilers, MB-WW, and wastewater sludge combustion (US EPA 2001). Dioxin emissions from aluminum smelters and copper refinery (US EPA 2001) are also involved, since either large or small mineral processing enterprises are widely constructed in the Chang-Zhu-Tan (Wang et al. 2004). The data normalizing was performed according to

Zhu et al. (2008). Congener concentrations below the detection limit were assigned values of half the limit when processing normalization. TEQ values were calculated using the WHO-TEFs (Van den Berg et al. 2006).

Results and discussion PCDD/F concentrations and profiles Concentrations of 17 2,3,7,8-substituted PCDD/Fs in surface sediments from CS, XT, and ZZ sections of the Xiangjiang River varied from 876 to 498,000 ng/kg (mean 161,000 ng/kg, n06) (Table 2). In five out of the six sediment samples, the PCDD/F concentrations significantly exceeded the US guideline (1,000 ng/kg). Samples from XT section, located near Shuangma Industrial Park, contained the highest concentrations of PCDD/Fs (356,000 and 498,000 ng/kg). To the best of our knowledge, the concentration of 2,3,7,8-PCDD/Fs

Table 2 Summary statistics for concentrations of 2,3,7,8-substituted congeners of PCDDs and PCDFs in six sediment samples in the Xiangjiang River (nanograms per kilogram dry weight) IUPAC no.

ZZ1

ZZ2

XT1

XT2

CS1

CS2

2,3,7,8-TCDF

0.52

1.84

8.65

7.49

1.87

0.35

1,2,3,7,8-PeCDF

0.56

1.47

3.20

3.29

1.49

n.d.

2,3,4,7,8-PeCDF

0.91

2.15

10.1

5.71

1.45

0.11

1,2,3,4,7,8-HxCDF

1.57

4.90

34.3

31.4

10.0

0.63

1,2,3,6,7,8-HxCDF

1.66

4.88

15.0

14.6

7.21

0.40

2,3,4,6,7,8-HxCDF

1.64

4.13

51.3

32.1

18.3

0.75

1,2,3,7,8,9-HxCDF

0.37

1.13

16.6

9.42

3.88

0.19

1,2,3,4,6,7,8-HpCDF

8.85

30.4

1,274

1,271

318

15.3

1,2,3,4,7,8,9-HpCDF

1.04

4.53

144

121

36.7

1.53

OCDF

13.3

42.8

5,358

4,133

902

50.3

∑2378-PCDFs

30.5

98.2

6,916

5,629

1,301

69.6

2,3,7,8-TCDD

0.04

0.12

9.41

n.d.

n.d.

n.d.

1,2,3,7,8-PeCDD

0.29

0.57

49.6

7.46

4.90

0.22

1,2,3,4,7,8-HxCDD

0.35

1.01

159

20.3

21.3

0.96

1,2,3,6,7,8-HxCDD

0.95

2.22

845

495

195

9.33

1,2,3,7,8,9-HxCDD

1.13

2.72

333

66.1

52.5

1.92

1,2,3,4,6,7,8-HpCDD

21.2

78.1

37,400

31,200

8,822

612

OCDD

822

3,212

452,000

318,000

91,300

4,314

∑2378-PCDDs

846

3,297

491,000

350,000

100,000

4,938

∑2378-PCDD/Fs

876

3,395

498,000

356,000

102,000

5,008

WHO-TEQ∑PCDD/Fs

2.01

5.80

737

502

156

9.34

n.d. not detected

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1 0.1 0.01

CD

Pe

78

12

3

12

F

8 34 -Pe C 12 78-H DF 36 x C 7 23 8- DF 46 Hx 78 CD 12 -H F 3 x 12 789 CD 34 -H F 6 7 12 8 xCD 34 -H F 78 pC 9- D H F pC D F O 23 C 7 D 12 8-T F 3 C 12 78- DD 34 Pe C 12 78-H DD 36 x C 12 78-H DD 3 12 789 xCD 34 -H D 67 xC 8- D H D pC D O D CD D

F

1E-3 CD

23 7 12 8-T 37 C D 23 8-P F 47 eC 12 8-P DF 34 eC 12 78-H DF 36 x C 23 78-H DF 46 x C 12 78-H DF 3 x 12 789 CD 34 -H F 12 678 xCD 34 -H F 78 pC 9- D H F pC D F 23 OC 7 D 12 8-T F 37 C 12 8-P DD 34 eC 12 78-H DD 36 x C 12 78-H DD 37 x 12 89 CD 34 -H D 67 xC 8- D H D pC O DD CD D

10 1 0.1 0.01 1E-3

10

47

90

B

-T

Composition (%)

95

100

23

A

78

100

sediments from the Tittabawassee River (range 0.06 to 3.8; mean 0.87) (Hilscherova et al. 2003) and the Saginaw River (range 0.04 to 2.5; mean 0.57) (Kannan et al. 2008). Obviously, the ratios varied depending on the location (Kannan et al. 2008). Profiles of PCDD/F congeners in sediments from the Xiangjiang River are shown in Table 2 and Fig. 2a. The concentrations for the individual congeners ranged from below the detection limit (n.d.) to 452,000 ng/kg (Table 2). Among the PCDFs, OCDF and 1,2,3,4,6,7,8-HpCDF were the most abundant congeners, accounting for 72.9% to 96.0% (mean 87.9%) of the total PCDF concentrations but only 1.20% to 2.53% (mean 1.67%) of the total PCDD/F concentrations in sediment (Fig. 1a).The most abundant congener was OCDD with an average proportion of 90.8% (range 86.1% to 94.6%) in the total PCDD/Fs concentrations, followed by 1,2,3,4,6,7,8-heptachlorodibenzo-p-dioxin (HpCDD) of 7.0% on average (range 2.3% to 12.2%) (Fig. 1a). Extremely high levels of OCDD were also detected in sediments from other sites, such as Hong Kong (Terauchi et al. 2009) and Queensland (Gaus et al. 2001). As for the PCDD/F profiles, similar results were comparable to those reported for marine surface sediments from Hong Kong (Terauchi et al. 2009) and for floodplain soils and sediments from the Shiawassee River (Kannan et al. 2008). The high concentrations of PCDDs in comparison with those of PCDFs and the elevated proportions of OCDD and HpCDD in sediments from the Xiangjiang River suggested a major PCDD source in this watershed. Previous studies have identified that the occurrences of

23

(498,000 ng/kg) found in this study was the highest value that have ever been reported for sediment samples, followed by the value of 193,000 ng/kg from the Baltic Sea (Salo et al. 2008). The mean concentration of PCDD/Fs (161,000 ng/kg) in surface sediments in this study was 1 to 3 orders of magnitude higher than those reported in the Suzhou creek (723.4 ng/kg, Li et al. 2007), Saginaw River (4,830 ng/kg, Kannan et al. 2008), Lake Superior (5 to 18,000 ng/kg, Shen et al. 2009), Masan Bay (102 to 6,493 ng/kg, Im et al. 2002), and Lake Huron (3 to 6,100 ng/kg, Shen et al. 2009). Many studies have shown that 2,3,7,8-PCDD/Fs concentrations range from 1,000 to >70,000 pg/g dw in areas considered as highly impacted by human activities (Canedo-López et al. 2010). The results in this study suggest that the elevated concentrations of PCDD/Fs in the sediment samples are typically associated with anthropogenic activities in the catchment. As mentioned above, the enormous existence of mining and metallurgical industries along the Xiangjiang River might be responsible for not only the high concentrations of heavy metals but also those of PCDD/Fs. As shown in Fig. 2a, concentrations of PCDDs accounted for 92% to 98% of the total PCDD/F concentrations, which were obviously higher than those of PCDFs (2% to 8%) in all the sediment samples. The concentration ratios of PCDDs to PCDFs (range 28 to 77; mean 57) in sediments from the Xiangjiang River were ten times of those found in sediments from the Shiawassee River (range 1.2 to 24; mean 5.7) (Kannan et al. 2008) and more than 50 times of those in

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Fig. 2 Concentrations of 2378-PCDD/F congener profile (a) and WHO-TEQ concentrations (b) in surface sediment from the Xiangjiang River

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demonstrating the high variability. Mean TEQ concentrations in sediments from the XT section (619.5 ng/kg) were 7.5-fold and 158-fold higher than those from the ZZ section (82.7 ng/kg) and CS section (3.91 ng/kg), respectively. TEQ concentrations for XT1 (737 ng WHO-TEQ/kg) and XT2 (502 ng WHO-TEQ/kg) were actually comparable to those reported in electronic component waste samples from Guiyu (489 ng WHOTEQ/kg, Leung et al. 2007) and higher than those reported in Saginaw River (3–266 ng WHO-TEQ/kg, Kannan et al. 2008) and Masan Bay (1 to 76 ng WHOTEQ/kg, Im et al. 2002). TEQ concentrations for three out of six sediment samples, XT1, XT2, and CS1, were significantly (P