Occurrence and levels of polybrominated diphenyl ethers in surface sediments from the Yellow River Estuary, China

Environmental Pollution 212 (2016) 147e154

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Occurrence and levels of polybrominated diphenyl ethers in surface sediments from the Yellow River Estuary, China* Zijiao Yuan a, b, c, d, Guijian Liu a, b, c, *, Michael Hon Wah Lam c, d, Houqi Liu a, Chunnian Da a a

CAS Key Laboratory of Crust-Mantle Materials and the Environment, School of Earth and Space Sciences, University of Science and Technology of China, Hefei, Anhui 230026, China State Key Laboratory of Loess and Quaternary Geology, Institute of Earth Environment, The Chinese Academy of Sciences, Xi'an, Shaanxi 710075, China c University of Science and Technology of ChinaeCity University of Hong Kong Joint Advanced Research Centre, Suzhou, Jiangsu 215123, China d Department of Biology & Chemistry, City University of Hong Kong, Tat Chee Avenue, Hong Kong SAR, China b

a r t i c l e i n f o

a b s t r a c t

Article history: Received 18 November 2015 Received in revised form 18 January 2016 Accepted 20 January 2016 Available online xxx

A total of 21 surface sediments collected from the Yellow River Estuary, China were analyzed for 40 kinds of polybrominated diphenyl ethers (PBDEs) using gas chromatography-mass spectrometry (GCeMS). Their levels, spatial distribution, congener profiles and possible sources were investigated. Only ten congeners were detected in the sediments. The total concentrations of the lower brominated BDEs P ( PBDEslow, PBDEs excluding BDE 209) and BDE 209 ranged from 0.482 ng/g to 1.07 ng/g and 1.16 e5.40 ng/g, with an average value of 0.690 and 2.79 ng/g, respectively, which were both at the low end of the global contamination level. The congener profiles were dominated by BDE 209, with the average value accounting for 79.2% of the total PBDEs in the sediment samples. Among the nine lower brominated BDE congeners, BDE 47, 99 and 183 had high abundances. Although the commercial Penta/OctaBDE products have been banned in most countries, the residual commercial Penta/Octa/Deca-BDE products and the debromination of highly brominated BDE compounds such as BDE 209 were still found to be the possible sources for the trace level of PBDEs in the present study area. In spite of the gradual removal of the commercial PBDEs in the world, the present research results further suggested that scientific attention should not be reduced on the issue of environmental contamination caused by these outdated chemical compounds. © 2016 Elsevier Ltd. All rights reserved.

Keywords: Yellow river Polybrominated diphenyl ethers Surface sediments Congener profiles Possible sources

1. Introduction Polybrominated diphenyl ethers (PBDEs) are a group of widely used brominated flame retardants (BFRs) in the world since 1960s and the production of PBDEs has increased quickly, leading to the cumulative production of over 2 million tons (Rayne et al., 2003; Shaw and Kannan, 2009; Wiseman et al., 2011). Pentabromodiphenyl ether (Penta-BDE), octabromodiphenyl ether (Octa-BDE) and decabromodiphenyl ether (Deca-BDE) were the three major commercial formulations of PBDEs (La Guardia et al., 2006). However, owing to their persistence, potential for endocrine disruption

*

This paper has been recommended for acceptance by Jay Gan. * Corresponding author. CAS Key Laboratory of Crust-Mantle Materials and the Environment, School of Earth and Space Sciences, University of Science and Technology of China, Hefei, Anhui 230026, China. E-mail address: [email protected] (G. Liu). http://dx.doi.org/10.1016/j.envpol.2016.01.058 0269-7491/© 2016 Elsevier Ltd. All rights reserved.

and bioaccumulation, and long-range transport ability, PBDEs were of great environmental concern in the past few years and the production of the Penta- and Octa-PBDE technical mixtures were banned in the European Union and North America in 2004, resulting in the gradual removal of PBDEs (Hale et al., 2006; Moon et al., 2007; Su et al., 2014). Nevertheless, the use of Deca-BDE is not subject to any regulatory restrictions in most countries and the Deca-BDE commercial mixture is still the dominant BFRs used in China (Mai et al., 2005; Ni et al., 2013; Zou et al., 2007). BDE 209 is the main component of Deca-BDE commercial mixture and it can degrade or metabolize into lower brominated congeners, which are more bioavailable, persist and toxic than BDE 209 (La Guardia et al., € derstro €m et al., 2004; Van den Steen 2007; Lagalante et al., 2011; So et al., 2007). In recent years, despite the gradual removal of commercial PBDEs, they have been widely detected in air (Li et al., 2015), water (Yang et al., 2015), sediments (Nouira et al., 2013), soil (Parolini et al., 2013), plant (Wang et al., 2011), marine mammal

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(Zhu et al., 2014a), birds (Erratico et al., 2015), and human tissues l et al., 2014). (Bramwell et al., 2014; Fromme et al., 2015; Kro Therefore, it is of great significance to continuously study the current contamination level of PBDEs in various environmental media, thus obtaining the action effect of PBDE restrictions and developing effective counter measures to reduce their adverse effects on the environment. The Yellow River, with a main stream 5464 km long and drainage area of 795 thousand km2, is the second largest river in China and one of the largest rivers in the world (Xu et al., 2007). It flows across nine Provinces in North China and ultimately run into the Bohai Sea through the present Yellow River Estuary in the city of Dongying in Shandong Province. Hydrophobic organic contaminants such as PBDEs are prone to be trapped in estuarine sediment through riverine inputs and atmospheric deposition (Zhao et al., 2011). Considering the rapid economic development in the adjacent Laizhou Bay area in the south of the estuary, where the largest BFR-manufacturing center in China located (Pan et al., 2011; Zhu et al., 2014b), the contamination caused by flame retardants such as PBDEs was expected to be serious in the Yellow River Estuary. The objectives of the present research work were to investigate the contamination level, spatial distribution, congener profile and possible potential sources of PBDEs in surface sediments collected from the Yellow River Estuary, further helping environmental researchers understand the global tendency of PBDE pollution under the situation of global restriction to this kind of contaminants, thus developing effective counter measures to control their adverse effects. To the best of our knowledge, this is the first study concentrating specifically on PBDEs in the Yellow River Estuary, China, which is a typical estuary area in the world. 2. Materials and methods 2.1. Study area and sample collection A total of 21 surface sediments were collected using a stainless steel grab from the Yellow River Estuary in August, 2013 (Fig. 1). The investigated area covers approximately 100 km of shoreline from the estuary mouth and holds the sampling locations both in and out of the Yellow River Delta Natural Reserve (YRDNR). The Yellow River Delta has been reported as a typical petrochemical area (Xie et al., 2012): Shengli Oilfield, the second largest oilfield in China, is located here and many branch oilfields of Shengli are spread over the study area due to the abundant oil and gas resources in this region. In addition, Laizhou Bay area, which holds the famous

chemical industrial base Weifang Binhai Economic Development Zone and the largest BFR-manufacturing center in China, is located in the south of the estuary area (Pan et al., 2011; Zhu et al., 2014b). The detailed sampling sites in this study were similar to our previously published paper (Yuan et al., 2015). After collection, all the samples were individually wrapped in clean aluminum foil, which were pre-combusted under 450
C to remove organic influence, and were transported to the laboratory immediately. Sediment samples were kept in a freezer at 20
C until further analysis. 2.2. Reagents and materials PBDE standard solutions BDE-AAP-A-15X, which contains 39 PBDE congeners including 2-BDE (BDE 1), 3-BDE (BDE 2), 4-BDE (BDE 3), 2,6-di-BDE (BDE 10), 2,4-di-BDE (BDE 7), 3,30 -di-BDE (BDE 11), 2,40 -di-BDE (BDE 8), 3,40 -di-BDE (BDE 13), 3,4-di-BDE (BDE 12), 4,40 -di-BDE (BDE 15), 2,4,6-tri-BDE (BDE 30), 2,40 ,6-triBDE (BDE 32), 2,20 ,4-tri-BDE (BDE 17), 2,30 ,4-tri-BDE (BDE 25), 2,4,40 -tri-BDE (BDE 28), 20 3,4-tri-BDE (BDE 33), 330 4-tri-BDE (BDE 35), 3,4,40 -tri-BDE (BDE 37), 2,4,40 6-tetra-BDE (BDE 75), 220 450 tetra-BDE (BDE 49), 2,30 ,40 ,6-tetra-BDE (BDE 71), 2,20 4,40 -tetra-BDE (BDE 47), 2,30 ,4,40 -tetra-BDE (BDE 66), 3,30 4,40 -tetra-BDE (BDE 77), 2,20 4,40 ,6-penta-BDE (BDE 100), 2,30 4,40 6-penta-BDE (BDE119), 2,20 4,40 ,5-penta-BDE (BDE99), 2,30 4,40 5-penta-BDE (BDE 118), 2,3,4,5,6-penta-BDE (BDE 116), 2,20 ,3,4,40 -penta-BDE (BDE 85), 3,30 4,40 5-penta-BDE (BDE126), 2,20 ,4,40 ,6,60 -hexa-BDE (BDE155), 2,20 4,40 5,60 -hexa-BDE (BDE 154), 2,20 4,40 5,50 -hexa-BDE (BDE 153), 2,20 3,4,40 50 -hexa-BDE (BDE 138), 2,3,4,40 ,5,6-hexa-BDE (BDE 166), 2,20 ,3,4,40 ,50 6-hepta-BDE (BDE 183), 2,20 3, 4,40 ,5,6-hepta-BDE (BDE 181), 2,3,30 ,4,40 ,5,6-hepta-BDE (BDE 190), and individual standard of 2,20 ,3,30 ,4,40 ,5,50 ,6,60 -deca-BDE (BDE 209), were purchased from AccuStandard, Inc. (New Haven, CT, USA). PBDE surrogate standards MBDE eMXA (containing 13C12-BDE 47, 13C12-BDE 99 and 13C12-BDE 153) were purchased from Wellington Laboratories (Guelph, Ontario, Canada). Silica gel (230e400 Mesh) was purchased from Riedel de Haen (Seelze, Lower Saxony, Germany). The internal standard m-terphenyl (99%) was purchased from J&K Chemical, China. Activated neutral alumina (75e300 Mesh) was purchased from International Laboratory, USA. Anhydrous sodium sulfate and copper were purchased from Sinopharm Chemical Reagent Co.(Shanghai, China). Before use, silica gel and anhydrous sodium sulfate were activated for more than 6 h at 500
C. Acidified silica gel was prepared by adding 27 mL concentrated sulfuric acid dropwise to 50 g activated silica gel with stirring (Covaci et al., 2002). Activated copper powder was prepared by mixing copper

Fig. 1. Sampling locations in the Yellow River Estuary, China (Yuan et al., 2015).

Z. Yuan et al. / Environmental Pollution 212 (2016) 147e154

149

with 1 mol/L hydrochloric acid and then rinsed with water, methanol and dichloromethane. All the organic solvents (dichloromethane, hexane, methanol and acetone) used for sample preparation were of analytical grade and purchased from RCI Labscan Limited (Bangkok, Thailand). Water used in the present study was Milli-Q high-grade water (18 MU) which obtained through a Millipore water purification system (Billerica, MA, USA). Furthermore, all the glassware used was sequentially washed with acetone, water and baked at 500
C for 12 h to eliminate any organic contamination.

PBDE compounds were identified mainly by comparing the GC retention time and the selected ion with the authentic standards. The ions monitored for each compound were as follows: m/z 248, 250 (BDE 1, 2, 3), m/z 328, 168, 326 (BDE 10, 7, 11, 8, 13, 12, 15), m/z 246, 248, 406, 408 (BDE 30, 32, 17, 25, 28, 33, 35, 37), m/z 326, 486 (BDE 75, 49, 71, 47, 66, 77), m/z 404, 406, 564, 566 (BDE 100, 119, 99, 118, 116, 85, 126), m/z 484, 644 (BDE 155, 154, 153, 138, 166), m/z 562, 564, 722, 724 (BDE 183, 181, 190), m/z 799 (BDE 209), m/z 337.9, 497.8 (13C12-BDE 47), m/z 417.9, 575.8 (13C12-BDE 99), m/z 495.8, 655.7 (13C12-BDE 153) and m/z 230 (m-terphenyl).

2.3. Sample extraction and clean up

2.5. Quality assurance and quality control (QA/QC)

The extraction and clean up of PBDEs were carried out according to several previously published methods with some modifications (Chen et al., 2012a; Lei, 2014). Each sample was freeze-dried, ground and homogenized to a fine powder with a mortar and pestle, then sieved through a stainless steel sieve (<125 mm). Next, they were spiked with three 13C-labbeled PBDE surrogate standards and allowed to equilibrate for 12 h. The prepared sediment samples were mixed with 5 g activated copper powder and were extracted with dichloromethane: hexane (1:1, v:v) in a sonication extractor for 30 min and then in a hot water bath (70
C) for another 30 min. Three cycles were performed for each solvent system per sample and the three extraction fractions were cooled and combined for subsequent cleanup. The combined extracts were concentrated by vacuum rotary evaporator and solvent-exchanged with hexane, then further blown down to 100 mL under a gentle stream of nitrogen. The concentrated extract was directly applied to a multi-layer column chromatography, previously conditioned with 20 mL hexane. The column fitted with a Teflon stopcock was packed from the bottom with 1.2 g anhydrous sodium sulfate, 2.4 g activated neutral alumina, 2.4 g acidified silica gel and 1 g anhydrous sodium sulfate. The column was eluted with 6 mL hexane and 6 mL dichloromethane. The extract was evaporated to dryness under a gentle flow of nitrogen and reconstitute in 100 mL hexane with a known amount of m-terphenyl (Internal standard). The quantification of the lower brominated BDE congeners (MonoBDEs to HepaBDEs) was conducted through the internal standard calibration and BDE 209 was quantified with the external standard calibration method.

The linearity of the method was checked using calibration curves made from standard solutions at five concentration levels and the quantification was only conducted when good linearity of the standard calibration curve was obtained (r2 > 0.99). The instrumental detection limit (IDL) for BDE 209 and the method detection limit (MDL) for the 39 lower brominated PBDEs were reported as the limit of detection (LOD) in the present research work. The IDL of BDE 209 was defined as the concentration that resulted in a signal-to-noise ratio of 3. To determine the MDL of the 39 PBDEs, a series of N samples were selected as the QA/QC samples before the onset of the extraction of the field samples and a known amount of the 39 PBDE standards was spiked into the N sample matrix. These spiked “samples” were analyzed and the standard deviation of the results (s) was calculated. The MDL for the 39 PBDE compounds can be calculated from the equation “MDL ¼ t  s”, where t is the compensation factor from the Student-t table of (N-1) degree of freedom with a confident interval of 95%. In the present research work, N is equal to seven. The LOD varied from 0.001 to 0.053 ng/g for the 39 lower brominated PBDEs and 1 ng/g for BDE 209. Procedural blanks (solvent), spiked blanks (spiked into solvent) and sample duplicates were processed for each batch of 14 sediment samples to assess possible interferences of other contaminants from solvents and glassware during sample processing. Furthermore, three 13C-labbed PBDE surrogate standards were added before extraction to quantify procedural recoveries. Solvents injected before and after the injection of standards showed negligible contamination or carryover. The relative standard deviations of the sample replicates were less than 15% and indicated good repeatability. The mean recoveries for surrogate PBDEs spiked in the field samples were 91.97 ± 12.1% for 13C12-BDE 47, 107.72 ± 13.59% for 13C12-BDE 99 and 103.22 ± 14.17% for 13C12-BDE 153. All the results were not corrected for recoveries and expressed on dry weight basis.

2.4. GCeMS analysis The instrumental methods and parameters chosen for the PBDEs in the present research work were modified based on some previous published research (Chen et al., 2012b; La Guardia et al., 2006; Lei, 2014). The analysis for the lower brominated BDE congeners (MonoBDEs to HepaBDEs) was conducted on an Aglient 5975C mass spectrometer detector (MSD) linked to a 7890 gas chromatography (GC) in selected ion mode (SIM), and the separation was accomplished with a DB-5MS capillary column (30 m  0.25 mm i.d.  0.1 mm film thickness). The oven program for the PBDE congeners was as follows: The initial temperature was 60
C and held for 2 min, then ramped to 200
C at 10
C/min and held for 2 min, before a final ramping to 300
C at 20
C/min and held for 10 min. The determination of BDE 209 was performed on Thermo Trace Ultra gas chromatography (GC) unit coupled to a Thermo DSQ II mass spectrometry (MS) unit in selective ion monitoring (SIM) mode using positive ion electron impact ionization (ionizing potential 70 eV), and separation was accomplished with a DB-5HT capillary column (15 m  0.25 mm i.d.  0.1 mm film thickness). The oven temperature started at 120
C, held for 1 min, then increased at 25
C/min to 330
C, held for 10 min. The individual

2.6. Statistical analysis Hierarchical cluster analysis (HCA), which can classify data according to their degree of similarity, and principal component analysis (PCA), which can reduce a set of original data into a small number of interpretable factors, were conducted on the data using SPSS 15.0 (Statistical Product and Service Solutions) for windows. Pearson correlation analysis among PBDE congeners was also performed by SPSS15.0. In order to meet the requirements of the HCA, the undetectable values were replaced with 1/2 LOD (Liu et al., 2009). Before conducting HCA, the KolmogoroveSmirnov test was carried out to verify whether the frequency distribution of the data was a normal distribution (p > 0.05). Moreover, when conducting HCA, all the data were Z-scaled (Mean ¼ 0 and standard deviation ¼ 1) to exclude influences of different scales. The method used was Ward's method and the distances were calculated using Euclidean distances (Jiang et al., 2011a; Motelay-Massei et al., 2004).

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3. Results and discussion 3.1. Levels and geographic distribution of PBDEs In the present study area, PBDEs were detected in all the 21 sediment samples, suggesting that these contaminants were widespread in the Yellow River Estuary, China. However, among the 40 PBDEs targeted in the present research work, only 10 PBDE congeners were found in the samples, they were BDE 10, BDE 35, BDE 37, BDE 47, BDE 99, BDE 85, BDE 154, BDE 153, BDE 183 and BDE P 209. The PBDEs low is defined as the sum of the detectable conP geners, excluding BDE 209. The PBDEs is defined as the sum of all the detectable congeners, including BDE 209. The concentrations of the detectable PBDE concentrations were summarized in Table 1. P The total concentrations of the PBDEs low and BDE 209 ranged from 0.482 ng/g to 1.07 ng/g and 1.16e5.40 ng/g, with an average value of 0.690 ng/g and 2.79 ng/g, respectively. For the lack of environmental health guidelines for PBDEs in sediments in China, the Federal Environmental Quality Guidelines (FEQGs) for PBDEs established by Environmental Canada (They were 44, 39, 0.4, 440 and 19 ng/g for the TriBDEs, TetraBDEs, PentaBDEs, HexaBDEs and DecaBDEs, respectively), below which there is little probability of adverse impacts on aquatic life, were used to evaluate the ecological risk of PBDEs in sediments to aquatic life in the Yellow River Estuary (Environment Canada, 2010; Marvin et al., 2013). Except BDE 99 in site 18, all the other PBDE congeners in the remaining sampling sites were below the FEQGs, indicating low risks of PBDEs in the study area. P The geographic distribution of concentrations of PBDEs in the Yellow River Estuary was illustrated in Fig. 2. In order to provide a much more indicative view of the PBDE distribution, the 21 surface sediments were divided into three parts along the reach of the estuary (Fig. 1): Section 1 includes 5 sampling sites (Site 1 to site 5), which were all relatively in the upper reach of the estuary and located out of the Yellow River Delta Natural Reserve; The site 6 to site 14 were included in Section 2, which were relatively in the middle reach of the estuary and in the natural reserve, where anthropogenic activities were scarce; The Section 3 contained the

Table 1 A summary of PBDE concentrations in sediments collected from the Yellow River Estuary, China (ng/g dry weight). BDE congeners

BDE concentrations Min

BDE 10 BDE 35 BDE 37 BDE 47 BDE 99 BDE 85 BDE 154 BDE 153 BDE 183 BDE209 MonoBDEs DiBDEs TriBDEs TetraBDEs PentaBDEs HexaBDEs HeptaBDEs DecaBDE P PBDEsbLow P PBDEsc

a

nd nd nd nd nd nd nd nd 0.00128 1.16 nd nd nd nd nd nd 0.00128 1.16 0.482 1.97

Max

Average

0.0732 0.0914 0.0966 0.585 0.441 0.147 0.0559 0.118 0.247 5.40 nd 0.0732 0.0966 0.585 0.441 0.166 0.247 5.40 1.07 6.46

0.0233 0.0112 0.0209 0.228 0.140 0.0181 0.0161 0.0649 0.167 2.79 nd 0.0233 0.0320 0.228 0.158 0.0811 0.167 2.79 0.690 3.48

P a: Not detected; b: PBDEslow refers to the total concentrations of all the detectable P PBDEs excluding BDE 209; c: PBDEs refers to the total concentrations of all the detectable PBDEs including BDE 209.

remaining sampling sites (Site 15 to 21), which were close to the Bohai Sea and located at the mouth of the estuary. The mean P concentrations of PBDEs in Section 1 (3.33 ng/g) and Section 3 (4.32 ng/g) were higher than that of the Section 2 (2.92 ng/g). The Section 1 is exposed to the city of Dongying, which is an important industrial base in Shandong Province, China and the phenomenon of environmental contamination has arisen along with the rapid development of the city, thus there is a tremendous possibility for PBDEs loading into Section 1 from the city through the discharge of the municipal and industrial wastewater effluents, urban surface runoff and the direct deposition from the atmosphere, which may lead to the relatively high levels of PBDEs (Kong et al., 2011, 2012a, 2012b). The highest concentrations of the Section 3 may be caused by the following factors: as the mouth of the Yellow River Estuary, the Section 3 is the interaction zone of freshwater and seawater and it may be influenced by both of them. In addition to the riverine inputs and the atmospheric deposition, PBDEs may be further accumulated in the estuarine sediments by the intrusion of sea waters from Bohai, which have been reported for PBDE contamination in the past few years (Jin et al., 2008; Pan et al., 2010, 2011). 3.2. Comparison of PBDE concentrations in surface sediments from other studies In order to evaluate the contamination levels of PBDEs, a comparison was conducted on the PBDE concentrations in surface sediments in the present study area with other locations in China and other countries in Table 2. Compared with other regions in China, the concentrations of P PBDEs low in the Yellow River Estuary were similar to those detected in the marine sediments in the adjacent Bohai Sea (Pan et al., 2010) and Laizhou Bay (Pan et al., 2011), Yangtze River Delta (Chen et al., 2006), Chaohu Lake (He et al., 2013), Baiyangdian Lake (Hu et al., 2010) and southwest Taiwan (Jiang et al., 2011b), but far below the concentration detected in the riverine sediments in the adjacent Laizhou Bay (Pan et al., 2011), Taihu Lake (Zhou et al., 2012), Shanghai (Wang et al., 2015), East China Sea (Li et al., 2012), the Pearl River Delta and the South China Sea (Mai et al., 2005). Compared with other locations in the world, the concentrations of P PBDEs low were higher than that of the Monastir Bay in Tunisia of the Central Mediterranean (Nouira et al., 2013), similar to the Shiawassee River, Saginaw River and Saginaw Bay in the USA (Yun et al., 2008), Tokyo Bay in Japan (Minh et al., 2007), Svabard, Northweigian Arctic (Jiao et al., 2009), but lower than that of the Chenab River, Pakistan (Mahmood et al., 2015), Ebro River in Spain (Eljarrat et al., 2004), Coastal waters of Korea (Ramu et al., 2010) and Niagara River in North America (Samara et al., 2006). For BDE 209, it was higher than that of the Chaohu Lake, China (He et al., 2013), similar to those detected in Southwest Taiwan, China, the Shiawassee River and Saginaw Bay in USA (Jiang et al., 2011b; Yun et al., 2008), but lower than that of other locations listed in Table 2. Based on the comparison, it can be concluded that the PBDE contamination level in the Yellow River Estuary was very low. 3.3. PBDE congener profiles and possible sources BDE 209, which is the main component of Deca-BDE commercial mixture, predominated in the sediments collected from the Yellow River Estuary, China, with an average value accounting for 79.2% of the total PBDEs in the samples, which coincides with the fact that the BFR production in China is dominated by commercial Deca-BDE products (Mai et al., 2005). For the PBDEs excluding BDE 209, a distinct different composition pattern can be observed in different section of the Yellow River

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Fig. 2. Spatial distribution of PBDEs in surface sediments collected from the Yellow River Estuary, China.

Table 2 A comparison of PBDE concentrations in sediments from the Yellow River Estuary with other locations in the world (ng/g dry weight). Locations

Sample description

Number of the detectable PBDEsa

Concentration range P BDE209 PBDEslowb

Yellow River Estuary, China

Riverine sediments

10

1.16e5.40 (2.79)

This study

10

0.482e1.07 (0.690)c 0.04e94.7 (9.9)

0.4e7341(465)

Mai et al., 2005

References

Pearl River Delta and adjacent South China Riverine and Marine Sea Sediments Yangtze River Delta, China Riverine and Marine Sediments Shanghai, China Riverine sediments Chaohu Lake, China Lake sediments

13

nd-0.55 (0.15)

0.16e94.6 (13.4)

Chen et al., 2006

52 14

Lake sediments

26

Baiyangdian Lake, China Laizhou Bay, China Laizhou Bay, China Bohai sea,China East China Sea Southwest Taiwan, China Shiawassee River, USA Saginaw River, USA Saginaw Bay,USA Niagara River, North America Coastal waters of Korea Ebro River, Spain Tokyo Bay, Japan Chenab River, Pakistan

Lake sediments Riverine sediments Marine sediments Marine sediments Marine sediments Marine sediments Riverine sediments Riverine sediments Marine sediments Riverine sediments Marine sediments Riverine sediments Marine sediments Riverine sediments

8 8 8 8 8 14 10 10 10 9 14 8 e 8

0.05e5.03 (0.78) 0.01e53 (4.5) nd-0.66 (0.32) 0.22e0.9 (0.48) nd-8.0 (1.6) nd-1.82 0.03e3.57(0.56) 0.04e2.54(0.61) 0.01e0.92 (0.34) 0.72e148 0.05e32 0.3e34.1 0.051e3.6 0.35e88.1 (18.7)

nd-189 (13.2) 0.0042 e0.691(0.176) 9.68e143.51 (37.49) 4.35e19.3(10.4) 0.74e280 (54) 0.66e12 (5.1) 1.76e15.1(7) 0.3e44.6(6.4) nd-6.26 0.11e12.7 (2.28) 0.08e48.3 (4.76) <0.01e5.8 (1.98) e 0.4e98 2.1e39.9 0.89e85 -

Wang et al., 2015 He et al., 2013

Taihu Lake, China

0.231e119 (7.20) 0.237e1.373 (0.638) 0.39e34.44 (5.21)

Monastir Bay (Tunisia, Central Mediterranean) Svalbard, Norwegian Arctic

Marine sediments

4

nd-0.1

e

Hu et al., 2010 Pan et al., 2011 Pan et al., 2011 Pan et al., 2010 Li et al., 2012 Jiang et al., 2011b Yun et al., 2008 Yun et al., 2008 Yun et al., 2008 Samara et al., 2006 Ramu et al., 2010 Eljarrat et al., 2004 Minh et al., 2007 Mahmood et al., 2015 Nouira et al., 2013

0.024e0.97

e

Jiao et al., 2009

a b c

Lake and marine sediments

14

Zhou et al., 2012

The number of PBDEs that were found in the field samples. P PBDEs low refers to the total concentrations of all the detectable PBDEs excluding BDE 209. The average concentration is tabulated in parenthesis.

Estuary. The compositional pattern of the lower brominated PBDE congeners was illustrated in Fig. 3. Among the nine lower brominated PBDE congeners detected in the Yellow River Estuary sediments, BDE 183 was predominated in Section 1 and 2 of the estuary (Site 1 to Site 14), with the average value accounting for 37.2% of P PBDEslow. However, in Section 3, BDE 47 and 99 were the major congeners, with the average concentration accounting for 53.5% P and 34.8% of the PBDEslow, respectively. BDE 47, 99 and 183 have been reported as the major components of commercial Penta-BDE and Octa-BDE products (La Guardia et al., 2006), therefore, the dominance of the three BDE congeners may indicate the possible use of the commercial Penta-BDE and Octa-BDE products in addition to the Deca-BDE products in the study area.

To find out whether the commercial Penta-BDE and Octa-BDE products were indeed the potential sources of PBDEs in the sediments in the Yellow River Estuary in addition to the commercial Deca-BDE products, a hierarchical cluster analysis (HCA) was conducted on the compositional pattern of the major PBDE congeners in the commercial Penta-BDEs (Bromkal 70-5DE and DE-71) € din et al., 1998) and Octa-BDEs (Konstantinov et al., 2008; Sjo (Bromkal 79-8DE and DE-79) (La Guardia et al., 2006) and the 21 surface sediments collected from the Yellow River Estuary. The similarities between the sediment samples and the four commercial PBDE products were illustrated with dendrogram in Fig. 4. As can be observed in Fig. 4a, the two commercial Octa-BDE products and the 14 sediment sampling sites were distinguished into two

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Fig. 3. Compositional pattern of lower brominated PBDEs (Excluding BDE 209) in surface sediments collected from the Yellow River Estuary, China.

S20, S21, Bromkal 70-5DE and DE-71, indicating the impact from commercial Penta-BDE products on these sampling sites. To further identity the possible sources of PBDEs in the Yellow River Estuary, PCA was conducted on the ten PBDE congeners detected in the sediments collected from the Yellow River Estuary, China. Three principal components (PC1, PC2 and PC 3) were extracted, accounting for 78.4% of the total variances (Table 3). As can be observed in Table 3, PC 1 accounted for 37.3% of the total variance and was predominated by BDE 10, BDE 37, BDE 47, BDE 154, BDE 153 and BDE 183. Among them, BDE 47, BDE 153, BDE154 and BDE 183 have been identified as the indicator of commercial Penta- and Octa-BDE products (La Guardia et al., 2006). BDE 10 and BDE 37 were not detected in any of the commercial Penta-, Octa- or Deca-BDE products (Konstantinov et al., 2008; La € din et al., 1998), but significant correlaGuardia et al., 2006; Sjo tion was observed between BDE 209 and BDE 10 (p  0.05) and among BDE 37, BDE 154 (p  0.05), BDE 153 (p  0.01) and BDE 183 (p  0.01) in Table 4. In addition, significant relationship was observed among BDE 10, BDE 47, BDE 154, BDE 153 and BDE 183 (p  0.01), indicating a similar environmental behavior and common source of these PBDEs. Moreover, significant correlation was P also observed between BDE 209 and PBDEs low (p  0.01). Considering the degradation and metabolism of highly brominated BDE compounds such as BDE 209 (La Guardia et al., 2007; Lagalante € derstro €m et al., 2004; Van den Steen et al., 2007), BDE et al., 2011; So 10 and BDE 37 in the sediments may be originated from the debromination of highly brominated BDE compounds. Therefore,

Table 3 Rotated component loadings of the principal components for PBDE compositions in sediments from the Yellow River Estuary, China. Fig. 4. Hierarchical dendogram for the major PBDE congeners in the sediment samples and four commercial PBDE products (Bromkal 70-5DEa,DE-71b, Bromkal 79-8DEc and DE-79c) using Ward's method and Euclidean distances as measure interval. a: Data € din et al., 1998. b: Data cited in Konstantinov et al., 2008. c: Data cited in La cited in Sjo Guardia et al., 2006.

major groups. The first major group was composed of S1, S2, S3, S4, S5, S6, S7, S10, S11, S12, S13, S14, and DE-79 and the second major group was composed of S8, S9 and Bromkal 79-8DE, suggesting that the two commercial Octa-BDE products may have impacts on these sampling sites. In Fig. 4b, the two commercial Penta-BDE products and the seven sediment samples were divided into two major groups. The first major group was consisted of S15 and S16. No commercial Penta-BDE products were included in this group. However, the second major group was composed of S17, S18, S19,

Principal components (78.4%)

BDE10 BDE35 BDE37 BDE47 BDE99 BDE85 BDE154 BDE153 BDE183 BDE209

1(37.3%)

2(27.1%)

3(14.0%)

¡0.758 0.301 0.773 ¡0.573 0.280 0.276 0.817 0.826 0.759 0.239

0.527 0.113 0.048 0.643 0.735 ¡0.671 0.231 0.268 0.519 0.784

0.285 0.850 0.130 0.372 0.097 0.519 0.127 0.216 0.287 0.132

The bold values indicate the relatively high absolute values of a variable in each principal component (Each principal component had relatively high loadings on these variables). These variables are highly correlated with the possible source and can help to identify the source categories.

Z. Yuan et al. / Environmental Pollution 212 (2016) 147e154

153

Table 4 Pearson correlation coefficients between PBDE congeners.

BDE35 BDE37 BDE47 BDE99 BDE85 BDE154 BDE153 BDE183 BDE209 P PBDEslow P PBDEs a b

BDE10

BDE35

BDE37

BDE47

BDE99

BDE85

BDE154

BDE153

BDE183

BDE209

P PBDEslow

0.366 0.563(a) 0.861(a) 0.546(b) 0.310 0.712(a) 0.796(a) 0.994(a) 0.494(b) 0.336 0.489(b)

0.277 0.419 0.001 0.131 0.111 0.372 0.363 0.017 0.121 0.003

0.394 0.348 0.067 0.446(b) 0.594(a) 0.558(a) 0.052 0.044 0.053

0.444(b) 0.415 0.587(a) 0.722(a) 0.860(a) 0.696(a) 0.444(b) 0.684(a)

0.367 0.327 0.368 0.526(b) 0.535(b) 0.868(a) 0.602(a)

0.063 0.064 0.310 0.195 0.331 0.222

0.641(a) 0.715(a) 0.315 0.161 0.304

0.801(a) 0.402 0.115 0.376

0.489(b) 0.309 0.481(b)

0.715(a) 0.995(a)

0.782(a)

Correlation is significant at the 0.01 level (2-tailed). Correlation is significant at the 0.05 level (2-tailed).

PC1 indicated mixed sources of debromination of highly brominated BDE compounds and the direct sources of commercial Pentaand Octa-BDE products. PC 2 was responsible for 27.1% of the total variance and was highly predominated by BDE 209, followed by BDE 99, BDE 85 and BDE 47. The latter three BDE congeners were all observed in the commercial Penta-BDE products and BDE 209 was the main component of commercial Deca-BDE products (La Guardia et al., € din et al., 1998), so PC2 may indicate the direct contri2006; Sjo bution from the commercial Penta-BDE and Deca-BDE source. PC 3 explained 14.0% of the total variance and had loadings on BDE 35. Similar to BDE 10 and BDE 37 in PC1, BDE 35 was not observed in any of the commercial Penta-, Octa- and Deca-BDE products, either. Therefore, PC3 can be attributed to the individual contribution from the debromination of highly brominated BDE congeners. 4. Conclusion In conclusion, the present research work has provided valuable information on the PBDE contamination level in surface sediments collected from the Yellow River Estuary, China. Compared with other reported data about PBDEs in sediments in the world, the pollution levels of PBDEs in the present study were relatively low. Along the reach of the Yellow River Estuary, the sediments out of the natural reserve (Section 1) and near the mouth of the estuary (Section 3) were prone to receive more PBDEs. BDE 209, BDE 47, BDE 99 and BDE 183 were the major PBDE congeners here. Although the commercial Penta-BDE and Octa-BDE products have been banned in the world, the residual commercial Penta-BDE, Octa-BDE, Deca-BDE products and the debromination of highly brominated BDE compounds were still found to be the possible sources to the PBDE contamination here. Therefore, much more emphasis should be placed on continuous monitoring and effective pollution control of PBDEs in the Yellow River Estuary, China. However, the small sample size is one limitation existed in the present study. Considering the great difference of water flow in the Yellow River in different seasons, in the future research work, samples collected from different seasons should be further investigated to obtain the seasonal variation and contamination trends of PBDEs in the study area. Acknowledgments This work was supported by the National Natural Science Foundation of China (41373110) and Environmental Project of Anhui Province (2015-011). Special thanks are given to the editors and reviewers for their useful suggestions and comments.

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