Scholarly article on topic 'Levels and distribution of polybrominated diphenyl ethers in Three Gorges Reservoir, China'

Levels and distribution of polybrominated diphenyl ethers in Three Gorges Reservoir, China Academic research paper on "Chemical sciences"

CC BY-NC-ND
0
0
Share paper
Academic journal
Emerging Contaminants
OECD Field of science
Keywords
{PBDE / "Virtual organism (VO)" / Sediment / "Suspended sediment (SS)" / Biofilm / "Three Gorges Reservoir (TGR)"}

Abstract of research paper on Chemical sciences, author of scientific article — Jingxian Wang, Yonghong Bi, Bernhard Henkelmann, Zeyu Wang, Gerd Pfister, et al.

Abstract Polybrominated diphenyl ethers (PBDEs) were investigated in water, sediments, suspended sediments and biofilms in Three Gorges Reservoir (TGR), China. Results showed that dissolved bioavailable PBDEs in water of TGR collected with semipermeable membrane device (SPMD)-based virtual organisms (VOs) were very low in the range of n.d. to 811 pg/g lipid and the detected compounds were mainly low molecular BDEs such as BDE-15, 17, 28, 47, 49, 66, 99 and 100. The PBDE levels in the sediment core collected near the dam were also very low in the range of 84–300 pg/g dw and the detected compounds were mainly large molecular BDEs such as BDE-196, 197, 206, 207 and 208. In suspended sediments and biofilms, the levels of PBDEs ranged from 298 to 52,843 pg/g dw and the detected compounds were also mainly large molecular BDEs such as BDE- 196, 197, 201, 203, 206, 207, 208 and 209. The dominant compound was BDE-209 which accounted for more than 90% of the total BDEs. Therefore, large molecular BDEs tended to be attached on fine particles. The vertical profile of BDEs on suspended sediments (SS) showed that SSs in the middle depth of water contained high level of BDE-209. The phenomenon indicated that most of BDE-209 did not settle into the sediment in front of the dam, instead transported further to downstream.

Academic research paper on topic "Levels and distribution of polybrominated diphenyl ethers in Three Gorges Reservoir, China"

Emerging Contaminants xxx (2017) 1—6

ADVANCING RESEARCH EVOLVING SCIENCE

Contents lists available at ScienceDirect

Emerging Contaminants

journal homepage: http://www.keaipublishing.com/en/journals/ emerging-contaminants/

Emerging Contaminants

Levels and distribution of polybrominated diphenyl ethers in Three Gorges Reservoir, China

Jingxian Wang a'b'c' *, Yonghong Bi a, Bernhard Henkelmann b, Zeyu Wang d, Gerd Pfister b, Karl-Werner Schramm b'c' **

a State Key Laboratory of Freshwater Ecology and Biotechnology, Institute of Hydrobiology, Chinese Academy of Sciences, Wuhan, 430072, China b Helmholtz Zentrum München - German Research Center for Environmental Health (GmbH), Molecular EXposomics (MEX), Ingolstädter Landstr.l, D-85764, Neuherberg, Germany

c Technische Universität München, Wissenschaftszentrum Weihenstephan für Ernährung, Landnutzung und Umwelt, Department für Biowissenschaften, Weihenstephaner Steig 23, 85350, Freising, Germany d Department of Engineering, University of Waterloo, Ontario, Canada

ARTICLE INFO

ABSTRACT

Article history:

Received 22 September 2016 Received in revised form 19 January 2017 Accepted 23 January 2017 Available online xxx

Keywords: PBDE

Virtual organism (VO) Sediment

Suspended sediment (SS) Biofilm

Three Gorges Reservoir (TGR)

Polybrominated diphenyl ethers (PBDEs) were investigated in water, sediments, suspended sediments and biofilms in Three Gorges Reservoir (TGR), China. Results showed that dissolved bioavailable PBDEs in water of TGR collected with semipermeable membrane device (SPMD)-based virtual organisms (VOs) were very low in the range of n.d. to 811 pg/g lipid and the detected compounds were mainly low molecular BDEs such as BDE-15, 17, 28, 47, 49, 66, 99 and 100. The PBDE levels in the sediment core collected near the dam were also very low in the range of 84—300 pg/g dw and the detected compounds were mainly large molecular BDEs such as BDE-196,197, 206, 207 and 208. In suspended sediments and biofilms, the levels of PBDEs ranged from 298 to 52,843 pg/g dw and the detected compounds were also mainly large molecular BDEs such as BDE- 196, 197, 201, 203, 206, 207, 208 and 209. The dominant compound was BDE-209 which accounted for more than 90% of the total BDEs. Therefore, large molecular BDEs tended to be attached on fine particles. The vertical profile of BDEs on suspended sediments (SS) showed that SSs in the middle depth of water contained high level of BDE-209. The phenomenon indicated that most of BDE-209 did not settle into the sediment in front of the dam, instead transported further to downstream.

Copyright © 2017, KeAi Communications Co., Ltd. Production and hosting by Elsevier B.V. on behalf of KeAi Communications Co., Ltd. This is an open access article under the CC BY-NC-ND license (http://

creativecommons.org/licenses/by-nc-nd/4.0/).

1. Introduction

Polybrominated diphenyl ethers (PBDEs) are widely utilized fire retardants embedded in textiles, plastics, electrical components, paints, foam, rubber, and other casing material [1]. They are halo-genated organic compounds which are hydrophobic, bio-accumulative, and persistent [2]. Due to their toxicity of reproductive, immunologic, and neurologic disruptive nature [3],

* Corresponding author. Department of Biosciences, TUM, D-85350, Freising, Germany.

** Corresponding author. Department of Biosciences, TUM, D-85350, Freising, Germany.

E-mail addresses: wangjx@ihb.ac.cn (J. Wang), schramm@wzw.tum.de (K.-W. Schramm).

Peer review under responsibility of KeAi Communications Co., Ltd.

these compounds have been extensively investigated in many environmental matrices. A stable or increasing trend of concentration found in these matrices has caused great concern [4,5].

The Three Gorges Area (TGA) has been rice and orange fields for several centuries with a populous area of 55,800 km2. Economically, the people (16 million) in TGA depend on the Three Gorges Reservoir (TGR) as a source of fresh drinking water and fishing as a source of favorite food in the local diet. The Three Gorges Dam (TGD) constructed on the Yangtze River in China is the largest hydro-electricity project in the world which created the TGR with an area of 1080 km2. The closing of the TGD has resulted in drastic environmental alterations, for example, water flow becomes much slower which influences contaminants transport and fate in the water system. So far, the information on the contamination of PBDEs in TGR is limited. Available references include reports of Zhao et al. [6] on investigating PBDEs in surface sediments from

http://dx.doi.org/10.1016/j.emcon.2017.01.003

2405-6650/Copyright © 2017, KeAi Communications Co., Ltd. Production and hosting by Elsevier B.V. on behalf of KeAi Communications Co., Ltd. This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/4.0/).

J. Wang et al. / Emerging Contaminants xxx (2017) 1—6

TGR and Wolf et al. [7] for determining water concentration of PBDEs in TGR. However, no information is available on sediment cores, suspended sediments and biofilms in TGR. To better understand the environmental behavior of these compounds in the reservoir and their potential risk, it is essential to investigate their distribution, congener profiles, transportation and inventories in the different matrices in TGR.

The objectives of this study were to determine occurrence and congener profiles of PBDE in water, sediment cores, suspended sediments and biofilms from Three Gorges Reservoir and to evaluate the level, distribution and transportation of PBDEs in TGR. Triolein containing semipermeable membrane device (SPMD) were used as biovirtual organism (VO) to collect PBDE congeners in the water column. Biofilm was the biofouling grown on the surface of SPMD membranes. Sediment core and suspended sediment (SS) were collected in front of the dam to investigate the vertical distribution profile of PBDEs in the area.

2. Methods and materials

2.1. VO samplers and deployment in TGR

The SPMD-based VO samplers were prepared in the manner described in our previous paper [8]. Briefly, the semipermeable membranes were prepared using lay-flat polyethylene tubing (from VWR Ismaning, Germany; 2.5 cm wide and 65 mm thick). The tubing was cut into 29 cm pieces and 700 mL of triolein (Sigma, Munich, Germany, 99%) were pipetted into each piece of tubing before sealing the ends. For chemical analysis, the triolein was spiked with 16 13C-labeled PAHs (Cambridge Isotope Laboratories, USA) as performance reference compounds (PRC) [8]. The prepared VOs were stored in heat treated 10 mL glass vials with aluminum foil sealed at -28 ° C and kept cooled during transportation until deployment.

The sampling sites spanned the whole reservoir from the upstream Chongqing to the great dam, covering more than 600 km long distance. The sampling sites were MP (Maoping), GJB (Guo-jiaba), BD1 (Badong), BD2 (Badong), DN1 (Wushan), DN2 (Wushan), FJ (Fengjie), XJl(Yunyang), XJ2(Yunyang), WZ (Wanz-hou), CS (Changshou), CQ(Chongqing) (Fig. 1). In late April to May

2008, the SPMDs were deployed for 7 d and 25 d at seven sites (MP, GJB, BD1, BD2, WZ, CS, CQ) in the TGR and in the same period in

2009, the SPMDs were deployed for 14 d and 25 d at the same seven

sites. In the sampling campaign from late April to May in 2011, 5 sites were added for deploying SPMDs which were DN1, DN2, FJ and XJ1, XJ2.

The VOs were deployed in stainless steel cages and immersed into the water at about 1 m depth. Each cage contained 4 replicates of VOs. The samplers were mounted on boats or fastened to docks which were about 10—20 m from the river bank. The VOs for the determination of blanks were prepared together with the other VOs for sampling. VO blanks were transported to the sampling sites as well in clean airtight jars, not deployed. After retrieval, the VOs were transported to the laboratory in the corresponding glass jars protected from light and were kept in a freezer at -28 °C until processing.

2.2. Collection of sediment cores, suspended sediments and biofilms

Sediment cores were obtained with a stainless gravity sediment core sampler (100 cm in length and 25 cm in diameter) at MD (7 km away from the dam) in September 2012. The core was sliced into 10 cm fractions with a spatula from top to bottom layers. Suspended sediments (SS) were collected with multi-pore stainless boxes in September 2012 which were deployed in the water at the depths of 1,11, 21, 31, 41, 51 and 61 m at the same site MD for one month. Biofilms were collected by scraping gently the biofoulings from the surface of the SPMDs which were deployed in TGR in May of 2009 and May of 2011.

2.3. Sample extraction and clean up

All organic solvents were of picograde quality and were obtained from LGC standards (Wesel, Germany). For later quantification, samples were spiked before extraction with a mixture of 13C-labeled brominated flame retardants BFR-LCS (Wellington Laboratories, Canada) to monitor the extraction and cleanup procedures. All of the sediment samples, suspended sediments and biofilms were lyophilized. 1 —5 g of the samples were extracted with Accelerated Solvent Extractor by 100 mL solvent mixture of hexane and acetone (1:1 v:v). The extraction method for VO was according to our previous study [8]. In brief, the VO was cut into small pieces and extracted in 100 mL cyclohexane overnight at 200 rpm on a left-right shaker. The volume of the extraction solution of VOs or particles was reduced to one drop around 1 mL using vacuum rotary evaporation. The residue was redissolved again with

Fig. 1. Scheme of sampling sites in Three Gorges Reservoir.

J. Wang et al. / Emerging Contaminants xxx (2017) 1—6

approximately 1—2 mL mixture of n-hexane: dichloromethane (1:1 v:v) and the sample underwent cleanup using a mixed column (3 cm diameter column containing, from the bottom upward, 10 g silica, 5 g alumina with 3% H2O, 5 g anhydrous sodium sulfate). The extract was eluted with 100 mL mixture of n-hexane and dichloromethane (1:1 v:v) and reduced to 1 mL. The residue was further purified through a C18 SPE cartridge for which acetonitrile was used as eluting solvent. After adding a recovery standard BFR-SCS (Wellington Laboratories, Canada), the extract was concentrated with a gentle flow of nitrogen to 20 mL to be ready for analytical determination.

2.4. Chemical analysis and QA/QC

The analysis for the BFRs was performed by an Agilent 6890 high resolution gas chromatography (HRGC) plus MAT 95S (Thermo) high resolution mass spectrometry (HRMS) using a column of Rtx-1614 (15 m, 0.25 mm ID, 0.1 mm film thickness) (Restek). Helium was used as carrier gas at a flow rate of 1.3 mL/min. The GC/MS operating conditions were 50 eV EI with the MS ion source temperature at 260 °C. 1 mL of the sample was injected in a splitless mode with cooled injection system CIS4 (Gerstel) which is a programmable temperature vaporization injection. The temperature program of the injection port was: increase temperature from 120 °C to 300 °C at 12 °C s-1, then maintain at 300 °C for 5 min. The temperature of transfer line was 300 °C. The temperature program ofGC was: first hold at 100°C for 1.5 min, then increase to 230"Cat 10 "C min-1 and to 325 "C at 5 "C min-1, then hold for 6 min at 325 "C.

Routine quality procedures were executed. These included the analysis of control samples and VO blank samples. The latter were also used to obtain the amounts of PRC prior to exposure and the blank values of the other analytes. The method detection limits (MDL) were calculated on the basis of 3 times the standard deviation of the mean blank values. A result is valid when the margin between the sample value and the average blank value is larger than the MDL and is reported as a result after subtraction of the average blank value. Otherwise, the result is reported as less than MDL. When blank signals for a compound are not detectable, the MDLs were calculated on the basis of a signal-to-noise of 3:1 of the mass traces of the unlabeled compound. Every signal below this limit is treated as not detectable. The recoveries of the 13C-labeled internal standards, MDLs and blank levels of the different types of the samples were presented in Tables S1 —S3 (Supplement Information).

3. Results

3.1. PBDE levels in VO samples

22 VOs among which 10 were collected in 2008 and 12 in 2009 were processed for PBDEs analysis. 22 PBDE congeners were measured by HRGC\HRMS, only 10 of them were detected in 14 VOs (Table 1). The sum of PBDE values were n.d. — 811 pg/g lipid.

Aqueous concentrations of PBDEs in TGR which considering sampling time and water sampling rate were calculated according to the method described in our previous publication [9]. In brief, the aqueous concentrations of PBDEs are calculated according to the following equation:

1 " exp( " KWTs

absorbed by the samplers, Ksw is the sampler-water partition coefficient, Vs is the sampler volume, and Rs is the water sampling rate, t is the sampling time.

The sampling rates (Rs) of absorbed analytes are related to the PRC-based sampling rates (Rs, PRC) and calculated by

Rs = Rs, PRC

Vm, PRC

Where Cw is the aqueous concentration, N is the amount of analyte

where Vm and Vm, PRC are the molar volumes of analyte and PRC, respectively. The physicochemical parameters used for calculating the aqueous concentrations of PBDEs were presented in Table S4 (Supplement Information).

The aqueous concentrations of total PBDEs in water of TGR ranged from 6 to 23 pg/L (Table 1). In general, the concentrations of PBDEs in TGR were low.

3.2. PBDE levels in sediments and suspended sediments

5 fractions of the sediment core sample (from the top to 50 cm depth of core) and 4 suspended sediments (from the surface to 61 m depth of water) collected at MD were analyzed for the 37 BDEs (Table 2). Because it was in flood season, no biofilm was found on the surface of the samplers. The water current is very slow at the sampling site MD near the dam and the suspended sediments mainly went through a sedimentation process. No particles were collected in the water of 1 m and 11 m depths, while higher amount of particles were collected at the depths of 41 m and 51 m (Fig. 2). 14 out of the 37 BDEs were not detected in the sediment core and SS samples and the data were not presented. Relative high levels of BDE-209 were detected in SSs collected at 31 and 41 m depth of water. Unfortunately, there are empty cells in the table meaning we did not specify any values for these compounds due to low recovery of the analytical method for these samples for unknown reason. We could not generate BDE-209 value for all sediment samples, but it does not mean BDE-209 was not present in the sediment. The sum of BDEs excluding BDE-209 in sediment core ranged from 84 to 300 pg/g dw which was substantially low. Whereas, the sum of BDEs in SSs ranged from 1869 to 29,744 pg/g dw. If BDE-209 was excluded, the sum of other BDEs in SSs ranged from 1869 to 10,002 pg/g dw. The levels of BDEs excluding BDE 209 decreased in suspended sediments from the surface water to deep water and sediment core.

3.3. PBDEs in biofilms

37 BDEs in 14 biofilms were measured, only 11 of the BDE congeners were detected (Table 3). Relatively high concentrations of BDE-209 were detected in most of the biofilm samples which accounted for more than 90% of total BDEs. BDE-206, 207, 208 were also frequently detected with relatively high levels. The total BDEs ranged from 298 to 52,843 pg/g dw and that without BDE-209 ranged from 298 to 2937 pg/g dw.

4. Discussion

There are very limited references available regarding PBDE levels in water of TGR. Wolf et al. [7] investigated organic trace substances in TGR including PBDEs and found that PBDE levels were below their method detection limit of 5 ng/L. Our study utilized VO facility to accumulate PBDEs from water and improved the detection limit to 5 pg/L. In the present study, 22 PBDEs were measured in 22 VOs, but only 10 PBDE congeners were detected in 14 VOs and in very low levels. The sum of PBDEs values were n.d. —

4 J. Wang et al. / Emerging Contaminants xxx (2017) 1—6

Table 1

PBDEs in VOs (pg/g lipid) collected in 2008 and 2009 from TGR.

2008_7d 2008_25d 2009_14d 2009_25d

WZ CS BD2 WZ BD1 BD2 WZ CS GJB BD1 BD2 WZ CS CQ

BDE-15 (20) 35 (20) 75 10 12 19 7 4 15 26 6 19 33

BDE-17 10 10 5 27 7 8 13 6 (2) 4 25 4 14 27

BDE-28 33 46 32 125 21 20 38 16 (11) 14 58 (11) 37 76

BDE-47 (231) (231) (231) (231) (101) (101) (101) (101) (101) (101) (101) (101) (101) 197

BDE-49 20 24 30 65 32 18 32 13 17 (12) 40 20 31 60

BDE-66 13 23 25 49 (19) (19) 20 (19) (19) (19) (19) (19) (19) 40

BDE-99 (83) (83) (83) (83) 24 30 35 36 (20) 26 20 (20) 28 71

BDE-100 (20) (20) (20) (20) 9 10 13 (6) 14 16 21 9 19 37

BDE-154 (0) 65 (0) 112 (0) (0) (0) (0) (0) (0) (0) (0) (0) (0)

BDE- (0) 24 (0) 24 (0) (0) (0) (0) (0) (0) (0) (0) (0) (0)

SBDE ng/g lipid 430 561 446 811 223 218 271 204 188 207 310 190 268 541

SBDE g/ L 22 24 13 17 12 11 15 10 6 8 9 6 7 11

Note: samples in 2008_7d were MP, GJB, BD1, BD2, WZ, CS; samples in 2008_24d were MP, GJB, BD2, WZ; samples in 2009_14d were MP, GJB, BD1, BD2, WZ, CS; samples in 2009_25d were MP, GJB, BD1, BD2, WZ, CS, CQ. Only 4 of 2008 VOs and 10 of 2009 VOs were detected PBDEs and were presented in the table.

22 PBDEs were determined, i.e, BDE-7,10,15,17,28,30,47,49,66, 77,85,99,100,119,126,138,139,140,153,154,156 and 169; only 10 of the 22 PBDEs were detected and presented in the table, i.e. BDE-15, 17, 28,47, 49, 66, 99,100,154, 156.

Values with a bracket mean not detected and presented by limit of determination (LOD). Sum of BDEs were calculated by assuming that all values of the different congeners less than the LOD were equal to the LOD.

Table 2

PBDEs in sediment core and in suspended sediments collected near the dam.

pg/g dw MD10 cm MD20 cm MD30 cm MD40 cm MD50 cm SP21m SP31m SP41m SP61m

BDE-15 4.5 (0.8) (2.1) (0.8) (0.8) 126 (29.5) 11.0 (15.3)

BDE-17 2.7 2.0 (3.2) 0.87 1.2 46.9 (7.0) (13.7) (24.1)

BDE-28 9.1 (2.9) 5.0 3.1 4.1 145 (37.9) (9.3) (19.7)

BDE-47 (8.8) (8.8) (22.5) (8.8) (8.8) 3750 (915) (224) (476)

BDE-49 3.0 4.2 (1.8) 1.8 (1.0) (47.5) (7.2) (9.4) (15.6)

BDE-66 5.9 3.3 (2.6) 2.1 (1.4) (300) (90.7) (22.3) (47.2)

BDE-85 (1.1) (1.5) (2.5) (0.9) (1.1) 113 (8.9) (11.3) (23.7)

BDE-99 (2.3) (2.3) (5.8) (2.3) (2.3) 2141 (413) (101) (215)

BDE-100 4.5 2.7 3.9 2.8 2.8 (433) (131) (32.1) (68.0)

BDE-153 4.7 (3.7) (5.4) 6.3 (3.4) (317) (95.8) (23.5) 94.7

BDE-154 5.9 (3.3) (5.5) (3.0) 5.8 (145) (43.9) (10.8) (22.8)

BDE-171 (5.6) (8.5) (17.6) (3.5) (7.0) (196) (38.5) (51.0) (96.2)

BDE-180 (6.3) (9.5) (19.8) (3.9) n.d. (174) (34.2) (45.3) (85.5)

BDE-183 (3.7) (5.6) (11.6) 9.2 10.3 (129) (25.4) (33.7) (63.5)

BDE-184 (3.7) (5.6) (11.5) (2.3) (4.6) (134) (26.4) (35.0) (66.0)

BDE-196 6.8 (4.9) (9.8) 10.8 8.4 (63.2) 31.0 64.7 (38.0)

BDE-197 6.9 (4.4) (8.7) 7.0 4.8 (57.8) (15.4) 38.6 (34.8)

BDE-201 7.3 (3.9) (7.7) 8.1 6.4 (55.2) (14.7) 45.2 (33.2)

BDE-203 10.7 (5.8) (11.5) 14.5 12.2 (73.7) 40.4 79.4 (44.4)

BDE-206 104 63.7 (319) 152.9 653 (137.3)

BDE-207 67.2 63.2 (1036) (313) 745 (162.7)

BDE-208 36.7 33.2 (199) 73.4 391 (85.3)

BDE-209 4586.6 27,093

BDEs (no 209) 104 84 159 300 254 10,002 2545 2651 1869

sum 104 84 159 300 254 10,002 7132 29,744 1869

Note: value with a bracket means not detected and presented with LOD. Sum of PBDEs were calculated by assuming that all values of the different congeners less than the LOD were equal to the LOD.

37 BDEs (BDE-7,10,15,17, 28,30,47,49, 66, 71, 77, 85, 99,100,119,126,138,139,140,153,154,156,171,180,183,184,191,196,197,201,203, 204, 205, 206, 207, 208 and 209) were measured and only 23 of them were detected and presented in the table.

The empty cells in the table mean we did not specify any values for these compounds due to low recovery of the analytical method for these samples for unknown reason.

811 pg/g lipid. The calculated aqueous concentrations of PBDEs according to the sampling rates of PRCs were n.d. — 24 pg/L. Therefore, the concentrations of PBDEs in the water phase of TGR were substantially low.

Sediments have been recognized as both a major sink and a potential source for persistent toxic chemicals in aquatic systems

[10,11]. The sediment load of Yangtze River is 500 Mt (1 Mt = 1,000,000) per year [12]. From Changshou to the dam, the water becomes stagnant for most of the year and most of the suspended sediments settle down in TGR through a natural settling process. Large amount of the suspended sediments entered in the reservoir have settled down in the areas of CS and WZ [8]. Smaller

J. Wang et al. / Emerging Contaminants xxx (2017) 1—6

Fig. 2. The amount of suspended sediments collected in different depth of water at MD.

particles move further to the dam area where water is almost stagnant. The depth profile of the amount of SS in front of the dam shows that almost no SS in the water of 1 m and H m depth. However, the sedimentation did not finish in front of the dam, since the largest amount of SS was found in the water of 41 m depth. The levels of BDEs excluding BDE 209 decreased in suspended sediments from the surface water to deep water. Relative high level of BDE-209 was detected in SS41m and SS31m.

One sediment core in the area was collected and analyzed. The sums of BDEs excluding BDE-209 in the sediment were 84—300 pg/ g dw which were lower than that of SS61m (1869 pg/g dw). Because we did not generate values for BDE-209 in the sediment core, we have to refer to the reference of Zhao et al. [6] in which levels of ]TBDEs excluding BDE-209 in sediments from TGR in 2010 were n.d. — 146 pg/g which were close to our results. The values of BDE-209 in the reference were 47—503 pg/g which were much lower than those in SSs in our study. Therefore, most of BDE-209 in SSs may not settle down in the sediment in front of the dam, instead move downstream of the reservoir.

The levels of PBDEs in the sediments in front of the dam were comparable to those relatively uncontaminated freshwater areas,

such as Lake Ontario, Canada (2.8 ng/g dw) [13], Lake Superior, USA (0.49—3.114 ng/g dw) [14], Lake Michigan, USA (1.67—3.97 ng/g dw) [15], etc. The values were relatively lower than those in sediments in the downstream area of the Yangtze River [16,17]. The values were also very much lower than those in sediments in other waters in China, such as Pearl River Estuary and Laizhou Bay [18,19].

The water current becomes very slow in front of the dam after the dam closing which induces the growth of biofilms. The VOs deployed for nearly one month in TGR were covered with a layer of biofilm or biofouling. 14 biofilms were collected from VOs and 37 BDEs were measured. Only 11 out of the 37 BDEs were detected in most of the biofilms and most of detected BDEs were of high molecular weight (Table 3), among which BDE-209 accounted for more than 90%. The sums of BDEs except BDE-209 were 347—2937 pg/g dw, and BDE-209 ranged from 7314 to 49,906 pg/g dw. High levels of BDEs in biofilms indicated BDEs especially BDEs of high molecular weight tended to be absorbed on fine particles. In aquatic ecosystems, the majority of microorganisms live attached to the surface of rocks and plants [20]. These microbial communities are usually known as biofilms which could be food of protozoan predators. The pollutants attached on the biofilms therefore enter into food chain.

The levels of BDEs in biofilms and SSs in TGR were in the same magnitude with those in sediments from downstream area of the Yangtze river, such as BDEs (excluding 209) 0.39—34.44 ng/g and BDE-209 9.68—143.51 ng/g in Taihu lake [17] and ¿BDEs (excluding 209) n.d. — 0.55 ng/g and BDE-209 0.16—94.60 ng/g in Yangtze River Delta [16]. Therefore, we suppose that most of BDE-209 attached on fine particles in TGR may transport to downstream area. Further studies are needed on the transport and translocation of PBDEs from the attached and suspended particles to the aquatic food chain and their adverse effects on aquatic organisms.

5. Conclusion

PBDEs in water, sediment core, biofilm and suspended sediment were detected in TGR with a HRGC/HRMS analytical method. Water concentrations of PBDEs were low and most detected BDE compounds were of lower molecular weight such as BDE-28, 47, 49, 66, 99, 100. Sediment core in front of the dam contained very low concentration of PBDEs, whereas suspended sediments at the same area in the middle depth of the water were determined with much higher level of PBDEs than that in sediment. The biofilms in surface

Table 3

PBDEs in biofilms.

pg/g dw 2009 2009 CS 2011 2011 2011 2011 2011 2011 2011 2011 2011 2011 2011 2011

WZ MP GJB BD1 BD2 WZ CS CQ DN1 DN2 FJ XJ1 XJ2

BDE-17 n.d. 2.5 4.3 12.8 n.d. n.d. n.d. n.d. n.d. n.d. n.d. n.d. n.d. n.d.

BDE-49 n.d. 5.9 16.9 52.2 14.5 19.6 28.0 n.d. n.d. n.d. 33.0 14.2 21.0 24.9

BDE-183 n.d. 19.1 39.2 n.d. n.d. 29.0 n.d. n.d. n.d. n.d. 110 n.d. n.d. 41.8

BDE-196 44.0 18.3 31.1 n.d. 44.1 14.5 29.5 41.8 38.0 n.d. n.d. 24.5 20.9 29.4

BDE-197 n.d. 15.7 27.1 n.d. 35.6 20.9 29.2 14.2 26.0 n.d. 39.3 25.2 18.5 24.2

BDE-201 37.0 16.2 13.7 n.d. 21.2 10.3 n.d. 23.5 n.d. n.d. n.d. 15.8 15.2 n.d.

BDE-203 53.7 20.4 41.6 n.d. 55.0 24.9 40.1 52.6 38.0 n.d. n.d. 35.1 33.4 44.8

BDE-206 688 181 840 190 1189 125 404 404 205 821 n.d. 354 124 600

BDE-207 464 n.d. 472 n.d. 1053 n.d. 656 349 n.d. 1628 n.d. n.d. n.d. 596

BDE-208 n.d. 73.8 251 105 525 61.8 299 226 131 n.d. 115 191 76.6 230

BDE-209 32,215 7314 17,449 16,925 49,906 8324 8435 25,278 10,479 19,249

BDEs (no 209) 1286 351 1733 347 2937 305 1486 1112 438 2448 298 660 309 1591

sum 33,501 7665 19,182 17,272 52,843 8629 1486 1112 8873 2448 298 25,938 10,788 20,840

Note: n.d. means not detectable.

37 BDEs (BDE-7,10,15,17, 28, 30,47,49, 66, 71, 77, 85,99,100,119,126,138,139,140,153,154,156,171,180,183,184,191,196,197, 201, 203,204,205, 206, 207, 208 and 209) were measured and only 11 of them were detected and presented in the table.

The empty cells in the table mean we did not specify any values for these compounds due to low recovery of the analytical method for these samples for unknown reason.

J. Wang et al. / Emerging Contaminants xxx (2017) 1—6

water also contained similar higher levels of PBDEs with SSs, most of them were also BDEs of higher molecular weight, among which BDE-209 accounted for more than 90% of the total BDEs.

For the first time, PBDEs in suspended sediments and biofilms were studied in TGR. The low levels of PBDEs in water phase and higher levels of PBDEs in biofilm and suspended sediment indicated that PBDEs tended to be attached on fine particles. Low levels of PBDEs in sediment core suggested that most of the PBDEs on fine particles may not settle down in the sediment in front of the dam, instead passed to the downstream area of the Yangtze River. PBDEs attached on biofilms which could be food of protozoan predators and entered into food chain. Further studies are needed on the transport, transfer and fate of PBDEs in aquatic environment and their adverse effects on aquatic organisms.

Acknowledgement

This project was funded by the German Ministry of Education and Research (BMBF 02WT1132).

Appendix A. Supplementary data

Supplementary data related to this article can be found at http:// dx.doi.org/10.1016/j.emcon.2017.01.003.

References

[1] M. Petreas, D. Nelson, F.R. Brown, D. Goldberg, S. Hurley, P. Reynolds, High concentrations of polybrominated diphenylethers (PBDEs) in breast adipose tissue of California women, Environ. Int. 3 (2011) 190—197.

[2] P. Praipipat, L.A. Rodenburg, G.J. Cavallo, Source apportionment of poly-chlorinated biphenyls in the sediments of the Delaware River, Environ. Sci. Technol. 47 (2013) 4277—4283.

[3] T. Nouira, C. Risso, L. Chouba, H. Budzinski, H. Boussetta, Polychlorinated bi-phenyls (PCBs) and polybrominated diphenyl ethers (PBDEs) in surface sediments from Monastir Bay (Tunisia, Central Mediterranean): occurrence, distribution and seasonal variations, Chemosphere 93 (2013) 487—493.

[4] R.C. Hale, M.J. La Guardia, E. Harvey, D. Chen, T.M. Mainor, D.R. Luellen, L.S. Hundal, Polybrominated diphenyl ethers in U.S. sewage sludges and biosolids: temporal and geographical trends and uptake by corn following land application, Environ. Sci. Technol. 46 (2012) 2055—2063.

[5] N. Xiang, L. Chen, X.Z. Meng, Y.L. Li, Z.G. Liu, B. Wu, L.L. Dai, X.H. Dai,

Polybrominated diphenyl ethers (PBDEs) and dechlorane plus (DP) in a conventional wastewater treatment plant (WWTP) in Shanghai: seasonal variations and potential sources, Sci. Total Environ. 487 (2014) 342—349.

[6] G. Zhao, K. Li, H. Zhou, X. Liu, P. Zhang, W. Wen, Y. Yu, H. Yuan, Poly-halogenated aromatic hydrocarbons in surface sediments from Three Gorges Reservoir, J. Environ. Sci. Health Part A 48 (2013) 136—144.

[7] A. Wolf, A. Bergmann, R.-D. Wilken, X. Gao, Y. Bi, H. Chen, C. Schuth, Occurrence and distribution of organic trace substances in waters from the Three Gorges Reservoir, China, Environ. Sci. Pollut. Res. 20 (2013) 7124—7139.

[8] J. Wang, Y. Bi, G. Pfister, B. Henkelmann, K. Zhu, K.-W. Schramm, Determination of PAH, PCB, OCP in water from the Three Gorges Reservoir accumulated by semipermeable membrane devices (SPMD), Chemosphere 75 (2009) 1119—1127.

[9] J. Wang, B. Henkelmann, Y. Bi, K. Zhu, G. Pfister, W. Hu, C. Temoka, B. Westrich, K.-W. Schramm, Temporal variation and spatial distribution of PAH in water of Three Gorges Reservoir during the complete impoundment period, Environ. Sci. Pollut. Res. 20 (2013) 7071—7079.

10] W. Ahlf, H. Hollert, H. Neumann-Hensel, M. Ricking, A guidance for the assessment and evaluation of sediment quality: a German approach based on ecotoxicological and chemical measurements, J. Soils Sediments 2 (2002) 37—42.

11] U. Forstner, B. Westrich, BMBF coordinated research project SEDYMO (20022006): sediment dynamics and pollutant mobility in river basins, J. Soils Sediments 5 (2005) 134—138.

12] J. Zhang, Geochemistry of trace metals from Chinese river/estuary systems: an overview, Estuar. Coast Shelf Sci. 41 (1995) 631—658.

13] X. Qiu, C. Marvin, R. Hites, Dechlorane plus and other flame retardants in a sediment core from Lake Ontario, Environ. Sci. Technol. 41 (2007) 6014—6019.

14] W. Song, J. Ford, A. Li, W. Mills, D. Buckley, K. Rockne, Polybrominated diphenyl ethers in the sediments of the great lakes. 1. Lake superior, Environ. Sci. Technol. 38 (2004) 3286—3293.

15] W. Song, A. Li, J. Ford, N. Sturchio, K. Rockne, D. Buckley, W. Mills, Poly-brominated diphenyl ethers in the sediments of the great lakes. 2. Lakes Michigan and Huron, Environ. Sci. Technol. 39 (2005) 3474—3479.

16] S.J. Chen, X.J. Gao, B.X. Mai, Z.M. Chen, X.J. Luo, G.Y. Sheng, J.M. Fu, E.Y. Zeng, Polybrominated diphenyl ethers in surface sediments of the Yangtze River Delta: levels, distribution and potential hydrodynamic influence, Environ. Pollut. 144 (2006) 951—957.

17] P. Zhou, K. Lin, X. Zhou, W. Zhang, K. Huang, L. Liu, J. Guo, F. Xu, Distribution of polybrominated diphenyl ethers in the surface sediments of the Taihu Lake, China, Chemosphere 88 (2012) 1375—1382.

18] B. Mai, S. Chen, X. Luo, L. Chen, Q. Yang, G. Sheng, P. Peng, J. Fu, E.Y. Zeng, Distribution of polybrominated diphenyl ethers in sediments of the Pearl River Delta and adjacent South China sea, Environ. Sci. Technol. 39 (2005) 3521—3527.

19] J. Jin, W. Liu, Y. Wang, X.Y. Tang, Levels and distribution of polybrominated diphenyl ethers in plant, shellfish and sediment samples from Laizhou Bay in China, Chemosphere 71 (2008) 1043—1050.

20] J.W. Costerton, Introduction to biolfilm, Int. J. Antimicrob. Agents 11 (1999) 217—221.