Bioaccumulation and trophic transfer of polybrominated diphenyl ethers (PBDEs) in biota from the Pea

Bioaccumulation and trophic transfer of polybrominated diphenyl ethers (PBDEs)in biota from the Pearl River Estuary,South China

Mei Yu a ,b ,Xiao-Jun Luo a ,?,Jiang-Ping Wu a ,b ,She-Jun Chen a ,Bi-Xian Mai a

a State Key Laboratory of Organic Geochemistry,Guangzhou Institute of Geochemistry,Chinese Academy of Science,Guangzhou 510640,China b

Graduate School of Chinese Academy of Science,Beijing,100039,China

a b s t r a c t

a r t i c l e i n f o Article history:

Received 16March 2009Accepted 12June 2009

Available online 17July 2009

Keywords:

Polybrominated diphenyl ethers (PBDEs)Biomagni ?cation Bioaccumulation Pearl River Estuary

Two hundred and ?fty-four biota samples (four species of invertebrates and ten species of ?sh)were collected from the Pearl River Estuary between 2005and 2007and one hundred and twenty four individual or composite samples were analyzed for polybrominated diphenyl ethers (PBDEs).The concentrations of PBDEs in organisms varied from 6.2to 208ng/g lipid weight.This PBDE level was signi ?cantly lower than those collected in 2004,showing a decreasing trend of PBDEs in biota in the study area.Trophic magni ?cation factors (TMFs)for nine BDE congeners were calculated with values ranging from 0.78to 3.0.TMFs of BDE47,66,100,99,154,and 153were statistically greater than one,indicating a biomagnifcation potential for these congeners.Signi ?cant positive correlations were also found between concentrations of the total PBDEs,BDE28,47,66,100,99,154,and153and lipid content in biota,indicating the that bioconcentration also played an important role in the accumulation of PBDEs.No correlation between trophic level and lipid content was found,suggesting that biomagni ?cation was not the result of lipid content effect but indeed occurred.The concentration ratios of BDE99to BDE100were much lower in biota than that in water implying that potential congener-speci ?c biotransformation of PBDEs occurred and in ?uenced the biomagni ?cation of BDE congeners.

1.Introduction

Polybrominated diphenyl ethers (PBDEs)are ?ame retardants widely used in plastic,textile,electronic and other material.Because of their ubiquity in the environment (Law et al.,2008;Schecter et al.,2003;Vonderheide et al.,2008)and their exponentially increasing concentrations in most environment compartments with doubling times of about 4–6years (Chen et al.,2007;Hites,2004),the behaviors of PBDEs in environment have attracted great attention and interests from the public and environmental community.Available toxicological evidences indicate that PBDEs can disturb thyroid homeostasis,cause hepatomegaly and neurobehavioral de ?cits,and exhibit fetal and maternal toxicity after prolonged exposure (Darnerud et al.,2001;McDonald,2002).

PBDEs are capable of bioaccumulation in the biota own to their properties of high lipophilicity (log K OW :5.9–10)and resistance to metabolism (Gustafsson et al.,1999).Recently,a few of papers reported that the bioaccumulation and biomagni ?cations of PBDEs in biota,mostly focused on the marine and fresh food webs,and the conclusions varied.For example,Wan et al.(2008)have reported that concentrations of BDE28,47,100and 119increased signi ?cantly with the increasing trophic levels in a marine food web of Bohai Bay.In the tropical –

subtropical waters,BDE47,100and 154were found biomagni ?cations but BDE66,99and 209were found trophic dilution in a fresh water food web from a contaminated reservoir in South China (Wu et al.,2009).While analyses of PBDEs in biota from a fresh water food web from Lake Winnipeg indicated that only BDE47and BDE209have TMF greater than one (Law et al.,2006).Burreau et al.(2006)found the absence of biomagni ?cation for the highly brominated diphenyl ethers such as BDE209and nona-BDEs and the slight biomagni ?cation for BDE47(TMF=1.5,calculated from B value)in the northern Atlantic Ocean food web.On the other hand,studies conducted by Guo et al.(2008)and Wang et al.(2007)found the absence of biomagni ?cation for PBDEs in the organisms from the Pearl River Estuary and from a river receiving ef ?uent discharged from a large sewage treatment,respectively.These results indicated that the bioaccumulation behavior of PBDEs in biota was complex and needs more ?eld research.

The Pear River Estuary is located in the Pearl River Delta region of southern China,one of the most economically developed regions in China.Many researches have evidenced the Pear River Estuary as a signi ?cant sink for organic pollutants including PBDEs from upstream runoff,which posed risks to the organisms in the region (Mai et al.,2005;Luo et al.,2008;Wurl et al.,2006).Guo et al.(2008)have carried out a preliminary research about accumulation of PBDEs in biota in this area and found the absence of biomagni ?cation of PBDEs in the food web.The limited samples number (50samples for 34species,average less than 2samples for each species)and short food

Environment International 35(2009)1090–1095

?Corresponding author.Tel.:+862085290146;fax:+862085290706.E-mail address:luoxiaoj@https://www.360docs.net/doc/9212918280.html, (X.-J.

10.1016/j.envint.2009.06.007

Contents lists available at ScienceDirect

Environment International

j o u r n a l h o me p a g e :w w w.e l s ev i e r.c om /l o c a t e /e n v i n t

web may mask the biomagni?cation of PBDEs in the food web.In the present study,we analyzed concentrations of10BDE congeners in the food web(including four invertebrate species and ten?sh species) and their relationship withδ15N and lipid content to understand their accumulation behaviors in the food web.We also compared the concentration ratios of BDE99to BDE100between biota and water samples to explore the potential congener-speci?c biotransformation of PBDEs in biota sample and its in?uence on the biomagni?cations of BDE congeners.

2.Materials and methods

2.1.Sampling

Organisms were collected using?sh trawls in the Pearl River Estuary during August2005and August2007.The detailed information about the sampling area has been given elsewhere(Xiang et al.,2007).All samples were stored in cool boxes and transported to the laboratory and then immediately transferred to a freezer where they were stored at?20°C until analysis.The biota species collected in the present study included sand swimming crab(Ovalipes punctatus,three composite samples from nine individuals),samoan crab(Scylla serrata,two composite samples form six individuals),ark shell(Tegillarca granosa,three composite samples from sixty individuals),oncomelania(Oncomelania hupensischiui, three composite samples from thirty individuals),common mullet(Mugil cephalus,seven individual samples),red eelgoby(Odontamblyopus rubicundus,three composite samples from?fteen individuals),robust tongue?sh(Cynoglossus robustus,seventeen individual samples),slimy spinefoot(Siganus canaliculatus,twelve individual samples),silver sillago (Sillago sihama,?ve individual samples),pompano(Psenopsis anomala,six composite samples from thirty individuals),Japanese eel(Anguilla japonica,nineteen individual samples),?athead?sh(Platycephalus indicus, twenty seven individual samples),large yellow croaker(Pseudosiaena crocea,eleven individual samples),and bombay duck(Harpodon nehereus, six individual samples).Detailed information on the samples was provided in Table1.Zooplankton samples were also collected using a tow net of160μm in August2007,and the trawling depth ranged from0to 3m.Two composite zooplankton samples were obtained and stored at ?20°C and further for nitrogen isotope measurements.A total of one hundred and twenty four samples were analyzed for PBDEs in this study.

2.2.Reagents and chemicals

All PBDE standards were purchased from Accustandards Inc.(New Haven,CT).CDE99(2,2′,4,4′,5-pentachlorodiphenyl ether)was obtained from Wellington Laboratories(Ontario,Canada).13C12-PCB141and13C12-PCB208were obtained from Cambridge Isotope Laboratories(Andover,MA,USA).All organic solvents were analytical reagent and redistilled using a glass system.

2.3.Extraction and cleanup

Before the further treatment,the length and weight were recorded for each individual?sh.Samples were thawed and dissected to remove skin and bones.Muscle?llets below the dorsal?n for?sh and the soft part(edible part)for invertebrates were taken.The procedure for biota sample extraction and cleanup was described in detail in our previous studies(Xiang et al.,2007;Wu et al.,2008).Brie?y,after being homogenized with ashed anhydrous sodium sulfate and spiked with surrogate standards(CDE99and13C12-PCB141),the samples were Soxhlet extracted with hexane/acetone(1:1,v/v)for48h.The extracts were concentrated and an aliquot of the extract was used to lipid content determination by gravimetric method,the other aliquot was subjected to gel permeation chromatography(GPC)to remove lipids.The cleaned extract was concentrated to approximately1mL and further puri?ed passing through a multilayer silica/alumina column.The extracts

were 1091

M.Yu et al./Environment International35(2009)1090–1095

concentrated,solvent exchanged to hexane,and ?nally concentrated to 50μL under a gentle stream of nitrogen.A known amount of internal standard (BDE118,BDE128and 13C 12-PCB208)was added to all extracts prior to instrumental analysis.2.4.Instrumental analysis

Polybrominated diphenyl ethers (PBDEs)were measured with a Shimadzu model 2010gas chromatograph coupled with a model QP2010mass spectrometer (Shimadzu,Japan)using electron capture negative ionization (ECNI)in the selective ion monitoring (SIM)mode.A DB-XLB capillary column (30m×0.25mm i.d.×0.25μm ?lm thickness)was used to determine the tri-to hepta-BDEs (BDE28,47,66,100,99,85,153,154,138,and 183).For deca-BDEs (BDE209),a CP-Sil 13CB capillary column (12.5m×0.25mm i.d.×0.20μm ?lm thickness)was used.Details of the GC temperature program as well as the procedure for quali ?cation and quanti ?cation of PBDEs were given in published literature (Mai et al.,2005).The limit of detection (LOD),de ?ned as a signal/noise ratio (S/N)=5,ranged from 0.001to 0.38ng/g lipid weight.BDE85was not quanti ?ed in all the samples because of chromatographic interferences.2.5.Quality assurance/quality control

Quality assurance was done by analyses of procedural blanks,triplicate spiked blanks,and triplicate spiked matrices.For each batch of 12samples,a procedural blank was processed.Some of the procedural blanks (n =15)contained traces of target chemicals,but the levels were close to the limit of quanti ?cation and they were not subtracted from those in samples.The mean recoveries of individual congeners (BDE28,47,66,100,99,153,154,138,and 183)ranged from 61%to 87%with relative standard deviations (RSDs)less than 10%in triplicate spiked blanks and from 61%to 82%with RSDs less than 15%in triplicate spiked matrices,respectively.The surrogate standard recoveries of CDE99and 13

C 12-PCB141were 83%±13%(ranged from 46%–125%)and 86%±16%(51%–118%),respectively.No surrogate corrections were made to ?nal reported concentrations.

2.6.Nitrogen isotope measurements

About 1mg of homogenized and ?nely ground sample was wrapped with a tin cup,and placed in the sample container of an elemental analyzer-isotope ratio mass spectrometer (CE ?ash EA1112-Finnigan Delta plus XL)for stable nitrogen isotope ratio measurements.Two replicates of each sample were analyzed and the relative standard

deviation was less than 0.6%.The isotope ratio was standardized against air according to δ15N=(R sample /R air ?1)×1000‰,where R is the isotope ratio of 15N to 14N.The δ15N values were calibrated against a standard,ammonium sulfate (IAEA-N-1,International Atomatic Energy Agency Analytical Quality Control Services,Wien,Austria).The precision of the analytical method and instrument was ±0.3‰.

Trophic level (TL)was calculated for individual sample using the following equation (Post,2002):TL consumer =?eδ15

N consumer àδ15

N primary

consumer T =3:8

+2e1T

where 3.8is the isotopic trophic enrichment factor.

TMFs were calculated according to Tomy et al.(2004),and the references therein using following equations:Log concentration elipid ànormalized T=A +B TL

e2TTMF =10

e3T

statistical signi ?cance of the regression Eq.(2)was de ?ned at p b 0.05.2.7.Statistical analysis

For samples with contaminant concentration below LOD,zero was used for the calculations.All data were lipid-normalized.BDE85was not quanti ?ed due to chromatographic interference in some of the samples.Simple linear regressions and correlation coef ?cients were used to examine correlation between the levels of PBDEs and lipid contents and between the PBDE concentrations and the trophic levels.The level of signi ?cance was set at α=0.05throughout the present study.

3.Results and discussion

3.1.PBDEs concentrations in organisms

Of the 10PBDE congeners measured,BDE28,47,66,100,99,154,and 153were detected in more than 70%of samples but BDE138,183,and 209were detected in less than 60%of samples (59%,35%,and 18%,respectively)(Table 1).Therefore,data for ∑PBDEs only contained the congeners of BDE28,47,66,100,99,154,and 153.The ∑PBDE concentrations in biota from the Pearl River Estuary were summarized in Table 1.Bombay duck,ark shell,and large yellow croaker had relatively low PBDE concentrations with median of 9.8,13,and 13ng/g lipid weight (lw),respectively.Sand swimming crab,samoan crab,oncomelania,common mullet,red eelgoby,and silver sillago had similar PBDE levels with median ranging from 17to 21ng/g lw,which were lower than those (median ranged from 29to 32ng/g lw)in robust tongue ?sh,slimy spinefoot and Japanese eel.The highest concentration was found in ?athead ?sh with a median of 59ng/g lw.The levels of PBDEs in the present study were signi ?cantly lower than those (median ranged from 67to 194ng/g lw)in biota samples collected in the same area in 2004,in which the same muscle tissues were analyzed in several same species (Xiang et al.,2007),indicating a decrease trend for PBDE levels in biota in the study area.In the present study,samples of robust tongue ?sh,Japanese eel,and ?athead ?sh were annually collected in 2005,2006and 2007.The concentrations of ∑PBDEs in three years were illustrated in Fig.1.It was clear that a decreasing trend of ∑PBDEs in biota was observed although no statistical signi ?cance was obtained,which con ?rmed the above conclusion.

BDE47was the most abundant congener in aquatic species and was usually chosen as a representative of PBDE contaminants.In the present study,the concentrations of BDE47in biota ranged from 2.3to 38ng/g lw,which were close to the concentrations

Fig.1.Box plot concentrations of ∑PBDE in biota from the Pearl River Estuary among 2005and 2007.The ?ve lines from bottom to upper represent 5th,25th,50th,75th,and 95th percentiles,respectively.Solid circles indicate average values.Asterisks above or below the boxes represent the maximum and the minimum.

Table 2

Slope and p -value of regression analysis between logarithm of concentration and trophic levels,and TMFs for https://www.360docs.net/doc/9212918280.html,pound Slope R TMF p BDE28?0.110.160.780.090BDE470.360.42 2.29b 0.001BDE660.270.29 1.86b 0.001BDE1000.470.46 2.95b 0.001BDE990.420.31 2.63b 0.001BDE1540.440.35 2.75b 0.001BDE1530.370.31 2.34b 0.001Sum BDEs

0.36

0.43

2.04

b 0.001

1092M.Yu et al./Environment International 35(2009)1090–1095

?shes from Lake Winnipeg,Canada (1.8–84ng/g lw)(Law et al.,2006),from southern Greenland (7.9–41ng/g lw)(Christensen et al.,2002),and from Canadian Arctic (2.9–26ng/g lw).The concentrations of BDE47in the present study were much lower than those reported concentrations in Laizhou Bay (30–240ng/g lw)(Jin et al.,2008),and coastal British Columbia (6.1–160ng/g lw)(Ikonomou et al.,2002)but higher than those from Vietnam Can Tho (0.4–0.7ng/g lw)(Minh et al.,2006),and Bohai Bay (0.03–3.8ng/g lw)(Wan et al.,2008).

3.2.Trophic magni ?cation factors (TMFs)

The structure of the Pearl River Estuary food web was elucidated using stable isotopes of nitrogen.Stable isotope values for the biota were shown in Table 1.The average δ15N for zooplankton was 9.7‰,and was assumed as primary consumer,i.e.,TL =2.0,because of their herbivorous feeding on primary producers (photoplankton)(Post,2002).Trophic level differed among organisms,with two distinct

groups

Fig.2.Relationships between concentrations of PBDE congeners (ng/g lw)and trophic levels of biota.

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M.Yu et al./Environment International 35(2009)1090–1095

apparent.Sand swimming crab,oncomelania,and common mullet occupied a relative lower trophic position (range in means TL of 2.4–2.6)than all other species (mean TL of 3.4–3.8)(Table 1).

Regression analysis was conducted between the lipid-normalized concentrations of PBDEs (log-transformed)and the trophic levels.Table 2and Fig.2illustrate that strong positive relationships (TMF N 1,p b 0.01)between chemical concentration (log C)and trophic level were observed for all PBDE congeners except for BDE28,which showed a negative relationship.A TMF value of 2.0was observed for ∑PBDEs concentration.TMFs for individual PBDE congeners ranged between 0.78and 3.0(Table 2).With exception of BDE28,all TMFs were signi ?cantly larger than one,indicating their biomagni ?cation in the food web.This result was contrary to that reported in a previous study conducted by Guo et al.(2008)in the same study area.In that study,a total of 50samples from 34species (23samples from the PRE and 27samples from the Daya Bay)were collected.No signi ?cant correlations between concentrations of PBDEs (normalized to lipid content)and δ15N values were found.Bioconcentration,rather than biomagni ?cation,was suggested as major accumulation mechanisms of PBDEs in ?sh in the Pearl River Estuary.Such discrepancy may be due to the difference in tropic levels occupied by organisms between the two studies.In Guo's study,the mean δ15N value of ?sh was 11‰which was much lower than that (mean 16‰)in the present study.Additionally,relatively small number of biota samples (50samples for 34species,the averaged sample number for one species was less than 2)may be another reason for the absence of biomagni ?cations of PBDEs in Guo's investigation.

The observed biomagni ?cations for most BDE congeners were also reported in the food webs from Bohai Bay,North China and from Baltic Sea and northern Atlantic Ocean (Wan et al.,2008;Burreau et al.,2006).The TMF values of seven individual congeners (BDE28,71,47,66,100,119and 99)and total PBDEs ranged from 1.56(BDE99)to 7.24(BDE47)in the food web from Bohai Bay,North China,and the values signi ?cantly larger than one were obtained for BDE28(3.57,p =0.024),BDE47(7.24,p =0.006),BDE100(3.23,p =0.049),BDE119(2.6,p =0.042)and total PBDEs (3.53,p =0.046).The TMF values in the present study were lower than those in the food web from Bohai Bay,North China,which may be due to the different food web structure.The food web from Bohai Bay included zooplankton and birds as well as invertebrates and ?sh.Several previous studies demonstrated that TMFs of hydrophobic organics,such as HCB,HCH,p,p ′-DDE and PCBs,estimated based on a food web including only poikilotherms (invertebrates,?sh)were usually lower than those estimated based on a food web including both poikilotherms and homoetherms (sea-birds and mammals)(Fisk et al.,2001;Hop et al.,2002;Wan et al.,2008).In the food webs from the Baltic Sea and the northern Atlantic Ocean,Burreau et al.(2006)also found that PBDEs with up to 6–7bromine atoms biomagni ?ed.However,no biomagni ?cation was found for all PBDE congeners (BDE28,66,99,100,118,153,and 154)but for BDE47in a Canadian arctic marine food web in a study conducted by Kelly et al.(2008).The authors suggested that biotransformation of PBDEs was the main reason for no observed biomagni ?cation.Wu et al.(2009)found biomagni ?cations for BDE47,100,and 154,but trophic dilution for BDE66,99,153,183,and 209in a highly contaminated freshwater food web from South China.The enhanced metabolic capacity induced by the high level of PBDE in organisms and the high temperature in water was responsible for this observation.

Correlation between TMFs and log K OW is expected because trophic level is diet-based and biomagni ?cation from diet correlates with K OW (Campfens and MacKay,1997).In the present study,a line positive correlation was found between TMF and log K OW (Fig.3),which was consistent with the expectation.However,it should be borne in mind that only seven BDE congeners were considered in the present study.The limited BDE congener numbers used in the present study might mask the realistic relationship between TMF and log K OW.A parabolic relationship between biomagni ?cation power (B )of BDE congener and log K OW was observed in a food web from the Baltic Sea (Burreau et al.,2004).The highest biomagni ?cation potential was found in BDE99then biomagni ?cation power decreased with increasing log K OW .In the present study,a

similar trend could also be found if taking into account of BDE138(TMF=1.7,p =0.15)and BDE183(TMF=1.8,p =0.26),in which BDE100had the highest TMF then TMF decreased with increasing degree of bromination.Similar parabolic relationship between TMF and log K OW has also been reported for PCBs in marine (Borg?et al.,2004;Kelly et al.,2008)and freshwater (Walters et al.,2008;Wu et al.,2009)food webs.This result suggested that the bioaccumulation behavior of PBDEs may be similar to that of PCBs.

3.3.Bioaccumulation behavior of PBDEs

Congener-speci ?c metabolism of PBDEs in the food web components undoubtedly plays a key role in the bioaccumulation of PBDEs (Kelly et al.,2008;Wu et al.,2009).Previous studies have indeed shown that biotransformation of PBDEs occurred in some ?sh.For example,Stapleton et al.(2004)observed in vivo debromination of BDE99to BDE47,and BDE183to 154in common carp.Voorspoels et al.(2003)suggested that the ratio of BDE99to BDE100could be related to the difference in metabolism in aquatic organisms,which have been further con ?rmed by the study of Xiang et al.(2007).In the present food web,the TMF value of BDE100was higher than that of BDE99,which was consistent with the results of previous studies in aquatic ecosystem although both of the chemicals had similar K OW (Wu et al.,2009;Wan et al.,2008;Law et al.,2006).The ratios of BDE99to BDE100in biota and water which supported the habitation of the organisms were investigated to take an insight to the potential in ?uence of biotransformation on biomagni ?cation.Water samples were collected at the same time as that of organisms.As shown in Fig.4,the concentration ratios of BDE99to BDE100in water samples (median of 5.3,unpublished data)were signi ?cantly higher than those in biota samples (median of 0.5),and the ratios in low tropic level organisms such as sand swimming crab,oncomelania,and common mullet were higher than those in other high tropic level organisms.This result implied that organisms with higher tropic levels had increased metabolism ability,which was in line with the results from other studies (Wan et al.,2008;Wu et al.,2009).This result can also be used to explain why the TMF of BDE99was usually lower than that of BDE100in aquatic ecosystem.Thus,the extent of biotransformation in food web should be considered to elucidate the bioaccumulation behavior of

PBDEs.

Fig.3.Relationship between TMFs and log K OW for PBDEs.Log K OW values were taken for

PBDEs.

Fig.4.Box plots of the ratios of BDE99to BDE100in different biota species and water (unpublished data).The ?ve lines from bottom to upper represent 5th,25th,50th,75th,and 95th percentiles,respectively.Solid circles indicate average values.Asterisks above or below the boxes represent the maximum and the minimum.SS:sand swimming crab (Ovalipes punctatus );ON:oncomelania (Oncomelania hupensischiui );CM:common mullet (Mugil cephalus );Other species contain ark shell (Tegillarca granosa ),red eelgoby (Odontamblyopus rubicundus ),robust tongue ?sh (Cynoglossus robustus ),slimy spinefoot (Siganus canaliculatus ),silver sillago (Sillago sihama ),pompano (Psenopsis anomala ),Japanese eel (Anguilla japonica ),?athead ?sh (Platycephalus indicus ),large yellow croaker (Pseudosiaena crocea ),and bombay duck (Harpodon nehereus ).Table 3

Slope and p -value of regression analysis between logarithm of concentration and logarithm of lipid percent lipid contents in https://www.360docs.net/doc/9212918280.html,pound Slope R p BDE28 1.20.61b 0.001BDE470.890.57b 0.001BDE660.970.61b 0.001BDE1000.710.46b 0.001BDE99 1.10.53b 0.001BDE1540.670.39b 0.001BDE1530.630.61b 0.001Sum BDEs

0.89

0.61

b 0.001

1094M.Yu et al./Environment International 35(2009)1090–1095

In cold water lakes,?sh with higher concentrations of PBDEs tend to be the fattiest within a species and in a food web(Law et al.,2006).There was a signi?cantly consistent relationship between log PBDEs(ng/g wet weight)and log percent lipid in the organisms from the Pearl River Estuary(r=0.39–0.61,p b0.001)(Table3),and the slopes of the regression lines ranged from0.63to1.2.These values were slightly higher than the results of the previous study in the Pearl River Estuary(The slope of the regression line for total PBDEs was0.65.)(Guo et al.,2008).The correlations between the PBDE concentrations and lipid contents maybe resulted from either bioconcentra-tion of the chemicals from environmental exposure and/or biomagni?cation via food web(Bentzen et al.,1996;Mbongwe et al.,2003).In the present study,no correlation was found between the trophic level of organisms and the percent of lipid.This implied that the biomagni?cation of PBDEs observed in the present study was not the result of lipid content effect.Therefore,we can conclude that biomagni?cations of PBDEs via food web indeed occurred in the present food web,but the bioconcentration cannot be ruled out as another important bioaccumulation mechanism of PBDEs in biota in the studied food web.

4.Conclusions

PBDE concentrations and the trophic levels were measured in fourteen species of biota from the Pearl River Estuary.The results of the present study clearly indicated that BDE congeners(BDE47,66,100,99, 154,and153)exhibited biomagni?cation potential in the food web.On the other hand,bioconcentration that biota accumulated PBDEs directly from the environment cannot be neglected as an important route of bioaccumulation of PBDEs in biota.The signi?cant difference of ratios of BDE99to BDE100between water and biota samples implied that congener-speci?c biotransformation occurred and in?uenced the observed TMF of the food web.

Acknowledgments

This work was?nancially supported by the National Science Foundation of China(20890112,40525012,40821003),and the National Basic Research Program of China(No.2009CB421604).This is contribution No.is-1098from GIGCAS.We thank Mr.T.S.Xiang for assistance in GC/MS.

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