Environ. Sci. Technol. 2003, 37, 892-898
Occurrence and Specific Congener Profile of 40 Polybrominated Diphenyl Ethers in River and Coastal Sediments from Portugal S IÄ L V I A L A C O R T E , * , † M IÄ R I A M G U I L L A M O Ä N,† E L E N A M A R T IÄ N E Z , † P A U L A V I A N A , ‡ A N D D A M I AÅ B A R C E L O Ä † Department of Environmental Chemistry, IIQAB, CSIC, Jordi Girona 18-26, 08034 Barcelona, Catalonia, Spain, and Instituto do Agua, Rua da Murgueira, Zambujal, Apartado 7585, Alfragide 2720, Portugal
Forty polybrominated diphenyl ethers (PBDEs), from mono- through hepta-brominated, were analyzed in river and coastal sediment samples of the eight main river basins of Portugal to investigate the occurrence, geographical distribution, and detailed congener profiles. Thirty-two sediment samples taken along the different rivers from inland to the open sea revealed an increase toward the river mouth with a total PBDE concentration of 20 ng/g-dw, and levels decreased to 0.5 ng/g-dw in coastal sediments. PBDEs were detected in all samples analyzed, indicating a diffuse source of pollution in the aquatic environments. Maximum levels were encountered in sediments collected close to urban and industrial areas. Of 40 congeners included in the analytical work, 17 congeners were detected in river sediments. BDE 47 was found in all samples analyzed whereas BDEs 100 and 99 were found in more than 26 out of 32 samples analyzed at concentrations from 0.03 to 10 ng/g-dw. This study is unique in showing the presence of previously nondescribed lower brominated PBDEs in riverine and marine sediments. BDEs 7, 11, 12+13, 15, 30, 32, 17, 25, 28+33, 49, 75, and 71 were identified in two to five samples with a median of 0.03-0.55 ng/g-dw. The analytical method developed consisted of the use of Soxhlet extraction with a novel cleanup method employing alumina cartridges and analysis by gas chromatographymass spectrometry operated in negative chemical ionization mode.
Introduction Polybromodiphenyl ethers (PBDEs) have been widely used in the past decade in many industrial applications as flame retardants (1). These compounds, used as additives in highimpact polystyrene, textile coatings, wire and cable insulation, electrical connectors, etc. are not chemically bonded to the plastic structure and are possibly more readily released to the environment. PBDEs have become ubiquitous environmental pollutants as a result of their usage, disposal of PBDEcontaining products, and distribution pattern. Ruled by their * Corresponding author phone: +34 93 4006169; fax: +34 93 2045904; e-mail:
[email protected]. † IIQAB, CSIC. ‡ Instituto do Agua. 892
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physicochemical properties, increasing levels have been reported in North America (2-4) as well as in Europe (5) and Asia (6). PBDEs behave as persistent organic pollutants and were suggested to be global environmental pollutants because of the high persistence, high bioaccumulation rates, and potential atmospheric transport (7). In addition, these compounds are suspected to cause endocrine disfunction by interfering with the thyroid hormone metabolism (8). Moreover, neurotoxic (9) and developmental effects (10) have been reported. As a result and because of the widespread use of such compounds as flame retardants, much concern is presently given to monitoring the levels of PBDEs in different environmental compartments in order to determine its environmental impact. Sediment (11) and sewage sludge (12) are considered a sink of PBDEs, and most typically BDEs 47, 99, and 100 have been detected at concentrations from 0.01 to 1000 ng/g-dw. Other works have determined the concentrations and spatial variations of PBDEs in air, indicating that PBDEs can be transported to remote areas (13). PBDE residues have been recently detected in Artic ringed seals, making the transport of some PBDE congeners evident and that such levels are increasing due to an atmospheric distillation process (14). Most work have been concentrated on the analysis of biota samples (15, 16) because of the high bioaccumulation potential of these compounds and associated risk they may pose. Reported levels vary from 0.008 to 2500 ng/g-lw in biota. Human exposure has been assessed by analyzing milk (17), and recently, it has been demonstrated that the levels of such compounds increased in archived human serum (18), threatening therefore human health (19, 20). Taking into consideration that the total world consumption of penta-, octa-, and deca-BDE was of 8500, 3825, and 54 800 t in 1999 (21), it is understandable that most works are directed to determine either the single legislated products (penta-BDE, according to the European Commission) (22) or the most abundant congeners such as BDE 209 or BDEs 47, 99, and 100 corresponding to the widely used commercial PBDE product, Bromkal 70-5DE, or other technical mixtures (23). With new analytical tools, this mixture has been extensively characterized and contained 37% of 2,2′,4,4′TeBDE (BDE 47), 35% of 2,2′,4,4′,5-PeBDE (BDE 99), and 6.8% of 2,2′,4,4′,6-PeBDE (BDE 100) while the remaining 20% was present as other homologue groups, hexa- and heptaBDE among them (24). The lack of analytical standards, because of synthetic difficulties, prevents comprehensive full congener analysis of PBDEs in environmental samples, in special of minority PBDEs for which it is not known whether they are present in the environment in significant quantities. As a result, there is a lack of the complete characterization of PBDEs starting from mono-BDE in environmental samples, and individual congener distribution pattern are needed to assess the fate of these compounds and their toxicological role in the environment. At present, mixtures of several PBDEs are available from mono- through hepta-brominated and deuterated standards, which can be used as surrogates and internal standards (25). These standard mixtures permit a much better characterization of the levels of specific congeners in environmental samples. Specifically, 13C-labeled standards are available as individual congeners or mixtures of them and are specially suitable for isotope dilution quantification in electron impact ion mode coupled to either low- (25) or high-resolution mass spectrometry (14). Using calibration standards containing 37 PBDEs and 13C-labeled PBDEs as internal and recovery standards, it was possible to characterize 37 different PBDEs in crabs, sole, and porpoise 10.1021/es020839+ CCC: $25.00
2003 American Chemical Society Published on Web 01/24/2003
in the coast of British Columbia at 4-2300 ng/g lipid, and di- to hexa-BDEs were detected. The most abundant congener was BDE 47 (found in 50% of samples), followed by BDEs 99, 100, 49, and 153 depending on the species and without a characteristic pattern. Other congeners detected were BDEs 25, 30, 32, 77, and 140 (26). Regarding sediment samples, a similar characterization has not been performed. The present work was aimed at determining 40 PBDE congeners from mono- to hepta-brominated in river and coastal sediments collected in Portugal in the context of a monitoring program directed to survey priority pollutants in water, sediments, and biota (27, 28). The sampling pattern was designed to estimate the geographical distribution of PBDEs in eight river basins, which are representative of a high level of industrial and agricultural activity. During the last two decades, industrial effluents were directly discharged untreated to the river bed. This situation has changed with the introduction and appliance of new European Union (EU) Directives, but historical contamination is expected at all sites. Congener-specific analysis has been performed to determine the most ubiquitous congeners and those detected at highest concentration. To achieve these objectives, an analytical method based on Soxhlet extraction followed by a novel cleanup method using alumina solid-phase extraction cartridges and analysis by gas chromatography-mass spectrometry operating in negative chemical ionization mode was optimized and applied for the analysis of 32 sediment samples. This paper reports the quality control/quality assurance parameters obtained with such methodology and the levels of PBDE congeners detected in Portuguese sediments and the distribution of these congeners along eight important river basins.
Experimental Section Chemicals and Reagents. The PBDE analytical standard EO4980 was purchased from Cambridge Isotope Laboratories, Inc. (MA). EO-4980 contained the following PBDE congeners: mono-BDEs 1, 2, and 3; di-BDEs 7, 8, 10, 11, 12, 13, and 15; tri-BDEs 17, 25, 28, 30, 32, 33, 35, and 37; tetra-BDEs 47, 49, 66, 71, 75, and 77; penta-BDEs 85, 99, 100, 105, 116, 119, and 126; hexa-BDEs 138, 140, 153, 154, 155, and 166; and hepta-BDEs 181, 183, and 190. The mixture also contained the following 13C-labeled congeners: tetra-[13C]-BDEs 47 and 77 and penta-[13C]-BDEs 99, 100, and 126, which were not taken into consideration in this study because these labeled congeners are only suitable for isotope dilution quantification. However, in our study low-resolution GC-EI-MS did not provide enough sensitivity for the low nanogram per gram dry weight (ng/g-dw) detection of PBDE congeners in sediments. Of 40 studied compounds, the following 17 congeners were detected above the method detection limit and are reported in this paper: BDE 7, BDE 11, BDE 12+13 (coeluting congeners), BDE 15, BDE 30, BDE 32, BDE 17, BDE 25, BDEs 28+33 (coeluting congeners), BDE 75, BDE 71, BDE 49, BDE 47, BDE 100, and BDE 99. The total PBDEs are the sum of these 17 congeners. The EO-4980 standard was used to construct a calibration curve over the range from 5 to 200 pg/µL. This calibration curve allowed quantification of congener concentrations over the range 10-400 pg/g-dw. EO-4980 was also employed to spike agricultural sediments for recovery studies following the standard addition method. Solvents used were from Merck (Darmstadt, Germany), and 2-g alumina cartridges were purchased from Waters (Milford, MA). Sampling Strategy. Selected sampling points chosen covered the main river basins of Portugal and corresponding coastal areas (42° N, 7° W to 37° N, 7°5′ W). These rivers are, from north to south, river Minho (flow of 300 m3/s), Douro (450 m3/s), Vouga (70 m3/s), Mondego (80 m3/s), Tejo (400
FIGURE 1. Map showing the eight river basins studied and corresponding sampling sites. m3/s), Guadiana (80 m3/s), Sado (40 m3/s), and Formosa (70 m3/s), and all discharge their waters to the Atlantic Ocean. Figure 1 shows a map of Portugal and the eight rivers monitored, indicating each sampling point in each river. Minho, Douro, Tejo, and Guadiana Rivers are transboundary rivers that spring in Spain and flow through highly agricultural areas until reaching the lower part of the river where urban and industrial activities are located. The other rivers have smaller flows and are a maximum of 150 km long; their waters are mainly used for irrigation, although in some points metallurgy, paper, and textile industries have spilled during some time their water to these rivers. Coastal sediment samples were collected from the river bed using a drag SmithMcIntyre with a midicorer Mark II-400. For river sampling, a Petit-ponar drag was used. The drag was opened on top of aluminum foil, and the upper surface was inserted in a previously cleaned Pyrex glass container. In such a way, the external layers (0-2 cm) were not altered. Samples were kept at 4 °C until transported to the laboratory. These same containers were used thereafter for lyophilizing the sample. Sample Preparation. Samples were stored at -18 °C and lyophilized at -50 °C during 36 h. Prior to analysis, samples were sieved through 250-, 100-, and 50-µm sieves in order to obtain a homogeneous material by way of particulate size. The total organic content (TOC) on a dry basis of these samples was between 0.49 and 6.25 mg/g. Prior to extraction, 1 g of sample was spiked with PCB 209 as a surrogate standard, which was only used for quality control of the analytical procedure. Samples were Soxhlet extracted in hexane: CH2Cl2 (1:1) for 18 h. Sulfur was removed by adding copper powder during extraction. The extract was rotaevaporated nearly to dryness, and sample cleanup was performed with 2-g alumina cartridges. Cartridges were placed on a Baker VOL. 37, NO. 5, 2003 / ENVIRONMENTAL SCIENCE & TECHNOLOGY
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FIGURE 2. GC-NCI-MS selected ion monitoring chromatogram of a sediment sample spiked with 40 individual PBDE congeners at concentrations between 2.5 and 10 ng/g-dw. Compound identification numbers as follows: 1 ) BDE; 2 ) BDE2; 3 ) BDE3; 4 ) BDE10; 5 ) BDE7; 6 ) BDE11; 7 ) BDE8; 8,9 ) BDE12+13; 10 ) BDE15; 11 ) BDE30; 12 ) BDE32; 13 ) BDE17; 14 ) BDE25; 15,16 ) BDE28+33; 17 ) BDE35; 18 ) BDE37; 19 ) BDE75; 20 ) BDE71; 21 ) BDE49; 22 ) BDE47; 23 ) BDE66; 24 ) BDE77; 25 ) BDE100; 26 ) BDE119; 27 ) BDE99; 28 ) BDE116; 29 ) BDE85; 30,31 ) BDE126+155; 32 ) BDE105; 33 ) BDE154; 34 ) BDE153; 35 ) BDE140; 36 ) BDE138; 37 ) BDE166; 38 ) BDE183; 39 ) BDE181; 40 ) BDE190. SPE 12G apparatus (Deventer, The Netherlands) connected to a vacuum system. Prior to cleanup, the cartridges were conditioned with hexane and dichloromethane (19:1). Afterward, 1 mL of sample extract was placed on the top of the cartridge and eluted by gravity with 20 mL of hexane:CH2Cl2 (19:1), 20 mL of hexane:CH2Cl2 (1:1), and 20 mL of CH2Cl2: methanol (1:1). Fractions 1 and 2 were mixed, and fraction 3 was disregarded since no traces of any PBDEs were present. After combining fractions 1 and 2, the extract was rotaevaporated to almost dryness and reconstitued in 200 µL of isooctane. Recovery studies were performed by spiking 1 g of sediment with a mixture of all 40 BDE congeners at concentration levels between 2.5 and 10 ng/g-dw. Extraction was performed as depicted above. GC-NCI-MS Analysis. GC-NCI-MS was performed on an Agilent 6890 gas chromatograph connected to an Agilent 5973 Network (Agilent, Waldbronn, Germany) mass spectrometer. A HP-5ms (30 m × 0.25 mm i.d., 0.25 µm film thickness) containing 5% phenyl methyl siloxane (model HP 19091S-433) capillary column was used with helium as the carrier gas at 10 psi. The temperature program was from 110 °C (held for 1 min) to 180 °C (held for 1 min) at 8 °C/min, then from 180 to 240 °C (held for 5 min) at 2 °C/min, and then from 240 to 280 °C (held for 6 min) at 2 °C/min. A total of 2 µL of the sample was injected using the splitless injection mode over an interval of 1 min. The GC-NCI-MS operating conditions were as follows: the ion source temperature was 250 °C, methane was used as the chemical ionization moderating gas at an ion source pressure of 2.7 10-4 Torr, and acquisition was performed in selected ion monitoring as described elsewhere (21). A quadrupole mass analyzer with unit resolution was used. With GC-NCI-MS, the target compounds were easily distinguishable, and retention time and spectral information provided confirmation of such results. Quantification and Validation. Quantification was performed by external standard calibration, and results were 894
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corrected by the recovery factor. Recovery values, standard deviations (n ) 3), and method detection limits using a signalto-noise ratio of 3 were calculated for each congener. In addition and to validate the analytical methodology, a certified standard solution and a sediment extract provided by Quasimeme (Aberdeen, U.K.) was analyzed using the above-mentioned analytical methodology. A good agreement was observed between our results (BDEs 28, 47, 99, 100, 153, 154, and 183) and the real concentrations (29).
Results and Discussion Chemical Analysis. GC-NCI-MS as used in the present study provided the low-level determination of 40 individual PBDEs congeners from mono- through hepta-brominated as illustrated in Figure 2, which shows a chromatogram of a spiked sediment sample at levels of 2.5-10 ng/g-dw. BDE 209 was not analyzed since it involves a different methodological approach. In this work, emphasis was given to the detection of the less prevalent PBDE congeners for which an extraction method and analysis in sediment samples has not been previously described. Extraction was performed using the classical Soxhlet method, which is especially suitable and widely applied to determine brominated flame retardants in environmental matrixes comprising sediment and biota samples, as indicated in a recent review (30). However, selectivity was enhanced by the optimization of a simplified cleanup method consisting of the use of solid-phase extraction cartridges packed with alumina, which provided elimination of interferences without affecting the recovery of target analytes. The alumina cartridges possess the advantages of simple and efficient handling and disposal, lack of glassware cleaning requirements, and no need of activation/deactivation procedure (e.g., by drying alumina at 300 °C and adding a fix amount of water, e.g., 1%). Recoveries between 74 and 120% were obtained for the majority of the congeners, with the exception of the three mono-BDE congeners, which had recoveries from 49 to 59% because of the fact that the vapor
TABLE 1. Sediment Concentration of Detected PBDEs in ng/g Dry Weight PBDE no. river
7
11
12+13
15
30
32
17
25
28+33
75
71
49
47
100
99
bdla
Minho 1 (M1) Minho 2 (M2) Minho 3 (M3) Minho coast (Mc)
bdl bdl bdl
bdl bdl bdl bdl
bdl 0.31 bdl bdl
bdl bdl bdl bdl
bdl bdl 0.15 bdl
bdl bdl bdl bdl
bdl bdl bdl bdl
bdl bdl 0.04 bdl
bdl bdl bdl bdl
bdl bdl 1.36 bdl
bdl bdl 0.13 bdl
bdl bdl bdl bdl
0.55 0.63 1.71 0.03
0.22 0.17 0.55 0.15
0.45 0.21 0.89 0.16
Douro 1 (D1) Douro 2 (D2) Douro 3 (D3) Douro coast (Dc)
bdl bdl bdl bdl
bdl bdl bdl bdl
bdl bdl bdl bdl
bdl bdl bdl bdl
bdl bdl bdl bdl
bdl bdl bdl bdl
bdl bdl 0.15 bdl
bdl bdl bdl bdl
0.11 bdl 0.11 bdl
bdl bdl bdl bdl
0.06 bdl 0.08 bdl
bdl bdl bdl bdl
1.65 0.57 1.20 0.06
0.55 0.25 0.32 0.15
1.64 0.68 0.90 0.16
Vouga 1 (V1) Vouga coast (Vc)
bdl bdl
bdl bdl
bdl bdl
bdl bdl
bdl bdl
bdl bdl
bdl bdl
bdl bdl
bdl 0.07
bdl bdl
bdl bdl
bdl bdl
0.96 0.56
0.25 0.21
0.57 0.48
Mondego 1 (M1) Mondego 2 (M2) Mondego 3b (M3) Mondego coast (Mc)
bdl bdl bdl bdl
bdl bdl bdl bdl
bdl bdl bdl bdl
bdl bdl bdl bdl
bdl bdl bdl bdl
bdl bdl bdl bdl
bdl bdl 0.15 bdl
bdl bdl bdl bdl
bdl bdl 0.18 bdl
bdl bdl bdl bdl
bdl bdl 0.15 bdl
bdl bdl bdl bdl
0.40 0.49 2.74 0.04
bdl 0.20 0.59 0.15
0.56 0.33 2.28 0.16
Tejo 1 (T1) Tejo 2 (T2) Tejo 3 (T3) Tejo 4 (T4) Tejo 5 (T5) Tejo 6 (T6) Tejo 7 (T7) Tejo estuary (Te) Tejo coast (Tc)
bdl bdl bdl bdl bdl bdl bdl bdl bdl
bdl bdl bdl bdl bdl bdl bdl bdl bdl
bdl bdl bdl bdl 0.15 bdl bdl bdl bdl
bdl bdl bdl bdl 0.29 bdl 0.25 bdl bdl
bdl bdl bdl bdl bdl bdl bdl bdl bdl
bdl bdl bdl bdl bdl bdl bdl bdl bdl
bdl bdl bdl bdl bdl bdl bdl bdl bdl
bdl bdl bdl bdl bdl bdl bdl bdl bdl
0.07 bdl bdl bdl bdl bdl bdl bdl bdl
bdl bdl bdl bdl bdl 0.23 0.23 bdl bdl
bdl bdl bdl bdl bdl bdl 17.68 bdl bdl
bdl bdl bdl bdl bdl bdl bdl bdl bdl
0.69 0.04 0.39 0.48 0.58 0.63 2.38 0.05 0.45
0.31 bdl bdl 0.21 0.22 bdl 0.22 0.15 0.16
0.94 0.16 0.30 0.33 0.39 0.36 0.33 0.16 0.29
Guadiana 1 (G1) Guadiana 2 (G2) Guadiana 3 (G3) Guadiana coast (Gc)
bdl bdl bdl bdl
bdl bdl bdl bdl
bdl bdl bdl bdl
bdl bdl bdl bdl
bdl bdl bdl bdl
bdl bdl bdl bdl
bdl 0.16 bdl bdl
bdl 0.02 bdl bdl
bdl 0.19 bdl bdl
bdl bdl bdl bdl
bdl 0.28 bdl bdl
bdl bdl bdl bdl
2.57 9.91 0.79 0.04
bdl 0.57 0.20 0.15
bdl 1.35 0.67 0.16
Sado (S1) Sado estuary (Se) Sado coast 1 (Sc1) Sado coast 2 (Sc2)
bdl bdl bdl 0.05
bdl bdl bdl 0.01
bdl bdl 0.26 bdl
bdl bdl bdl bdl
bdl bdl 0.16 0.01
bdl 0.13 bdl bdl
bdl bdl bdl bdl
bdl bdl bdl bdl
bdl bdl bdl bdl
bdl bdl bdl 0.04
bdl bdl 0.06 bdl
bdl bdl 0.25 bdl
0.03 0.78 0.54 0.10
bdl 0.35 0.24 0.16
bdl 0.42 0.39 0.18
Formosa
0.08
0.01
bdl
bdl
bdl
bdl
bdl
bdl
bdl
bdl
bdl
bdl
0.04
0.15
0.16
a
bdl, below detection limit.
b
This sample corresponds to an effluent of the river Mondego.
pressure of these compounds is highest among the mixture (31). This may induce losses of mono-BDE during the extraction and concentration procedure. Method detection limits obtained with GC-NCI-MS in selected ion monitoring were in the range of 7-171 pg/g-dw, being the highest values for mono-BDE. By performing triplicate analysis, the coefficient of variation was around 7%, except coeluting compounds (BDEs 126 and 155) and hepta-BDE that had maximum variation of 13%, indicating an overall good performance of the method. For all samples, the ion at m/z 79/81 was the base peak for all congeners. To unequivocally confirm the presence of a PBDE congener, three less prominent ions formed during GC-NCI-MS, normally corresponding to loss of a bromine atom or to [M-HBrx]-, were selected by compound, and their relative intensities should be within 10% of the corresponding standard. In addition, the retention times could not vary more than 0.1 min of their theoretical value. The base peak at m/z 79 was chosen for quantification. PCB 209 was used as surrogate for quality control of the whole procedure but could not be used for quantification because of a high dispersion of the response factors detected for the different bromination degree. Therefore quantification was performed by external standard with recovery correction. Method validation was performed by analyzing a certified standard and sediment extract from a Quasimeme interlaboratory exercise, which was organized at European level. For the standard solution, the concentrations level were between 97 and 570 µg/kg; for all congeners, a mean error of 15% was performed by our laboratory. For sediment extracts, with an assigned value of between 0.8 and 19 ng/
g-dw, a mean error of 17% was performed. These results validate our method of analysis. Environmental Levels. Successful method development allowed the determination of individual PBDE congeners in river and coastal sediments from different parts over Portugal at the 0.03-18 ng/g-dw level. Table 1 indicates the specific sampling sites and concentration of each PBDE congener. Out of 32 samples analyzed, all of them contained at least one PBDE, indicating that these pollutants have reached river sediments in places where there is or has been an important industrial activity. Of 40 PBDEs analyzed, 17 were found in sediment samples. Figure 3 shows a boxplot indicating the BDE detected, the number of positive samples, the maximum and minimum concentration, and the median. The most common BDE detected were BDEs 47, 99, and 100, which were present in almost all samples analyzed at concentrations varying from 0.4 to 18 ng/g-dw with a median value of 0.55, 0.21, and 0.37 ng/g-dw, respectively. In these compilations, analytes with concentration below the LOD were omitted. These levels are in accordance to previous studies, where PBDEs were determined in Swedish river sediments at 8-50 ng/g-dw (32) and at 0.52 ng/g-dw in the upper layer of a sediment core collected in the Baltic Sea (33). Higher levels in sediments up to 1400 ng/g-dw were found in a downstream area of a manufacturing plant in United Kingdom (34) and at 120 ng/g-dw downstream of an area with textile industries (35). In all these cases, BDEs 47 and 99 were the dominant congeners and were found in equal concentrations. In the present work, these two congeners along with BDE 100 were also found at mean concentrations between 0.53 and 1 ng/ g-dw, and their concentrations did not vary significantly along VOL. 37, NO. 5, 2003 / ENVIRONMENTAL SCIENCE & TECHNOLOGY
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FIGURE 3. Boxplot indicating the PBDE congeners detected, the number of positive samples (boxes) out of 32 analyzed, the maximum and minimum concentration, and the median in ng/g-dw (lines).
FIGURE 4. Total concentration of detected BDE from north to south of Portugal, indicating the river basin from which samples were obtained. any of the rivers monitored, indicating that the levels encountered are due to diffuse pollution generated over the years. However, in all sampled basins monitored, the concentrations of these congeners increased through their way to industrial and urban areas, e.g., higher levels in sediments from the Douro River on its way through the city of Porto with 1.7 million inhabitants or the Tejo River through its way through Lisbon (2.1 million inhabitants). BDEs 17, 28+33, and 71 were found in more than 5 samples out of the 32 analyzed with a median of 0.19, 0.11, and 0.14 ng/g-dw, respectively; BDE 71 was detected with concentrations up to 17.6 ng/g-dw for one sample collected at the Tejo River mouth, in the city of Lisbon, which is characterized by important industrial activities mainly related to textile, metal, and paper production from eucalyptus wood. These congeners are not present in technical formulations. BDE congeners detected in 1-5 samples were BDEs 7, 11, 12+13, 15, 30, 32, 75, and 49 at concentrations from 0.03 to 1.7 ng/ g-dw (Table 1). Only lower brominated BDEs 28 and 17 have been previously reported in crab samples (26) and in air (39) whereas serum contained only trace levels of BDE 28 (14). Hexa-BDEs 153 and 154 and hepta-BDE 183, although present in 5, 2.5, and 44% of the technical penta-BDE and octa-BDE products, respectively, were not found in these river sediments unlike previous studies that detected these congeners 896
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in a fjord in Norway, in a lake, or in the Wadden Sea in The Netherlands (21). The difference may be explained by the fact that the sediment samples in this study correspond to rivers with a considerable flow (from 40 to 500 m3/s) rather than enclosed environments. Mobility of some congeners can be expected, including possible debromination, although the elimination/transformation rate cannot still be predicted. The origin of tri- and tetra-brominated BDEs may be due to some transformation and decomposition under the environment conditions. The presence of some naturally occurring PBDEs has been attributed to spongi, but in our study, no spongi were present in our sampling locations. Previous laboratory studies indicate that deca-BDE is debrominated by sunlight and UV light to lower brominated PBDEs (36, 37). The identification of resultant BDEs in environmental or mesocosm conditions to test this hypothesis has not been performed. Another explanation would be metabolism via reductive debromination process to generate lower brominated BDEs (38), which could then be available to the particulate phase and deposition to sediment. Figure 4 shows the change in total PBDE concentrations moving downstream along the eight most important river basins in Portugal according to their flow rates and drainage areas. From each river, sampling points are grouped from furthest (200 km inland) to nearest to the river mouth (Figure 1). A
FIGURE 5. Concentration (in ng/g-dw) of di-, tri-, tetra-, and penta-BDE by homologue grouping in sediment samples collected along the Douro, Mondego, Tejo, and Guadiana River basins. similar trend is observed in all basins, where the initial point has a concentration between 1 and 3 ng/g-dw, and increases as the river passes a urban/industrial site (e.g., Porto with river Douro, Monte Real with river Mondego, and Lisbon with river Tejo) and decreases again as the river discharges its waters to the estuary and finally to the sea. The river with highest total amount of BDE was the Tejo river, where the sediments collected just in the river discharge had a total amount of 21.09 ng/g-dw but the sample collected at the exit of the estuary the concentration decreased to 0.36 ng/g-dw, indicating that sediment transport and diffusion of PBDEs toward the open sea (50-100 km) offshore takes place at very slow rate and that dilution is the main process that explained the low concentrations encountered. The Atlantic Ocean, in this area, is characterized by strong currents along the coast. This similar trend was observed in the other river basins. In the Douro River basin, the total PBDE concentration was from 3 to 5 ng/g-dw all through the river, even at its point through the industrial city of Porto, probably because of pollution coming from industrial activities along its flow. North from Porto, in river Minho, the total concentration was similar to that found in Douro, of 5 ng/g-dw upstream and at the river mouth, whereas in the open coast, PBDEs were detected at very low concentration. Another river basin with levels of total PBDEs around 5 ng/g-dw was river Vouga and river Mondego (north from Lisbon, in Monte Real). In river Vouga, levels varied from 1 to 3 ng/g-dw, similar to Mondego river, except to its way through Monte Real, which is characterized by metal industry, where levels of 5 ng/g-dw (Mondego 1) were encountered. In all river basins studied, the total PBDE concentration was around 1 ng/g in marine sediments, and only PBDEs 47, 99, and 100 were encountered and at lower concentration, in contrast to higher levels encountered in river sediments that also contained other lighter PBDE congeners. This means that although river sediments deposit along estuaries and to the open sea, there is a gradient dilution that is reflected by lower levels of PBDE congeners. Figure 5 shows the specific BDE distribution in samples collected in the Douro, Mondego, Tejo, and Guadiana River basins. Tetra-BDE (75, 71, and 47) and penta-BDE (100 and 99) were the compounds found at highest concentrations. In all river samples, those sediments that had the highest levels of tetra- and penta-BDEs contained also tri-BDEs (30,
32, 17, 25, and 28+33). In the Tejo River basin, di-BDEs were also encountered (7, 11, 12+13, and 15). Different homologuespecific profiles were found in each river basin where the concentration of each homologue group varied according to the distance to the river mouth. In general, coastal sediments had a higher contribution of penta-BDE, except for the river Tejo, where the levels in general were higher than in the other rivers. The suggestion that lower brominated PBDEs congeners can be found in river sediments has an implication on how analytical methods should be designed. The presence of these PBDEs reveals the importance of their inclusion in analytical methods in order to perform a complete environmental survey. The inclusion of a large number of congeners in the analytical method can be easily achieved as suggested in this study and improves to a large extent our knowledge of the specific PBDE congener compositions in environmental samples. In this study, the total PBDEs load increased along all studied river basins toward the river mouth, with maximum concentration as the river passes through big cities, point to populated and industrialized regions as the source of PBDEs in the environment. The identification of which specific congeners contribute to the total PBDEs load will improve risk assessment. In addition, the presence of lower brominated PBDEs in the environment indicate that effort should be directed to study possible environmental transformation of higher brominated congeners. This will improve the existing knowledge on the persistence, degradation, and fate of these chemicals in the environment. The method presented here has been validated by participating in an interlaboratory exercise where PBDEs were analyzed in sediment extracts.
Acknowledgments This work has been financed by the Instituto do Ambiente of Portugal (Ministry of Environment). Roser Chaler and Dori Fanjul are thanked for GC-MS assistance. One of the reviewers is acknowledged for helpful discussions to improve the quality of the paper.
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Received for review July 16, 2002. Revised manuscript received November 20, 2002. Accepted December 2, 2002. ES020839+
