Environ. Sci. Technol. 2007, 41, 2249-2254
Isomers of Dechlorane Plus in Lake Winnipeg and Lake Ontario Food Webs G R E G G T . T O M Y , * ,†,‡ K E R R I P L E S K A C H , † NARGIS ISMAIL,† D. MICHAEL WHITTLE,⊥ PAUL A. HELM,§ ED SVERKO,| DONNA ZARUK,| AND CHRIS H. MARVIN| Department of Fisheries and Oceans, Winnipeg, Manitoba, R3T 2N6 Canada, Department of Chemistry, University of Manitoba, Winnipeg, Manitoba, R3T 2N2 Canada, Department of Fisheries and Oceans, Great Lakes Laboratory for Fisheries Aquatic and Sciences, Burlington, Ontario, L7R 4A6, Canada, Ontario Ministry of the Environment, Toronto, Ontario, M9P 3V6 Canada, and Environment Canada, National Water Research Institute, Burlington, Ontario, L7R 4A6 Canada
The extent of bioaccumulation of the syn- and antiisomers of Dechlorane Plus (DP) is assessed in archived food web samples from Lake Winnipeg and Lake Ontario. Concentrations of the isomers were determined using purified analytical solutions of individual isomers as opposed to the technical mixture. The syn-isomer was consistently detected in all samples from both lakes; the anti-isomer was detected in all Lake Ontario samples, but only 45% of the samples from Lake Winnipeg. The pattern of bioaccumulation was different for the isomers in Lake Winnipeg. The anti-isomer was dominant in higher trophic level (TL) organisms like walleye [arithmetic mean ( 1 × standard error: 730 ( 120 pg/g, lipid weight (lw)] and goldeye (760 ( 170 pg/g, lw) while the syn-isomer dominated the lower TL organisms like zooplankton (550 ( 40 pg/g, lw) and mussels (430 ( 140 pg/g, lw). In Lake Ontario, the extent of bioaccumulation of the isomers and concentrations was greatest in the lower TL benthic organism, Diporeia (syn, 1307 ( 554; and anti, 3108 ( 898 pg/g lw) and also high in zooplankton (syn, 719; and anti, 1332 pg/g lw). This suggests that the isomers are bioavailable in sediment and that, despite their molecular size, diffusion from the water column into zooplankton can occur. Differences in the mean fractional abundance of the anti-isomer (mean fanti ) mean concentration of the anti-isomer divided by sum of mean syn- and anti-concentrations) were pronounced in sediments between lakes (Lake Winnipeg mean fanti ) 0.610, Lake Ontario mean fanti ) 0.860) and the extent of enrichment (anti-) and depletion (syn-) of the isomers were more marked in Lake Winnipeg biota. There were also differences in the biomagnification potentials, as measured by the trophic magnification factor (TMF), between the isomers in the Lake Winnipeg food web; no statistically significant TMFs for either isomer were found for the * Corresponding author phone: 204-983-5167; fax: 204-984-2403; e-mail:
[email protected]. † Department of Fisheries and Oceans. ‡ University of Manitoba. ⊥ Great Lakes Laboratory for Fisheries and Aquatic Sciences. § Ontario Ministry of the Environment. | Environment Canada. 10.1021/es062781v CCC: $37.00 Published on Web 03/03/2007
2007 American Chemical Society
Lake Ontario food web. A TMF of 2.5 (r 2 ) 0.12, p ) 0.04) for the anti isomer and 95%), brominated diphenyl ether congeners (BDE) 71, 126, 156, 197, and 207, chlorinated diphenyl congener 99 (CDE-99) and the mass labeled HBCD isomers (13C and d18-γ) were supplied by Wellington Laboratories (Guelph, ON, Canada). Sample Information. Detailed sample information can be found in Law et al. and Tomy et al. (2, 3). Samples for both studies were collected between 2000 and 2003. Additional sediment samples from the central basin of Lake Ontario collected by Environment Canada (EC) in 1998 were also analyzed. All samples were processed at the Freshwater Institute (FWI) laboratory. Biological samples were homogenized with dry ice, spiked with a suite of recovery internal standards, and extracted using accelerated solvent extraction VOL. 41, NO. 7, 2007 / ENVIRONMENTAL SCIENCE & TECHNOLOGY
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(ASE), lipid removal by gel permeation chromatography (GPC), and further cleanup using Florisil. Sediment samples were first freeze-dried and extracted in a manner identical to that of biota with the exception of GPC. Stable isotope analysis of nitrogen was previously determined on biota to define trophic levels (TL). Gas Chromatography/Mass Spectrometric Analysis. Lake Winnipeg and Lake Ontario extracts were analyzed at FWI and EC, respectively. Both laboratories employed identical methodologies: analyses were performed on Agilent 5973 GC-mass selective detectors (Mississauga, ON, Canada) fitted with a 10 m DB-5 capillary column (0.25 µm film thickness × 0.25 mm i.d; J&W Scientific, Folsom, CA). Splitless injections of 2 µL were made onto an injector set isothermally at 280 °C. The initial oven temperature was set at 90 °C with no hold time, ramped at 20 °C/min to 310 °C, and held for 5 min. The MS analysis was performed in the electron capture negative ion mode using methane as the buffer gas. Source and quadrupole temperatures were both set to 150 °C. The dominant peak in the molecular ion cluster of the two isomers (m/z 651.8; spectra were identical) was used for quantitation while the second most abundant peak (m/z 653.8) was used for confirmation. The retention time for the syn- and antiisomers was 11.17 and 11.42 min, respectively. Extraction efficiencies of the BDE congeners 71, 126, 197, and 207 were measured using the [Br]- ions (m/z 79 and 81) while that of the CDE-99 congener was done using the [Cl]- ions (m/z 35 and 37). Quality Control. The extracts employed in this study were those previously used for our work on BFRs in both lakes. In those studies, chlorinated diphenyl ethers (CDEs) and mass labeled hexabromocyclododecane (HBCD) isomers were used as recovery internal standards. To test if BFRs are extracted in a manner similar to that of the DP isomers, a controlled experiment was conducted whereby a suite of BDE isomers, including 71, 126, 197, and 207, CDE-99, and 13C-γ-HBCD, along with the syn- and anti-isomers (using the technical product) were spiked into an ASE cell containing hydromatrix (baked for 6 h at 600 °C) at an elevated (200 pg, n ) 6) and lower (50 pg, n ) 6) dose. The spiked ASE cells were immediately extracted under conditions identical to those reported previously (2, 3). Extracts were then further processed through the GPC and adsorption chromatography cleanup steps followed by the addition of an instrument performance internal standard (IPIS), BDE-156, and injected onto the GC/MS; for HBCD analysis the d18-γ-HBCD was added as an IPIS and analysis was based on liquid chromatography tandem mass spectrometry as described in Tomy et al. (4). Mean recoveries of the four BDE recovery standards in the low dose range were 93.5 ( 6.8% (mean ( 1 × standard error), CDE-99 was 95.1 ( 8.5%, 13C-γ-HBCD was 89.6 ( 7.9%, and DP-isomers were 76.4 ( 3.4%, while in the elevated dose respective mean recoveries of the four BDEs, CDE-99, 13 C-γ-HBCD, and DP were 90.3 ( 1.9, 98.2 ( 6.5, 96.5 ( 6.4, and 102.1 ( 3.8%. One-way ANOVA testing indicated that there was no difference between the recoveries of the BFRs or DP isomers at either treatment level. Therefore, these results suggest that it would be suitable to use the recoveries of the internal standards analyzed previously to correct our DP concentrations. However, because recoveries of CDEs in the Lake Winnipeg and 13C2-labeled HBCD in the Lake Ontario samples were consistent in the sample extracts and greater than 82% no recovery correction was applied to the data. Duplicates of sculpin from Lake Ontario, extracted separately and analyzed to check for repeatability, were within 94% of each other for both isomers suggesting good repeatability. An interlaboratory comparison (EC and FWI) on the technical mixture gave excellent agreement: the respective contributions of the syn- and anti-isomers in the mixture were estimated to be 36 and 64% by EC laboratory and 34 2250
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TABLE 1. Interlaboratory Comparison of Measurements Made by FWI and EC on Four Sediment Samples from Lake Winnipeg and on the Technical Mixturea Syn-isomer
Anti-isomer
sediment
EC
FWI
EC
FWI
1 2 3 4 technical mixture (%)
289 361 288 227 0.36
408 526 336 360 0.34
372 610 545 448 0.64
444 822 652 617 0.66
a Samples were extracted at FWI and the same extracts were analyzed in each laboratory. Quantitation was based on an external standard solution prepared using the individual isomers. Values for sediment are given as total pg per sample while the technical mixture is presented as the fraction of each isomer contributing to the total.
and 66% by FWI laboratory (Table 1). Four sediment extracts were also analyzed in both laboratories and showed good agreement (63 to 86%) between the measured DP isomer values and suggested good precision between laboratories. Method detection limits (MDLs) were estimated from the procedural blanks which consisted of Ottawa sand. Trace amounts of both isomers (syn, 0.6 pg; anti, 2.6 pg) were present in the blanks. Using an average sample mass of 15 g, MDLs of 0.3 and 1.5 pg/g for syn- and anti-isomers, respectively, were determined. The linear dynamic range of the instruments was 10-2500 pg on column (r 2 > 0.995) for both isomers. The ratio of the quantitation and confirmation ions in samples was within 15% of measured standard values in all cases. Statistical Analysis. Statistical treatment of the data was done using SigmaStat (Version 9.01, Systat Software Inc.).
Results and Discussion Lake Winnipeg. Concentrations of DP isomers in the Lake Winnipeg food web are given in Table 2. The syn-isomer was consistently detected in all samples while the anti-isomer was less frequently detected (∼ 45% of samples). In biota, concentrations of the syn-isomer were greatest in burbot (range, 67-773 pg/g, lw; median, 415 pg/g), zooplankton (range, 469-647 pg/g lw; median, 542 pg/g), and mussels (range, 76-823 pg/g lw; median, 504 pg/g), while the antiisomer was greatest in walleye (range, 608-883 pg/g lw; median, 714 pg/g) and goldeye (range, 594-932 pg/g lw; median, 763 pg/g). Concentrations of both isomers were similar in whitefish but varied considerably in walleye and goldeye; respective concentrations of the anti-isomer were 25 and 14 times greater than that of the syn-isomer in these species. Sediments contained small pg/g (dry weight) concentrations (syn, 11.7 pg/g; anti, 18.3 pg/g dry wt) of both isomers. Lake Ontario. Concentrations of the isomers in the Lake Ontario food web are given in Table 3. Both isomers were detected in all samples with anti-DP consistently greater than that of the syn isomer. Similar concentrations of both isomers were observed in trout (median, syn ) 44.3, anti ) 47.2 pg/g lw), smelt (median, syn ) 5.5, anti ) 6.5 pg/g lw), alewife (median, syn ) 48.3, anti ) 54.2 pg/g lw) and sculpin (median, syn ) 626, anti ) 777 pg/g lw). Concentrations of the antiisomer were approximately 2.5 times greater than the synisomer in Diporeia, 3 times greater in Mysis, and 2 times greater in plankton. In sediments, the anti-isomer comprised ∼85% of the total DP concentrations (mean ∑DP ) 206 ng/g dry wt), which were orders of magnitude greater than those from Lake Winnipeg. Concentrations of BFRs determined in our other studies on the same samples are presented along with the DP concentration data in Tables 2 and 3. In general, ∑DP
TABLE 2. Concentrations [Arithmetic Mean ( 1 × Standard Error (SE)] of Syn- and Anti-DP Isomers in Fish (pg/g, Lipid Adjusted and Blank Corrected) and Sediment (pg/g, dry wt) from the South Basin of Lake Winnipeg (For Comparison, Concentrations (pg/g, lw for Biota and pg/g, dry wt for Sediment) of Other Contaminants are Also Given) sample walleye (n ) 5) burbot (n ) 5) emerald shiner (n ) 5) whitefish (n ) 5) white sucker (n ) 5) goldeye (n ) 5) zooplankton (n ) 5) mussels (n ) 5) sediment (n ) 4)
BFRsb
DP isomers
δ15N (mean ( 1SE)
TL (mean ( 1SE)
mean % lipid
syn-
anti-
fantia
∑PBDEs
∑HBCD
BTBPE
17.8 ( 0.3 16.6 ( 1.6 16.0 ( 0.1 12.0 ( 0.2 15.2 ( 0.6 16.1 ( 0.2 9.7 ( 1.1 9.5 ( 0.6
2.39 ( 0.07 2.09 ( 0.37 1.92 ( 0.03 0.87 ( 0.05 1.72 ( 0.16 1.95 ( 0.06 1 0.21 ( 0.15
1.15 0.33 3.18 8.78 2.27 2.34 13.67 0.32
29 ( 21 450 ( 120 35 ( 16 30 ( 11 37 ( 1 56 ( 3 550 ( 40 430 ( 140 11.7 ( 1.1
730 ( 120
