Environ. Sci. Technol. 1988, 22, 1071-1079
(42) NRCC Chlordane: I t s Effects on Canadian Ecosystems
and Its Chemistry;NRCC No. 14094;Associate Committee on Scientific Criteria for Environmental Quality, National Research Council of Canada: Ottawa, Ontario, 1974; 189 PP.
(43)
Prevett, J. P.; Kolenosky, G. B. Nut. Can. (Rev. Ecol. Syst.), 1982, 109,933-939.
Received for reuiew February 9, 1987. Revised manuscript received September 24, 1987. Accepted March 29, 1988.
Organochlorine Contaminants in Arctic Marine Food Chains: Accumulation of Specific Polychlorinated Biphenyls and Chlordane-Related Compounds Derek C. G. Mulr,*,+ Ross J. Norstrom,t and Mary Simon$ Department of Fisheries and Oceans, 50 1 University Crescent, Winnipeg, Manitoba R3T 2N6, Canada, and Environment Canada, Canadian Wildlife Service, Ottawa, Ontario K1A OH3, Canada ~
~~~
Polychlorinated biphenyl congeners (S-PCB) and chlordane-related compounds (S-CHLOR) as well as DDT, hexachlorocyclohexane, toxaphene, and chlorobenzenes were determined in pooled arctic cod (Boreogadus saida) muscle and polar bear (Ursus maritimus) fat and in the blubber and liver of 59 ringed seals (Phoca hispida) from the east-central Canadian Arctic. S-PCB concentrations ranged from 0.0037 mg/kg (wet wt) in cod muscle to 0.68 mg/kg in male seal blubber and 4.50 mg/kg in bear fat. Tri- and tetrachloro PCB homologues were the dominant PCBs in fish, while pentachloro/hexachloro and hexachloro/heptachloro congeners predominated in ringed seal blubber and polar bear fat, respectively. Chlordane compounds detected in seal blubber were oxychlordane, cisand trans-nonachlor, and cis-chlordane as well as nine minor components of technical chlordane, including nonachlor-I11 (a nonachlor isomer). Toxaphene and HCH isomers were the major organochlorines in cod muscle with mean concentrations of 0.018 and 0.010 mg/kg, respectively. S-CHLOR/S-PCB ratios ranged from 0.6 in fish muscle and bear fat to 0.7-0.9 in seal blubber, much higher than observed in more southerly marine environments, suggesting a proportionally greater input of chlordane into the Arctic. Introduction The presence of chlorinated hydrocarbons in marine mammals and fish of the Canadian arctic archipelago and Greenland has been documented in several surveys carried out over the past 15 years (1-5). This study focuses on trophic transfer of specific organochlorine isomers in the arctic marine food chain. Arctic cod (Boreogadus saida), ringed seal (Phoca hispida), and polar bear (Urus maritimus) are important components of the marine food chain in the east/central Canadian arctic archipelago (6, 7). Arctic cod are the only relatively abundant marine fish in many arctic areas (8). They are a small (C300 mm), short-lived (C5-6 years) pelagic fish inhabiting under-ice surfaces. The diet of arctic cod is dominated by copepods (primarily calanoids) and amphipods (primarily small Parathemisto spp.) (8,9). Ringed seal is the most common seal in the Canadian Arctic. They inhabit mainly land-fast ice and are thought to be relatively sedentary although immature animals may migrate long distances on a seasonal basis (7, IO). Adult ringed seals are opportunistic feeders, but their diet is thought to consist primarily of arctic cod during ice-covered conditions (9, 11). Amphipods, primarily Parathemisto, are important dietary components, especially for immature seals ( 9 , I l ) . Thus, seals Department of Fisheries and Oceans.
* Environment Canada.
Published 1988 by the American Chemical Society
and cod may occasionally feed at the same trophic level. The diet of polar bears in the central and eastern Canadian Arctic consists largely of the skin and blubber of immature ringed seals (7). DDT and PCBs are the only organochlorines that have been monitored on a systematic basis in arctic marine mammal tissues (12). Levels in ringed seal blubber were relatively similar over a wide geographical area during the mid-l970s, ranging from means (males and females) of 0.8-1.5 mg/kg for total DDT isomers (S-DDT) and 0.9-3.0 mg/kg for total PCBs (S-PCB) (measured as Aroclor 1254/1260) (1,2,5). Recent analyses of ringed seal blubber collected at Holman Island in the western Canadian Arctic (3) showed significant declines of S-PCB and p,p’-DDE but not of p,p’-DDT. Toxaphene and hexachlorocyclohexane isomers (S-HCH) are the major organochlorine contaminants in Canadian arctic marine fish including arctic cod (13). Polar bears were the first component of the arctic marine food chain to have received a systematic study of PCB and chlordane levels on an isomer-specific basis, as described in the accompanying paper (14). All published work to date on organochlorines in arctic seals and fishes has used packed-column gas chromatographic (GC) techniques, and therefore, the individual components of PCBs have not been reported. Chlordane compounds, when reported at all, have been restricted to oxychlordane and cis- and trans-chlordane (15). Highresolution capillary GC with electron capture (HRGCECD) and mass spectrometric (GC-MS) detection has been applied recently to a wide variety of marine mammal and fish extracts for determination of individual PCBs and some chlordane components (16-18) but rarely for surveys of large numbers of individual animals. Our objective in this study was to identify all major organochlorines in samples of ringed seal blubber, arctic cod muscle, and polar bear fat using HRGC-ECD and GC-MS and to examine the bioaccumulation of these contaminants in three trophic levels of the arctic marine food chain. Experimental Section Sampling. Blubber and liver tissue samples from 33 ringed seals were collected in Barrow Strait near Resolute, N.W.T., during April 1984 and from 26 ringed seals collected in Admiralty Inlet (north Baffin Island) between January and April 1983 (Figure 1). Five ringed seal blubber samples from Admiralty Inlet, collected in 1975-1976 and three ringed seal blubber samples collected in 1972 from Grise Fiord, and previously analyzed by Bowes and Jonkel ( I ) , were also analyzed. The samples collected during the 1970s had been archived at -40 “C. Arctic cod were collected at the same locations in August 1984 by gill netting. Polar bear adipose tissue was obtained Environ. Sci. Technol., Vol. 22, No. 9, 1988 1071
0
Figure 1. Map of northern Baffin, Lancaster Sound, and Barrow Strait regions where arctic cod, ringed seal, and polar bear samples were collected.
from specimens collected in Barrow Strait in 1982 and Pond Inletlnorth Baffin Island in 1984, as part of an extensive survey reported by Norstrom et al. (14). All Samples were stored in plastic bags (-50 “C) until processed. Fish were filleted, and muscle from 27 (Admiralty Inlet) and 14 (Barrow Strait) individuals was pooled, by blending with dry ice, to yield two large samples (18 g) for analysis a t each site. Bear adipose tissue homogenates from 10 individuals were pooled from each location (14). Seals were aged by tooth section and fish by examination of otoliths. Standards. Four well-characterized mixtures containing a total of 51 PCB congeners were obtained from the National Research Council of Canada, Atlantic Research Laboratories, Halifax. An additional PCB, 2,4,2’,4’,5’pentachlorobiphenyl (PCB-99) (Ultra Scientific, Hope, RI), was included. Other organochlorine standards were obtained from the U.S. EPA repository. Extraction and Separation. Extraction and chromatographic procedures are described in Norstrom et al. (14) except those used for seal tissues. Seal blubber (1g) and liver (5 g) samples were mixed with anhydrous sodium sulfate and ball-milled in the tube with hexane (30 min) in a 50-mL capped centrifuge tube on a high-speed shaker (19). Aliquots of the extracts were subjected to gel permeation chromatography (GPC) to remove coextractive lipids and then chromatographed on Florisil to separate organochlorines into nonpolar (fraction 1,hexane), medium polarity (fraction 2, hexane-DCM, 85:15), and polar (fraction 3, hexane-DCM, 1:l)fractions for HRGC-ECD and GC-MS analysis (14). Gas Chromatography. Gas chromatographic operating conditions were identical with those described by Norstrom and Won (20). Capillary GC was performed on a Hewlett-Packard 5890 equipped with a 63NiECD. A fused silica column (60 m X 0.25 mm i.d.) coated with a crosslinked, bonded phase (DB-5, J&W Scientific) was used for all separations. Under these conditions, the retention time of decachlorobiphenyl was 52.2 min, and peak reproducibility was 0.004 min. GC-MS was carried out on a Hewlett-Packard 5987B as described by Norstrom et al. (14). PCBs were identified on the basis of identical retention times (window f 0.1%) with 52 congeners (Table I) or, in 1072
Environ. Sci. Technol., Vol. 22, No. 9, 1988
the case of isomers not available, e.g., PCB-74, -70, -95, -110, and -146, on the basis of patterns and order of elution of peaks in an Aroclor 125411260 (1:l) standard mixture. Quantitation of PCB congeners was carried out with response factors from individual standards or with ECD response factors calculated from the weight percent of the isomer in the total ion chromatogram (TIC) of an Aroclor 1254 standard. Where isomers were known to coelute (21), PCB-70176, -95166, -56160, 44/89, -1561171, -1571200, and -1721197, an average ECD response factor was calculated from the TIC of Aroclor 1254. All congeners were quantitated individually and summed to obtain total PCB (S-PCB). Quantitation of chlordane-related compounds for which standards were not available was carried out as described by Norstrom et al. (14). Total chlordane (SCHLOR) was the sum of all chlordane-related compounds including heptachlor epoxide. Toxaphene was quantitated by summing six peaks in Florisil fraction 2 identified as toxaphene-related by GC-MS and multiplying by a response factor based on the area of the six peaks in a toxaphene standard (22). Low levels of organochlorines in fish muscle extracts were confirmed by selected ion monitoring (SIM) of characteristic ions of di- through nonachlorobiphenyls (mlz 222, 258, 292, 326, 360, 394, 430, and 464) and of chlordane-related compounds (mlz 100,337,371,387, and 405). Average response factors for six tetra- to pentachlorobiphenyl standards were used to quantify tri- and tetrachlorobiphenyls in fish extracts, in the absense of suitable standards, because of the similarity of SIM response for these homologues (23). Data Analysis and Recovery Studies. Linear correlations of organochlorine concentrations in seal blubber with age (for results from each sampling site and year) were performed with log-transformed data because there appeared to be some means-variance correlation in the data. Significant differences between sample means were determined with Student’s t test. Recoveries of PCBs and organochlorine pesticides from fortified egg samples by procedures identical with those described have been reported previously (20). Recovery efficiencies of a standard mixture of organochlorine pes-
Table I. S t r u c t u r e s and Relative Proportions (to PCB-153) of PCB Congeners Determined in Arctic Cod Muscle, Ringed Seal Blubber, and Polar Bear Fat"
IUPAC no.*
chlorine substitution ring 2
17/18 31/28 52 49 47/48 44 41/71 40 74 70176 66/95 56/60 84/89 101 99 97 87 85 110 151 149 118 114 146 153 105 141 137 138 178 187 183 128 174 177 2,394 1561171 3.412.3.4 1571200 1721197 180 199 170 201 1961203 194 206 209
fraction of PCB-153 in each species cod seal bear muscle blubber fat
~
0.12 0.21 0.46 0.42 0.08 0.25 0.03 0.02 0.15 0.40 0.89 0.18 0.11 0.82 0.39 0.28 0.42 0.13 0.72 0.26 0.72 0.49 0.02 0.05 ref 0.09 0.13 0.02 0.88 0.11 0.46 0.17 0.06 0.22 0.11 0.09 0.02 0.12 0.39 0.08 0.19 0.11 0.11
