Aquaculture 254 (2006) 234 – 247 www.elsevier.com/locate/aqua-online
Occurrence of persistent organic pollutants in sediments collected near fish farm sites Paula J. Sather a , Michael G. Ikonomou a,⁎, Kats Haya b a
b
Department of Fisheries and Oceans, Institute of Ocean Sciences, Marine Environmental Quality Section, Sidney, British Columbia, Canada V8L 4B2 Department of Fisheries and Oceans, St. Andrews Biological Station, 531 Brandy Cove, St. Andrews, New Brunswick, Canada E5B 2L9 Received 27 April 2005; received in revised form 17 August 2005; accepted 19 August 2005
Abstract The sediment under four New Brunswick fish farm net pens was examined for the persistent organic pollutants (POPs): polychlorinated biphenyls (PCBs), polychlorinated dibenzo-p-dioxins and furans (PCDD/Fs), polybrominated diphenyl ethers (PBDEs), pesticides, and polyaromatic hydrocarbons (PAHs). Concentrations of these POPs were compared according to distance from the net pen (0 m, 25 m, 50 m, and 100 m), sediment quality (anoxic, hypoxic, normoxic, and a remediation site), and published levels from locations worldwide. In general, at the anoxic sites POP concentrations were higher than at other sites, and they did not drop in concentration over distance to 100 m. The highest concentrations of the POPs examined here were low relative to polluted sites worldwide. Crown Copyright © 2005 Published by Elsevier B.V. All rights reserved. Keywords: Aquaculture; Sediments; PCB; PCDD/F; PBDE; Pesticides; PAH
1. Introduction Aquaculture or “fish farming”, the practice of raising fish, crustaceans, and molluscs in captivity, has increased rapidly over the last two decades. According to FAO (Fisheries and Agriculture Organization) statistics (F.A.O., 2002) since 1970 aquaculture has increased annually at an average compounded rate of 9.2% while capture fisheries have increased only at 1.4% and terrestrial farmed meat at 2.8%. Low income, food deficit countries account for the bulk of this ⁎ Corresponding author. Tel.: +1 250 363 6804; fax: +1 250 363 6807. E-mail address:
[email protected] (M.G. Ikonomou).
increase, but developed countries still show a growth rate of 3.7% since 1970. While North American aquaculture contributes only a small portion to the world total (1.8%), it has nevertheless been growing rapidly. In Canada, aquaculture industry operations exist in provinces on both the east and west coasts. New Brunswick's aquaculture industry is the second largest in the country, and is that province's fastest growing resource industry (G.N.B., 2002). However, as the number of fish farms grows so does the amount of waste from these farms, and they are thus coming under increasing scrutiny by environmentalists and researchers. The advantages of fish farming seem obvious: a more secure supply and less pressure on wild stocks. The downside includes issues such as the introduction
0044-8486/$ - see front matter. Crown Copyright © 2005 Published by Elsevier B.V. All rights reserved. doi:10.1016/j.aquaculture.2005.08.027
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of non-native species (Hindar, 2001) and the impacts of the farming operation both on the fish themselves and on the marine habitat at or near the fish farms. These impacts to the marine environment include changes to nutrient and dissolved oxygen levels in the water (McClelland and Valiela, 1998; Ingrid et al., 1997; E.P.A., 1999), and changes to the physical and chemical characteristics of the seabed (benthos) under and nearby the fish farm net pens. Many of these changes, including increases to the production of bacteria, methane, and H2S, and the persistence of antibacterial agents, have been or are being investigated (Sutherland et al., 2001, and references contained within). Potential pollutants, introduced directly to the marine environment as the result of aquaculture activities, include antifoulants such as copper (Berstssen et al., 1999), medicines such as antibiotics, anaesthetics, disinfectants, and sea lice control pesticides (Paul and Davies, 1986; Zitko, 1994; Ernst et al., 2001), as well as unintended additives or contaminants of feed and oil such as polychlorinated biphenyls (PCBs), pesticides, and other POPs (Gruger et al., 1977; Easton et al., 2002; Jacobs et al., 2002). Assessing the impact to the benthos is not trivial as there are many unknowns and variables in the system. In New Brunswick, Canada, the Department of the Environment and Local Government (DELG) which has authority over these fish farms, rates sediment condition according to redox potential, and to the accumulation of sulphide and ammonia. Redox potentials drop as oxygen concentrations fall, and become more negative with higher impacts. Sediment conditions are classified, in order of decreasing quality, as normoxic, hypoxic, and anoxic. Anoxic conditions, where redox potential (Eh) b − 100 mVNHE (normal hydrogen electrode) and sulphide levels at N 6000 μM, are considered unacceptable (N.B.D.A.F.A., 2000). Other variables can also be used to assess the impact to sediment, and Chou et al. (2002) examined the concentrations of some metals (Cu, Zn, Mn, and Fe), particle size, and organic carbon content in relation to their ratings according to the sediment criteria defined by DELG. They have shown the Cu, Zn, organic carbon, and b 63 μm particles increase in concentration as conditions become more degraded while Mn and Fe levels fall. Very little is known about the levels of POPs in the sediments under fish farm net pens though many groups have studied contaminant accumulation in wild fish stocks and marine mammals. The contaminants examined include organic pollutants such as polychlorinated dibenzo-p-dioxins and furans (PCDD/
235
Fs), PCBs, and polybrominated diphenyl ethers (PBDEs) (Butcher et al., 1997; MacDonald et al., 1997; O'Neill et al., 1998; Addison and Smith, 1998; Ross et al., 2000; Rayne et al., 2003). Increasingly, these efforts have included farmed fish and their feed (Easton et al., 2002; Jacobs et al., 2002), and have led some researchers to suggest reduced consumption recommendations based on the contamination levels in farmed salmon (Easton et al., 2002; Hites et al., 2004). In this paper we undertake a survey examination of several classes of persistent organic pollutants (POPs) in the sediment beneath and close to fish farm net pens located in southwestern New Brunswick to find out if they are present, and, if so, what is their signature and distribution. Specifically, we attempt to determine: a) if contaminant concentrations are higher in more degraded sediment environments (anoxic, hypoxic sites) than in less degraded sediment environments (normoxic, remediation sites); b) if the levels of these contaminants change with distance (0 m, 25 m, 50 m, and 100 m) from the net pens; c) what the contaminant levels of PCBs, PCDD/Fs, PBDEs, polyaromatic hydrocarbons (PAHs), and pesticides in sediments under and near net pens are, and how these levels compare to other published values worldwide; and d) what are the characteristic congener or compound profiles found in the sediment under and around the net pens. The number of samples examined is low, so the work presented here is preliminary, but it is offered as a starting point in the examination of POPs in fish farm sediments. This point must also be kept in mind during the speculative portions of the discussion. 2. Methods and materials 2.1. General PCDD/Fs were analysed by a method measuring the seventeen 2,3,7,8-TCDD/F congeners individually. PCBs were analysed by a full congener method measuring 206 of the possible 209 congeners eluting singly (132 congeners) or as coeluters (74 as 2 or more coeluters). The PCB congeners are numbered according to Ballschmiter and Zell (1980). The PBDE analysis measures 61 selected congeners, and the PAH and pesticide analyses include 54 and 13 specific compounds respectively. Differences between sampling groups were investigated using single factor ANOVA. Calculations were carried out using Microsoft Excel software.
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2.2. Sites and sampling
current. The sediments were placed in 1 L glass Mason jars, and stored at − 27 C.
In 1998 divers collected four surficial sediment samples from each of four fin fish aquaculture sites in Southwestern New Brunswick for a total of 16 samples. The sampling was conducted under a confidentiality agreement with the fish farmers, so exact locations are known only to the divers and the farmers. Consequently, information regarding farming conditions, or conditions prior to farming, is unknown. The sites chosen reflect four different soil environments: anoxic, hypoxic, normoxic, and a remediation site unused for a year to allow for natural recovery from the impact of the fish farm operation. The soil environments were rated at collection by redox potential (Eh) according to the sediment criteria for the depositional zone defined by the Department of Environment and Local Government of New Brunswick, Canada (N.B.D.A.F.A., 2000; Janowicz and Ross, 2001). These ratings are: Normoxic, (Eh) N + 100 mVNHE (normal hydrogen electrode), sulphide b 300 μM; Hypoxic, (Eh) 0 to − 100 mVNHE, sulphide 1300–6000 μM; and Anoxic, (Eh) b − 100 mVNHE, sulphide N 6000 μM. At each site samples were collected immediately under the net pens (0 m), and at 25 m, 50 m, and 100 m from the net pens along the tidal
a)
2.3. Sample preparation and analysis The samples were stored originally at the St. Andrews Biological Station, St. Andrews, New Brunswick. Subsequently they were shipped to the Institute of Ocean Sciences in Sidney, B.C. for further analysis. Samples were thawed and homogenized. Aliquots of approximately 10 g wet weight (ww) for the contaminant extraction and analysis, and 2 g ww for moisture content, organic carbon, and organic nitrogen determination were removed. The methods for extraction, work-up, and analysis of pesticides, PCDD/Fs, PCBs, and PBDEs have been previously published by Ikonomou et al. (2002a), MacDonald et al. (1997), and Rantalainen et al. (1998). Comprehensive details of every part of the extraction, work-up, and analysis are also available in our method manual (Ikonomou et al., 2001). Briefly, sediment samples were spiked with a representative suite of 13C-labelled internal standards and soxhlet extracted with toluene/acetone (80:20) for 16 h. As pesticides are temperature and pH sensitive, further cleanup proceeded only after splitting the extract into
Organic Carbon Content (%)
organic carbon (%)
5 4
anoxic
3
hypoxic
2
remediation
1
normoxic
0 0m
b)
25 m
50 m
100 m
Moisture Content (%)
70
Moisture (%)
60 anoxic
50 40
hypoxic
30
remediation
20
normoxic
10 0 0m
25 m
50 m
100 m
Fig. 1. (a) Organic carbon content and (b) moisture content given as percentages.
P.J. Sather et al. / Aquaculture 254 (2006) 234–247
concentration (ng/kg)
a)
2378 TCDD/F (ng/kg)
400 anoxic
300
hypoxic 200
remediation
100
normoxic
0 0m
concentration (ng/g)
b)
concentration (ng/g)
50 m
100 m
PCB (ng/g) anoxic hypoxic remediation normoxic
c)
25 m
50 m
100 m
PBDE (ng/g)
4 anoxic
3
hypoxic 2
remediation
1
normoxic
0 0m
d) concentration (ng/g)
25 m
12 10 8 6 4 2 0 0m
25 m
50 m
100 m
pesticide (ng/g)
20 anoxic
15
hypoxic 10
remediation
5
normoxic
0 0m
e) concentration (ng/g)
237
25 m
50 m
100 m
PAH (ng/g)
3000 2500 2000 1500 1000 500 0
anoxic normoxic
0m
25 m
50 m
100 m
Fig. 2. Total dry weight concentration (sum of congeners or compounds) for (top to bottom): 2378-PCDD/F (ng/kg); PCB (ng/g); PBDE (ng/g); pesticide (ng/g); and PAH (ng/g). Each sample type (anoxic, hypoxic, remediation, and normoxic) shows concentration levels at 0 m, 25 m, 50 m, and 100 m respectively.
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two portions. One portion was passed through a Florisil column before being spiked with recovery standards and analyzed by HRGC/HRMS for pesticides. The other portion was acid–base washed and then cleaned through three columns in turn, all eluted with DCM/hexane (1:1): 1) layered silica gel (basic, neutral, acidic, and neutral silica); 2) copper filings and sodium sulphate (Na2SO4); 3) activated neutral
alumina capped with anhydrous Na2SO4. The final eluants were separated by a carbon fibre HPLC into four fractions: 1) di-through tetra-ortho (DO-) PCBs; 2) mono-ortho (MO-) PCBs; 3) non-ortho (NO-) PCBs; 4) PCDD/Fs. The fractions were spiked with recovery standards and analyzed by HRGC/HRMS for PCBs and PCDD/Fs, then recombined and analysed for PBDEs.
Table 1 Comparison of sediment contamination from this study to that from various studies worldwide This study: New Brunswick fish farm sediment
Sites: industrial/contaminated
Remote or pre-industrial
PCBs (ng/g dw) Total PCBs
1.067–10.417
0.050–2.54 (Finland)b 2.03–5.91 (Antarctic)d
∑10 congeners ngTEQ/g
(8.0–45) × 10–5
0.9–1211 (Alexandria H., Egypt)a 0.05–3200 (various)c n.d.–14.9 (Bohai and Yellow Seas)e
2400; 3790 (Tittabawassee R. Michigan)f 121–814 (R. Po, Italy)g
35 (Finland)b 39 and 158 (1888), 785 (1984), and b400 (1998, Isle Royale, L. Superior)h
PCDD/Fs (ng/kg) ∑2378 congeners ∑Homologue totals
20.7–328.9
ngTEQ/kg
0.49–3.32
PBDEs (ng/g O.C.) ∑60 congeners + 209 ∑6 congeners + 209 ∑BDE47 and 99 PAH (ng/g dw) ∑54 PAHs ∑16 PAHs ∑35 PAHs ∑14 PAHs
0.48–4.36 160 (near Oslo, Norway)i ∼ 16 (Baltic Sea) j
511.58–2736 20–344,600 (Santander Bay, Spain)k m
4–855 (Aquitaine, France) 25–1450 (Cotonou region, Benin)m 20.4–5734.2 (Bohai and Yellow Seas)e
∑10 PAHs Pesticides (ng/g) ∑16 pesticides⁎ ∑DDTs⁎⁎
a
0.649–15.482 b0.25–885 (Alexandria H., Egypt)a 0.06–72 (Black Sea)n 0.37–1417.08 (Bohai and Yellow Seas)e
Barakat et al., 2002. Isosaari et al., 2002. c Table 2 from c. d Montone et al., 2001. e Ma et al., 2001. f Hilscherova et al., 2003. g Fattore et al., 2002. h Baker and Hites, 2000. i Zegers et al., 2003. j Nylund et al., 1992. k Viguri et al., 2002. l Ricking and Schulz, 2002. m Soclo et al., 2000. n Fillmann et al., 2002. ⁎ Includes DDTs and metabolites (o, p and p, p DDTs, DDEs, and DDDs). ⁎⁎ DDTs and metabolites; R. = River; H. = Harbour; L. = Lake. b
b100 (1750–1800) l
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239
eV), using Multiple Ion Detection (MID) to enhance sensitivity. At least two characteristic ions for each target analyte and surrogate standard were monitored. The column used was a Restek Rtx-5 (30 m, 0.25 mm i.d. × 0.25 μm film thickness). Quantification of target analytes was by the isotope dilution method. Concentrations were determined by comparison of the quantification ion's area to that of the corresponding deuterated surrogate standard and correcting for response factors (determined daily using authentic PAHs). Calculated PAH concentrations were then corrected to 100% recovery by the recovery standard.
The HRGC/HRMS used was a VG-Autospec highresolution mass spectrometer (Micromass, Manchester, UK) coupled to a Hewlett-Packard 5890 Series II gas chromatograph fitted with a 50 m DB5 column. The HRMS was operated in the positive electron impact (EI) ionization condition (35 eV electron energy) at 10,000 resolution. Data was acquired in single ion monitoring (SIM) mode. PAHs were extracted and analyzed by Axys Analytical Services using their validated methods. Wet sediment samples were ground with anhydrous Na2SO4, spiked with a mixture of perdeuterated surrogate standards. The samples were extracted by column chromatography using methanol (MeOH) followed by DCM. The eluates were washed with a sodium hydroxide solution (0.1 M) and ultra pure water, and then dried and concentrated. Copper foil, activated by swirling in methanol while adding concentrated hydrochloric acid (HCl) dropwise until it brightened, and then rinsing three times with acetone, was added to remove sulphur. Cleanup of the samples proceeded through a silica gel column (5% deactivated) eluted with pentane (Fraction-1, discarded) and then DCM (Fraction-2, retained). Fraction-2 was concentrated and spiked with perdeuterated recovery standards. HRGC/HRMS analysis was carried out using a Finnegan INCOS 50 mass spectrometer (Finnegan Corp., San Jose, California) equipped with a Varian 3400 gas chromatograph with CTC autosampler (CTC Analytics, Switzerland) and a Prolab/Envirolink data system (Prolab Resources, Inc., Wisconsin, USA) for MS acquisition and control. The MS was operated at unit mass resolution, in the EI mode (70
2.4. Moisture and organic carbon and organic nitrogen determination Moisture content was determined by difference after drying the sediment sub-sample in a vented oven at 60 °C to stable weight. Organic carbon and organic nitrogen (CHN) was determined using methodology by Van Iperen and Helder (1985). Briefly, sediment sub-samples of approximately 500 mg were decalcified with 1 N hydrochloric acid (HCl) and dried overnight on a 70 °C hotplate followed by an additional 2 h at 105 °C. They were then hydrated at room temperature for 2.5 h with weighing every halfhour to determine that hydration had stabilised. Approximately 4–6 mg of the acidified sub-samples were weighed into tin cups for elemental analysis using a Leemens 440 Elemental Analyzer. The instrument was standardised against an Acetanilide standard (71.09%C and 10.36% N). Each analytical run began
15 10
OCDF
OCDD
1,2,3,4,7,8,9-HpCDF
1,2,3,4,6,7,8-HpCDF
1,2,3,4,6,7,8-HpCDD
1,2,3,7,8,9-HxCDF*
2,3,4,6,7,8-HxCDF*
1,2,3,6,7,8-HxCDF*
1,2,3,4,7,8-HxCDF*
1,2,3,7,8,9-HxCDD*
1,2,3,6,7,8-HxCDD*
1,2,3,4,7,8-HxCDD*
2,3,4,7,8-PeCDF*
1,2,3,7,8-PeCDF*
1,2,3,7,8-PeCDD*
0
2,3,7,8-TCDF
5
2,3,7,8-TCDD
weight percent
20
congener Fig. 3. 2,3,7,8-TCDD/F congener composition expressed as a percentage of total 2,3,7,8-TCDD/F concentration for a representative sample (normoxic site, 0 m from pen). OCDD weight percentage is 68.
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6
weight percent
5 4 3 2 1 162
170190
176
183
191
198
205
176
183
191
198
205
154 154
170190
147 147
162
137 137
124
142131
116125117
99
108107
91
85
79
68
53
6174
46
40
34
25
19
13
4/10
0
142131
124
116125117
108107
99
91
85
79
68
6174
53
46
40
34
25
19
13
9 8 7 6 5 4 3 2 1 0 4/10
weight percent
congener BZ number
congener BZ number Fig. 4. Congener composition expressed as percentage of total PCB concentration for an approximate “best” fit mixture of Aroclors (top, 1:1:1 1242:1254:1260) and for a representative sample (anoxic site, 0 m from pen). Congener order is by BZ number from 4 to 208 with coeluters identified placed at lowest congener position. Tick marks are every third congener with labels every sixth congener. Coeluting congeners are: 4/ 10; 5/8; 7/9; 16/32; 20/33; 24/27; 41/64/71; 42/59; 47/48/75; 52/73; 56/60; 61/74; 70/76; 83/109; 84/92; 86/97; 87/115; 90/101; 93/102; 106/ 118; 107/108; 116/117/125; 131/142; 132/153; 134/143; 135/144; 138/160/163/164; 139/140; 146/161; 170/190; 172/192; 174/181; 182/187; 196/203.
3. Results The discussion is divided into three sections. The first part is the comparison of the samples to each
20 18 16 14 12 10 8 6 4 2 0 1 2 3 7 8/11 10 12 13 15 Di(1) 17 25 28/33 30 32 35 37 Tr(1) Tr(2) 47 49 66 71 75 77 85 99 100 105 116 119 126 Pe(1) Pe(2) Pe(3) Pe(4) Pe(5) Pe(6) Pe(7) Pe(8) Pe(9) Pe(10) 138/166 140 153 154 155 Hx(1) Hx(2) 181 183 190 OcI OcII OcIII OcIV Oc(1) 208 207 206 209
weight percent
and ended with tin cup/nickel sleeve blanks, and included the acetanilide standard and one sample replicate. Standard acetanilide analysed six times gave: 70.94 ± 0.64% carbon, 10.48 ± 0.18% nitrogen.
congener Fig. 5. PBDE congener composition expressed as percentage of total PBDE concentration for a representative sample (normoxic site, 50 m from pen). BDE209 weight percentage is 61. PBDE congeners of unconfirmed assignment are listed by homologue level and number consecutively, e.g. Pe(1).
P.J. Sather et al. / Aquaculture 254 (2006) 234–247
241
12
weight percent
10
8
6
4
0
1-Methylnaphthalene 2-Methylnaphthalene Acenaphthylene Acenaphthene Fluorene Phenanthrene Anthracene 2-Methylanthracene1 1-Methylphenanthrene 9/4-Methylphenanthrene1 Fluoranthene Pyrene 3Methylfluoranthene/benzo[a]fluorene Benzo[b]fluorene1 Benz(a)anthracene Chrysene/triphenylene Benzofluoranthenes Benzo(e)pyrene Benzo(a)pyrene Perylene Indeno(1,2,3-cd)pyrene Dibenzo(ac/ah)anthracene Benzo(ghi)perylene Naphthalene Dibenzothiophene Cadalene Pimanthrene1 Retene 4,5-Methylene phenanthrene1 Dehydroabietin Benzo[b]naphtho[1,2-d]thiophene 1-Methylchrysene 5,9-Dimethylchrysene Cholanthrene 9-Methylbenzo[b]fluoranthene 7-Methylbenzo[a]pyrene Dibenzofuran1 Benzo[ghi]fluoranthene1 Benzo[c]phenanthrene1 Cyclopenta[cd]pyrene Benzo[a]fluoranthene1 Anthanthrene1 2-Methylphenanthrene1 3-Methylphenanthrene1 C2-Naphthalenes C3-Naphthalenes C4-Naphthalenes C2-Phenanthrenes/anthracenes C3-Phenanthrenes/anthracenes C1-Fluoranthenes/pyrenes C2-Fluoranthenes/pyrenes C3-Fluoranthenes/pyrenes C1-Dibenzothiophenes C2-Dibenzothiophenes
2
Fig. 6. PAH composition expressed as percentage of total measured PAH concentration for a representative sample (anoxic, 0 m from pen).
tions found here to a sampling of literature values found for contaminants in sediment worldwide (presented in Table 1), and to Canadian Council of Ministers of the Environment (CCME) guidelines for marine sediment quality. The third section describes the representative congener or compound compositions for each contaminant group expressed as weight percentages (presented in Figs. 3–7), and discusses
other, and is illustrated by Figs. 1 and 2. We look for differences in contaminant concentration between the four different sediment environments and for changes in contaminant concentration as distance from the net pen increases. Some statistical treatment is offered, though, due to the small number of samples studied here, strong conclusions are approached cautiously. The second section compares contaminant concentra-
weight percent
40 30 20 10
mirex
pp-ddt
op-ddt & pp-ddd
op-ddd
pp-dde
trans-nonaclor
cis-chlordane
op-dde
heptachlor epoxide
heptachlor
g-HXH
hexachlorobenzene
0
Fig. 7. Pesticide composition expressed as percentage of total measured pesticide concentration for a representative sample (remediation site, 25 m from pen).
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what these patterns may indicate about contaminant sources. 4. Discussion 4.1. Influence of sediment condition and net pen distance Before discussing contaminant levels in relation to sediment condition and distance from the net pens, it is useful to discuss the organic carbon and moisture levels in the samples. Fish feces and any excess feed contribute to increased levels of organic carbon in the sediments near the net pens of more highly impacted sites compared to those at less impacted sites. The concurrent decomposition of these organics drops the redox potential, and therefore it is expected that higher organic carbon levels are associated with lower redox potentials (and thus with sediment ratings that are hypoxic or anoxic) in impacted sediments. This expectation holds true for the samples in this study. For example, the mean organic carbon levels at each site are not the same (p = 9.9 × 10− 4), and range from the highest at the anoxic site through to the lowest at the remediation and normoxic sites (see Fig. 1). In addition, organic carbon levels remain approximately constant at the normoxic and remediation sites over all distances. In contrast, as distances increase from the net pens, organic carbon levels drop at the anoxic and hypoxic sites. This drop is expected as organic material of aquaculture origin would be expected to decrease with increasing distance from the net pen. However, as can be seen in Fig. 1, the organic carbon levels at the anoxic sites do not fall as low as samples at the other sites even at 100 m from the net pen, which suggests that the organic material of aquaculture origin at such sites extends to at least 100 m. The moisture content of the samples (see Fig. 1) illustrates the same point with mean levels different for at least one sample group (p = 7.39 × 10− 4). At 0 m from the net pen both the anoxic and hypoxic samples have very high moisture contents of 60% and 54% respectively, while the remediation and normoxic sites are less than 40% moisture. Over distance, the remediation and normoxic samples remain at roughly similar levels, the hypoxic samples fall to levels of b25% moisture, and the anoxic samples remain at ∼ 60% moisture. The implication, again, is that evidence of organic enrichment is detectable even at 100 m distance away from sites rated as anoxic. Where the conditions are not as extreme (hypoxic), the evidence
of this organic enrichment drops as the distance increases to 100 m. Examination of the contaminant levels in the sediment samples again reveals similar patterns. Concentration means, calculated for each contaminant over all distances, are different (p = 0.0306 for PBDEs; all others b = 0.00725), and contaminant levels are highest at the anoxic sites and lowest at the normoxic and remediation sites. When the contaminants are examined by distance from the net pen (Fig. 2) we find that only at the hypoxic sites do contaminants decrease somewhat reliably as distance increases (r2 = 0.58–0.88, r b 0 for all POPs measured), while at the other sites they show lower correlations with distance (r2 = 0.0003–0.51, r = − 0.70–0.71). These patterns are clearest for the PCDD/ Fs, PCBs, and pesticides. PAHs were only measured at normoxic and anoxic sites, so the complete pattern is not available. However, the higher levels of PAHs at the anoxic sites and lower levels at the normoxic sites are consistent with it. Again these results suggest that the influence of aquaculture activity at unacceptably impacted net pen (anoxic) sites extends further than it does for healthier sites, although they are suggestive rather than conclusive as few samples were examined. 4.2. Contaminant concentrations Because we have neither data from these sites before the commencement of fish farming nor data from similar, unfarmed, sites nearby, there are no direct background measurements. Therefore, to aid a qualitative understanding of the contaminant concentrations discussed in this work we have compared them to published values from other sediments worldwide (see Table 1). However, because we are amongst the first to examine the sediments beneath fish farm net pens specifically for POPs, this comparison is to marine and fresh water sediments generally rather than to other fish farm sediments. Sampling locations may be divided into three general types. The first are from industrial or contaminated sites worldwide. The second, from remote sites in Antarctica and Finland, give background data for PCBs and PCDD/Fs. Finally, the third, from sediment cores from the Baltic and White Seas and from Isle Royale in Lake Superior, give pre-industrial background data for PCDD/Fs and PAHs. Comparisons of PBDE, PAH, and pesticide levels are complicated by the number and variety of congeners (PBDEs) or compounds (PAHs and pesticides) selected for study (noted in Table 1). Also, many congeners/compounds in these classes of POP are currently in wide use, and levels found in the environment
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may reflect the usage patterns of each place. An example of this reflection of usage is the general finding that PBDE levels are higher in Europe than in Japan and higher yet in North America than in Europe (Hites, 2004). Despite these complications the comparisons show us that, in general, totals levels for all the contaminants were low compared to contaminated sites globally though some PCDD/F, PCB, and PAH concentrations may be elevated compared to the pre- or post-industrial background levels. One possible source of POP contamination in fish farms is the feed, and several groups have published measurements of contaminants in fish feed and oils. These studies have shown contaminant concentration in the order PAH (∑20 PAHs 82–1333 ng/g ww, Easton et al., 2002;) N total PCBs (b 15–N 90 ng/g ww, Hites et al., 2004; 76–1153 ng/g lipid, Jacobs et al., 2002; 65.5 ng/g ww, Easton et al., 2002) N pesticides/DDTs (∑DDTs and their metabolites 34–52 ng/g lipid, Jacobs et al., 2002; ∑25 pesticides 48.1 ng/g ww, Easton et al., 2002) N PBDEs (∑9 PBDEs 8–24 ng/g lipid, Jacobs et al., 2002; ∑41 PBDEs 1.9 ng/g ww, Easton et al., 2002) N PCDD/Fs (b1–∼ 7 pgTEQ/g ww, Hites et al., 2004). The Hellou study (which includes our samples) examines fish feed specifically from New Brunswick fish farm operations, and finds levels of PCB153 and p, p′-DDE within a range comparable to other published values (Hellou et al., 2005). With the exception of the PAHs, which appear to be at slightly higher levels in the sediment than in the feed, the highest concentrations of these POPs in the sediment samples are at or slightly lower than the low ends of the ranges found in fish feed. Although the concentrations are lower than in fish feed, to understand the relationship between input levels and the resultant sediment levels will require an exploration of the interaction of many aspects of the farming operation (production levels, species, biomass, time of operation) together with the ocean floor characteristics (flow rates, sedimentation rate, bacterial activity). Also, given the small sampling size, confirmation of the generality of the findings presented here will require more complete sampling that includes sites not impacted by fish farm operations or other industrial activities. We have also, where possible, compared contaminant concentrations measured for this work to the CCME interim marine sediment quality guidelines (ISQGs) and probable effects levels (PELs) (C.C.M.E., 2003). These results are summarized here with the note that PEL levels are always higher than the ISQGs. The CCME ISQG and PEL guidelines for PCDD/F are given as ngTEQ/kg dw. The Toxic Equivalency Quo-
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tient (TEQ) is an estimate of total toxicity for PCDD/Fs whereby Toxic Equivalency Factors (TEF) have been estimated for each of the seventeen 2,3,7,8-PCDD/F congeners (Van den Berg et al., 1998). These TEFs are relative to the toxicity of 2,3,7,8-TetraCDD, which is assigned a value of 1. The TEQ for each congener is calculated by multiplication of its TEF value by its concentration, and total toxicity is the sum of the 17 TEQ values. For the PCDD/Fs the CCME ISQG and PEL are set 0.85 ngTEQ/kg and 21.5 ngTEQ/kg respectively. Calculated in terms of their TEQ values the New Brunswick fish farm samples are all well below the PEL, but some are higher than the ISQG. Specifically, the anoxic samples are about four times higher than the ISQG; the hypoxic samples (0 and 25 m) are about three times the ISQG, and all the others are similar to or slightly lower than the ISQGs. The PCB levels are all well below the CCME ISQGs of 62.3 ng/g (as Aroclor 1254) or 21.5 ng/g (total PCBs). CCME guidelines for PBDEs have not yet been established. Of the 54 PAHs measured in the anoxic and normoxic samples (hypoxic and remediation samples not analysed for PAHs) only 13 have CCME guidelines available. Of these 13 PAHs all samples had concentrations lower than the PELs and most were lower than the ISQGs. The exceptions follow. The 50 m anoxic sample showed much higher levels of 2-methylnaphthalene and naphthalene (165.00 ng/g and 109.00 ng/g respectively) than the other three anoxic samples (9.30–10.10 ng/g and 9.31–9.97 ng/g respectively), and also higher than the ISQGs (20.2 ng/g and 34.6 ng/g respectively). Next, the anoxic samples as a group show levels similar to the ISQGs for acenaphthylene (4.57–7.16 ng/g; ISQG = 5.87 ng/ g), acenaphthene (3.15–7.06 ng/g; ISQG = 6.71 ng/g), and phenanthrene (53.80–102.00 ng/g; ISQG = 86.7 ng/g). Finally, the normoxic samples show levels similar to the ISQGs for fluoanthene (43.3–120 ng/ g; ISQG = 113 ng/g) and dibenzo(ac/ah)anthracene (2.44–9.09 ng/g; ISQG = 6.22 ng/g), while the levels in anoxic samples are somewhat higher than the ISQGs (135.00–164.00 ng/g and 14.40–16.40 ng/g respectively). As with the PAHs, not all of the pesticides measured in this study are included in the CCME guidelines. However, the DDTs, DDDs, and DDEs (sum of o, p and p, p isomers in all cases) are included, with ISQG and PEL levels, in μg/kg (ng/g) dw, of 1.17 and 4.77; 1.22 and 7.81; 2.07 and 3.74; and respectively. The DDT levels are all much lower than the ISQG. In contrast, the anoxic samples show levels of DDDs and
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DDEs several times higher than the ISQGs, with DDEs in the 25, 50, and 100 m samples at or higher than the PEL. 4.3. Contaminant congener patterns Another purpose of this investigation is to examine the characteristic congener or compound profiles for each contaminant class. Inspection indicates that patterns are quite similar over all distances examined, and the characteristic congener/compound patterns for each of the contaminant types are shown in Figs. 3–7. In general, the PCDD/Fs show a pattern dominated by just 4 congeners (Fig. 3). These are OCDD (63% to 73% by weight), 1,2,3,4,6,7,8-HpCDF, 1,2,3,4,6,7,8-HpCDD, and OCDF, which together make up from 89% to 95% (by weight) of the 2378-PCDD/F congeners in the samples. This pattern is consistent with the air transport of combustion sources (Yunker et al., 2002; Macdonald et al., 1998) which show a predominance of OCDD and other highly chlorinated congeners, rather than sources such as those associated with chlorine bleaching (e.g. pulp mills) or PCP (pentachlorophenol) condensation (Yunker et al., 2002). For PCBs the characteristic congener pattern (Fig. 4) is close to that of a mixture of Aroclors 1242:1254:1260 (1:1:1) as determined by the mixing model method described by Sather et al. (2001). The sum of squares residual value for the samples averaged 37 with a standard deviation of 18. Low residual values indicate little change from Aroclor technical mixtures, which is consistent with sediment samples from a variety of locations that we have examined from the eastern and western coasts of Canada (Ikonomou, unpublished data, 2004). However, congener patterns from in house, unpublished, fish feed data show a pattern more closely resembling a mixture of Aroclors 1254:1260 (1:1) which is not consistent with the pattern found in the sediment samples. PBDEs, like PCBs, are produced as technical mixtures. Three major mixtures are produced: a “penta” mixture containing PBDEs 47, 99, 100, 153, and 154 in a 9:12:2:1:1 ratio, an “octa” mixture containing several hexa to nona chlorinated congeners, and a deca product containing mostly PBDE 209 (Hale et al., 2001; Sjödin et al., 1998; Alaee et al., 2003). Worldwide production in 1999 totalled approximately 67,000 tonnes with the majority (80%) as the deca product (penta 14%, octa 6%) (Arias, 2001). In sediments worldwide the dominant congeners have been reported as BDE99 or BDE47 (Rayne et al., 2003) although this may be because BDE209 (highly thermal and UV un-
stable) is often not measured (Hites, 2004). The PBDEs in the fish farm sediments are consistent with the production patterns. They show a congener pattern dominated by just 5 congeners (Fig. 5): PBDEs 209, 47, 99, 183, and 207. Together they make up from 81% to 93% of the total PBDEs (by weight). Of these BDE209 is most dominant making up from 42% to 84% (by weight) of the PBDEs in the samples. Commercial fish feed is reported to contain PBDEs, albeit at lower concentrations than PCBs, and thus may be a potential source (Easton et al., 2002; Jacobs et al., 2002). However, Easton et al. (2002) did not find BDE209 above the detection limit (0.65 pg/g ww) in the two samples of fish feed measured, which is not consistent with the PBDEs found in the fish farm sediments (BDE209 was not measured by Jacobs et al., 2002). Thus, other sources may be important, especially considering that PBDEs are currently in wide use, and wild fish from polluted waters have been reported to have much higher levels of PBDEs than farmed fish from less contaminated sites (Jacobs et al., 2002). PAHs appear in the environment from both natural and anthropomorphic sources. Natural sources include forest fires and volcanoes while anthropomorphic sources include non-combustion as well as combustion sources such as creosote, petroleum products, and the emissions from aluminium smelters. Some efforts have been made to identify the characteristic compound profiles from these various sources. According to Hellou et al. (2002) and the references cited within, typical combustion sources show a predominance of parent PAHs relative to alkylated PAHs while the reverse is associated with petroleum products. Also, characteristic phenanthrene/anthracene and fluoranthene/pyrene ratios of 2.0–8.8 and 1.2–1.5 respectively are reported to indicate the dominance of combustion sources. Both of these criteria suggest that the PAHs in the fish farm sediment samples (Fig. 6) presented here are from combustion sources. Parent PAHs are more abundant in the PAH profile than alkylated PAHs, with the most abundant PAHs being fluoranthene, pyrene, benzofluoranthenes, and cholanthrene. The phenanthrene/ anthracene ratios range from 2.7 to 8.4 (average 4.7, standard deviation 2.2), and the fluoranthene/pyrene ratios range from 1.21 to 1.49 (average 1.31, standard deviation 0.09). In contrast, pesticide sources are entirely anthropomorphic. The pesticide profiles seen in the fish farm sediment samples presented here (Fig. 7) are dominated by p, p′-DDE which makes up 27–58% of the pesticides by weight in each of the samples. The top 4 pesticides in each sample make up 82–90% of the pesticides by weight
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in each of the samples. They are (in order of abundance): p, p-DDE, o, p-DDT and p, p-DDD (coeluters), hexachlorobenzene, o, p-DDD, and transnonaclor. The p, pDDE/p, p-DDT ratio is used to indicate if p, p-DDT use is recent since p, p-DDE (metabolite of p, p-DDT) is not significantly present in technical p, p-DDT. The high ratios of p, p-DDE/p, p′-DDT found here (lowest at 11.9) indicates that the p, p-DDT use was not recent.
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processing and analyses of these samples. The authors gratefully acknowledge the manuscript review comments provided by Dr. Les Burridge and the assistance of Mr. Marc Fernandez. The financial support of the Environmental Sciences Strategic Research Fund (Fisheries and Oceans Canada) and the regional Fisheries and Oceans funding available to the Regional Dioxin Laboratory at Institute of Ocean Science made this work possible and are appreciated.
5. Conclusion References In summary, all of the contaminants examined in this study are at higher concentrations in the more highly impacted anoxic and hypoxic sediments (as defined by Redox potential) than in the less impacted normoxic and remediation sediments. In general, the levels of these compounds appear to be low in comparison to levels at contaminated sites worldwide. And finally, congener or compound patterns for each contaminant class can be characterized: PCDD/Fs congener profiles resemble background incineration profiles, PBDEs and PCBs reflect commercial mixtures, PAH ratios and profiles indicate combustion sources, and the p, p′-DDE/p, p′-DDT ratio of the pesticides does not indicate recent DDT usage. Further questions that are raised here may help to guide future research. For instance, is the contamination that we did find fish farm related? A comparison of the levels and congener/compound profiles of contaminants found in fish feed and oil to those found in sediments might help to clarify the connection between them. Also, a more focused sampling design could provide more substantial evidence of the relation of contaminant levels to sediment conditions. Next is the question of why the anoxic sites have higher levels of contamination than the other sites. Anoxic sediments have characteristically high sediment accumulations and bacterial mat covers (Fisheries and Oceans Canada, 2002), and have been described as “gel–mud deposits” by Sutherland et al. (2001). Is it higher quantities of material falling through the net pens that cause the elevated contaminant levels or other causes such as changes to bacterial activity? Further comparisons between fish farms with differing sediment ratings, including, in addition to contaminant levels, factors such as sedimentation fluxes, current flows, and fish farm activities, might help to answer these questions.
Acknowledgment The authors thank all the Regional Dioxin Laboratory chemists and laboratory assistants involved in the
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