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ABSTRACT: Two phosphate ester flame retardants, triphenyl phosphate (TPP) and 2-ethylhexyldi-phenyl phosphate (EHDPP) (both 14C-labelled) were added to two small artificial ponds (3 m3 volume) to give water concentrations of 60 μg/L for each compound. Both phosphate esters had half-lives of about 15 h in the water column and showed rapid sorption to bottom sediment. At 24 h posttreatment an estimated 28% of EHDPP and 9% of TPP added could not be accounted for by measurements of radioactivity in water, sediment and biota. Calculations of volatilization rates from water of the two compounds suggested that losses of EHDPP may have been due in part to volatilization. Bioconcentration of TPP by fathead minnows (Pimephales promelas) was similar to that predicted from laboratory studies on the uptake and clearance of TPP by rainbow trout (Salmo gairdneri). Prediction of the bioconcentration of EHDPP by duckweed (Lemna minor) from laboratory studies underestimated the rapid uptake of this compound observed in the ponds.
Environmental Toxicology and Chemistry 10/2009; 1(2):113 - 119. · 2.81 Impact Factor
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ABSTRACT: Uptake and elimination of 14C-labeled terbutryn, fluridone, triphenyl phosphate (TPP), trans-permethrin, methoxychlor and 2,4,5,2′,4′,5′-hexachlorobiphenyl (HCBP) by Chironomus tentans larvae were studied in sediment-water systems. Animals were exposed to three different sediments containing 50 to 500 μg/kg (wet weight) of each chemical, or were held in screened containers in water above the treated sediment for 24 or 96-h. Elimination of radioactivity was determined over a 48-h interval. Results were analyzed by use of a one-compartment kinetic model. Larvae exposed in sand or in water above sand had significantly higher concentrations of each chemical than those exposed in or above river (silty) or pond (silty clay) sediments. Uptake of terbutryn and fluridone, two hydrophilic compounds, was similar (24-h exposure) to that of methoxychlor and greater than that for TPP, trans-permethrin or HCBP, due to much greater partitioning of the former compounds into water above each sediment. TPP, trans-permethrin, methoxychlor and HCBP concentrations were significantly higher in larvae from sediment than in animals held in water above sediment. Uptake rate constants from water for each chemical were much greater than those for sediment, but due to the relatively large sediment-to-water ratio (1:5) and the high proportion of chemical in sediment, relative contributions of sediment and water uptake to body burden were similar. Assimilation of each compound by larvae from ingested sediments appeared to be negligible except for TPP and HCBP. Estimates of assimilation of TPP and HCBP in sand-water systems were much greater than those for sediments with higher organic matter content.
Environmental Toxicology and Chemistry 10/2009; 2(3):269 - 281. · 2.81 Impact Factor
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ABSTRACT: The bioconcentration of four synthetic pyrethroid insecticides (cis- and trans-cypermethrin, deltamethrin, fenvalerate and cis- and trans-permethrin) by larvae of the midge Chironomus tentans was studied in sand, silt and clay sediments and water (sediment/water ratio, 1:5). Larvae were exposed for 24 h in sediment and for 48 h in water above sediment that contained 12 to 640 ng/g 14C-labeled cypermethrin and 5 and 50 ng/g of the other compounds. Depuration of radioactivity following transfer to clean sand/water systems was monitored for 96 h. Bioconcentration factors for larvae held in sand ranged from 135 for trans-permethrin to 316 for deltamethrin. Larvae in water above sand accumulated 5- to 15-fold greater concentrations of each pyrethroid than did larvae held in water above silt or clay sediments. The lower bioavailability of each compound to larvae in water above silt and clay was attributed to greater sorption to suspended particulates and to dissolved organic carbon in these systems than in relatively particulate-free sand/water systems. The accumulation of pyrethroids by larvae in silt and clay sediments was best accounted for by the uptake of the dissolved portion of each compound in pore water. Depuration of the four pyrethroids by Chironomus larvae was rapid, with an overall half-life for radioactivity of 27 ± 8 h. Exposure for 24 h in sediments containing 5 ng/g concentrations of each pyrethroid had little effect on the behavior of the larvae, but at higher concentrations the animals were immobilized, although many survived following transfer to depuration experiments.
Environmental Toxicology and Chemistry 10/2009; 4(1):51 - 61. · 2.81 Impact Factor
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ABSTRACT: Terbutryn (2-ethylamino-4-(tert-butylamino)-6-methylthio-s-triazine) was applied in June 1978, to two farm ponds (A and C) near Winnipeg. Canada, to give 100 μg/l water concentrations. The persistence of the herbicide and its degradation products was monitored over a 61-week period following application. The half-life of terbutryn m the water column ranged from 3 weeks in Pond C, which contained heavy growths of cattails (Typha sp.) and duckweed (Lemna sp.), to 30 days in Pond A. which was free from aquatic macrophytes, Terbutryn residues m sediment reached a maximum of 1.4 μg/g (dry wt) in Pond A and 0.5 μg/g in C. Maximum concentrations of N-deethylated terbutryn (2amino-4-(tert-butylamino)-6-methylthio-s-tria-zine)(DET) were 14.4 μg/l in Pond A water after 61 weeks and 0.14 μg/g in Pond C sediment after 30 weeks. The maximum concentration of hydroxy-terbutryn (2-hydroxy-4-ethyl-amino-6-(tert-butylamino)-s-triazine) (HT) observed in pond water was 6.4 μg/l in Pond C after 7 weeks. HT was not detected in sediment (<0.05 μg/g) during the study. After 61 weeks, about 50% of the terbutryn that was added could still be accounted for in Pond A and 35% in Pond C. Terbutryn. DET and HT represented an estimated 71, 28 and 1%, respectively, of total terbutryn remaining in Pond A and 65, 29 and 6%, respectively, of that remaining in Pond C, 61 weeks after application, Terbutryn residues in Typha ranged from 0.3 μg/g (dry wt) in the shoot to 3.3 μg/g in the roots. After 12 weeks, terbutryn residues in plants (Pond C) were estimated to account for 1 to 4% of the herbicide in the pond.Résumé: Davenir de la terbuiryne dans lex étangs de farmes comptant ou nun des macrophytesDe la terbutryne (2-éthyle amino-4-(tert. butylamino)-6-méth-ylthio-s-triazine) a été appliquée en juin 1978 sur deux étangs de fermes (A et C) près de Winnipeg, Canada, pour obtenir une concentration dans l'eau de 100 μg/l. La persistance de l'herbicide et ses produits de dégradation ont été suivis pendant une période de 61 semainesaprés le traitement. La demi-vie de la terbutryne dans l'eau (en colonne) varia de 3 semaines pour l'étang C qui renfermait des plantes vigoureuses de masscties (Typhas sp.) et de lentilles d'eau (Lemna sp,). à 30 jours pour l'étang A qui ne contenait pas de macrophytes aquatiques. Les résidus de lerbutryne dans la vase atteignaient un maximum de 1.4 μg/g (P.S.) dans l'étang A et 0.5 μg/g dans l'étang C. Les concentrations maximales de lerbutryne N-déèthylèe (2 amino-4-(butylamino)-6-méthylamino-s-triazine), (TDE), ont atteint 14.4 μg/l dans l'eau de l'étang A après 61 semaines, et 0.14 μg/g dans la vase de l'étang C après 30 semaines. La concentration maximum d'hydroxyterbutryne (2-hydroxy-4-éthylamino-6-(terl. butylamino)-2-triazine). (HT), observée dans l'eau fut de 6.4 μg/l pour l'étang C après 7 semaines. HT n'a pas été dècelée dans la vase (<0.05 μg/g) au cours de ces recherches. Après 61 semaines. 50% environ de la terbutryne apportée pouvait encore ètre retrouvée dans l'étang A et 35% dans l'étang C. La terbuiryne, la TDE et l'HT furent évaluées respectivement à 71, 28 et 1% de la terbuiryne totale restant dans l'étang A. et à 65, 29 et 6% pour l'étang C, 61 jours après le traitement. Les résidus de terbutryne dans les Typhas allerent de 0.3 μg/g (p.s.) dans la partie aérienne à 3.3 μg/g dans les racines. Après 12 semaines, les résidus de terbutryne dans les plantes de l'étang C furent estimés entre l et 4% de l'herbicide dans cet étang.ZusammenfassungEinfluss der Vegetation auf das Schicksal von Terbutryn in Teichen.Terbutryn (2-Äthylamino-4-tert-butylamino-6-methylthio-s-triazin) wurde im Juni 1978 in zwei Teichen (A und C) in der Nhe von Winnipeg (Kanada) angewendet. Die Herbizidkon-zentration im Wasser betrug nach der Applikation 100 μg/l. Die Persistent von Terbutryn und das Verhalten seiner Abbaupro-dukte wurden 61 Wochen lang beobachtet. Die Halhwertszeit von Terbutryn im Wasser betrug im Teich C, der viel Rohrkolben (Typha sp.) und Wasserlinsen (Lemna sp.) enthielt, 3 Wochen und in Teich A. der frei von höheren Wasserpflanzen war, 30 Tage. Die höchsten beobachteten Terbulrynrückstnde im Sediment betrugen im Teich A 1.4 μg/g (Trgw.) und im Teich C 0.5 μg/g. Die höchsten Konzentralionen an N-dethyliertem Terbutryn (2-Amino-4-tert.-butylamino-6-methylthio-s-tria-zin) (DET) betrugen in Wasser von Teich A nach 61 Wochen 14.4 μg/l und im Sediment von Teich C nach 30 Wochen 0.14 μg/g. Die höchste beobachtete Konzentration an Hydroxyter-butryn (2-Hydroxy-4-thylmaino-6-tert.-butylamino-s-triazin) (HT) betrug im Wasser von Teich C nach 7 Wochen 6.4 μg/l Im Sediment konnte HT nicht nachgewiesen werden (0.05 μg/g). Nach 61 Wochen waren im Teich A noch ungefhr 50% und im Teich C noch 35% des zugesetzten Terbutryn vorhanden. Nach 61 Wochen betrug der Anteil von Terbutryn, DET und HT im Teich A, bezogen auf Gesamt-Terbutryn. noch schtzungsweise 71, 28 und 1% und im Teich C 65, 29 und 6%, Die Terbutryn-rückstnde in Typha bewegten sich zwischen 0.3 μg/g (Trgw.) im Spross und 3.3 μg/g in den Wurzeln. Nach 12 Wochen betrugen die Terbutrynrückslnde in den Pflanzen (Teich C) schtzungs-weise 1–4% der dem Teich zugesetzten Herbizidmenge.
Weed Research 07/2006; 21(2):59 - 70. · 1.92 Impact Factor
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ABSTRACT: Lake Winnipeg supports the largest commercial fishery on Canadian Prairies. It has been influenced by a variety of environmental forces and anthropogenic activities. To gain a better understanding of recent changes in nutrient status of the lake, it is important to reconstruct its previous history from sedimentary records. Lacustrine sediments are known to be an important sink of many dissolved and suspended substances, including phosphorus, hence, they provide a permanent historical record of changes occurring in the lake. These changes may be induced by natural factors or by anthropogenic activities in the watershed. Phosphorus profiles from dated sediment cores collected in 1999 and 1994 from the South Basin of Lake Winnipeg were investigated to determine phosphorus enrichment in recent sediments. To interpret the nutrient status and depositional conditions responsible for the trends in total phosphorus, three operationally defined forms of phosphorus (P) were determined: non-apatite inorganic P, apatite P, and organic P. Significant increases in sediment phosphorus concentrations were observed in the uppermost 20 cm of the cores and several anomalies were observed at depth. A doubling in total phosphorus relative to aluminum over the last fifty years is largely due to increases in the non-apatite inorganic fraction, suggesting that much of sedimentary phosphorus increase is attributable to changes in the nutrient status of the water column related to anthropogenic inputs. Organic phosphorus exhibits a subtle increase in the upper 20 cm of the gravity cores, likely due to increases in the primary productivity of the lake. Except for the slight increase in deeper sediments, apatite phosphorus, which is thought to be of detrital origin, remained fairly constant over the length of the cores. Anomalous spikes in phosphorus concentrations deeper in the cores, comprised mainly of the non-apatite inorganic phosphorus fraction, likely resulted from natural variation in local oxidizing conditions, possibly induced by changes in water circulation and/or changes in sediment deposition rates due to climatic variation. The results of this investigation contribute to increased understanding of the depositional history of phosphorus in the lake over the last millennium.
Aquatic Ecosystem Health and Management 07/2006; 9(3):307-318. · 0.65 Impact Factor
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W L Lockhart,
G A Stern,
R Wagemann,
R V Hunt,
D A Metner,
J DeLaronde,
B Dunn,
R E A Stewart,
C K Hyatt,
L Harwood,
K Mount
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ABSTRACT: Beluga whales have been hunted for food by Native People in the Canadian Arctic since prehistoric time. Here we report the results of analyses of total mercury in samples of liver, kidney, muscle and muktuk from collections over the period 1981-2002. We compare these results with human consumption guidelines and examine temporal and geographic variation. Liver has been analyzed more frequently than other organs and it has been used as the indicator organ. Mercury accumulates in the liver of the whales over time so that the whale ages are usually linked statistically to their levels of mercury in liver. Virtually all the samples of 566 animals analyzed contained mercury in liver at concentrations higher than the Canadian consumption guideline of 0.5 microg g-1 (wet weight) for fish. (There is no regulatory guideline for concentrations in marine mammals in Canada.) Samples from locations in the Mackenzie Delta in the western Canadian Arctic and from Pangnirtung in the eastern Canadian Arctic were obtained more often than from other location and these offered the best chances to determine whether levels have changed over time. Statistical outlier points were removed and the regressions of (ln) mercury in liver on age were used to calculate the level of mercury in whales of age 13.1 years in order to compare age-adjusted levels at different locations. These age-adjusted levels and also the slopes of regressions suggested that levels have increased in the Mackenzie Delta over the sampling period although not in a simple linear fashion. Other locations had fewer collections, generally spread over fewer years. Some of them indicated differences between sampling times but we could not establish whether these differences were simply temporal variation or whether they were segments of a consistent trend. For example, the levels in whales from Arviat were considerably higher in 1999 than in 1984 but we have only two samples. Similarly, samples from Iqaluit in 1994 exceeded considerably those in 1993 and the interval seems too short to reflect any regional temporal trend and more likely represent an extreme case of year-to-year variation. Previous analyses of data from geographically distinct groups had suggested that whales in the western Canadian Arctic had higher levels of mercury than those from the eastern Canadian Arctic. The present analysis suggests that such regional differences have diminished and are no longer statistically significant. No site has indicated significant decreases in more recent samples. The levels of total mercury in the most analyzed organs fell in the order of liver (highest levels), kidney, muscle and muktuk (lowest level). While muktuk had the lowest level of the organs most frequently analyzed, it is the preferred food item from these whales and it still exceeded the consumption guideline in most instances.
Science of The Total Environment 01/2006; 351-352:391-412. · 3.29 Impact Factor
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W L Lockhart,
G A Stern,
G Low,
M Hendzel,
G Boila,
P Roach,
M S Evans,
B N Billeck,
J DeLaronde,
S Friesen, [......],
S Atkins,
D C G Muir,
M Stoddart,
G Stephens,
S Stephenson,
S Harbicht,
N Snowshoe,
B Grey,
S Thompson,
N DeGraff
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ABSTRACT: Subsistence fishing has been an important source of food for Native People in northern Canada since prehistoric time. Measurements of the levels of mercury in edible muscle of northern fish have been undertaken for over three decades in efforts to evaluate the risks of consuming northern fish. This report summarizes the data obtained from 7974 fish of 25 species from sites distributed from the Yukon to Labrador. The most abundant species were lake trout, lake whitefish, arctic char, walleye, northern pike and burbot. The question being asked was essentially "Are the fish safe to eat?" The results were used to support decisions on fishing and consumption of fish. They were sorted in several ways, into concentration ranges corresponding to human consumption guidelines, into political jurisdictions and into types of bedrock geology. Overall walleye, northern pike and lake trout, usually exceeded the subsistence consumption guideline of 0.2 microg g-1 total mercury and often exceeded the higher guideline of 0.5 microg g-1 total mercury for commercial sales of fish. Mercury in burbot, another facultative predator, was often lower but several still exceeding a guideline. Arctic char collections were mostly from anadromous populations and these had very low levels of mercury, presumably reflecting marine food sources. Lake whitefish were among the cleanest fish examined with 69 of 81 collections falling in the lowest range. Most collections were from sites in sedimentary rock. However a few sites were in metamorphic, intrusive or volcanic rocks and these, taken together, tended to have a higher proportion of sites in the higher ranges of mercury. These results indicate a widespread problem with mercury in subsistence fisheries for predator species of fish with the problem being most problematic for Nunavut.
Science of The Total Environment 01/2006; 351-352:427-63. · 3.29 Impact Factor
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B M Braune,
P M Outridge,
A T Fisk,
D C G Muir,
P A Helm,
K Hobbs,
P F Hoekstra,
Z A Kuzyk,
M Kwan,
R J Letcher, W L Lockhart,
R J Norstrom,
G A Stern,
I Stirling
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ABSTRACT: This review summarizes and synthesizes the significant amount of data which was generated on mercury (Hg) and persistent organic pollutants (POPs) in Canadian Arctic marine biota since the first Canadian Arctic Contaminants Assessment Report (CACAR) was published in 1997. This recent body of work has led to a better understanding of the current levels and spatial and temporal trends of contaminants in biota, including the marine food species that northern peoples traditionally consume. Compared to other circumpolar countries, concentrations of many organochlorines (OCs) in Canadian Arctic marine biota are generally lower than in the European Arctic and eastern Greenland but are higher than in Alaska, whereas Hg concentrations are substantially higher in Canada than elsewhere. Spatial coverage of OCs in ringed seals, beluga and seabirds remains a strength of the Arctic contaminant data set for Canada. Concentrations of OCs in marine mammals and seabirds remain fairly consistent across the Canadian Arctic although subtle differences from west to east and south to north are found in the proportions of various chemicals. The most significant development since 1997 is improvement in the temporal trend data sets, thanks to the use of archived tissue samples from the 1970s and 1980s, long-term studies using archeological material, as well as the continuation of sampling. These data cover a range of species and chemicals and also include retrospective studies on new chemicals such as polybrominated diphenyl ethers. There is solid evidence in a few species (beluga, polar bear, blue mussels) that Hg at some locations has significantly increased from pre-industrial times to the present; however, the temporal trends of Hg over the past 20-30 years are inconsistent. Some animal populations exhibited significant increases in Hg whereas others did not. Therefore, it is currently not possible to determine if anthropogenic Hg is generally increasing in Canadian Arctic biota. It is also not yet possible to evaluate whether the recent Hg increases observed in some biota may be due solely to increased anthropogenic inputs or are in part the product of environmental change, e.g., climate warming. Concentrations of most "legacy" OCs (PCBs, DDT, etc.) significantly declined in Canadian Arctic biota from the 1970s to the late 1990s, and today are generally less than half the levels of the 1970s, particularly in seabirds and ringed seals. Chlorobenzenes and endosulfan were among the few OCs to show increases during this period while summation operatorHCH remained relatively constant in most species. A suite of new-use chemicals previously unreported in Arctic biota (e.g., polybrominated diphenyl ethers (PBDEs), short chain chlorinated paraffins (SCCPs), polychlorinated naphthalenes (PCNs), perfluoro-octane sulfonic acid (PFOS) and perfluorocarboxylic acids (PFCAs)) has recently been found, but there is insufficient information to assess species differences, spatial patterns or food web dynamics for these compounds. Concentrations of these new chemicals are generally lower than legacy OCs, but there is concern because some are rapidly increasing in concentration (e.g., PBDEs), while others such as PFOS have unique toxicological properties, and some were not expected to be found in the Arctic because of their supposedly low potential for long-range transport. Continuing temporal monitoring of POPs and Hg in a variety of marine biota must be a priority.
Science of The Total Environment 01/2006; 351-352:4-56. · 3.29 Impact Factor
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ABSTRACT: During the mid-1990s and through the early 2000s, researchers determined that elevated mercury concentrations were a common occurrence in predatory fish in many lakes in the Mackenzie River Basin (MRB), located in northern Canada. Here we present the results of studies investigating factors contributing to higher mercury concentrations in fish in many of these lakes. Twenty-two percent of lake trout, 33% of northern pike, and 50% of walleye populations had mean mercury concentrations >0.5 microg/g, the guideline for the commercial sale of fish. Higher mercury concentrations were strongly associated with the relatively old age of MRB predatory fish; mean age ranged from 7.6 to 24.9 years for the three species. In contrast, none of the lake trout sampled in eight lakes further south in northern Saskatchewan and Alberta had mean mercury concentrations >0.5 microg/g; fish also were younger (mean age 6 years for the 8 lakes). Mercury concentrations in MRB fish generally increased with fish length, age, and trophic feeding although the nature of these relationships varied with the lake. Mean length was a good predictor of mean mercury concentrations in walleye populations across the study lakes but not for whitefish, lake trout, and pike; age was a good predictor for lake trout and walleye. Mercury concentrations in water and invertebrates were similar to those observed in more southerly regions where fish do not have elevated mercury concentrations. Mercury concentrations tended to be higher in fish in smaller vs. larger lakes and as a probable consequence of higher summer epilimnion temperatures, which favour a higher net methylation rate, and higher mercury and methyl mercury concentrations in water which enter these lakes from the watershed. Increasing fishing pressures on MRB lakes may be a means of reducing mean fish age, improving growth rates, and decreasing mercury body burdens. Increased global warming may result in higher mercury concentrations in fish through increased water temperatures, a longer ice free season, and increased release of stored mercury from the watershed into these lakes.
Science of The Total Environment 12/2005; 351-352:479-500. · 3.29 Impact Factor
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G A Stern,
E Braekevelt,
P A Helm,
T F Bidleman,
P M Outridge, W L Lockhart,
R McNeeley,
B Rosenberg,
M G Ikonomou,
P Hamilton,
G T Tomy,
P Wilkinson
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ABSTRACT: Two annually laminated cores collected from Lake DV09 on Devon Island in May 1999 were dated using 210Pb and 137Cs, and analyzed for a variety of halogenated organic contaminants (HOCs), including polychlorinated biphenyls (PCBs), organochlorine pesticides, short-chain polychlorinated n-alkanes (sPCAs), polychlorinated dibenzo-p-dioxins and dibenzofurans (PCDD/Fs), and polybrominated diphenyl ethers (PBDEs). Dry weight HOC concentrations in Lake DV09 sediments were generally similar to other remote Arctic lakes. Maximum HOC fluxes often agreed well with production maxima, although many compound groups exhibited maxima at or near the sediment surface, much later than peak production. The lower than expected HOC concentrations in older sediment slices may be due to anaerobic degradation and possibly to dilution resulting from a temporary increase in sedimentation rate observed between the mid-1960s and 1970s. Indeed, temporal trends were more readily apparent for those compound classes when anaerobic metabolites were also analyzed, such as for DDT and toxaphene. However, it is postulated here for the first time that the maximum or increasing HOC surface fluxes observed for many of the major compound classes in DV09 sediments may be influenced by climate variation and the resulting increase in algal primary productivity which could drive an increasing rate of HOC scavenging from the water column. Both the fraction (F(TC)) and enantiomer fraction (EF) of trans-chlordane (TC) decreased significantly between 1957 and 1997, suggesting that recent inputs to the lake are from weathered chlordane sources. PCDD/Fs showed a change in sources from pentachlorophenol (PeCP) in the 1950s and 1960s to combustion sources into the 1990s. Improvements in combustion technology may be responsible for the reducing the proportion of TCDF relative to OCDD in the most recent slice.
Science of The Total Environment 05/2005; 342(1-3):223-43. · 3.29 Impact Factor
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ABSTRACT: PCBs and other persistent organochlorine (OC) pesticides were analyzed in sediment cores collected from six lakes in Yukon Territory and one in northern British Columbia, Canada, with the objective of establishing sources and historical trends of these contaminants. DDT was found to be the most prominent OC in the sediment profiles of most of the lakes. Maximum sigmaDDT levels (3.47-2680 ng g(-1) dw) were observed in sediment slices dated to the 1950s from lakes near populated areas. In contrast, in more remote lakes (Hanson, Kusawa and Lindeman), the maximum sigmaDDT concentrations were observed in the sediments dated to the 1970s. Highest sigmaPCB and sigmaDDT concentrations were measured in sediments from Watson Lake, near a suspected PCB waste disposal site and in a region where DDT was heavily applied in the 1950s and 1960s. Elevated sigmaPCB concentrations [16.1-93.6 ng g(-1) dry weight (dw)] were also observed in sediments from lakes situated near populated areas, relative to Kusawa and Lindeman (11.1 and 12.7 ng g(-1) dw, respectively). Recent sigmaPCB fluxes ranged from 621 ng m(-2) y(-1) in Kusawa Lake to 16400 ng m(-2) y(-1) in Little Atlin Lake. The extremely high sedimentation rate (2050 g m(-2) y(-1)) in glacial fed Lindeman Lake gave rise to elevated fluxes of sigmaPCB (2410 ng m(-2) y(-1)) and other OCs, despite much lower concentrations in the sediment. Levels of hexachlorocyclohexanes (sigmaHCH), chlordane-related compounds (sigmaCHL), and chlorobenzenes (sigmaCBz) were in the low ng g(-1) (dw) range in all lake sediments, similar to concentrations previously reported for Arctic lakes in Canada, indicating that their major source was long range atmospheric transport. Contamination of the lakes with PCBs and DDT near populated areas of the Yukon Territory appears to be a result of regional activities rather than long range transport and deposition. The results also point to glacial runoff as a significant source of OCs to small, high elevation lakes (Lindeman), but not to larger lakes within the Yukon River drainage basin that are also affected by glacial sources (Kusawa, Laberge).
Science of The Total Environment 01/2002; 280(1-3):17-37. · 3.29 Impact Factor
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ABSTRACT: Induction of phase I biotransformation enzymes is recognized as a hallmark response in fish exposed to coplanar PCBs. Depletions of vitamins A and E and disrupted thyroid hormone and glandular structure secondary to this induction have not yet been examined in an arctic fish species. Arctic grayling were exposed to a single oral dose of 0 (control), 10, 100 or 1000 ng 3,3',4,4'-tetrachlorobiphenyl (TCB) g(-1) bodyweight, a contaminant found in most arctic fish. After 30 and 90 days of exposure, TCB concentrations in tissues, hepatic phase I activity (as ethoxyresorufin-O-deethylase (EROD)), plasma and tissue vitamin A and E concentrations, plasma thyroid hormone levels and thyroid glandular structure were examined. Total plasma osmolality, as an indicator of overall fish health was also monitored. TCB recovery in tissues was low and extremely variable, making comparisons between intended dose groups inappropriate. Therefore, correlation analysis between actual recovered TCB concentrations and biochemical responses was employed. Hepatic EROD activity correlated strongly with liver TCB concentrations. Liver concentrations of vitamin A were altered as a function of TCB concentrations and EROD activity, but plasma vitamin A status was not affected. Vitamin E was depleted by TCB accumulation in blood and EROD induction in liver of males only at 90 days postexposure. Thyroid hormones status and glandular structure were not affected by the short duration TCB exposures used in this experiment. TCB concentrations were correlated with an elevation in plasma osmolality. Results from this experiment indicate that the vitamin status and osmoregulation of arctic grayling exposed to TCB can be compromised. Further studies of field populations exposed to this type of contaminant are warranted.
Chemosphere 11/2001; 45(2):185-93. · 3.21 Impact Factor
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ABSTRACT: There has been recent controversy over the discrimination between natural and anthropogenic loadings of mercury to lakes. Sediment core profiles have been interpreted as evidence that inputs to lakes have increased. Some investigators have argued, however, that mercury may be sufficiently mobile in sediments to generate profiles that are misinterpreted as historical records. This argument can be tested where the histories of inputs of mercury are known independently from other kinds of information. We have such cases in Canadian lakes and we have been able to assemble sediment core records for comparison with known source histories. Three cases are represented by Clay Lake in Ontario where the source was a chlor-alkali plant with a known history of mercury discharges, Giauque Lake in the Northwest Territories where mercury was used at a gold mine to extract gold from ore, and Stuart Lake in British Columbia where a mercury mine operated for a known period at Pinchi Lake, the lake immediately upstream from Stuart Lake. In these cases lake sediment cores were dated using lead-210 and cesium-137 and then slices were analysed for mercury. The histories of mercury deposition derived from the cores agreed well with the known histories of inputs.
Science of The Total Environment 11/2000; 260(1-3):171-80. · 3.29 Impact Factor
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ABSTRACT: Four types of mercury species, namely, methylmercury, organic mercury other than methylmercury, inorganic mercury, and insoluble mercury, deemed to be mercuric selenide (HgSe), were found in the liver of 45 ringed seals from the Canadian Arctic. On average, methylmercury, at 2%, made up the smallest fraction of the total mercury in the liver of these animals. Of the total mercury concentration in seal liver, 53% was insoluble mercury, estimated to be largely mercuric selenide. Other workers have found this compound to be present in mammalian liver and identified it to be HgSe. Organic mercury other than methylmercury made up 4%, and inorganic mercury 42% of the total mercury in the liver. The sum of the independently determined mercury species agreed well with the total mercury concentration in the liver. Species other than mercuric selenide are known to be toxic. Mercuric selenide, considered to be a stable end product of the demethylation process of methylmercury, although not readily eliminated from the liver, is inert and apparently non-toxic. Only approximately half of the total mercury in the liver was potentially toxic mercury. All four mercury species were positively correlated with the age of animals, the regression slope on age being 20 times larger for insoluble Hg (HgSe) than for methylmercury. A number of reported observations, such as the long half-life of Hg in liver (> or = 10 years), the dependence of Hg on age, and the often-observed one-to-one relationship between Hg and Se (on a molar basis), are readily explained by the temporal accumulation of HgSe in the liver. In the future, a more accurate assessment of the health risk to animals and humans from the consumption of contaminated animal tissues will be possible, by measuring all mercury species rather than just total mercury or methylmercury. Total mercury alone in the liver is an inadequate indicator of toxicity to animals. Methylmercury was analyzed by capillary gas-liquid chromatography with ECD detection, and the other species were operationally/experimentally defined using physical/chemical methods.
Science of The Total Environment 10/2000; 261(1-3):21-32. · 3.29 Impact Factor
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R W Macdonal,
L A Barrie,
T F Bidleman,
M L Diamond,
D J Gregor,
R G Semkin,
W M Strachan,
Y F Li,
F Wania,
M Alaee, [......],
T Harner,
J T Hoff,
L M Jantunen, W L Lockhart,
D Mackay,
D C Muir,
J Pudykiewicz,
K J Reimer,
J N Smith,
G A Stern
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ABSTRACT: Recent studies of contaminants under the Canadian Northern Contaminants Program (NCP) have substantially enhanced our understanding of the pathways by which contaminants enter Canada's Arctic and move through terrestrial and marine ecosystems there. Building on a previous review (Barrie et al., Arctic contaminants: sources, occurrence and pathways. Sci Total Environ 1992:1-74), we highlight new knowledge developed under the NCP on the sources, occurrence and pathways of contaminants (organochlorines, Hg, Pb and Cd, PAHs, artificial radionuclides). Starting from the global scale, we examine emission histories and sources for selected contaminants focussing especially on the organochlorines. Physical and chemical properties, transport processes in the environment (e.g. winds, currents, partitioning), and models are then used to identify, understand and illustrate the connection between the contaminant sources in industrial and agricultural regions to the south and the eventual arrival of contaminants in remote regions of the Arctic. Within the Arctic, we examine how contaminants impinge on marine and terrestrial pathways and how they are subsequently either removed to sinks or remain where they can enter the biosphere. As a way to focus this synthesis on key concerns of northern residents, a number of special topics are examined including: a mass balance for HCH and toxaphene (CHBs) in the Arctic Ocean; a comparison of PCB sources within Canada's Arctic (Dew Line Sites) with PCBs imported through long-range transport; an evaluation of concerns posed by three priority metals--Hg, Pb and Cd; an evaluation of the risks from artificial radionuclides in the ocean; a review of what is known about new-generation pesticides that are replacing the organochlorines; and a comparison of natural vs. anthropogenic sources of PAH in the Arctic. The research and syntheses provide compelling evidence for close connectivity between the global emission of contaminants from industrial and agricultural activities and the Arctic. For semi-volatile compounds that partition strongly into cold water (e.g. HCH) we have seen an inevitable loading of Arctic aquatic reservoirs. Drastic HCH emission reductions have been rapidly followed by reduced atmospheric burdens with the result that the major reservoir and transport agent has become the ocean. In the Arctic, it will take decades for the upper ocean to clear itself of HCH. For compounds that partition strongly onto particles, and for which the soil reservoir is most important (e.g. PCBs), we have seen a delay in their arrival in the Arctic and some fractionation toward more volatile compounds (e.g. lower-chlorinated PCBs). Despite banning the production of PCB in the 1970s, and despite decreases of PCBs in environmental compartments in temperate regions, the Arctic presently shows little evidence of reduced PCB loadings. We anticipate a delay in PCB reductions in the Arctic and environmental lifetimes measured in decades. Although artificial radionuclides have caused great concern due to their direct disposal on Russian Shelves, they are found to pose little threat to Canadian waters and, indeed, much of the radionuclide inventory can be explained as remnant global fallout, which was sharply curtailed in the 1960s, and waste emissions released under license by the European reprocessing plants. Although Cd poses a human dietary concern both for terrestrial and marine mammals, we find little evidence that Cd in marine systems has been impacted by human activities. There is evidence of contaminant Pb in the Arctic, but loadings appear presently to be decreasing due to source controls (e.g. removal of Pb from gasoline) in Europe and North America. Of the metals, Hg provokes the greatest concern; loadings appear to be increasing in the Arctic due to global human activities, but such loadings are not evenly distributed nor are the pathways by which they enter and move within the Arctic well understood.
Science of The Total Environment 07/2000; 254(2-3):93-234. · 3.29 Impact Factor
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ABSTRACT: Sediment cores from six lakes in Canada ranging from 49°N to 81°N were analyzed for C10−C13 polychlorinated n-alkanes (PCAs) with the intent of (i) examining the depositional trends with increasing latitude, (ii) studying the historical profiles and fluxes of PCAs in dated sediment slices, and (iii) investigating possible in situ degradation. Sediment slices were dated using 210Pb and 137Cs, and extracts were analyzed for PCA concentrations by high resolution gas chromatography electron capture negative ion high resolution mass spectrometry (HRGC-ECNI/HRMS) in the selected ion monitoring (SIM) mode. Concentrations of total PCAs in surface sediments declined significantly from 135 ng/g (dry weight (dw)) in sediments from the southern basin of Lake Winnipeg (50°N/96°W, Manitoba) to 4.52 ng/g in Hazen Lake (81°N/71°W, high Arctic); corresponding surficial fluxes were 147 and 0.9 μg/m2 yr, respectively. The high flux of PCAs to the south Lake Winnipeg basin suggests local contamination. This was confirmed by analyzing water collected from the Red River, a river that discharges into the southern basin of Lake Winnipeg, in which elevated levels of PCAs were detected (0.02−0.05 μg/L). The surficial flux of PCAs to Fox Lake (61°N/135°W), a subarctic lake in the Yukon, was also high, 34 μg/m2 yr. Much lower fluxes were found in Lake Nipigon (49°N/89°W, N. Ontario), 3 μg/m2 yr, the northern basin of Lake Winnipeg (52°N/98°W, Manitoba), 4 μg/m2 yr, and to Ya Ya Lake (69°N/134°W, Arctic) 0.45 μg/m2 yr. The remote locations of Hazen and Ya Ya Lakes and the low levels of PCAs observed in their corresponding sediment slices are consistent with long-range atmospheric transport. The profiles of PCAs in the midcontinental lakes showed maxima in slices dated from the early 1980s to the 1990s while that of ΣDDT showed a maxima in the 1960s. The presence of PCAs in surface sediments over a wide geographic area, including the Canadian Arctic, suggests that these compounds, which are components of commercial short chain chlorinated paraffins, are regionally and globally distributed by long-range atmospheric transport.
07/1999;
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ABSTRACT: Concentrations of methylmercury, total mercury and selenium in marine mammal tissues were determined in liver, muscle, skin (muktuk) and blubber of belugas, ringed seals and narwhal, using atomic absorption and capillary gas chromatography with ECD detection. Mean MeHg levels in the types of tissues analysed, except blubber, generally exceeded the Canadian Federal Consumption Guideline for mercury in fish (0.5 micrograms/g wet wt.). A spatial trend of higher MeHg levels in western compared to eastern Arctic belugas and ringed seals was found which followed a similar trend observed for total mercury. Factors which could explain this trend are discussed. Robust linear regression of MeHg on total Hg and MeHg on age of animals was performed and a strong correlation between the two variables was found in each case. The ratio of MeHg to total mercury as indicated by the regression coefficients was close to one for muscle and skin (muktuk) while for liver it was < 1. The mean percentage of MeHg in the liver of marine mammals was 3-12% of the total Hg in this tissue depending on species and location. It is postulated that the formation and deposition of mercuric selenide in the liver is part of the demethylation process in this tissue. This is based on the relatively low fraction of MeHg in the liver not withstanding the fact that the predominant form of mercury taken up via food is MeHg. The long half-life for total mercury and the relatively short half-life for MeHg in this organ are in accord with this postulate as is the 1:1 stoichiometric relationship between mercury and selenium in the liver.
Science of The Total Environment 07/1998; 218(1):19-31. · 3.29 Impact Factor
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W L Lockhart
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ABSTRACT: Chemical residue analyses have established beyond doubt that arctic ecosystems are contaminated with low concentrations of several contaminants. The sources of these vary, but for many, the principal source is atmospheric deposition as a result of widespread dispersal by air masses carrying materials from lower latitudes. The principal problem discussed here is how to determine whether there are biological implications associated with the contaminants. For the most part, concentrations are below those found in more temperate regions where similar questions have been asked. Little experimental toxicology has been done with arctic species, and relatively little has been done in environmental toxicology in general to express biological responses in terms of body residues. It is argued that chemical residue studies are not, in themselves, evidence of biological responses. The effects of greatest interest are those at ecological levels, but ecological surveys that might detect biological changes have little power to test for cause-effect linkages between the contaminants and the changes observed. The emerging approach of biomarkers or bioindicators seems to offer the greatest promise for efforts to determine whether arctic contaminants have biological implications.
Science of The Total Environment 02/1995; 160-161:631-41. · 3.29 Impact Factor
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ABSTRACT: Sediment cores collected from several lakes in northern Canada have been analyzed for mercury and several other chemical contaminants. Sites ranged from the Experimental Lakes Area of northwestern Ontario, north to Cornwallis Island, and west to the southern Yukon. Cores were sliced at sites of collection and individual slices were freeze dried and analyzed for Pb-210 and Cs-137 to estimate average time intervals of deposition. The earliest date estimated by Pb-210 was about 1850, and mercury concentrations in some lakes were clearly increasing before then, assuming no vertical movements of mercury within the sediments. Extrapolation of dates downward to deeper slices, assuming a constant sedimentation rate, indicated that in some lakes mercury inputs increased slowly even in the 1500's, more rapidly after 1750, and more rapidly yet over the current century. These increases are interpreted as increased fluxes of mercury to the lakes as a result of long-range transport of atmospheric mercury, since there are no local industrial sources of mercury. Slices taken near the bottom of a core are taken to estimate the geological component while elevations in excess of that in surface slices are taken to represent contamination from fallout. This partitioning suggests that sediments in the eastern Northwest Territories are dominated by pollution, while those from the western Northwest Territories are influenced more by their geological settings. Two cores from Hudson Bay suggest that mercury is increasing there too, but has not yet exceeded geological sources. Mercury shows little or no tendency to decline in the most recent slices; indicating that inputs of mercury remain at or near their historical maxima. Given relatively high and continuing inputs of mercury to northern lakes it seems likely that some portion of that mercury may find its way into the food chain, hence the long-term prospect is for increasing levels of mercury in northern fish.
Water Air and Soil Pollution 01/1995; 80(1):603-610. · 1.63 Impact Factor
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ABSTRACT: Mercury concentrations were determined in liver, kidney and muscle of belugas, narwhal, whitebeaked dolphins, pilot whales, ringed seals, harp seals and walrus. Tissue collections and analyses were performed largely over the past 10 years. Sampling sites ranged across the Canadian Arctic from the Mackenzie Delta and Banks Island in the west, Grise Fjord in the north, the Atlantic coast in the east and south. High Hg levels in the liver of ringed seals from the western Arctic, collected in 1987 and 1988 were similar to previously-reported values for ringed seals collected in 1973 and 1972 from the same area. Comparison among different marine mammal species showed substantial inherent differences in Hg levels among different species. White-beaked dolphins and walrus had much less Hg than pilot whales. A comparison of Hg levels in ringed seals from locations across the Arctic and Hudson Bay showed that Hg was generally higher in ringed seals from the western than the eastern Arctic, indicating a possible influence of the different geological settings in the eastern and western Arctic. The effect of age was considered in these comparisons. A similar, but less pronounced effect was noted for belugas, with some possible anthropogenic influence on animals in Hudson Bay. The spatial trend in Hg levels in animals appeared to be largely present-day background concentration reflecting geological differences between the eastern and western Arctic. Higher Hg concentration were present in surficial sediments and coastal waters in the western Arctic than the eastern Arctic in accord with the Hg trend observed in seals and belugas.
Water Air and Soil Pollution 01/1995; 80(1):683-693. · 1.63 Impact Factor
