Comparison of contaminants from different trophic levels and ecosystems

The present paper provides an overview of the priority contaminants and media from the Greenland part of the Arctic Monitoring and Assessment Program. Levels and accumulation patterns of heavy metals, POPs and a radionuclide (137Cs) are compared from the terrestrial, freshwater and marine ecosystems. Of the nine compounds presented, seven (Cd, Hg, Se, sigma PCB, sigma DDT, sigma HCH, HCB) increased in concentration towards higher trophic levels. For these contaminants the concentrations in soil and aquatic sediment were in the same order of magnitude, whereas the concentrations in marine biota were higher than found in the freshwater and terrestrial ecosystems probably due to the presence of longer food chains. Pb and 137Cs showed the reverse pattern compared with the other compounds. The concentrations in soil and aquatic sediments decreased in the order terrestrial, freshwater and marine ecosystems, which was reflected in the biota as well. Reindeer had similar or lower levels of Pb and 137Cs than lichens. Levels of Pb and 137Cs in marine biota did not show the same clear increase towards higher trophic as found for the other analysed compounds. Greenland Inuit contains considerably less mercury but higher levels of sigma PCB, sigma DDT and HCB than other Arctic marine top consumers.     

Persistent organochlorine pollutants in ringed seals and polar bears collected from northern Alaska

Blubber samples from ringed seal (Phoca hispida; n = 8) and polar bear subcutaneous fat (Ursus maritimus; n = 5) were collected near Barrow, Alaska in 1996 as part of the Alaska Marine Mammal Tissue Archival Project (AMMTAP) and retained in the National Biomonitoring Specimen Bank at the National Institute of Standards and Technology in Gaithersburg, Maryland (USA). The samples were analyzed for a variety of persistent organochlorine pollutants (POPs) including polychlorinated biphenyls (PCBs), hexachlorocyclohexanes (HCHs), chlordane and metabolites, hexachlorobenzene (HCB) and DDTs and metabolites. The geometric mean, on a wet mass basis, of sigmaPCBs (sum of 29 congeners and congener groups) were 732+/-282 ng/g (1 S.D.) in seals and 3395+/-1442 ng/g in polar bears. The geometric mean of sigmaDDTs, sigmaHCHs (alpha-, beta- and gamma- HCH) and HCB concentrations (wet mass basis) in seals and bears were 562+/-261 ng/g vs. 74.8+/-39 ng/g, 380+/-213 ng/g vs. 515 ng/g, and 17.4+/-10.1 ng/g vs. 183+/-153 ng/g, respectively. The geometric mean sum of chlordane (sigmachlordane, sum of cis- and trans-chlordane, cis- and trans-nonachlor, oxychlordane and heptachlor epoxide) and dieldrin concentrations in ringed seals and polar bears were 753+/-617 ng/g vs. 720+/-315 ng/g and 38.6+/-22.8 ng/g vs. 130+/-65 ng/g, respectively. Apparent bioaccumulation factors (polar bear/ringed seal POP concentrations) were lower in the animals sampled near Barrow, Alaska than in those from locations in the Canadian Arctic. This suggests that polar bears are also preying on marine mammals from lower trophic levels than the ringed seals with correspondingly lower organochlorine levels, such as bowhead whale carcasses. PCB congener patterns in the samples demonstrated the metabolism of certain PCB congeners in the polar bear relative to the ringed seal in agreement with previous studies. Regional comparisons of animals collected in Alaska and Arctic Canada are presented.     

Uncertainty and variability in risk from trophic transfer of contaminants in dredged sediments.

The risks associated with bioaccumulative contaminants must be considered when evaluating dredged material disposal alternatives. The bioaccumulation of organochlorines and other contaminants by higher trophic level organisms represents one of the most significant sources of uncertainty in risk assessment. Both population variability (e.g. true population heterogeneity in body weight, lipid content, etc.) and uncertainty (e.g. measurement error) in trophic transfer can lead to large errors in predicted risk values for ecological receptors. This paper describes and quantitatively evaluates sources of uncertainty and variability in estimating the risk to an ecological receptor (osprey) from the trophic transfer of polychlorinated biphenyls (PCBs) in sediments from the New York-New Jersey (NY-NJ) Harbor. The distribution of toxicity quotients is obtained using a food chain model for the osprey and specifying distributions for input parameters, which are disaggregated to represent either uncertainty or variability. PCB concentrations in sediment and water are treated as predominantly uncertain, whereas lipid content in fish, feeding preferences, and fish weight are assumed to contribute primarily to population variability in PCB accumulation. The analysis shows that point estimates of reasonable maximum exposure (RME) exceed the uncertainty bounds on the 95th percentile of variability. The analysis also shows that uncertainties in the sediment and water contaminant concentrations contribute more to the range of risk estimates than does the variability in the population exposure parameters. The separation of uncertainty and variability in food chain models can help to support management decisions regarding dredged material disposal by providing a quantitative expression of the confidence in ecological risk estimates. A rationale is provided for the distinction between uncertain and variable parameters based on management goals and data availability.     

Concentrations and patterns of organochlorine contaminants in white whales (Delphinapterus leucas) from Svalbard, Norway

Blubber was collected from live-captured, adult male white whales (Delphinapterus leucas) from Svalbard, Norway, and analysed for levels and patterns of organochlorine (OC) contaminants. The OC compounds analysed were HCB, dieldrin, sigmaHCH (alpha-HCH, beta-HCH and gamma-HCH), sigmaChl (heptachlor epoxide, oxychlordane, cis-chlordane, trans-nonachlor, and cis-nonachlor), sigmaDDT (pp'-DDT, pp'-DDE and pp'-DDD) and sigmaPCB (27 PCB congeners). The major OC compounds detected in the blubber were sigmaPCB (5103+/-1874 ng/g l.w.) and sigmaDDT (5108+/-1089 ng/g l.w.), which made up 70% of the sigmaOC. These compounds were followed in prevalence by sigmaChl (2872+/-1177 ng/g l.w.), which contributed 20% of the sigmaOC burden. SigmaHCH, HCB and dieldrin were present, but at low concentrations. This OC pattern is typical of top predators in Arctic marine food chains. OC levels in white whales from Svalbard are lower than white whales from the St Lawrence River in Canada and are generally similar to values reported previously for other Arctic white whale stocks. Some geographic patterns in relative prevalence of various OC compounds appear to be quite consistent among various marine mammal species in the Arctic. PCB and DDT concentrations in Svalbard's white whales are below the levels that are thought to have negative effects on reproduction or the immune system.     

Organic contaminants in the aquatic environment I. Sources and occurrence

Literature pertaining to the sources and occurrence of organic compounds in raw, potable and waste waters is reviewed. The introduction of organic micropollutants into the hydrological cycle is considered in terms of both point and non-point source discharges and the individual industrial and domestic sources of particular classes of organic chemicals are assessed. The occurrence in waters and waste waters of a wide variety of organic contaminants has been evaluated with regard to their concentrations in particular aqueous samples and frequency of occurrence. Although specific sources are known to be responsible for the addition of certain organic compounds to water and waste water, the occurrence of particular compounds cannot always be related to a particular source. In addition, it is evident that the reported occurrence of many organic contaminants has been limited by the capabilities of presently available analytical techniques.With the number of organic chemicals in use increasing, the potential for continued contamination of water resources exists. The implications for water quality and the possible effects generated by the introduction of organic compounds into the hydrological cycle on water re-use operations are discussed.     

Environmental contaminants and biomarker responses in fish from the Columbia River and its tributaries: spatial and temporal trends

Fish were collected from 16 sites on rivers in the Columbia River Basin (CRB) from September 1997 to April 1998 to document temporal and spatial trends in the concentrations of accumulative contaminants and to assess contaminant effects on the fish. Sites were located on the mainstem of the Columbia River and on the Snake, Willamette, Yakima, Salmon, and Flathead Rivers. Common carp (Cyprinus carpio), black bass (Micropterus sp.), and largescale sucker (Catostomus macrocheilus) were the targeted species. Fish were field-examined for external and internal lesions, selected organs were weighed to compute somatic indices, and tissue and fluid samples were preserved for fish health and reproductive biomarker analyses. Composite samples of whole fish, grouped by species and gender, from each site were analyzed for organochlorine and elemental contaminants using instrumental methods and for 2,3,7,8-tetrachloro dibenzo-p-dioxin-like activity (TCDD-EQ) using the H4IIE rat hepatoma cell bioassay. Overall, pesticide concentrations were greatest in fish from lower CRB sites and elemental concentrations were greatest in fish from upper CRB sites. These patterns reflected land uses. Lead (Pb) concentrations in fish from the Columbia River at Northport and Grand Coulee, Washington (WA) exceeded fish and wildlife toxicity thresholds (>0.4 microg/g). Selenium (Se) concentrations in fish from the Salmon River at Riggins, Idaho (ID), the Columbia River at Vernita Bridge, WA, and the Yakima River at Granger, WA exceeded toxicity thresholds for piscivorous wildlife (>0.6 microg/g). Mercury (Hg) concentrations in fish were elevated throughout the basin but were greatest (>0.4 microg/g) in predatory fish from the Salmon River at Riggins, ID, the Yakima River at Granger, WA, and the Columbia River at Warrendale, Oregon (OR). Residues of p,p'-DDE were greatest (>0.8 microg/g) in fish from agricultural areas of the Snake, Yakima, and Columbia River basins but were not detected in upper CRB fish. Other organochlorine pesticides did not exceed toxicity thresholds in fish or were detected infrequently. Total polychlorinated biphenyls (PCBs; >0.11 microg/g) and TCDD-EQs (>5 pg/g) exceeded wildlife guidelines in fish from the middle and lower CRB, and ethoxyresorufin O-deethylase (EROD) activity was also elevated at many of the same sites. Temporal trend analysis indicated decreasing or stable concentrations of Pb, Se, Hg, p,p'-DDE, and PCBs at most sites where historical data were available. Altered biomarkers were noted in fish throughout the CRB. Fish from some stations had responded to chronic contaminant exposure as indicated by fish health and reproductive biomarker results. Although most fish from some sites had grossly visible external or internal lesions, histopathological analysis determined these to be inflammatory responses associated with helminth or myxosporidian parasites. Many largescale sucker from the Columbia River at Northport and Grand Coulee, WA had external lesions and enlarged spleens, which were likely associated with infections. Intersex male smallmouth bass (Micropterus dolomieu) were found in the Snake River at Lewiston, ID and the Columbia River at Warrendale, OR. Male bass, carp, and largescale sucker containing low concentrations of vitellogenin were common in the CRB, and comparatively high concentrations (>0.3 mg/mL) were measured in male fish from the Flathead River at Creston, Montana, the Snake River at Ice Harbor Dam, WA, and the Columbia River at Vernita Bridge, WA and Warrendale, OR. Results from our study and other investigations indicate that continued monitoring in the CRB is warranted to identify consistently degraded sites and those with emerging problems.     

Cadmium,zinc, copper,arsenic, selenium and mercury in seabirds from the Barents Sea: levels,inter-specific and geographical differences

Trace elements Cd, Zn, Cu, As, Se and Hg were analysed in muscle and liver of Brünnich's guillemot, Common guillemot, Puffin, Black guillemot, Little auk, Razorbill, Common eider, King eider, Glaucous gull, Herring gull, Black-legged kittiwake, Northern fulmar and Arctic tern collected in 1991-1992 at the main breeding colonies in the Barents Sea. The highest levels of the most toxic elements Cd and Hg were found in birds nesting north of Spitsbergen. Extremely high levels of As were detected in tissues of all seabird species collected at colonies in Chernaya Guba (Novaya Zemlya), where nuclear tests were carried out in the 1960s. In general, levels of all of the trace elements in the Barents Sea seabirds were similar or lower in comparison with those reported for the same seabird species from the other Arctic areas. Data on metallothionein concentrations in different seabird species need to be collected in order to understand the mechanism of bioaccumulation and possible toxic effects of trace elements in Arctic seabirds.     

Sources and trends of environmental mercury emissions in Asia

This paper focuses on environmental mercury emissions in Asia and elaborates its probable trend in the future and associated implications given the anticipated socioeconomic outlook and other macro-environmental factors. Among the various regions, Asia has become the largest contributor of anthropogenic atmospheric Hg, responsible for over half of the global emission. In the next few decades, a significant increase in anthropogenic Hg emissions in Asia is likely owing to rapid economic and industrial development, unless drastic measures are taken. In particular, the dominance of Asia in some Hg-emitting industries, such as coal combustion, steel production and gold mining, provokes a serious environmental concern over their potential contributions of incidental Hg in the region. Moreover, the increasing prevalence of electrical and electronic manufacturing industry as a user and a contributor of Hg in Asia is also worrying. Specifically, disposal of obsolete electrical and electronic wastes represents a phenomenon increasingly encountered in Asia. In addition to escalating anthropogenic Hg emissions in Asia, associated environmental and health implications may also exacerbate in the region for the probable effects of a unique combination of climatic (e.g. subtropical climate), environmental (e.g. acid rain) and socioeconomic factors (e.g. high population density). Hence, much effort is still needed to understand the role of Asia in global Hg cycle and associated environmental and health effects in the region.     

Organochlorine contaminants in endangered Steller sea lion pups (Eumetopias jubatus) from western Alaska and the Russian Far East

Investigations into the cause of the Steller sea lion population decline have focused on numerous factors, including exposure to toxic contaminants such as organochlorines (OCs). OCs, such as polychlorinated biphenyls (PCBs), 1,1,1-trichloro-2,2-bis(p-chlorophenyl)ethane, or dichlorodiphenyltrichloroethane (DDT), have been associated with various biological effects in marine mammals. We measured these compounds in whole blood of free-ranging Steller sea lion pups in order to determine the extent and magnitude of contamination across their geographical range. Of 212 pups analyzed for OCs, 76 pups (36 females and 40 males) were from western Alaska and the other 136 (63 females and 73 males) were from the Russian Far East. Concentrations of summation SigmaPCBs in the whole blood of pups from western Alaska ranged from 0.21 to 13 ng/g wet weight with a mean of 2.1+/-0.27 ng/g wet weight. In the Russian animals, summation SigmaPCB concentrations in the whole blood of pups ranged from 0.33 to 36 ng/g wet weight with a mean of 4.3+/-0.44 ng/g wet weight. summation SigmaDDT concentrations in the whole blood of pups from western Alaska ranged from 0.18 to 11 ng/g wet weight with a mean of 1.6+/-0.23 ng/g wet weight. In Russia, summation SigmaDDT in the whole blood of pups ranged from undetectable to 26 ng/g wet weight with a mean of 3.3+/-0.36 ng/g wet weight. Average OC concentrations were significantly higher in the blood of Russian animals compared to western Alaska (for PCBs and DDTs, p<0.001) and in both areas females had higher concentrations than males. Male pups from western Alaska had significantly lower levels of summation SigmaPCBs and summation SigmaDDT when compared to male pups from Russia (for PCBs and DDTs p<0.001). Female pups from western Alaska were significantly lower in summation SigmaPCBs than Russian female pups (for PCBs p=0.009) as were female pups for summation SigmaDDT levels between areas (for DDTs p=0.026). OC contaminants data indicate that Steller sea lion pups have measurable concentrations of these synthetic chemicals. While any physiological effect and the specific role these chemicals may have in either the decline or the failure of the endangered Steller sea lion population to recover needs to be further investigated, this study indicates specific areas and animals that may be most at risk.     

Fate of organochlorine contaminants in arctic and subarctic lakes estimated by mass balance modelling

Elevated concentrations of some persistent organic pollutants (POPs) in fish from arctic and subarctic lakes have been hypothesized to be due to processes within food webs and fish physiology. We investigated limnological processes and contaminant chemistry as explanations of these elevated concentrations by developing and applying fugacity-based mass balance models to a relatively small lake in the high arctic and a series of larger lakes in the southern Yukon River basin. The results indicate that high arctic lakes are transient and inefficient sinks for POPs. The mobility of POPs in high arctic lakes is conferred by their hydrologic regime (i.e. partial through flow of melt water loadings) and minimal scavenging and retention in sediments due to extremely low organic carbon in settling and sediment particles. Contaminant dynamics in lakes of the south Yukon River basin are governed by hydrology (i.e., water residence time), because, similarly to high arctic lakes, most of the contaminant inventory resides in the water column due to inefficient scavenging by settling particles. For the less persistent compounds, long water residence time shifts the major loss process from export to degradation. Model results also suggest relatively short degradative half-lives of the hexachlorocyclohexanes (sum of HCHs) and endosulfan, particularly in high arctic Amituk Lake.     

Locational differences in heavy metals and metalloids in Pacific Blue Mussels Mytilus [edulis] trossulus from Adak Island in the Aleutian Chain, Alaska

Increasingly there is a need to implement biomonitoring plans that can be sustained cost-effectively, focusing on single widespread (or closely-related species) in different parts of the world to detect exposure, potential damage to the organisms themselves, and risk to their consumers, including humans. Blue Mussels (Mytilus edulis and its relatives) have been widely used for environmental monitoring. One successful program that has achieved great coverage in time and space is "Mussel Watch", and related programs exist in several regions. In this paper we use the Pacific Blue Mussel Mytilus [edulis] trossulus collected from five locations on Adak Island in the Aleutian Chain to examine five heavy metals and two metalloids, to test for locational differences as a function of anthropogenic activities, and to consider potential human health risks. Until the late 1990s Adak hosted a large U.S. military base, with multiple areas of contamination, some of which have been remediated. In June 2004 we identified four presumably human-impacted sites and a presumed unimpacted reference site, the latter on Clam Lagoon Beach, about 3 km from former military activity. No single site had the highest level of more than two metals, and the reference site had the highest levels of chromium and manganese. We subsequently found historic records of a former landfill within 1 km of the reference site. All of the locational differences were less than an order of magnitude, the greatest difference between the highest and lowest values being 4.5 times for lead. The highest correlations were between mercury and arsenic, mercury and lead, arsenic and lead, and chromium and manganese. Shell length was a better indicator of metals' levels than soft body weight, but the relationships were weak. There was no significant correlation between body size or weight with arsenic, lead, or selenium levels. There is substantial comparative data on these metals in mussels. Our results from Adak are generally within the range of mean values reported in the literature, except for the consistently elevated levels of chromium.     

Risk to breeding success of fish-eating Ardeids due to persistent organic contaminants in Hong Kong: evidence from organochlorine compounds in eggs

Eggs of two Ardeid species, the Little Egret (Egretta garzetta) and the Black-crowned Night Heron (Nycticorax nycticorax), were collected from two egretries located in the New Territories of Hong Kong with one located near the internationally acclaimed wetland reserve, the Mai Po Marshes, and the other in a remote site (A Chau). The eggs were analysed for organochlorine (OC) compounds including the DDTs, PCBs, hexachlorocyclohexanes (HCHs) and the chlordanes (CHLs). All of the OCs under investigation were detected in the eggs of both species with significantly higher levels in the Little Egret (DDTs, 560-2200; PCBs, 270-1700; CHLs, 81-470 ng g(-1) wet weight) than the Night Heron (DDTs, 210-1200; PCBs, 85-600; CHLs 59-75 ng g(-1) wet weight). The DDTs consisted mainly of DDE with levels ranging from 85% to 95% of the total. The HCHs were at about the same levels in both species (8.4-30 ng g(-1) wet weight). All of the OCs had linear concentration probability distributions on a log-normal basis which were used to evaluate exposure associated with these compounds as part of a probabilistic risk analysis. A linear dose/response relationship for the percentage reduction in the survival of young associated with DDE in eggs was developed. This probabilistic relationship was used to establish the threshold level (1000 ng g(-1) wet weight) at which there was a significant level of reduction in the survival of young above zero and the variability in DDE concentrations at this effect level. Using a threshold level of 1000 ng g(-1), the calculated Risk Quotient (RQ) had a 12.4% probability of RQ exceeding unity with the Night Heron, and 40.9% with the Little Egret. These results indicate that the DDTs in eggs would be expected to be associated with adverse effects on the survival of young of both species, particularly the Little Egret.     

A comparison of the non-essential elements cadmium, mercury, and lead found in fish and sediment from Alaska and California

Concentrations of three non-essential elements (cadmium (Cd), mercury (Hg), and lead (Pb)) were determined in sediment and fish from several locations in Alaska (AK) and California (CA) and used to examine differences in bioaccumulation within and between geographic locations. We analyzed tissue (liver, muscle, gill, and stomach contents) from white croaker (Genyonemus lineatus) and English sole (Pleuronectes vetulus) in California and flathead sole (Hippoglossoides elassodon) in Alaska, in addition to several species of invertebrates (mercury only). As found in previous work on arsenic (As) [Meador et al., 2004], Cd in fish liver exhibited a negative correlation with sediment concentrations. No such correlations were found for Hg and Pb when fish liver and sediment were compared; however, these metals did exhibit a positive relationship between liver and organic carbon normalized sediment concentrations, but only for the CA sites. Sediment concentrations of Hg at the AK sites were lower than those for the CA sites; however, AK invertebrates generally bioaccumulated more Hg than CA invertebrates. Conversely, Hg bioaccumulation was higher in CA fish. Even though ratios of total metal/acid volatile sulfides (AVS) in sediment were one to two orders of magnitude higher for the AK sites, bioaccumulation of these elements was much higher in fish from the CA sites. Bioaccumulation factors ([liver]/[sediment]) (BAFs) were highest at relatively clean sites (Bodega Bay and Monterey), indicating that elements were more bioavailable at these sites than from more contaminated locations. The observation of high BAFs for As in fish from Alaska and low BAFs for the California fish, but reversed for Cd, Hg, and Pb in this study, implies that differences in fish species are less important than the unique geochemical features at each site that control bioavailability and bioaccumulation and the potential sources for each element. Additionally, these data were also used to examine the metal depletion hypothesis, which describes the inverse relationship between elements and organic contaminants documented in some monitoring studies. Our results suggest that the enhanced bioavailability of the metals at some uncontaminated sites is the main determinant for the inverse correlation between metal and organic contaminants in tissue.     

Geographic variation in polychorinated biphenyl and organochlorine pesticide concentrations in the blubber of bottlenose dolphins from the US Atlantic coast

Concentrations of polychorinated biphenyls (PCBs) and other organochlorine contaminants (OCs) were measured in blubber collected from live bottlenose dolphins (Tursiops truncatus) at three sites along the United States Atlantic coast. Dolphins were sampled via surgical biopsy during capture-release studies near Charleston, South Carolina and Beaufort, North Carolina. Additional animals were sampled using remote biopsy techniques in estuarine waters near Charleston and from the Indian River Lagoon, Florida. Overall concentrations of major contaminant groups were found to vary between sites and mean concentrations of most OCs from male dolphins in the Indian River Lagoon were less than half of those measured from Charleston and Beaufort males. Geometric mean total PCB concentrations were 30, 27 and 14 microg/g lipid for male dolphins sampled in Beaufort, Charleston and the Indian River Lagoon, respectively. Significant variation related to sex- and age-class, as well as geographic sampling location, was seen in the PCB congener profiles. The measured PCB concentrations, although lower than those reported for stranded animals from the 1987/1988 epizootic along the United States mid-Atlantic coast, are sufficiently high to warrant concern for the health of dolphins from the sampled populations, particularly the animals near Charleston and Beaufort.     

Levels and spatial and temporal trends of contaminants in Greenland biota: an updated review

Knowledge of contaminant levels in Greenland biota has increased substantially in recent years, particularly for persistent organic pollutants. This paper reviews and updates knowledge of spatial and temporal trends of Cd, Hg and organochlorines (PCBs, DDTs, HCHs, HCB and chlordane-related compounds) in Greenland terrestrial, freshwater and marine biota. The most comprehensive studies of spatial trends of Cd and Hg in the terrestrial ecosystem concern lichens, with relatively complete coverage, and caribou (Rangifer tarandus), with coverage mainly in different regions of central West Greenland and Southwest Greenland. The Arctic char (Salvelinus alpinus) is the only freshwater organism for which studies of spatial trends of Hg levels have been completed. Information on spatial trends of Cd and Hg in the marine environment is available from studies of fish, seabirds, ringed seals (Phoca hispida) and polar bears (Ursus maritimus). Geographical patterns of Cd and Hg in Greenland biota were not always consistent among different species or different studies. In landlocked Arctic char the concentrations of Hg decreased from south to north. In marine animals levels of Hg tended to be higher in East Greenland than in West Greenland and Cd levels were highest in biota from Disko Island in central West Greenland. The observed regional differences are difficult to explain but in most cases the causes appear to be natural rather than anthropogenic. Only a few time series covering the last 20 years exist for Cd and Hg. The one time series indicating a temporal change is for ringed seals in Northwest Greenland, which shows an increasing trend of Hg and a decreasing trend of Cd since 1984. Whether the changes reflect anthropogenic inputs, seal behaviour or other environmental factors is unknown. The most significant new insights have concerned organochlorines. In general, levels of these compounds were very low in terrestrial biota compared to marine species. Concentrations in landlocked Arctic char were highest in Southeast Greenland and lowest in Northwest and Northeast Greenland. Marine species from East Greenland had consistently higher levels of SigmaPCB, SigmaDDT and SigmaHCH than marine species from West Greenland. Very few data exist to evaluate temporal changes of organochlorine levels in Greenland biota, and this is the most significant knowledge gap at present. The most pronounced change observed was a decrease of 78% in SigmaPCB levels in polar bears from East Greenland from 1990 to 2000. Levels of SigmaHCH in shorthorn sculpins (Myoxocephalus scorpius) and seals from both central West Greenland and central East Greenland appear to have decreased since 1994. Increasing trends of SigmaDDT from 1994 until now were found in both sexes of seals as well as in male sculpins from central West Greenland.     

Inter- and intraclutch variation in egg mercury levels in marine bird species from the Canadian Arctic

Mercury (Hg) is a toxic metal that has been of increasing concern in the Canadian Arctic. We measured total Hg in eggs of three marine birds (Arctic terns Sterna paradisaea, common eiders Somateria mollissima borealis, long-tailed ducks Clangula hyemalis) that breed in the Canadian Arctic, to compare Hg laying order effects from the same clutch and to examine Hg among species. Early-laid eggs of all three species had 24-48% higher Hg concentrations than late laid eggs. Arctic terns had approximately twice the concentration of Hg in their eggs as the two duck species, and Hg in eider eggs from the High Arctic was higher than Hg in eggs from the Low Arctic. Higher Hg in tern eggs was consistent with this species occupying a higher trophic position in marine food webs, as indicated by stable nitrogen isotope (δ¹⁵N) values. The egg-laying sequence may need to be considered for Hg biomonitoring studies where small samples sizes are planned, and early eggs may be preferable for such studies since early eggs may be more representative of potential maximum levels of Hg in the marine food webs.     

Environmental contaminants and biomarker responses in fish from the Rio Grande and its U.S. tributaries: spatial and temporal trends

We collected, examined, and analyzed 368 fish of seven species from 10 sites on rivers of the Rio Grande Basin (RGB) during late 1997 and early 1998 to document temporal and geographic trends in the concentrations of accumulative contaminants and to assess contaminant effects on the fish. Sites were located on the mainstem of the Rio Grande and on the Arroyo Colorado and Pecos River in Texas (TX), New Mexico (NM), and Colorado. Common carp (Cyprinus carpio) and largemouth bass (Micropterus salmoides) were the targeted species. Fish were examined in the field for internal and external visible gross lesions, selected organs were weighed to compute ponderal and organosomatic indices, and samples of tissues and fluids were obtained and preserved for analysis of fish health and reproductive biomarkers. Whole fish from each station were composited by species and gender and analyzed for organochlorine chemical residues and elemental contaminants using instrumental methods, and for 2,3,7,8-tetrachloro dibenzo-p-dioxin-like activity (TCDD-EQ) using the H4IIE rat hepatoma cell bioassay. Overall, fish from lower RGB stations contained greater concentrations of organochlorine pesticide residues and appeared to be less healthy than those from sites in the central and upper parts of the basin, as indicated by a general gradient of residue concentrations and biomarker responses. A minimal number of altered biomarkers and few or no elevated contaminant concentrations were noted in fish from the upper RGB. The exception was elevated concentrations [up to 0.46 microg/g wet-weight (ww)] of total mercury (Hg) in predatory species from the Rio Grande at Elephant Butte Reservoir, NM, a condition documented in previous studies. Arsenic (As) and selenium (Se) concentrations were greatest in fish from sites in the central RGB; Se concentrations in fish from the Pecos River at Red Bluff Lake, TX and from the Rio Grande at Langtry, TX and Amistad International Reservoir, TX exceeded published fish and wildlife toxicity thresholds. In the lower RGB, residues of p,p'-DDT metabolites (相似文献   

Age and trophic position dominate bioaccumulation of mercury and organochlorines in the food web of Lake Washington

Understanding the mechanisms of bioaccumulation in food webs is critical to predicting which food webs are at risk for higher rates of bioaccumulation that endanger the health of upper-trophic predators, including humans. Mercury and organochlorines were measured concurrently with stable isotopes of nitrogen and carbon in key fishes and invertebrates of Lake Washington to explore important pathways of bioaccumulation in this food web. Across the food web, age and trophic position together were highly significant predictors of bioaccumulation. Trophic position was more important than age for predicting accumulation of mercury, sigmaDDT, and sigma-chlordane, whereas age was more important than trophic position for predicting sigmaPCB. Excluding age from the analysis inflated the apparent importance of trophic position to bioaccumulation for all contaminants. Benthic and pelagic habitats had similar potential to bioaccumulate contaminants, although higher sigma-chlordane concentrations in organisms were weakly associated with more benthic carbon signals. In individual fish species, contaminant concentrations increased with age, size, and trophic position (delta15N), whereas relationships with carbon source (delta13C) were not consistent. Lipid concentrations were correlated with contaminant concentrations in some but not all fishes, suggesting that lipids were not involved mechanistically in bioaccumulation. Contaminant concentrations in biota did not vary among littoral sites. Collectively, these results suggest that age may be an important determinant of bioaccumulation in many food webs and could help explain a significant amount of the variability in apparent biomagnification rates among food webs. As such, effort should be made when possible to collect information on organism age in addition to stable isotopes when assessing food webs for rates of biomagnification.     

Price variation in spatial markets: the case of perfectly inelastic demand

This paper analyzes short-run price variation in one-dimensional (i.e., circular, linear) spatial markets where both producers and consumers are numerous. Price reaction functions are established for firms under symmetrical price conjectures. For perfectly inelastic consumer demand each firm's equilibrium price is shown to depend upon distance-decay effects in both firms' locations and marginal costs. The rate of distance decay in these effects is inversely related to the degree of price conjectural variation in the market. Boundary effects in spatial markets are also shown to influence these distance-decay rates and, thus, patterns of firms' equilibrium prices.An earlier version of this paper was presented at the IGU Mathematical Models Working Group in Canberra, Australia during August 1988. The authors gratefully acknowledge the comments of two referees