Dennis Gregor

Arctic contaminants: sources, occurrence and pathways

Potentially toxic organic compounds, acids, metals and radionuclides in the northern polar region are a matter of concern as it becomes evident that long-range transport of pollution on hemispheric to global scales is damaging this part of the world. In this review and assessment of sources, occurrence, history and pathways of these substances in the north, the state of knowledge of the transport media--the ocean and atmospheric circulation--is also examined. A five-compartment model of the northern region is developed with the intent of assessing the pathways of northern contaminants. It shows that we know most about pathways of acids, metals and radionuclides and least about those of complex synthetic organic compounds. Of the total annual inputs of anthropogenic acidic sulphur and the metals lead and cadmium to the Arctic via the atmosphere, an estimated 10-14% are deposited. A water mass budget for the surface layer of the Arctic Ocean, the most biologically active part of that sea, is constructed to examine the mass budget for one of the major persistent organochlorine compound groups found in remote regions, hexachlorocyclohexanes (HCH), one isomer of which is lindane. It is concluded that both the atmosphere and the ocean are important transport media. Even for the HCH substances which are relatively easily measured and simple in composition compared to other synthetic organics, we know little about the occurrence and environmental physical/chemical characteristics that determine pathways into the food chain. More environmental measurements, chemical characterization studies and environmental chemical transport modelling are needed, as is better knowledge of the circulation of the Arctic Ocean and the marine food web.

Enantioselective Breakdown of .alpha.-Hexachlorocyclohexane in a Small Arctic Lake and its Watershed.

Water and snow samples were collected at Amituk Lake on Cornwallis Island to investigate the enantioselective degradation of α-hexachlorocyclohexane (α-HCH)in the Arctic. The two enantiomers were separated by gas chromatography on permethylated cyclodextrin capillary columns. The enantiomeric ratio (ER=(+)α-HCH)(-)α-HCH) for an α-HCH standard was 1.00±0.005, which is in excellent agreement with a theoretical ER of 1.00 for unmetabolized α-HCH. ERs of snow samples were racemic (0.9810.03). Degradation was found in Amituk Lake at 15-21 m where ERs were 0.7710.004; however, stream runoff and lake outflow ERs varied considerably during the study. ERs of the outflow traced the meltwater running over the surface of the lake, being close to streamwater values during peak runoff and returning to deep lake water values during low flow. Streamwater ERs decreased within a few weeks of snowmelt and showed a large variability (0.970.62), which may be due to the differences in temperature and amount of suspended sediments. The rapid enantioselective breakdown of a-HCH suggests that the ability of arctic microbial systems to degrade organic contaminants is greater than commonly thought

The historical residue trend of PCBs in the Agassiz Ice Cap, Ellesmere Island, Canada

Current detailed measurements of contaminant deposition cannot provide a historical perspective except through long-term monitoring programs. In the Aretic, ice caps provide an alternative to lake sediments, in that the annual snow layers reflect atmospheric deposition. As a result of the remoteness of the ice cap and the limited summer melt, annual layers undergo little chemical change, especially after the first summer season, and therefore provide a well-defined historical record. Initial work was undertaken at the Agassiz Ice Cap (80°49′50″ N, 72°56′30″ W) beginning in 1986, but a major effort was undertaken in 1993, during which snow samples covering 30 years were taken from a snow pit. Large volume snow samples were obtained for the determination of PCB congeners. Mean ΣPCB deposition to the ice cap ranged from 930 ng/m2/year in the winter of 1967–1968 to a minimum of 91 ng/m2/year in 1980–1981. Since 1980–1981, deposition has again increased to a local maximum of 848 ng/m2/year (in 1989–1990). The mean deposition for the 30 years of record was 406 ng/m2/year, with no evidence of a consistent long-term trend.

The recent depositional trend of polycyclic aromatic hydrocarbons and elemental carbon to the Agassiz Ice Cap, Ellesmere Island, Canada

Polar ice caps can provide long-term records of atmospheric deposition. Owing to the prevalent conditions, the layers of accumulated snow are subject to little chemical or physical change and are temporally well defined. Sampling of the Agassiz Ice Cap on Ellesmere Island was undertaken in early 1993 to investigate the potential of polar ice caps for use in determining recent historical trends in the deposition of anthropogenic contaminants to the Arctic. Discrete annual snow and ice layers representing the last 30 years of accumulation were sampled from a deep pit to obtain large volume samples for the determination of polycyclic aromatic hydrocarbons (PAHs) and elemental carbon (EC). The flux of PAHs to the ice cap has remained relatively constant for the past 20 years, with a mean value of 11 (± 6) μg/m2/year. This equates to a total annual loading of PAH to the Arctic of 37 t/year for the same period. Prior to this period, a greater flux of 74 (± 20) μg/m2/year is observed. Mean values for EC concentration and flux were found to be 2.6 (± 2.8) μg/l and 310 (± 370) μg/m2/year, respectively. However, analytical complications were encountered with the analysis of EC, and these data should be considered as preliminary baseline values only.

Deposition of atmospherically transported polychlorinated biphenyls in the Canadian arctic

Abstract Snow collectors were installed in 1990 at two Canadian high arctic weather stations (Mould Bay {MB} and Eureka {EU}) in an effort to estimate annual deposition of PCBs, compare these estimates to annual snowpack measurements and to investigate the timing of the deposition. The collectors operated successfully but tended to over collect when two snow fences were used. The daily flux of ΣEPCBs in the snowpack for 1990/91 generally compared well to that of the snow collector at MB. The snowpack sample at EU for the same period was considered to be unrepresentative, due to low snow accumulation on the ground and high winds, with resulting low concentrations and fluxes. The congener makeup of snowpack and snow collector samples was similar for both sites. Mean ΣEPCB fluxes for the collectors for the winter season were 2.0 and 3.8 ng· m −2 · day −1 for MB and EU respectively. Due to the tendency of the collectors to overcatch, especially late in the season, the fluxes were corrected relative to the shielded Nipher Gauge used to measure snowfall at the weather stations. The corrected ΣEPCB fluxes for MB reduced the overall contribution of a high concentration event in the winter, in favour of the fall season, the time of greatest snow accumulation. Initial assessment of the collectors for measuring the timing of and composition of PCB deposition to the arctic is very encouraging. Work is continuing to improve the collectors and to provide a better estimate of deposition of organic contaminants to the arctic environment.

Contaminant fate in high arctic lakes: development and application of a mass balance model

Abstract Steady- and unsteady-state models based on the QWASI fugacity/aquivalence approach and describing chemical fate in high Arctic lakes were developed and applied to Amituk and Char Lakes on Cornwallis Island, NWT, Canada. The model considered characteristics of Arctic lakes, such as water and chemical throughflow, development and depletion of ice cover, and temperature dependence of physical-chemical properties. The model of Char Lake was parameterized and calibrated with literature data for phosphorus, and for Amituk Lake, data were obtained from the Amituk Lake project, focusing on ΣDDT. Model results indicate that Arctic lakes act as conduits, not sinks for chemicals. Most loadings are from snowmelt that enter via stream inflow and most is exported from the lake; minimal amounts of chemicals volatilize or are retained in sediments. Burial is restricted by low-suspended particle concentrations that convey chemicals to the sediment. An attendant implication of the low-suspended particle concentrations is that nearly all chemicals remain in the dissolved phase in the water column. Consequently, chemical persistence is mainly controlled by water retention time which, for these small lakes, is several years. The illustrative unsteady-state model shows seasonal effects on chemical processes such as cryoconcentration that may increase water column concentrations by up to 15% in early May.

Use of a food web model to evaluate the factors responsible for high PCB fish concentrations in Lake Ellasjøen, a high Arctic Lake

Background, aim, and scopeLake Ellasjøen, located in the Norwegian high arctic, contains the highest concentrations of polychlorinated biphenyls (PCBs) ever recorded in fish and sediment from high arctic lakes, and concentrations are more than 10 times greater than in nearby Lake Øyangen. These elevated concentrations in Ellasjøen have been previously attributed, in part, to contaminant loadings from seabirds that use Ellasjøen, but not Øyangen, as a resting area. However, other factors, such as food web structure, organism growth rate, weight, lipid content, lake morphology, and nutrient inputs from the seabird guano, also differ between the two systems. The aim of this study is to evaluate the relative influence of these factors as explanatory variables for the higher PCB fish concentrations in Ellasjøen compared with Øyangen, using both a food web model and empirical data.MethodsThe model is based on previously developed models but parameterized for Lakes Ellasjøen and Øyangen using measured data wherever possible. The model was applied to five representative PCB congeners (PCB 105, 118, 138, 153, and 180) using measured sediment and water concentrations as input data and evaluated with previously collected food web data.ResultsModeled concentrations are within a factor of two of measured concentrations in 60% and 40% of the cases in Lakes Ellasjøen and Øyangen, respectively, and within a factor of 10 in 100% of the cases in both lakes. In many cases, this is comparable to the variability associated with the data as well as the efficacy of the predictions of other food web model applications.DiscussionWe next used the model to quantify the relative importance of five major differences between Ellasjøen and Øyangen by replacing variables representing each of these factors in the Ellasjøen model with those from Øyangen, in separate simulations. The model predicts that the elevated PCB concentrations in Ellasjøen water and sediment account for 49%–58% of differences in modeled fish PCB concentrations between lakes. These elevated sediment and, to a lesser extent, water concentrations in Ellasjøen are due to PCB loadings from seabird guano. However, sediment–water fugacity ratios of PCBs are consistently greater in Ellasjøen compared with Øyangen, which suggests that internal lake processes also contribute to differences in sediment and water concentrations. We hypothesize that the nutrients associated with guano influence sediment–water fugacity ratios of PCBs by increasing the stock of pelagic algae. As both these algae and the guano settle, their organic carbon content is degraded faster than PCBs, which causes an extra magnification step in Ellasjøen before these detrital particles are consumed by benthic organisms, which are in turn consumed by fish. The model predicts that the remaining ∼50% of the differences in PCB concentrations observed between the fish of these lakes are due to other subtle differences in their food web structures.ConclusionsIn conclusion, based on the results of a food web model, we found that the most dominant factors influencing the higher PCB fish concentrations in Lake Ellasjøen compared with Øyangen are the higher sediment and water concentrations in Ellasjøen, caused by seabird guano. Together, sediment and water are predicted to account for 49%–58% of differences in fish concentrations between lakes. Although seabird guano provides a source of nutrients to the lake, in addition to contaminants, empirical data and indirect model results suggest that nutrients are not leading to decreased bioaccumulation, in contrast to what has been observed in temperate, pelagic food webs.Recommendations and perspectivesThe results of this study emphasize the importance of considering even small differences in food web structure when comparing bioaccumulation in two lakes; although the food web structures of Ellasjøen and Øyangen differ only slightly, the model predicts that these differences account for most of the remaining ∼50% of the differences in PCB fish concentrations between the two lakes. This study further demonstrates the utility of food web models as we were able to predict and tease apart the influence of various factors responsible for the elevated concentrations in the fish from Lake Ellasjøen, which would have been difficult using the field data alone.