Much of the contamination in the polar region originates from human activities in southern latitudes. A broad range of organic and metal pollutants, acidifying compounds, and radioactive contaminants is carried north by winds, rivers and ocean currents. A second major source of contaminants is from localized areas that are severely contaminated as a direct result of activities within the Arctic. The first comprehensive program to examine levels of anthropogenic pollutants and assess their effects in all the polar countries was undertaken by the Arctic Monitoring and Assessment Program (AMAP) established in 1991.
As described in the entry on Local and Transboundary Pollution, major atmospheric, oceanic, and river pathways converge in the Arctic, delivering contaminants from remote sources and circulating them within the Arctic. These processes are referred to variously as the grasshopper effect, the global distillation hypothesis, and long-range transport. The atmosphere contains relatively few contaminants compared with the total burden in Arctic soil, sediments, and water. It is nonetheless an important pathway to the Arctic and is the fastest route from the source of pollution, delivering contaminants from locations around the world in days or weeks. Ocean currents move more slowly, taking months or years to carry compounds to the Arctic. Industrial impact on the large Russian rivers that originate to the south and discharge into the Arctic (specifically the Ob' and Yenisey) is considerable. Suspended solids carrying contaminants are deposited in sediment in estuaries, deltas, and on coastal shelves, leading to local and regional dispersal of radionuclides, some heavy metals, polychlorinated biphenyls (PCBs), dichlorodiphenyltrichloroethane (DDT), and oil. There is little industrial impact on Canadian river systems flowing north. Sea ice may be important in transporting contaminants from coastal sediments and from atmospheric deposition.
In heavily industrialized parts of the Russian Arctic and in eastern Finnmark (Norway), metal and organic contamination from air emissions and effluent is intense and has had catastrophic ecological impacts in some locations. Former military sites in Canada and the United States provide chronic, low-level inputs of some metals and PCBs. Contamination from these local point sources are the second major pollution concern in the Arctic.
The following groups of contaminants exist in the Arctic under conditions that are potentially damaging or threatening to certain ecosystems or human health: persistent organic pollutants (POPs), heavy metals, acidifying sulfates and nitrates, petroleum hydrocarbons, and radioactive contaminants.
Among the POPs found in the Arctic, the most prevalent in air and snow are pesticides such as DDT, hexachlorocyclohexanes (HCH), and chlordane, and technical products such as PCB mixtures and chlorobenzenes. These are most likely to have traveled from the midlatitudes of the Northern Hemisphere via air currents. The Canada Basin and Canadian Arctic Archipelago have the highest HCH concentrations among the world's oceans. These are attributed mainly to remote sources. The highest PCB and DDT concentrations in Arctic biota and sea water occur near Svalbard, the southern Barents Sea, and eastern Greenland. A significant contribution to these comes from Russian rivers carrying compounds into Arctic waters from sources further south. PCBs from decommissioned military sites in Canada and dioxins/furans from smelters in Norway are examples of sources within the Arctic.
Heavy metal contamination is associated primarily with the combustion of fossil fuels, mining and smelting, and manufacturing industries. Volcanic activity, forest fires, rock weathering, and other natural processes contribute to contaminant levels in the Arctic, but are less significant than anthropogenic releases. Heavy metals emissions in the Urals, Kola Peninsula, Noril'sk, industrial Central and Eastern Europe contribute more than half of the air pollution in the Arctic. Industrial sources in Europe and North America account for up to one-third. The most severe effects from heavy metals result from local pollution. The nickel-copper smelters on the Kola Peninsula and at Noril'sk have severely polluted nearby terrestrial and freshwater environments. Although most of the smelter emissions are deposited close by, they still represent a major source of circumpolar contamination. Emissions from Kola Peninsula are the major source of metals in northern Fennoscandian air, and emissions from the Urals and Noril'sk increase air concentrations over Alaska and northern Canada. Mercury found in lake and ocean sediments comes in part from remote sources, and increasing concentrations may
Red hot slag from a nickel foundry in Noril'sk is poured onto a heap, Western Siberia, Russia.
Copyright Bryan and Cherry Alexander Photography
Red hot slag from a nickel foundry in Noril'sk is poured onto a heap, Western Siberia, Russia.
Copyright Bryan and Cherry Alexander Photography reflect global increases. Anthropogenic sources of mercury within the Arctic are minor on the global scale but may cause local pollution, especially in lakes and rivers. The amount of anthropogenic cadmium that enters the Arctic Ocean from the atmosphere is less than 1% of the cadmium that enters from natural sources, and is mostly from mining in the Kola Peninsula.
Petroleum hydrocarbon contamination associated with exploration, development, and the transportation of oil and gas has caused localized contamination. Contributions come from sources within and outside the Arctic, with the highest concentrations occurring at the mouths of the large Russian rivers. Except in a few areas affected by spills, however, the Arctic is relatively free of hydrocarbon contamination. Where spills do occur, effects tend to be more severe and persistent in the Arctic than elsewhere. Outside the Arctic, large releases of petroleum hydrocarbons associated with oil and gas operations have had devastating impacts on local marine ecosystems and bird species. Growth in Arctic oil and gas operations is increasing the risk of similar releases in the Arctic.
Acidifying sulfur dioxide and nitrogen oxides from global sources associated with industry, energy production, and transport results in low-level but widespread contamination throughout the Arctic. Within the Arctic these contaminants are produced by nonferrous smelters on the Kola Peninsula and at Noril'sk. The impacts of acidification are apparent in the Kola Peninsula and in a limited area in Norwegian eastern Finnmark. Damage to forests, fish and invertebrates has occurred near the Kola smelters. Extensive vegetation damage is evident in a region surrounding the smelter of Noril'sk. In specific areas that are particularly sensitive, the effects of acidification from longrange transported pollutants can also be found. In Svalbard, a decreasing trend in air concentrations of sulfates and nitrates is attributed to reductions in European sulfur emissions. Concentrations in the Canadian Arctic and Alaska have not decreased. Soil and freshwater are particularly sensitive to acidification where the soil is acid and shallow. Most of northern Fennoscandia, the northern part of the Kola Peninsula, and parts of the Canadian Shield are vulnerable.
Radioactive contamination comes from three primary sources: past atmospheric nuclear weapons testing, releases from European nuclear reprocessing plants (e.g., Sellafield in the UK), and fallout from the Chernobyl accident. Long-range marine transport has resulted in some radioactive accumulations in Arctic sediments. Arctic sources such as dumped nuclear waste, nuclear storage sites, accidents, and underground explosions have led to localized contamination. The greatest concerns about radioactive contamination in the Arctic arise from the consequences in the event of an accident. Radioactive sources, including numerous operating and decommissioned nuclear reactors, are highly concentrated in northwestern Russia, and represent a potential for the release of considerable quantities of radioactive contamination.
For various reasons, relatively low levels of contamination may have a greater impact on the Arctic environment than the same levels would have on other environments. Arctic ecosystems have adapted to the harsh conditions of the Arctic in ways that make them unique and more sensitive. Adaptation to cold, for example, gives fat a more dominant role in the metabolism of Arctic animals, resulting in the transfer of larger quantities of lipids and fat-soluble compounds up the food chain. Thus, the potential for low concentrations of fat-soluble environmental contaminants to accumulate and have effects at the top of the food chain increases. Some indigenous peoples who rely on a traditional diet are consequently among the most exposed in the world to certain contaminants. The rate of biological productivity is limited under Arctic conditions, affecting attenuation processes such as micro-bial degradation. This is important, for example, in evaluating the significance of metal and petroleum hydrocarbon contaminants, which are detoxified or degraded by natural processes in more temperate environments.
POPs are similar in that they are unusually resistant to degradation and are fat-soluble. Among the most persistent of these are the organochlorines, which resist degradation in virtually any environment. Although the concentrations of POPs are generally lower in the Arctic than anywhere else, the distribution varies and high levels accumulate in some biological species. Food chains provide the biological links for uptake, transfer, and sometimes magnification of contaminants by plants and animals. The more hydropho-bic organochlorines partition quickly onto soil and plant surfaces, from which they are assimilated in the food chain through diet. The most persistent are found in predatory birds and mammals high up in the food chain, with various compounds dominating in different species, depending on metabolism capabilities. For example, PCBs, chlordane, and DDT reach high concentrations in seals. In polar bears, PCBs and chlordane continue to accumulate but DDT is metabolized, leaving only traces. In some Arctic species, DDT and dioxin-like compounds are present in concentrations that are likely to produce effects.
For humans, food is the major exposure route to contaminants in the Arctic. While reductions in production have caused a decline in the environmental levels of some Arctic contaminants, lower human exposure is not yet evident for many contaminants. Since the ban on above-ground nuclear weapons testing in the 1960s, human exposure to radionuclides has generally declined. Populations that rely on country food from cadmium-rich areas may have very high cadmium intakes. The degree of mercury and cadmium uptake in mammals varies geographically, possibly due to differences in diet or processes related to temperature, or the contamination may be introduced to the food chain through returning migratory species that acquire high contaminant burdens in the South.
The first controls on POPs began 25 years ago. Since then, Arctic levels have declined in the environment but have not decreased in people with traditional diets. In certain geographic areas, human exposure to mercury, cadmium, and organic contaminants including toxaphene, PCBs, and chlordane is high enough to indicate a need for public health measures. It is not obvious what approach should be taken to reduce exposure. Changes to current patterns of traditional food consumption have not been recommended because, while the health-promoting effects of this diet are well documented, the associated risks are not, and there is no convincing evidence of adverse health effects. Evaluation of the risks is complicated because there are both scientific and social issues that must be taken into account.
The levels of many contaminants in the Arctic are likely to remain at or close to existing levels for decades. For the most part, local and regional contamination can be reduced through legislation and with adequate financial and technological resources. Where contamination is part of a global process, long-term reductions can only be achieved through continuing global reforms.
Environmental Sciences Group, Royal Military
College of Canada
See also Heavy Metals; Hydrocarbon Contamination; Local and Transboundary Pollution; Persistent Organic Pollutants (POPs); Radioactivity
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