Summary

Compared to the rest of the world, the Antarctic environment is less affected by anthropogenic contaminants, but it is not pristine. The deposition of artificial radionuclides on the continent was first detected in the 1950s, and that of pesticides a few years later. Although the first reports of DDT contamination in Antarctica were questioned in the belief that the residues reached the continent on ships and planes serving research stations, in the early 1970s it became clear that other continents of the Southern Hemisphere were the source of pesticides and other persistent POPs. Antarctic snow constitutes an immense, natural receptacle for atmospheric contaminants and, with respect to other depositional environments such as peat bogs or lake sediments, permanently frozen snow and ice have a chemical composition more directly related to that of the overlying atmosphere and also contain more detailed records, including individual precipitation events. However, the atmosphere/snow transfer of contaminants and post-depositional processes affecting their incorporation into snow are complex and still largely unknown. There is evidence that snow is chemically active and produces a number of chemical compounds which affect local atmospheric photochemistry. A better knowledge of these processes and the post-depositional fate of contaminants are a prerequisite for reliable quantitative estimates of chemical concentrations in recent and past atmospheres based on contaminant concentrations measured in snow and ice. Despite these limitations, the recent introduction of suitable procedures to prevent contamination of samples, and of analytical techniques for the direct determination of chemicals in snow at the sub-picogram per gram level has promoted a number of studies in Antarctica and the Arctic, Alps and Andes. These studies aim to reconstruct pathways of airborne contaminants and temporal changes in their deposition pat tern. Research performed in Antarctic snow and firn during the last decade shows that, especially in the period between the 1950s and 1980s, the continent received 137Cs and other artificial radionuclides, DDTs, PCBs, HCHs, and some metals such as Pb, Cu and, probably, Ag, Cd, U, Cr, Bi and Zn, derived from human activities in the Southern Hemisphere. A large amount of airborne metals was probably released in South America, even if the relative metal contribution from natural sources such as volcanoes, rock and soil particles, and the marine environment is still uncertain, and for some metals it may be greater than previously supposed.

Environmental contamination from local human activities in Antarctica may compromise studies which aim to assess biogeochemical cycles of elements or large-scale processes in the transport and deposition of persistent atmospheric contaminants. In general, snow data show that the impact of human activities is relatively small and highly localised, usually confined to within a few kilometres or few hundred metres of human settlements. The main exception was probably the release of Pb by aircraft, and other man-made emissions from the 1960s to the 1980s; this impact has been significantly reduced in recent years through the progressive phasing-out of leaded gasoline.

Many Antarctic scientific stations are located in coastal ice-free areas where soils, lichens and mosses are among the most suitable environmental matrices to assess the impact of human activities. Environmental impact assessment is among the actions required under the Protocol on Environmental Protection to the Antarctic Treaty. In the past, wastes were often dumped or open-burned close to stations; through the analysis of soils, the nature and extent of pollution in some degraded Antarctic sites was detected and measures to remediate local environmental pollution were undertaken.

At present, trace metals and PAHs from combustion processes and fuel and oil spill are among the most widespread contaminants around scientific stations. In general, most contaminants have a low mobility in dry Antarctic soils; however, climate change may affect soil leaching and drainage processes. Antarctic organisms can play an important role in the assessment of anthropogenic impacts. Changes in the biodiversity of indigenous flora and fauna, for instance, can be valuable indicators in Antarctic ice-free areas, and some species of Antarctic macrolichens and mosses, which are long-term integrators of persistent atmospheric pollutants, can be used as reliable biomonitors of atmospheric deposition of trace metals, PCBs and other chemicals. These organisms could be used to establish long-term biomonitoring networks based on the analysis of indigenous cryptogams or of mosses and lichens exposed near stations in small nylon bags.

Although this chapter has discussed environmental monitoring assessment and recovery around several scientific stations, many other abandoned stations and dumping sites exist throughout Antarctica, not only in coastal ice-free areas but also on ice.As for the latter sites, concern arises from the fact that small spills of drilling fluids and all forms of waste, debris and contaminants from human activities on the Antarctic plateau will remain in the ice for thousands of years and will be gradually transported towards the coast within the ice sheet.

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