One of the main values of Antarctica for science is the near-pristine environment, with snow, ice, soil, sediments, terrestrial and marine organisms providing an ideal archive of data on past and current trends in global atmospheric and marine contamination. However, tourism, scientific research and supporting logistic activities inevitably affect the Antarctic environment. Over the first half of the 20th century, the impact was limited because most expeditions had few participants and technological devices. However, beginning with the International Geophysical Year in 1958-1959 (with the involvement of 12 countries and over 5,000 persons occupying 55 stations on the continent and in the Southern Ocean), there was a significant increase in the geographical extent of research activities, and in the number of wintering stations, personnel and supporting infrastructures (Beltramino 1993). Concern about the localised detrimental impact of human activity in Antarctica began to be expressed in the 1970s (e.g. Parker 1978). At several stations, refuse was left to accumulate or dumped into the sea, and disused vehicles and bases were abandoned and left to deteriorate. Cameron (1972), for example, described many instances of poor waste management in the past at McMurdo Station (the largest in Antarctica, with about 1,200 persons in summer) and at remote field camps in the Dry Valleys (southern Victoria Land). The open burning of wastes contaminated the environment near scientific stations with soot containing PCBs (Risebrough et al. 1976).
Environmental awareness among the Antarctic Treaty states has greatly increased during the last decades, and significant improvements in pollution control and prevention have been made (or planned) under the requirements of the Protocol on Environmental Protection, which came into force in January 1998. With the exception of ship, aircraft and vehicle transport (to, from or within Antarctica), the release of persistent atmospheric contaminants is localised in scientific stations and is mainly due to the use of fuel (for the production of electricity, heating, water production, and equipment operation), waste disposal (including incineration), the use of chemical products in machinery, small engineering processes and scientific research. The risk of environmental impact is especially high in regions such as the Fildes Peninsula (King George Island), with a great concentration of multinational activities (10 scientific stations, various field huts and refuges, and some decades of overwintering persons; Harris 1991). In general, the most common persistent contaminants around stations are trace metals and POPs, which can be typically detected within a few hundred metres. Even at stations which have been occupied for long periods and were established when little attention was paid to environmental protection, no effects can be detected at distances greater than a kilometre (UNEP 2002a). Mazzera et al. (2001a) measured concentrations of PM10 (aerosol particles with aerodynamic diameter<10 |m) during the 1995-1996 and 1996-1997 austral summers at Hut Point (less than 1 km from the centre of McMurdo Station), and found that major contributors were soil (57 %), sea salt (15 %), fossil fuel combustion (14 %), and sources of secondary sulphate (10 %). Human activity at McMurdo Station consumes about 2x106 gallons of diesel fuel during summer, and it was estimated that the power-generating station for electricity and water production contributed to 69 % of combustion sources, while the remaining amount was due to heating. Ambient elemental carbon concentrations (129 ng m-3; Mazzera et al. 2001b) were two orders of magnitude higher than background concentrations measured in Antarctica during austral summer (Bodhaine 1996; Wolff and Cachier 1998). The pollution plume at McMurdo contained concentrations of Pb (0.85 ng m-3) and Zn (1.52 ng m-3; Mazzera et al. 2001b) which were 17 and 46 times higher respectively than values measured during summer at the South Pole (0.051 and 0.033 ng m-3 respectively; Maenhaut et al. 1979). It seems likely that the deposition of atmospheric pollutants in McMurdo Sound can affect ecosystems at distances greater than that (1 km) indicated in the UNEP Report. Furthermore, metals and other atmospheric contaminants are released and widely dispersed from aircraft. Boutron and Wolff (1989), for instance, estimated that about 20 % (1,800 kg year-1) of the total deposition of
Pb over continental snow was due to emissions from within Antarctica, and that a large proportion of the metal was from aviation gasoline.
The Environmental Protocol obliges signatories to the Antarctic Treaty to monitor the existing environmental impact, and the Antarctic Environment Officers Network (AEON) of COMNAP (Council of Managers of National Antarctic Programs) in July 2001 gave an account of environmental monitoring activities around Antarctic scientific stations. The release of atmospheric contaminants from Antarctic stations is trivial in a global context. However, monitoring is necessary to improve environmental management, to meet the legal requirements of the Protocol and to protect the scientific value of Antarctica. Monitoring data provide a means of defining the "fingerprint" of local releases, and to adopt suitable sampling strategies for studies concerning the assessment of global transport and deposition of persistent contaminants. Moreover, available data show that at present local inputs are the only ones with the potential to accumulate in organisms to levels which might induce biological responses (Venkatesan and Kennicutt 1996).
At McMurdo Station, besides soot, PCBs and trace metals, there is also evidence of local emission of PCDDs and PCDFs (Lugar et al. 1996). Trace levels of only a few PCDD/PCDF congeners were detected sporadically in air samples collected in 1992-1994 at a site about 500 m downwind of the station. The highest and most varied values were measured at a "downtown" location (total PCDDs varied in the range 0.12-1.8 pg m-3 and PCDFs in the range <0.02-2.77 pg m-3), indicating that, in addition to the main solid-waste incinerator, there are various combustion sources which release dibenzo-p-dioxins and dibenzofurans at McMurdo. However,Antarctic air at remote site resulted free of PCDD/PCDF compounds, considering the detection limit in the sub-pg m-3 range (Lugar et al. 1996). Other atmospheric byproducts of combustion (also evaporating from hydrocarbon fuel spillages) are Polycyclic Aromatic Hydrocarbons (PAHs). For three summer seasons (1993-1995), Caricchia et al. (1995) measured particulate PAHs at a series of sampling stations set up within 200 m of the Italian "Baia Terra Nova" research station. Overall PAH concentrations ranged from 15-700 pg m-3 and the 11 analysed compounds showed very low concentrations (hundreds to thousands of times lower than particulate PAHs in urban areas). The plant for generating electricity was considered the most important source of PAHs at Baia Terra Nova Station.
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