Historical reconstruction of Plutonium contamination in the Swiss-Italian Alps
1 Institute for the Dynamics of Environmental Processes IDPA-CNR, 30123 Venice, Italy
2 Department of Environmental Sciences, Informatics and Statistics, University Ca’ Foscari of Venice, 30123 Venice, Italy
3 Paul Scherrer Institut, 5232 Villigen (PSI), Switzerland
4 Laboratoire de Glaciologie et Géophysique de I’Environnement (LGGE), University Joseph Fourier of Grenoble, 38402 St Martin d’Hères Cedex, France
5 Centre for Ice and Climate - Niels Bohr Institute, University of Copenhagen, DK-2100 Copenhagen, Denmark
Plutonium is present in the environment as a consequence of atmospheric nuclear tests carried out in the 1960s, nuclear weapons production and releases by the nuclear industry over the past 50 years. Approximately 6 tons of 239Pu have been released into the environment as a result of 541 atmospheric weapon tests Nuclear Pu fallout has been studied in various environmental archives, such as sediments, soil and herbarium grass. Mid-latitude ice cores have been studied as well, on Mont Blanc, the Western Alps and on Belukha Glacier, Siberian Altai. We present a Pu record obtained by analyzing 52 discrete samples of an alpine firn/ice core from Colle Gnifetti (M. Rosa, 4450 m a.s.l.), dating from 1945 to 1991. The 239Pu signal was recorded directly, without preliminary cleaning or preconcentration steps, using an high resolution inductively plasma mass spectrometer equipped with a desolvation system. The 239Pu profile reflects the three main periods of atmospheric nuclear weapons testing: the earliest peak lasted from 1954/55 to 1958 and was caused by the first testing period reaching a maximum in 1958. Despite a temporary halt of testing in 1959/60, the Pu concentration decreased only by half with respect to the 1958 peak due to long atmospheric residence times. In 1961/62 Pu concentrations rapidly increased reaching a maximum in 1963. After the signing of the “Limited Test Ban Treaty” between USA and USSR in 1964, Pu deposition decreased very sharply reaching a minimum in 1967. The third period (1967-1975) is characterized by irregular Pu concentrations with smaller peaks which might be related to the deposition of Saharan dust contaminated by the French nuclear tests of the 1960s.
Key words: Plutonium / Alps / ice / snow / ICP-SFMS / nuclear tests
© Owned by the authors, published by EDP Sciences, 2013
This is an Open Access article distributed under the terms of the Creative Commons Attribution License 2.0, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.