Historical reconstruction of Plutonium contamination in the Swiss-Italian Alps

• Published in: E3S Web of Conferences
• Main Authors: Gabrieli J., Cozzi G., Vallelonga P., Schwikowski M., Sigl M., Boutron C., Barbante C.
• Format: Article in Journal/Newspaper
• Language: English; French
• Published: EDP Sciences 2013
• Subjects: Plutonium; Alps; ice; snow; ICP-SFMS; nuclear tests; Environmental sciences; GE1-350; Mont Blanc; ice core
• Online Access: https://doi.org/10.1051/e3sconf/20130114001; https://doaj.org/article/223d2bd7036f47e59bfe4f19717147b2

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.