{240}$Pu/$^{239}$Pu signatures allow refining the chronology of radionuclide fallout in South America

• Published in: The Science of the total environment Vol. 843
• Main Authors: Chaboche, Pierre-Alexis, Pointurier, Fabien, Sabatier, Pierre, Foucher, Anthony, Tiecher, Tales, Minella, Jean P. G., Tassano, Marcos, Hubert, Amélie, Morera, Sergio, Guédron, Stéphane, Ardois, Christophe, Boulet, Béatrice, Cossonnet, Catherine, Cabral, Pablo, Cabrera, Mirel, Chalar, Guillermo, Evrard, O.
• Format: Journal Article
• Language: English
• Published: Elsevier 15-10-2022
• Subjects: Agricultural sciences; Continental interfaces, environment; Earth Sciences; Environmental Sciences; Geochemistry; Geomorphology; Life Sciences; Sciences of the Universe; Soil study; Nuclear weapon tests; Geochronology; Panoply; Soil erosion; Plutonium isotopes
• ISSN: 0048-9697; 1879-1026
• DOI: 10.1016/j.scitotenv.2022.156943

Atmospheric nuclear tests (1945-1980) have led to radioactive fallout across the globe. French tests in Polynesia (1966-1974) may influence the signature of fallout in South America in addition to those conducted by USA and former USSR until 1963 in the Northern hemisphere. Here, we compiled the $^{240}$Pu/$^{239}$Pu atom ratios reported for soils of South America and conducted additional measurements to examine their latitudinal distributions across this continent. Significantly lower ratio values were found in the 20-45° latitudinal band (0.04 to 0.13) compared to the rest of the continent (up to 0.20) and attributed to the contribution of the French atmospheric tests to the ultra-trace plutonium levels found in these soils. Based on sediment cores collected in lakes of Chile and Uruguay, we show the added value of measuring $^{240}$Pu/$^{239}$Pu atom ratios to refine the age models of environmental archives in this region of the world.