Radioactive fallout legacy of nuclear tests in soils of the Southern Hemisphere
Abstract Fallout radionuclide (FRN) archived in soils are key tracers of soil redistribution, sediment dynamics, and associated carbon fluxes, yet their global application is limited by poorly constrained baselines in the Southern Hemisphere. Here, we present the first hemisphere-scale baseline and uncertainty maps of 137 Cs and 239+240 Pu soil inventories. Predictions exhibited lower spatial variability and relative uncertaintyfor 137 Cs across most landscapes, whereas 239+240 Pu showed greater spatial variability and larger relative uncertainty. The reconstructed inventories revealed strong latitudinal and topographic gradients, with the highest predicted fallout occurring in tropical and mountainous regions. We further show, under a standardized hypothetical 50% inventory-loss scenario, that uncertainty in low-inventory regions can propagate nonlinearly into soil erosion and carbon-budget estimates, producing carbon budget biases of up to 19.8 t C ha −1 . These findings provide a new benchmark for Southern Hemisphere fallout radionuclide applications and a scalable framework for integrating spatial uncertainty into sediment tracing, soil degradation assessment, and carbon cycle studies.
Authors
- Hélène Angot (ORCID: https://orcid.org/0000-0003-4673-8249)
- Olivier Cerdan (ORCID: https://orcid.org/0000-0003-1395-3102)
- Katrin Di Bella Meusburger (ORCID: https://orcid.org/0000-0003-4623-6249)
- Christine Alewell (ORCID: https://orcid.org/0000-0001-9295-9806)
- Aydoğan Avcıoğlu (ORCID: https://orcid.org/0000-0001-7814-0554)
- Gerald P. Dicen (ORCID: https://orcid.org/0000-0002-3759-9825)
- Surya Gupta (ORCID: https://orcid.org/0000-0003-3643-0099)
- Pierre Sabatier (ORCID: https://orcid.org/0000-0002-9620-1514)
- Rosalie Vandromme (ORCID: https://orcid.org/0000-0001-7489-0219)
- Olivier Evrard (ORCID: https://orcid.org/0000-0002-3503-6543)
Institutions
- Institut polytechnique de Grenoble (FR)
- Centre National de la Recherche Scientifique (FR)
- University of Basel (CH)
- Université de Versailles Saint-Quentin-en-Yvelines (FR)
- Université Paris-Saclay (FR)
- Swiss Federal Institute for Forest, Snow and Landscape Research (CH)
- ETH Zurich (CH)
- Institut National de Recherche pour l'Agriculture, l'Alimentation et l'Environnement (FR)
- Institut des Géosciences de l'Environnement (FR)
- Laboratoire des Sciences du Climat et de l'Environnement (FR)
- Bureau de Recherches Géologiques et Minières (FR)
- Institut de Recherche pour le Développement (FR)
- Laboratoire Environnements, Dynamiques et Territoires de Montagne (FR)
- Institute of Terrestrial Ecosystems (CH)
- Université Savoie Mont Blanc (FR)
- Université Grenoble Alpes (FR)
Publication Details
- Journal
- Communications Earth & Environment
- Published
- 2026-11-07
- DOI
- https://doi.org/10.1038/s43247-026-04218-z
- Primary Topic
- Radioactive contamination and transfer
- Type
- article
- Field-Weighted Citation Impact
- 0.00
Funders
- Agence Nationale de la Recherche
- Schweizerischer Nationalfonds zur Förderung der Wissenschaftlichen Forschung