A worldwide meta-analysis (1977–2020) of sediment core dating using fallout radionuclides including $^{137}$Cs and $^{210}$Pb$_{xs}$

Anthony Foucher (1) , Pierre-Alexis Chaboche (1) , Pierre Sabatier (2) , Olivier Evrard (1)

1 GEDI - Géochimie Des Impacts
2 EDYTEM - Environnements, Dynamiques et Territoires de Montagne

Dating recent sediment archives (< 150 years) constitutes a prerequisite for environmental and climatic reconstructions. Radiocaesium ($^{137}$Cs) emitted during thermonuclear bomb testing (∼ 1950–1980) and nuclear accidents and the decrease in excess lead-210 ($^{210}$Pb$_{xs}$) with depth are often combined to establish sediment core chronology. Although these methods have been widely used during the last several decades, there is a lack of structured and comprehensive worldwide synthesis of fallout radionuclide analyses used for dating sediment cores in environmental and Earth sciences. The current literature overview was based on the compilation of 573 articles published between 1977 and 2020, reporting the collection of 1351 individual dating sediment cores (the dataset can be accessed at https://doi.org/10.1594/PANGAEA.931493; Foucher et al., 2021). This review was conducted in order to map the locations where $^{137}$Cs fallout events were detected. These included the thermonuclear bomb testing peak in 1963, the Chernobyl accident in 1986, the Fukushima accident in 2011, and 24 additional events identified at 112 sites that led to local or regional radioactive releases (e.g., Sellafield accidents, Chinese nuclear tests). When $^{210}$Pb$_{xs}$ records were used along with $^{137}$Cs data, detailed information on the $^{210}$Pb$_{xs}$ age–depth models were also synthesized. With the current growing number of studies analyzing sediment cores and the increasing interest in the deployment of sediment fingerprinting techniques including radionuclides as potential discriminant properties, this spatialized synthesis provides a unique worldwide compilation for characterizing fallout radionuclide sources and levels at the global scale. This synthesis provides in particular a reference of $^{137}$Cs peak attribution for improving the sediment core dating, and it outlines the main questions that deserve attention in future research as well as the regions where additional $^{137}$Cs fallout investigations should be conducted in priority.

Mots clés: Panoply

Domaines: Sciences de la Terre; Sciences de l'environnement

Anthony Foucher, Pierre-Alexis Chaboche, Pierre Sabatier, Olivier Evrard. A worldwide meta-analysis (1977–2020) of sediment core dating using fallout radionuclides including $^{137}$Cs and $^{210}$Pb$_{xs}$. Earth System Science Data, 2021, 13 (10), pp.4951-4966. ⟨10.5194/essd-13-4951-2021⟩. ⟨hal-03406193⟩