Fundamental Research Division
The DRF at the CEA assemble approximately 6,000 scientists since January 2016.
Découvertes et avancées | Scientific result | Environment | Dating | Climate
The LSCE (CEA-CNRS-UVSQ) and the EDYTEM laboratory (CNRS - Université Savoie Mont Blanc - Ministère de la Culture) have established a comprehensive overview of cesium-137 fallout observed in sedimentary archives around the world. This database makes it possible to improve the dating of sedimentary cores.
For several decades now, the study of sediments accumulated at the bottom of lakes and oceans has been widely used to reconstruct the evolution of climate and the environment during the 20th century, a period strongly impacted by socio-environmental changes. These natural archives can notably be used to assess the trajectory, magnitude and resilience of terrestrial ecosystems and continental hydrological systems faced with climate change, human activities and contamination-related pressures.
The dating of these natural archives is the first step in these paleoenvironmental reconstructions. 137Cs, an artificial radionuclide that was emitted during atmospheric nuclear testing in the 1960s as well as during the Chernobyl (1986) and Fukushima (2011) accidents, is one of the time markers traditionally used to date these sediment cores.
Until now, no global overview was available to characterize the spatial distribution of 137Cs sources and thus avoid possible confusion regarding the attribution of sources that could lead to errors in dating, and consequently paleoenvironmental reconstructions.
To create this reference database, the authors compiled published data on nearly 1,350 sediment cores collected around the world. They were able to confirm that the peak in fallout related to atmospheric tests was observed across the globe, with contrasting 137Cs activities between the northern and southern hemispheres. The fallout from the Chernobyl and Fukushima disasters is mainly observed in Europe and on the Japanese peninsula. In addition to these regional sources widely described in the literature, this overview has highlighted more local sources of 137Cs. This includes discharges from the La Hague reprocessing plant in France, as well as some regional sources such as Chinese nuclear tests or discharges linked to incidents at the Sellafield nuclear power plant in the UK.
This overview and the associated database, completely free and open access, can now be used in future publications to facilitate and standardize the dating of sediment cores, especially in regions of the world where multiple 137Cs sources can be detected.
CEA is a French government-funded technological research organisation in four main areas: low-carbon energies, defense and security, information technologies and health technologies. A prominent player in the European Research Area, it is involved in setting up collaborative projects with many partners around the world.