EGU23-1303, updated on 21 Mar 2023
https://doi.org/10.5194/egusphere-egu23-1303
EGU General Assembly 2023
© Author(s) 2023. This work is distributed under
the Creative Commons Attribution 4.0 License.

Was the 137Cs contained in Saharan dust deposited across Europe in March 2022 emitted by French nuclear tests in Algeria?

Olivier Evrard1, Octave Bryskere1, Charlotte Skonieczny2, Anthony Foucher1, Rémi Bizeul1, Thomas Chalaux Clergue1, Jean-Sébastien Barbier1, Jean-Eudes Petit1, José A. Corcho‑Alvarado3, Stefan Röllin3, Pierre-Alexis Chaboche4, and Germán Orizaola5
Olivier Evrard et al.
  • 1CNRS-CEA, LSCE - Laboratoire des Sciences du Climat et de l'Environnement, Gif-sur-Yvette, France (olivier.evrard@lsce.ipsl.fr)
  • 2Université Paris-Saclay, CNRS, GEOPS, Orsay, France
  • 3Nuclear Chemistry Division, Spiez Laboratory, Federal Office for Civil Protection, Spiez, Switzerland
  • 4International Research Fellow of Japan Society for the Promotion of Science (Postdoctoral Fellowships for Research in Japan (Standard), Institute of Environmental Radioactivity, Fukushima University, Japan
  • 5IMIB- Biodiversity Research Institute (Univ. Oviedo-CSIC-Princip. Asturias), Mieres, Zoology Unit, Department Biology Organisms and Systems, University of Oviedo, Oviedo, Spain

Air masses loaded with mineral dust and originating from the Sahara arrive frequently in Europe, which has multiple impacts on global and regional cycles. However, the occurrence of these processes may further accelerate in the future in response to climate change, and more knowledge is therefore required on the characteristics of the particles transported during these massive dust transport and deposition episodes. Furthermore, questions arise regarding the content of this dust in radionuclides, in relationship with the atmospheric nuclear bomb testing conducted around the world between the 1950s and the 1970s in general, and those tests conducted by France in the Sahara in the early 1960s in particular.

The Saharan dust episode that took place from 13th to 16th March 2022 led to the occurrence of dense dust deposition across multiple European countries, which raised concerns among the population regarding the potential radioactivity content of this dust. To address this question with a representative sample set, a participative science campaign to collect dust across Europe was launched on Twitter on 17th March 2022. Thanks to this initiative, 110 dust samples could be collected along a transect from Southern Spain to Austria.

This unique sample bank was regrouped at University Paris-Saclay, France, to conduct a set of physico-chemical analyses on a selection or on the totality of these dust samples including particle size, colourimetry, mineralogy and fallout radionuclides.

Backward trajectories of air masses that have led to these deposits were calculated, and this analysis confirm their potential origin from Algeria. 137Cs was detected in all dust samples, with variable activity concentrations. A strong relationship was found between the particle size of the analysed particles and the 137Cs activity concentrations, which is consistent with the literature on this topic. Particle size was found to decrease with increasing distances from the source. The colour and mineralogy analyses demonstrated that the dust collected in Austria showed different properties than those samples collected in Spain, France, Luxembourg and Germany, which likely indicates that this material did not fully consist of Saharan dust deposited during the March 2022 episode. Accordingly, the following interpretations did not take the properties of Austrian dust into account.

The mineralogical analyses confirmed the potential origin of the dust from the Maghreb region, including a vast area in Southern Morocco and Southern Algeria. In contrast, the analysis of plutonium isotopic ratios (240Pu/239Pu) and 137Cs/239+240Pu activity ratios, which provide diagnosis tools to investigate the source of artificial radionuclides, in a selection of dust samples collected between Southern Spain and Luxembourg showed that the dust signature was consistent with that of the global fallout largely dominated by the nuclear tests conducted by the USA and the Soviet Union. The 137Cs contained in the dust transported and deposited during this episode was therefore very likely not associated with the French nuclear tests conducted in the early 1960s in Sahara.

In the future, elemental geochemistry analyses will provide additional information on their source provenance. All results will also be published in open-access database and disseminated to the public.

How to cite: Evrard, O., Bryskere, O., Skonieczny, C., Foucher, A., Bizeul, R., Chalaux Clergue, T., Barbier, J.-S., Petit, J.-E., Corcho‑Alvarado, J. A., Röllin, S., Chaboche, P.-A., and Orizaola, G.: Was the 137Cs contained in Saharan dust deposited across Europe in March 2022 emitted by French nuclear tests in Algeria?, EGU General Assembly 2023, Vienna, Austria, 24–28 Apr 2023, EGU23-1303, https://doi.org/10.5194/egusphere-egu23-1303, 2023.

Supplementary materials

Supplementary material file