Kerguelen Islands Fjord: detection of traces of radioactivity linked to French nuclear tests and lead originating from South Africa
The Cook Glacier, which covers part of the main island of the Kerguelen Archipelago (French Southern and Antarctic Lands), has been melting at an accelerated rate since the 1960s as a result of global warming. The fjord of Table Bay – a system fed with water and sediments by melting ice – constitutes an ideal archive of environmental changes in this region.
Analysis of a sediment core collected from this fjord in 2009 during an expedition by the Marion Dufresne (French Oceanic Fleet, FOF) has revealed, for the first time in the southern Indian Ocean, the presence of traces of nuclear fallout associated with the nuclear tests carried out by France between 1966 and 1974 in Polynesia, which has enabled the age model of this sedimentary sequence to be validated and refined.
Indeed, in addition to the 137Cs fallout associated with all atmospheric nuclear tests, traces of plutonium exhibiting an isotopic signature (240Pu/239Pu) consistent with that attributed to the French tests were found there. These results were corroborated by the use of two reference techniques for plutonium analysis (accelerator mass spectrometry, AMS, and inductively coupled plasma mass spectrometry, ICP-MS), which yielded consistent results. The presence of other anthropogenic contaminants on this isolated island and their evolution over the past few decades has been accurately reconstructed thanks to this validated dating.
Deposition of heavy metals and persistent organic pollutants (POPs) in fjord systems during ice melting was investigated with a sediment core collected in Table Fjord from Kerguelen Island (49° 33.8 S–69° 13.9 E) situated in the Southern Indian Ocean. © Environ. Sci. Technol. 2026, 60, 8, 6635-6648
We were thus able to demonstrate the impact of the melting of the Cook Ice Cap on the remobilisation of anthropogenic lead, the transport of which to the fjord across the proglacial lake was facilitated by the melting ice. Analysis of the trajectories of air masses in the region and of the isotopic signature of the lead found there indicates that it is associated with historical contamination, likely linked to industrial activities in South Africa and the rise in the consumption of leaded petrol in the region from the 1940s onwards. A review of the literature also indicates that South Africa is the main source of air pollution in this region.
Analysis of a wide range of contaminants has revealed more recent contamination, dating from 2001, with arsenic, molybdenum, antimony and various persistent organic pollutants (POPs). Thus, all the POPs tested were detected only in the most recent sediment layer (2005–2007). These include light PAHs and polybrominated diphenyl ethers (PBDEs; used in particular as flame retardants in plastics and textiles), which supports the hypothesis of their long-range transport on a global scale or from South Africa.
In future, these findings—which corroborate other evidence regarding the long-range transport of contaminants to the farthest corners of the globe—could be updated through the analysis of other sedimentary records collected more recently.
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These results were made possible thanks to collaboration between various laboratories in France (LSCE/Laboratory of Climate and Environmental Sciences, METIS/Environmental Media, Transfers and Interactions in Hydrosystems and Soils, GEODE/Environmental Geography), the University of Basel (Switzerland), the University of Vienna (Austria) and the University of Quebec at Trois-Rivières (Canada).
Reference
Xu-Yang, Y., Evrard, O., Foucher, A., Chaboche, P.A., Lefèvre, I., Taraconat, N., Kobler Waldis, J., Alewell, C., Merchel, S., Steier, P., Michel, E., Thiébault, T., Chapron, E., Chassiot, L., Ayrault, S. (2026). Refining our knowledge of radionuclide fallout from global and French nuclear weapon tests to study the sediment and legacy contaminants transport in Kerguelen archipelago fjord system affected by ice melting. Environmental Science & Technology 60(8), 6635-6648.
Contact
Olivier Évrard, LSCE-IPSL •
