New Insights into Pb Isotope Fingerprinting of U-Mine Material Dissemination in the Environment: Pb Isotopes as a Memory Dissemination Tracer

Alkiviadis Gourgiotis (1) , Arnaud Mangeret (1) , Gérard Manhès (2) , Pascale Blanchart (3) , Lucie Stetten (4) , Guillaume Morin (4) , Pierre Le Pape (4) , Pierre Lefebvre (4) , Mathieu Le Coz (1) , Charlotte Cazala (1)

1 IRSN/PSE-ENV/SEDRE/LELI - Laboratoire de recherche sur le devenir des pollutions de sites radioactifs
2 IPGP - Institut de Physique du Globe de Paris
3 IRSN/PSE-ENV/SEDRE/USDR - Unité d'expertise des sites et des déchets radioactifs
4 IMPMC - Institut de minéralogie, de physique des matériaux et de cosmochimie

Stable Pb isotope ratios were measured and compared to U distributions in three soil cores located in a wetland highly impacted by water discharge of a former U-mine. Pb isotope ratios showed notable alignments in binary mixing plots demonstrating the dissemination of radioactive-enriched material from the U-mine. Thanks to theses alignments and to the measurement of 204Pb isotope, a precise characterization of the Pb isotope composition of the U-ore was performed without the use of U-ore samples. The well-defined end-members with the help of a reevaluated isotope mixing model allowed the accurate determination of the radiogenic Pb percentages in the cores that were overall found to be >50%. Non-correlated distributions of radiogenic 206Pb and U are observed in several of the wetland soil samples studied. They reveal post-depositional U redistribution explained by major U speciation changes due to redox cycling in the wetland. On the contrary, the radiogenic 206Pb showed no or small post-depositional mobility and thus can be considered to be a memory tracer of the dissemination of U-rich radioactive material: even after an important U loss, the radiogenic 206Pb is able to reveal past contamination by U-rich materials.

Domaines: Sciences de l'environnement

Alkiviadis Gourgiotis, Arnaud Mangeret, Gérard Manhès, Pascale Blanchart, Lucie Stetten, et al.. New Insights into Pb Isotope Fingerprinting of U-Mine Material Dissemination in the Environment: Pb Isotopes as a Memory Dissemination Tracer. Environmental Science and Technology, 2019, 54 (2), pp.797-806. ⟨10.1021/acs.est.9b04828⟩. ⟨hal-03041326⟩