Unveiling the origins and transport processes of radioactive pollutants downstream from a former U-mine site using isotopic tracers and U-238 series disequilibrium

• Published in: Journal of hazardous materials Vol. 472; p. 134416
• Main Authors: Geng, Tingting, Mangeret, Arnaud, Péron, Olivier, Suhard, David, Gorny, Josselin, Darricau, Louise, Le Coz, Mathieu, Ait-ouabbas, Nicolas, David, Karine, Debayle, Christophe, Blanchart, Pascale, Montavon, Gilles, Gourgiotis, Alkiviadis
• Format: Journal Article
• Language: English
• Published: Netherlands Elsevier B.V 05.07.2024; Elsevier
• Subjects: Pb stable isotopes; Physics; U-contaminated environment; U-series disequilibrium; Uranium mines; U-series disequilibrium; Uranium mines; Pb stable isotopes; U-contaminated environment
• ISSN: 0304-3894; 1873-3336
• DOI: 10.1016/j.jhazmat.2024.134416

High U concentrations (reaching up to 14,850 mg ⋅ kg−1), were determined in soils and sediments of a wetland downstream of a former U mine in France. This study aims to identify the origin of radioactive contaminants in the wetland by employing Pb isotope fingerprinting, (234U/238U) disequilibrium, SEM, and SIMS observations. Additionally, information about U and 226Ra transport processes was studied using U-238 series disequilibrium. The results of Pb fingerprinting highlighted inherited material inputs of different U-mines with mainly two types of U-ores: i) pitchblende (UO2), and ii) parsonsite (Pb2(UO2)(PO4)2). Moreover, significant disequilibrium of (230Th/238U) and (226Ra/230Th) activity ratios highlighted the mobility of 238U and 226Ra in the wetland, primarily driven by the water table fluctuations. Finally, this work uncovered a limitation of Pb isotope fingerprinting in the case of parsonsite materials, as the high natural Pb content of this mineral may hide the uranogenic Pb signature in the samples. [Display omitted] •U-Pb isotopic tracing efficiently identified U-mining input in the environment.•Pitchblende and torbernite exhibit high radiogenic Pb signature.•Parsonsite lacks radiogenic Pb signature due to its high natural Pb content.•SIMS analysis confirm the presence of pitchblende and neoformed U-bearing phases.•U-series disequilibrium highlights U and Ra mobilities in the wetland.