title: Estimation of sedimentation rates based on the excess of radium 228 in granitic reservoir sediments.
abstract: Knowledge of sedimentation rates in lakes is required to understand and quantify the geochemical processes involved in scavenging and remobilization of contaminants at the Sediment-Water Interface (SWI). The well-known210Pb excess (210Pbex) method cannot be used for quantifying sedimentation rates in uranium-enriched catchments, as large amounts of210Pb produced by weathering and human activities may dilute the atmospheric210Pb. As an alternative dating method in these cases, we propose an original method based on232Th decay series nuclides. This study focuses on an artificial lake located in a granitic catchment downstream from a former uranium mine site. The exponential decay of228Ra excess (228Raex) with depth in two long cores yields sedimentation rates of 2.4 and 5.2 cm yr-1respectively. These sedimentation rates lead to the attribution of the137Cs activity peak observed at depth to the Chernobyl fallout event of 1986. The228Raexmethod was also applied to two short cores which did not display the137Cs peak, and mean sedimentation rates of 2.1 and 4.0 cm y-1were deduced. The proposed method may replace the classical radiochronological methods (210Pbex,137Cs) to determine sedimentation rates in granitic catchments.
authors.affiliation: Laboratoire des Sciences du Climat et de l'Environnement, LSCE/IPSL, CEA-CNRS-UVSQ, Université Paris-Saclay, F-91198, Gif-sur-Yvette, France.
authors.forename: Jean-Louis
authors.initials: JL
authors.lastname: Reyss
authors.affiliation: Institut de Radioprotection et de Sureté Nucléaire (IRSN), PRP-DGE, BP 17, Fontenay-aux-Roses, 92262, France. Electronic address: arnaud.mangeret@irsn.fr.
authors.forename: Arnaud
authors.initials: A
authors.lastname: Mangeret
authors.affiliation: Institut de Radioprotection et de Sureté Nucléaire (IRSN), PRP-DGE, BP 17, Fontenay-aux-Roses, 92262, France.
authors.forename: Christelle
authors.initials: C
authors.lastname: Courbet
authors.affiliation: Institut de Radioprotection et de Sureté Nucléaire (IRSN), PRP-DGE, BP 17, Fontenay-aux-Roses, 92262, France.
authors.forename: Sylvain
authors.initials: S
authors.lastname: Bassot
authors.affiliation: Institut de Radioprotection et de Sureté Nucléaire (IRSN), PRP-DGE, BP 17, Fontenay-aux-Roses, 92262, France.
authors.forename: Gilles
authors.initials: G
authors.lastname: Alcalde
authors.affiliation: Laboratoire Microorganismes Génome et Environnement (LMGE), UMR CNRS 6023, Aubière, 63177, France.
authors.forename: Antoine
authors.initials: A
authors.lastname: Thouvenot
authors.affiliation: Institut de Radioprotection et de Sureté Nucléaire (IRSN), PRP-DGE, BP 17, Fontenay-aux-Roses, 92262, France.
authors.forename: Jérôme
authors.initials: J
authors.lastname: Guillevic
mesh_terms: D019015:Geologic Sediments / Q000737:chemistry*; D008956:Models, Chemical; D011883:Radium / Q000032:analysis*; D012822:Silicon Dioxide; D014875:Water Pollutants, Radioactive / Q000032:analysis*
chemical_list: D014875:Water Pollutants, Radioactive; C007886:granite; D012822:Silicon Dioxide; D011883:Radium
keywords: Dating; Granitic catchment; Radium 228; Recent sediments; Uranium mine