Estimation of sedimentation rates based on the excess of radium 228 in granitic reservoir sediments. (October 2016)

• Record Type: Journal Article
• Authors: Reyss, Jean-Louis; Mangeret, Arnaud; Courbet, Christelle; Bassot, Sylvain; Alcalde, Gilles; Thouvenot, Antoine; Guillevic, Jérôme
• Is Part Of: Journal of environmental radioactivity. Volume 162/163(2016:Oct.)
• Page Start: 8
• Page End: 13
• Publication Date: 2016-10
• Subjects: Recent sediments -- Dating -- Uranium mine -- Radium 228 -- Granitic catchment; Radioactivity -- Periodicals; Radiation, Background -- Periodicals; Radioecology -- Periodicals; Radioactive pollution -- Periodicals; Environmental Pollutants -- Periodicals; Radioactive Pollutants -- Periodicals; Radioactivity -- Periodicals; Radioécologie -- Périodiques; Pollution radioactive -- Périodiques; Fond de rayonnement -- Périodiques; 539.752
• DOI: 10.1016/j.jenvrad.2016.04.032
• Languages: English
• ISSNs: 0265-931X

Abstract

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-known 210 Pb excess ( 210 Pbex ) method cannot be used for quantifying sedimentation rates in uranium-enriched catchments, as large amounts of 210 Pb produced by weathering and human activities may dilute the atmospheric 210 Pb. As an alternative dating method in these cases, we propose an original method based on 232 Th 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 of 228 Ra excess ( 228 Raex ) with depth in two long cores yields sedimentation rates of 2.4 and 5.2 cm yr −1 respectively. These sedimentation rates lead to the attribution of the 137 Cs activity peak observed at depth to the Chernobyl fallout event of 1986. The 228 Raex method was also applied to two short cores which did not display the 137 Cs peak, and mean sedimentation rates of 2.1 and 4.0 cm y −1 were deduced. The proposed method may replace the classical radiochronological methods ( 210 Pbex, 137 Cs) to determine sedimentation rates in granitic catchments. Graphical abstract: Highlights: The well-known 210 Pbex sediment dating method cannot be applied in the studied system. An original dating method of lake sediments based on radium 228 excess is proposed. The 228 Raex method led to the attribution of the 137 Cs peak to the Chernobyl fallout. Lake sediments younger than 1986 can be dated according to the 228 Raex method.