Dating of recent sediments from Lago Maggiore and Lago di Lugano (Switzerland/Italy) using 137Cs and 210Pb

• Published in: Journal of environmental radioactivity 2020-02, Vol.212, p.106135-106135, Article 106135
• Main Authors: Putyrskaya, V., Klemt, E., Röllin, S., Corcho-Alvarado, J.A., Sahli, H.
• Format: Article
• Language: English
• Subjects: 137Cs; 210Pb; Dating; Event layer; Lake sediments; Mass accumulation rate
• ISSN: 0265-931X; 1879-1700
• DOI: 10.1016/j.jenvrad.2019.106135

This paper presents the results of 137Cs and 210Pb dating of sediments from the northern and western basins of Lago Maggiore and the southern basin of Lago di Lugano. Vertical distributions of 137Cs in sediment cores taken in 2017/18 were compared to those of the sediment cores taken almost two decades ago at the same positions. This comparison showed that 137Cs peaks do not alter their shape significantly over time and 137Cs remains a reliable time-marker for many decades. 210Pb dating using for the first time the piecewise “constant rate supply” (CRSPW) model constrained with 137Cs time-markers is performed for sediment cores of Lago Maggiore and Lago di Lugano. “Event-linked” mass accumulation rates (MARs) were derived from the CRSPW model. In combination with the dry bulk density, organic matter content, 40K and 210Pb activity concentrations, these “event-linked” MARs were used for the identification of one or more event layers (turbidites, detrital layers) in 1-cm thick sediment samples. “Continuous” mean MARs which are independent of the event layers were estimated: in Lago Maggiore sediment cores they are 0.066–0.090 g cm−2 yr−1; in Lago di Lugano they vary in the range of 0.032–0.057 g cm−2 yr−1 with higher values in the time interval 1963–1986 as compared to 1986–present. •137Cs remains a reliable time-marker in lake sediments for the next decades.•Necessity of using piecewise constant rate supply 210Pb model constrained with 137Cs.•Event-linked mass accumulation rates (MARs) as indicators for event layers.•Estimation of continuous MARs which are independent of event layers.