Modelling radionuclide behaviour in deep lakes of Italian Alpine region: Seasonality effects and comparison with deep volcanic lakes of Central Italy

摘要

The present report describes the results of research carried out following the Chernobyl accident to analyze the behavior of radionuclides in some Italian lakes. The lacustrine systems examined were the volcanic lakes Bolsena, Bracciano, and Vico (central Italy) and Lake Como (northern Italy) whose drainage area is located in the Alpine region. The average residence times of Cs-137 in water of volcanic lakes are much higher than the radionuclide residence time in lake Como. As quantitative analyses can show, the differences between the mean water retention times of the examined lakes do not suffice to explain this occurrence. Some peculiar seasonal effects (thermal stratification of water and ice/snow melting in lake drainage area) and high sedimentation rates are responsible of Cs-137 efficient removal from water of lake Como.