Modelling the long-term dynamics of radiocaesium in closed lakes

On the radiocesium carbonate barrier in organics-rich sediments of Lake Juodis, Lithuania

“…Modeling studies of the radiocesium uptake and migration in sediments deal with an equation of the radiocesium convectiveedispersive transport and use a number of simplifications and assumptions (Robbins and Jasinski, 1995;Smith and Comans, 1996;Smith et al, 2000;Bulgakov et al, 2002;Fesenko et al, 2004;Monte et al, 2005). They are too formal and do not account for possible effects of organics content of the sediments.…”

“…They are too formal and do not account for possible effects of organics content of the sediments. Nevertheless, fitting procedures of simulated data are sometimes applied to the sediments of rather high organics content: w39% organic matter in Robbins and Jasinski (1995) and w40% in Bulgakov et al (2002).…”

“…It means that studying a net uptake of the radionuclide by the sediment models deal with a very small part of its free-ion concentration (a total radionuclide concentration in dissolved phase in water divided by the retardation factor). As a result, such an approach leads to the underestimation of the process and modeling data are unable to explain results (especially the fast phase) of laboratory experiments on sediment incubation under aerobic conditions (Smith et al, 2000) as well as measured in situ radiocesium vertical profiles (Smith et al, 2000;Bulgakov et al, 2002;Monte et al, 2005). Laboratory studies of radiocesium sorption kinetics by suspended particles (Robbins et al, 1992;Robbins and Jasinski, 1995;Stephens et al, 1998;Ciffroy et al, 2001) are always carried out in stirred water.…”

Effects of Thermodynamical Processes on Radiocesium Behavior in Lake Tapeliai / Termodinaminių Procesų Įtaka Radiocezio Elgsenai Tapelių Ežere

“…Tai susiję su tuo, kad ežerai yra labiausiai prieinamos gėlo vandens saugyklos šaltinis. Radiocezio aktyvumas apskaičiuojamas visam ežero tūriui ir toliau taikomas modeliuojant jo migraciją ežero dugno nuosėdo-se (Bulgakov et al 2002;Monte et al 2005;Putyrskaya, Klemt 2007). Manoma (Alberts et al 1979;Davison et al 1993a;Avery 1999), kad padidėjusią radiocezio aktyvumo koncentraciją vandens hipolimneone paprastai sukelia jo dalelių remobilizacija iš ežero dugno nuosėdų, esant anoksinėms sąlygoms.…”

137Cs in Lake Tapeliai, Lithuania

“…These models relate the behaviour of radionuclides in lakes to the relevant environmental characteristics and use generic values for the transfer parameters which are not specific to physical and chemical fundamental processes. Radiocesium concentrations in water averaged over the entire volume of the lake are further used in the modelling of its migration processes in lake sediments [11][12][13]. However, earlier Santschi et al [14,15] evidenced that after the Chernobyl fallouts in deep thermally stratified lakes, the processes of radiocesium direct sorption onto surface sediments in shallow epilimnetic parts of lakes could significantly eliminate its flux to hypolimnion.…”