Distribution and Dynamics of Radionuclides in the Chernobyl Cooling Pond

Reconstruction of the Long-Term Dynamics of Particulate Concentrations and Solid–Liquid Distribution of Radiocesium in Three Severely Contaminated Water Bodies of the Chernobyl Exclusion Zone Based on Current Depth Distribution in Bottom Sediments

“…Some minor deviations can be noticed for Lake Azbuchin and CP, yet not contradicting the general trend. There are also secondary maxima in the 137 Cs activity concentrations, which are likely to be associated with water level manipulation and other remediation activities, as well as changes in the ChNPP operational mode [18].…”

“…The obtained 137 Cs core profiles provided a basis for reconstructing long-term dependence of its particulate activity concentration in the water column. This is especially important since throughout the years after the accident, this crucial characteristic of radioactive contamination was not monitored on a regular basis but measured only occasionally in selected water bodies within some projects [18,44,45,53].…”

“…In the calculations of с , we used the 137 Cs effective dispersion coefficient in soil 0.1 cm 2 /y, which corresponds to the lower bound of the range of Deff values in the ChEZ soils [33,36,54]. The low value of Deff was taken since 137 Cs deposited on these catchments was incorporated in persistent fuel particles characterized by slow disintegration and low mobility [18,55,56]. The reconstructed time dependences of 137 Cs particulate activity concentration in the three studied water bodies since the accident are shown in Figure 4.…”

“…Despite a vast number of studies of radionuclide behavior in such water bodies, most of them lacked broad temporal coverage and did not deal with long-term changes in radionuclide concentrations. This is especially true for particulate concentrations in the Chernobyl zone water bodies, with the monitoring system primarily focused on dissolved concentrations as being the most important Land 2022, 11, 29 2 of 14 in terms of radionuclide mobility and bioavailability [17,18]. In our work, particulate concentration as a function of time is reconstructed from radionuclide depth distribution in bottom sediments, assuming certain conditions are satisfied for sediment column formation.…”

Long-term prediction of $$^{137}$$Cs in Lake Onuma on Mt. Akagi after the Fukushima accident using fractional diffusion model

“…Therefore, the 137 Cs activity concentrations of the lake water and pond smelt in Lake Onuma were measured for a long period of 5.4 years after the accident 10 .The main processes governing 137 Cs activity concentration after the accident can be categorized into an initial phase and mid-, to long-term phases, corresponding to the post-accident phase. The most important processes in the initial phase are the atmospheric fallout of 137 Cs on the water surface, subsequent sorption and fixation by sediments, and their settling on the bottom [13][14][15] . Besides pure fitting, a parameter for a given lake and radionuclide in the diffusion model can be estimated using characteristics with clear meaning 137 Cs deposition, effective diffusion coefficient, and distribution coefficient 11 , and thus predictions of 137 Cs long-term dynamics in a lake can be provided immediately after the accident using previously measured values of the characteristics, literature data or expert judgments.…”