Fukushima and Chernobyl: similarities and differences of radiocesium behavior in the soil-water environment

<p>In the wake of Chernobyl and Fukushima accidents radiocesium has become a radionuclide of most environmental concern.<strong> </strong>The ease with which this radionuclide moves through the environment and is taken up by plants and animals is governed by its chemical forms and site-specific environmental characteristics. Distinctions in climate and geomorphology, as well as ¹³⁷Cs speciation in the fallout result in differences in migration rates of ¹³⁷Cs in the environment and rates of its natural attenuation. In Fukushima areas ¹³⁷Cs was found to be strongly bound to soil and sediment particles, its bioavailability being reduced as a result. &#160;Up to 80% of the deposited ¹³⁷Cs on the soil were reported to be incorporated in hot glassy particles (CsMPs) insoluble in water. Disintegration of these particles in the environment is much slower than of Chernobyl-derived fuel particles. The higher annual precipitation and steep slopes in Fukushima contaminated areas are conducive to higher erosion and higher total radiocesium wash-off. Typhoons Etou in 2015 and Hagibis in 2019 demonstrated the pronounced redistribution of ¹³⁷Cs on river watersheds and floodplains, and in some cases natural self-decontamination occurred. Among the common features in ¹³⁷Cs behavior in Chernobyl and Fukushima is a slow decrease in ¹³⁷Cs activity concentration in small, closed, and semi-closed lakes and its particular seasonal variations: increase in summer and decrease in winter.</p>