Using Radionuclides from Atmospheric Deposition in the Study of Their Geochemical Migration in Soils: Review

This article provides an overview of the results of long-term studies of the migration of radionuclides in the composition of lysimetric waters (leachates). It considers peculiarities of lysimeter-based studies at various stages of advancement in radioecology. It is noted that, for a long time, the use of lysimeters was limited to a low level of radionuclides in soil solutions; the studies gained momentum after the Chernobyl deposition (1986). Release of radionuclides to leachates is shown to be the greatest in the forest and coniferous phytocenoses, in particular, and the least in meadows and agrophytocenoses. The intensity of radionuclide migration in the leachates is the maximum during the initial period after atmospheric deposition in the long-term dynamics and during summer in the seasonal dynamics. Gravity flow was assessed in redistribution of radionuclides across the soil profile. The annual flux with vertical subsurface flow varies depending on edaphic and climatic conditions; time elapsed after the deposition; and thickness and depth of the layer. The annual flux ranges from tenths of a percent to a low percentage of the forest floor and from hundredths to tenths of a percent from a 0- to 20-cm layer of the total radionuclide inventory in these layers. The relative flux of 90 Sr significantly surpasses that of 137 Cs. From 70 to 90% of radionuclides ( 90 Sr, 137 Сs, 238 Pu, 239+240 Pu, and 241 Am) are present in soil solution in the form of radionuclide–organic compounds of various molecular weights.