Plant and Soil Relationships of Uranium and Thorium Decay Series Radionuclides—A Review

TLDR

Radionuclides from the uranium and thorium decay series in terrestrial systems are of concern due to mining and nuclear fuel disposal, yet plant‑soil uptake mechanisms remain poorly understood, with most studies relying on concentration ratios that do not capture the fraction available to plants. The uptake and translocation of radionuclides such as 226 Ra may follow mechanisms analogous to calcium transport in plants.

Abstract

Abstract The behavior of radionuclides of the uranium (U) and thorium (Th) decay series in terrestrial systems is of interest because of environmental effects of mining and disposal activities related to nuclear power plant fuels. The soft‐plant relationships of U, Th, and polonium (Po), and some other daughter radionuclides, notably radium ( 226 Ra), are not well understood. Most studies have been concerned with relative uptake of these radionuclides by various plant species. Plant concentrations have been related to total contents of these radionuclides in the soil as a plant/soil concentration ratio (CR), even though the fraction of these radionuclides, which may be available to plants, is not well known. These CR values have been used to predict transport of radionuclides and other elements of interest through the food chain as well as for other purposes, including biogeochemical exploration for U. Little information is available on uptake and transport mechanisms of radionuclides in plants. However, the mechanisms relating to Ca uptake and translocation in plants may be similar to those of some radionuclides, especially 226 Ra. Soil chemical reactions of these radionuclides also have not been studied as well as those of plant nutrients, although knowledge of the effects of soil pH, soil texture, and organic matter content on uptake, as well as mobility in soil of these radionuclides, has been gained in recent years.