Availability of radiocasium in plant from soil: facts, mechanism and modelling

Radiocaesium is an isotope that can enter the food chain after having been absorbed by
plants from soil. Our ability to predict the consequences of an accidental release of 137Cs
depends mainly on the level of understanding of the mechanisms involved in 137Cs
interactions with different components of agricultural and natural ecosystems and their
formalization into predictive models. In this study the impact of some environmental and
physiological factors, such as root density and presence of AM (Arbuscular mycorrhizal)
fungal hyphae, on the ability of plants to uptake and accumulate radiocaesium through the
roots was investigated. Three plant species were used: pea, soybean and oats. Experimental
data suggested that, as roots explore new volumes of soil during growth, the plant will
continue to accumulate this radionuclide at high rates in the early stages of ontogenesis. If
plants are established on a contaminated site they may not be able to remove all of this
radionuclide from soil, especially if a substantial amount of the radionuclide has been leached
below the root zone which is commonly 30-40 cm in depth. Laboratory experiments indicate
that certain plants may be able to remove radionuclides, especially 137Cs, from soil over a
time period of 5-20 years.