ABSTRACT
The uptake of radionuclides by plant roots constitutes the main pathway for the migration of radiocaesium from soil to humans, via food chain. In this study we assessed radiocaesium uptake by plant in order to piece together information on factors affecting uptake processes, particularly K supply and differential uptake among different plant species. Soil contaminated by the Chernobyl accident and forage from a semi-natural alpine grassland, situated in Tarvisio, Italy, were sampled during 1999. Under field conditions, 137Cs uptake for Graminaceae and Taraxacum officinale seem to behave in a comparable way. Higher 40K soil activity concentration leads to a lower 137Cs plant uptake, suggesting an inhibitory pattern of potassium on radiocaesium plants uptake. For forage samples, a similar tendency was observed. We analyzed the influence of the ratio of 137Cs/ 40K in soil on 137Cs plant uptake. Under field conditions, the ratio observed varied in a range of 0.5 to 1.3. For most of the species, at higher 40K soil concentration a lower 137Cs uptake was observed, a fact that reflects the resulting effect of the complexity of factors controlling ion absorption from soil.
ABSTRACT
In the present study we assessed the radiocaesium uptake by plants in order to piece together information on factors affecting the uptake processes, particularly K supply and plant species differences. Vegetation uptake from soil contaminated by the Chernobyl accident was compared at two semi-natural grasslands. The Cs/K discrimination factor (DF), which is often used to evaluate a plant's efficiency in absorbing nutrients from soil, was estimated. The obtained DF values (0.01 to 0.8) vary with K soil concentrations and plant species, indicating that the (40)K is more efficiently absorbed than (137)Cs. The soil-to-plant relationship was evaluated by means of the transfer factor (TF). The (137)Cs TF(sp) values obtained from separated plant species varied within the range of 0.016 to 0.400 (site 1) and 0.017 to 0.171 (site 2). When mixed grass samples were considered a large variation was observed, mainly for site 1. The (137)Cs TF(mix) ranges were: 0.018 to 0.250 for site 1 and 0.017 to 0.167 for site 2. These values fall within the range of TFs commonly reported (0.0001-1). Our present data suggest that these pastures are apt for forage use. Different plant species presented different individual behavior regarding their (137)Cs TF(sp) when the (40)K soil activity concentration was taken in account. For most of the species analyzed, we observed a gradual decrease in the individual (137)Cs TF(sp) when the (40)K soil activity concentration was increased, with the exception of Taraxacum officinale at one of the sampling sites.
