Modelling ~(137)Cs uptake in plants from undisturbed soil monoliths

摘要

A model predicting ~(137)Cs uptake in plants was applied on data from artificially contaminated lysimeters. The lysimeter data involve three different crops (beans, ryegrass and lettuce) grown on five different soils between 3 and 5 years after contamination and where soil solution composition was monitored. The mechanistic model predicts plant uptake of ~(137)Cs from soil solution composition. Predicted K concentrations in the rhizosphere were up to 50-fold below that in the bulk soil solution whereas corresponding ~(137)Cs concentration gradients were always less pronounced. Predictions of crop ~(137)Cs content based on rhizosphere soil solution compositions were generally closer to observations than those based on bulk soil solution composition. The model explained 17% (beans) to 91% (lettuce) of the variation in ~(137)Cs activity concentrations in the plants. The model failed to predict the ~(137)Cs activity concentration in ryegrass where uptake of the 5-year-old ~(137)Cs from 3 soils was about 40-fold larger than predicted. The model generally underpredicted crop ~(137)Cs concentrations at soil solution K concentration below about 1.0 mM. It is concluded that ~(137)Cs uptake can be predicted from the soil solution composition at adequate K nutrition but that significant uncertainties remain when soil solution K is below 1 mM.