Modelling 137Cs uptake in plants from undisturbed soil monoliths

Area of Science:

• Environmental Science
• Radiochemistry
• Plant Physiology

Background:

• Cesium-137 (137Cs) is a significant radionuclide contaminant affecting agricultural ecosystems.
• Understanding plant uptake mechanisms is crucial for assessing food chain contamination.
• Lysimeter studies provide controlled environments to investigate radionuclide behavior in soils.

Purpose of the Study:

• To evaluate a mechanistic model for predicting 137Cs uptake in different crops.
• To assess the influence of soil solution composition, particularly potassium (K) concentration, on 137Cs uptake.
• To compare the predictive accuracy using bulk versus rhizosphere soil solution data.

Main Methods:

• Application of a mechanistic model to lysimeter data from artificially contaminated soils.
• Cultivation of beans, ryegrass, and lettuce across five soil types over 3-5 years post-contamination.
• Monitoring of soil solution composition (137Cs and K concentrations) in bulk and rhizosphere soil.

Main Results:

• The model explained 17% (beans) to 91% (lettuce) of 137Cs variation, with rhizosphere data yielding better predictions than bulk soil data.
• Predicted K concentrations in the rhizosphere were significantly lower than in bulk soil.
• The model underpredicted 137Cs uptake in ryegrass and at soil solution K concentrations below 1.0 mM.

Conclusions:

• Plant 137Cs uptake can be predicted from soil solution composition under adequate potassium (K) nutrition.
• Significant uncertainties exist in predicting 137Cs uptake when soil solution K is below 1.0 mM.
• The model's performance varies significantly among crop species and soil conditions, highlighting the need for further refinement.