Impact of soil moisture on cesium uptake by plants: Model assessment

Computational models of radioisotopes soil-to-plant transfer are an essential component of decision support systems for nuclear emergency and assessment impact of nuclear accidents on human beings and the environment. The soil water regime impact on cations behavior in the «soil-plant » system. Therefore, relationships between radioisotopes accumulation by plants and soil moisture should be included in the computational models. A kinetic model for simulation of Cs+ root uptake under alteration of soil moisture content in soil is presented in this paper. The model simulates Cs+ and K+ diffusion from bulk soil into rhizosphere under alteration of water content. The model results show a drop of Cs+ and K+ concentration in the rhizosphere with decreasing soil moisture. The magnitude of enhanced root uptake of Cs+ with soil moisture alteration depends on the exchangeable potassium content and soil texture. The Cs+ root uptake rate has a maximum at 60%-80% of field capacity under sufficient and high exchange potassium content. A similar dependence should also be seen for the RCs soil-to-plant transfer factor. The results indicate the importance of soil water content for modification of the RCs accumulation by plants and the necessity to include this factor into an appropriate semi-mechanistic model.