Modelling the behaviour of uranium-series radionuclides in soils and plants taking into account seasonal variations in soil hydrology

• Kinetic model of radionuclide transport in soils and uptake by plants.
• Takes soil hydrology and redox conditions into account.
• Applicable to the whole U-238 chain, including Rn-222, Pb-210 and Po-210.
• Demonstrates intra-season and inter-season variability on timescales up to thousands of years.

In a previous paper, a mathematical model for the behaviour of 79Se in soils and plants was described. Subsequently, a review has been published relating to the behaviour of 238U-series radionuclides in soils and plants. Here, we bring together those two strands of work to describe a new mathematical model of the behaviour of 238U-series radionuclides entering soils in solution and their uptake by plants. Initial studies with the model that are reported here demonstrate that it is a powerful tool for exploring the behaviour of this decay chain or subcomponents of it in soil-plant systems under different hydrological regimes. In particular, it permits studies of the degree to which secular equilibrium assumptions are appropriate when modelling this decay chain. Further studies will be undertaken and reported separately examining sensitivities of model results to input parameter values and also applying the model to sites contaminated with 238U-series radionuclides.