Understanding radionuclide behaviour at the plant-soil interface to direct bioremediation strategies for contaminated land

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Plants efficiently accumulate inorganic elements from their environment, which they need for growth. However, mineral nutrient accumulation mechanisms are often non-selective, causing uptake of potentially toxic elements, including radionuclides, when these contaminants are present at elevated concentrations. Some plants are able to tolerate radionuclide contaminated environments, either by inhibiting accumulation by mediating chemical changes that reduce radionuclide bioavailability and also reduce mobilisation through the soil solution (phytostabilisation), or by enhancing bioavailability to allow bulk accumulation of radionuclides (phytoextraction). However, many aspects of sub-surface radionuclide behaviour in response to plant and associated microbial presence are poorly understood. While it is clear that plants are able to accumulate a wide range of radionuclides, a detailed biogeochemical analysis of the influence of plants to selected radionuclides is lacking. The aim of this project is therefore to understand sub-surface speciation of selected radionuclides (including Sr-90, Cs-137, isotopes of U and Pu) in response to the presence of plants and associated microorganisms, and the mechanisms of radionuclide bio-accumulation and bio-stabilisation, in order to inform contamination management pathways and bioremediation potential. By combining environmental radiochemistry and soil-plant ecology approaches, this project, in collaboration with Sellafield Ltd, will generate a detailed characterisation of the soil-plant microbiome of radionuclide contaminated soils in order to gain a more accurate understanding of radionuclide behaviour and how this determines radionuclide bioavailability. These approaches will aid quantification of the broader ecological consequences of sub-surface soil radionuclide contamination, and in particular how changes in radionuclide bioavailability correlate with mobilisation and transfer into vegetation.