Alex Chapman

PhD student, Associate Lecturer

Research Overview

My research project aims to investigate the biological availability of radionuclides for plant uptake in contaminated soils using the Diffusive Gradients in Thin Films (DGT) technique. Radionuclide contamination of the soil environment through human activity represents a major human exposure pathway to radioactivity following plant uptake, redistribution throughout the food chain and subsequent consumption of agricultural produce. Understanding the bioavailability of these radionuclides represents the first step in modelling the long-term potential transfer of the radiation dose following plant uptake and therefore characterising and quantifying the radiological risk posed to human health.

Specifically, my research considers the long-lived (half-life > 2 x105 years) fission products 79Se, 99Tc and 129I, in addition to U isotopes, all of which have been identified as being particularly important in long-term safety assessments of nuclear waste disposal. DGT provides an in-situ, time-integrated means of determining the concentration of labile species in soils, sediments and aqueous solutions based upon the kinetics of diffusion through a hydrogel and subsequent immobilisation by a selective binding agent. The DGT technique has been utilised to investigate bioavailability based upon its demonstrated ability to mimic plant uptake of a range of metals.

The objective of my research is to advance our understanding of the biogeochemical behaviour of radionuclides in terms of their soil binding and release kinetics which is critical in determining availability for plant uptake. I hope to establish whether short-term measurements collected from controlled laboratory experiments over a three year period can be used to predict the long-term bioavailability of radionuclides in soils by testing the models in soils sampled from the Chernobyl Exclusion Zone.