PhD in Environmental Geochemistry

This 3.5-year PhD studentship is open to EU, UK, and US applicants. The successful candidate will receive an annual tax-free stipend set at the UKRI rate (£20,780 for 2025/26; subject to annual uplift). We expect the stipend to increase each year. Tuition fees will be paid for home students and fee waivers might be available for international students. The start date is October 2026. Organic-rich wetlands have unique hydrological and biogeochemical properties that make them well suited for sequestering inorganic contaminants, including the toxic radionuclide uranium (U). In these environments, U is typically immobilised through adsorption onto organic matter and reduction of U(VI) species to less mobile U(IV) species. However, fluctuating hydrological and geochemical conditions can disturb these equilibria and potentially trigger uranium remobilisation. Understanding how these processes affect uranium mobility in environments that are particularly sensitive to environmental change is essential. This PhD project aims to unravel the mechanisms controlling uranium mobility in a coastal organic-rich wetland subject to fluctuating hydrogeochemical conditions. The project will specifically address: the influence of hydrogeochemical and redox fluctuations on uranium speciation and mobility the role of organic matter in controlling U mobility and U(IV)/U(VI) redox kinetics the formation, stability, and field-scale relevance of uranium-bearing colloids under variable hydrogeochemical conditions By combining field observations with controlled laboratory experiments, the student will develop a mechanistic understanding of uranium behaviour in organic-rich soils under environmental perturbations (e.g., saline intrusion, drought–flood events), thereby improving predictions of U mobility in a changing climate. The student will gain multidisciplinary expertise in environmental geochemistry and mineralogy, colloid science, and uranium biogeochemistry, and will receive training in laboratory and field methods as well as quantitative data analysis. The project will employ a suite of advanced analytical techniques, including X-ray absorption spectroscopy (XAS), luminescence spectroscopy, and electron microscopy. Reactive transport and geochemical modelling may also be used to support experimental and field observations and to predict uranium mobility at the field scale.