This dataset contains the results of a laboratory study investigating the dissolution of UO3•nH2O particles in dynamic sediment/groundwater column systems, representative of the shallow subsurface at the Sellafield Ltd. site, UK. Measurements were carried out to determine the extent of uranic particle dissolution and the speciation of dissolved uranium within the columns under contrasting biogeochemical conditions (oxic and electron-donor amended). Columns effluents were analysed periodically for key biogeochemical indicators (nitrate, sulfate) and trace metals (iron, manganese, uranium) and systems were sacrificed after 6 and 12 months of groundwater flow. Upon sacrifice, columns were cross-sectioned, and the sediment structure preserved for synchrotron micro-focus X-ray Fluorescence (XRF) mapping, and uranium L-edge X-ray Absorption Spectroscopy (XAS) measurements. Sub-samples of column sediments were also analysed for acid extractable metals, microbial abundance and classification and bioavailable Fe(II) concentrations. Experiments were performed between March 2016 and March 2017. Subsequent analyses were performed between March 2017 and December 2018. This data was collected as part of the project: Understanding radioactive ‘hot’ particle evolution in the environment funded by the UK Natural Environment Research Council (grant NE/M014088/1). Full details about this nonGeographicDataset can be found at https://doi.org/10.5285/2702e1b0-13df-4ae4-9f91-4ac4bd07bbf1