Behaviour and mobility of U and Ra in sediments near an abandoned uranium mine, Cornwall, UK†

This study investigates the behaviour and mobility of uranium (U) and radium (226Ra) in sediments near the abandoned South Terras uranium mine in Cornwall, UK. The objective was to assess the geochemical dispersion of these radionuclides. Sediment samples collected from the vicinity were analysed for uranium and radium concentrations using alpha and gamma spectrometry, respectively. Sequential chemical extraction was applied to examine the speciation of the radionuclides and their association with stable elements. Results indicated enhanced radioactivity in two specific locations, leading to further investigation of these samples. The geochemical distribution revealed variations of the radionuclides within five operationally-defined fractions, with the carbonate and organic fractions showing significant uranium release. The distribution pattern of radium paralleled that of barium, highlighting similar chemical properties. Analysis through scanning electron microscopy (SEM) and electron microprobe analysis (EMPA) identified uranium-bearing phases associated with various elements. Importantly, the study underscores the potential human health risks associated with contamination from former uranium mining areas, reaffirming the necessity for detailed environmental assessments in these sites.