Geochemical modelling of the Broubster natural analogue site Caithness, Scotland
Anomalous uranium, thorium and rare earth element (REE) concentrations are associated with peat-rich soils at Broubster, Northern Scotland. The elements have been transported to and retained within a peat bog approximately 100 metres downslope from their source. This report discusses the geochemistry of rock, soil and water samples collected from the Broubster site and the relationship of trace element distributions to actinide and lanthanide mineralisation. The results of a modelling study carried out to improve understanding of speciation and actinide migration mechanisms operating at Broubster are described. Reduction of U(VI) to U(IV) appears to play no part in uranium speciation at Broubster and levels are not constrained by solubility. Comparison with the results of a parallel experimental study suggests all the uranium to be in true aqueous solution. However, a substantial proportion of the thorium in the Broubster waters is found to be present in colloidal form. The migration of transition metals both laterally and vertically within the soil zone has been investigated. Separate transport mechanisms are postulated for uranium and thorium. The results of modelling are in very good agreement with experimental speciation data and the observed behaviour of uranium and thorium at the site.
Bibliographic Reference: EUR 12342 EN (1989) 54 pp., FS, ECU 6.25
Record Number: 199010047 / Last updated on: 1994-12-01
Original language: en
Available languages: en