Characterizing the transport of natural uranium and its decay product ²²⁶Ra, downstream from former mines in France

Surface waters downstream from former uranium mines have been studied in order to characterize U and ²²⁶Ra transport and to assess their bioavailability. Filtrations and ultra-filtrations (UF) have been performed (0.45 μm / 0.2 μm / 500 kDa / 100 kDa / 10 kDa) and compared to the in situ technique, diffusive gradients in thin films (DGT). One of the study sites, a stream passing through a peat bog located in the vicinity of a former U mine, shows an increase in total U and a slight increase in ²²⁶Ra concentrations. While ²²⁶Ra is completely dissolved, U is mainly present as particles and colloids, the dissolved fraction reaching only about 5-20%. (authors)