Po sequential extraction applied to wetland soils at uranium mining sites.

Former uranium mining activities have led to the presence of naturally occurring nuclides embedded in soil. Such activities have also modified the secular equilibrium between radionuclides in U decay series. The objective of this paper is to quantify the long-term effect of former uranium mining activities on the behavior of the final radionuclide in the U-series, i.e. polonium-210 (Po), present in soils. Soil samples are extracted from two uranium sites in France, specifically a quarried site and a natural site. The polonium distribution is studied within the various soil fractions, namely: water soluble, exchangeable, bound to carbonates, bound to iron/manganese oxides, bound to organic matter, and residual. Po is mainly found in the residual fraction of both study sites (87-90%), followed by the carbonates fraction (5-9%). The Po activity in the other fractions is very small in comparison with total activity.