Estuaries are sinks of materials and substances which are released directly into them or transported from rivers that drain the basin. It is usual to find high organic matter loads and fine particles in the sediments. We analyzed
radionuclide concentrations ((210)Po, (230)Th, (232)Th, (234)U, (238)U, (226)Ra, (228)Th, (228)Ra, (40)K) in sediments and three different organs (roots, stems and leaves) of three species of halophytes plants (Spartina maritima, Spartina densiflora and Sarcocornia perennis). The study was carried out in two tidal
salt marshes, one polluted by U-series
radionuclides and another nearby that was unpolluted and was used as a control (or reference) area. The Tinto River
salt marsh shows high levels of U-series
radionuclides coming from mining and industrial discharges. On the contrary, the unperturbed
Piedras River
salt marsh is located about 25 km from the Tinto marsh, and shows little presence of contaminants and
radionuclides. The results of this work have shown that natural
radionuclide concentrations (specially the U-
isotopes) in the Tinto
salt marsh sediments are one order of magnitude higher than those in the
Piedras marsh. These
radionuclide enhancements are reflected in the different organs of the plants, which have similar concentration increases as the sediments where they have grown. Finally, the
transfer factor (TF) of the most polluted
radionuclides (U-
isotopes and (210)Po) in the Tinto area are one order of magnitude higher than in the
Piedras area, indicating that the fraction of each
radionuclide in the sediment originating from the pollution is more available for the plants than the indigenous fraction. This means that the plants of the
salt marshes are unhelpful as
bioindicators or for the phytoremediation of
radionuclides.