Accumulazione, speciazione e meccanismi di trasferimento di radionuclidi in alghe marine modello

The aim of the present study is to evaluate the uptake of Uranium and Europium in two species of brown algae (Laminaria digitata and Ascophyllum nodosum) under pseudo-natural conditions. In vivo bioaccumulation experiments were performed by exposing the brown algae to a daily dose of Uranium and Europium for ten days.The accumulation of heavy metals was quantified via ICP-OES (Inductively Coupled Plasma - Optical Emission) and via Gamma Spectrometry at trace levels. The biodistribution inside different compartments of algae was also analyzed. To evaluate the uptake mechanisms, the speciation inside algal cells was investigated by EXAFS (Extended X-ray Absorption Fine Structure) spectroscopy and SEM (Scanning Electron Microscopy). As a complementary study, the potential role of glutathione (GSH) in direct chelation of Europium for intracellular detoxification was examined. It Is widely reported that organic ligands are released by seaweeds in response to metal exposure; glutathione (GSH) is a key component in metal sequestration due to the binding capacity related to its thiol (-SH) group.The binding constant of the GSH/Eu3+ system was analysed through spectrophotometric titrations. An exchange reaction that uses the PAR (4-(2-pyridylazo) resorcinol) dye was needed; therefore, the mechanistic aspects of the PAR-Eu3+ system were also analysed