New analytical methods for the assessment of natural (238U, 232Th, 226Ra, 40K) and anthropogenic (137Cs) radionuclides as actinides (239Pu, 240Pu): The case study of the Garigliano NPP releases along the Domitia sandy beaches (Southern Italy)

•Natural and anthropogenic radionuclides along the Domitia sandy beaches.•The natural (238U, 232Th, 226Ra, 40K) activities increase in the sand fraction.•The Cesium (137Cs) activity excludes any contribution of the nuclear plant.•The Plutonium ratios (240Pu/239Pu) exclude any contribution of the nuclear plant.•The applied methodology can be used as a reference for sand analyses. The work aims to investigate the distribution versus depth of natural (238U, 232Th, 226Ra, 40K) and anthropogenic radionuclides (137Cs, 239Pu, 240Pu) along the Domitia coastal zone (Campania Region, Southern Italy) downstream the Garigliano and Volturno rivers, to value the influence of the decommissioned Garigliano Nuclear Power Plant (GNPP) releases. Despite the coastal systems are in continuous evolution, they hold memory of the radioactive contamination to be monitored in order to disseminate new knowledge both about the geochemistry of the isotopes and on their possible interactions with the geologic-sedimentologic context. Given the limited scientific investigations during the years in this field, the present work attempted to fill the gap of knowledge, trying to investigate the presence of radionuclide pollution in the Campanian coastal littoral. A constant distribution of natural radioisotopes in the medium-fine sand fraction is found, with an increase in the coarse fraction, showing an interesting correlation between the radioactive content with the lithology and mineralogy. About the anthropogenic cesium, the low concentrations (due to its strong solubility in the water) allowed to exclude any contribution of the GNPP. Furthermore the 239,240Pu actinides results, detected for both the ivestigated areas and for the used techniques, falls completely in the reference range values: the isotopic ratio is in the global fallout range allowing to exclude any contribution from the GNPP. The extraction and purification method has allowed to obtain excellent results to detect 239,240Pu actinides both for the ICP-MS, at Risø National Laboratory, and for the AMS technique, at CIRCE laboratory. For these reason the method is so reliable and reproducible that it could be considered as a reference for future environmental radioactivity studies on the sandy matrix.