PRELIMINARY RESULTS ON THE OCCURRENCE OF RARE EARTH ELEMENTS IN THE AQUATIC SYSTEM OF THE PIALASSA BAIONA, RAVENNA (ITALY) RÉSULTATS PRÉLIMINAIRES SUR LA PRÉSENCE DES ÉLÉMENTS DE TERRES RARES DANS LE SYSTÈME AQUATIQUE DE LA PIALASSA BAIONA, RAVENNE (ITALIE) RISULTATI PRELIMINARI SULLA PRESENZA DI TERRE RARE NEL SISTEMA DELLE ACQUE DELLA PIALASSA BAIONA, RAVENNA (ITALIA)

The Site of Community Importance of the Pineta S. Vitale, bordered by the Pialassa Baiona lagoon system, is submitted to increasing deterioration due to a subsiding phenomenon, groundwater salinization and contamination from the industrial sites of Ravenna. Within a multidisciplinary research project, evaluation of the background level of Rare Earth Elements (REE, not regulated at present, but potentially harmful to human health) and the characterization of processes which control their migration and retention were performed to contribute to the knowledge on the present environmental quality of the Ravenna area. Concentrations of total and dissolved elements were determined in 40 water samples comprising surface waters, soil waters, shallow and deep groundwater. Dissolved major and minor components generally showed increasing concentrations from West to East (i.e. towards the sea) and appeared mostly derived from a marine source. Marked correlations between dissolved ΣREE and Al and Fe concentrations in the filtered fraction <0.4 μm were observed, especially in the soil waters. Shale-normalized patterns of the dissolved REE in the soil waters showed an enrichment in the Middle REE (MREE); such patterns being attributed to preferential adsorption of the MREE onto colloidal particles (<0.4