Rare earth elements in box-core sediments offshore of an industrial area, Ionian Sea, SE Sicily

The distribution of rare earth elements and yttrium (REEs + Y) has been investigated in box-core sediments recovered from four stations in the Sicilian coastal zone seawards of Augusta, one of the most industrialized and contaminated areas in the Mediterranean region. Shale-like REE patterns and low Y/ Ho ratios (close to the chondritic ratio) suggest a dominant terrigenous (geogenic) source for REE. Slight enrichment of LREE over the HREE is interpreted as due to preferential adsorptive transfer of LREE from seawater to sediment particles. Samples from offshore cores exhibit slightly positive Gd and negative Ce anomalies. It is here hypothesized that main drivers of anthropogenic Gd flux towards the offshore are dredged contaminated materials that, recovered from the Augusta Bay, have been repeatedly discharged offshore. Consistent with the redox-chemistry of Ce, these anomalous sedimentary inputs induce a decrease of O2 concentration in the sediment, which in turn triggers Ce regeneration.