Mercury historical signature in the Central and Southern Adriatic Sea sediment cores

The Hg evolution and relation with sediment grain-size and depositional environment are studied in four sediment cores collected along areas of present active pelitic sedimentation located in the western part of the middle and south Adriatic Sea. The four cores exhibited different Hg concentrations, ranging from 0.120 ± 0.016 to 0.040 ± 0.010 mg/kg, with higher content in northern areas than in southern and deeper areas, and decreasing concentrations from the upper to the lower core sections. Hg content was always below the limit of 0.3 mg/kg set by the Italian sediment quality guidelines. The positive correlation found between Hg and silt marks the importance of the silty fraction for the Hg adsorption and distribution in the Western Adriatic and its continental origin. The Sediment Accumulation Rates obtained from the literature allowed a preliminary core dating. This dating suggests that the evolution of Hg content over time reflects both historical periods of industrial growth and war activities, as well as different input areas. Therefore, Hg could be considered as a proxy for Anthropocene in industrialized areas. In particular, Hg reflects discharges from ore exploitation of Idrija mines (Slovenia), industry of Ravenna Harbour, as well as bombings and movements during WWII. All these anthropogenic activities produced high Hg rich particulates that were deposited, reworked, transported, and accumulated by the hydrodynamics of the Adriatic Sea. This study suggests Hg contamination in Adriatic Sea sediments as a potential marker for defining the Anthropocene epoch in middle and southern Adriatic sediments, contributing to the ongoing debate on its definition.