Contamination legacy of Etruscan and Roman smelting at Populonia, a key pre-industrial metalworking site in Italy

The city of Populonia in the Gulf of Baratti (Southern Tuscany, Italy) was a prominent Mediterranean metalworking hub starting from Etruscan times (from eighth century BCE [Before Common Era]), particularly for iron production. Evidence of this extensive metallurgical activity includes large deposits of slag and metallurgical debris along the gulf. To assess the environmental impact of these activities, a mineralogical and geochemical study was conducted on soils and sedimentary deposits exposed along the Gulf of Baratti’s sea cliff. These deposits span from the Late Pleistocene to recent soils and include detrital slags deposits. Findings reveal that pre-anthropogenic deposits and soils have natural anomalous concentrations of chromium (Cr), nickel (Ni), and arsenic (As), originating from ophiolite complexes (Cr and Ni) in the nearby Apennine chain and polymetallic sulfide ore deposits (As) of Campiglia Marittima area. Erosion and river transport have caused an enrichment of these elements in the gulf leading to concentrations up to ten times higher than the average Upper Continental Crust. Calculating an enrichment factor (EF) index with paleosoil as a baseline, showed that soils and deposits linked to metallurgical activity are enriched up to 300 times in elements such as iron (Fe), tin (Sn), tungsten (W), lead (Pb), and copper (Cu)—key elements in iron and copper production. This study highlights significant trace metal dispersion during and after the metallurgical period, offering insights into natural background values for metals in Southern Tuscany.