The Bagnoli-Napoli, Italy, cleanup case study: Initial site characterisation, former remediation and current cleanup plans for the brownfield site

The Bagnoli–Napoli brownfield is a highly complex contaminated site where historical industrial pollution overlaps with an active volcanic–hydrothermal system related to the Campi Flegrei caldera. This study integrates results from extensive environmental investigations (1996–2001) with a process-based geochemical evaluation of completed and proposed remediation strategies. Geochemical evidence indicates that soils, groundwater, and marine sediments are affected by the superposition of anthropogenic contaminants and naturally derived potentially toxic elements mobilised by ascending hydrothermal fluids, making source discrimination, background definition, and risk assessment particularly challenging. Remediation actions completed by 2009 achieved contaminant concentrations compatible only with commercial/industrial land-use standards. Recent remediation plans rely heavily on large-scale excavation, dredging, and thermal desorption treatments of soils and sediments contaminated by PAHs and PCBs. Our analysis shows that such ex–situ–oriented approaches may significantly increase environmental and health risks in this specific geological context. Thermal desorption, when applied to materials enriched in organic pollutants under saline and hydrothermally influenced conditions, may favour the formation of secondary toxic compounds, including dioxins and organometallic Hg and Sn species. We therefore propose remediation solutions that preferentially adopt in-situ strategies, aimed at minimising soil and sediment disturbance, reducing contaminant mobility, and interrupting exposure pathways rather than removing large volumes of material. Controlled in-situ containment, isolation, and stabilisation techniques, integrated with site-specific geochemical background characterisation, are shown to be more compatible with the area's persistent geothermal fluxes. We conclude that effective remediation at Bagnoli requires in-situ, process-driven solutions tailored to the volcanic–hydrothermal setting, rather than aggressive ex-situ technologies or generic remediation schemes.