Characterisation of waterborne asbestos fibres to assess the impact on groundwater quality and their role in the risk of secondary migration in the air: The Mount Reventino area in Southern Italy as pilot site

Waterborne asbestos in affected Naturally Occurring Asbestos (NOA) areas represents a potential route for human exposure via ingestion and secondary aerial pathways. For the first time, this study systematically assesses the occurrence, concentration, and fate of hydrodispersed asbestos fibres in the Mount Reventino area of Calabria (Southern Italy), by using an integrated mineralogical, geochemical, and hydrogeological approach. Twenty-one water samples (16 groundwater, 5 surface water) were collected near ophiolitic outcrops and abandoned quarries and analysed using several advanced techniques. Based on morphological and compositional criteria, tremolite was the most abundant asbestos mineral detected in the water samples, followed by chrysotile, actinolite and anthophyllite. Surface waters show higher asbestos concentrations (1.5E+05 f/L) and longer fibres compared to groundwater (2.3E+04 f/L), suggesting a selective retention within the aquifer. The annual fibrous flux is dominated by tremolite (3.1E+14 f/year) and chrysotile (2.4E+14 f/year), followed by actinolite (9.2E+13 f/year) and anthophyllite (1.0E+11 f/year). The total annual fibre flux was estimated at 6.5E+14 (f/ year), predominantly from high-discharge watercourses, demonstrating that environmental impact is better quantified by fibre load rather than concentration alone. Water chemistry showed that most samples belong to the Ca-HCO3 and Mg-HCO3 hydrogeochemical facies and also provided the first evidence of a link between fibre concentrations and Ni and Cr levels. These new findings suggest a key role for fibres in trace metal mobilization. This study highlights groundwater as a potential pathway for asbestos dispersion and emphasises the need for integrated monitoring and prevention strategies in NOA-affected regions worldwide.