Mercury contamination in Italy: developing strategies for risk assessment

Mercury (Hg) occurs naturally or as an anthropogenic contaminant in the environment, posing serious threats to ecosystems and human health due to its mobility, toxicity, and bioaccumulation potential. Mercury contamination in Italy is due both to past mining activities and to various industrial uses. Contamination from mining can be particularly extensive. In the case of the Mt.Amiata mining district, in southern Tuscany, remarkable amounts of Hg were released in the environment causing a widespread contamination of downstream ecosystems over at least 200 km along the Paglia-Tiber River system (Rimondi et al., 2015). For large areas of Friuli Venezia Giulia (NE, Italy), the high contamination recorded in soils and sediments is caused by the mining activity at Idrija (Western Slovenia). The relevance of mining activities for Hg contamination is confirmed also by the EU mapping of Hg in topsoils, identifying highest concentrations of Hg close to mining sites, including Mt. Amiata and Idrija (Ballabio et al., 2021). In Italy, there are also several areas affected by the presence of Hg mainly used in the industrial manufacture of Cl products (Hg-cells). In 2020, after the Italian ratification of the Minamata Convention and the first official EU request on the Mercury European Regulation (EU 2017/852) implementation for contaminated sites, ISPRA collected relevant information from regional inventories identifying more than 240 Hg contaminated sites (i.e. posing significant risks), about half of which have been remediated. The toxicity of Hg varies greatly with its chemical form and exposure pathway. In Italy, for evaluating human exposure, the amount of three different Hg forms is usually considered, accounting for different toxicity/mobility related to specific pathways: Methylmercury (organic form) for direct contact; Mercury Chloride (soluble form in water) for mobilization to water resources (groundwater) and Elemental Mercury (volatile form) for inhalation route. The latter represents, together with the organic form, the most critical for human exposure (Kim et al., 2016). Substrates enriched in Hg due to anthropogenic contamination can release notable amounts of gaseous elemental mercury (GEM) into the atmosphere even years after the phase out of the contamination source, thus representing a health concern for exposure via vapour inhalation and requiring accurate measures of the GEM emissions to achieve a comprehensive risk assessment. An innovative measurement approach represented by an accumulation chamber coupled with a real-time GEM analyser, which allows rapid assessment of areal emissions (Floreani et al., 2023), has been tested for GEM fluxes estimation at the soil-air interface in some residential and agricultural areas within the contaminated site of Portoscuso (SW Sardinia). Diffuse GEM emissions were calculated and used as input in a new modelling approach for the estimation of outdoor and indoor human exposure.