Environmental impact of past Hg mining activities in the Monte Amiata district, Italy: A summary of recent studies

The environmental impact of mining and smelting in the world-class Monte Amiata mercury (Hg) ore field has long been studied, before and after the final closure in 1982. A first summary was presented in 2015. With this contribution, we review the studies conducted in the last eight years. The most significant results include ⅰ) Hg-isotope characterization of primary ore (cinnabar), smelting waste (calcines), soil, fish and stream sediments; ⅱ) analysis of the interplay between geomorphological evolution, fluvial dynamics and Hg distribution in the Paglia River catchment, which drains the main mining areas; ⅲ) an improved quantification of the Hg loads discharged to the Mediterranean Sea; ⅳ) the use of biomonitors to reveal the dispersion of Hg; ⅴ) new detailed surveys, including innovative techniques, of Hg distribution in air; ⅵ) specific investigations to support the ongoing reclamation at Abbadia San Salvatore, the main mining and smelting center of the district, and ⅶ) the assessment of the variability of Hg distribution in air, water and soil from the reclaimed Siele mine. Despite these progresses, there are further steps to be conducted to achieve optimal management of the wide contamination evidenced in this district. It is now fully clear that the diffuse character of contamination results in unfeasible hypotheses for total remediation. Therefore, the goal is that of a sustainable coexistence between contamination and human activities. This goal may involve the following activities: a) implementation of GIS-based contamination maps as a direct operational instrument for local authorities to tune up specific limitations and regulations of human activities (e.g., fishing, instream quarrying and wildfire management); b) mitigation measures such as increasing the vegetal cover of river banks to limit erosion and runoff, and c) continuous monitoring of air, water and soil contamination, including transfer to the food chain.