A GIS-based map of the Hg-impacted area in the Paglia River basin (Monte Amiata Mining District – Italy): An operational instrument for environmental management

In this study, we describe the elaboration of a GIS-based map of the Hg-impacted area of the upper part of the Paglia River basin. The map developed from a systematic collection of all existing geological and geochemical data, together with land cover and geomorphology data, integrated into a GIS-based geo-database. The Hgimpacted area was identified along the upper part of the Paglia River basin and was defined as a band within which there is at least one demonstrated occurrence of river/stream sediments and soils with concentrations of Hg ≥1 mg/kg. The Hg-impacted area covers about 20 km2 and the width roughly coincides with the Paglia River floodplain developed in the last 130 years. The identification of a Hg-impacted area will be a useful tool for the local communities in the Paglia River basin and for environmental national agencies when planning works involving the remobilization of river/stream sediments and soils to prevent the dispersal of contaminants. Considering that the extent of the Hg-contaminated area does not allow any remediation, the map can be used for site-specific risk assessment to ensure that anthropogenic activities occur at a minimum risk, considering the opportunity of revising local legislations regarding the permissible Hg-concentration in river/stream sediments in the area.