Abstract Purpose The extensive Hg contamination in soil and sediments occurring along the Paglia River (Central Italy) is the result of the interplay between the geomorphological changes of the river and anthropic activities, primarily associated to the exploitation of Hg-deposits in "The Monte Amiata mining district" (MAMD). The present study determines the implications of the morphological changes that occurred along the Paglia River in the last 200 years on the distribution of Hg along the floodplain and riverbed, which today represent one of the main Hg-reservoirs in the MAMD. Materials and methods The temporal changes of the Paglia riverbed and the extent of its alluvial deposits were reconstructed by a GIS-based analysis of the available maps and aerial photos. The Hg-concentration in soil and sediment samples, collected along five transects transverse to the Paglia River channel, was determined by ICP-MS. Results and discussion Samples along the investigated Paglia River segment typically show Hg-contents exceeding the Italian threshold for residential and public green soil use (1 mg kg −1 ). The distribution of Hg in the Paglia floodplain results from the combination of exceedance of sediment yield to the river during mining activities, that fed the floodplain with large amounts of Hg-contaminated sediments during its braided stage about 100 years ago, and the morphological changes of the river, that led to the evolution from a braided to the present-day single channel river. The magnitude of the extension of Hg-contamination, the river geomorphologic changes, and the processes of transport, deposition, and re-suspension did not allow a natural “clean up” of the river system, which shows a low resilience. Under high flow conditions, and especially in coincidence with intense rain events, large amounts of Hg stored in the overbank sediments are mobilized and redistributed, contributing to make the floodplain a secondary Hg-source. Extreme weather events, expected to intensify as a consequence of climate change, will contribute to the recurrent distribution of Hg-contaminated legacy sediments in the floodplain and along the Paglia river course. Conclusion From a water/land management perspective, the variability of the river flow, associated with an increase of extreme flood events driven by climate change, will affect the distribution of Hg-contaminated particles in the Paglia River, contributing to the Hg input into the Mediterranean Sea in the future. Graphical abstract 

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The extensive mercury contamination in soil and legacy sediments of the Paglia River basin (Tuscany, Italy): interplay between Hg-mining waste discharge along rivers, 1960s economic boom, and ongoing climate change

In the framework of the Italian Special Network for Mercury (ISNM) "Reti Speciali", a sampling campaign to monitor atmospheric mercury (Hg) was carried out at Monte Sant'Angelo (MSA). This is a coastal monitoring station in the Apulia region, representative of the Southern Adriatic area, within the Mediterranean basin. This work presents continuous Gaseous Elemental Mercury (GEM) measurements over about three years at MSA, using the Lumex RA-915AM mercury analyzer. The aim was to obtain a dataset suitable for the analysis of Hg concentrations in terms of source and transport variation. Diurnal cycles of GEM were evaluated to observe the influence of local atmospheric temperature and wind speed on potential re-emissions from surrounding sea and soil surfaces. Data were also analyzed in terms of long-range transport, using backward trajectory cluster analysis. The spatial distribution of potential sources, contributing to higher measured GEM values, was obtained employing Potential Source Contribution Function (PSCF) statistics. The influence of major Hg anthropogenic point sources, such as mining activities and coal-fuel power plants, both regionally and continentally, from mainland Europe, was observed. The role of the vegetation GEM uptake in modulating the seasonal GEM variability was also investigated. The potential of wildfire influence over the highest detected GEM levels was further examined using active fire data and the evaluation of the vegetation dryness index during the selected episodes. 

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First atmospheric mercury measurements at a coastal site in the Apulia region: seasonal variability and source analysis

The Italian approach to determining background values (BGVs) of metals and trace elements in marine sediments according to the national legislation transposing the water framework directive (WFD) has been illustrated. This study may be helpful for all countries that need to establish local BGVs for the correct assessment of contamination in areas with wide geological and geochemical variability and, particularly, for those that need assessing the good chemical status according to the WFD. The first step was clearly defining the BGV as a concentration value that allows for discriminating between natural and anthropogenic contributions and establishing the concept of the marine geochemical province (MGP). Successively, criteria for delimiting the MGPs were provided, similar to those adopted for the geochemical mapping of the territory. Finally, an integrated method based on the constitution of a dataset from unpolluted sediments obtained from pre-industrial levels was chosen for determining the BGV.

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Coastal Marine Geochemical Provinces and Background Values in Sediments: A Methodological Approach

The Mediterranean Sea is characterized by a marked mercury (Hg) geochemical anomaly, arising in part from large Hg deposits. Mercury mass loads discharged from the Monte Amiata mining district (Central Italy) to the Mediterranean Sea through the Paglia–Tiber River system were estimated. Data from two seasons showed that up to 40 kg year−1 of Hg are drained to Tiber River and finally to the Mediterranean Sea. The mercury mass loads varied in different seasons, from 3 mg day−1 in the upper section of Paglia River in November to 42 g day−1 before the confluence with Tiber River in June. Along Tiber River, up to 15 ng L−1 of the total Hg found at a site after Rome showed that Hg can be discharged to the sea. The Alviano reservoir along Tiber River acts as a temporary trap for Hg-rich particulate, while dam operations may promote Hg release (up to 223 g day−1). The combination of hydrologic factors controlling Hg transport, the torrential regime in the upper catchment of Paglia River, the waterway steepness, together with Hg-contaminated legacy sediments in the Paglia River floodplain, make the Paglia–Tiber River system a long-lasting intermittent source of Hg to Tiber River and the Mediterranean Sea.

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Total Mercury Mass Load from the Paglia–Tiber River System: The Contribution to Mediterranean Sea Hg Budget

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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

Mercury distribution around the Siele Hg mine (Mt. Amiata district, Italy) twenty years after reclamation: Spatial and temporal variability in soil, stream sediments, and air

Rossella Friani

Papers

Mercury distribution around the Siele Hg mine (Mt. Amiata district, Italy) twenty years after reclamation: Spatial and temporal variability in soil, stream sediments, and air