Wetlands are hotspots of CH₄ emissions to the atmosphere, mainly sustained by microbial decomposition of organic matter in anoxic sediments. Several knowledge gaps exist on how environmental drivers shape CH₄ emissions from these ecosystems, posing challenges in upscaling efforts to estimate global emissions from waterbodies. In this work, CH₄ and CO₂ diffusive fluxes, along with chemical and isotopic composition of dissolved ionic and gaseous species, were determined from two wetlands of Tuscany (Italy): (i) Porta Lake, a small wetland largely invaded by Phragmites australis reeds experiencing reed die-back syndrome, and (ii) Massaciuccoli Lake, a wide marsh area including open-water basins and channels affected by seawater intrusion and eutrophication. Both wetlands were recognized as net sources of CH₄ to the atmosphere. Our data show that the magnitude of CH₄ diffusive emission was controlled by CH₄ production and consumption rates, being mostly governed by (i) water temperature and availability of labile carbon substrates and (ii) water column depth, wind exposure and dissolved O₂ contents, respectively. This evidence suggests that the highest CH₄ diffusive fluxes were sustained by reed beds, providing a large availability of organic matter supporting acetoclastic methanogenesis, with relevant implications for global carbon budget and future climate models.

Total and leached Arsenic, Mercury and Antimony were determined in the topsoils developed on the mining waste dumping area of Le Lame (Mt. Amiata, central Italy) where the post-processing Hg-rich ore deposits from the mining area of Abbadia San Salvatore were stored. The concentrations of As, Hg and Sb were up to 610, 1910 and 1610 mg kg⁻¹, respectively, while those in the leachates (carried out with CO₂-saturated MilliQ water to simulate the meteoric water conditions) were up to 102, 7 and 661 μg·L⁻¹, respectively. Most aqueous solutions were characterized by Hg content <0.1 μg·L⁻¹. This is likely suggesting that the mine wastes (locally named “rosticci”) were possibly resulting from an efficient roasting process that favored either the removal or inertization of Hg operated by the Gould furnaces and located in the southern sector of Le Lame. The highest values of total and leachate mercury were indeed mostly found in the northern portion where the “rosticci”, derived by the less efficient and older Spirek-Cermak furnaces, was accumulated. The saturation index was positive for the great majority of leachate samples in Fe-oxy-hydroxides, e.g., ferrihydrite, hematite, magnetite, goethite, and Al-hydroxides (boehmite and gibbsite). On the other hand, As- and Hg-compounds were shown to be systematically undersaturated, whereas oversaturation in tripuhyte (FeSbO₄) and romeite (Ca₂Sb₂O₇) was evidenced. The Eh-pH diagrams for the three chalcophile elements were also constructed and computed and updated according to the recent literature data.

The Galleria Italia waters drain the complex tunnel system of the former Hg-mining area of Abbadia San Salvatore (Tuscany, central Italia) and feed the 2.5 km-long Fosso della Chiusa creek. The mining exploitation was active for more than one century and more than 100,000 tons of liquid mercury were produced by roasting processes of cinnabar (HgS). In this work, a discontinuous geochemical monitoring of the Galleria Italia circumneutral waters was carried out from February 2009 to October 2020, during which the main physicochemical parameters, main and minor dissolved species and trace elements (including Hg) were determined. In the observation period, significant variations in the water chemistry were recorded, particularly when flooding waves, due to intense precipitations, occurred, with the two main events being recorded in February 2009 and January 2010. The chemical composition of the Galleria Italia waters was Ca(Mg)-SO₄ and related to congruent dissolution of gypsum/anhydrite at which a contribution from carbonatic and silicatic minerals and partial solubilization of CO₂ and and H₂S oxidation is to be added. Regarding the trace elements, Al, Mn and Fe were up to 1500, 768 and 39520 μg L⁻¹, with these elements also showing high contents in the sediment precipitating by the Galleria Italia waters. In most cases, dissolved mercury was below the instrumental detection limit (1 μg L⁻¹. Considering a mean flow rate of 40 L s⁻¹ of the discharged water, the amount of dissolved mercury released from Galleria Italia was computed, although most mercury was occurring in the sediment (1.2 mg kg⁻¹). A more realistic computation of mercury released from Galleria Italia should involve a sampling network along the Fosso della Chiusa before entering the riverine system of the Tiber basin, into which dissolved and suspended mercury are to be determined along with that occurring in the sediments.

Dissolved and suspended toxic elements in water discharged from abandoned and active mining areas pose several critical issues, since they represent a threat to the environment. In this work, we investigated the water, suspended particulates, and stream sediments of a 2.1 km long creek (Fosso della Chiusa) that is fed by waters draining the galleries of the abandoned Hg mining area of Abbadia San Salvatore (Mt. Amiata, Tuscany, central Italy). The geochemical results show evidence that the studied matrices are characterized by relatively high concentrations of Hg and As, whereas those of Sb are generally close to or below the instrumental detection limit. Independent of the matrices, the concentration of As decreases from the emergence point to the confluence with the Pagliola creek. In contrast, Hg concentrations display more complex behavior, as water and sediment are mainly characterized by concentrations that significantly increase along the water course. According to the geoaccumulation index (I_geo), sediments belong to Class 6 (extremely contaminated) for Hg. The I_geo of As varies from Class 6, close to the emergence, to Class 2 (moderately contaminated), dropping to Class 0 (uncontaminated) at the confluence with the Pagliola creek. Finally, the total mass load of Hg and As entering the Pagliola creek was computed to be 1.3 and 0.5 kg/year, respectively, when a mean flow rate of 40 L/s was considered. The calculated loads are relatively low, but, when the Fosso della Chiusa drainage basin is taken into account, the specific load is comparable to, or even higher than, those of other mining areas.

Mercury is a toxic and noxious element and is the only metal that naturally occurs as gas. One of the most challenging topics (included in the United Nations Minimata convention) is to understand the adsorption–release processes of manmade materials (e.g., concrete, bricks, tiles, painting). Adsorption of Hg by construction and demolition waste materials has recently been studied, but investigations on how much Hg⁰ can be released from these products are rather poor. The abandoned mining site of Abbadia San Salvatore (Siena, central Italy) where, for about one century, cinnabar was roasted to produce liquid mercury, is known for the high concentrations of (i) Hg⁰ in edifices and structures and (ii) total and leachate Hg in synthetic materials. In the present paper, a new, simple and low-cost method to measure the amount of GEM (Gaseous Elemental Mercury) released from anthropic materials (concrete, wall rocks, and tiles) located in the Hg⁰-rich environments of the former mining site, is proposed. The efficiency of a specific paint that was supposed to act as blocking agent to Hg⁰ was also tested.

A severe boron pollution has been recognized in the shallow aquifer of Isola di Castelluccio (central-eastern Tuscany, Italy) since 2009. Previous investigations showed that the high boron concentrations (up to 57 mg L-1) were related to an anthropogenic source. It was likely due to current and/or past industrial and artisanal activities, which were using B-compounds during their productive cycles. However, a univocal source of boron has so far not been recognized. In this work, we present and discuss new geochemical and isotopic data related to an extensive campaign (June 2016) carried out in 33 domestic well and piezometer waters. In addition, the results from a three-weekly to monthly monitoring survey (from August 2014 to December 2019) on selected waters were used to recognize signals in response to dry and wet periods or related to the presence of the recently installed hydraulic barrier. To verify the efficiency of the hydraulic barrier a numerical model of the shallow aquifer was performed by using the MODFLOW computer program. This study has allowed to identify where the source of contamination is likely located. This implies that specific investigations can now be carried out to definitively remove the anthropogenic source of boron.