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The chemical composition of rainwater was studied in two highly-industrialised areas in Sicily (southern Italy), between June 2018 and July 2019. The study areas were characterised by large oil refining plants and other industrial hubs whose processes contribute to the release of large amounts of gaseous species that can affect the chemical composition of atmospheric deposition As in most of the Mediterranean area, rainwater acidity (ranging in the study area between 3.9 and 8.3) was buffered by the dissolution of abundant geogenic carbonate aerosol. In particular, calcium and magnesium cations showed the highest pH-neutralizing factor, with ~92% of the acidity brought by SO42− and NO3− neutralized by alkaline dust. The lowest pH values were observed in samples collected after abundant rain periods, characterised by a less significant dry deposition of alkaline materials. Electrical Conductivity (ranging between 7 µS cm−1 and 396 µS cm−1) was inversely correlated with the amount of rainfall measured in the two areas. Concentrations of major ionic species followed the sequence Cl− > Na+ > SO42− ≃ HCO3− > ≃ Ca2+ > NO3− > Mg2+ > K+ > F−. High loads of Na+ and Cl− (with a calculated R2 = 0.99) reflected proximity to the sea. Calcium, potassium, and non-sea-salt magnesium had a prevalent crustal origin. Non-sea salt sulphate, nitrate, and fluoride can be attributed mainly to anthropogenic sources. Mt. Etna, during eruptive periods, may be also considered, on a regional scale, a significant source for fluoride, non-sea salt sulphate, and even chloride.

Geothermal areas of Greece are located in regions affected by recent volcanism and in continental basins characterised by elevated heat flow. Many of them are found along the coast, and thus, water is often saline due to marine intrusion. In the current study, we present about 300 unpublished and literature data from thermal and cold mineral waters collected along Greece. Samples were analysed for major ions, Li, SiO2 and isotopes in water. Measured temperatures range from 6.5 to 98 °C, pH from 1.96 to 11.98, while Total Dissolved Solutes (TDS) from 0.22 to 51 g/L. Waters were subdivided into four main groups: (1) thermal; (2) cold; (3) acidic (pH 11). On statistical basis, thermal waters were subdivided into subgroups according to both their temperature [warm ( 75 °C)] and TDS [low salinity ( 30 g/L)]. Cold waters were subdivided based on their pCO2 [low ( 0.85 atm)]. δ18O–H2O ranges from − 12.7 to + 2.7‰ versus SMOW, while δ2H–H2O from − 91 to + 12‰ versus SMOW being generally comprised between the Global Meteoric Water Line and the East Mediterranean Meteoric Water Line. Positive δ18O shifts with respect to the former are mostly related to mixing with seawater, while only for a few samples these shifts point to high-temperature water–rock interaction processes. Only a few thermal waters gave reliable geothermometric estimates, suggesting reservoir temperatures between 80 and 260 °C.

Trace elements have a fundamental role in natural and anthropogenic systems. In waters, they present a great variability of concentrations that mostly depends on the degree of gaswaterrock interactions and geochemical conditions such as pH, temperature, redox and/or exchange reactions, etc. Even though, they are present in very low contents in hostrocks, elevated concentrations in ground or surface waters may have a hazardous impact on human and animal health and thus, it is important to both quantify and try to understand their behaviour in natural systems. Here we present the results of about 300 cold and thermal mineral waters collected along the entire Hellenic territory. Physicochemical parameters (temperature, pH, electrical conductivity and Eh) were measured in situ, whilst samples were analysed by Ionic Chromatography (IC) and Inductively Coupled Plasma Mass Spectrometry (ICPMS) for their major and trace elements’ content. The great variability in hydrogeological settings justifies the wide range of temperatures (6.5 98° C) and pH (1.96 11.98). Total Dissolved Solids (TDS) values also covered a wide range, from 0.06 to 43 g/L. Based on the combination of pH, T and TDS, samples were subdivided into 5 classes: i) thermal waters; ii) thermal waters affected by sea water contamination; iii) cold CO2rich waters; iv) hyperalkaline waters; and v) acidic waters. The great variability in chemical composition of the sampled waters is reflected in the large range of trace element contents (four to five orders of magnitude). Thermal waters affected by seawater contamination show the strongest enrichments in Li (up to 17,600 μg/L), B (up to 38,200 μg/L), Sr (up to 80,000 μg/L) and Rb (up to 9230 μg/L), mostly deriving from waterrock interaction. Cold CO2rich waters display elevated concentrations of Mn (up to 3970 μg/L), Ni (up to 111 μg/L) and Fe (up to 218,000 μg/L), whilst at the water outflow an extensive precipitation of iron oxihydroxides is observed. Hyperalkaline waters are generally strongly depleted in trace elements due to the precipitation of secondary minerals, however they are enriched in Al (up to 421 μg/L). Aluminium becomes soluble at extreme pH conditions and therefore also acidic waters present enhanced concentrations (up to 100,000 μg/L). Acidic waters show also enrichments in Fe (up to 58,400 μg/L), Mn (up to 15,600 μg/L) and Ni (up to 101 μg/L). In some cases, the maximum contaminant levels (MCLs) fixed by the Directive 98/83/EC for drinking water (and subsequent updates), are strongly exceeded in the under investigation waters. Such elevated concentrations of harmful elements may create hazards to human health either via direct consumption of cold mineral waters or through mixing of highly mineralized waters even in small proportions with shallow groundwater. For instance, As (MCL 10 μg/L) in the sampled waters reaches concentrations up to 1820 μg/L that derive from high temperature waterrock interaction within the hydrothermal circuit.

I was lucky enough to meet Mariano Valenza in September 1995. I was hitchhiking on the highway that leads from Cefalu to Palermo to go back home. I had spent my summer holidays in the beautiful and wild Madonie mountains. An off-road vehicle (a Land Rover Defender) stopped and a refined gentleman with a curious and charismatic gaze offered me a ride. During our journey, we chatted pleasantly and he told he was originally from that area. When I told him, I was a Geology student, he smiled at me and said Then we will meet again soon, I am going to be your Teacher of Geochemistry!. After a few weeks the lessons began and I met again Professor Valenza in Via Archirafi 36, at the University of Palermo. I will never forget the first introductive lesson of his course: ... we are going to study how the chemical elements have formed in the stars, and how these elements have spread out on our planet; we are going to study the chemical- physical laws regulating their geochemical cycles and how they move in between the atmosphere, the hydrosphere and the lithosphere. We will also learn how the isotopes of these elements allow us to date the geological phenomena and the age of our own planet Earth; ...let's imagine that we are ourselves made of billions and billions and billions of atoms, and it is statically possible that one of Napoleon atom could be here, in this class room!. I was truly fascinated and I discovered my passion for this interesting subject.In via Archirafi 36, in the historical building of the University of Palermo, once home of the Istituto di Mineralogia, I have graduated and got a Ph.D. in Geochemistry, and still nowadays I am working there. In these last 25 years I have learnt to know the stories of different personalities and their scientific researches, which have been hidden and looked after in the ancient building of the University for almost one century. With this article, we would like to remember Professor Mariano Valenza, by telling some stories about him and some others told by himself. Amongst these extraordinary stories we have focused on the one of a little-known scientist, Ludovico Sicardi (1895 - 1987), a modest man who followed his passion for volcanoes. In his field, he was a true innovator and the present research in the field of the geochemical surveillance of volcanos is deeply in debt to him. The Scuola di Geochimica dei Fluidi, born in the '70s at the University of Palermo, has the most debt of gratitude to him, but also the one which has treasured best his memory. This special paper is dedicated to Professor Valenza, who was one of the founders of this school and, before that, the teacher of most of this piece's authors. He had preserved, beside the historical memory, also many documents, photos, and the scientific equipment used by Sicardi for his studies.Sergio Calabrese, Palermo, March 2020

The eruption of Mt. Etna which occurred on December 24th 2018 was characterized by strombolian activity and fire fountains, emitted by the New South-East Crater and along a fissure that propagated towards the SE. The influence of volcanic emissions on atmospheric deposition was clearly detectable at several kilometres from the source. Wet and dry (bulk) deposition samples were collected each month, through a network of eleven collectors, in the areas of Milazzo, and Priolo between June 2018 and June 2019. They were analysed for major ions and trace elements concentrations. The pH values range from 3.9 to 8.3, while the EC values range from 7 to 396 μS cm-1. An extensive neutralization of the acidity has been recognised mainly due to the suspended alkaline dust particles, which have a buffering role in rainwater. A high load of Na+ and Cl- was observed at all sites, related to the closeness of the study areas to the coast, showing a high positive correlation (R2 = 0.989) along the line of Na+/Cl- ratio in seawater. During the eruption, the volcanic plume was carried by the winds for long distance (more than 300 km) affecting the area of Priolo but not that of Milazzo, which was upwind with respect to Mt. Etna. The impact of volcanic HF was clearly recognised in the samples collected after the eruption. Volcanic SO2 and HCl had a lower impact due to the overwhelming input of anthropogenic sulfate and marine chloride. On the contrary, the signature of the Mt. Etna eruption can be well recognised in the high concentrations of certain trace elements in the samples collected immediately after the eruption. The strongest contrast between affected and non-affected samples was recognised in Al, Cd, and especially in the volatile elements Tl and Te, which are typically enriched in volcanic emissions. The results showed that volcanic eruptions might have a relevant effect on the atmospheric chemistry and on the composition of rainwater up to distances of 80 km from the emission vents.