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Ludovico Sicardi was a chemist and a pharmacist, and a passionate researcher, enthusiastic about phenomena related to volcanic activity. Due to a field survey within a project of mining research committed by a private company, he has the opportunity to visit the island of Vulcano (Eolie - Sicily), from December 1921 to June 1922. He was completely fascinated by the wild island of Vulcano and its gas manifestations. During several successive field trips in Vulcano, he observed and described the fumarolic field on a systematic basis, measuring the temperatures and recording their variations over time. He was one of the first to perform chemical analysis of fluids emitted by fumaroles in Vulcano Island and Solfatara di Pozzuoli (Italy). Furthermore, he was the first to suppose the coexistence of SO2 and H2S in fumarolic fluids, which by that time was considered to be impossible. Also, he succeeded in measuring their ratio by developing an in situ method that chemically separate the gaseous S-species. As the pioneer of applied geochemistry in volcanic fluids, he developed a method based on the sampling of fumarolic fluids using a glass flask that contained a NH4OH-AgNO3 solution to absorb the soluble acid gases (CO2, SO2 and HCl) and precipitate H2S as an insoluble Ag2S. A series of fortuitous coincidences allowed us to tell this story. Thanks to Prof. Marcello Carapezza and Prof. Mariano Valenza of the University of Palermo, the “scientific treasure” of Sicardi was preserved and it is nowadays studied and cataloged. It consists of Sicardi’s sampling-equipment, copies of the scientific articles, several historical maps and photos of Vulcano and Solfatara, manuscript notes and three important unpublished researches about Vulcano, Vesuvio and Campi Flegrei. Based on the remarkable scientific production, Sicardi has to be considered a precursor of modern volcanic monitoring based on fluid geochemistry.

Mt. Etna, on the eastern coast of Sicily (Italy), is one of the most active volcanoes on the planet and it is widely recognized as a big source of volcanic gases (e.g., CO2 and SO2), halogens, and a lot of trace elements, to the atmosphere in the Mediterranean region. Especially during eruptive periods, Etna’s emissions can be dispersed over long distances and cover wide areas. A group of trace elements has been recently brought to attention for their possible environmental and human health impacts, the Technology-critical elements. The current knowledge about their geochemical cycles is still scarce, nevertheless, recent studies (Brugnone et al., 2020) evidenced a contribution from the volcanic activity for some of them (Te, Tl, and REE). In 2021, in the framework of the research project “Pianeta Dinamico”, by INGV, a network of 10 bulk collectors was implemented to collect, monthly, atmospheric deposition samples. Four of these collectors are located on the flanks of Mt. Etna, other two are in the urban area of Catania and three are in the industrial area of Priolo, all most of the time downwind of the main craters. The last one, close to Cesarò (Nebrodi Regional Park), represents the regional background. The research aims to produce a database on major ions and trace element compositions of the bulk deposition and here we report the values of the main physical-chemical parameters and the deposition fluxes of major ions and trace elements from the first year of research. The pH ranged from 3.1 to 7.7, with a mean value of 5.6, in samples from the Etna area, while it ranged between 5.2 and 7.6, with a mean value of 6.4, in samples from the other study areas. The EC showed values ranging from 5 to 1032 μS cm-1, with a mean value of 65 μS cm-1. The most abundant ions were Cl- and SO42- for anions, Na+ and Ca+ for cations, whose mean deposition fluxes, considering all sampling sites, were 16.6, 6.8, 8.4, and 6.0 mg m-2 d, respectively. The highest deposition fluxes of volcanic refractory elements, such as Al, Fe, and Ti, were measured in the Etna’s sites, with mean values of 948, 464, and 34.3 μg m-2 d-1, respectively, higher than those detected in the other sampling sites, further away from the volcanic source (26.2, 12.4, 0.5 μg m-2 d-1, respectively). The same trend was also observed for volatile elements of prevailing volcanic origin, such as Tl (0.49 μg m-2 d-1), Te (0.07 μg m-2 d-1), As (0.95 μg m-2 d-1), Se (1.92 μg m-2 d-1), and Cd (0.39 μg m-2 d-1). Our preliminary results show that, close to a volcanic area, volcanic emissions must be considered among the major contributors of ions and trace elements to the atmosphere. Their deposition may significantly impact the pedosphere, hydrosphere, and biosphere and directly or indirectly human health.

Mt. Etna, on the eastern coast of Sicily (Italy), is one of the most active and most intensely monitored volcanoes on the Earth, widely recognized as a big source of volcanic gases, such as CO2, SO2, halogens, and many trace elements, including technological critical elements (TCEs), to the atmosphere on a regional and global scale. Mt. Etna emissions account for a significant percentage of the worldwide average volcanic budget and especially during eruptive periods, its products can be dispersed over great distances and they influence the chemical composition of the atmosphere of other continents too. The current knowledge about the geochemical cycle of TCEs is still scarce, nevertheless, recent studies [Brugnone et al., 2020], evidenced a contribution from the volcanic activity for some of them (Te, Tl, and REE). Here we report the arithmetic mean of the volume-weighted mean concentration values of each sampling site of both volcanic gas-derived anions SO42-, Cl-, and F-, and of some TCEs (i.e. Te and Tl). These were determined on bulk deposition samples collected, on monthly basis, during three different research projects: (1) SEW, from July 2017 to July 2018; (2) CISAS, from June 2018 to June 2019; (3) HEAVEN, which started in March 2021 and still ongoing. All the samples were analysed for major ion contents and many trace elements by IC, ICP-OES, and ICP-MS. During the first project, samples were acquired with 3 bulk collectors, located on the eastern slope of Etna, i.e., the slope toward which the volcanic emissions are usually dispersed by the prevalent regional winds. During this period, Etna showed ordinary outgassing activity and occasional ash emissions. Volume-weighted-mean (VWM) concentrations of 3.37, 6.87, and 0.48 mg L-1 were measured for SO42-, Cl-, and F- respectively (maxima up to 12.74, 44.80, and 2.55 mg L-1, respectively). High concentrations of Te and Tl were measured especially at the sampling sites closest to the central craters (VWM 0.012 µg L-1 and maximum 0.129 µg L-1 for Te; VWM 0.122 µg L-1 and maximum 0.978 µg L-1 for Tl). During the CISAS project, atmospheric bulk depositions were collected through a network of 11 bulk collectors, which were installed in the area of Siracusa, a town on the east coast of Sicily, about 80 km SSE of Mt. Etna, and in Milazzo, a town on the northern coast of Sicily, about 55 km NNE of Mt. Etna. Between 24-30 December 2018, a major eruption of Etna occurred, characterized by lava fountains and ash emissions. The samples collected in the study area of Siracusa during the period straddling the eruptive event were characterized by high concentrations of SO42- (up to 6.68 mg L-1), Cl- (up to 19.00 mg L-1), and F- (up to 0.88 mg L-1). In the same samples, the maximum concentrations were 0.025 µg L-1 and 0.164 µg L-1 for Te and Tl, respectively, showing values one order of magnitude higher than the median concentrations measured in the samples of the other monitoring campaigns carried out in the same study area. The study area of Milazzo, due to the prevailing winds from the North direction during the period of the eruption, has not been affected by the volcanic plume, and therefore the signature of the eruption was not visible in the samples collected in that area. From March 2021 atmospheric bulk deposition samples were collected through a network of 10 bulk collectors, which were installed on Mt. Etna, at various distances from the summit craters and on different slopes of the volcano, near the city of Catania, in the Siracusa area and near the village of Cesarò, in the Nebrodi Natural Regional Park. Mt Etna experienced two long sequences of 53 short-living lava fountain episodes between December 2020 and March 2021 and April to October 2021. Other episodes occurred more recently, between February and May 2022. Volcanic emissions associated with these paroxysmal events have been dispersed over great distances, even reaching other continents (e.g., Asia), and have been important contributors to the chemical composition of atmospheric deposition at all monitoring sites during the first year of the research. VWM concentrations of 3.26 mg L-1 (maximum 189.60 mg L-1), 5.78 mg L-1 (maximum 244.60 mg L-1), and 0.43 mg L-1 (maximum 40.66 mg L-1) were recorded for SO42-, Cl-, and F-, respectively. High concentrations of Te and Tl were also recorded, especially at sites closer to the central craters of Mt. Etna, with VWM concentrations of 0.018 µg L-1 and 0.121 µg L-1 and values up to 0.369 µg L-1 and 2.101 µg L-1, respectively. Based on our finding, we highlight that volcanic emissions must be considered among the major contributors to the chemistry of the atmospheric bulk deposition in sites close to active volcano emissions, but also at considerable distances from the vents during high-magnitude eruption events.

The source of chemical elements dissolved in rainwater can be both natural and anthropogenic. A group of trace elements has been recently brought to attention for their possible environmental impacts, the Technology-critical elements (TCEs). The current knowledge about the geochemical cycle of TCEs is still scarce, nevertheless recent studies [e.g. Brugnone et al., 2020] evidenced a contribution from the volcanic activity for some of them (Te, Tl, and REE). Our research aims to produce a geochemical database on major and trace element depositions in different areas of Sicily: a volcanic area (Etna), two urban areas (Palermo, Catania), two industrial areas (Milazzo, Priolo), and a rural monitoring site (Cesarò). The samples are collected monthly through a network of 15 bulk collectors. Here we report about the chemical composition of rainwater from the first five sampling campaigns. The pH was between 5.5 and 7.8, with an average value of 7.0. EC showed values ranging from 8 to 184 μS/cm, with an average of 72 μS/cm. The most abundant major elements were Cl- and SO42- for anions, Ca+ and Na+ for cations. Regarding trace elements, the highest volume-weighted mean (VWM) concentrations were generally measured in the areas affected by volcanic emissions, especially for TCEs, such as Te and Tl, which show VWM concentrations of 4.5 ng/L and 50.8 ng/L, respectively, higher than the VWM values detected in samples far from the volcanic source (0.8 ng/L and 2.5 ng/L, respectively). Exceptions are Zn and Br with the highest VWM concentration found in the Priolo area, Cr and Fe in Palermo. The contribution of the various sources, including the volcanic one, can therefore be well evidenced through the characterization of the chemical composition of the atmospheric deposition.

The Earth C-cycle is complex, where endogenic and exogenic sources are interconnected, operating in a multiple spatial and temporal scale (Lee et al., 2019). Non-volcanic CO2 degassing from active tectonic structures is one of the less defined components of this cycle (Frondini et al., 2019). Carbon mass-balance (Chiodini et al., 2000) is a useful tool to quantify the geogenic carbon output from regional karst hydrosystems. This approach has been demonstrated for central Italy and may be valid also for Greece, due to the similar geodynamic settings. Deep degassing in Greece has been ascertained mainly at hydrothermal and volcanic areas, but the impact of geogenic CO2 released by active tectonic areas has not yet been quantified. The main aim of this research is to investigate the possible deep degassing through the big karst aquifers of Greece. Since 2016, 156 karst springs were sampled along most of the Greek territory. To discriminate the sources of carbon, the analysis of the isotopic composition of carbon was carried out. δ13CTDIC values vary from -16.61 to -0.91‰ and can be subdivided into two groups characterized by (a) low δ13CTDIC, and (b) intermediate to high δ13CTDIC with a threshold value of -6.55‰. The composition of the first group can be related to the mixing of organic-derived CO2 and the dissolution of marine carbonates. Springs of the second group, mostly located close to Quaternary volcanic areas, are linked to possible carbon input from deep sources.

Sin dagli anni ’70, la ricerca scientifica ha evidenziato una forte relazione tra il degassamento di carbonio profondo e le aree tettonicamente attive, sottolineando l’elevata importanza del contributo di queste emissioni nella quantificazione del carbonio globale. La Penisola Balcanica presenta grandi aree caratterizzate da degassamento di carbonio di origine mantellica, da attività vulcaniche Quaternarie, da un’elevata sismicità e da strutture tettoniche a scala regionale. Purtroppo, la stima del degassamento di anidride carbonica profonda in quest’area è ancora poco studiata. La ricerca di questa tesi di dottorato si è focalizzata sulla (i) stima dell’output di carbonio profondo dalle grandi sorgenti carsiche della Grecia, e sulla (ii) caratterizzazione della composizione chimica e isotopica delle principali manifestazioni gassose della Macedonia del Nord. Inoltre, è stato condotto anche uno studio sull’impatto dei processi geogenici ed antropogenici sulla qualità delle acque dei grandi sistemi carsici della Grecia. Negli acquiferi carsici delle Grecia sono state riconosciute tre principali composizioni chimiche dell’acqua: (i) bicarbonato-calcica per le sorgenti continentali; (ii) cloruro-sodica per le sorgenti in area di costa, (iii) solfato-calcica dovuta a processi di dissoluzione di gesso all’interno dell’acquifero. I risultati, in termini di specie maggiori ed elementi in traccia, sono stati comparati con i limiti sulle acque potabili imposte dalle Direttive della Comunità Europea, CE/98/83 e CE/2020/2184, i quali raramente vengono superati tranne per quei parametri che risentono della influenza dell’intrusione marina (Conduttività Elettrica, Na, Cl, B). In queste sorgenti, sono stati rivelati elevati valori di nitrato, sebbene sempre al di sotto del limite di potabilità. Per quanto riguarda la composizione chimica dei gas disciolti e liberi, l’azoto risulta essere il gas dominante, con concentrazioni fino a 985,300 µmol mol-1. Il δ13CTDIC varia tra -16.6 ‰ e -0.10 ‰ (vs. V-PDB), mentre il δ13CCO2, misurato nel gas libero, varia da -29.9 ‰ a -7.41 ‰ (vs. V-PDB). La composizione isotopica dell’elio è stata misurata solo in pochi campioni (R/RA = 0.20 - 0.33), con valori che indicano una sorgente principalmente crostale. Applicando il bilancio di massa del carbonio, è stata fatta una stima del carbonio endogenico (1.43 × 109 mol a-1), la quale sorgente potrebbe essere associata a diverse sorgenti, tra cui termo-metamorfismo di carbonati indotto dall’intrusione di corpi magmatici di età Quaternaria e/o strutture tettoniche regionali. La ricerca condotta in Macedonia del Nord rappresenta un primo catalogo delle principali manifestazioni gassose presenti nell’area, sebbene ancora incompleto. Le manifestazioni gassose campionate, comprendenti sia sistemi caldi sia sistemi freddi, sono stati suddivisi in tre gruppi: (i) dominati in N2; (ii) dominati in CO2; (iii) ricchi in H2S. Queste categorie sono ben separate geograficamente, associate, soprattutto, al regime tettonico estensionale e, spesso, associati alle aree di confine tra le principali unità geotettoniche. Il δ13CCO2 varia tra -15.7 ‰ e +1.0 ‰, mentre i valori di R/RA variano da 0.1 a 1.8, suggerendo un’origine perlopiù crostale con un contributo mantellico fino al 20%. La composizione isotopica del metano presenta valori di δ13CCH4 tra -57.8 ‰ e -7.2 ‰ e valori di δ2HCH4 tra -303 ‰ e -80 ‰. Inoltre, misure di flusso di CO2 al suolo sono state condotte a Duvalo Kosel, Petkoniva e Botun. Per quanto riguardo Duvalo Kosel, un’area studiata in dettaglio, si è stimato una emissione di CO2 di 66.9 t × d-1. A Petkoniva and Botun sono state condotte delle misure preliminari, limitate ad aree caratterizzate da forte alterazione del suolo e mancanza di vegetazione, rivelando un flusso di CO2 di 0.20 t × d-1 a Petkoniva e di 0.59 t × d-1 a Botun. Since the 1970s, scientific research evidenced the close relationship between deeply-derived carbon degassing and active tectonic zones, highlighting the utmost importance of tectonic degassing contribution within the global carbon cycle. Large-scale degassing of mantle-derived carbon, Quaternary volcanic activity, seismic activity, and regional active fault systems are widespread in the Balkan Peninsula. However, the estimation of geogenic CO2 release from this area is currently still poorly quantified. This PhD research is focused on (i) the estimation of endogenous carbon release from the main karst hydro-systems of Greece and on (ii) the chemical and isotopic characterization of the main gas manifestation in North Macedonia. Moreover, a study about the geogenic and anthropogenic processes affecting the water quality of Hellenic karst aquifers was carried out. Three main water types were recognized in the Hellenic karst aquifers: (i) calcium-bicarbonate for hinterland springs; (ii) sodium-chloride for coastal springs; (iii) calcium-sulfate derived from gypsum dissolution. Results in terms of major ions and trace elements were compared with the drinking water limits set by the Directive 98/83/EC and the Directive 2020/2184/EC, which are rarely exceeded except for parameters related to marine intrusion along the coastal areas (EC, Na, Cl, B). In these springs, the highest nitrate levels are also found, though always below the drinking water limit. Regarding the chemical composition of the dissolved and free gases collected in the above-mentioned springs, the nitrogen is the dominant gas (up to 985,300 µmol mol-1). The δ13CTDIC varies between -16.6 ‰ and -0.10 ‰ (vs. V-PDB), whereas the δ13CCO2 in free gases ranged from -29.9 ‰ to -7.41 ‰ (vs. V-PDB). The isotopic composition of helium was measured in few samples (R/RA = 0.20 - 0.33), with values indicating a mainly crustal source. An estimation of the endogenous carbon (1.43 × 109 mol a-1) released from these systems was carried out, applying the isotope-carbon mass balance. The geogenic source of carbon may be associated to multiple sources, such as thermo-metamorphism of buried carbonates associated to intrusions of Quaternary magmatic bodies and/or regional tectonic structures. The research about the gas manifestations in North Macedonia represented a first catalogue, although still incomplete. The collected gas manifestations, comprising both thermal and cold systems, were subdivided in three groups: (i) N2-dominated group; (ii) CO2-dominated group; (iii) H2S-rich group. These categories are geographically well separated, mainly, related to the extensional tectonic regime of the area and, sometimes, associated with boundaries between the major geotectonic units. The δ13CCO2 varies between -15.7 ‰ and +1.0 ‰, whereas the R/RA values vary from 0.1 to 1.8, suggesting a prevailing crustal source with a mantle contribution up to 20%. On the other hand, the isotope composition of methane showed δ13CCH4 values ranging between -57.8 ‰ and -7.2 ‰ and δ2HCH4 varying from -303 ‰ to -80 ‰. Furthermore, soil CO2 flux measurements were carried out at Duvalo Kosel, Petkoniva and Botun. Regarding the former, a detailed investigation was carried out, estimanting a total CO2 output of 66.9 t × d-1. A preliminary investigation was done at Petkoniva and Botun, limited only to patches with heavy soil alteration and devoid of vegetation, revealing a CO2 output of 0.20 t × d-1 at Petkoniva and of 0.59 t × d-1 at Botun.