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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.

Quantification of gaseous emissions in geological systems is an important branch because it is a major source of greenhouse gas to the atmospheric budget. Of geological environments, there are two different categories: the first category includes emissions of the predominant carbon dioxide (CO2), while the second includes emissions of the predominant methane (CH4). The Hellenic territory has a very complex geodynamic setting deriving from a long and complicated geological history. It is strongly characterized by intense seismic activity and enhanced geothermal gradient. This activity, with the contribution of an active volcanic arc, favours the existence of many cold and thermal gas manifestations. Geogenic sources release huge amounts of gases, which, apart from having important influences on the global climate, could also have a strong impact on human health. Geochemical studies based on the isotopic composition of carbon and hydrogen, along with helium isotopic ratios have become a good indicator of the origin of the gas. The isotopic ratio 13C/12C of CO2 expressed in _ 13C (h, provides important information about the amount of CO2 released from the Earth’s crust or mantle. For methane, carbon and hydrogen isotopic compositions and C1/(C2+C3) hydrocarbon ratios can characterize the origin of methane: biogenic (thermogenic or microbial) or abiogenic. Helium isotopic ratios provide additional information about crustal or mantle origin of the gas. In the present work, a large set of chemical and isotopic data is presented aiming at the identification of areas with geogenic gas emissions and their characterization in terms of different gas composition and origin. The present catalogue should be the base for the estimation total nationwide geogenic CO2 and CH4 fluxes.

Since its last magmatic eruption in 1530 AD, La Soufrière andesitic volcano in Guadeloupe has displayed intense hydrothermal activity and six phreatic eruptive crises (the last of which, in 1976-1977, with 73000 evacuees). Here we report on the first direct quantification of gas plume emissions from La Soufrière summit vents, which gradually intensified during the past 20 years. Gas fluxes were determined in 2006 then 2012 [1] by measuring the horizontal and vertical distribution of volcanic gas concentrations in the air-diluted plume, the composition of the hot fumarolic fluid at exit (108°C), and scaling to the speed of plume transport (in situ measurements and FLIR imaging). We first demonstrate that all fumarolic vents of La Soufrière are fed by a common H2O-rich (97-98 mol %) fluid end-member, emitted almost unmodified at the most active South Crater while affected by secondary alterations (steam condensation, sulphur scrubbing) at other vents. Daily fluxes in 2012 (200 tons of H2O, 15 tons of CO2, ~4 tons of H2S and 1 ton of HCl) were augmented by a factor ~3 compared to 2006, in agreement with increasing activity. Summit fumarolic degassing contributes most of the bulk volatile and heat budget (8 MW) of the volcano. Isotopic evidences demonstrate that La Soufrière hydrothermal emissions are sustained by continuous heat and gas supply from an andesitic magma reservoir confined at 6-7 km depth. This magmatic supply mixes with abundant groundwater of tropical meteoric origin in the hydrothermal system. Based on petro-geochemical data for the erupted magma(s), we assess that the volcanic gas fluxes in 2012 can be accounted for by the release of free magmatic gas derived from about 1000 m3 per day of the basaltic melt replenishing the reservoir at depth. In terms of mass budget, the current degassing unrest is compatible with enhanced free gas release from that reservoir, without requiring any (actually undetected) magma intrusion. We recommend a regular survey of the fumarolic gas flux from La Soufrière in order to anticipate the evolution of the magma reservoir. [1] P. Allard et al., Chemical Geology 384, 76-93, 2014.

Volcanic and geothermal systems emit endogenous gases by widespread degassing from soils, including CH4, a greenhouse gas 25 times as potent as CO2. Recently, it has been demonstrated that volcanic/geothermal soils act as source, but also as biological filter for methane release to the atmosphere. For long time, volcanic/geothermal soils has been considered inhospitable for methanotrophic microorganisms, but new extremophile methanotrophs belonging to Verrucomicrobia were identified in three different areas (Pozzuoli, Italy; Hell’s Gate, New Zealand; Kamchatka, Russia), explaining anomalous behaviours in methane leakages of several geothermal/volcanic sites. Our aim was to increase the knowledge of the relationship between methane emissions from volcanic/geothermal areas and biological methane oxidation, by investigating a geothermal site of Pantelleria island (Italy). Pantelleria Island hosts a high enthalpy geothermal system characterized by high temperature, high CH4 and very low H2S fluxes. Such characteristics are reflected in potentially great supply of methane for methanotrophs and scarce presence of inhibitors of their activity (H2S and NH3) in the Pantelleria soils. Potential methanotrophic activity within these soils was already evidenced by the CH4/CO2 ratio of the flux measurements which was lower than that of the respective fumarolic manifestations indicating a loss of CH4 during the gas travel towards the earth’s surface. In this study laboratory incubation experiments using soils sampled at Favara Grande, the main hydrothermal area of Pantelleria, showed very high methane consumption rates (up to 9500 ng CH4 h1 g1). Furthermore, microbiological and culture-independent molecular analyses allowed to detect the presence of methanotrophs affiliated to Gamma- and Alpha-Proteobacteria and to the newly discovered acidothermophilic methanotrophs Verrucomicrobia. Culturable methanotrophic Alpha-proteobacteria of the genus Methylocystis were isolated by enrichment cultures. The isolates showed a wide range of tolerance to pH (3.5 – 8) and temperatures (18 – 45 C), and an average methane oxidation rate of 450 ppm/h. A larger diversity of proteobacterial and verrucomicrobial methanotrophs was detected by the amplification of the methane mono-oxygenase gene pmoA. This study demonstrates the coexistence of both the methanotrophic phyla Verrucomicrobia and Proteobacteria in the same geothermal site. The presence of proteobacterial methanotrophs was quite unexpected because they are generally considered not adapted to live in such harsh environments. Their presence at Favara Grande could be explained by not so low soil pH values (> 5) of this specific geothermal site and by the high methane availability. Such species could have found their niches in the shallowest part of the soils, were the temperatures are not so high, thriving on the abundant upraising methane. Understanding the ecology of methanotrophy in geothermal sites will increase our knowledge of their role in methane emissions to the atmosphere.

Explosive eruptions and volcanic passive degassing inject large quantities of gas and particles into the atmosphere that are ultimately deposited at the Earth’s surface through wet or dry deposition processes, affecting the atmosphere, the hydrosphere and the biosphere. Mount Etna (Italy) is one of the most prodigious and persistent sources of gases and particles to the troposphere. Volcanic emissions were studied at Etna volcano by using moss-bags technique. Mosses (Sphagnum species) were exposed around the volcano at different distances from the active vents to evaluate the impact of its emissions into the atmosphere and in the local surrounding. The results confirmed the huge amount of silicates, sulfates and halides compounds emitted into the atmosphere from Mount Etna. X-ray microanalysis showed that chemical composition of the particles is mostly defined by silicate (from pure silica to metal-rich silicate composition) and sulfate/halide compounds. The contents of major and trace elements in the Sphagnum moss-bags significantly increased after their exposure to volcanic emissions, confirming mosses as efficient accumulators. Metals uptake rate rapidly decreases with the distance from the volcanic emission vents. The elements that showed the greatest accumulation after exposition were S, Na, Fe, Al, Cu, V, As, Cd, Li, Se, Sc, Th, Bi and Tl. This study confirmed the marked environmental impact of volcanic emissions in the eastern sector of Etna, leading to an intense “geochemical anomaly” of volatile major and trace elements due to the fumigation by the volcanic plume, in agreement with passive biomonitoring studies reported by previous authors. Finally, moss-bags techniques provide a cheap and efficient method to investigate quantitatively in space and time the environmental impact of volcanogenic atmospheric deposition.

Bulk deposition has been collected at six sampling sites in area of Gela plain (Italy) in the period from February 2008 to May 2009. Samples collected each two weeks were analysed for the major ion and trace elements content. Preliminary results allow identifying three different sources that control the abundance of the elements in atmospheric deposition: (1) sea spray, (2)geogenic dust, and (3) anthropogenic pollution. Due to the closeness of the coast, clear evidence of sea spray input is detectable for most of the samples. The high excess of non sea-salt sulphate(50 - 90% of the total) is prevailingly ascribable to the abundant SO2 emissions of the refinery.The pH values of the collected samples range from 4.2 to 8.6, with 80% of them above pH 6.5,indicating an extensive neutralization. This is due to NH3 coming from widespread agricultural activities in the plain of Gela, and geogenic CaCO3 either from local or from regional (desert dust) sources. Elevated levels of trace metals (Zn, V, Sb, Ni, Cr, Ni and Cu) can be observed in the samples collected close to the industrial area. All these elements can be identified as “anthropogenic” and attributed to the human activities, mainly to the industrial emissions, but a contribution could also derive from the intensive vehicular traffic.

Volcanic emissions represent one of the most relevant natural sources of trace elements to the troposphere. Due to their potential toxicity they may have important environmental impacts from the local to the global scale and they can severely affect the atmospheric and terrestrial environment also at timescales ranging from a few to million years. Etna volcano is known as one of the largest global contributors of magmatic gases (CO2, SO2, and halogens) and particulate matter, including some toxic trace elements. The aim of this study was to characterize the chemical composition and the mineralogical features of the volcanogenic aerosol passively emitted from Mt. Etna. Nine samples were collected by using the filtration technique at different sites on summer 2010 and 2011. Chemical and mineralogical analyses allowed to discriminate two main constituents: the first is mainly referable to the silicate component in the volcanic plume, like lithic and juvenile fragments, crystals (e.g., plagioclases, pyroxenes, oxides) and shards of volcanic glass; the second one is linked to the soluble components like sulfosalts or halide minerals (sulfates, chlorides and fluorides). These investigations are especially important in the study area because the summit of Mt. Etna is yearly visited by nearly one hundred thousand tourists that are exposed to potentially harmful compounds.

Methane is a major contributor to the greenhouse effect, its atmospheric concentration being more than doubled since the XIX century. Every year 22 Tg of methane are released to the atmosphere from several natural and anthropogenic sources. Natural sources include geothermal/volcanic areas but the estimation of the total methane emission from these areas is currently not well defined since the balance between emission through degassing and microbial oxidation within the soils is not well known. Microbial oxidation in soils contributes globally for about 3-9% to the removal of methane from the atmosphere and recent studies evidenced methanotrophic activity also in soils of volcanic/geothermal areas despite their harsh environmental conditions (high temperatures, low pH and high concentrations of H2S and NH3). Methanotrophs are a diverse group of bacteria that are able to metabolize methane as their only source of carbon and energy and are found within the Alpha and Gamma classes of Proteobacteria and within the phylum Verrucomicrobia. Our purpose was to study the interaction between methanotrophic communities and the methane emitted from the geothermally most active site of Pantelleria island (Italy), Favara Grande, whose total methane emission has been previously estimated in about 2.5 t/a. Laboratory incubation experiments with soil samples from Favara Grande showed methane consumption values of up to 9500 ng g1 dry soil per hour while soils collected outside the geothermal area consume less than 6 ng g1 h1. The maximum consumption was measured in the shallowest part of the soil profile (1-3 cm) and high values (>100 ng g1 h1) were maintained up to a depht of 15 cm. Furthermore, the highest consumption was measured at 37 C, and a still recognizable consumption (>20 ng g1 h1) at 80 C, with positive correlation with the methane concentration in the incubation atmosphere. These results can be considered a clear evidence of the presence of methanotrophs that were investigated by culturing and culture-independent techniques. The diversity of proteobacterial methanotrophs was investigated by creating a clone library of the amplified methane mono-oxygenase encoding gene, pmoA. Clone sequencing indicates the presence of Gammaproteobacteria in the soils of Favara Grande. Enrichment cultures, on a mineral medium in a CH4-enriched atmosphere, led to the isolation of different strains that were identified as Methylocistis spp., which belong to the Alphaproteobacteria. The presence of Verrucomicrobia was detected by amplification of pmoA gene using newly designed primers. Soils from Favara Grande show therefore the largest spectrum of methanotrophic microorganisms until now detected in a geothermal environment. While the presence of Verrucomicrobia in geothermal soils was predictable due to their thermophilic and acidophilic character, the presence of both Alpha and Gamma proteobacteria was unexpected. Their presence is limited to the shallowest part of the soil were temperatures are lower and is probably favored by a soil pH that is not too low (pH 5) and their contribution to biological methane oxidation at Pantelleria is significant. Understanding the ecology of methanotrophy in geothermal sites will increase our knowledge of the role of soils in methane emissions in such environments.

Methane plays an important role in the Earth’s atmospheric chemistry and radiative balance being the most important greenhouse gas after carbon dioxide. It has recently been established that geogenic gases contribute significantly to the natural CH4 flux to the atmosphere (Etiope et al., 2008). Volcanic/geothermal areas contribute to this flux, being the site of widespread diffuse degassing of endogenous gases (Chiodini et al., 2005). In such an environment soils are a source rather than a sink for atmospheric CH4 (Cardellini et al., 2003; Castaldi and Tedesco, 2005; D’Alessandro et al., 2009; 2011; 2013). Due to the fact that methane soil flux measurements are laboratory intensive, very few data have been collected until now in these areas. Preliminary studies (Etiope et al., 2007) estimated a total CH4 emission from European geothermal and volcanic systems in the range 4-16 kt a-1. This estimate was obtained indirectly from CO2 or H2O output data and from CO2/CH4 or H2O/CH4 values measured in the main gaseous manifestations. Such methods, although acceptable to obtain order-of-magnitude estimates, completely disregard possible methanotrophic activity within the soil. At the global scale, microbial oxidation in soils contributes for about 3-9% to the total removal of methane from the atmosphere. But the importance of methanotrophic organisms is even larger because they oxidise the greatest part of the methane produced in the soil and in the subsoil before its emission to the atmosphere. Environmental conditions in the soils of volcanic/geothermal areas (i.e. low oxygen content, high temperature and proton activity, etc.) have been considered inadequate for methanotrophic microrganisms. But recently, it has been demonstrated that methanotrophic consumption in soils occurs also under such harsh conditions due to the presence of acidophilic and thermophilic Verrucomicrobia. These organisms were found in Italy at the Solfatara di Pozzuoli (Pol et al., 2007), in New Zealand at Hell’s Gate (Dunfield et al., 2007) and in Kamchatka, Russia (Islam et al., 2008). Both the Italian and the Hellenic territories are geodynamically very active with many active volcanic and geothermal areas. Here we report on methane flux measurements made at Pantelleria (Italy) and at Sousaki and Nisyros (Greece). The total methane output of these three systems is about 10, 19 and 1 t a-1, respectively (D’Alessandro et al., 2009; 2011; 2013). The total emissions obtained from methane flux measurements are up to one order of magnitude lower than those obtained through indirect estimations. Clues of methanotrophic activity within the soils of these areas can be found in the CH4/CO2 ratio of the flux measurements which is always lower than that of the respective fumarolic manifestations, indicating a loss of CH4 during the travel of the gases towards earth’s surface. Furthermore laboratory methane consumption experiments made on soils collected at Pantelleria and Sousaki revealed, for most samples, CH4 consumption rates up to 9.50 μg h-1 and 0.52 μg h-1 respectively for each gram of soil (dry weight). Only few soil samples displayed no methane 2 consumption activity. Finally, microbiological and molecular investigations allowed us to identify the presence of methanotrophic bacteria belonging to the Verrucomicrobia and to the Alpha- and Gamma-Proteobacteria in the soils of the geothermal area of Favara Grande at Pantelleria. While the presence of the former was not unexpected due to the fact that they include acidophilic and thermophilic organisms that were previously found in other geothermal environments, the latter are generally considered not adapted to live in harsh geothermal environments. Their presence in the soils of Pantelleria could be explained by the fact that these soils do not have extremely low pH values (>5). Indeed thermotollerant methanotrophic Gamma-proteobacteria, have been previously found in the sediments of thermal springs in Kamchatka (Kizilova et al., 2012). Such species could find their niches in the shallowest part of the soils of Favara Grande were the temperatures are not so high and they thrive on the abundant upraising hydrothermal methane. References: Cardellini C., Chiodini G., Frondini F., Granieri D., Lewicki J., Peruzzi L., 2003. Accumulation chamber measurements of methane fluxes: application to volcanic–geothermal areas and landfills. Appl. Geochem. 18, 45–54. Castaldi S., Tedesco D., 2005. Methane production and consumption in an active volcanic environment of Southern Italy. Chemosphere 58, 131–139. Chiodini G., Granieri D., Avino R., Caliro S., Costa A., 2005. Carbon dioxide diffuse degassing and estimation of heat release from volcanic and hydrothermal systems. J. Geophys. Res. 110, B08204. D’Alessandro W., Bellomo S., Brusca L., Fiebig J., Longo M., Martelli M., Pecoraino G., Salerno F., 2009. Hydrothermal methane fluxes from the soil at Pantelleria island (Italy). J. Volcanol. Geotherm. Res. 187, 147–157. D’Alessandro W., Brusca L., Kyriakopoulos K., Martelli M., Michas G., Papadakis G., Salerno F., 2011. Diffuse hydrothermal methane output and evidence of methanotrophic activity within the soils at Sousaki (Greece). Geofluids 11, 97–107 D’Alessandro W., Gagliano A.L., Kyriakopoulos K., Parello F., 2013. Hydrothermal methane fluxes from the soil at Lakki plain (Nisyros island, Greece). Bull. Geol. Soc. Greece, vol. XLVII Proc. of the 13th International Congress, Chania, Sept. 2013 Dunfield P.F., Yuryev A., Senin P., Smirnova A.V., Stott M.B., Hou S., Ly B., Saw J.H., Zhou Z., Ren Y, Wang J., Mountain B.W., Crowe M.A., Weatherby T.M., Bodelier P.L.E., Liesack W., Feng L., Wang L., Alam M., 2007. Methane oxidation by an extremely acidophilic bacterium of the phylum Verrucomicrobia. Nature, 450, 879–882. Etiope G., Fridriksson T., Italiano F., Winiwarter W., Theloke J., 2007. Natural emissions of methane from geothermal and volcanic sources in Europe. J. Volcanol. Geotherm. Res. 165, 76–86. Etiope G., Lassey K.R., Klusman R.W., Boschi E., 2008. Reappraisal of the fossil methane budget and related emission from geologic sources. Geophys. Res. Lett. 35, L09307. Islam T., Jensen S., Reigstad L.J., Larsen Ø., Birkeland N.K., 2008. Methane oxidation at 55°C and pH 2 by a thermoacidophilic bacterium belonging to the Verrucomicrobia phylum. Proc. Natl. Acad. Sci. 105, 300–304. Kizilova A.K., Dvoryanchikova E.N., Sukhacheva M.V., Kravchenko I.K., Gal’chenko V.F., 2012. Investigation of the communities of the Hot Springs of the Uzon Caldera, Kamchatka, by Molecular Ecological Techniques. Microbiology, 81, 606-613. Pol A., Heijmans K., Harhangi H.R., Tedesco D., Jetten M.S.M., Op den Camp H.J.M., 2007. Methanotrophy below pH 1 by a new Verrucomicrobia species. Nature, 450, 874–878.

Methane is released to the atmosphere by a wide number of natural (geological and biological) and anthropogenic sources, and is the second most important greenhouse gas after CO2. Microbial oxidation in soils by methanotrophic bacteria contributes to the removal of CH4 from the atmosphere and methanotrophic activity was also detected in volcanic/geothermal areas where degassing of endogenous gases occurs. Our aim is to describe the methanotrophs at the main exhalative area of Le Favare site at Pantelleria Island, where high CH4 consumption (up to 950 ng/g/ per h) was measured. Total soil bacterial diversity was analysed by TTGE of amplified 16S rRNA genes and the diversity of proteobacterial methanotrophs was investigated by creating a clone library of the amplified methane mono-oxygenase encoding genes, pmmoA. Enrichment cultures on a mineral medium in a CH4-enriched atmosphere led to the isolation of different strains that were identified as Methylocistis spp. Understanding the ecology of methanotrophy in geothermal sites will increase our knowledge of the role of such soils in methane emissions.

We report helium isotope data for 0.03–1 Ma olivine-bearing basaltic hawaiites from three volcanoes of the southern Italy magmatic province (Ustica, Pantelleria, and Linosa Islands). Homogenous H3e/H4e ratios (range: 7.3–7.6 Ra) for the three islands, and their similarity with the ratio of modern volcanic gases on Pantelleria, indicate a common magmatic end-member. In particular, Ustica (7.6±0.2 Ra) clearly differs from the nearby Aeolian Islands Arc volcanism, despite its location on the Tyrrhenian side of the plate boundary. Although limited in size, our data set complements the large existing database for helium isotope in southern Italy and adds further constraints upon the spatial extent of intraplate alkaline volcanism in southern Mediterranea. As already discussed by others, the He-Pb isotopic signature of this magmatic province indicates a derivation from a mantle diapir of a OIB-type that is partially diluted by the depleted upper mantle (MORB mantle) at its periphery.

Tunisia is characterized by hot and warm groundwaters (temperature up to 75 °C) which represent the surface manifestation of geothermal systems hosted in carbonate-evaporite rock sequences. The T-conditions of Tunisia deep thermal reservoirs are here evaluated for the first time at the regional scale. The results here shown clearly highlight the limitations inherent in the application of common geothermometric methods in the estimation of equilibrium temperatures in sedimentary environments. The modeling approach proposed by Chiodini et alii (1995), which makes use of the ratios between dissolved HCO3, SO4 and F, provides the most reliable results, and allows us to derive equilibrium temperatures up to 200 °C for the Tunisian thermal reservoirs. Very high equilibrium pCO2 (100 bar) values are also estimated, likely indicative of the confined aquifer conditions.

Methane plays an important role in the Earth’s atmospheric chemistry and radiative balance being the second most important greenhouse gas after carbon dioxide. Methane is released to the atmosphere by a wide number of sources, both natural and anthropogenic, with the latter being twice as large as the former. It has recently been established that significant amounts of geological methane, produced within the Earth’s crust, are currently released naturally into the atmosphere. Active or recent volcanic/geothermal areas represent one of these sources of geological methane. Microbial oxidation in soils contributes for about 3-9% to the total removal of CH4 from the atmosphere. Recent studies evidenced methanotrophic activity also in soils of volcanic/geothermal areas notwithstanding their harsh environmental conditions (high temperatures, low pH and high concentrations of H2S and NH3). The purpose of our study was to verify the methanotrophic potential and the bacterial diversity of the soils of the main geothermal area of Pantelleria island (Italy). Laboratory incubation experiments with soil samples collected at the main exhalative area showed methane consumption values of up to 9500 ng per g of dry soil per hour while soils collected outside the geothermal area less than 6 ng/g/h. Geothermal soils showed their maximum methane consumption in the shallowest part of the soil profile (0-3 cm) mantaining high values (>100 ng/g/h) at least up to dephts of 15 cm. Furthermore they showed the maximum consumption at about 37°C, showing a still recognizable consumption (>20 ng/g/h) at 80°C, and a positive correlation with the methane concentration in the incubation atmosphere. These results can be considered a clear evidence of the presence of methanotrophs. In order to evaluate the bacterial diversity, soil metagenomic DNA was extracted from Le Favare and analysed using a Temporal Temperature Gradient Electrophoresis (TTGE) analysis of the amplified Bacterial 16S rRNA gene. The amplification of metagenomic DNA with primers targeting Proteobacterial and Verrucomicrobial MMO (methane monooxygenase) genes is in progress. Enrichment cultures on a mineral medium in a CH4-enriched (25%) atmosphere allowed to isolate different strains that are under characterization.

Besides human activities, volcanoes also introduce significant quantities of potentially harmful chemical compounds into the environment, mainly in the forms of gases and particles. High-temperature emissions from persistently degassing volcanoes are a known source of trace metal emissions to the atmosphere which may have important environmental consequences. Among these metals, mercury (Hg) is of particular interest since it is a toxic volatile metal found at elevated concentrations in remote regions of the world. Many natural Hg pathways include a recycled component of anthropogenic material. The anthropogenic contribution to the global atmospheric Hg budget is now well constrained, with most recent estimates ranging from 1484 [AMAP/UNEP, 2008] to 1894 t yr-1 [2005/2006 inventory; Streets et al 2009]. Hg emissions from natural sources are, on the other hand, still poorly characterized, though being likely in the same range [estimates from 500 to 3000 t yr-1; Nriagu 1989] of those reported for anthropogenic release. The poorly constrained Hg speciation in volcanic emissions, and the limited number of studies so far, have hampered accurate estimation of the global Hg flux, with previous estimates ranging from as low as ~1 t yr-1 [Ferrara et al. 2000] to >800 t yr-1 [Varekamp and Buseck 1986]. Besides, historical archives such as ice-cores documented that large eruptions can release quantities of Hg similar to the present anthropogenic burden. The effects, or potential effects, of active volcanoes on the environment and on public health is an important issue, given the large number of communities and populated cities that exist and keep growing around and upon active and dormant volcanoes. Poisonous gases, and in the specific mercury, are also released continuously or semi-continuously into the environment by non-erupting volcanoes causing however regional environmental effects equally severe to the volcanic events of massive proportions. A major uncertainty regarding the impacts of volcanic Hg is the extent to which Hg emitted from a volcano is deposited locally or transported globally. Actually, volcanogenic mercury fluxes are poorly constrained and there is an almost complete absence of data on the factors (magma composition, eruptive temperature, or volcanic gas composition) that influence its degassing rates at different volcanoes. In order to better understand the role of volcanoes in the global mercury budget and to extend the currently limited dataset on volcanogenic Hg emissions, a number of field campaigns were carried out to evaluate Hg flux in volcanic gases by the simultaneously-determined Hg/SO2 ratios and SO2 flux. Measurements were made at the crater edge of a number of quiescently degassing volcanoes (Etna, Stromboli, Asama, Miyakejima, Montserrat, Ambrym, Yasur, Nyiragongo, Masaya). Emissions from open vents were investigated and concentrations of Hg elevated above usual background levels (rural areas far from emitting source, 1-2 ng m-3) were detected. We found that in volcanic plume mercury is mainly found as the relatively inert form of gaseous elemental mercury (GEM) with concentrations ranging from 18 to 373 ng Hg m-3. GEM has a long atmospheric lifetime estimated as 0.5-2 years due to its low solubility and gaseous nature, promoting long-range global transport [Nriagu 1989; Pyle and Mather, 2003]. High variability found in plume Hg concentrations depends on both volcanic (gas flux) and non-volcanic factors (extent of mixing and dilution in the vent; wind speed and direction), hence comparing the concentrations of Hg species between different volcanoes is not necessarily meaningful and it is more useful to compare Hg/SO2 ratios. Using our determined Hg/SO2 mass ratios in tandem with the simultaneously-determined SO2 emission rates, we estimated that the investigated volcanoes have Hg emission rates ranging from 0.2 to 18 t•yr-1 (corresponding to a total Hg flux of ~54 t•yr-1). Based on our dataset and previous works, we propose that a Hg/SO2 plume ratio ~10-5 is best-representative of gas emissions from quiescent degassing volcanoes. Using this ratio, we infer a global volcanic Hg flux from persistent degassing of ~95 t•yr-1. If representative of other volcanoes, these results suggest degassing of basaltic magma plays an important part of the global atmospheric Hg budget. According to both these data and recent observations [Bagnato et al., 2010], volcanism thus would contribute from as little as 12 to as much as 78% of the estimated global natural Hg budget. Volcanic Hg therefore has a greater potential for local and global environmental impact than Hg from the more prodigious but diffuse natural and anthropogenic sources. In particular, Hg released from Mt Etna degassing, the largest active volcano in Europe, represents approximately 5% of the total industrial Hg emissions in the Mediterranean area [~105 t•yr-1, Pirrone et al., 2009] and about 2% of the anthropogenic Hg supplies throughout Europe [~239 t•yr-1, EMEP 2002]. With these new estimates we critically revisit the idea that volcanic activity is a trivial contribution to the atmospheric Hg supply in the Mediterranean area. We shall re-examine the status of the global volcanic mercury emissions budget and its uncertainties, even when only considering quiescent phases of volcanic activity. Besides, large sectors of the planet (SW Pacific) are still un-explored, and thus our global Hg flux value estimated from passive degassing may constitutes a lower limit. However, Hg flux measurements in eruptive gases is a priority for future mercury research at volcanoes.

Geochemical comparison between some metals (As, Cd, Cu, Pb, Se, V, Zn) emissions from an active volcano (Mt. Etna) and a highly industrialized area (Šalek Valley) showed some interesting similarities: in general, most of the elements emitted into the atmosphere do not return to the Earth’s surface and are therefore dispersed into the environment. Exceptions for Šalek Valley are Cd, which probably derives in large part from rock leaching, and in part As and Pb, which fall mostly as ash. Also, Etna’s emissions are richer in Cd and Cu, whereas industrial emissions at Šalek Valley are richer in V and Zn. All other metals have similar fluxes in the two types of emissions.

Mt. Etna, in the eastern coast of Sicily (Italy), is one of the most active and most intensely monitored volcanoes of the planet. It is widely recognized as a big source of volcanic gases, such as CO2, SO2 and halogens, to the troposphere in the Mediterranean basin, and its gas emissions account for a significant percentage respect to the worldwide average volcanic budget. The SO2 flux from Mt. Etna’s plume has been routinely measured by the INGV since 1987. SO2 flux ranges between 600 to 25000 Mg/d; fluxes greater than 100000 Mg/d were prevalently measured during eruptive events. During eruptive periods, Etna’s emissions can be dispersed over long distances and cover wide areas of the Mediterranean region. Mt. Etna is also considered a huge source of many trace elements to the atmosphere on regional and global scale. On the morning of December 24th 2018, a moderate lateral eruption of the Mt. Etna started. This eruption was related to an intrusion of a magmatic dike on the high eastern flank of the volcano, through a 2 kilometres long fracture in the NNW SSE direction. At the same time, the summit craters produced a continuous strombolian activity generating a very dense ash plume, dispersed by the wind into the S/SE direction. From June 2018 to June 2019, atmospheric precipitations were collected in the area of Siracusa, a city on the east coast of Sicily, about 80 km SSE of Mt. Etna, and in the area of Milazzo, a city on the northern coast of Sicily. Atmospheric precipitations were monthly collected through a network of 12 pluviometers; the collectors were open during the entire exposure time, receiving both wet and dry deposition (bulk collectors). All the collected water samples were analysed for major ion contents and for a large number of trace elements by ICPOES and ICPMS. During the eruptive period (from 24th to 27th December 2018), the prevailing winds blew from the North direction and there were light rainfalls in the monitored sites (between 0.2 mm in Siracusa and Augusta, and 1.6 mm in Palazzolo Acreide). As a consequence, gases and particles of Etna’s plume were carried for long distance from the emission point, and they were deposited as dry and wet deposition also in the area of Siracusa. During the eruption event and in the following days, the plume reached distances of more than 300 km from the emission point (island of Malta). The samples collected in the study area of Siracusa during the period straddling the eruptive event are characterized by high concentrations of some major ions, such as Fluoride (up to 0.88 mg/l), Chloride (up to 124 mg/l) and Sulphate (23.1 mg/l). These ions derive mainly from the emitted volcanic gases (HF, HCl and SO2). The effect of the described eruption is also visible in the high concentrations of some trace elements, such as Aluminium, Thallium and Tellurium. The mean concentrations of the selected trace elements in the samples collected in the area of Siracusa, in the period before the eruptive event, are: 18.2 μg/l for Aluminium, 0.009 μg/l for Thallium, while Tellurium was always under the detection limit (0.004 μg/l); the concentrations of the same elements in the samples collected during the eruptive event reach 152 μg/l for Aluminium, 0.16 Âg/l for Thallium and 0.025 μg/l for Tellurium, therefore showing a strong enrichment. While Thallium and Tellurium are highly volatile elements typically enriched in volcanic emissions, Aluminium is a refractory element that was probably released by the dissolution of the related volcanic ashes. 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 plume and therefore the signature of the eruption is not visible in the samples collected in that area, as shown by the mean values of the selected trace elements: 24.2 μg/l, 0.026 μg/l and < 0.004 μg/l for Aluminum, Thallium and Tellurium respectively. In conclusion, close to active volcanic areas, volcanic emissions have to be considered among the major contributors to the chemistry of rainwater, especially during eruptive periods.

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.

Greece, a country characterised by intense seismic and volcanic activity, has a complex geodynamic and geological setting that favours the occurrence of many gas manifestations. In this study, we address the origin of CH 4 and light hydrocarbons in cold and thermal emissions discharging along the Hellenic territory. Also, we investigate their possible relationship with the main geochemical composition of the gases and the different geological settings of the sampling sites. For this purpose we collected 101 new samples that were analysed for their chemical (O 2 , N 2 , CH 4 , CO 2 , He, Ne, Ar, H 2 , H 2 S and C 2 -C 6 hydrocarbons) and isotopic (R/R A , δ 13 C-CO 2 , δ 13 C-CH 4 and δ 2 H-CH 4 ) composition. Results show that CH 4 presents a wide range of concentrations (from 13 C-CH 4 from −79.8 to +45.0‰ vs. V-PDB; δ 2 H-CH 4 from −311 to +301‰ vs. V-SMOW). Greece was subdivided in four geologic units (External [EH] and Internal [IH] Hellenides, Hellenic Hinterland [HH] and active Volcanic Arc [VA]) and a decreasing CH 4 concentration from EH to HH was recognized, whereas CH 4 showed intermediate concentrations in VA. The CH 4 /(C 2 H 6 + C 3 H 8 ) ratios (from 1.5 to 93,200), coupled with CH 4 isotopic features, suggest that the light alkanes derive from different primary sources and are affected by secondary processes. An almost exclusive biotic, mainly microbial, origin of CH 4 can be attributed to EH gases. Cold gases at IH have mainly a thermogenic origin, although some gases connected to continental serpentinization may have an abiogenic origin. Methane in gases bubbling in thermal waters of IH, HH and VA and fumarolic gases of the VA seem to have an abiogenic origin, although their chemical and isotopic characteristics may have been produced by secondary oxidation of thermogenic CH 4 , a process that in some of the sampled gases causes extremely positive isotopic values (δ 13 C-CH 4 up to +45.0‰ vs. V-PDB and δ 2 H-CH 4 up to +301‰ vs. V-SMOW).

Κατά την περίοδο 2004 με 2017, συλλέχθηκαν περισσότερα από 350 δείγματα ελεύθερων και διαλελυμένων αερίων στην Ελλάδα. Μαζί με αυτά συνυπολογίστηκαν και βιβλιογραφικά δεδομένα. Για καλύτερη κατανόηση της μελέτης, η χώρα διαιρέθηκε σε τέσσερις γεωλογικές ενότητες (Εξωτερικές [EH] και Εσωτερικές [IH] Ελληνίδες, Ελληνική Ενδοχώρα [HH] και ενεργό ηφαιστειακό τόξο [VA]) και με βάση τον συγκεκριμένο διαχωρισμό ερευνήθηκε η πιθανή σχέση της κύριας γεωχημικής σύστασης των αερίων με τα διάφορα γεωλογικά και γεωδυναμικά καθεστώτα των περιοχών δειγματοληψίας. Τα δείγματα αναλύθηκαν για την χημική (O2, N2, CH4, CO2, He, Ne, Ar, H2, H2S και C2-C6 υδρογονάνθρακες) και ισοτοπική τους (R/RA, δ13C-CO2, δ13C-CH4 and δ2H-CH4) σύσταση. Οι συγκεντρώσεις κυμαίνονταν από 0.10 έως 3370 μmol/mol για το He, 600 έως 995,000 μmol/mol για το N2, 0.60 έως 915,000 μmol/mol για το CH4 και 17 έως 1,000,000 μmol/mol για το CO2, ενώ οι ισοτοπικές τους τιμές από 0.01 έως 7.10 R/RA, -29.91 έως +6.00 vs. V-PDB για το δ13C-CO2, -79.8 έως +45.0‰ vs. V-PDB για το δ13C-CH4 και -311 έως +301‰ vs. V-SMOW για το δ2H-CH4. Λαμβάνοντας υπ’όψιν τις τιμές των R/RA και 4He/20Ne, υπολογίστηκε η συνεισφορά της ατμόσφαιρας, του μανδύα και του φλοιού για το He. Η μεγαλύτερη μανδυακή συνεισφορά (έως και 90%) βρέθηκε στο VA, ενώ η χαμηλότερη (0-20%) στο EH. Η συνεισφορά της ατμόσφαιρας ήταν σχετικά αμελητέα. Σύμφωνα με την γεωγραφική κατανομή των αερίων, είναι εμφανές πως το R/RA αυξάνεται σε περιοχές που χαρακτηρίζονται από: i) λεπτό φλοιό; ii) αυξημένες τιμές ροής θερμότητας; iii) πρόσφατη (Πλειστόκενο-Τεταρτογενής) ηφαιστειακή δραστηριότητα; και iv) τοπικά εκτατικά ή διασταλτικά ρήγματα. Οι υψηλότερες τιμές βρέθηκαν κατά μήκος του VA και οι χαμηλότερες στις EH. Επιπλέον, με βάση τις τιμές των CO2/3He και δ13C-CO2, υπολογίστηκε η συνεισφορά των Ιζηματογενών, Μανδυακών και Ασβεστολιθικών end-members του CO2. Οι πλειοψηφία των δειγμάτων παρουσίασε μία κυρίως ασβεστολιθική σύσταση για τον C, ενώ μόνο λίγα δείγματα έδειξαν μανδυακή σύσταση. Παρ’όλα αυτά, με τα υπάρχοντα δεδομένα, είναι αδύνατος ο διαχωρισμός του CO2 που προέρχεται από τους ασβεστολίθους του φλοιού και από εκείνους της υπό βύθισης πλάκας. Επί προσθέτως, λόγω της σύνθετης γεωδυναμικής ιστορίας, η ισοτοπική σύσταση του μανδυακού C θα μπορούσε να είναι επηρεασμένη από μετασωμάτωση συσχετιζόμενη με την βύθιση της πλάκας, όπως συμβαίνει και στην γειτνιακή περιοχή της Ιταλίας, κάνοντας την ισοτοπική του σύσταση πιο θετική. Σε τέτοια περίπτωση, η συνεισφορά του μανδύα θεωρείται ότι έχει υποτιμηθεί. Κάποια δείγματα παραθέτουν πολύ χαμηλες τιμές CO2/3He και δ13CO2 λόγω απώλειας του CO2, η οποία έχει προκληθεί είτε από διάλυση του CO2 σε υπόγεια νερά μικρού βάθους είτε από την καθίζηση του ασβεστίτη που λαμβάνει μέρος στε ορισμένες θερμές πηγές. Από την άλλη μεριά, οι τιμές του CH4/(C2H6+C3H8) (από 1.5 έως 93,200) σε συνδιασμό με τα ισοτοπικά χαρακτηριστικά του CH4, συνιστούν πως οι ελαφριές αλκάνες προέρχονται από διαφορετική αρχική πηγή και αρκετές φορές επηρεάζονται από δευτερογενή διαδικασίες. Στα αέρια των EH παρατηρείται μια σχετικά αποκλειστική βιοτική, κυρίως μικροβιακή, προέλευση για το CH4. Τα αέρια των ψυχρών πηγών των IH έχουν κυρίως θερμογενή προέλευση, αν και κάποια από αυτά συνδέονται με ηπειρωτικές σερπεντινιώσεις και μοιάζει να έχουν αβιοτική προέλευση. Το CH4 στις θερμές πηγές των IH, HH and VA και στα φουμαρολικά αέρια του VA φαίνεται να είναι κυρίως αβιοτικό, αν και τα χημικά και ισοτοπικά χαρακτηριστικά του μοιάζει να έχουν επηρεαστεί από δευτερογενή οξείδωση του CH4 θερμογενούς προέλευσης. Τέλος, κάποια από τα δείγματα παρουσιάζουν αρκετά θετικές ισοτοπικές τιμές (δ13C-CH4 έως +45.0‰ vs. V-PDB και δ2H-CH4 έως +301‰ vs. V-SMOW) πιθανότατα λόγω οξείδωσής τους από μικρόβια. In the period from 2004 to 2017, more than 350 samples of free and dissolved gases were collected along the whole Hellenic area. Some literature data have also been taken into consideration. For a better comprehension of this study, Greece was subdivided in four geologic units (External [EH], Internal [IH] Hellenides, Hellenic Hinterland [HH] and active Volcanic Arc [VA]) and based on that division, I investigate the possible relationship of the main geochemical composition of the gases with the different geological and geodynamical settings of the sampling sites. Samples have been analysed for their chemical (O2, N2, CH4, CO2, He, Ne, Ar, H2, H2S and C2-C6 hydrocarbons) and isotope (R/RA, δ13C-CO2, δ13C-CH4 and δ2H-CH4) composition. The concentrations range from 0.10 to 3370 μmol/mol for He, 600 to 995,000 μmol/mol for N2, 0.60 to 915,000 μmol/mol for CH4 and 17 to 1,000,000 μmol/mol for CO2, whereas the isotope values range from 0.01 to 7.10 for R/RA, -29.91 to +6.00 vs. V-PDB for δ13C-CO2, -79.8 to +45.0‰ vs. V-PDB for δ13C-CH4 and -311 to +301‰ vs. V-SMOW for δ2H-CH4. Considering the R/RA and 4 He/20Ne ratios the atmospheric, mantle and crustal contributions for He have been calculated. The highest mantle contribution (up to 90%) is found in the VA, whereas the lowest in continental Greece (0-20%). Atmospheric contribution is mostly negligible. Taking into consideration the geographical distribution of the gases, it is evident that the R/RA increases in areas characterised by: i) thin crust; ii) elevated heat flow values; iii) recent (PleistoceneQuaternary) volcanic activity; and iv) deep routed extensional or transtensional regional faults. The highest values are therefore found along VA and the lowest in EH. Furthermore, based on the CO2/3He and δ13C-CO2 values, the contribution of Sediment, Mantle and Limestone endmembers for CO2 was determined. The majority of the collected samples present a prevailing limestone C component and only few samples have a prevailing mantle C component. However, with the present data, it is not possible to distinguish CO2 deriving from crustal and slab-related limestones. Additionally, due to the complex geodynamic history, the mantle C isotope composition could be affected by subduction-related metasomatism and, similarly to the nearby Italian area, the C isotope composition could be more positive. In this case, the mantle contribution is probably underestimated. Some samples display very low CO2/3He and δ13CO2 values due to the CO2 loss caused either by dissolution of CO2 in shallow groundwater or by the calcite precipitation that is taking place in most of the thermal springs. On the other hand, the CH4/(C2H6+C3H8) ratios (from 1.5 to 93,200) coupled with CH4 isotopic features, suggest the light alkanes derive from a different primary source and are sometimes affected by secondary processes. An almost exclusive biotic, mainly microbial, origin of CH4 can be attributed to EH gases. Cold gases at IH have mainly a thermogenic origin, although some gases connected to continental serpentinization may have an abiogenic origin. Methane in gases bubbling in thermal waters of IH, HH and VA and fumarolic gases of the VA seem to have a prevailing abiogenic origin, although their chemical and isotopic characteristics may have been produced by secondary oxidation of thermogenic CH4. Finally, in some of the sampled gases, the isotopic values are extremely positive (δ13C-CH4 up to +45.0‰ vs. V-PDB and δ2H-CH4 up to +301‰ vs. V-SMOW) most probably caused by microbial oxidation.

Ogni anno, 22 Tg di CH4 vengono rilasciati in atmosfera da numerose sorgenti sia naturali che antropiche. Il metano riveste un ruolo molto importante nella chimica dell’atmosfera terrestre e nel bilancio dell’energia radiante assorbita, essendo il secondo gas serra più potente dopo la CO2. Le aree vulcaniche e geotermali contribuiscono al flusso di metano in atmosfera, essendo vaste aree di degassamento. Studi preliminari hanno stimato che le emissioni globali di metano dai sistemi geotermali e vulcanici europei sono nel range di 4-16 kt a-1. Questa stima è stata ottenuta indirettamente dai dati delle emissioni di CO2 o H2O e dal rapporto del flusso CO2/CH4 oppure H2O/CH4 misurati nelle principali fumarole. La stima del metano emesso globalmente dalle aree vulcaniche e geotermali non è ancora ben definita in quanto il bilancio tra le emissioni per degassamento dai suoli e il consumo di metano per ossidazione microbica è ancora poco noto. Inoltre, le misure di flusso di metano sono molto difficili da eseguire e si hanno a disposizioni pochi dati. Alcuni metodi, seppur accettabili al fine di ottenere stime sul flusso di metano, escludono completamente la possibilità che il metano venga rimosso per via microbica dai batteri metanotrofi. A scala globale, l’ossidazione microbica del metano contribuisce alla rimozione di circa il 3-9% del metano dall’atmosfera. Ma l’importanza dei batteri metanotrofi è ancora maggiore in quanto questi ossidano la maggior parte del metano prodotto nel suolo e nel sottosuolo prima che questo raggiunga l’atmosfera. Le condizioni ambientali dei suoli vulcanici e geotermali (ad esempio scarso contenuto in ossigeno, alta temperature, attività protonica, ect.) sono stati da sempre considerati inospitali per i batteri metanotrofi. Tuttavia, di recente è stata dimostrata la presenza di batteri acidofili e termofili appartenenti al phylum dei Verrucomicrobia. Questi organismi sono stati individuati alla Solfatara di Pozzuoli (Italia), ad Hell’s gate (Nuova Zelanda) ed in Kamchatka (Russia). Qui riportiamo l’attività metanotrofa riscontrata nei suoli dell’Isola di Pantelleria (Italia), dell’Isola di Vulcano (Italia), di Sousaki (Grecia), di Nea Kameni- Santorini (Grecia), e dell’Isola di Nisyros (Grecia). Evidenze di rimozione microbica del metano in questi suoli era già stata riscontrata nel rapporto dei flussi di CO2/CH4, che risultava sempre inferiore rispetto a quello atteso, indicando una perdita di CH4 durante il suo movimento verso la superficie. Esperimenti per la misura del consumo di metano sono stati eseguiti usando i suoli di Pantelleria, Vulcano, Nea kameni, Nisyros e Sousaki. Questi esperimenti hanno rivelato tassi di consumo fino a 950, 48, 15, 39 e 520 ng CH4 h-1 per ogni grammo di suolo (peso secco), rispettivamente. Solo pochi campioni non hanno indicato consumo di metano. L’analisi dei gas del suolo e le caratteristiche chimico-fisiche del suolo ci hanno permesso di discriminare i fattori principali che influenzano la presenza dei metanotrofi e il tasso dei consumo del metano. La composizione del gas dal suoli, e in particolare il contenuto di CH4 e di H2S rappresentano il fattore discriminate per i metanotrofi. infatti, l’isola d Vulcano e di Nisyros, il cui contenuto in H2S raggiunge circa 250000 ppm, mostrano i consumi più bassi. In aggiunta nei suoli geotermali e vulcanici l’H2S contribuisce all’abbassamento del pH dei suoli. I valori di consuma maggiori sono stati misurati nell’isola di Pantelleria dove l’H 2S è meno di 20 ppm e il pH è vicino alla neutralità. Analisi microbiologiche e molecolari hanno permesso di riscontrare nei suoli di Pantelleria la presenza di batteri metanotrofi affiliati ai Gamma ed agli Alfa-Proteobatteri ed agli acido-termofili Verrucomicrobia. Il metanotrofo coltivabile appartenete al genere Methylocystis (Alfaproteobatterio) e il Gammaproteobatterio Methylobacterium sono stati isolati attraverso colture di arricchimento. Gli isolati mostrano ampi range di tolleranza di pH e temperatura e un tasso di ossidazione fino a 450 ppm/h. Attraverso l’amplificazione del gene pmoA, basandosi sui metodi coltura-indipendenti è stata rivelata un’ampia diversità di batteri metanotrofi appartenenti ai Proteobatteri (α- e γ-) ed ai Verrucomicrobia. Questo è il primo report in cui si dimostra la coesistenza di entrambi i phyla di metanotrofi in un sito geotermale/vulcanico. La presenza dei metanotrofi Proteobatteri era inaspettata perché le condizioni di sito sono state considerate inadeguate e può essere spiegata del pH non eccessivamente basso (>5) di questo specifico sito geotermale. Queste specie possono aver trovato la loro nicchia negli strati più superficiali dei suoli di Favara Grande a Pantelleria dove le temperature non sono così alte ed è presente una forte risalita di metano. capire l’ecologia dei metanotrofi nei siti geotermali e vulcanici aumenterà le conoscenze nel loro ruolo nelle emissioni di metano in atmosfera. Yearly, 22 Tg of CH4 are released in to the atmosphere from several natural and anthropogenic sources. Methane plays an important role in the Earth’s atmospheric chemistry and radiative balance being the most important greenhouse gas after carbon dioxide. Volcanic/geothermal areas contribute to the methane flux, being the site of widespread diffuse degassing of endogenous gases. Preliminary studies estimated a total CH4 emission from European geothermal and volcanic systems in the range 4-16 kt a-1. This estimate was obtained indirectly from CO2 or H2O output data and from CO2/CH4 or H2O/CH4 values measured in the main gaseous manifestations. The total estimated CH4 emission from geothermal/volcanic areas is still not well defined since the balance between emission through degassing and consumption through soil microbial oxidation is poorly known. Moreover, methane soil flux measurements are laboratory intensive and very few data have been collected until now in these areas. Such methods, although acceptable to obtain order-of-magnitude estimates, completely disregards possible methane microbial oxidation within the soil carried on by the methanotrophs. At the global scale, microbial oxidation in soils contributes for about 3-9% to the total removal of methane from the atmosphere. But the importance of methanotrophic organisms is even larger because they oxidize the greatest part of the methane produced in the soil and in the subsoil before its emission to the atmosphere. Environmental conditions in the soils of volcanic/geothermal areas (i.e. low oxygen content, high temperature and proton activity, etc.) have long been considered inadequate for methanotrophic microorganisms. But recently, it has been demonstrated that methanotrophic consumption in soils occurs also under such harsh conditions due to the presence of acidophilic and thermophilic Verrucomicrobia. These organisms were found in Italy at the Solfatara at Pozzuol (Italy), at Hell’s Gate (New Zealand) and in Kamchatka (Russia), pointing to a worldwide distribution. Here we report on methane oxidation rate measured in Pantelleria Island (Italy), Vulcano Island (Italy), Sousaki (Greece), Nea Kameni (Santorini) and Nisyros (Greece) soils. Clues of methane microbial oxidation in soils of these areas can be already found in the CH4/CO2 ratio of the flux measurements which is always lower than that of the respective fumarolic manifestations indicating a loss of CH4 during the travel of the gases towards earth’s surface. Laboratory methane consumption experiments made on soils collected at Pantelleria, Vulcano, Nea Kameni, Nysiros and Sousaki revealed for most samples consumption rates up to 950, 48, 15, 39 and 520 ng CH4 h-1 for each gram of soil (dry weight), respectively. Only few soil samples displayed no methane consumption activity. Analysis on soil gases and chemical-physical characteristics of the soils allowed us to discriminate the main factors that influenced the methanotrophs presence and the methane consumption rate. Soil gases composition, and in particular the amount of the CH4 and H2S, represent the main discriminating factor for methanotrophs. In fact, Vulcano and Nisyros Island, whose soil gas contained up to 250000 ppm of H2S, showed the lowest consumption rate. Moreover, in geothermal/volcanic soils H2S contribute to the soil pH lowering; highest methane consumption were recorded in Pantelleria island were H2S is less than 20 ppm and pH close to the neutrality were measured. Microbiological and molecular analyses allowed to detect the presence of methanotrophs affiliated to Gamma and Alpha-Proteobacteria and to the newly discovered acido-thermophilic methanotrophs belong to the Verrucomicrobia phylum in soils from Pantelleria. Culturable methanotrophic Alphaproteobacteria of the genus Methylocystis and the Gammaproteobacteria Methylobacterium were isolated by enrichment cultures. The isolates show a wide range of tolerance to pH and temperatures and an average methane oxidation rate up to 450 ppm/h. A larger diversity of (α- and γ-) proteobacterial and verrucomicrobial methanotrophs was detected by a culture-independent approach based on the amplification of the methane mono-oxygenase gene pmoA. This is the first report describing coexistence of both the methanotrophic phyla (Verrucomicrobia and Protebacteria) in the same geothermal site. The presence of proteobacterial methanoptrophs, in fact, was quite unexpected because they are generally considered not adapted to live in such harsh environments and could be explained by not really low pH values (> 5) of this specific geothermal site. Such species could have found their niches in the shallowest part of the soils of Favara Grande were the temperatures are not so high and thrive on the abundant upraising methane. Understanding the ecology of methanotrophy in geothermal sites will increase our knowledge of their role in methane emissions to the atmosphere.

Years of scientific research have shown that acidification of oceans (OA) is an undisputed fact. Why is it so important to increase knowledge about OA? Because many animals and plants in the ocean have calcium carbonate skeletons or shells, and a decreasing in pH can affect their population health state and the marine-ecosystem structure. Another point of view about OA which must to be considered is that it may alter the behavior of sediment-bound metals, modifying their bioavailability and thus toxicity. The toxic free-ion concentration of metals such as copper may increase by as much as 115% in coastal waters in the next 100 years due to reduced pH. Since increasing atmospheric CO2 over the next 200 years will cause a pH decrease in ocean water, and consequently change the organic and inorganic speciation of metals in surface ocean waters, and it will effect on their interaction with marine species. Most of the intense submersed hydrothermal seeps are located near the isthmus of the Baia di Levante along the beach (38°25’01.44”N, 14°57’36.29”E), where dispersed underwater leaks cover a 130 × 35m shallow water area (

This research is focused on the geochemistry of Tellurium (Te) in active volcanic environments. To this end concentrations of Te have been measured on different matrices (plume, ashes, soils, atmospheric depositions and plants). Samples were collected from different volcanoes around the world: volcanic aerosols from Etna and Vulcano (Italy), Turrialba (Costa Rica), Myakejima, Asama and Aso (Japan), Mutnovsky and Gorely (Kamchatka, Russia), Copahue (Argentina), Nyamuragira and Nyiragongo (D.R. Congo); atmospheric depositions from Etna and Vulcano (Italy), Nyiragongo (D.R. Congo); ash from Etna (Italy), Copahue (Argentina), San Miguel (El Salvador). Among with plume and rain samples, several leaves of plants from volcanic areas were collected for biomonitoring investigations: Etna, Vulcano and Stromboli (Italy), Nyiragongo (D.R. Congo), Nisyros (Greece), Gorely (Kamchatka), Turrialba (Costarica), Masaya (Nicaragua), Soufriere (Guadalupe); for comparison plant samples were collected also from an industrial area (Augusta, Italy) and a rural forest (Ficuzza, Italy). Samples of soils were also collected from Nisyros (Greece) to better understand the soil-plant distribution. From a literature review, there is a scarcity of data available about Tellurium abundances in the environment, expecialy for volcanic areas. This fact can be ascribed to the scarce use of this element in the past. During the last decades, the use of Te increased considerably due to its importance for electronics and solar photovoltaic manufacturing. Moreover, the recent natural disaster of Fukushima in March 2011 drew attention to the environmental impact of isotope Tellurium-132, produced after the nuclear power plant failure. As consequence, a lot of new studies are focused on Te behaviour in the environment. Regarding Te plume concentrations and fluxes from active volcanoes, only few estimations were reported in previous studies. Sixty-five plume samples were collected and analysed thus significantly increasing the existing worldwide dataset. The concentrations of Te detected range from

This research indicates the fate of Zr, Hf and Rare Earths during their sublimation from the high-temperature gas phase (100° - 420 °C), in volcanic systems associated with different geodynamic regimes, and processes associated with volcanic sublimation representing the last natural “inorganic” interface where a detailed investigation into the behaviour of Rare Earths had never been conducted. The research was carried out in active volcanic systems at Vulcano (Aeolian Islands, Italy), Santorini (Cyclades Islands, Greece), Phlegrean Fields (Italy), Tenerife (Canary Islands, Spain) and Fogo Island (Cape Verde) where both fumaroles and thermal waters from submarine springs and inland wells were collected and investigated. Both solid newly forming sublimates and the coexisting volcanic gas phase were studied in fumaroles in order to evaluate partitioning of the elements studied during the sublimation. Volatile geochemistry of Zr, Hf and Rare Earths (hereafter reported REE, being the sum of lanthanides and yttrium) data suggested a scenario where REE are transported in the volcanic gas phase as chloride complexes. This indication is apparently also confirmed for Zr and Hf by the Zr partitioning in the volcanic gas phase during sublimation relative to Hf. This evidence is attributed to the formation of [(Zr,Hf)Cl4(H2O)4] and other Cl-complexes that are more stable in the volatile phase when Zr is the coordinating metal relative to Hf. Features of shale-normalised REE patterns show positive Gd anomalies in volcanic gas during the sublimation whose amplitude progressively grows with increasing HCl contents in volcanic gas. These features are consistent with reference values of stability constants for chloride-REE complexes rather than for fluorine- and other REE complexes. This data may explain several instances of medium REE enrichments in natural waters during and immediately after large volcanic eruptions and suggests a particular Gd fate relative to other REE during the emission of volcanic soluble substances. Geochemical evidence coming from hydrothermal waters from Vulcano and Santorini Islands confirm the above-mentioned suggestion about the particular Gd behaviour in volcanic fluids since positive Gd anomalies are recognised in waters from submarine vents. Here Gd/Gd* ii up to 1.6 are associated with clear signs of W-type tetrad effects that allow us to identify these fluids as those leaching the authigenic solids that are immediately formed during the mixing between the hot reducing and acidic hydrothermal fluids with cold, oxidizing and basic seawater close to the vent. This and other geochemical evidence along with model calculations allow us to identify two different water groups in terms of physical-chemical characters, calculated saturation/oversaturation with respect to carbonates (group 1 waters) and Fe-oxyhydroxides (group 2 waters) and reciprocal Zr-Hf behaviour dissolved in natural pools. In both waters, the dissolved speciation of these elements is dominated by [Zr(OH)4]0 e [Hf(OH)5]- complexes. These species being differently charged, they fractionate during interactions with occurring solid surfaces. Our data confirms that Zr and Hf undergo a competition process between dissolved speciation and surface adsorption, but also suggests that the larger Hf surface reactivity, especially onto Fe-oxyhydroxides, can be related to the Hf surface complexation rather than to a simple interaction attributed to electrostatic attractions. Our findings prove that passive volcanic degassing can represent a suitable Gd source in a soluble and bioavailable form. Model calculations based of CO2 fluxes from the studied active volcanic areas indicate that about 1 kg Gd per year is released as a whole into the atmosphere. Comparing this value with reference data, this indication suggests that the volcanic Gd-flux is of the same order of magnitude as the yearly anthropogenic Gd delivered to the hydrosphere from hospital wastewaters in Germany. Therefore, Gd from volcanic source could represent a potential environmental risk under particular conditions.

Major volatiles play an important role in subduction zone magmatism, from magma generation in the mantle, to crustal ascent and evolution, until its dramatic expression during a volcanic eruption. In the attempt to add a piece of information on source and behavior of major volatiles in arc volcanism, I here report on the geochemistry of H2O, CO2, S and Cl in two volcanic systems in NW Nicaragua (Central America), San Cristóbal and Telica. The observational approach is based upon combination of some of the most recent techniques in volcanic gas monitoring and petrology. I here explore quiescent and eruptive degassing processes by combining both volcanic gas and melt inclusion approaches. Field gas measurements were primarily obtained via the Multi-Component Gas Analyzer system (Multi- GAS) technique, complemented with additional remote sensing observations via open-path Fourier Transform IR (OP-FTIR) spectroscopy, ultraviolet differential optical absorption spectroscopy (UV-DOAS). These techniques together allowed characterizing compositions and fluxes of CO2, H2O, S and Cl in the central crater plumes of both quiescent degassing volcanoes. These measurements contribute to our understanding of the current structure and state of the shallow plumbing systems that feed the surface gas emissions. The targeted San Cristóbal and Telica volcanoes are also investigated by characterizing, for the first time, the volatiles contents (CO2, H2O, S and Cl, F) in their melt inclusions. Using a series of laboratory instrumental facilities, such as electron microprobe, micro FTIR spectroscopy, Raman spectroscopy and Nano secondary ions mass spectroscopy (NanoSIMS), I show that olivine- and pyroxene-hosted melt inclusions can reveal crucial information on preeruptive magma conditions at both San Cristóbal and Telica. I propose that polybaric degassing and crystallization models can suitably describe major volatile abundance and behavior during magmatic evolution. These results are synthesized in 3D illustrative sketches that represent the crustal structure of San Cristóbal and Telica volcano-magmatic systems. Water is the primary agent during magmatic fragmentation and strongly influences eruptive style. CO2, the second most abundant volatile in magmas, is generally more difficult to quantify in melt inclusion studies, but its role in volcanic processes is revealing more and more important as volcanological research advances. I therefore spend major attention in this study to charactering the carbon content in San Cristóbal and Telica primitive magmas. CO2, apart from being an excellent chemical tracer of magmatic degassing processes, is one of the most important triggers of explosive eruptions in basic to intermediate magmas. The volatile contents of Central American magmas show wide regional-scale variations. It is shown here that gas signature (carbon abundance) of Central American volcanic gases correlates with petrological tracers of magma compositions, and specifically with the trace element proxies of slab-fluid contribution to the mantle wedge. This brings novel constraints on carbon source in volcanic arc regions. I also show, using noble gas isotope compositions of fluid inclusions in olivine-pyroxene crystals, that a common mantle fluid signature persists along the entire Nicaragua volcanic segment. Controls on magma generation are, instead, better reconstructed using incompatible trace elements; these data reveal that the degree of mantle melting and sedimentary fluid incorporation are higher in Nicaragua than in other sectors of the arc. We find that local variations exist also at the scale of a single magma system. These variations, at different spatial and temporal timescales, prove that regional compositional heterogeneities exist underneath volcanic arcs.

Lo studio sedimentologico e stratigrafico di alcune sezioni del Triassico Superiore-Giurassico Inferiore del dominio Panormide (Sicilia), ha contribuito all’elaborazione di un dataset che consente di avanzare nuove considerazioni sulla complessa evoluzione di questo dominio paleogeografico in prossimità del limite T/J. Sono stati studiati in dettaglio tre principali settori lungo la porzione nord-occidentale della Sicilia, dai Monti di San Vito alle Madonie, attraverso i Monti di Palermo. Nel settore più occidentale presso Monte Sparagio (penisola di Capo San Vito), l’analisi delle microfacies ha consentito di posizionare il limite T/J all’interno di una spessa successione di cicli peritidali del Triassico Superiore-Giurassico Inferiore, sulla base della scomparsa di Triasina hantkeni e della comparsa di associazioni oligotipiche a Thaumapoporella parvovesiculifera e Aeolisaccus. Il passaggio appare continuo, non si evidenziano infatti discontinuità legate alla tettonica o alle variazioni del livello del mare. Evidenze di un abbassamento del livello del mare lungo questa sezione, sono state riconosciute ben al di sotto del limite T/J, all’interno della biozona a Triasina del Retico. Questo evento è evidenziato dalla presenza di uno spesso paleosuolo che ricopre una superfice carsificata correlabile lateralmente con una struttura interpretabile come una paleodolina. Inoltre, al sotto di questa superfice, si sviluppa un ampio sistema di grandi cavità paleocarsiche. Le cavità sono colmate da brecce da collasso formando, in alcuni casi, delle strutture tipo “breccia pipes”. Gli elementi della breccia derivano dall’host rock peritidale e sono circondate da una matrice siltosa policroma che rende questa breccia di particolare interesse ornamentale. L’emersione stimata della piattaforma è di circa 130 m, un valore che difficilmente può essere spiegato in termini di una variazione eustatica se si considera che il valore stimato da Hallam (2001) per la variazione Retica del l.m. è di circa 50 m. E’ quindi da considerare una possibile componente tettonica connessa al contemporaneo rifting della adiacente Tetide Alpina. I cicli triassici presenti in quest’area mostrano estesi fenomeni di dissoluzione stratale che chiaramente predatano la porosità “cavernus” come indicato dalla presenza, fra le brecce da collasso, di clasti derivanti da questi orizzonti. Tre diversi tipi di dissoluzione stratale sono stati riconosciuti: vug, biomoldic e “spongy-like”. Lo studio di questo tipo di dissoluzione risulta di particolare interesse per la formazione di porosità secondaria nei reservoirs carbonatici ed ha quindi costituito uno degli argomenti più approfonditi nello studio di dottorato. La comparazione morfologica delle cavità spony-like con simili strutture da dissoluzione presenti nelle piattaforme carbonatiche attuali, insieme ai dati geochimici, supporta l’influenza di una lente di acque di mixing per la formazione sia delle cavità spongy che della porosità vug e biomoldic. Il modello messo a punto implica la presenza di un apporto di acque dolci e di un’interazione tra le variazioni ad alta frequenza del livello del mare, responsabili della ciclicità peritidale e la tessitura delle facies subtidali. Durante le fasi di lowstand (con la conseguente formazione dei paleosuoli) un apporto di acque dolci, da una terra emersa vicina o dalle precipitazioni, interagisce con la lente freatica marina creando una lente di acque di mixing che staziona nei membri subtidali dei cicli. Il forte controllo tessiturale, dettato dalla bioturbazione, dal contenuto fossilifero o dall’assenza di entrambi, nelle facies subtidali risulta fondamentale nella determinazione della porosità risultante. In altre parole, quando la lente di mixing staziona in corrispondenza delle facies bioturbate, nelle quali si è creata una disomogeneità tessiturale fra sedimento originario e il riempimento delle cavità da bioturbazione, la dissoluzione risultante assume l’aspetto del pattern spongy. Nel caso della presenza di abbondanti gusci di bivalvi, la dissoluzione ad opera di acque di mixing crea una porosità di tipo biomoldic, mentre in assenza di un controllo tessiturale si sviluppa una porosità vug. Nelle aree di studio adiacenti (Monti di Palermo e Madonie) il limite tra i terreni triassici e giurassici è discontinuo. I depositi di scogliera del Norico-Retico presentano alcune cavità colmate da silt meteorici di età retica che indicano una breve fase di esposizione del margine di piattaforma seguita da un successivo annegamento. L’intensa frammentazione tettonica dimostrata da altri autori nel settore di Billiemi durante l’Hettangiano è responsabile della conversione del margine della piattaforma a scarpata. Si determina in questo modo una superfice di discontinuità che mette a contatto i depositi di scogliera con lembi discontinui di calcari bioclastici a brachiopodi del Pliensbachiano e/o con depositi pelagici ad ammoniti del Toarciano. La presenza di grandi volumi di depositi di scarpata dolomitizzati (Fm. Fanusi e Quacella Auct., nell’adiacente bacino Imerese, è qui interpretata come il risultato di ripetuti crolli da una scarpata a controllo tettonico impostatasi lungo il margine della piattaforma durante l’Hettangiano ed il Sinemuriano Questa ipotesi è anche supportata dalla presenza di sedimenti di differente facies ed età (tuttavia sempre del Giurassico Inferiore) che drappeggiano la scogliera come depositi di episcarpata. The stratigraphical and sedimentological study of uppermost Triassic-lowermost Jurassic sections belonging to the Panormide platform in Sicily, has provided an original dataset that allow to put forward some new considerations on the complex evolution of this paleogeographic domain across the T/J boundary. Three main sectors have been investigated in detail along a northern Sicily W-E transect from the San Vito Lo Capo Peninsula, via the Palermo Mountains, to the Madonie Mountains. In the westernmost sector, at Monte Sparagio (San Vito Lo Capo Peninsula), the microfacies analysis has allowed to place the T/J boundary across a thick undifferentiated succession made of Upper Triassic-Lower Jurassic peritidal cycles, on the base of the last occurrence of Triasina hantkeni and the appearance of oligotypic facies with Thaumatoporella parvovesiculifera and Aeolisaccus. The transition appears fully conformable without any record of possible variations of the sedimentary regime (e.g. sea level fall, tectonic deformations) besides the faunal turnover. In this section evidence of a sea-level lowering are recognized well below the T/J boundary, roughly in the middle part of the Triasina zone, thus of the Rhaetian. This event is suggested by the presence of a particularly thick red paleosol that covers a karstified surface, laterally correlated with a structure that is interpreted as a paleosinkhole. Moreover an huge system of paleokarstic caves develops downward from this surface. The caves are filled up by collapsed breccias to form, in some parts “breccia pipes”. The breccia elements clearly derive from the peritidal host rock and are surrounded by polychrome silty matrices that rendered this breccia of great interest for ornamental purposes. The uplift of the platform can be estimated at about 130 m, a value that is difficult to explain only in terms of eustatic variation if we consider the estimated values (about 50 m) provided by Hallam (2001). So a tectonic forcing has to be considered possibly induced by the adjacent rifting of the Alpine Tethys. The Triassic cycles in this area show extensive phenomena of stratabound dissolution that clearly predate the cavern dissolution as indicated by the involvement of the latter in the collapse breccias that fills the paleocaves. Three main types of stratabound dissolution have been recognized: vug, moldic and “spongy-like”. The study of this type of dissolution is of particular interest for the diagenetic formation of the secondary porosity in carbonate reservoirs so it has been one of the main topic of the PhD. The morphological comparisons of the spongy-like cavities with recent similar dissolution patterns in modern carbonate platforms, coupled to the geochemical data, supports the influence of a mixing water lens for the formation of the spongy-like cavities but also for the vug and moldic stratabound porosity. The model put forward implies the presence of a fresh water supply in the area and an interaction between the high-frequency and low-amplitude sea-level fluctuations, responsible of the peritidal ciclicity, and the textural patterns of the subtidal facies. During the lowstand phases (and the subsequent formation of the Terra Rossa paleosols) a fresh-water supply, provided by adjacent exposed lands and/or by rainwaters, interacts with the phreatic marine lens giving rise to a thin mixing water lens floating on the phreatic marine zone and stationing in the subtidal member of the cycle. The strong textural control exerted by the bioturbation, by the fossil content or by the absence of both in a specific subtidal member is fundamental in determining the resulting solution patterns. In other words, when the mixing zone was stationed on the bioturbated mud, where a differential porosity and permeability existed, than dissolution preferentially assumed the spongy shape. In the presence of abundant mollusc shells, the dissolution operated by the mixing waters preferentially created biomoldic porosity, whilst without a strong macrotextural control a vuggy porosity could develop. In the adjacent study areas (Palermo and Madonie Mountains) the boundary between Triassic and Jurassic sediments is discontinuous. A drowning unconformity characterizes the marginal sector of the platform in which the reef complex is overlain by Pliensbachian pelagic limestones belonging to the “Rosso Ammonitico”. These data are indicative of a short subaerial exposure of the platform, during Rhaetian, and of a tectonic activity, along the platform margin, during Hettangian-Sinemurian times. These type of deformations are related to the rifting stages in the adjacent Alpine Tethys. The presence of a huge volume of slope dolomitized deposits (Fanusi and Quacella Formations Auct.), in the adjacent Imerese Basin account for a conversion of the reef complex, edging the platform, to a slope zone repeatedly affected by submarine collapses. This is also supported by the presence of sediment pockets (patches) of different facies and ages (however Early Jurassic) that drapes the reefs as epi-escarpment deposits.

This PhD thesis concerns the geochemistry of Zr, Hf and REE in extreme water environments characterized by a wide spectrum of chemical physical-parameters and compositions. The investigations were carried out in hypersaline waters covering a wide range of Eh values along Dead Sea Fault (Israel), in hyperacid waters circulating in Nevado del Ruiz volcano-hydrothermal system (Colombia) and in CO2-rich waters belonging to the Pantelleria volcano-hydrothermal system (Italy), including the alkaline lake “Specchio di Venere” formed within a calderic depression. The wide spectrum of chemical-physical conditions and various water chemical compositions interacting with different solid phases allowed to depict a scenario where Zr, Hf and REE are ruled by different processes, filling the still missing geochemical aspects. The important role of the pH (from 1 to 8.8) and the water chemical composition in regard to the distribution of Zr, Hf and REE was mainly investigated in the Nevado del Ruiz volcano-hydrothermal system. The pH rules the precipitation of authigenic Fe-, Al-oxyhydroxides producing changes in Zr, Hf and REE abundances and strong cerium anomaly. Significant LREE (Light Rare Earth elements) depletion was found in acidic sulphate waters, where the formation of alunite and jarosite was recognized. Sub-chondritic Zr/Hf ratios (lower than magmatic local rocks) and chondritic Y/Ho ratios (close to the local magmatic rocks) are shown in acidic sulphate waters (1