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The sustained and uninterrupted plume degassing at Mount Etna volcano, Southern Italy, represents the troposphere's most prominent natural source of fluorine. Of the ∼ 200 Mg of fluorine (as HFg) emitted daily by the volcano, 1.6 ± 2.7 Mg are deposited by wet and dry deposition. Fluorine-deposition via volcanic ash, here characterised for the first time, can be quite significant during volcanic eruptions (i.e. 60 Mg of fluorine were deposited during the 2001 eruption through volcanic ash, corresponding to ∼ 85% of the total fluorine deposition). Despite the fact that these depositions are huge, the fate of the deposited fluorine and its impact on the environment are poorly understood. We herein present original data on fluorine abundance in vegetation (Castanea Sativa and Pinus Nigra) and andosoils from the volcano's flank, in the attempt to reveal the potential impact of volcanogenic fluorine emissions. Fluorine contents in chestnut leaves and pine needles are in the range 1.8–35 μg/g and 2.1–74 μg/g respectively; they exceed the typical background concentrations in plants growing in rural areas, but fall within the lower range of typical concentrations in plants growing near high fluorine anthropogenic emission sources. The rare plume fumigations on the lower flanks of Mt Etna (distance > 4 km from summit craters) are probably the cause of the “undisturbed” nature of Etnean vegetation: climatic conditions, which limit the growth of vegetation on the upper regione deserta, are a natural limit to the development of more severe impacts. High fluorine contents, associated with visible symptoms, were only measured in pine needles at three sites, located near recently-active (2001 to 2003) lateral eruptive fractures. Total fluorine contents (FTOT) in the Etnean soils have a range of 112–341 μg/g, and fall within the typical range of undisturbed soils; fluorine extracted with distilled water (FH2O) have a range of 5.1 to 61 μg/g and accounts for 2–40% of FTOT. FH2O is higher in topsoils from the eastern flank (downwind), while it decreases with depth in soil profiles and on increasing soil grain size (thereby testifying to its association with clay–mineral-rich, fine soil fractions). The fluorine adsorption capacity of the andosoils acts as a natural barrier that protects the groundwater system.

A limnological investigation was carried out on the small, endorheic lake, called Lake Sfondato, located in central Sicily (Italy). All the aquatic environments in the central part of the island are rich in salt, with conductivity values above 5 mS cm−1, and are characterized by high alkalinity values and hard waters. In addition, due to intensive agriculture, many of these ecosystems have experienced a strong anthropogenic eutrophication over the last decades. In order to better understand the functioning of these peculiar environments, the morphology, hydrology, and geochemistry, as well as several selected physical and biological characteristics of Lake Sfondato, were studied in the years 2003 and 2004. The results showed that the water body is characterized by meromixis, with permanent water stratification. This condition reduces the eutrophication processes within the lake, which have kept the trophic conditions constant over the last 50 yr.

Gli autori riferiscono sui tipi e sui modelli di genesi dei carbonati dei suoli, attraverso l’uso degli isotopi del 13C. Lo studio è stato condotto in un’area dell’interno collinare argilloso siciliano, su suoli che evolvono sui depositi evaporitici della Serie Gessoso-Solfifera. Sono stati scelti cinque pedon su litotipi calcarei e non. I pedon sono stati descritti in campo e campionati secondo la sequenza degli orizzonti genetici; sui campioni di suolo sono state eseguite le seguenti analisi: tessitura, reazione, conducibilità elettrica, gesso, carbonio organico ed inorganico. Inoltre, parallelamente sono state eseguite le analisi isotopiche del carbonio organico ed inorganico. I risultati hanno consentito di individuare, oltre che le complesse relazioni esistenti tra la componente abiotica e biotica del suolo, anche i modelli di genesi dell’orizzonte calcico e quindi le relative implicazioni sulla classificazione dei pedon investigati.

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.

Dry and wet depositions provide the pathways through which particles and gases emitted into the atmosphere return to the Earth’s surface. Bulk deposition is defined as the sum of dry and wet deposition, which is characterized by water-soluble and insoluble chemical species. Recent studies (e.g. Castillo et al., 2017) showed that most of the atmospheric deposition in Europe occurs in the wet form, but in southern European regions the role of dry contribution can be as significant as that of wet deposition. In the framework of the multidisciplinary project “CISAS” (Centro Internazionale di Studi Avanzati su Ambiente, ecosistema e Salute umana), bulk depositions were monthly sampled over two polluted industrial areas of Sicily (Milazzo and Priolo), through a network of 12 bulk collectors, from June 2018 to July 2019. In that period, 137 samples were collected and subdivided into 4 aliquots for different analytical determinations: (i) unfiltered aliquots for the total alkalinity; (ii) filtered aliquots (0.45 µm filters) for major anions by ionic chromatography (IC); (iii) filtered and acidified (with Ultrapure HNO3) for the analysis of major cations and a large suite of trace elements, respectively by ICP-OES and ICP-MS; (iv) unfiltered and acidified aliquots for the same suite of trace elements, to evaluate the contribution of less-soluble species. The filtration of the rain samples allows the separation of the water-soluble fraction from the particulate fraction (> 0.45 µm), which is retained by the filter. The comparison between filtered and unfiltered aliquots allowed to highlight the different geochemical mobility of the trace elements, and their distribution among the two fractions. The unfiltered aliquots, therefore, represent the less-soluble species found in the particulate under typical rainwater pH values (4 – 8), that becomes soluble due to the acidification of the samples (pH < 1). Results showed that the less-soluble fraction represents a significant part of the bulk deposition for several trace metals, especially during dry-dominated periods which are characterized by a long-range transport of geogenic particles (e.g. desert dust). In particular, Al, B, Ba, Fe, Li, Sr, and Ti showed significant enrichment if the less-soluble fraction is included. Similar enrichments are noteworthy also for As, Cr, Co, Cu, Ni, Pb, Se Tl, Te and V which can be attributed to the local industrial atmospheric pollution, as well as to Mt. Etna that is a permanent source of several volcanogenic elements (Brugnone et al., 2020).

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