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scientific articles, several historical maps and photos of Vulcano and Solfatara, manuscript notes and three important unpublished researches about Vulcano, Vesuvio and Campi Flegrei.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

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

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

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

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

Mt. Etna, in eastern coast of Sicily (Italy), is one of the most active and most intensely monitored volcanoes of the planet. It is the biggest volcanic point source of volcanic gases and particles to the troposphere in the Mediterranean basin. On the morning of December 24th 2018, a new lateral eruption of the Mount Etna started. This eruption was related to an intrusion of a magmatic dike on the high eastern flank of the volcano, which a two kilometers long fracture in the NNW - SSE direction. At the same time, the summit craters also produced a continuous strombolian activity generating a very dense dark ash plume, dispersed by the wind into the southeastern direction. This volcanic event well record from the atmospheric precipitations. During the period from June 2018 to May 2019, atmospheric precipitations were collected in the area of Priolo, eighty kilometer far SSE from Mt. Etna. The sampling and analytical protocols were chosen following the guidelines published by the main international agency involved in the monitoring of atmospheric precipitation. The rain gauges were open during the entire exposure time, collecting 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. The atmospheric precipitation of the period straddling the eruptive event is characterized by high concentration of major ions, such as Fluoride (up to 0.88 mg/l), Chloride (up to 124 mg/l) and Sulphate (23.1 mg/l). These derive mainly from the emitted volcanic gases (HF, HCl and SO2). On the another hand, an enrichment of some trace elements is also presented, such as Aluminum (up to 152 μg/l), Thallium (0.16 μg/l), Tellurium (0.025 μg/l). While Tl and Te are highly volatile elements typically enriched in volcanic emissions, Al is a refractory element that is probably correlated to the dissolution of the emitted volcanic ashes.

The Hellenic territory has a very complex geodynamic setting from a long and composite geological history, giving rise to an intense seismic activity deriving and favoring the occurrence of many cold and thermal gas manifestations. Geogenic sources release huge amounts of gases, which have a significant impact on the global balance of the subaerial Carbon Cycle. The study of the geochemistry of the natural gas emissions of the Greek territory is actually underway. In the present work, we focus on methane and light hydrocarbons (C2-C6) to define their origin. Concentrations of methane range from < 2 to 915,200 mmol/mol and its isotopic ratios cover a wide range (d13C from -79.8‰ to +16.9‰; dD from -298‰ to +264‰) indicating different origins or secondary post-genetic processes. Samples from gas discharged located in the Ionian coast and northern Aegean Sea have a prevailing microbial origin, as also shown by the lack of C4+ hydrocarbons and the high C1/(C2+C3) ratios. On the contrary, cold and thermal gas manifestations of central and northern Greece display a prevalent thermogenic origin. Methane in gases released along the active volcanic arc seems to be abiogenic in origin, since they show low C1/(C2+C3) ratios, as well as relatively high C6H6 concentrations. However in these gases, significant thermogenic contribution cannot be excluded. Gases collected in the geothermal areas of central Greece (Sperchios basin and northern Euboea) are likely affected by strong secondary oxidation processes, as suggested by their highly positive C and H isotopic values (up to +16.9‰ and +264‰ respectively) and low C1/(C2+C3) ratios. Incubation experiments on water and sediments of some of these springs reveal that the oxidation of methane is microbially driven.

Il mercurio (Ilg) è uno dei principali inquinanti emessi in atmosfera. La sua complessità geochimica, unitamente alla tossicità c agli effetti persistenti della sua presenza nell’ecosistema terrestre, lo hanno inserito nella lista delle priorità di un numero sempre crescente di accordi internazionali rivolti alla tutela ambientale e della stiline umana (The Arctic- Monitoring and Assessment Program, AMAR, United Nations - Economie Commission for Europe: Ileavy Metals Protocol, UN- ECE, The Helsinki Commission, IIELCOM, la convenzione OSPAR). I progressi raggiunti neH’ullimo decennio sullo studio del Hg come ‘global poi Intani '(Pirrone et al.. 2001; Hedgecock et al, 2000: Paeyna et al, 2006; Bullock and Jacgle, 2000; Dastoor e Davignon, 2009; Eriedli et al., 2(X)!); .Jaegle et al, 2009; Jung et al. 2009; Seigneur et al, 2009; Travnikov and Ilyin, 2009) hanno contribuito a fornire una valutazione aggiornata delle emissioni di Hg a scala globale provenienti sia da fonti antropogeniche che naturali. A oggi, le sorgenti antropiche sono responsabili di circa il 30% delle emissioni annue di mercurio in atmosfera. Un altro 10% proviene da fonti geologiche naturali, mentre il restante 60% dalla “ri-emissione” di mercurio precedentemente depositatosi nell’ecosistema terrestre (Kocman et al., 2013). E’stato stimato che circa 5207 t di Hg vengono emesse annualmente da parte dei processi naturali (emissioni primarie di mercurio + ri-emissioni). Nel complesso, di queste 5207 t anno1, circa 2429 t anno1 di Ilg vengono emessi dalle superfici terrest ri (47% del totale delle emissioni naturali di Hg), mentre l’evasione oceanica contribuisce con un flusso di - 2778 anno1 (Pirrone et al. 2010). Per mitigare il rischio associato a tali emissioni è necessario conoscere a fondo le dinamiche che regolano lo scambio di Hg tra la sorgente e il recettore. In che misura è possibile quindi prevedere la futura evoluzione del Ilg rilasciato in atmosfera?

Le interazioni del Hg con l'ambiente costituiscono il ciclo geochimico di questo elemento che si esplica per mezzo di complessi processi fisico-chimici differenti per ciascun comparto geochimico. Si stima che circa i due terzi del mercurio presente in ambiente sia stato prodotto durante il ventesimo secolo, e che il carico di mercurio immesso attualmente sia aumentato di circa 3 volte rispetto agli inizi del 1900 (Mason et al.. 1994). Il comparto ambientale certamente più coinvolto dalle emissioni di mercurio è quello atmosferico, da cui poi l’elemento si diffonde anche negli altri comparti, suolo e sedimenti compresi (Filzgerald & Clarkson, 1991). L’Atmosfera costituisce un importante reservoir temporaneo di mercurio. Infatti, i processi chimici che avvengono in atmosfera trasformano il mercurio dallo stato elementare allo stato bivalente, influenzandone cosi le modalità di trasporto e la velocità di deposizione di questo metallo sulla superficie terrestre. Il mercurio è rilasciato in atmosfera da una varietà di sorgenti naturali (Siegei e Siegei, 1983; Filzgerald, 1986; Xiao et al., 1991; Mason et al.. 1994; Lindberg et al., 1995) ed antropogeniche (Lindqvist et al., 1991; Ferrara et al., 1992; Pirrone et al., 2010; Carpi e Lindberg, 1997; Lacerda, 1997). Le sorgenti naturali includono i vulcani, i suoli, le foreste, i laghi, gli oceani apert i per un i nput totale di circa 2000 lon/anno (Mason et al., 1994); le sorgenti antropogeniche sono principalmente legate alla produzione energetica mediante l’utilizzo di carboni fossili, la combustione e l'incenerimento dei rifiuti, e ad alcuni processi industriali- metallurgici, determinando un flusso totale di circa 4000 lon/anno (Forcella et al., 1997). Il trend delle emissioni di mercurio antropogenico su scala globale è in crescila, soprattutto a causa delle emissioni dai Paesi in forte via di sviluppo (es., Cina, India).

Volcanic/geothermal areas are sites of complex interactions between geosphere and biosphere. Pantelleria island (Southern Mediterranean Sea) hosts a high enthalpy geothermal system characterized by high CH4 and low H2S fluxes. Two sites, FAV1 and FAV2, located a few meters apart at the main exhalative area of the island (Favara Grande), recorded similar physical conditions (soil temperature 60°C, soil gas composition enriched in CH4, H2 and CO2). However, while high methanotrophic activity (59.2 nmol g-1 h-1) and high diversity of methanotrophs was detected at FAV2, FAV1 was not active and appeared deprived of methanotrophs (1). Our aim was to investigate the main factors influencing methanotrophy as a result of biotic and abiotic interactions in this geothermal site. To this aim, soil bacterial and archaeal communities of the two sites were analysed by 16S rDNA MiSeq Illumina sequencing and the results related to geochemical data. At phylum level, both FAV1 and FAV2 bacterial sequences were mainly assigned to four phyla (Proteobacteria, Firmicutes, Actinobacteria and Chloroflexi) being Chloroflexi much more represented at FAV1 and Actinobacteria at FAV2. High abundance of thermo-acidophilic chemolithotrophs was detected in site FAV1, while FAV2 was dominated by methanotrophs (40% of the reads). The most represented species at FAV1 was Acidithiobacillus ferrooxidans (25%), while methanotrophs at FAV2 were dominated by Methylocaldum (31%). Archaea were almost exclusively represented, at both sites, by the chemolithotrophic ammonia-oxidating candidate species Nitrososphaera gargensis (Thaumarchaeota). Our results suggest that methanotrophs are not hampered at FAV1 by harsher conditions but by a previously unrecognized competition between chemolithotrophy and methanotrophy due to energetic convenience for chemolithotrophic lifestyle derived from higher availability of electron donors (NH4+, H2). (1) Gagliano et al., 2014 Biogeosciences, 11, 5865–5875

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.

Like other geodynamically active areas, Greece is affected by a large number of geogenic gas manifestations. These occur either in form of point sources (fumaroles, mofettes, bubbling gases) or as diffuse emanations. We produced a first catalogue of the geogenic gas manifestations of Greece also considering few literature data. Collected samples were analysed for their chemical (He, Ne, Ar, O2, N2, H2, H2S, CO, CH4 and CO2) and isotopic composition (He, C and N). Most of the sampled gas manifestation are found along the South Aegean active volcanic arc (32 sites) and in the majority they belong to the CO2 dominated group. Very few gas manifestations, N2- or CH4- dominated, are found along the most external units of the Hellenides orogen (Apulia domain - W and SW Greece), where generally compressive or transpersive tectonic prevails. On the contrary, gas manifestations (mainly CO2- dominated) are widespread along northern Greece (28 sites) and along Sperchios basin - north Evia graben (12 sites) which are characterised by extensional tectonic. Geogenic gases, apart from having important influences on the global climate, could have strong impact on human health. Gas hazard is often disregarded because fatal episodes are often not correctly attributed. Geodynamic active areas release geogenic gases for million years over wide areas and the potential risks should not be disregarded. A preliminary estimation of the gas hazard has been made for the last 20 years considering the whole population of Greece. In this period at least 2 fatal episodes with a total of 3 victims could be certainly attributed to CO2. This would give a risk of 1.3·10-8 fatality per annum. Such value, probably underestimated, is much lower than most other natural or anthropogenic risks. Nevertheless this risk, being unevenly distributed along the whole territory, should not be overlooked and better constrained in areas with high density of gas manifestations and high soil gas fluxes.

In the winter 2013, mercury concentrations in air from the mine-polluted area of Mt. Amiata (1738 m a.s.l.), in southern Tuscany (Central Italy), were measured by active moss biomonitoring. This area is part of the geologic anomaly of Hg in the Mediterranean basin, which contains about 65 % of the world’s cinnabar (HgS). Mt. Amiata covers some 400 km2 and is drained by several rivers. Esploitation activity at Abbadia S. Salvatore, in the SE sector of the mountain, sprang up during the 19th century as one of the largest mercury mining and smelting plants in Europe, after those of Almaden Spain. In this area, Sphagnum moss bags were exposed for about two months, from October to December 2013. At each site (10 sites), one covered and one uncovered moss bag were deployed. Concentrations of mercury in air were also investigated in the same sites with a portable spectrophotometer (Lumex RA-915M). After exposure, mosses were oven-dried, grinded and each sample was divided in two aliquots: one was analyzed for mercury by using a Hydra C cold vapor atomic absorption analyzer (INGV-Palermo), following 7473 US EPA method; the second was microwave digested in acid solution (HNO3 + H2O2). Extraction solutions were analyzed by ICP-MS for total concentrations of a large suite of trace elements, including potentially toxic elements e.g. As, Cd, Cr, Cu, Mo, Sb, Se, V. Mercury air concentrations measured with the Lumex showed extremely high values in the mine district of Abbadia, with median values ranging from 2,000 to 4,000 ng/m3 and maximum values up to 20,000 ng/m3, in contrast with the lower values (median values from 20 to 200 ng/m3) measured in the distal sites few kilometres from the mine-district area. In agreement with these results, in the vicinity of the district uncovered bags were in the range of 10,000 – 100,000 ng/g of Hg, whereas in the distal sites they were in the range of 1,000 – 10,000 ng/g. The moss-blank (unexposed moss) was ~100 ng/g. Covered moss bags were not significantly enriched in Hg with respect to the concentrations recovered from the moss-blank, suggesting that the mercury trapped in the mosses was mainly in particulate form. The particles carried from the winds were probably associated with soils re-mobilization, as also confirmed by the associated enrichments of some lithophile elements (Li and lanthanides) and anthropogenic element (As, Cr, Cd, Fe, Se, V). These preliminary results confirm the intense contamination of the study area not only for mercury but also for other potentially toxic elements.

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. 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