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We have analyzed the carbon isotopic composition of CO 2 , methane, ethane, propane and n-butane, the hydrogen isotopic composition of methane as well as total concentrations of gas constituents contained in the Mediterranean volcanic–hydrothermal discharges of Nisyros (Greece), Vesuvio, La Solfatara, Ischia and Pantelleria (all Italy) to determine the origin of the hydrocarbons. Isotopic criteria conventionally used for hydrocarbon classification suggest thermogenic origins, except for Pantelleria, for which an abiogenic origin is indicated. These findings would imply that thermogenic sources can provide methane/(ethane + propane) concentration ratios as high as those usually observed for microbial hydrocarbons. However, additional consideration of gas concentration data challenges the suitability of conventional criteria for the classification of hydrocarbons emanating from hydrothermal environments. Methane seems to be in close equilibrium with co-occurring CO 2 , whereas its higher chain homologues are not. Therefore, it cannot be excluded that methane on the one hand and ethane, propane and n-butane on the other hand have distinct origins. The carbon isotopic composition of methane might be controlled by the carbon isotopic composition of co-occurring inorganic CO 2 and by hydrothermal temperatures whereas the carbon isotopic composition of the higher n-alkanes could correspond to the maturity of organic matter and/or to the residence time of the gasses in the source system.

International audience; Along the Jordan Valley-Dead Sea Fault area several natural waters in springs, wells, and catchments occur. The chemical-physical characters of the studied waters allowed for the first time the investigation of the Zr and Hf geochemical behavior, apart from REE, extended to a wide range of Eh, temperature, salinity, and pH conditions. The results of this study indicate that the dissolved Zr and Hf distribution in natural waters is strongly influenced by redox conditions since these in turn drive the deposition of Fe-oxyhydroxides or pyrite. In oxidizing waters saturated or oversaturated in Fe-oxyhydroxides (Group 1), superchondritic Zr/Hf values are measured. On the contrary, in waters where Eh < 0 values occur (Group 2), chondritic Zr/Hf values are found. Superchondritic Zr/Hf values are produced by the preferential Hf scavenging onto Fe-oxyhydroxides that is inhibited under reducing conditions consistent with the water oversaturation relative to pyrite. Redox conditions also influence the amplitude of Ce and Eu anomalies. Oxidized Group-1 waters show negative Ce anomalies related to the oxidative Ce scavenging as CeO2 onto Fe-oxyhydroxide. Reduced Group-2 waters show positive Eu anomaly values consistent with the larger Eu2+ concentration relative to Eu3+ in these waters suggested by model calculations. The higher stability of Eu2+ with respect to its trivalent neighbors along the REE series can explain the above mentioned positive Eu anomaly values. The middle-REE enrichment observed in shale-normalized REE patterns of studied waters can be ascribed to carbonate and/or gypsum dissolution.

Nisyros is the easternmost island of the South Aegean Active Volcanic arc in Greece. It is an active stratovolcano known for its intense hydrothermal activity. In this study we present the results of the mineralogical analyses of 20 soil samples collected in the caldera area. Samples were analysed through X-ray diffraction and the results allow us to divide them in two groups: Lakki Plain and Stefanos Crater. In their majority the soils of Lakki Plain have a main mineralogical assemblage that consists of quartz, feldspar and gismondine (Ca2Al4Si4O16·9H2O). Gismondine as well as stellerite (CaAl2Si7O18·7H2O), which is appearing in some samples, derive from hydrothermal alteration, whilst wollastonite (CaSiO3) is also found as a product of thermally metamorphosed siliceous carbonates. In the Stefanos Crater soils, due to the acid environment and the relatively high temperatures of the fumaroles (about 100°C), the main assemblages mostly comprises hydrothermal alteration minerals like quartz, sulfur, wollastonite, gypsum and gismondine. The lower amount of feldspars with respect to the Lakki Plain soils can be justified by the high percentage of gismondine, their alteration products. Voltaite (K2Fe(II)5Fe(III)3Al(SO4)12·18H2O) was also found in some of the samples as a product of hydrothermal alteration of Si deposits. Close to the fumaroles, the occurrence of alunogen (Al2(SO4)3·17H2O), a sulphide alteration mineral found in fumarolic environments, is also noticeable.

The geologic emissions of greenhouse gases (CO2 and CH4) give an important natural contribution to the global carbon budget. However, the contribution of these emissions to the global carbon cycle and their possible role on the climate change remain still poorly quantified (Guliyev and Feizullayev, 1997; Milkov, 2000; Etiope et al., 2015 and references therein). Methane, the most abundant organic compound in Earth's atmosphere, may be created either from existing organic matter or synthesized from inorganic molecules. Accordingly, it can be differentiated in two main classes: a) biotic (either microbial or thermogenic) and b) abiotic. For this study, 115 gas samples of fumarolic, thermal and cold discharges from all over the Hellenic territory were collected and both chemical (CO2, H2S, CH4, N2, O2, Ar, H2 and light hydrocarbons) and isotopic (13C-CO2, 13C-CH4, D-CH4) analyses were performed, in order to investigate the genetic processes that produced CH4 in fluids related with the complex geodynamic setting of Greece. On the basis of the spatial distribution of the gas discharges and their type of emission, the whole dataset was subdivided into 3 main “domains”, as follows: 1) Volcanic Arc (VA) - 34 samples; 2) External Hellenides (EH) - 23 samples of cold emissions and of hyperalkaline aqueous solutions; 3) Internal Hellenides (IH) - 62 samples of cold and geothermal emissions. Almost each group is characterized, as long as subdivided in 3 groups based on the type of emission (on-land free or dissolved gases and subaqueous gases) and a 4th group includes literature data.

Several gas samples have been collected from natural gas manifestations at the island of Kos. Most of them are found underwater along the southern coast of the island. On land two anomalous degassing areas have been recognized. These are characterised by lack of vegetation and after long dry periods by the presence of sulfate salts efflorescences. Almost all the gases are CO2-dominated (CO2 ranging from 88 to 99%) with minor amounts of N2 (up to 7%) and CH4 (up to 2.6%). Only the on-land manifestations have also significant contents of H2 (up to 0.2%) and H2S (up to 0.3%). Only one underwater manifestation is N2-dominated (61-99%) with CH4 (0.6-11%) and low CO2 (0.1-26%). The isotopic composition of He shows values ranging from 0.84 to 6.72 R/RA indicating a sometimes strong mantle contribution with the highest values measured in two of the most strongly degassing areas (Paradise Beach and Volcania). C-isotopic composition of CO2 is in the range from -3.6 to 0.6 ‰ vs V.PDB with most of the values around -1‰ indicating a mixed mantle – limestones origin. Isotopic composition of CH4, ranging from -21.5 to 2.8‰ for C and from -143 to 36‰ for H, points to a geothermal origin with sometimes evident secondary oxidation processes. CO2-flux measurements showed values up to about 10,000 g/m2/day in the areas of Volcania and Kokkino Nero and up to about 50,000 g/m2/day at Paradise beach. Preliminary CO2 output estimations gave values of 8.8 and 4 tons/day for the first two areas and of 2.7 tons/day for the latter. The total output of the island (15.5 tons/day) should be considered a minimum estimation because of the incomplete coverage of the area and is comparable to the other active volcanic/geothermal systems of Greece (Nisyros, Nea Kameni and Methana).

The Greek territory belongs to the geodynamically active Alpine-Himalayan orogenic belt. As such, it shows intense seismic activity, active volcanic systems and areas of enhanced geothermal fluxes. One of these areas is the Sperchios basin and the northern part of Evia island in central Greece, which present widespread thermal manifestations (D’Alessandro et al., 2014). Five of them with temperatures from 33 to 80°C present bubbling gases whose dominating species are either CO2 or N2. All gases contain from 27 to 4000 ppm of CH4. The isotopic composition of CH4 in these gases covers a wide range with δ13C values ranging from -21.7 to +16.9 ‰ and δ2H values ranging from -124 to +301 ‰. The hottest manifestation displays the lowest isotopic values within the typical range of volcanic and geothermal systems. All the remaining samples fit a methane oxidation trend reaching very positive values. If we consider the lowest values as the deep hydrothermal marker the obtained ΔH/ΔC values range between 5 and 13 which are close to those typical of microbially driven oxidation (Kinnaman et al., 2007). Although the outlet temperature of the hottest manifestations is at the upper limit for methanotrophic microrganisms (Sharp et al., 2014), we can hypothesize that environmental conditions are not favorable for their survival at this site while they can thrive in the other, strongly consuming methane and producing very positive isotopic values. D’Alessandro, W., Brusca, L., Kyriakopoulos, K., Bellomo, S., Calabrese S. (2014): A geochemical traverse along the "Sperchios Basin-Evoikos Gulf" Graben (Central Greece): origin and evolution of the emitted fluids. Mar. Petrol. Geol., 55, 295-308. Kinnaman, F.S., Valentine, D.L., Tyler, P.A. (2007): Carbon and hydrogen isotope fractionation associated with the aerobic microbial oxidation of methane, ethane, propane and butane. Geochim. Cosmochim. Acta, 71, 271-283. Sharp, C.E., Smirnova, A.V., Graham, J.M., Stott, M.B., Khadka, R., Moore, T.R., Grasby, S.E., Strack, M., Dunfield, P.F. (2014): Distribution and diversity of Verrucomicrobia methanotrophs in geothermal and acidic environments. Environ. Microbiol., 16, 1867-1878.

The Greek territory belongs to the geodynamically active Alpine-Himalayan orogenic belt. As such, it shows intense seismic activity, active volcanic systems and areas of enhanced geothermal fluxes. One of these areas is the Sperchios basin and the northern part of Evia island in central Greece, which present widespread thermal manifestations [1]. Five of them with temperatures from 33 to 80°C present bubbling gases whose dominating species are either CO2 or N2. All gases contain from 27 to 4000 ppm of CH4. The isotopic composition of CH4 in these gases covers a wide range with δ13C values ranging from -21.7 to +16.9‰ and δ2H values ranging from -124 to +301‰. The hottest manifestation displays the lowest isotopic values within the typical range of volcanic and geothermal systems. All the remaining samples fit a methane oxidation trend reaching very positive values. If we consider the lowest values as the deep hydrothermal marker the obtained ΔH/ΔC values range between 5 and 13 which are close to those typical of microbially driven oxidation [2]. Although the outlet temperature of the hottest manifestations is at the upper limit for methanotrophic microrganisms [3], we can hypothesize that environmental conditions are not favorable for their survival at this site while they can thrive in the other strongly consuming methane and producing very positive isotopic values. [1] D’Alessandro et al. (2014), Mar. Petrol. Geol. 55, 295-308; [2] Kinnaman et al. (2007), Geochim. Cosmochim. Acta 71, 271-283; [3] Sharp et al. (2014), Environ. Microbiol. 16, 1867-1878

The geologic emissions of greenhouse gases (CO2 and CH4) have an important natural contribution in the global carbon budget. Tectonics, through faults in geothermal and oil producing areas, play a significant role in the release of C-gases in many non-volcanic regions of the Earth. Methane, the most abundant organic compound in Earth’s atmosphere, has a potential global warming that is 28 times higher than that of CO2 on a 100-year time horizon. In this study, δ13C-CH4, δ2H-CH4 and light hydrocarbon (alkane: CH4, C2H6, C3H8, C3H6, i-C4H10, n-C4H10; alkene C3H6, iC4H8; and aromatic C6H6) gas concentration data of 119 gas samples (103 unpublished data and 16 literature data) from volcanic-hydrothermal, geothermal and cold discharges are used to shed light on the genetic processes that have formed CH4 in the complex geodynamic setting of Greece. On the basis of the spatial distribution of the gas discharges and their type of emission, the whole dataset was subdivided into 4 main “domains”, as follows: 1) Volcanic Arc (VA); 2) External Hellenides (EH); 3) Internal Hellenides (IH); 4) Hellenic Hinterland (HH). Almost each group is characterized, as long as subdivided, in 3 groups based on the type of emission (on-land free or dissolved gases and submarine gases) and a 4th group includes literature data. Concentrations of CH4 range from < 2 to 925,200 µmol/mol and its isotopic ratios cover a wide range (δ13C from -79.8 ‰ to +45 ‰; δ2H from -311 ‰ to +301 ‰) indicating the different primary sources and the secondary post-genetic processes (oxidation) that can significantly affect the origin of this gas compound. Hydrocarbons in the CH4-dominated gases discharged from the EH are showing a clear biotic origin. In particular, those collected in the Gavrovo-Tripolis zone are showing a dominating biotic origin, whereas it is also noticeable that some gas samples of the Ionian zone are produced by both microbial activity and thermal maturation of sedimentary organic matter. The CO2-dominated gas discharges from the main geothermal systems of the IH and from the VA most likely predominantly contain abiogenic CH4 deriving from CO2 reduction. However, some of the gas discharges of the geothermal and volcanic-hydrothermal systems located in the neritic sedimentary Pelagonian, Gavrovo-Tripolis and Attico-cycladic zones (IH) and in Rhodope massif (HH), seem to exhibit significant contributions from thermogenic sources. The presence of abiotic methane was also recognized in the hyperalkaline aqueous solutions that are issuing from the ophiolites of Othrys and Argolida (Pindos zone (EH)). Most of the geothermal gases of Subpelagonian and Vardar/Axios zones (IH), the cold manifestations of the Rhodope massif (HH) and some of the volcanic-hydrothermal ones of the Attico-cycladic zone (VA) are presenting a microbial oxidation of CH4.

The Aegean area, which is geodynamically very active, is characterised by intense seismic activity, presence of active volcanic systems and anomalous geothermal gradients. Like other regions of intense geodynamic activity it is also characterized by extensive geogenic degassing. Gas manifestations are not only widespread on land but are also very frequent underwater. Many of these, as for example those of Milos and Santorini, are known since long time and have been previously studied although the targets were generally the hot waters or the sediments affected by the emissions (Smith and Cronan 1978, Dando et al. 1995, Price et al. 2013, Megalovassilis 2014).The present study aims at producing the first catalogue of the shallow submarine gas manifestations of the Aegean Sea andto characterizegeochemically the emitted gases.

Analogously to the ocean-bottom black/white smokers, “continental smokers” have recently been defined as sites of mantle degassing through continental crust. The goal of this research, carried out within the Deep Carbon Observatory Community, is to investigate the role of deeplysourced fluids in niche ecosystem differentiation in European continental smokers. A 16S rRNA gene survey of microbial communities was carried out on 11 geothermal manifestations of northern Greece, all showing a distinct contribution of mantle fluids (R/Ra up to 1.2) that allow to classify them as continental smokers. The selected sites cover a wide range of temperatures (15-77 °C), pH (6.11-8.46), Eh (-289 – 40 mV), salinities (TDS 0.4-38 g/L) and show significant differences in energy sources for microbial life, like H2 (up to 0.8 μmol/L), CH4 (up to 400 μmol/L), NH4 (up to 112 μmol/L), sulphide (up to 103 μmol/L), Fe (up to 130 mmol/L). Illumina sequencing revealed negligible presence of Archaea and dominance of Actinobacteria, Bacteroidetes, Firmicutes and Proteobacteria. Different bacterial taxa dominate depending on physico-chemical features: Deinococcus-Thermus dominates the hottest sites while chemoautotrophic genera (Sulfurovum and Sulfurimonas) are abundant in the most reducing H2S-rich waters. Signatures of deep-sea vent microbial ecosystems were detected in most assemblages, together with novel taxa.

Table S6. Galdieria sulphuraria introns that underwent alternative splicing in our studied samples. (PDF 981Â kb)

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 CH4 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 (O2, N2, CH4, CO2, He, Ne, Ar, H2, H2S and C2-C6 hydrocarbons) and isotopic (R/RA, δ13C-CO2, δ13C-CH4 and δ2H-CH4) composition. Results show that CH4 presents a wide range of concentrations (from

Figure S1. Two examples of spliceosomal single-gene phylogeny that show different ancestries of red algal spliceosomal genes. (PDF 137Â kb)

Street trees are an important part of urban vegetation due to their provisioning of different types of ecosystem services such as local climate regulation and contribution to aesthetical and recreational values. In order to provide these services, urban trees need to endure many stress factors not present in natural environments, such as the widespread use of impervious surfaces in the vicinity of street trees. However, few studies have evaluated the effect of this potential stress factor on urban tree growth. The aim of this study was therefore to investigate how ground surface permeability affects stem and current-year shoot growth of linden (Tilia europaea) street trees in Gothenburg, Sweden. We found that a small fraction of permeable ground surface in the vertically projected tree crown area caused lower stem growth and strongly suppressed current-year shoot growth. This finding can guide future city planning, demonstrating that the vitality of street trees is compromised when the permeable surface area in the vicinity of the tree is small.

Table S3. Presence and absence of human spliceosomal machinery-associated proteins in red algae. (PDF 134Â kb)

Figure S2. The search results for snRNA component of the spliceosome in Galdieria sulphuraria. (PDF 91Â kb)

Table S4. INFERNAL scores and e-values for red algal snRNA genes. (PDF 64Â kb)

Table S5. The intron statistics in red algal and Viridiplantae genomes. (PDF 71Â kb)

Hyperalkaline mineral springs related to active continental serpentinization are a theme of growing interest since they may contain significant amounts of abiotic gas and have important implications for energy resource exploration, subsurface microbiology and astrobiology. We report the discovery of a new hyperalkaline (pH∼12) spring issuing in the Agioi Anargyroi monastery at Ermioni (Greece), connected to serpentinization of peridotites of the Argolis ophiolite. Two water samples have been collected from separated springs and analysed for the chemical composition of major, minor and trace elements, and isotopic composition (2H and 18O) of water by IC, ICP-OES, ICP-MS and IRMS, and for the chemical (H2, O2, N2, CH4, CO2 and C2H6) and isotopic (He, δ2H-CH4 and δ13C-CH4) composition of dissolved gases. The Iliokastron Mélange Unit, comprising abundant serpentinized harzburgite, represent the aquifer feeding the hyperalkaline springs. The isotopic composition of water indicates a recent meteoric recharge probably through the close by and stratigraphically higher limestones of the Faniskos Unit. The Ca-OH water composition resulted to be similar to other hyperalkaline waters of Greece and worldwide. Although the concentrations of dissolved H2 are very low (tens of nmol/L) compared to other gases collected in similar manifestations, the concentrations of CH4 are considerable (38–314 μmol/L) and display isotopic compositions indicating a substantial if not exclusive abiogenic origin. Methane oxidation is also hypothesized in one of the two springs. © 2017 Elsevier Ltd

Figure S3. Sequence conservation in Galdieria sulphuraria genes. (PDF 181Â kb)

Twenty gas samples have been collected from the natural gas manifestations of Milos Island, the majority of which is found underwater along its coast. Furthermore, three anomalous degassing fumarolic areas (Kalamos, Paleochori and Adamas) have been recognized on-land. Almost all the gases are CO2-dominated with CO2 ranging from 88 to 99% vol for the samples taken underwater, while the on-land manifestations show a wider range (15–98%) due to air contamination. Methane reaches up to 1.0% vol, H2 up to 3.2% vol and H2S up to 3.5% vol indicating a hydrothermal origin of the gases. The isotope composition of He points out to mantle contributions up to 45%, while the C-isotope composition of CO2 (from −1.9 to +1.3‰ vs. V-PDB with most of the values around −0.5‰) suggests a prevailing limestone origin. Isotope composition of CH4, ranging from −18.4 to −5.0‰ vs. V-PDB for C and from −295 to +7‰ vs. V-SMOW for H, points to a geothermal origin with sometimes evident secondary oxidation processes. Additionally, CO2-flux measurements showed high values in the three fumarolic areas (up to 1100, 1500 and 8000 g/m2/d at Kalamos, Paleochori and Adamas respectively) with the highest CO2-flux values (up to about 23,000 g/m2/d) being measured in the sea at Kanavas with a floating chamber. The south-western part of the island was covered with a lower density prospection revealing only few anomalous CO2 flux values (up to 650 g/m2/d). The total output of the island (30.5 t/d) is typical of quiescent closed-conduit volcanoes and comparable to the other volcanic/geothermal systems of the south Aegean active volcanic arc (Nisyros, Kos, Nea Kameni, Methana and Sousaki). © 2018 Elsevier B.V.

Cyanidioschyzon merolae (C. merolae) is an acidophilic red alga growing in a naturally low carbon dioxide (CO

Greece is located on a convergent plate boundary comprising the subduction of the African Plate beneath the Eurasian, while the Arabian plate approaches the Eurasian in a northwestward motion. It is considered to be one of the most tectonically active regions of Earth with a complex geodynamic setting, deriving from a long and complicated geological history. Due to this specific geological background, conditions for the formation of many thermal springs are favoured. In the past years, almost all the already known sites of degassing (fumaroles, soil gases, mofettes, gas bubbling in cold and thermal waters) located in the Hellenic area were sampled at least one time. 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). Some of these sites have been selected for systematic sampling. Four of them have records longer than 10 years with tens of samplings also considering some literature data. Two of the sites are located in active volcanic areas (Santorini and Nisyros) while the other two are close to actively spreading graben structures with intense seismic activity (Gulf of Korinth and Sperchios basin). Results allowed to define long term background values and also some interesting variation related to seismic or volcanic activity.

It has recently been hypothesized that life on Earth could have been originated in hyperalkaline waters related to serpentinization of ophiolitic rocks, despite their extreme conditions (high pH and very low levels of nutrients). Five hyperalkaline springs of the Kizildag ophiolite complex (Turkey) were characterized. The dominant gases are either H2, CH4 or N2 . Bacterial diversity, analysed by RISA (Ribosomal Intergenic Spacer Analysis) revealed different profles for each spring. Sequencing of excised DNA bands allowed to identify the presence of Bacillus, Ralstonia, Pseudoalteromonas., Ureibacillus, Alicycliphilus, Anaerococcus. 16S ribosomal DNA sequencing by Illumina is in progress. Three samples were also positive for the presence of pmoA (encoding the key enzyme of methane oxidation) confrming the presence of methanotrophs in accordance to gas analyses that showed clues of microbial methane oxidation in the isotopic ratio. The presence of methanotrophs in these hyperalkaline springs highlights the extraordinary capability of the methanotrophs to adapt to extreme conditions.

The large amount of trace elements emitted from volcanoes has a strong impact on the close surrounding areas. Nyiragongo Volcano (Democratic Republic of Congo) belongs to the Virunga volcanic chain and is one of the most active volcanoes in Africa. It is characterized by the presence of an active and permanent lava lake with a persistent degassing activity. During a field trip in October-November 2014, we investigated the impact of the volcanogenic deposition in the surrounding of the crater by using different sampling techniques. Rain-gauges were used to collect atmospheric bulk deposition. Active and passive biomonitoring techniques (moss-bags and leaves of endemic plants – Senecio spp. and Amarantus viridis) were applied in order to investigate the dispersion of volcanic gas and particle emissions. We collected daily rainfall events at various sites: seven samples at the crater rim (on the western and southern side, 3470 m a.s.l.), one sample at the village Kibati (south-eastern flank, 1955 m a.s.l.) located at the up-wind base of the volcano (representing the local background), and four samples in the city of Goma (southern flank of the volcano, 1500 m a.s.l.). In order to implement our dataset, several samples of rainwater, amaranth leaves, soils and atmospheric depositions (by moss-bags and filters exposition) were sampled after the field trip by the researchers of the Goma Volcano Observatory (GVO). Since, the prevalent wind direction was blowing the plume in westerly or southwesterly direction, we exposed the raingauges in the villages of Bulengo, Rusayo and Kingi in the southwestern side respect to the volcano, and Kibumba in the southesthern as a background site, at increasing distance from the rim. In the same sites, leaves of Amarantus viridis, which is one of the principal vegetables eaten by the local population, were collected. Rainwater, moss bags and plant samples were analyzed for major and trace elements by IC, ICP-OES and ICP-MS. The large amount of emitted volcanic gases and particles includes sulfur, halogens and trace elements, that strongly affect rainwater chemistry and have a widespread impact on the surrounding vegetation of the volcano. Indeed, rainwater samples collected at the rim of the crater have low pH values (_ 3), high concentration of F- and Cl- (up to 12.0 and 12.8 mg/l, respectively) and dissolved toxic elements (such as Al, As, Cd, Cu, Fe and Pb), whereas samples from the city of Goma have pH values above 5 and the same elements show orders of magnitude lower concentrations. The biomonitoring results highlight that bioaccumulation of trace elements is extremely high in the proximity of the crater rim and decreases with the distance from the active craters. The data will be compared to earlier measurements taken in December 2011 and the impact of a slightly decreasing gas emission on the vegetation will be discussed.

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.

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

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 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). 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 2011-2012, Santorini was characterized by seismic-geodetic-geochemical unrest, which was unprecedented since the most-recent eruption occurred in 1950 and led to fear an eruption was imminent. This unrest offered a chance for investigating the processes leading to volcanic reactivation and the compositional characteristics of involved magma. We have thus analyzed the He-Ne-Ar-isotope composition of fluid inclusions in olivines and clinopyroxenes from cumulate mafic enclaves hosted in cogenetic dacitic lavas of the 1570-1573 and 1925-1928 eruptions of Nea Kameni. These unique data on Aegean volcanism were compared with those of gases collected in quiescent periods and during the unrest. The 3He/4He ratios (3.1-4.0 Ra) are significantly lower than the typical arc-volcano values (R/Ra ∼ 7-8), suggesting the occurrence of magma contamination in Santorini plumbing system, which would further modify the 3He/4He ratio of parental magmas generated in the local metasomatized mantle. The 3He/4He values of enclaves (3.1-3.6 Ra) are comparable to those measured in gases during quiescent periods, confirming that enclaves reflect the He-isotope signature of magma residing at shallow depths and feeding passive degassing. A significant increase in soil CO2 flux from Nea Kameni and anomalous compositional variations in the fumaroles were identified during the unrest, accordingly with previous studies. Simultaneously, 3He/4He ratios up to 4.0 Ra were also measured, demonstrating that the unrest was due to the intrusion into the shallow plumbing system of a more-primitive 3He-rich magma, which is even volatile richer and less contaminated than mafic magma erupted as enclaves. This new intrusion did not however trigger an eruption.

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.

Volcanic emissions represent one of the most important natural sources of trace elements (e.g. As, Cd, Cu, Hg, Pb, Sb, Tl and Zn) into the atmosphere, sequentially influencing the hydrosphere, lithosphere and biosphere. The human health hazard during episodic volcanic eruptions generally follows from deposition of coarse and fine particles (2.5-10 and < 2.5 μm) that produces effects such as asthma and lung and respiratory disease. Regarding passive degassing volcanoes, the harmful effects of fluorine fumigation are known both for vegetation (foliar necrosis) and human/animals (fluorosis), but only a few studies have been focused on the effects of potentially toxic trace elements. From a review published work on the metal output from active worldwide volcanoes, 52 publications (the first dating back to the 70’s) were identified, 13 of which on Etna and the others from some of the world most active volcanoes: Mt. St. Helens, Stromboli, Vulcano, Erebus, Merapi, White Island, Kilauea, Popocatepetl, Galeras,Indonesian arc, Satasuma and Masaya. In general, the review shows that available information is scarce and incomplete. We compiled a database both for concentrations and fluxes of 59 chemical elements (major and trace), which allowed us to constrain the compositional and output range. In this study we also present unpublished results from Etna (Italy), Turrialba (Costa Rica), Nyiragongo (Democratic Republic of Congo), Mutnovsky and Gorely (Kamchatka), Aso Asama and Oyama (Japan). Concentrations of major and trace elements were obtained by direct sampling of volcanic gases and aerosols on filters. Sulfur and halogens were collected by using filter-packs methodology, and analyzed by ion chromatography. Untreated filters for particulate were acid digested and analyzed by ICP-OES and ICP-MS. Sulfur to trace element ratios were related to sulfur fluxes to indirectly estimate elemental fluxes. Etna confirms to be one of the greatest point sources in the world. Nyiragongo results to be an additional large source of metals to the atmosphere, especially considering its persistent state of degassing from the lava lake. Turrialba and Gorely also have high emission rates of trace metals considering the global range. Only Mutnovsky volcano show values which are sometimes lower than the range obtained from the review, consistent with its dormant (fumarolic) stage of activity. The accurate estimation of individual and global volcanic emissions of trace metals is still affected by a high level of uncertainty. The latter depends on the large variability in the emission of the different volcanoes, and on their changing stage of activity. Moreover, only few of the potential sources in the world have been directly measured. This preliminary work highlights the need to expand the current dataset including many other active volcanoes for better constraining the global volcanic trace metal fluxes.