Description: 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〈0.5 to 925,200 μmol/mol) and isotopic values (δ13C-CH4 from−79.8 to +45.0‰vs. V-PDB; δ2H-CH4 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 CH4 concentration from EH to HH was recognized, whereas CH4 showed intermediate concentrations in VA. The CH4/(C2H6+C3H8) ratios (from 1.5 to 93,200), coupled with CH4 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 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 an abiogenic origin, although their chemical and isotopic characteristics may have been produced by secondary oxidation of thermogenic CH4, a process that in some of the sampled gases causes extremely positive isotopic values (δ13C-CH4 up to +45.0‰vs. V-PDB and δ2H-CH4 up to +301‰ vs. V-SMOW).

Description: Published

Description: 286-301

Description: 6A. Geochimica per l'ambiente e geologia medica

Description: JCR Journal

Description: We report on original geochemical data, which combine the rainfall trace metal contents from three different areas of Mt. Etna, variably fumigated by the volcanic plume, and those from soils, collected over the whole volcano. Trace element contents in rainfall appear mostly related to acidic ash leaching, while only for the most volatile elements (Cu, Zn, Cd, Pb, As, Sb, Tl, Se). We analyzed separately the labile fraction of soil samples, considered the fraction bioavailable to plants and soil organisms living in. The complexing medium used to extract the bioavailable fraction simulates the growth environment of plant roots.The contents of trace elements in the bioavailable fraction from soil samples showed peculiar patterns, apparently unrelated to the plume fumigation. The transition metal contents in the bioavailable fraction account for less than 15 % of the pseudo-total fraction and the highest contents were measured in the less acidic soil samples and farthest from the summit craters. In particular, high Fe, Mn, Co, Ni, Pb, Zn, Cd contents were paralleled by high soil organic carbon concentrations, which increased in the samples collected downwind the summit vents. Concerning immobile elements, their abundance in the bioavailable fraction was related to the degree of alteration of soils. Two elements, Se and Tl, were enriched in soil samples collected at closer distance from the summit vents. Their origin is probably related to the plume deposition.The study highlighted that the accessibility of plants to potentially harmful trace elements present in the soil is not simply related to the exposure to pollutants, but also to their fate in the pedogenetic environment.

Description: Published

Description: 57-78

Description: 6A. Geochimica per l'ambiente e geologia medica

Description: JCR Journal

Description: I was lucky enough to meet Mariano Valenza in September 1995. I was hitchhiking on the highway that leads from Cefalù to Palermo to go back home. I had spent my summer holidays in the beautiful and wild Madonie mountains. An off-road vehicle (a Land Rover Defender) stopped and a refined gentleman with a curious and charismatic gaze offered me a ride. During our journey, we chatted pleasantly and he told he was originally from that area. When I told him, I was a Geology student, he smiled at me and said “Then we will meet again soon, I am going to be your Teacher of Geochemistry!”. After a few weeks the lessons began and I met again Professor Valenza in Via Archirafi 36, at the University of Palermo. I will never forget the first introductive lesson of his course: “… we are going to study how the chemical elements have formed in the stars, and how these elements have spread out on our planet; we are going to study the chemicalphysical laws regulating their geochemical cycles and how they move in between the atmosphere, the hydrosphere and the lithosphere. We will also learn how the isotopes of these elements allow us to date the geological phenomena and the age of our own planet Earth; …let’s imagine that we are ourselves made of billions and billions and billions of atoms, and it is statically possible that one of Napoleon atom could be here, in this class room!”. I was truly fascinated and I discovered my passion for this interesting subject. In via Archirafi 36, in the historical building of the University of Palermo, once home of the Istituto di Mineralogia, I have graduated and got a Ph.D. in Geochemistry, and still nowadays I am working there. In these last 25 years I have learnt to know the stories of different personalities and their scientific researches, which have been hidden and looked after in the ancient building of the University for almost one century. With this article, we would like to remember Professor Mariano Valenza, by telling some stories about him and some others told by himself. Amongst these extraordinary stories we have focused on the one of a little-known scientist, Ludovico Sicardi (1895 - 1987), a modest man who followed his passion for volcanoes. In his field, he was a true innovator and the present research in the field of the geochemical surveillance of volcanos is deeply in debt to him. The “Scuola di Geochimica dei Fluidi”, born in the ‘70s at the University of Palermo, has the most debt of gratitude to him, but also the one which has treasured best his memory. This special paper is dedicated to Professor Valenza, who was one of the founders of this school and, before that, the teacher of most of this piece’s authors. He had preserved, beside the historical memory, also many documents, photos, and the scientific equipment used by Sicardi for his studies. Sergio Calabrese, Palermo, March 2020

Description: Published

Description: 413-435

Description: 4V. Processi pre-eruttivi

Description: 6TM. Poli Museali

Description: JCR Journal

Description: The eruption of Mt. Etna which occurred on December 24th 2018 was characterized by strombolian activity and fire fountains, emitted by the New South-East Crater and along a fissure that propagated towards the SE. The influence of volcanic emissions on atmospheric deposition was clearly detectable at several kilometres from the source. Wet and dry (bulk) deposition samples were collected each month, through a network of eleven collectors, in the areas of Milazzo, and Priolo between June 2018 and June 2019. They were analysed for major ions and trace elements concentrations. The pH values range from 3.9 to 8.3, while the EC values range from 7 to 396 μS cm-1. An extensive neutralization of the acidity has been recognised mainly due to the suspended alkaline dust particles, which have a buffering role in rainwater. A high load of Na+ and Cl- was observed at all sites, related to the closeness of the study areas to the coast, showing a high positive correlation (R2 = 0.989) along the line of Na+/Cl- ratio in seawater. During the eruption, the volcanic plume was carried by the winds for long distance (more than 300 km) affecting the area of Priolo but not that of Milazzo, which was upwind with respect to Mt. Etna. The impact of volcanic HF was clearly recognised in the samples collected after the eruption. Volcanic SO2 and HCl had a lower impact due to the overwhelming input of anthropogenic sulfate and marine chloride. On the contrary, the signature of the Mt. Etna eruption can be well recognised in the high concentrations of certain trace elements in the samples collected immediately after the eruption. The strongest contrast between affected and non-affected samples was recognised in Al, Cd, and especially in the volatile elements Tl and Te, which are typically enriched in volcanic emissions. The results showed that volcanic eruptions might have a relevant effect on the atmospheric chemistry and on the composition of rainwater up to distances of 80 km from the emission vents.

Description: Published

Description: 341-358

Description: 6A. Geochimica per l'ambiente e geologia medica

Description: JCR Journal

Description: The complex geology of Greece includes two important parallel running ophiolitic belts. The Othrys Massif in central Greece belongs to the westernmost of them. In the current study, 33 water samples from cold hyperalkaline and hypothermal (T 〈 40°C) alkaline springs and 30 gas samples (either dissolved or free) were collected at 17 different sites in and around this wide ophiolite outcrop, aiming to determine the origin of fluids and evidence gas-water-rock interaction processes taking place in the area. Water samples were analysed for their chemical (major ions and trace elements) and isotope (δ18O-H2O, δ2H-H2O) composition. They can be subdivided into alkaline (pH 〈11) of both Mg-Ca-HCO3 and Na-HCO3 composition and hyperalkaline (pH 〉 11 and Ca-OH composition). Trace elements generally showed very low concentrations and mostly inversely correlated with pH. Gases were analysed for their chemical (He, Ne, Ar, H2, O2, N2, CH4, C2H6, CO2 and H2S) and isotope (δ13C-CH4, δ2H-CH4, δ13C-CO2) composition. Samples from alkaline waters were mainly dominated by CH4 (from 128,000 to 915,000 μmol/mol), while hyperalkaline waters showed a N2-rich composition (from 727,000 to 977,000 μmol/mol). Methane had a wide range of isotope compositions (δ13C-CH4 from -74.5 to -14.5 ‰ and δ2H-CH4 from -343 to -62 ‰). Alkaline waters present the most negative isotope values for CH4, evidencing a biogenic (both thermogenic and microbial) origin. Many of the hyperalkaline waters had CH4 isotope values compatible with an abiogenic origin through serpentinization processes but occasionaly very negative values were recorded, indicating sometimes a clear biogenic contribution. Finally, few samples both from alkaline and hyperalkaline waters showed some evidence of secondary oxidation processes.

Description: Published

Description: 42-56

Description: 6A. Geochimica per l'ambiente e geologia medica

Description: JCR Journal

Description: A multidisciplinary field campaign was carried out at Nisyros Island (Greece). Hydrothermal gases were sampled and analysed, and CH4 and CO2 fluxes from the soils were measured with the accumulation chamber method. The sampling area (Lakki plain) covers an area of about 0.08 km2, and includes the main fumarolic areas of Kaminakia, Stefanos, Ramos, Lofos and Phlegeton. Flux values measured at 130 sites range from −3.4 to 1420 mg m−2 d−1 for CH4 and from 0.1 to 383 g m−2 d−1 for CO2. The fumarolic areas show very different CH4 degassing patterns, Kaminakia showing the highest CH4 output values (about 0.8 t a−1 from an area of about 30,000 m2) and Phlegeton the lowest (about 0.01 t a−1 from an area of about 2500 m2). The total output from the entire geothermal system of Nisyros should not exceed 2 t a−1. Previous indirect estimates of the CH4 output at Nisyros, based on soil CO2 output and CH4/CO2 ratios in fumarolic gases, were more than one order of magnitude higher. The present work further underscores the utmost importance of direct CH4 flux data because indirect methods totally disregard methanotrophic activity within the soil. Ten soil samples were collected for CH4 consumption experiments and for metagenomic analysis. Seven of the soil samples showed small but significant CH4 consumption (up to 39.7 ng g−1 h−1) and were positive for the methanotrophs-specific gene (pmoA) confirming microbial CH4 oxidation in the soil, notwithstanding the harsh environmental conditions (high temperature and H2S concentrations and low pH).

Description: Published

Description: 119546

Description: 6A. Geochimica per l'ambiente e geologia medica

Description: JCR Journal

Description: 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. VPDB for C and from−295 to+7‰vs. V-SMOWfor 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).

Description: Published

Description: 13-22

Description: 4V. Processi pre-eruttivi

Description: JCR Journal

Description: Greece is a region characterised by intense geodynamic activity that favours the circulation of hydrothermal fluids in the crust transporting volatiles from either the deep crust or the mantle to the surface. Elevated heat flow values are detectable at Sperchios Basin and North Euboea (central Greece), two areas defined by a system of deeply rooted extensional faults and Quaternary volcanic activity. This setting contributed to the formation of numerous hydrothermal systems, which are mostly expressed as CO2-rich thermal springs with intense bubbling. The CO2 output from six bubbling pools has been determined by flux measurements with the use of the floating chamber method. The highest bubbling CO2 output has been found at Thermopyles and Psoroneria (0.6 and 0.84 t/d, respectively), where the outgoing channels have an elevated flow (〉250 l/s) of gas-charged water (〉15 mmol/l of CO2). Although no bubbling is noticed along the stream, the CO2 content decreases by an order of magnitude after few hundreds of metres, indicating an intense degassing from the water. Taking into account the water flow and the amount of CO2 lost to the atmosphere, the CO2 output of the outgoing channels is quantified in 12.5 t/d for Thermopyles and 9.23 t/d for Psoroneria. Output estimation has also been made for the other springs of the area. The diffuse CO2 release from the outgoing channels has always been higher respect to that of the visible bubbling, suggesting that most of the degassing is “hidden”. Furthermore, the loss of CO2 from the water has determined a shift in dissolved carbonate species as demonstrated by the pH increase along the channel that led eventually to an oversaturation in carbonate minerals and therefore travertine deposition. The total CO2 output to the atmosphere of the study area is estimated at ~27 t/d, with the major contribution deriving from the degassing along the outflow channels of the thermal springs. Such output is comparable to that of the single active volcanic systems along the South Aegean Active Volcanic Arc and highlights the importance of “hidden” degassing along CO2-oversaturated streams.

Description: Published

Description: 104660

Description: 6A. Geochimica per l'ambiente e geologia medica

Description: JCR Journal

Description: The attention devoted to our valuable geological heritage land has been often lacking in Italy. We have experienced it, as field experimentalist or as science teachers. So, we need to improve the knowledge of Earth-science at any educational level and we think an empiric approach, can be the proper beginning for a successful scientific cognitive path. The geo-tourism essentially attracts foreigners. During our field experiences on active volcanoes, we are still surprised by local visitors who enjoy seasonal activities, like skiing on the flanks of Etna, or doing sea activities on the coastal beaches at Vulcano and Stromboli, but who are not interested in the ongoing volcanic processes. Consequently, we have integrated the social impetus that drives active citizenship with school education in order to relate our scientific knowledge to the professional and existential needs of young students. Two scientific workshops have been carried out in collaboration with the science school teacher, the researcher of a naturalistic association (Geode), and researchers of the INGV. The first (A.Y. 2015/2016) was targeted to the Aeolian isles of Vulcano and Stromboli, the second to M. Etna (2016/2017). Set goals: - to increase the sensibility, respect and care for natural environment, as well as the awareness of the natural phenomena characterizing it; - to overcome the traditional school setting organized in the classroom, using both field and laboratory approach; - use a more effective (and attractive) teaching style to increase young people cognitive abilities, training also the relational skills, like work ethics, orally speaking, and teamworks; - to foster the multi-disciplinar approach for solving complex problems; - to contaminate disciplines with digital technologies highlighting instrumental potentiality and versatility; - to orient young people into future professional applications. The didactic pathway provided information on geology, volcanology and on botanic-naturalistic aspects of the Aeolian archipelago, Mount Etna and surrounding areas. We formed groups of students, heterogeneous for class and address, ranging from 28 to 35 items. The didactic experience consisted into theoretical lessons in the classroom and excursions by land and by sea, through the most significant itineraries of Vulcano, Stromboli and Etna (Monti Rossi, Alcantara Gorges). The students were introduced to the volcanologist's task in the field of volcanic surveillance, through an operational approach. Volcanic surveillance is a fast evolving multi-disciplinar research field, aimed to the mitigation of risk. The application of geochemical and of geophysical principles and instrumentations, allow to monitor some changes of energy release occurring in volcanic system. Field activities have provided: a) learning of the main notions of orienteering (geographic map reading, compass, GPS, Google Earth); b) petrologic recognition in field and by microscope; c) sampling of volcanic fluids emitted from the fumaroles on the rim of the crater; d) simulation of geochemical explorations, using temperature and pH sensors on a mesh of acquisition points; e) identification of the main botanical species, typical of the visited areas. By returning the campaign data, students shared the acquired data and prepared a final presentation with some digital software: virtual padlet, power point presentation, genially presentation. The students' cognitive and soft skills were evaluated as inputs and outputs from the workshops, to qualify the experience, highlighting strengths and weaknesses in the perspective of continuous improvement. Following the release of L.107 / 2015 "La Buona Scuola", this workshop experience has been recognized as a school-work didactic method (“Alternanza Scuola Lavoro”) for high schools (L.107/2015 art.1, 33 – 43). In fact, one of the training objectives set out in Art. 1c.7e;i, is the deepening of the methodological dimension by expansion and innovation of teaching strategies.

Description: Published

Description: PISA

Description: 2SR. VULCANI - Servizi e ricerca per la Società

Description: Greece belongs to the most geodynamically active regions of the world and as such it has to be considered an area of intense geogenic degassing. Here we review all the papers already published in the scientific literature on both the geochemistry of gas manifestations and the CO2 and CH4 release, in an attempt to obtain the first nationwide inventory of the natural output of these carbon gases in Greece. The best studied and most exhaling area is the South Aegean Active Volcanic Arc (SAAVA), which releases more than 1.3×105 tons of CO2 per year. Continental Greece, on the contrary, is much less studied but may release CO2 in the same order of magnitude in its eastern-central and northern parts. The western and south-western parts of Greece are conversely the main areas in which methane and higher hydrocarbons degas. Methane output of Greece is much less constrained, but the presence of one of the biggest thermogenic gas seepages of Europe, which releases about 200 tons of CH4 per year to the atmosphere, underscores its potentially high contribution.

Description: Published

Description: 60-74

Description: 6A. Geochimica per l'ambiente e geologia medica

Description: JCR Journal