ALBERT

Description: Pantelleria is an active volcanic complex, at present in quiescent status, hosting a high enthalpy geothermal system. Explorative geothermal wells tapped exploitable water-dominated reservoirs at 600-800 m depth with maximum measured temperatures of 250°C. Five field campaigns for soil gas measurements were made in the period from July 2005 to October 2006. CO2 flux was measured with the accumulation chamber method at 807 sites, CO2 concentration and Rn activity in soil atmosphere were measured at 50 cm depth at 728 and 358 sites, respectively. The first campaign covered the whole island (about 83 km2) with an approximately sample density of 3.5 points per km2 for CO2 (flux and concentration) measurements and of 1.6 points per km2 for Rn measurements. The distribution of the sampling points was as far as possible evenly distributed. Only few limited areas resulted uncovered due to accessibility problems (inhabited areas, airport, steep or rough topography). In the following four surveys nine areas were studied with greater detail with sample densities of up to 100 points per km2. Flux measurements for the whole surveys gave values in the range 〈 0.1 - 4700 gCO2 m-2 day-1 (Fig. 1). Organic contribution could not be distinguished with statistical methods and in the present study was considered negligible above 30 g m-2 day-1. The sites displaying flux values above this threshold, representing about 32% of the total population, are almost all located within the 50 ka old caldera. The highest values correspond to the areas of Favara Grande and of the lake Specchio di Venere (Fig. 1), which have long been recognized as sites of anomalous degassing with the presence of active fumarolic vents with temperatures of about 100 °C in the former and thermal springs with abundant bubbling gases and a mofette in the latter. A new anomalous degassing area with very high output values has been identified on the southern flank of Mt. Grande (MGS in Fig. 1). In this area the vegetation cover strongly contrasts with that of the neighboring areas, consisting of scrubby low growing plants, mosses and bare land. Indeed, high CO2 flux values are always measured as long as such vegetation cover is found, abruptly decreasing when higher growing plants are present. The contrast is particularly evident in springtime and can be used as a good marker to individuate anomalous degassing areas. Further areas were studied in detail being sites of fumarolic manifestations. All of them are also sites of anomalous CO2 fluxes although of limited areal extension. The area of the last subaerial volcanic activity (Mursia) was also studied but the measurements were all far below the anomaly threshold. The total CO2 output of the anomalous degassing areas was estimated through geostatistical methods considering only values above the anomaly threshold. Results evidence that most of the output (87%) of the island is due to 3 of the anomalous degassing areas (Lake, MGS and Favare), the first of which accounts for more than 50%. Summing up the contribution of all anomalous areas we obtained a total output of about 0.3 kg s-1 (26 t day-1) over an area of about 0.58 km2. Concentrations of CO2 ranged from 0.039 (atmospheric value) up to 95 % (Fig. 1). The distribution of the values on a probability plot evidenced two statistically distinct populations with an inflection point at about 0.8 %. The values below the threshold (65 % of the population) can be considered as derived from organic activity while those above of magmatic/geothermal origin. The spatial distribution of the sites with anomalous concentrations closely resembles those of anomalous CO2 fluxes. Radon222 activity in the soil ranged from 〈 0.1 to 〉1000 kBq m-3 (Fig. 1). The distribution of the values on a probability plot evidenced three statistically distinct populations with inflection points at 40 and 400 kBq m-3. The lower population (74% of the entire population) probably corresponds to close to equilibrium values in soils with different contents of parent isotopes of the 238U decay chain and could be considered as background population. The values of the other two populations have to be considered anomalous and their high activity values have to be related either to sustained fluxes of a carrier gas (CO2) or/and to enhanced release from the soil due to fumarolic alteration. These anomalous values generally correspond to elevated CO2 flux values and are found close to active or fossil fumarolic areas. The close relationship with fumarolic alteration is confirmed by the contrasting behavior of two of the areas displaying the highest CO2 flux values, namely Favare and Lake. In the former area the high soil temperatures, testifying for anomalous fluxes of hydrothermal fluids, are reflected in a high percentage of anomalous values of soil 222Rn activity. On the contrary at the lake area, where the highest CO2 fluxes are measured, soil temperatures are much lower and consequently also soil 222Rn activity. The only high soil 222Rn activity values are measured along the southern shores of the lake where seeps of thermal water with about 60 °C are present. At Mursia, where recent basaltic lavas and scorias crop out, soil 222Rn activity is particularly low due to the low content of parent radioactive elements in these rocks. Finally, the present study evidenced a few areas were the gas hazard due to both CO2 and radon is elevated with either acute or chronic health issues for humans. These are the western shores of the lake and the village of Rekale the only inhabited area close to an anomalous degassing area.

Description: Published

Description: Patras, Greece

Description: 4.5. Studi sul degassamento naturale e sui gas petroliferi

Description: open

Description: Biomonitoring may be defined as the use of organisms and biomaterials (biomonitors) to obtain informations on certain characteristics of a particular medium (atmosphere, hydrosphere etc.). In particular, mosses accumulate large amounts of trace metals, making them good bioaccumulators to estimate atmospheric pollution. The moss-bags technique, introduced in the early 1970’, has become very popular. Such active biomonitoring technique is particularly useful in highly polluted areas and has been extensively used in industrial and/or urban areas to examine deposition patterns and to recognize point sources of pollution. The main objective of this study, which represents the first application of the moss-bags technique in an active volcanic area, was to test its efficacy in such environment. Complementary objectives were: to determine the different behavior and the geographic dispersion of volcanogenic elements emitted from Mt. Etna; to check the usefulness of a simpler analytical techniques (leaching instead of mineralization of the moss samples). A mixture of Sphagnum species was picked in a clean area, treated in laboratory (washed, dried and packed) and exposed in field for 1 month. Sites were chosen considering the prevailing wind at Mt. Etna’s summit. Milled samples were analyses for major and trace elements concentrations, after microwave digestion (HNO3 + H2O2), by ICP-MS and ICP-OES techniques. The same elements were also analyzed after simple leaching with deionized water (1/50 weight ratio for 4 hours). Leaching solutions were also analyzed by IC for F, Cl and SO4. Analyses clearly showed the efficacy of the moss-bags technique also in this peculiar environment. Several elements were strongly enriched in the mosses exposed to the volcanic emissions. The highest enrichment was measured close to the summit crater, but evidences of metals bioaccumulation were also found in down wind sites, at several km from the volcanic source. The accumulation factor (exposed/unexposed moss) allowed us to distinguish a group of elements (Tl, Bi, Se, Cu, As, Cd, S), which are highly mobile in the high temperature volcanic environment. Also alkali metals showed a significant increase in their concentrations, probably because of their affinity for the halide species carried by the volcanic plume. Also the simple and cheap leaching technique gave important indications on the plume dispersion pattern, especially for highly volatile elements (F, Cl, S, Tl).

Description: Published

Description: Torino, Italia

Description: 4.5. Studi sul degassamento naturale e sui gas petroliferi

Description: open

Description: Methane soil flux measurements have been made in 38 sites at the geothermal system of Sousaki (Greece) with the closed chamber method. Fluxes range from –47.6 to 29,150 mg m-2 d-1 and the diffuse CH4 output of the system has been estimated at 19 t a-1. Contemporaneous CO2 flux measurements showed a moderate positive correlation between CO2 and CH4 fluxes. Comparison of the CO2/CH4 soil flux ratios with the CO2/CH4 ratio of the gases of the main gas manifestations provided evidence for methanotrophic activity within the soil. Laboratory CH4 consumption experiments confirmed the presence of methanotrophic microorganisms in soil samples collected at Sousaki. Consumption was generally in the range from –4.9 to –38.9 pmolCH4 h-1 g-1 but could sometimes reach extremely high values (–33,000 pmolCH4 h-1 g-1.). These results are consistent with recent studies on other geothermal systems that revealed the existence of thermoacidophilic bacteria exerting methanotrophic activity in hot, acid soils, thereby reducing methane emissions to the atmosphere.

Description: Published

Description: 97–107

Description: 4.5. Studi sul degassamento naturale e sui gas petroliferi

Description: JCR Journal

Description: reserved

Description: Volcanic and geothermal areas are one of the major natural sources of sulphur gases to the atmosphere. Hydrogen sulphide (H2S) is a toxic gas mainly associated to geothermal systems while sulphur dioxide (SO2) is released in huge quantities from volcanoes characterized by open conduit activity. Apart from being one of the most impressive geodynamic expressions, volcanoes are also an important tourist attraction. During the summer season the number of tourists visiting the crateric areas each day is on average many tens at Stromboli, hundreds at Vulcano, Santorini and Nisyros and thousands at Etna. Touristic exploitation of active volcanic areas cannot exempt from warranting a reasonable security to the visiting persons. But while many risks in these areas have been since long time considered, gas hazard, a very subtle risk, is often disregarded. The atmospheric concentrations and dispersion pattern of naturally emitted SO2 were measured at three volcanoes of southern Italy (Etna, Vulcano and Stromboli) while that of H2S at four volcanic/geothermal areas of Greece (Sousaki, Milos, Santorini and Nisyros). Measurements were made with a network of passive samplers positioned at about 1.5 m above the ground, which gave time-integrated values for periods from few days to 1 month. Samplers were placed in zones of the volcanoes with high tourist frequentation. Measured concentrations and dispersion pattern depend on the strength of the source (craters, fumaroles), meteorological conditions and geomorphology of the area. At Etna, Vulcano, Stromboli and Nisyros measured concentrations reach values that are absolutely dangerous to people affected by bronchial asthma or lung diseases. But considering that these are average values over periods from few days up to one month, concentrations could have reached much higher peak values dangerous also to healthy people. The present study evidences a peculiar volcanic risk connected to the touristic exploitation of volcanic areas. Such risk is particularly enhanced at Etna where elderly and not perfectly healthy people can easily reach, with cableway and off-road vehicles, areas with dangerous SO2 concentrations.

Description: Published

Description: Bari, Italy

Description: 4.5. Studi sul degassamento naturale e sui gas petroliferi

Description: open

Description: Biomonitoring may be defined as the use of organisms and biomaterials (biomonitors) to obtain informations on certain characteristics of a particular medium (atmosphere, hydrosphere etc.). In particular, mosses accumulate large amounts of trace metals, making them good bioaccumulators to estimate atmospheric pollution. The moss-bags technique, introduced in the early 1970’, has become very popular. Such active biomonitoring technique is particularly useful in highly polluted areas and has been extensively used in industrial and/or urban areas to examine deposition patterns and to recognize point sources of pollution. The main objective of this study, which represents the first application of the moss-bags technique in an active volcanic area, was to test its efficacy in such environment. Complementary objectives were: to determine the different behaviour and the areal dispersion of volcanogenic elements emitted from Mt. Etna; to characterize the morphology and mineralogy of particles transported in the plume-system, basing on microscopy investigation. A mixture of Sphagnum species was picked in a clean area, treated in laboratory (rinsed, dried and packed) and exposed in field for 1 month. Sites were chosen considering the prevailing wind at Mt. Etna’s summit. Milled samples were analyses for major and trace elements concentrations, after microwave digestion (HNO3 + H2O2), by ICP-MS and ICP-OES techniques. Morphology and mineralogy of volcanic particulate were investigated by using a SEM with EDS. Analyses clearly showed the efficacy of the moss-bags technique also in this peculiar environment. Several elements were strongly enriched in the mosses exposed to the volcanic emissions. The highest enrichment was measured close to the summit crater, but evidences of metals bioaccumulation were also found in down wind sites, at several km from the volcanic source. The accumulation factor (exposed/unexposed moss) allowed us to distinguish a group of elements (Tl, Bi, Se, Cu, As, Cd, S), which are highly mobile in the high temperature volcanic environment. Also alkali metals showed a significant increase in their concentrations, probably because of their affinity for the halide species carried by the volcanic plume. Microscopic observations evidenced sulphate and halide crystals on particles trapped by the mosses. Mosses exposed at sites directly fumigated by the volcanic plume showed crystal growth also directly on the moss surface.

Description: Published

Description: Bari, Italy

Description: 4.5. Studi sul degassamento naturale e sui gas petroliferi

Description: open

Description: Volcanic emissions are considered one of the major natural sources of several trace metals (e.g. As, Cd, Cu, Pb, and Zn) to the atmosphere [Nriagu, 1989], and the geochemical cycles of these elements have to be considered strongly influenced by volcanic input. However, the accurate estimation of the global volcanic emissions of volatile trace metals into the atmosphere 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 [Hinkley et al. 1999]. Atmospheric deposition processes (wet and dry) are the pathways through which volcanic emissions return to the ground (soils, plants, aquifers), resulting in both harmful and beneficial effects [Baxter et al. 1982; Aiuppa et al. 2000; Brusca et al. 2001; Delmelle, 2003; Bellomo et al. 2007; Martin et al. 2009; Floor et al. 2011; Calabrese et al. 2011]. In the first part of this study we present the results of a literature review on trace metals emissions from active volcanoes around the world. In the second part, we present new data on the fluxes of the trace metals from Etna (Italy) and four active volcanoes in the world: Turrialba (Costarica), Nyiragongo (DRC), Mutnovsky and Gorely (Kamchatka). We found 27 publications (the first dating back to the 70’s), 13 of which relate to the Etna and the other include some of the world’s most active volcanoes: Mt. St. Helens, Erebus, Merapi, White Island, Kilauea, Popocatepetl, Galeras, Indonesian arc, Satasuma and Masaya. The review shows that currently there are very few data available, and that the most studied volcano is Mt. Etna. Using these data, we defined a range of fluxes for As, Ba, Bi, Cd, Cu, Fe, Mn, Pb, Se, V and Zn (Figure 1). To obtain new data we sampled particulate filters at the five above mentioned volcanoes. Filters were mineralized (acid digestion) and analyzed by ICP-MS. Sulphur to trace element ratios were related to sulphur fluxes to indirectly estimate trace elements fluxes. Etna confirms to be one of the greatest point sources in the world. The Nyiragongo results to be also a significant source of metals to the atmosphere, especially considering its persistent state of degassing from the lava lake. Also Turrialba and Gorely 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 the fact that it is mainly a fumarolic field. This work highlights the need to expand the current dataset including many other active volcanoes for a better constraint of global trace metal fluxes from active volcanoes.

Description: Published

Description: Nicolosi (Catania)

Description: 1.2. TTC - Sorveglianza geochimica delle aree vulcaniche attive

Description: open

Description: Passive samplers were used to measure the atmospheric concentrations of SO2 naturally emitted at three volcanoes in Italy (Etna, Vulcano and Stromboli) and of H2S naturally emitted at three volcanic/geothermal areas in Greece (Milos, Santorini and Nisyros). The measured concentrations and dispersion patterns varied with the strength of the source (open conduits or fumaroles), the meteorological conditions and the area topography. At Etna, Vulcano and Stromboli, SO2 concentrations reach values that are dangerous to people affected by bronchial asthma or lung diseases (〉1000 μg m−3). H2S values measured at Nisyros also exceed the limit considered safe for the same group of people (〉3000 μg m−3). The data obtained using passive samplers represent time-averaged values over periods from a few days up to 1 month, and hence concentrations probably reached much higher peak values that were potentially also dangerous to healthy people. The present study provides evidence of a peculiar volcanic risk associated with tourist exploitation of active volcanic areas. This risk is particularly high at Mt. Etna, where the elderly and people in less-than-perfect health can easily reach areas with dangerous SO2 concentrations via a cableway and off-road vehicles

Description: Published

Description: 1-13

Description: 4.5. Studi sul degassamento naturale e sui gas petroliferi

Description: JCR Journal

Description: restricted

Description: 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 local to global scale. They can also severely affect the atmospheric and terrestrial environment at timescales ranging from a few to millions of years. Mt. 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. Aim of this study is to characterize the chemical composition and the mineralogical features of the volcanogenic aerosol passively emitted from Mt. Etna. Twenty-five samples were collected by filtration technique from different sites between 2008 and 2014. 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, juvenile fragments or glass shards and crystals (e.g. plagioclases, pyroxenes, oxides); the second constituent consists of soluble compounds like sulfosalts or halide minerals (sulfates, chlorides and fluorides). Fluxes of major and trace metals emitted in the atmosphere have been estimated. By comparing the Etnean trace elements with those from European anthropic emissions, we conclude that Mt. Etna is the main persistent point source of major and trace metals in the Mediterranean region. Results gathered from this investigation is a fundamental importance due to the exposure and potential impact harmful chemical compounds for hundred thousand tourists visit each year the summit of Mt. Etna.

Description: Published

Description: 219

Description: 4V. Vulcani e ambiente

Description: JCR Journal

Description: restricted

Description: Fumarolic alteration crusts and efflorescences have been sampled at the Sousaki solfataric field. Samples have been analysed for mineralogical (XRD) and chemical composition (HNO3 digestion and leaching with distilled water). Results show that mineralogical and chemical compositions (major, minor and trace metals) are controlled by microenvironmental conditions. The sample collected in the anoxic part of a cave is composed almost exclusively by native sulfur. The samples collected in the oxidizing part of the cave and outside in relatively sheltered position are mainly composed by very soluble sulfates. Chemical composition evidence strong enrichments in Al, Ca, Cr, Fe, Mg and Ni which are present in highly soluble form and derive from the fumarolic alteration of the outcropping rocks (Marls and peridotites). One sample collected outside the cave, well exposed to atmospheric agents, is composed almost exclusively of gypsum and the chemical composition reveals, with respect to the previous samples, a relative enrichment of elements (Ba, Ca, K, Pb and Sr) forming less soluble sulfates. The presence of toxic metals like Al, Cr and Ni in high concentrations and highly soluble form evidences the potential impact of the fumarolic activity on the local environment.

Description: Published

Description: Myconos, Greece

Description: 4.4. Scenari e mitigazione del rischio ambientale

Description: open

Description: Sousaki (Corinthia, Greece), is a presently inactive volcanic area hosting a geothermal reservoir. Geothermal activity, still recognizable by a series of low temperature gas manifestation, is responsible of the widespread alteration of the outcropping rocks in the area. The main manifestations are hosted within caves whose walls are covered by alteration products in the form of crusts and efflorescences. This study presents the results of mineralogical and chemical analyses of the alteration products collected in the area. Leaching experiments with distilled water were also performed to get insights on the mobility of the elements incorporated in the alteration products. X-ray diffractometry allowed us to recognize a series of secondary minerals deriving from the alteration of the ophiolithic host rocks (altered peridotites to serpentinites) and whose composition depends mainly on the microenvironmental conditions in which they were formed. Elemental sulphur is the main mineral phase at the bottom of the caves where the atmosphere is anoxic. In the upper part of the caves, where oxygen is readily available, efflorescences are composed of many highly soluble acid sulphate minerals. In the oxidised part of the cave the stability of the mineral phases is mainly controlled by the relative humidity. The most hydrous mineral phases occur in the lower part of the cave, which is characterised by higher humidity values. Outside the caves highly soluble sulphates have been found in two samples collected in relatively sheltered position while a further sample collected outside the caves, but exposed to atmospheric agents, is composed almost exclusively by gypsum. Chemical analyses (ICP-MS after digestion with HNO3) revealed high contents of Al (up to 55,000 µg/g), Co (up to 655 µg/g), Cr (up to 7400 µg/g), Fe (up to 105,000 µg/g), Mg (up to 147,000 µg/g), Mn (up to 3700 µg/g) and Ni (up to 8800 µg/g) in the sample collected in the oxidised part of the caves. These strong enrichments confirm that the alteration products derive from the ophiolithic rocks. Leaching experiments evidenced the high mobility of these elements. Due to the extreme solubility of the mineral phases, on average between 70 and 94% of Al, Ca, Co, Cr, Cs, Cu, Fe, Li, Mg, Mn, Ni, Rb, Sr, U and Zn is in water soluble form. On the contrary, As, B, Ba, K, Mo, Na, Pb and V display lower solubilities (4 – 56%). Toxic elements’ mobility, favoured by the strongly acidic environment of the fumarolic area, may have severe environmental consequences.

Description: Published

Description: Myconos, Greece

Description: 4.4. Scenari e mitigazione del rischio ambientale

Description: open