ALBERT

Description: Seven 222Rn soil gas surveys have been accomplished throughout the N-E area of Stromboli Island. The former survey has been performed in July 2001, in a quiescent period since 1985, throughout a grid of 50 sites. The same grid has been repeated, in January 2003, soon after December, 28, 2002 eruption onset. The other surveys have been carried out in March 2003, in June 2003 after the April, 5, 2003 paroxysm event, and in July 2004 and March 2005 (quiescent periods). Finally, CO2 fluxes and soil gas surveys (Rn, CO2, CH4, H2, O2, N2, He) have been performed in March 2007 after the slightly February 2007 eruption onset. Results have highlighted correlated and synchronous 222Rn soil gas changes throughout the grid, allowing to discriminate the sectors of maximum increased 222Rn emission at surface, with a volcano-tectonical significance, mostly in January and March 2003 surveys. The positive NE-SW anomalies have been found maximum up to 13.000 Bq/m3 in January 2003, while after the Rn values returned to pre-eruptive values. Plotting single point concentration versus monitoring time, it is well evident that, in proximity of a paroxysm event, always the same points undergo to a radon concentration increasing. Data set of the investigated area has been divided in eight zones (on the basis of geographic sectors of the island). In every zone maximum Rn values correspond to the paroxysmal phase of the Stromboli eruptions. In particular, highest radon values are found in the “Lampara – COA” and “Town Hall” zones located along the known N40° lineament. After the eruptive phase, concentrations start to decrease. The NW-SE extension could be linked to the ongoing volcano collapse toward the NW located Sciara del Fuoco slope. Also the SE sector could undergo to collapses, along weakness lines (faults and fractures) whose prolongation in the Mole-S14 zone could release anomalous CO2-fluxes and anomalous soil gas concentrations (up to 10-20 % in CO2) dangerous for human health. The importance of geochemical monitoring together with volcanic time series, is a valid tool for evaluating the volcanic hazard.

Description: Unpublished

Description: Reykjavík - ICELAND

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

Description: open

Description: The Valentano area is located in the volcanic district of Vulsini Mounts, in the northern part of the Latium region (Central Italy). Geometry and shallow distribution of gas anomalies together with geophysical data on deep structural elements and anomalous geothermal gradient, confirm the presence of gas fluxes from a geothermal reservoir. The Valentano area is characterized by widespread natural emission phenomena, hazardous to human and animal health (many animals deaths have been recorded). A soil gas survey has been carried out in this area with the aim to understand the spatial distribution of the gaseous species and so the location of the main pathways (faults and fractures) causing the gas uprising. A detailed survey has been carried out at NW of Valentano town, where gas vent phenomena are characterised by high CO2 and CH4 concentrations. In this area, 75 soil gas samples (60 samples/km) have been collected. Data have been treated statistically (by normal probability plots), and by contour maps. CO2 and CH4 concentrations show maximum values up to 100% and 1000ppm respectively, detected over the highest emission points. CO2 and CH4 contour maps show high anomalous concentrations in the central and in the southern sector of the studied area and distributions have a spot geometry. Highest Rn concentrations (〉 100Bq/L) show a good spatial continuity in N-S direction overlapping the CO2 and CH4 highest values only in the central part of the anomaly. He concentrations show anomalous values only in the southern sector. The good correlation of the gas concentrations allow us to infer that the geochemical anomalous areas and the deep geothermic reservoir are strictly related. Besides, the good association between Rn and CO2 distributions confirms the CO2 carrier gas role for trace elements. Since this study has been partially funded by local authorities for the gas risk assessment, radon hazard map has been elaborated in order to highlight the risk areas for the human and animal health.

Description: Unpublished

Description: Reykjavìk, ICELAND

Description: 4.5. Degassamento naturale

Description: open

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: An ECBM feasibility study started for the Sulcis Coal Province (SW Sardinia, Italy): available geochemical, structural-geology, stratigraphic and reservoir engineering considerations as well as the newly gathered experimental data are discussed, including: fluid geochemistry (major and minor elements, dissolved gases, C and He isotopic ratios) of different strata/reservoir, coal composition and experimental data on CO2/CH4 adsorption-desorption on coal. A MapInfo GIS structure was built up including stratigraphic, geo-structural, hydro-geochemical, coal-compositional and environmental-impact information as well as the CO2 sources location and typology. Despite preliminary, these data highlighted both the challenging positive and negative aspects of the Sulcis Coal Province versus the exploitation of the ECBM technique. The most important objective of this phase I of the project is the selection of the best Sulcis ECBM test-pilot site, which will be followed (Phase II-2007) by the choice of a scaled up site and possibly by a future network (Phase III-2008). CO2 geological storage and CH4 production potentials in Sulcis have been grossly evaluated as a whole, in the frame of the Sardinia region CO2 sources, including the coal-fired power plants, both existent and foreseen (hundreds of millions of tonnes of CO2 are possible to be stored underground in the next decades).

Description: Unpublished

Description: Trondheim, Norway

Description: 4.4. Scenari e mitigazione del rischio ambientale

Description: open

Description: A geochemical survey, in shallow aquifers and soils, has been carried out to evaluate the feasibility of natural gas (CH4) storage in a deep saline aquifer at Rivara (MO), Northern Italy. This paper discusses the areal distribution of CO2 and CH4 fluxes and CO2, CH4, Rn, He, H2 concentrations both in soils and shallow aquifers above the proposed storage reservoir. The distribution of pathfinder elements such as 222Rn, He and H2 has been studied in order to identify potential faults and/or fractures related to preferential migration pathways and the possible interactions between the reservoir and surface. A geochemical and isotopic characterization of the ground waters circulating in the first 200 m has allowed to investigation of (i) the origin of the circulating fluids, (ii) the gas–water–rock interaction processes, (iii) the amount of dissolved gases and/or their saturation status. In the first 200 m, the presence of CH4-rich reducing waters are probably related to organic matter (peat) bearing strata which generate shallowderived CH4, as elsewhere in the Po Plain. On the basis of isotopic analysis, no hints of thermogenic CH4 gas leakage from a deeper reservoir have been shown. The d13C(CO2) both in ground waters and free gases suggests a prevalent shallow origin of CO2 (i.e. organic and/or soil-derived). The acquisition of preinjection data is strategic for the natural gas storage development project and as a baseline for future monitoring during the gas injection/withdrawing period. Such a geochemical approach is considered as a methodological reference model for future CO2/CH4 storage projects.

Description: Published

Description: 3-22

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

Description: JCR Journal

Description: restricted

Description: Soil–gas measurements of different gas species were performed in two distinct areas of the Corinth Gulf Rift (Greece): the Aigion-Neos Erineos-Lambiri (ANEL) fault zone and the Rion-Patras fault zone. Both zones lie in one of the most seismically active areas of the Euro-Mediterranean region, where a fast-opening continental rift is located. In particular, the geochemical investigations were focused on fault segments and fracture systems previously inferred by geomorphological, lithological and structural studies. In this work the applicability of soil–gas geochemistry surveys for the exploration of buried/hidden faults was tested by using various statistical methods. Moreover, a comprehensive geostatistical treatment of the collected data provided new insights into the control exerted by active structures on deep-seated gas migration towards the surface. In both investigated areas, the highest 222Rn and CO2 concentration peaks correspond with zones where the interaction among fracture and fault segments was inferred by structural and morphological methods. This indicates a clear correlation between the shape and orientation of the anomalies and the different attitude and kinematic behavior of the faults recognized in the two areas. Furthermore, obtained results show that gases migrate preferentially through zones of brittle deformation by advective processes, as suggested by the relatively high rate of migration needed to obtain anomalies of short-lived 222Rn in the soil pores

Description: Published

Description: 86-100

Description: 5A. Energia e georisorse

Description: JCR Journal

Description: restricted

Description: The Vicano–Cimino Volcanic District (VCVD) is related to the post-orogenic magmatic activity of the peri- Tyrrhenian sector of Central Italy. The chemical and isotopic compositions of 333 water discharges and 25 gas emissions indicate the occurrence of two main sources: 1) cold Ca-HCO3 to Ca(Na, K)-HCO3 type waters from relatively shallow aquifers hosted in volcanic and sedimentary formations; and 2) thermal Ca-SO4(HCO3) type waters located in a deep CO2-pressurized reservoir, hosted in carbonate–evaporite rocks and separated from the shallow aquifers by thick sequences of low-permeability formations. Carbon dioxide is mainly produced by thermal metamorphic decarbonation within the deepest and hottest parts of the carbonate–evaporite reservoir (δ13C–CO2 from−3.1 to+2.2‰vs. VPDB), likely affected by a mantle-rooted CO2. ReleaseofCO2-rich gases from the deep aquifer into the overlying shallow aquifers produces high-CO2 springs and bubbling pools. The spatial distribution of thermal waters and CO2-rich cold discharges is strongly controlled by fractures and faults located in correspondencewith buried structural highs. Stable isotopes (δD and δ18O) suggest thatmeteoric water feeds both the shallowand deep reservoirs. The relatively lowR/Ra values (0.27–1.19) indicate that He ismainly deriving from a crustal source, with minor component from the mantle affected by crustal contamination related to the subduction of the Adriatic plate. Consistently, relatively high N2/Ar and N2/3He ratios and positive δ15N–N2 values (from0.91 to 5.7‰vs. air) characterize the VCVD gas discharges, suggesting the occurrence of a significant “excess” nitrogen. Isotopic compositions of CH4 (δ13C–CH4 and δD–CH4 values from−28.9 to−22.1‰vs. VPDB and from −176 to −138‰ vs. VSMOW, respectively), and composition of light alkanes are indicative of prevalent thermogenic CH4, although the occurrence of abiogenic CH4 production cannot be excluded. The δ34S–H2S values (from+9.3 to+11.4‰vs. VCDT) are consistentwith the hypothesis of H2S production fromthermogenic reduction of Triassic anhydrites. Gas geothermometry in the H2O–H2–Ar–H2S system suggests that the VCVD gases equilibrated in a liquid phase at redox conditions controlled by interactions of fluids with the local mineral assemblage at temperatures lower (b200 °C) than that andmeasured in deep (N2000 m) geothermalwells. This confirms that secondary processes, i.e. steam condensation, gas dissolution in shallow aquifers, re-equilibration at lower temperature, and microbial activity, significantly affect the chemistry of the uprising fluids. Thermal water chemistry supports the occurrence in this area of an anomalous heat flowthat, coupledwith the recent demographic growth, makes this site suitable for direct and indirect exploitation of the geothermal resource, in agreement with the preliminary surveys carried out in the 1970's–1990's for geothermal exploration purposes.

Description: Published

Description: 96-114

Description: 5A. Energia e georisorse

Description: JCR Journal

Description: restricted