Soil-Gas Geochemistry: Significance and Application in Geological Prospectings

Gas-geochemistry has been proven to be a reliable and simple technique to apply, at different scales, in many geological scenarios. The study of spatial distribution of soil-gas anomalies, at the surface, can give important and interesting information on the origin and processes involving deep and superficial gas species. This information can be applied and studied in different frameworks, for example: I) seismic zonation, examining, at the surface, anomalous concentrations of deep gas species that upraise throughout preferential pathways (faults and/or fractures); II) environmental protection, monitoring naturally occurring toxic gases and highlighting zones with high health risks for humans; III) geomorphological and structural research, detecting the aggressive fluid piping that causes carsic phenomena; IV) radionuclide migration, both in the pollution assessment from abandoned uranium mines and in the study of high-level radioactive-waste isolation systems. Soil-gas distribution could be affected by surface features such as pedological, biogenic and meteorological factors: these are supposed to have only a subordinate effect on gas leakage. However, it is possible to properly interpret soil-gas anomalies and recognize, and avoid, influences of surface features studying the association of different gases (with different origin and physical/chemical behavior), collecting a large number of samples during periods of stable meteorological and soil moisture conditions (e.g., during dry season) and using appropriate statistical treatment of data (i.e., experimental variograms to investigate the spatial dependency of gas concentrations). We will try, in this paper, to give hints for a better comprehension of the main mechanisms ruling soil-gas features both displaying and discussing some data obtained in either prospecting or monitoring case studies. Soil-gas geochemistry involves the study of many gaseous species (i.e., radiogenic, trace and diagenetic gases) each of them can give specific information on the conditions that allow their formation, accumulation and/or migration. In this study, we outline the results from two analyzed soil-gases: radon (222Rn), a radiogenic trace gas, and carbon dioxide (CO2) which generally acts as carrier for trace gases.Published183-2044.5. Studi sul degassamento naturale e sui gas petroliferiope

The Application of Soil-Gas Technique to Geothermal Exploration: Study of Hidden Potential Geothermal Systems

Geochemical studies were conducted using soil-gas and flux surveyings for locating both permeable zones in buried reservoirs and the presence of possible gaseous haloes linked to active geothermal systems. In this work we focused our interest on the distribution of soil-gas concentrations (Rn, Th, He, H2, O2, N2, CO2, CH4 and H2S) in the soil air of the Tetitlan area (Nayarit, Mexico) considered a potential thermal field and characterized by scarcity of surface manifestations. A total of 154 soil-gas samples and 346 CO2 and CH4 flux measurements were collected in an area of about 80 square kilometres. The performed soil-gas and flux geochemical surveys highlighted a general rising patterns linked to local fault system, with the important implication that the highest CO2 and CH4 fluxes, as well as Rn concentrations, could be used in undeveloped geothermal systems to identify main upflow regions and areas of increased and deep permeability

Very slightly anomalous leakage of CO2, CH4 and radon along the main activated faults of the strong L'Aquila earthquake (Magnitude 6.3, Italy). Implications for risk assessment monitoring tools & public acceptance of CO2 and CH4 underground storage.

Abstract The 2009-2010 L'Aquila seismic sequence is still slightly occurring along the central Apenninic Belt (August 2010), spanning more than one year period. The main- shock (Mw 6.3) occurred on April 6th at 1:32 (UTC). The earthquake was destructive and caused among 300 casualties. The hypocenter has been located at 42.35 °N, 13.38° at a depth of around 10 km. The main shock was preceded by a long seismic sequence starting several months before (i.e., March, 30, 2009 with Mw 4.1; April, 5 with Mw 3.9 and Mw 3.5, a few hours before the main shock). A lot of evidences stress the role of deep fluids pore-pressure evolution–possibly CO2 or brines - as occurred in the past, along seismically activated segments in Apennines. Our geochemical group started to survey the seismically activated area soon after the main-shock, by sampling around 1000 soil gas points and around 80 groundwater points (springs and wells, sampled on monthly basis still ongoing), to help in understanding the activated fault segments geometry and behaviour, as well as leakage patterns at surface (CO2, CH4, Radon and other geogas as He, H2, N2, H2S, O2, etc …), in the main sector of the activated seismic sequence, not far from a deep natural CO2 reservoir underground (termomethamorphic CO2 from carbonate diagenesis), degassing at surface only over the Cotilia-Canetra area, 20 km NW from the seismically activated area. The work highlighted that geochemical measurements on soils are very powerful to discriminate the activated seismogenic segments at surface, their jointing belt, as well as co-seismic depocenter of deformation. Mostly where the measured "threshold" magnitude of earthquakes (around 6), involve that the superficial effects could be absent or masked, our geochemical method demonstrated to be strategic, and we wish to use these methods in CO2 analogues/ CO2 reservoir studies abroad, after done in Weyburn. The highlighted geochemical - slight but clear anomalies are, in any case, not dangerous for the human health and keep away the fear around the CO2–CH4 bursts or explosions during strong earthquakes, as the L'Aquila one, when these gases are stored naturally/industrially underground in the vicinity (1–2 km deep). These findings are not new for these kind of Italian seismically activated faults and are very useful for the CO2–CH4 geological storage public acceptance: Not necessarily (rarely or never) these geogas escape abruptly from underground along strongly activated faults

Continuous/discrete geochemical monitoring of CO2 Natural Analogues and of Diffuse Degassing Structures (DDS): hints for CO2 storage sites geochemical monitoring protocol

Abstract Italy is one of the most promising prone areas to study the CO 2 behavior underground, the caprock integrity to the CO 2 leakage, mostly in presence of pervious/geochemically active faults, due to a wide availability of CO 2 rich reservoirs at a depth between 1 and 10 km, as highlighted by recent literature. These deep CO 2 reservoirs generate at least 200 leakage areas at surface throughout Italy which have been defined "Diffuse Degassing Structures" (DDS) by INGV. These are widely studied by INGV institutionally by a long term convention with the Civil Protection Department (DPC) with the aim to catalog, monitor and assess the Natural Gas Hazard (NGH, namely the probability of an area to become a site of poisonous peri-volcanic gas exhalation from soils). More than 150 researcher of INGV are involved in monitoring areas affected by the CO 2 presence underground and at surface, by continuous monitoring on-line networks (around 40 stations throughout Italy, including the Etna area, Aeolian Islands, Umbria region, Piemonte region, etc.) and discretely (9 groups of research were involved in the last years to localize, define and monitor almost all the DDSs in Italy), by sampling and analyzing chemical and isotopic compounds, useful to discriminate the origin, evolution and natural gas hazards of the examined DDS. In this paper, we will discuss some DDS catalogued and studied by a Rome INGV Research Unit (UR 11) which focused its work in Central Italy, throughout different DDS, also in relation to the diverse seismotectonic settings, to discover buried faults as possible gas leakage pathways, mostly if they are "geochemically" activated. In particular we discuss, among the discrete monitoring techniques exploited by INGV, soil gas surveying, which consists in a collection of gas samples from the soil zone not saturated (dry zone) to measure the geogas gaseous species both in fluxes (CO 2 , CH 4 , 222 Rn) and in concentration (He, H 2 , H 2 S, helium, hydrogen, CO 2 , CH 4 , 222 Rn), that permeate the soil pores. The total CO 2 flux budget was calculated as "baseline" degassing rate of these " CO 2 analogues". A good discrete areal monitoring is prerequisite to design sound continuous monitoring network to monitor CO 2 related parameters in liquid/gas phases, to review the protocol of the Annex II of the European Directivity on CCS

Panarea natural-lab: eight years of underwater research

The volcanic island of Panarea is characterized by the presence of continuous emission of volcanic gases from the seafloor. In November 2002 the system increased its flow of some order of magnitude and since then a steady release of gas is present generating bubble plumes that, in the shallowest points, reach the sea surface. Due to the environmental conditions, the area close to the shore and shallow water can be utilized as a “natural lab” to study the effect of high levels of CO2on the marine realm by surface techniques and directly by means of SCUBA diving. Since 2002, over one hundred hours of diving have been utilized to collect samples of fluids and sediments and to study the biota. After a first phase of volcanic surveillance, the island is more recently studied as a “natural analogue” for the development of reliable monitoring techniques for potential seepage from sub-seabed carbon storage sites. Hereby we present a synthesis of eight years of research in the area

Very slightly anomalous leakage of CO2, CH4 and radon along the main activated faults of the strong L’Aquila earthquake (Magnitude 6.3, Italy). Implications for risk assessment monitoring tools & public acceptance of CO2 and CH4 underground storage.

The 2009-2010 L'Aquila seismic sequence is still slightly occurring along the central Apenninic Belt (August 2010), spanning more than one year period. The main- shock (Mw 6.3) occurred on April 6th at 1:32 (UTC). The earthquake was destructive and caused among 300 casualties. The hypocenter has been located at 42.35°N, 13.38° at a depth of around 10 km. The main shock was preceded by a long seismic sequence starting several months before (i.e., March, 30, 2009 with Mw 4.1; April, 5 with Mw 3.9 and Mw 3.5, a few hours before the main shock). A lot of evidences stress the role of deep fluids porepressure evolution – possibly CO2 or brines - as occurred in the past, along seismically activated segments in Apennines. Our geochemical group started to survey the seismically activated area soon after the main-shock, by sampling around 1000 soil gas points and around 80 groundwater points (springs and wells, sampled on monthly basis still ongoing), to help in understanding the activated fault segments geometry and behaviour, as well as leakage patterns at surface (CO2, CH4, Radon and other geogas as He, H2, N2, H2S, O2, etc...), in the main sector of the activated seismic sequence, not far from a deep natural CO2 reservoir underground (termomethamorphic CO2 from carbonate diagenesis), degassing at surface only over the Cotilia-Canetra area, 20 km NW from the seismically activated area. The work highlighted that geochemical measurements on soils are very powerful to discriminate the activated seismogenic segments at surface, their jointing belt, as well as co-seismic depocenter of deformation. Mostly where the measured “threshold” magnitude of earthquakes (around 6), involve that the superficial effects could be absent or masked, our geochemical method demonstrated to be strategic, and we wish to use these methods in CO2 analogues/CO2 reservoir studies abroad, after done in Weyburn. The highlighted geochemical -slight but clear- anomalies are, in any case, not dangerous for the human health and keep away the fear around the CO2-CH4 bursts or explosions during strong earthquakes, as the L'Aquila one, when these gases are stored naturally/industrially underground in the vicinity (1-2 km deep). These findings are not new for these kind of Italian seismically activated faults and are very useful for the CO2- CH4 geological storage public acceptance: not necessarily (rarely or never) these geogas escape abruptly from underground along strongly activated faults

Study of natural analogues for the comprehension of gas migration mechanism

Soil gas anomalies are useful to recognize influences of surface features on natural gas migration. The study of the association of different gases (with different origin and physical/chemical behavior), the collection of a large number of samples during periods of stable meteorological and soil moisture conditions (e.g., during dry season) and the use of appropriate statistical treatment of data are fundamental in the comprehension of gas migration mechanism. Gas geochemistry has been proven to be a reliable and simple technique to apply, at different scales, to many geological scenarios [Quattrocchi et al. 2001; Baubron et al. 2002; De Gregorio et al. 2002; Pizzino et al. 2002; Lewicki et al. 2003; Voltattorni et al. 2009; Lombardi and Voltattorni, 2010]. The study of spatial distribution of soil gas anomalies, at the surface, can give important and interesting information on the origin and processes involving deep and superficial gas species. This information can be applied and studied in different frameworks, for example: 1. geological sequestration of anthropogenic CO2 to reduce the amount of greenhouse gases released to the atmosphere. Natural gas emissions represent extremely attractive surrogates for the study and prediction of the possible consequences of leakage from geological sequestration sites of anthropogenic CO2 (i.e., the return to surface potentially causing localized environmental problems). 2. radionuclide migration in the study of high-level radioactive-waste isolation systems. The main approach is to study the natural migration of radiogenic particles or elements throughout clay formations that are considered an excellent isolation and sealing material due to their ability to immobilize water and other substance over geological timescales

Giuseppa and the Dragon: Storytelling and Focused Game to Introduce Pre-scholar Children to the Seismic Risk

Italy is a seismic country being in the merging zone of African and Euro-Asiatic plates and several destructive earthquakes occurred in the last few decades. For this reason, it is important to educate children about seismic risk and make them aware of simple behaviors and expedients that can save their life. But, how can we explain seismic risks or what an earthquake is to pre-scholar children? It is not simple because, at this age, children do not know what the word “risk” means and entails. A method to explain earthquakes has been developed and tested in a school with the collaboration of teachers willing to educate their young students to deal with natural risks and teach how properly behave. The method consists in a story telling using a “butai-kamishibai” (Japanese imagine theatre) with manually sliding paper imagines. This old technique, used by wandering storyteller, is very incisive because the butai-kamishibai produces by itself a scenography that creates a strong involvement between the teller and the listeners. The story is about a young girl (named Giuseppa) traveling inside the Earth where she meets a dragon whose jumps cause earthquakes. Inside the story, there is a nursery rhyme explaining what to do when the dragon jumps and the school shakes (for instance, go under the desk, be far from windows, keep calm, line up in pairs and so on). The story telling has just the purpose to catch children attention while the nursery rhyme helps to teach, entertaining, the right behaviors to adopt during an earthquake. After a break during which children can create/color their own dragon, there is a game having the aim to draw up the life-saving actions. The game is developed by means of a magnetic blackboard divided in two parts (true and false), magnets of the story characters acting (in the right or wrong way) during an earthquake. One by one, children pick a magnet from a bag and put it on the right/wrong side of the blackboard explaining why. After the first test, this method has been carried out in several nursery schools always obtaining a positive outcome. Teachers love Giuseppa story because activities are proposed in a playful but, at the same time, seriously way especially when life-saving actions are showed communicating the importance of what children are learning.UnpublishedSan Francisco - California - USA2TM. Divulgazione Scientific

Studio di formazioni argillose quali barriere geologiche per la migrazione di radionuclidi nell'ambito della radioprotezione

Dottorato di ricerca in scienze della terra. 12. ciclo. Docenti guida S. Lombardi e L. ServaConsiglio Nazionale delle Ricerche - Biblioteca Centrale - P.le Aldo Moro, 7, Rome; Biblioteca Nazionale Centrale - P.za Cavalleggeri, 1, Florence / CNR - Consiglio Nazionale delle RichercheSIGLEITItal

Study of the geothermal potential of Tetitlan area (Nayarit, Mexico)

The soil-gas method has been widely used to infer the nature of subsurface geology/geochemistry since gases released from active geothermal systems, can freely rise through overlying cover to be detected in the near-surface. The high mobility of some gases makes them the best pathfinders for concealed natural resources. Indeed, the gases produced and/or accumulated in geothermal reservoirs can escape towards the surface by diffusion, through transportation by rising hot fluids and by migration along fractures and faults. The Tetitlan area (Nayarit, Mexico) has been investigated by CFE (Comisiòn Federal de Electricidad) since nineties by means of exploratory wells for geothermal purposes and gravimetric prospectings. On the basis of obtained results, a potential deep geothermic reservoir has been inferred in spite of the scarcity of evident surface manifestations (e.g., hot springs, vents). A total of 154 soil-gas samples and 346 CO2 and CH4 flux measurements were collected in an area of 72 square kilometres. The performed soil-gas and flux geochemical surveys highlighted a general rising patterns linked to local fault system. Experimental variograms confirmed the presence of anisotropies highlighting different spatial domains. The contour maps elaborated on the basis of the calculated experimental variograms, demonstrated that gas emission at the surface is not spatially heterogeneous within studied area with the important implication that the highest fluxes, as well as concentrations, could be used in undeveloped geothermal systems to identify main upflow regions and areas of increased and deep permeability. Further, the total natural gas emission has been calculated in order to estimate the exploitation potential of the inferred system. The overall calculated levels of CO2 and CH4 emissions (2.35 104 t/day and 6.6 103 t/ day, respectively) from the Tetitlan system is found to remain within the range of normalized emissions measured for geothermal, volcanic, non-volcanic and hydrothermal systems worldwide.UnpublishedTorino4.5. Studi sul degassamento naturale e sui gas petroliferiope