The imprint of thermally induced devolatilization phenomena on radon signal. Implications for the geochemical survey in volcanic areas

Thermal gradients due to magma dynamics in active volcanic areas may affect the emanating power of the substrate and the background level of radon signal. This is particularly effective in subvolcanic substrates where intense hydrothermal alteration and/or weathering processes generally form hydrous minerals, such as zeolites able to store and release great amounts of H2O (up to ∼25 wt.%) at relative low temperatures. To better understand the role played by thermally induced devolatilization reactions on the radon signal, a new experimental setup has been developed for measuring in real time the radon emission from a zeolitized volcanic tuff. Progressive dehydration phenomena with increasing temperature produce radon emissions two orders of magnitude higher than those measured during rock deformation, microfracturing and failure. In this framework, mineral devolatilization reactions can contribute significantly to produce radon emissions spatially heterogeneous and non-stationary in time, resulting in a transient state dictated by temperature gradients and the carrier effects of subsurface gases. Results from these experiments can be extrapolated to the temporal and spatial scales of magmatic processes, where the ascent of small magma batches from depth causes volatile release due to dehydration phenomena that increase the radon signal from the degassing host rock material

Indoor/outdoor air exchange affects indoor radon – the use of a scale model room to develop a mitigation strategy

Abstract. Indoor/outdoor air exchange on indoor radon concentration was investigated. We evaluated the effect of air extraction versus air introduction at different flow rates on equilibrium 222Rn activity concentrations in a scale model room of 62 cm × 50 cm × 35 cm (inner length x width × height), made of a porous, radium and thorium-rich lithoid ignimbrite (Tufo di Gallese) from Vico volcano (Lazio, central Italy). Experiments were carried either with the inner walls of the chamber covered with a plasterboard shield or without any inner coating. Air introduction was always more effective than air extraction to reduce indoor 222Rn and, in both cases, higher flow rates produced higher 222Rn decreases. The presence of the plasterboard enhanced 222Rn reduction when outdoor air was introduced in the chamber. Main results were that, with plasterboard, maximum reductions of 89.5 % and 25.0 % were obtained introducing and extracting air, respectively; without plasterboard, we found maximum radon decreases of 33.2 % and 26.6 %, namely with air introduction or extraction. The diffusion of 222Rn through the walls of the scale model room was modelled with a modified version of Fick's second law, where a term considering air flow velocity was added. These findings suggested that the combined use of proper coatings on the inner walls of a house and outdoor air introduction at suitable rates are a good strategy to approach radon mitigation actions

Updated CMB constraints on Dark Matter annihilation cross-sections

The injection of secondary particles produced by Dark Matter (DM) annihilation at redshift 100<z<1000 affects the process of recombination, leaving an imprint on Cosmic Microwave Background (CMB) anisotropies. Here we provide a new assessment of the constraints set by CMB data on the mass and self-annihilation cross-section of DM particles. Our new analysis includes the most recent WMAP (7-year) and ACT data, as well as an improved treatment of the time-dependent coupling between the DM annihilation energy with the thermal gas. We show in particular that the improved measurement of the polarization signal places already stringent constraints on light DM particles, ruling out 'thermal' WIMPs with mass less then about 10 GeV.Comment: 4 pages, 1 figur

Long-Term Soil Gas Surveys in the Northern Part of the Modena Province Pre, During and After the 2012 Seismic Sequence

Three geochemical surveys of soil gas (CO2 and CH4 flux measurements, He, H2, CO2, CH4 and C2H6 concentrations) and isotopic analyses (δ13C–CH4, δD–CH4, δ13C–CO2) were carried out as part of a feasibility study for a natural gas storage site in the Modena Province (Northern Italy), during the 2006-2009 period. In May-June 2012, a seismic sequence (main shocks of ML 5.9 and 5.8) was occurred closely to the investigated area. Chemical and isotopic analysis were repeated in May 2012, September 2012, June 2013 and July 2014.In the 2006-2009 period, at the pre-seismic conditions, chemical composition of soil gas showed that the southern part of the studied area is CH4-dominated, whereas the northern part is CO2-dominated. Relatively anomalous fluxes and concentrations were recorded with a spotted areal distribution. Anyway, CO2 and CH4 values are within the typical range of vegetative and of organic exhalation of the cultivated soil. 2012-2013 soil gas results show CO2 values essentially unvaried with respect to pre-earthquake surveys, while the 2014 values highlight an increasing of CO2 flux in the whole study area. On the contrary, CH4 values seem to be on average higher after the seismic sequence, although with a decreasing trend in the last survey (2014). Isotopic analysis were carried out only on samples with anomalous values. The δ13C-CO2 value suggests a prevalent shallow origin of CO2 (i.e. organic and/or soil-derived) probably related to anaerobic oxidation of heavy hydrocarbons. Methane isotopic data (δ13C-CH4) indicate a typical biogenic origin (i.e. microbial hydrocarbon production) of the CH4, as recognized elsewhere in the Po Plain and surroundings. Obtained results highlight a different CO2 and CH4 behaviour before, during and after the seismic events. These variations could be produced by increasing of bacterial (e.g. peat strata) and methanogenic fermentation processes in the first meters of the soil. No hints of deep degassing can be inferred for the study area after the earthquake, as suggested by isotopic analysis. These achieved outcomes constitute the starting point for subsequent geochemical surveys, in order to assess the temporal variations and to better understand the geochemical processes related to the seismic sequence

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

CMB constraints on Dark Matter models with large annihilation cross-section

The injection of secondary particles produced by Dark Matter (DM) annihilation around redshift 1000 would inevitably affect the process of recombination, leaving an imprint on Cosmic Microwave Background (CMB) anisotropies and polarization. We show that the most recent CMB measurements provided by the WMAP satellite mission place interesting constraints on DM self-annihilation rates, especially for models that exhibit a large Sommerfeld enhancement of the annihilation cross-section, as recently proposed to fit the PAMELA and ATIC results. Furthermore, we argue that upcoming CMB experiments such as Planck, will improve the constraints by at least one order of magnitude, thus providing a sensitive probe of the properties of DM particles

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

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