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$$\hbox {CO}_{2}$$ sequestration in geological formations requires specific conditions to safely store this greenhouse gas underground. Different geological reservoirs can be used for this purpose, although saline aquifers are one of the most promising targets due to both their worldwide availability and storing capacity. Nevertheless, geochemical processes and fluid flow properties are to be assessed pre-, during, and post-injection of $$\hbox {CO}_{2}$$ . Theoretical calculations carried out by numerical geochemical modeling play an important role to understand the fate of $$\hbox {CO}_{2}$$ and to investigate short-to-long-term consequences of $$\hbox {CO}_{2}$$ storage into deep saline reservoirs. In this paper, the injection of $$\hbox {CO}_{2}$$ in a deep structure located offshore in the Tyrrhenian Sea (central Italy) was simulated. The results of a methodological approach for evaluating the impact that $$\hbox {CO}_{2}$$ has in a saline aquifer hosted in Mesozoic limestone formations were discussed. Seismic reflection data were used to develop a reliable 3D geological model, while 3D simulations of reactive transport were performed via the TOUGHREACT code. The simulation model covered an area of $$>$$ 100 km $$^{2}$$ and a vertical cross-section of $$>$$ 3 km, including the trapping structure. Two simulations, at different scales, were carried out to depict the local complex geological system and to assess: (i) the geochemical evolution at the reservoir-caprock interface over a short time interval, (ii) the permeability variations close to the $$\hbox {CO}_{2}$$ plume front, and (iii) the $$\hbox {CO}_{2}$$ path from the injection well throughout the geological structure. One of the most important results achieved in this study was the formation of a geochemical barrier as $$\hbox {CO}_{2}$$ -rich acidic waters flowed into the limestone reservoir. As a consequence, a complex precipitation/dissolution zone formed, which likely plays a significant role in the sequestration of $$\hbox {CO}_{2}$$ due to either the reduction of the available storage volume and/or the enhancement of the required injection pressure. [ABSTRACT FROM AUTHOR]

We investigated the speciation of Fe in bulk and in suspended respirable quartz dusts coming from ceramic and iron-casting industrial processes via X-ray absorption spectroscopy, with the aim of contributing to a better understanding of the variability of crystalline silica toxicity. Four different bulk industrial quartz powders, nominally pure quartz samples with Fe contents below 200 ppm, and three respirable dusts filters were selected. Fe speciation was determined in all samples through a coupled study of the X-ray absorption near-edge structure and extended X-ray absorption fine structure regions, operating at the Fe-K edge. Fe speciation revealed common features at the beginning of the different production processes, whereas significant differences were observed on both respirable dusts and bulk dusts exiting from the production process. Namely, a common pollution of the raw quartz dusts by elemental Fe was evidenced and attributed to residuals of the industrial production of quartz materials. Moreover, the respirable samples indicated that reactivity occurs after the suspension of the powders in air. The gravitational selection during the particle suspension consistently allowed us to clearly discriminate between suspended and bulk dusts. On the basis of the obtained results, we provide an apparent spectroscopic discrimination between the raw materials used in the considered industrial processes, and those that are effectively inhaled by workers. In particular, an amorphous Fe oxide, with an unsaturated coordination sphere, can be related to silica reactivity (and health consequences). [ABSTRACT FROM AUTHOR]

The EPR spectrum of Mn2+ in microcrystalline calcite geomaterials (e.g., marbles, travertines) possesses exceptional diagnostic characteristics, allowing to relate samples to their origin (natural/synthetic, inorganic, organogenic, ...) and to evaluate the details of impurities clustering. This information, beyond their mineralogical and geochemical interest, is of paramount importance for environmental, palaeoclimatic, and cultural heritage studies. Accessing the information hidden in the Mn2+ EPR spectrum relies on disentangling spurious self-correlation among spin Hamiltonian parameters in the powder spectrum. In the present study, this goal is achieved through a systematic comparison of the temperature dependencies of four different microcrystalline calcite geomaterials. Accordingly, an assessment of the internal correlation structure of the spin Hamiltonian parameters is provided and the most sensitive discriminating parameters, which are able to mark samples, are identified. It has been found that the spin Hamiltonian parameters useful for discrimination purposes are those which are dependent on the ligand field interaction, whereas the Fermi contact interaction, as well as the spin-spin, spin-phonon, and spin-lattice interactions, are not able to "store" information related to formation processes, nor post-depositional events. This characteristic behavior is ascribed to the occurrence of mosaic structure and to the clustering among Mn2+ and other impurity ions, which are able to induce a strong and variable ligand field interaction. In particular, the proposed method appears fully able to reveal the biogenic origin of microcrystalline calcites and to trace post-depositional events. [ABSTRACT FROM AUTHOR]

n extensive characterisation of the magnetic properties of synthetic powders of kuramite, with formal composition CuSnS, was performed. Powders were investigated through superconducting quantum interference device (SQUID) magnetometry, electron paramagnetic resonance (EPR) spectroscopy, X-ray powder diffraction (XRPD), scanning and transmission electron microscopies (SEM and TEM) and microanalysis. SEM and TEM reveal the presence of nanodimensioned particles. XRPD clearly shows that CuSnS crystallised in a cubic sphalerite-type structural model, in spite of the stannite-type tetragonal structure described for the natural phase. This difference arises from a full random distribution of cations. Synthetic kuramite nanopowders exhibit a marked paramagnetism, originated by the presence of Cu(II), definitely assessed by EPR measurements. Moreover, the overall magnetic behaviour of the sample cannot be simply ascribed to diluted paramagnetism, and this suggests the presence of strong superexchange interactions among Cu(II) ions even at room temperature. The main consequences of these results are the definitive assessment of the chemical formula Cu(I)Cu(II)SnS and of a random distribution of Cu(II), Cu(I) and Sn(IV) ions within the available tetrahedral sites. [ABSTRACT FROM AUTHOR]

Carbon dioxide and CH 4, C6H6 and C7H8 fluxes from the soil cover of Case Passerini landfill site (Florence, Italy) were measured using the accumulation and static closed chamber methods, respectively. Results show that the CH4/CO2, CH4/ C 6H6 and CH4/C7H8 ratios of the flux values are relatively low when compared with those of the ‘pristine’ biogas produced by degradation processes acting on the solid waste material disposed in the landfill. This suggests that when biogas transits through the cover soil, CH4 is affected by degradation processes activated by oxidizing bacteria at higher extent than both CO2 and mono-aromatics. Among the investigated hydrocarbons, C6H6 has shown the highest stability in a wide range of redox conditions. Toluene behaviour only partially resembles that of C6H6, possibly because de-methylation processes require less energy than that necessary for the degradation of C6H6, the latter likely occurring via benzoate at anaerobic conditions and/or through various aerobic metabolic pathways at relatively shallow depth in the cover soil where free oxygen is present. According to these considerations, aromatics are likely to play an important role in the environmental impact of biogas released into the atmosphere from such anthropogenic emission sites, usually only ascribed to CO2 and CH4. In this regard, flux measurements using accumulation and static closed chamber methods coupled with gas chromatography and gas chromatography—mass spectrometry analysis may properly be used to obtain a dataset for the estimation of the amount of volatile organic compounds dispersed from landfills. [ABSTRACT FROM AUTHOR]

Abstract: Geological storage is presently one of the most promising options for reducing anthropogenic emissions of CO2. Among the several projects investigating the fate of CO2 stored at depth, the EnCana''s CO2 injection EOR (Enhancing Oil Recovery) project at Weyburn (Saskatchewan, Canada) is the most important oil production development that hosts an international monitoring project. In the Weyburn EOR Project CO2 is used to increase recovery of heavy oil from the Midale Beds, a Mississippian reservoir consisting of shallow marine carbonate, where about 3 billions standard m3 of supercritical CO2 have been injected since 2000 with an injection rate of 5000 ton/day. In this work the available dataset (bulk mineralogy of the reservoir, gas-cap composition and selected pre- and post-CO2 injection water samples) provided by the International Energy Agency Weyburn CO2 Monitoring & Storage Project has been used in order to: [i)] reconstruct the pre-injection reservoir chemical composition (including pH and the boundary conditions at 62 °C and 15 MPa); [ii)] assess the evolution of the reservoir subjected to CO2 injection and predict dissolution/precipitation processes of the Weyburn brines over 100 years after injection; [iii)] validate the short-term (September 2000–2003) evolution of the in situ reservoir fluids due to the CO2 injection, by comparing the surface analytical data with the composition of the computed depressurized brines. To achieve these goals the PRHEEQC (V2.14) Software Package was used with both modified thermodynamic database and correction for supercritical CO2 fugacity. The oil–gas–water interaction and the non-ideality of the gas phase (with exception of CO2) were not considered in the numerical simulations. Despite intrinsic limitations and uncertainties of geochemical modeling, the main results can be summarized, as follows: 1) the calculated pre-injection chemical composition of the Midale Beds brine is consistent with the analytical data of the waters collected in 2000 (baseline survey), 2) the main reservoir reactions (CO2 and carbonate dissolution) take place within the first year of simulation, 3) the temporal evolution of the chemical features of the fluids in the Weyburn reservoir suggests that CO2 can safely be stored by solubility (as CO2(aq)) and mineral trapping (via dawsonite precipitation). The short-term validation performed by calculating chemical composition of the reservoir fluids (corrected for surface conditions) after the simulation of 3 years of CO2 injection is consistent (error ≤5%) with the analytical data of the wellhead water samples collected in 2003, with the exception of Ca and Mg (error >90%), likely due to complexation effect of carboxilic acid. [Copyright &y& Elsevier]

Abstract: The composition of non-methane volatile organic compounds (hereafter VOCs) in i) the cover soil, at depths of 30, 50 and 70 cm, and ii) gas recovery wells from Case Passerini landfill site, (Florence, Italy) was determined by GC-MS. The study, based on the analysis of interstitial gases sampled along vertical profiles within the cover soil, was aimed to investigate the VOC behaviour as biogas transits from a reducing to a relatively more oxidizing environment. A total of 48 and 63 different VOCs were identified in the soil and well gases, respectively. Aromatics represent the dominant group (71.5% of total VOC) in soil gases, followed by alkanes (6.8%), ketones (5.7%), organic acids (5.2%), aldehydes (3.0%), esters (2.6%), halogenated compounds (2.1%) and terpenes (1.3%). Cyclics, heterocyclics, S-bearing compounds and phenols are ≤1%. In the wells the VOC composition is characterized by higher concentrations of cyclic (7.6%) and S-bearing compounds (2%) and lower concentrations of O-bearing compounds. The vertical distribution of VOCs in the cover soil shows significant variations: alkanes, aromatics and cyclics decrease at decreasing depth, whereas an inverse trend is displayed by the O-bearing species. Total VOC and CH4 concentrations at a depth of 30 cm in the soil are comparable, inferring that microbial activity is likely affecting VOCs at a very minor extent with respect to CH4. According to these considerations, to assess the biogas emission impact, usually carried out on the sole basis of CO2 and CH4 emission rates, the physical–chemical behaviour of VOCs in the cover soil, regulating the discharge of these highly contaminant compounds in ambient air, has to be taken into account. The soil vertical distribution of these species can be used to better evaluate the efficiency of oxidative capability of intermediate and final covers. [Copyright &y& Elsevier]

Abstract: The determination of reduced S species in natural waters is particularly difficult due to their high instability and chemical and physical interferences in the current analytical methods. In this paper a new, rapid and reliable analytical procedure is presented, named the Cd–IC method, for their determination as ΣS2− via oxidation to after chemical trapping with an ammonia–cadmium solution that allows precipitation of all the reduced S species as CdS. The S2−–SO4 is analysed by ion-chromatography. The main advantages of this method are: low cost, high stability of CdS precipitate, absence of interferences, low detection limit (0.01mg/L as SO4 for 10mL of water) and low analytical error (about 5%). The proposed method has been applied to more than 100 water samples from different natural systems (water discharges and cold wells from volcanic and geothermal areas, crater lakes) in central-southern Italy. [Copyright &y& Elsevier]

The oxidation of palladium nanoparticles causes the performance degradation of alkaline direct ethanol fuel cells. Quantifying this oxidation is a task of tremendous importance to design mitigation strategies that extend the service life of catalysts and devices. Here, we show that the Fixed Energy X-ray Absorption Voltammetry (FEXRAV) can provide this information with an in-situ approach. To do so, we have developed a quantification method that assumes the linear response at fixed energy. With this method, we have investigated the oxidation of carbon black-supported palladium electrocatalysts during cyclic voltammetry in the same solution employed as a fuel in the direct ethanol fuel cells. We have shown that up to 38% of the palladium is oxidised at 1.2 V vs. RHE and that such oxidation also happens at lower potentials that the catalyst can experience in real direct ethanol fuel cells. The result of this study is a proof of concept of quantitative FEXRAV. [ABSTRACT FROM AUTHOR]

Obtaining qualitative information about the stress state in the Earth's crust is a challenging task. Typically, direct measurements of crustal stresses are not included in logging programs of geothermal wells, especially while drilling in high enthalpy reservoirs in which temperature conditions often exceed operational limits of the conventional logging equipment. There are a number of methods for assessing stress state of the reservoir, all of which adhered to the petroleum industry, and include sonic logging, hydraulic fracturing, leak-off tests, borehole breakouts analysis and stress indications from core samples studies. Unfortunately, only in a few geothermal wells, these methods are being applied. This is often due to either high investment costs, challenges during core recovery or extremely high reservoir temperatures. Obtaining reliable estimates of parameters such as minimum and maximum horizontal, vertical stresses and pore pressure is vital for ensuring safe drilling operations and increasing the learning curve for the future drilling operations. This study proposes a method for the assessment of crustal stresses using non-direct stress measurements such as circulation losses, multi-arm mechanical caliper logs, and analysis of continuously measured drilling parameters. A MATLAB-based software for assessing minimum and maximum horizontal stresses and breakout orientation from multi-arm mechanical caliper recordings was developed. The proposed methods do not require additional equipment or costs and can be simply extracted from already recorded parameters during drilling. The analysis carried out in this study was based on the results from deep drilling in the Los Humeros Geothermal Field, the third largest field in Mexico, located at the border of Veracruz and Puebla states in the central-eastern part of the country, where the highest recorded temperature recorded was 395°C and hostile reservoir fluids were produced. Throughout almost 40 years of drilling operations in the field, issues related to wellbore instability have been observed. Such complications might be prevented or mitigated in future operations once solid knowledge about reservoir geomechanics is assessed prior to the drilling activity. Additionally, this study proposes an approach for computing the base data needed for the geomechanical modeling on the example of the central part of the Los Humeros Geothermal Field. [ABSTRACT FROM AUTHOR]

In the field of the renewables, a large effort has been devoted in the last years to obtain conventional and new materials for solar energy conversion by using methods which couple a good efficiency and scalability with energetic and environmental concerns. This research has included the so-called kesterites, materials considered interesting for the thin-film solar cell technology, consisting of relatively abundant and harmless elements: Cu3-x-yFexZnySn(S,Se)4. In this study, we undertook the synthesis of members of the kuramite-stannite (Cu3SnS4-Cu2FeSnS4) join by means of a two-step solvothermal approach, able to provide nanocrystalline products in an easy, low-temperature, and fast way. The sample with the highest Fe concentration was characterised by means of a multi-analytical approach, aimed to assess not only its final structural, chemical and micromorphological features, but also the redox speciation of the two transition metal cations, i.e. Cu and Fe, in relation to the overall charge balance. Namely, Electron Paramagnetic Resonance (EPR), Mössbauer and X-ray Absorption Spectroscopy (XAS) and SQUID magnetometry were involved. The main results point out an excellent control of the structural features, and an intermediate Fe content in the sample, leading to the following formula unit: Cu2.2Fe0.48Sn1.2S4. The overall findings of the multi-analytical characterization imply a complex redox balance, where inferring the site occupancy is not trivial; the charge balance, in fact, can only be achieved taking into account the presence of both Fe(III) and vacancies. Moreover, Fe is distributed over two different crystallographic sites. [ABSTRACT FROM AUTHOR]

Studies on hydrothermal fluids circulation and tectonic structures improve the geothermal exploration and exploitation in Iceland. In this paper we present the results of an integrated study (structural, kinematic, fluid inclusions analyses) carried out on a fossil and exhumed geothermal system at Geitafell (SE Iceland), considered an analogue of the active Krafla geothermal system (NE Iceland). Our work is addressed to the relationships between the main structures and the paleo-geothermal fluids circulation at the boundary between the magma chamber (with magma of gabbroic composition) and host rocks, with the aim to get information on those factors having controlled the hydrothermal fluids flow, its storage and the rocks-fluid interaction, at 1–2 km crustal depth. The structural study is mostly based on defining the architecture of mineralized brittle shear zones, where, by measuring length and width of mineralized fractures, permeability was computed in 1.3 × 10−14 m2. As regards the hydrothermal paleo-fluids, fluid inclusions in hydrothermal quartz and calcite, usually associated with epidote and chlorite (i.e., the typical alteration minerals found in Icelandic geothermal fields), recorded a fluid circulation with temperature ranging from about 255 °C to 320 °C, and boiling at the highest temperature. Transient pressure drop, likely related to fracture opening and propagation during tectonic activity, triggered local boiling process testified by fluid inclusions in a calcite sample. During a late evolution the system progressively cooled down to 60–90 °C. Paleo-geothermal fluids were characterized by low-salinity meteoric water, although higher salinity fluids (up to 10.6 wt% NaCl equiv.) entered in the system and mixed with meteoric fluid. In the end, based on results from fluid inclusions, derived fluid density, permeability values and modeling of viscosity, hydraulic conductivity between 2.8 × 10−8 to 1.8 × 10−7 m/s, was also computed within the fluids-channelling brittle shear zones. We finally encourage the key-study of fossil geothermal systems as a tool for getting parameters commonly obtained after drilling in active systems. • The relationship between brittle shear zones and hydrothermal circulation in an exhumed geothermal system, analogue of active system, is described. • Integration among structural and kinematic data of fault surfaces, fluid inclusion analyses on hydrothermal minerals and modeling, permitted us to obtain parameters normally obtained after drilling. [ABSTRACT FROM AUTHOR]

Our society largely relies on inorganic semiconductor devices which are, so far, fabricated using expensive and complex processes requiring ultra-high vacuum equipment. Here we report on the possibility of growing a p-n junction taking advantage of electrochemical processes based on the use of aqueous solutions. The growth of the junction has been carried out using the Electrochemical Atomic Layer Deposition (E-ALD) technique, which allowed to sequentially deposit two different semiconductors, CdS and Cu 2 S, on an Ag(111) substrate, in a single procedure. The growth process was monitored in situ by Surface X-Ray Diffraction (SXRD) and resulted in the fabrication of a thin double-layer structure with a high degree of crystallographic order and a well-defined interface. The high-performance electrical characteristics of the device were analysed ex-situ and show the characteristic feature of a diode., (© 2024 Wiley-VCH GmbH.)

Electrochemical Atomic Layer Deposition (E-ALD) technique has demonstrated to be a suitable process for growing compound semiconductors, by alternating the under-potential deposition (UPD) of the metallic element with the UPD of the non-metallic element. The cycle can be repeated several times to build up films with sub-micrometric thickness. We show that it is possible to grow, by E-ALD, Cu 2 S ultra-thin films on Ag(111) with high structural quality. They show a well ordered layered crystal structure made on alternating pseudohexagonal layers in lower coordination. As reported in literature for minerals in the Cu-S compositional field, these are based on CuS 3 triangular groups, with layers occupied by highly mobile Cu ions. This structural model is closely related to the one of the low chalcocite. The domain size of such films is more than 1000 Å in lateral size and extends with a high crystallinity in the vertical growth direction up to more than 10 nm. E-ALD process results in the growth of highly ordered and almost unstrained ultra-thin films. This growth can lead to the design of semiconductors with optimal transport proprieties by an appropriate doping of the intra metallic layer. The present study enables E-ALD as an efficient synthetic route for the growth of semiconducting heterostructures with tailored properties.