Pore Fillings Research Articles

Sustainable Lignin to Enhance Engineering Properties of Unsaturated Expansive Subgrade Soils

New ways to apply sustainable materials, such as biomass components, are essential for reducing dependence on fossil fuels. This work investigated the engineering properties of unsaturated expansive subgrade soils stabilized by bio-based energy coproducts containing lignin. Lignin is a waste by-product of the paper and pulp industry that is frequently burned. Highway subgrade could consume lignin as an environmentally benign, low-cost, and energy-efficient chemical substance for soil stabilization. Swell and shrink behavior of expansive subgrade soils complicates highway construction and causes damage to existing highways. However, research on the hydromechanical properties and volume change behavior of lignin-stabilized expansive soil is limited, and better insight is required into its unsaturated behavior for safe and economical pavement design practices. In this research, a series of geotechnical laboratory tests were conducted to characterize expansive subgrade soils treated with lignin by determining the Atterberg limits, compaction and consolidation behaviors, swelling characteristics, and water retention properties. The mechanisms influencing the changes in engineering properties of lignin-treated expansive soils were further investigated using soil pH, scanning electron microscopy, X-ray diffraction, and Fourier transform infrared spectroscopy analysis. The study shows that the optimal lignin content contributed to an acceptable degree of soil stabilization. The lignin-based cementing material effectively bonds soil particles together and fills pores, thereby preventing water infiltration into the soil and reducing the swell–shrink potential of stabilized soils.

Diagenesis, facies and palaeocurrent analysis of Upper Rewa Sandstone around Sagar, Central India

The stratigraphic surface represented by a major contact between the Archean Bundelkhand Granite and the extensive Proterozoic Vindhyan sediments is a regional basement cover unconformity. This crystalline–sedimentary interface reflects an intense weathering of continental crust during marine transgression. Three time-transgressive sand deposition events viz. Kaimur, Rewa and Bhander are mainly witnessed during the entire Vindhyan sedimentation. Stratigraphically, the Upper Rewa Sandstone comprises one of these events in the Vindhyan Basin. Considerable progress has been made in interpreting these sandstones as a function of entirely marine process to a combination of tidal–fluvio–eolian activities. All the results have so far been attained on the basis of sedimentary facies, provenance, palaeocurrent analysis, and some of petrography. A distinct differentiation between marine and fluvial components of the Upper Rewa Sandstone still remains uncertain. Here, we use diagenesis as a parameter for the first time along with facies and palaeocurrent analysis to acquire a clear comprehension of marine- and fluvial-dominated processes. The present study spans 27 square kilometer area covering 15 stratigraphic sections with a collection of 571 directional data from the facies specific sedimentary structures, and 28 samples obtained for the thin section analysis.The lower unit of the Upper Rewa Sandstone shows facies association typical of tidal environment, along with polymodal palaeocurrent. These rocks are well sorted and dominantly lithified by authigenic cement. Profuse development of a complex of syntaxial, passive pore fills, and grain replacive cements reflect normally pressured nature of the lower unit sandstones. The upper unit of the Upper Rewa Sandstone however, reveals a facies pattern resembling fluvial processes and unimodal palaeocurrent plot. They exhibit poor sorting, siliceous, and ferruginous matrix, and development of intense stylolites. Since, pressure solution is a dominant mode of lithification; the upper unit rocks therefore, are overpressured. Sand deposition event pertaining to the Upper Rewa Sandstone is found to comprise both marine and fluvial processes. Such a diagenesis based approach can be applied for marking a possible facies based unconformity between genetically different depositional units.

Dynamic CT Imaging in the Laboratory: Characterization of Pore Filling Events in Geological Materials.

Dynamic CT Imaging in the Laboratory: Characterization of Pore Filling Events in Geological Materials.

Rice husk biochar - A novel engineered bio-based material for transforming groundwater-mediated fluoride cycling in natural environments

Biochar, a promising carbon-rich and carbon-negative material, can control water pollution, harness the synergy of sustainable development goals, and achieve circular economy. This study examined the performance feasibility of treating fluoride-contaminated surface and groundwater using raw and modified biochar synthesized from agricultural waste rice husk as problem-fixing renewable carbon-neutral material. Physicochemical characterizations of raw/modified biochars were investigated using FESEM-EDAX, FTIR, XRD, BET, CHSN, VSM, pHpzc, Zeta potential, and particle size analysis were analyzed to identify the surface morphology, functional groups, structural, and electrokinetic behavior. In fluoride (Fˉ) cycling, performance feasibility was tested at various governing factors, contact time (0–120 min), initial Fˉ levels (10–50 mg L−1), biochar dose (0.1–0.5 g L−1), pH (2–9), salt strengths (0–50 mM), temperatures (301–328 K), and various co-occurring ions. Results revealed that activated magnetic biochar (AMB) possessed higher adsorption capacity than raw biochar (RB) and activated biochar (AB) at pH 7. The results indicated that maximum Fˉ removal (98.13%) was achieved using AMB at pH 7 for 10 mg L−1. Electrostatic attraction, ion exchange, pore fillings, and surface complexation govern Fˉ removal mechanisms. Pseudo-second-order and Freundlich were the best fit kinetic and isotherm for Fˉ sorption, respectively. Increased biochar dose drives an increase in active sites due to Fˉ level gradient and mass transfer between biochar-fluoride interactions, which reported maximum mass transfer for AMB than RB and AB. Fluoride adsorption using AMB could be described through chemisorption processes at room temperature (301 K), though endothermic sorption follows the physisorption process. Fluoride removal efficiency reduced, from 67.70% to 53.23%, with increased salt concentrations from 0 to 50 mM NaCl solutions, respectively, due to increased hydrodynamic diameter. Biochar was used to treat natural fluoride-contaminated surface and groundwater in real-world problem-solving measures, showed removal efficiency of 91.20% and 95.61%, respectively, for 10 mg L−1 Fˉ contamination, and has been performed multiple times after systematic adsorption-desorption experiments. Lastly, techno-economic analysis was analyzed for biochar synthesis and Fˉ treatment performance costs. Overall, our results revealed worth output and concluded with recommendations for future research on Fˉ adsorption using biochar.

Influence of Pore Surface Structure and Contents on Shock-Induced Collapse and Energy Localization

The majority of computational efforts in the shockwave driven collapse of porosity focus on idealized pore geometries and structures. These give significant insight into the physical mechanisms in play, but omit some potentially important effects of real energetic materials. To address this, we simulate pore collapse in 1,3,5-triamino-2,4,6-trinitrobenzene (TATB) for four types of pore surfaces and fillings: an idealized cylindrical pore, a pore surface coated with polymer, a melted/amorphous pore surface, and a pore filled with gas molecules. We find that these perturbations to the pore structure result in only minor changes to the highly complex collapse mechanisms. However, significant differences in hotspot temperature are observed, with peak temperatures ranging over several hundred Kelvin. The polymer-coated system has the most effect, lowering the hotspot temperature by 300 K, and also limiting the manifestation of intramolecular strain energy that is known to induce mechanochemistry.

Structure and properties of ZrO2-Al2O3-MgO porous ceramic for biomedical applications

Starch consolidation casting (SCC), which involves pouring starch-containing slurries into an impermeable mould, is a flexible, easy, not harmful, not expensive, and firmly established method for manufacturing ceramic green structures. The procedure depends on the fact that the starch granules, when heated to about 80 °C, start to swell and absorb the water from the ceramic slurries. Following sintering, the starch granules have been completely destroyed by burning, resulting in the formation of porous-structured ceramics. In the current study, porous zirconia-alumina–magnesia (77.5 wt% ZrO2, 2.5 wt% MgO, and 20 wt% Al2O3) ceramic composites have been produced using starch consolidation casting method at different suspension concentration (60, 65, and 70 wt%). Potato or tapioca starches with varying quantities (10, 20, and 30 wt% related to the solid ceramics) were used as a pore and body forming agents. The sintered microstructures were investigated using X-ray diffraction (XRD) and scanning electron microscopy (SEM). Furthermore, the research activity investigates how the apparent density and apparent porosity of the porous ceramic structure that has been produced are affected by the addition of different proportions of starches in different suspension concentrations. The XRD result after sintering reveals monoclinic zirconia, indicating that the tetragonal phase of zirconia is not stabilized by MgO and returns to monoclinic upon cooling. Magnesia does not act as a stabilizer for zirconia, but it is combined with alumina to produce a spinel structure. Maximum apparent porosity value of around 73% were demonstrated for porous-structured ceramics made with (30 wt%) potato starch and (60 wt%) suspension concentration. The SEM analysis of porous-structured ceramics revealed the presence of pore fills in the shape of miniature sintered ceramic shells within the pores. These shells form throughout the drying and burn-out processes, when the starch granules undergo a process that causes them to shrink. For nominal starch quantities of approximately 10 wt%, starch swelling is noticeable, and the pores left behind by sintering are bigger than the starch granules. Swelling is limited for greater amounts of starch by the amount of available space and/or water, and the matrix shrinkage that occurs during sintering more than compensates for the swelling impact, resulting in ceramic pores much smaller than the initial starch granule size. SEM and high-pressure mercury porosimetry results indicated that the prepared porous-structured ceramics have a bimodal pore structure. The maximum compressive strength at around 15.87 MPa for a sample containing 10 wt% tapioca starch and 70 wt% suspension concentration. Compressive strength drastically reduced when starch content increased from 10 to 30 wt% and suspension concentration reduced from 70 to 60 wt%.

The diagenesis and evolution of conglomeratic reservoirs in the Wutonggou Formation in the Yingyeer area

The conglomeratic reservoirs of the Permian Wutonggou Formation in the Yingyeer area of the Turpan–Hami Basin are key petroliferous horizons, with enormous potential for hydrocarbon exploration. Existing studies on the conglomeratic reservoirs in this area mainly focus on the sedimentary environment and sand body distribution, while few of them concern the diagenesis and evolution of the conglomeratic reservoirs, leading to deficient knowledge about relevant mechanisms. By comprehensively utilizing the data from ordinary and casting thin section identification, the x-ray diffraction analysis of whole rock and clay, scanning electron microscopy, and other analyses and assays, this study analyzed and investigated the petrological characteristics, diagenetic types, and characteristics, and diagenetic evolutionary stages and mechanisms of the conglomeratic reservoirs of the Permian Wutonggou Formation in the Yingyeer area. The study results are as follows. Under the influence of sedimentary provenances, tectonic evolution, and paleogeomorphology, the conglomeratic reservoirs of the Permian Wutonggou formation have low clastic grain maturity and low structural maturity, suggesting proximal provenances. The reservoirs are subjected to various diagenesis, including carbonate cementation, which fills pores and throats; compaction as a major factor leading to poor reservoir quality, and dissolution, which significantly improves the reservoir properties. The conglomeratic reservoirs in the Wutonggou formation are generally in substage A of the middle diagenetic stage. The diagenetic evolution of the reservoirs generally underwent early mechanical compaction, calcite precipitation, secondary quartz overgrowth, the injection of organic fluids, the dissolution of feldspars and lithic grains, the transformation of clay minerals, and calcite cementation in sequence. Hydrocarbon charging mainly occurred during the late Middle Jurassic and was greatly influenced by early compaction and dissolution.

Investigating the influence of pore size, pore fluid and wavelength on backscattering images with sintered glass filter matrices as experimental models

Laser backscattering imaging (LBI) is an economic, energy-saving method, which can be applied to characterise bio-organisms in postharvest processes. When applying LBI to horticultural crops, scientists seldom report the cell size of their samples, and often consider the scattering coefficient as constant. The objective of this research was to investigate the influence of pore size, the pore filling for different solutes and concentrations, and wavelength under controlled conditions. Porous glass discs with five different pore diameters from 1 to 160 µm were used as reproducible experimental models for the experiment. NaCl aqueous solutions (0, 1, 2, 3 and 4 mol/L) and NaH2PO4 aqueous solutions (0, 0.8, 1.6, 2.4 and 3.2 mol/L) were applied as pore fills. The LBI system used laser modules at three wavelengths (405, 635, 780 nm). The results revealed that three of the four investigated experimental factors influence LBI, specifically: (i) the pore diameter, (ii) the solutes and (iii) their concentrations. In contrast, the three wavelengths applied did not show clear differences in the LBI patterns. Thus, when applying LBI on fruit for example, the cell size at different depths from the fruit surface needs to be carefully considered.

Relationship between normalized permeability and resistivity index in hydrate-bearing sediments: fractal model and numerical simulation

SUMMARYPermeability is a critical factor in evaluating the fluid flow capacity and production performance of natural gas hydrate reservoirs. The similarity of electrical conduction and hydraulic flow makes it possible to predict reservoir permeability using electrical data. Clarifying the relationship between the permeability and resistivity of sediments with different hydrate growth habits contributes to the efficient exploration and development of natural gas hydrate resources. In this work, normalized permeability and the resistivity index models for grain-coating (GC) and pore-filling (PF) hydrates are developed based on the fractal geometry theory, forming a new relationship between normalized permeability and resistivity index. The empirical exponent is determined by fractal dimension. Meanwhile, we selected five sets of 3-D computed tomography (CT) images of quartz sand with different particle sizes, GC and PF hydrate digital rocks are constructed using random simulation methods. The numerical simulation of permeability and resistivity index is carried out, based on the pore microstructure images, the box counting method was used to calculate the fractal dimension and analyse the relationship between pore space and transport paths. Furthermore, the pore radius, throat radius and pore connection number are extracted through the pore network method to study the evolution of pore space. The results show that the tortuosity fractal dimension is a critical parameter in the relationship between normalized permeability and resistivity index. The proposed analytical expressions are validated by laboratory and well log data, and the exponent ranges cover existing hydrate permeability–resistivity index data. The models provide the possibility to predict the normalized permeability of hydrate reservoirs based on electrical data alone.

The Effects of Diatomite as an Additive on the Macroscopic Properties and Microstructure of Concrete

Diatomite is a siliceous sedimentary rock containing amorphous silica, which can be used as a green mineral admixture to improve the properties of concrete. This study investigates the affecting mechanism of diatomite on concrete performance by macro and micro tests. The results indicate that diatomite can reduce the fluidity of concrete mixture and change its water absorption, compressive strength, resistance to chloride penetration (RCP), porosity, and microstructure. The low fluidity of concrete mixture containing diatomite can reduce workability. With increasing diatomite as partial replacement for cement in concrete, water absorption of concrete decreases before increasing, while compressive strength and RCP rise first and then drop. When diatomite is added to the cement at a content of 5% by weight, the concrete has the lowest water absorption and the highest compressive strength and RCP. Through the mercury intrusion porosimetry (MIP) test, we determined that the addition of 5% diatomite reduces the porosity of concrete from 12.68% to 10.82% and changes the proportion of pores with different sizes in concrete, the proportion of harmless and less harmful pores increases, and the proportion of harmful pores reduces. Based on the microstructure analysis, the SiO2 in diatomite can react with CH and produce C-S-H. C-S-H is responsible for developing concrete because it fills pores and cracks, forms a platy structure, and makes the concrete much denser, thereby improving its macroscopic performance and microstructure.

Clarification of the Effects of Oxygen Containing Functional Groups on the Pore Filling Behavior of Discharge Deposits in Lithium–Air Battery Cathodes Using Surface-Modified Carbon Gels

In lithium–air batteries (LABs), controlling the characteristics of the Li2O2 deposited during discharging can lead to the reduction of the large overpotential required for charging. The large overpotential is one of the most significant problems that needs to be solved to improve the cycle performance of LABs. Here, we focused on the effects of functional groups in the cathode carbon on the characteristics of the Li2O2 deposited during discharging and the cathode performance of LABs. In this study, 4 types of carbon gels (CGs) were prepared using different treatment methods to modify their surface properties. The types and amounts of oxygen-containing functional groups (OCFGs) existing within the CGs were clarified along with the number of edge H’s by a high-sensitivity temperature-programmed desorption (TPD) technique. The results of N2 adsorption analysis of discharged CGs suggested that, by increasing the number of OCFGs from 0.40 to 1.80 mmol g–1 through acid treatment, the ratio of Li2O2 deposited within the mesopores of the porous carbon particles can be increased from 1% to 60%. This significant change in the manner of Li2O2 deposition led to the reduction of the charging overpotential. Side reactions that are thought to deteriorate cycle performance tended to proceed in CGs having a large number of OCFGs. This negative effect could be reduced by removing carboxyl groups in the CGs through simple heat treatment at 300 °C in an inert atmosphere. Our study clarified the critical roles of OCFGs in the cathode during the discharging and charging of LABs. The obtained knowledge can be utilized for the development of a high-performance cathode for LABs.

Characteristics of Gas Seepage and Pore Structure Response in CO2-ECBM Process of Low Permeability Coal Seam

CO2-ECBM is a method of enhanced coalbed methane extraction followed by cutting greenhouse gas emissions and new energy development. In order to reveal the characteristics of gas flow in porous media and the pore structure response characteristics of coal rocks, the experiments were carried out to simulate the process of CO2 displacement of N2 at a buried depth of 900 m, including monitoring the changes in gas permeability and strain of coal samples along with a comparison of the pore structure of low-temperature liquid nitrogen adsorption on coal samples both before and after displacement were both done. The findings of the experiment are listed below. The N2 permeability of the LiuZhuang sample ranges from 0.0008mD to 0.0014mD, whereas the permeability of QiDong is around 0.0003mD. With an increase in gas injection duration and an expansion of the coal matrix for N2 adsorption, the permeability steadily decreases. The efficient stress compression of the coal pore fracture structure during sample preparation and testing avoids the visible fracture region, which results in poor permeability. The displacement stages of CO2 can be divided into three phases. Free nitrogen flows from the end of the position and the permeability diminishes during the phase of free nitrogen. When CO2 is introduced into the penetration stage, the permeability tends to rise, however when there is no penetration, the permeability test values are frequently low. During the CO2 steady displacement phase, gas permeability gradually declines. Axial and radial strains are progressively raised during the initial stage of the CO2 injection whereas they are gradually reduced during the initial stage of the N2 injection. While CO2 is continuously supplied through the coal body stage, there are modest axial and radial strain changes. The axial and radial stresses are stabilized by the CO2 displacement. The overall pore volume of the coal significantly rises following the displacement. The increase part of the pore volume is primarily focused on the pore of absorption and filling (aperture < 10nm), whereas the decreased part is mainly concentrated in the diffusion pore of the Fick type and the permeability part (aperture > 50nm). The increased in pore volume ratio surface area is centered mostly in the fill pore region (aperture 10 nm) and is four times greater than it was before the displacement. The CO2 injection exerts an expansion impact on the adsorptionfilled and diffusion pores during the CO2-ECBM process, whereas the compression effect on the percolation pores results in a reduction in permeability.

Characterizing Gas Hydrate-Bearing Marine Sediments Using Elastic Properties—Part 2: Seismic Inversion Based on a Pore-Filling–Solid Matrix Decoupling Scheme

Characterizing gas hydrate-bearing marine sediments using seismic methods is essential for locating potential hydrate resources. However, most existing pre-stack seismic inversion methods estimate the properties of sediments containing gas hydrates without considering specific characteristics associated with gas hydrate occurrences. In the present study, a pore-filling–solid matrix decoupling amplitude variation with offset (AVO) formula is proposed to represent seismic reflectivity in terms of properties associated with gas hydrates. Based on the rock physics relationships of solid substitution, the parameters introduced into the decoupling AVO equation estimate the concentration of gas hydrates with different occurrences, including pore fillings mixed with water and solid components forming part of the dry sediment frame. A theoretical model test indicates that seismic attributes obtained with the decoupling AVO inversion are superior to the conventional wave velocities-related properties in predicting gas hydrate saturations. A realistic model test further validates the applicability of the proposed method in characterizing a gas hydrate system with varying concentrations and layer thickness. By adjusting the tuning parameters, the configurations and concentrations of the gas hydrate system can be identified using the obtained attributes. Therefore, the presented method provides a useful tool for the characterization of gas hydrate-bearing sediments.

Characterizing Gas Hydrate–Bearing Marine Sediments Using Elastic Properties—Part 1: Rock Physical Modeling and Inversion from Well Logs

Gas hydrates are considered a potential energy source for the future. Rock physics modeling provides insights into the elastic response of sediments containing gas hydrates, which is essential for identifying gas hydrates using well-log data and seismic attributes. This paper establishes a rock physics model (RPM) by employing effective medium theories to quantify the elastic properties of sediments containing gas hydrates. Specifically, the proposed RPM introduces critical gas hydrate saturation for various modeling schemes. Such a key factor considers the impact of gas hydrates on sediment stiffnesses during the dynamic process of the gas hydrate accumulating as pore fillings and part of the solid components. Theoretical modeling illustrates that elastic characteristics of the sediments exhibit distinct variation trends determined by critical gas hydrate saturation. Numerical tests of the model based on the well-log data confirm that the proposed technique can be employed to rationally predict gas hydrate saturation using the elastic properties. The compressional wave velocity model is also developed to estimate the gas hydrate saturation, which gives reliable fit results to core measurement data. The proposed methods could improve our understanding of the elastic behaviors of gas hydrates, providing a practical approach to estimating their concentrations.

Effect of Pore Filling on Properties of Nanocomposites LiClO4-MIL-101(Cr) with High Ionic Conductivity.

Experimental data on nitrogen adsorption, pellets density and ionic conductivity of nanocomposite solid electrolytes (1−x)LiClO4–xMIL-101(Cr) were interpreted in frames of the model of the composite in which the lithium salt fills the pores of a metal-organic framework MIL-101(Cr). According to the model, the concentration of lithium salt located in the pores reaches a maximum at the concentration x = xmax which is defined by a ratio of the molar volume of LiClO4 and the total volume of accessible pores in the MIL-101(Cr) framework. The model allows one to describe the dependences of pore volume and pellet density on the concentration of MIL-101(Cr). Conductivity of the composites were successfully described by two separate mixing equations for concentration ranges x < xmax and x > xmax. In the first concentration region x < xmax, the composite may be regarded as a mixture of LiClO4 and MIL-101(Cr) with completely filled pores accessible for LiClO4. At x > xmax, the total amount of lithium perchlorate is located in the pores of MIL-101(Cr) and occupies only part of the volume of the accessible pores. It was found that xmax value determined from the concentration dependence of conductivity (xmax = 0.06) is noticeably lower than the corresponding value estimated from adsorption data (xmax = 0.085) indicating a practically complete filling the pores of MIL-101(Cr) in the composite pellets heated before conductivity measurements.

Pore Structure Modification of Pitch‐Derived Hard Carbon for Enhanced Pore Filling Sodium Storage

The pore structure of hard carbon has an important influence on its sodium storage performance. Herein, pitch‐derived hard carbons with different pore structures have been prepared via the combination of physical activation and vapor carbon coating. It reveals that the open pores favor the slope capacity while the closed pores can promote the plateau capacity, which consolidates the pore‐filling mechanism of hard carbon during the sodium storage in the plateau region. HC1400‐5 h@PP with rich closed micropores can deliver a reversible specific capacity of 299.1 mAh g−1 with initial Coulombic efficiency of 81.1%. The plateau capacity accounts for 66.6% of the total capacity. Ex situ Raman and galvanostatic intermittent titration investigations show that there exists an energy barrier for the Na deposition in the closed pores, leading to the rapid decay of plateau capacity at a high current density.

Effect of pore size on the magnetic properties of emim FeCl4 confined in the pores of SBA-15

The magnetic moments of a magnetic ionic liquid, emim FeCl4, confined in the micropores and mesopores of SBA-15 with two different fractional pore fillings were measured over the temperature range of 1.8–300 K. The slightly negative Weiss temperature of the bulk decreased to −67 K above the high-temperature region more than 120 K in the system both micropores and mesopores filled. X-ray scattering profiles of the confined emim FeCl4 revealed that the magnetic anions confined in mesopores are loosely bounded to the pore walls, thus have unique magnetic properties.

Sensitivity and Uncertainty Analysis for Natural Gas Hydrate Production Tests in Alaska

The Japan Research and Development Consortium for Pore Filling Hydrate in Sand (MH21-S), the U.S. Department of Energy National Energy Technology Laboratory (DOE NETL), and the U.S. Geological Survey (USGS) are planning a long-term production test from gas hydrate (methane hydrate) bearing reservoirs in the Prudhoe Bay Unit in northern Alaska. Prediction of gas and water production using 2D reservoir simulation models can be very useful for decision-making for long-term production testing. However, the input parameters applied to the simulation model, which are essentially based on the most likely values obtained from the well-log interpretation and core sample measurements of the Hydrate-01 stratigraphic test well (STW), have some degrees of uncertainty. In this study, to evaluate the impact of uncertainties in the input model on the prediction results of gas and water production as well as to analyze how each input parameter contributes to the uncertainties of prediction results, we conducted uncertainty analysis and parameter sensitivity analysis based on two different methods (the regression-based method and the Sobol’ method). The sensitivity analyses reveal that the parameters regarding relative permeability (exponential of the gas relative permeability (Ng) and residual gas saturation (Sgcr)) and the intrinsic/effective permeability of the lower B1 sand significantly contribute to the uncertainties of the gas and water production predictions. In addition, the uncertainty analyses reveal that the P50 value of cumulative gas production can result in less than the reference case with the most likely values for the input parameters due to the uncertainty of Ng. These results indicate that reducing the uncertainties of gas relative permeability and residual gas saturation is essential for more reliable numerical simulations both for prediction of test well performance and subsequent history matching of field test results.

Systematic variations in trace element composition of pyrites from the 26°S hydrothermal field, Mid-Atlantic Ridge

Variations in trace element composition of pyrites in inactive chimneys from the SMAR 26°S hydrothermal field provide important insights into the genesis and evolution of volcanic-hosted hydrothermal mineralization. Petrographic observations of zoned chimney samples integrated with in-situ LA-ICP-MS analysis of morphologically different pyrites allowed the assessment of fluid evolution during the chimney growth. Pyrite varieties precipitated with increasing temperatures from the outermost chimney wall (zone A) through the intermediate zone (zone B) to the inner zone (zone C). At the late mature stage, pyrite precipitates as interstice pore fillings. The distribution of trace elements in pyrites across the chimney indicates a strong dependence on time, temperature, and associated sulfide minerals. Variations in the trace elements composition of the different pyrite varieties indicate that the hydrothermal system evolved from low-temperature low-chloride liquid-dominated fluids (enriched in Zn, Cd, Tl, Ag, Pb, Mn, Mo, and V) to higher temperature, vapor-dominated fluids (Cu, Au, Te, and Bi), and then to high-temperature fluids (Co and Se). In the waning stage of the hydrothermal system, circulating hot fluids in auxiliary conduits were depleted in most trace elements. The systematic variations in trace element compositions of hydrothermal fluids induced by changes in physicochemical conditions are properly governed by the law of normal distribution of trace elements. The LA-ICP-MS time-depth analysis indicate that Cu, Zn, Cd, Tl, Ag, Te, and Bi are related to micro-/nano-inclusions, whereas Co, Se, and Mo may occur as substitutions in pyrite lattice. The As, Pb, Au, and Sb show both modes of occurrences as substitutions and as inclusions. Adsorbed films on pyrites control the distribution of V and Mo. The incorporation processes of trace elements in pyrites change with fluid evolution during the chimney growth: trapping of micro-/nano-inclusions and surface adsorption is seen more frequently at the low-temperature stage, and lattice substitution mainly at the elevated temperature stages.

Structural and chemical changes in pyrogenic organic matter aged in a boreal forest soil

Pyrogenic organic matter (PyOM) is formed during wildfires and prescribed burnings or produced intentionally in the form of biochar for soil amendment purposes. It is attracting a growing scientific and practical interest due to its important role in the global carbon cycle and agronomic applications as a soil enhancer. Most of the studies on the physicochemical properties of PyOM have been conducted using fresh biochars even though the characteristics of PyOM are expected to alter due to aging processes in soil environment. In this paper, we report the results of a study that utilized X-ray microtomography and elemental analysis to investigate the chemical and structural changes in the PyOM formed during prescribed burning events and aged thereafter for 1–71 years in a boreal forest soil. Our results indicate that changes in elemental composition occurred at decadal timescales, and an apparent steady state was reached ca. 30 years after PyOM formation and exposure to the environment. At such timescales, PyOM was able to retain its porous structure originating from the cellular structure of the initial wood tissues. However, structural analysis revealed several effects of aging on the pore structure, such as the formation of surface coating layers, pore fillings, and fractures. These changes may alter pore size distribution and accessibility of the pores and further alter the influence of PyOM on soil functions, such as the transfer and retention of water and nutrients in PyOM pores.