Crystalline Minerals Research Articles

[formula omitted] Affects the crystalline calcium silicate hydrate minerals synthesized by fly ash-based silicon extraction solution and lime milk

When extracting amorphous silicon from fly ash using a strong alkaline solution, other elements such as Al also enter the silicon extraction solution in the form of AlOH4−. To systematically investigate the impact of AlOH4− on the synthesis of typical calcium silicate hydrate crystals in a silicon extraction solution, a specific amount of AlOH4− was added to the silicon extraction solution, and calcium silicate was hydrothermally synthesized at 90℃ and 230℃. Scanning electron microscopy (SEM) and Brunner−Emmet−Teller (BET) analysis revealed that with the increasing in AlOH4− content, microporous calcium silicate gradually loses its microporous morphology. While the specific surface area shows no significant change, the median pore diameter first increases from 1.47 nm to 1.58 nm and then decreases to 1.55 nm. The xonotlite fibers underwent a gradual refinement, diminishing from 0.28 to 0.15 µm. Simultaneously, the specific surface area increases from 28.87 to 56.8 m2/g. At an AlOH4− concentration of 3 mol/L, the microscopic morphology transforms into a sheet-like structure. X-ray diffraction (XRD) analysis reveals that AlOH4− promotes the formation of tobermorite while inhibiting the further development of calcium silicate. Additionally, Fourier transform infrared spectroscopy (FTIR) and nuclear magnetic resonance indicate that Al can replace Si in the calcium silicate hydrate system, primarily substituting positions the Q2 and Q3 sites. Qualitatively, it is suggested that with the increasing incorporation of Al, the polymerization degree of the silicon-oxygen tetrahedra decreases. According to experimental results, the concentration of AlOH4− should be below 0.05 mol/L when synthesizing microporous calcium silicate hydrate and less than 0.2 mol/L when synthesizing fibrous xonotlite-type calcium silicate hydrate.

Recycling of flotation residual carbon from coal gasification fine slag through thermal combustion reaction: Insight into the spatial and temporal multi-scale evolution of typical heavy metals

The necessity for a fundamental comprehension of the migration and transformation patterns of heavy metals in the combustion reaction process is paramount to ensure the effective and targeted prevention and control of heavy metal pollution in the context of large-scale energy utilization of waste coal gasification fine slag. This study aims to reveal the fate of typical heavy metals during the combustion reaction of coal gasification fine slag to provide valuable insight for its clean secondary use. In this work, the thermal combustion reactivity of coal gasification fine slag was initially enhanced through froth flotation, and then the spatial and temporal multi-scale evolution of heavy metals in the flotation carbon-rich fraction was investigated by a series of analytical experiments. The results demonstrate a strong correlation between the volatility of typical heavy metals and the combustion reaction process of the flotation carbon-rich fraction. The volatility of V, Ni, Cu, Zn, and Pb is consistently high, of which the volatility of Zn and Pb is consistently above 50%, while the volatility of Cr, Mn, and Ba exhibits greater temperature sensitivity. As the reaction proceeds, the specific surface area of the solid residue expands, and then the smooth and dense mineral particles dissolve into each other to form a cluster structure simultaneously with the collapse of the pore structure, resulting in the volatility of the heavy metals firstly increasing and then decreasing. Furthermore, alkali metals and alkaline earth metal compounds are effective carriers of Cr, Mn, and Ba in the bottom residual. Additionally, the type and number of crystalline minerals in the bottom residual gradually increase as the reaction progresses. This results in the gradual conversion of the heavy metals bound to unstable carbonate minerals and sulphones into more stable chemical forms. The findings provide novel theoretical support and technical guidance for the environmentally sound and efficient utilization of residual carbon in the waste coal gasification fine slag.

Crystalline iron oxide mineral (magnetite) accelerates methane production from petroleum hydrocarbon biodegradation

Methane (CH4) emissions are a factor in climate change; in addition, CH4 production may affect reclamation of fluid fine tailings (FFT) in tailings ponds, and end-pit lakes (EPLs). In laboratory cultures, we investigated the effect of crystalline iron mineral (magnetite) on CH4 production from the biodegradation of hydrocarbons added to FFT collected from methanogenically more and less active sites in a demonstration EPL. Magnetite enhanced CH4 production from both sites, having a greater effect in more active FFT, where it increased the CH4 production rate as much as 48% (from 6.67 μmol d−1 to 9.87 μmol d−1) compared to FFT without magnetite. Correspondingly, magnetite hastened biodegradation of hydrocarbons (monoaromatics, n-alkanes and iso-alkanes), with a pronounced effect on o-xylene, ethylbenzene, m/p-xylenes, n-octane, n-nonane, and 2-methyloctane, where biodegradation rates increased by 46, 117, 11, 45, 28 and 37%, respectively, compared to FFT without magnetite. Little FeII was produced, suggesting that magnetite is not being used as an electron acceptor but rather functions as a conduit for electron transfer. Thus, magnetite may be a suitable amendment to enhance bioremediation of anaerobic environments contaminated with hydrocarbons. Importantly, our observations imply that magnetite may increase CH4 emissions from terrestrial ecosystems, thus affecting carbon budget estimations.

Assessment of submicron bone tissue composition in plastic-embedded samples using optical photothermal infrared (O-PTIR) spectral imaging and machine learning

Understanding the composition of bone tissue at the submicron level is crucial to elucidate factors contributing to bone disease and fragility. Here, we introduce a novel approach utilizing optical photothermal infrared (O-PTIR) spectroscopy and imaging coupled with machine learning analysis to assess bone tissue composition at 500 nm spatial resolution. This approach was used to evaluate thick bone samples embedded in typical poly(methyl methacrylate) (PMMA) blocks, eliminating the need for cumbersome thin sectioning. We demonstrate the utility of O-PTIR imaging to assess the distribution of bone tissue mineral and protein, as well as to explore the structure-composition relationship surrounding microporosity at a spatial resolution unattainable by conventional infrared imaging modalities. Using bone samples from wildtype (WT) mice and from a mouse model of osteogenesis imperfecta (OIM), we further showcase the application of O-PTIR spectroscopy to quantify mineral content, crystallinity, and carbonate content in spatially defined regions across the cortical bone. Notably, we show that machine learning analysis using support vector machine (SVM) was successful in identifying bone phenotypes (typical in WT, fragile in OIM) based on input of spectral data, with over 86% of samples correctly identified when using the collagen spectral range. Our findings highlight the potential of O-PTIR spectroscopy and imaging as valuable tools for exploring bone submicron composition.

Influences and mechanisms of iron input for methane productions in peatlands.

Atmospheric deposition provides a stable iron source for peatlands. The influences of Fe input on methane (CH4) productions and the underlying mechanisms remain unclear. We conducted a microcosm experiment with peat sediments collected from the Qinghai-Tibet Plateau of China to explore the effects of ferrihydrite reductionfor CH4 productions in peatlands by using geochemical analyses including 57Fe Mössbauer spectroscopy and three-dimensional fluorescence spectroscopy (3D-EEM) in combination with high-throughput sequencing of 16S rRNA and real-time fluorescence quantitative PCR (qPCR). Results showed that ferrihydrite reduction significantly increased CH4 production, being 30 times of that under the control. Selective extractions for iron oxides and 57Fe Mössbauer spectroscopy measurements revealed that no crystalline secondary iron minerals were formed during the ferrihydrite reduction process. The addition of ferrihydrite enhanced the degradation of dissolved organic matter (DOM) in peat soil, resulting in a reduction in the concentration of dissolved organic carbon (DOC). Furthermore, the relative abundance of typical fermentative microorganisms in peat sediments, including Acidobacteriota and Bacteroidota, significantly increased. Such a result indicated that reduction of ferrihydrite accelerated organic matter decomposition and increased substrate concentration required for methanogenesis. Furthermore, a co-increase in relative abundance of Geobacter, Geothrix, and Methanobacterium in the ferrihydrite-amended group suggested a potential synergistic interaction that may promote the CH4 production. Our results demonstrated that ferrihydrite reduction could significantly enhance CH4 production and play a vital role in regulating CH4 emissions in peatlands.

Characterization of regolith-hosted rare earth element deposits using reflectance spectroscopy: Framework towards an efficient and reliable field exploration tool

With a growing demand for the rare earth elements (REE), exploration of regolith-hosted REE resources worldwide has been thriving in recent years and development of a rapid and reliable field-based tool will greatly facilitate the survey and exploration. In this study, we use visible and short-wave infrared (VNIR-SWIR) reflectance spectroscopy to comprehensively evaluate the applicability of the technique to explore regolith-hosted REE resources, exemplified by three representative regolith-hosted REE deposits in China. Neodymium among the REE shows reliably detectable spectral features in the VNIR-SWIR spectroscopy down to concentrations of 10–50 ppm in field samples with heterogeneous mineral grain sizes. The Nd spectral intensity of electronic transition at the band of ∼800 nm is correlated with bulk Nd concentrations and can be used as semi-quantitative indicators for the Nd concentrations, thereby the total REE in regolith. Moreover, VNIR-SWIR spectroscopy is demonstrated to be capable of delineating favorable ore-bearing mineralogy by characterizing the abundance and type of clay minerals and Fe (oxyhydr)oxides, and the crystallinity of kaolinite-group minerals. However, the Nd spectral features of samples with high bulk Fe2O3 contents (>3 wt%) are significantly masked due to overlapping by the strong absorption features of ferric (oxyhydr)oxides. VNIR-SWIR spectroscopy is deemed to be applicable to the exploration of regolith-hosted REE resources developed from Fe-poor felsic rocks.

Analysis of The Crystalline Phases of The Mineral Rutan By Means of The X-Ray Diffraction Technique

Objective: This work aims to analyze a sample of the mineral Rutana, composed of two crystalline phases of titanium dioxide (TiO2): rutile and anatase, using the X-ray diffraction technique. Theoretical reference: In 1914, the German physicist Max von Laue, using a CaSO4 crystal, successfully achieved the diffraction of X-rays. Crystalline solids, such as CaSO4, consist of regular arrangements of atoms with interatomic spacings of the order of 0.1 -1.0Å, that is, with the same order of magnitude as the wavelength of X-rays. Due to the periodic nature of the internal structure of the crystals, it was possible for them to act as a three-dimensional diffraction grating, providing science with a new method for indirect investigation of the internal structure of materials: the X-ray diffraction (XRD) technique. Methodology: In this technique, a finely ground crystalline powder of a material is placed in the path of a monochromatic x-ray beam. This material, composed of a large number of small crystallites, are randomly oriented. Diffraction occurs from planes of the crystallites that are oriented at the correct angle to fulfill the Bragg condition, in such a way that localized peaks of the same intensity as the diffracted beams are formed. Results and discussion: Based on the intensity, angles and width of the diffraction peaks, the mass percentages of each of the mineral's crystalline phases were obtained: rutile (62.08%) and anatase (37.92%). Research Implications: This work presents a contribution to future research related to the chemical characterization of initially unknown samples, by providing a comprehensive and representative theoretical framework related to the XRD technique. Originality/value: This study presents practical contributions to the literature related to the application of the XRD technique in the characterization of materials.

The role of collagen and crystallinity in the physicochemical properties of naturally derived bone grafts

Abstract Xenografts are commonly used for bone regeneration in dental and orthopaedic domains to repair bone voids and other defects. The first-generation xenografts were made through sintering, which deproteinises them and alters their crystallinity, while later xenografts are produced using cold-temperature chemical treatments to maintain the structural collagen phase. However, the impact of collagen and the crystalline phase on physicochemical properties have not been elucidated. We hypothesized that understanding these factors could explain why the latter provides improved bone regeneration clinically. In this study, we compared two types of xenografts, one prepared through a low-temperature chemical process (Treated) and another subsequently sintered at 1100 °C (Sintered) using advanced microscopy, spectroscopy, x-ray analysis, and compressive testing. Our investigation showed that the Treated bone graft was free of residual blood, lipids, or cell debris, mitigating the risk of pathogen transmission. Meanwhile, the sintering process removed collagen and the carbonate phase of the Sintered graft, leaving only calcium phosphate and increased mineral crystallinity. Micro computed tomography revealed that the Treated graft exhibited an increased high porosity (81%) and pore size compared to untreated bone, whereas the Sintered graft exhibited shrinkage, which reduced the porosity (72%), pore size, and strut size. Additionally, scanning electron microscopy (SEM) displayed crack formation around the pores of the Sintered graft. The Treated graft displayed median mechanical properties comparable to native cancellous bone and clinically available solutions, with an apparent modulus of 166 MPa, yield stress of 5.5 MPa, and yield strain of 4.9%. In contrast, the Sintered graft exhibited a lower median apparent modulus of 57 MPa. It failed in a brittle manner at a median stress of 1.7 MPa and strain level of 2.9%, demonstrating the structural importance of the collagen phase. This indicates why bone grafts prepared through cold-temperature processes are clinically favourable.

Control mechanism of short-term fertilization with cattle manure on the release characteristics of soil colloids in farmland: grain size and physicochemical properties

BackgroundUnderstanding the release characteristics of soil colloids is a prerequisite for studying the co-transport of colloids and pollutants in subsurface environment. As a crucial agricultural management measure, fertilization not only alters the material composition of farmland soil, but also significantly regulates the properties and release patterns of soil colloids. This study systematically investigated the regulatory mechanism of short-term cattle manure fertilization on the macroscopic release and microscopic properties of soil colloids with different particle sizes, providing a theoretical foundation for subsequent research on the fate and transport of agricultural non-point source pollutants.ResultsThe colloids in natural agricultural soil primarily consist of inorganic components. Graded extraction of the colloids has revealed that the combined proportion of colloids with particle sizes of 1–2 μm and 0.45–1 μm accounts for approximately 80.5%. Applying cattle manure inhibits the release of soil colloids, and the content of large particle size (1–2 μm) components increases. The content of organic colloids is increased due to the high total organic carbon (TOC) in cattle manure, particularly those with a particle size less than 1 μm. The characterization of organic colloid components revealed a significant increase in aromatic carbon and oxygen-containing functional groups, while the aliphatic content decreased. The response sequence regarding changes in functional groups within organic colloids induced by fertilization was as follows: –CH3, –CH2 > C–O > –OH > C=C. Fertilization promotes the release of 1:1-type inorganic mineral colloids, increasing the content of poorly crystalline minerals. The retention of aromatic carbon and oxygen-containing functional groups by poorly crystalline mineral colloids served as the primary mechanism leading to their increased content levels. Changes in environmental factors significantly impacted the release and properties of soil colloids. Conditions such as low cationic valence, high ionic strength, and high pH promoted the release of soil colloids.ConclusionsThe short-term fertilization resulted in a reduction in the release of soil colloids and brought about significant alterations in their particle size composition and properties. The findings of this study provide valuable insights into understanding the impact of fertilization-induced colloid release on the environmental behavior of agricultural non-point source pollutants.

Modeling solid-state reaction processes: application for the archaeometric study of potteries from Venus Fisica Temple in Pompeii (Italy)

AbstractThis research employs the voltammetry of immobilized microparticles (VIMP) methodology to analyze a collection of ceramic samples from the temple of Venus Fisica in the archaeological site of Pompeii. The primary objective is to discern their origins and manufacturing processes by the solid-state analysis of the electroactive properties of iron minerals, particularly hematite, extensively investigated for its electrochemical and catalytic characteristics. In our study, we propose a model to elucidate the electrochemical processes involved, building upon prior logistic and nucleation formulations. In this model, we consider the possibility of two superimposed pathways. This approach provides a nuanced understanding of composition changes and mineral crystallinity, factors that can induce significant variations in the voltammetric signal. Consequently, it becomes an effective means to discriminate between different provenances and manufacturing techniques of different potteries. The outcomes of this research contribute valuable insights into the intricate realm of ancient ceramic materials, casting light on their origins and production processes within the historical context of Pompeii.

Properties of Durable Mullite Bodies Manufactured from Waste Clay-Diatomite

Durable mullite bodies have been fabricated using diatom frustules from diatomite powder as the Si source and Al-nitrate as the Al precursor, resulting in fibrous pore morphology. The hard mullite ceramics prepared by mold pressing without additives showed high compressive strength (up to 133 MPa when sintered at 1500 °C). The diatomite-nitrate samples were sintered at three temperatures (1300, 1400, and 1500 °C) for 2 hours. XRPD analysis of the sintered samples showed that the crystalline mineral phases mainly comprise mullite, cristobalite, and corundum. SEM results indicate the presence of rod-like mullite grains measuring 5 µm in length and 500 nm in diameter (aspect ratio 1:10). XRPD analysis of the samples sintered at 1300 °C demonstrated good thermo-mechanical stability and the formation of new hard phases (mullite, corundum, and cristobalite), making the analyzed diatomaceous earth suitable to produce various types of ceramic, construction, and thermal insulating materials.

Crystal Symmetry-Inspired Algorithm for Optimal Design of Contemporary Mono Passivated Emitter and Rear Cell Solar Photovoltaic Modules

A metaheuristic algorithm named the Crystal Structure Algorithm (CrSA), which is inspired by the symmetric arrangement of atoms, molecules, or ions in crystalline minerals, has been used for the accurate modeling of Mono Passivated Emitter and Rear Cell (PERC) WSMD-545 and CS7L-590 MS solar photovoltaic (PV) modules. The suggested algorithm is a concise and parameter-free approach that does not need the identification of any intrinsic parameter during the optimization stage. It is based on crystal structure generation by combining the basis and lattice point. The proposed algorithm is adopted to minimize the sum of the squares of the errors at the maximum power point, as well as the short circuit and open circuit points. Several runs are carried out to examine the V-I characteristics of the PV panels under consideration and the nature of the derived parameters. The parameters generated by the proposed technique offer the lowest error over several executions, indicating that it should be implemented in the present scenario. To validate the performance of the proposed approach, convergence curves of Mono PERC WSMD-545 and CS7L-590 MS PV modules obtained using the CrSA are compared with the convergence curves obtained using the recent optimization algorithms (OAs) in the literature. It has been observed that the proposed approach exhibited the fastest rate of convergence on each of the PV panels.

Acid resistance of alkali-activated binders based on clays from phosphate mining by-products

This paper outlines the results of studying the resistance of alkali-activated materials (AAM), based on calcined yellow clay from phosphate mine by-products as a precursor, to an acid attack (with sulfuric and phosphoric acids, 5 %, pH ≈ 0,8–2). Calcined yellow clay (YC850) is used as the source of aluminosilicates, containing montmorillonite, dolomite, and quartz. The alkali-activation of such materials allows the determination of an adequate valorization way and evaluating their durability leads to defining the range of application. The residual compressive strengths were measured after 1, 2, and 4 weeks of immersion in those acids. The deterioration suffered by the paste specimens was examined using different techniques.The degree of deterioration differs from one acid to another; in sulfuric acid, the strengths decrease from 47 MPa to 10.6 MPa presenting 77.4 %. While in phosphoric acid, the decrease was about 36.2 % (30 MPa) after 28 days of attack. This detriment in the strengths is associated with changes not only in the microstructure but also with the alteration of the reaction products, mainly the binding gels C-A-S-H and (C,N)-A-S-H, which undergoes dealumination and decalcification. What is more, the chemical attack involves several reactions; calcium coming from the precursor reacts with the sulfates (in the H2SO4 attack) inducing the precipitation of gypsum, which is responsible for the significant strength loss. In addition, the dissolution of crystalline minerals, such as periclase and gehlenite (present in the precursor) generates higher porosity explaining the obtained results.

The evolution of clay mineral and its indication of hydrocarbons under overpressure: An example from the shale of the Qingshankou Formation in the Gulong Sag

The enrichment and development of shale oil are significantly influenced by the evolution of clay minerals. In this paper, the mineralogy and clay mineral crystallinity of shale samples from Wells X1, X2 and X3 in the Gulong Sag are characterized by X-ray diffraction analysis (XRD) and field emission scanning electron microscopy (FE-SEM). Geochemical parameters, including total organic carbon (TOC) and rock-eval pyrolysis, were also evaluated. The results reveal that illite in the shale primarily exists in the matrix, originating mainly from the transformation of smectite and I/S mixed layer. Chlorite in pores is predominantly formed through fluid precipitation and crystallization. The study area exhibits abnormal evolution of illite and I/S mixed layers, as well as the phenomenon of rapid chlorite growth under overpressure condition. The abnormal evolution of illite and I/S mixed layer may attribute to the inhibition of the conversion reaction from I/S mixed layer to illite. Chlorite's rapid growth occurs through the nucleation mechanism. Furthermore, through the analysis of clay and organic matter correlation, coupled with overpressure and hydrocarbon-rich section considerations, it is observed that chlorite may play a significant role in the storage and generation of S1. This study contributes to a better understanding of the relationship between clay mineral evolution and shale reservoir overpressure, offering valuable insights for the accurate assessment of shale oil.

Ceramic Materials in dentistry using the SPSS Method

Dental ceramics can be used in a variety of root canal therapy, such as inlays, bone grafting, crowns, and bridges, to replace earthenware (PFM) systems with everything systems. Dental crowns, dental composite components, and dentures are all made of porcelain and glass-ceramic materials, which are together referred to as dental ceramics. Conventional dental porcelain is feldspar-based and contain sizable amounts of kaolin (Al2O32SiO22H2O), quartz, and feldspar (KAlSi3O8). Rocks containing mica and iron are known to contain feldspar, a grey crystalline mineral. Ceramics are any of the countless hard, brittle, heat, corrosion-resistant substances produced by molding and thereafter scorching an inorganic, non-metallic substance like clay to high temperatures. Common examples include earthenware, pottery, and brick. Dental ceramics that are made of Lucite feldspathic material are very attractive and frequently utilized. Inlays, on lays, partial crowns, crowns, and veneers for metals and ceramics are among their clinical indications. Ceramics are resistant to high temperatures, effective thermal insulators, and have minimal thermal expansion. For uses like as lining industrial furnaces and sealing space shuttles, it makes really good thermal barriers. Dental ceramics are explained within a framework that makes it simple to comprehend how they developed. symptoms and composition. Engineering assessments of efficacy of treatment are discussed, and research is done. Behavior of all earthenware systems clinically. The usage of dental ceramics is discussed from a practical standpoint. Emphasizing what they know but also how we know it while maximizing beauty and endurance. Reviewing the history of ceramics' use in dentistry is helpful. This account has three purposes: (1) to warn professionals Pottery and improved ceramics were created to remedy the issue; (2) to increase actual issues or restoration diversity; and (3) give a soft backdrop in nature and ceramic science. The use of ceramics has always represented the adoption of "high technology" and "Craftsmanship". Ratio studies are statistical analyses of data from appraisals and property valuations. Nearly all states utilize them to produce quantitative measure of the proportion of current market price about which individually estimated taxable property is appraised as well as to offer assessment performance indicators. Evaluation parameters: Ceramic materials in dentistry, Glass-ceramics, predominantly glassy ceramics, Substructure ceramics, Particle-filled glasses and Polycrystalline ceramics. Result: The Cronbach's Alpha Reliability result. The overall Cronbach's Alpha value for the model is .658 which indicates 66% reliability. From the literature review, the above 50% Cronbach's Alpha value model can be considered for analysis. Characteristics of sisal fiber the Cronbach's Alpha Reliability result. The overall Cronbach's Alpha value for the model is .658 which indicates 66% reliability. From the literature review, the above 50% Cronbach's Alpha value model can be considered for analysis.

Insights into the Crystallinity-Dependent Photochemical Productions of Reactive Oxygen Species from Iron Minerals.

Iron minerals are widespread in earth's surface water and soil. Recent studies have revealed that under sunlight irradiation, iron minerals are photoactive on producing reactive oxygen species (ROS), a group of key species in regulating elemental cycling, microbe inactivation, and pollutant degradation. In nature, iron minerals exhibit varying crystallinity under different hydrogeological conditions. While crystallinity is a known key parameter determining the overall activity of iron minerals, the impact of iron mineral crystallinity on photochemical ROS production remains unknown. Here, we assessed the photochemical ROS production from ferrihydrites with different degrees of crystallinity. All examined ferrihydrites demonstrated photoactivity under irradiation, resulting in the generation of hydrogen peroxide (H2O2) and hydroxyl radical (•OH). The photochemical ROS production from ferrihydrites increased with decreasing ferrihydrite crystallinity. The crystallinity-dependent photochemical •OH production was primarily attributed to conduction band reduction reactions, with the reduction of O2 by conduction band electrons being the rate-limiting key process. Conversely, the crystallinity of iron minerals had a negligible influence on photon-to-electron conversion efficiency or surface Fenton-like activity. The difference in ROS productions led to a discrepant degradation efficiency of organic pollutants on iron mineral surfaces. Our study provides valuable insights into the crystallinity-dependent ROS productions from iron minerals in natural systems, emphasizing the significance of iron mineral photochemistry in natural sites with abundant lower-crystallinity iron minerals such as wetland water and surface soils.

A Modern Multidisciplinary Method to Characterize Natural White Spot Lesions with 2D and 3D Assessments: A Preliminary Study.

In this preliminary study, a multidisciplinary method based on high-resolution analytical techniques (such as microcomputed tomography, Raman Microspectroscopy, scanning electron microscopy, and Vickers microhardness test) was exploited to evaluate the alterations that occur in human teeth at the initial stage of the carious lesion. To this purpose, six extracted molars displaying a natural white spot lesion (WSL) were investigated. Specific morphological, structural, and chemical parameters, such as the mineral density, indentation hardness, molecular and elemental composition, and surface micromorphology were obtained on the WSL, and the results were statistically compared (t-test, p < 0.05) to those of the sound enamel on the same tooth. In the WSL, with respect to the sound area, a decrease in the mineral density and crystallinity was detected together with differences in the molecular composition and surface microstructure, such as the occurrence of micropores and irregularities. Moreover, the elemental analysis highlighted in WSL showed a statistically significant decrease in Ca and P percentages. In conclusion, this multidisciplinary approach allows us to fully characterize the area of interest, providing a deeper knowledge of these enamel lesions, which could have important clinical implications.

Management and liming-induced changes in organo-Al/Fe complexes and amorphous mineral-associated organic carbon: Implications for carbon sequestration in volcanic soils

Amorphous mineral-associated organic carbon (AMAOC) and organo-Al/Fe complexes (Cp) play crucial roles in soil carbon (C) sequestration in volcanic soils. This study investigated the effects of land use management and liming on the C sequestration capacity of a young allophanic Andisol and old halloysitic-kaolinitic volcanic Ultisol sampled at 0–10 and 10–20 cm depth. This study was designed to test two hypotheses: (1) management and liming affect the C sequestration capacity of Andisol by reducing Cp and increasing AMAOC to offset Cp losses, and (2) they do not significantly affect the carbon sequestration capacity of Ultisol because of its more crystalline mineral forms and reduced amount of Cp. This study was conducted using a selective dissolution technique and density fractionation with agricultural soils and forests as control soils. After 43 years of intensive management and liming, the soil organic carbon (SOC) content decreased by 32% in the topsoil compared to the original native forest soil (178 ± 2 g kg−1 soil), mainly in the particulate organic matter (POM) fraction, which decreased by 74% compared to the native forest soil (61 ± 9 g kg−1 soil). However, Cp decreased only by 40% compared to the forest soil (62 ± 1 g kg−1 soil) from pHKCl 4.8–5.0, and AMAOC increased in 17% in the topsoil and 64% in the subsoil, supporting the first hypothesis of this study. In the cultivated Ultisol, SOC decreased by 35% due to the POM fraction, and mineral-associated organic C (MAOC) decreased by 37% compared to the forest soil (38 ± 7 g kg−1 soil). These results partially support the second hypothesis because the crystalline clay minerals from which MAOC originated remained unchanged and were strongly correlated with SOC. The mass balance of both soils indicated that the stable C losses from native forest soils were < 14%. These results highlight the importance of different C sequestration mechanisms to compensate for SOC losses in the young allophanic Andisol and old volcanic Ultisol. Our findings imply that both mechanisms can be used to estimate the C sequestration capcity in similar soil types.

Effects of the groundwater flowing and redox conditions on arsenic mobilization in aquifers of the Datong Basin, Northern China

A multi-level field site was built at the As-affected area of the Datong basin. The one-year monitoring results showed that the three aquifers exhibit different redox conditions and hydrogeochemical behaviors. In the shallow aquifer, groundwater As concentration is up to 220.5 μg/L, which is related to the dissimilatory reduction of poor-crystalline Fe minerals. In the middle aquifer, groundwater sulfate reduction shows two sides effects on As mobilization that the reduced sulfide on the one hand promotes the release of sediment As via abiotic reductive dissolution of Fe minerals and on the other hand immobilizes groundwater As via the adsorption on the newly formed Fe(II)-sulfide minerals. In the deep aquifer, the reductive dissolution of crystalline Fe minerals was the dominant process causing the release of sediment As into groundwater with the highest As concentration up to 341.1 μg/L. Based on the one-year monitored data, a coupled flow and reactive transport model was developed. The model results showed that only considering the groundwater flow underestimated the concentration of groundwater As. When adding the hydro-biogeochemical processes, the good agreement was achieved between the observed and simulated groundwater As. In the shallow and deep aquifers, microbially mediated reduction of poor-crystalline and crystalline Fe minerals contributed approximately 85 % of groundwater As. In the middle aquifer, abiotic reduction of Fe minerals driven is responsible for around 35 % of the release of sediment As, and around 17 % of released As was re-adsorbed or co-precipitated onto the neo-formed Fe(II) minerals. Under different redox conditions, the hydrogeochemical behavior of As was dominantly controlled by the Fe-S-As cycling in the groundwater system.

Research Enhancing Acidic Mine Wastewater Purification: Innovations in Red Mud-Loess.

This study investigates the adsorption of cadmium (Cd) by red mud-loess mixed materials and assesses the influence of quartz sand content on permeability. Shear tests are conducted using various pore solutions to analyze shear strength parameters. The research validates solidification methods for cadmium-contaminated soils and utilizes SEM-EDS, FTIR, and XRD analysis to elucidate remediation mechanisms. The findings suggest that the quartz sand content crucially affects the permeability of fine-grained red mud-loess mixtures. The optimal proportion of quartz sand is over 80%, significantly enhancing permeability, reaching a coefficient of 6.7 × 10-4 cm/s. Insufficient quartz sand content of less than 80% fails to meet the barrier permeability standards, leading to a reduced service life of the engineered barrier. Adsorption tests were conducted using various pore solutions, including distilled water, acidic solutions, and solutions containing Cd, to evaluate the adsorption capacity and shear characteristics of the red mud-loess mixture. Additionally, the study examines the behavior of Cd-loaded red mud-loess mixtures in various pore solutions, revealing strain-hardening trends and alterations in cohesiveness and internal friction angle with increasing Cd concentrations. The analysis of cement-red mud-loess-solidified soil demonstrates enhancements in soil structure and strength over time, attributed to the formation of crystalline structures and mineral formations induced by the curing agent. These findings provide valuable insights into the remediation of cadmium-contaminated soils.