Search Results (2,991)

Land leveling deep-seated landslides for agricultural use alters soil profile integrity and soil functionality. In the mid-20th century, such interventions in the Transylvanian Basin (Romania) involved grading and converting landslide bodies into arable land. This study evaluates the consequences of interventions on soil physicochemical properties and erosion susceptibility in the case of two deep-seated landslides. Soil samples collected from leveled landslide bodies were analyzed for pH, total nitrogen, available phosphorus (P-AL), available potassium (K-AL), calcium carbonates, humus content, and texture. The results, in the case of the two studied deep-seated landslides, indicate contrasts between areas where the Ah horizon is preserved and where leveling exposed the C horizon or parental material at the surface. Exposed zones exhibit reduced nitrogen and humus content, altered textures, and higher carbonate influence, indicating lower fertility potential despite 65 years of pedogenesis. Spatial assessment using Sentinel-2-derived NDMI and USLE-based erosion modelling confirms increased moisture stress and higher erosion susceptibility in areas with exposed substratum. These findings demonstrate that the leveling of the two studied deep-seated landslide bodies, although effective in expanding arable surfaces, leads to persistent soil degradation patterns and reduced agro-ecological resilience. Sustainable cultivation of such terrains requires targeted soil conservation measures, including erosion control and adapted land management practices. The results provide important implications for land-use planning in landslide-prone agricultural landscapes. Full article

This research explored how dietary supplementation of calcium nitrate influences methane emissions, nitrogen excretion, ruminal fermentation parameters, and microbiota in Liuyang black goats. A total of twelve male goats from this breed were divided into two groups: one serving as a control group (CON), while the other received a treatment of 3% calcium nitrate (CAL). The research was conducted over a period of 40 days and comprised two separate trial phases. A 10-day adaptation period and a 5-day sampling period (days 11–15) for each stage. Results showed that incorporating calcium nitrate significantly reduced the emissions of methane (CH₄) (p < 0.05) and carbon dioxide (CO₂) (p < 0.05). Moreover, the use of calcium nitrate modified the trends in ruminal fermentation, resulting in an increase in pH (p < 0.05). Moreover, the ratio of acetate to propionate (A:P) was notably reduced in the CAL group (p < 0.05), indicating a shift toward enhanced production of propionate. At the microbial level, an increased presence of Bacteroidota and Prevotella was observed in the CAL group (p < 0.05). In contrast, the CON group exhibited elevated levels of Firmicutes and Methanobrevibacter (p < 0.05). This finding suggests that calcium nitrate plays a significant role in reducing methane emissions and also affects the fermentation processes in the rumen along with the microbiota of Liuyang black goats. Further research is needed to examine the long-term implications of calcium nitrate supplementation on the health and productivity of these goats. Full article

Located in the north of Yunnan Province, China, the Wuding geothermal area is a typical medium- and low-temperature geothermal system with strong hydrothermal activity and development potential as a clean and renewable energy resource. This study systematically investigates the main controlling factors of the Wuding geothermal field through field investigation, hydrochemical analysis, and stable isotope analysis, and puts forward a genetic model of the geothermal field. The results show that the Wuding geothermal field is a medium- to low-temperature, conduction-dominated geothermal system, and its geothermal water is predominantly of the Ca–HCO₃ (calcium bicarbonate) type. The recharge area lies at an altitude above 2250 m, which is speculated to be within the mountainous area in the southwest of the study area. The underground hot water in the area is immature water. The source water circulates to the deep heat storage zone along faults, rises to the surface through heat convection, and is exposed as hot springs. Upon discharge, the geothermal water mixes with shallow cold water, with cold-water dilution accounting for up to 85% of the total volume. Using the silica thermometer, cation thermometer, and silicon enthalpy model, the maximum temperature of heat storage is estimated to be 91 °C, with the depth of geothermal water circulation reaching 2200 m. The thermal reservoir is composed of dolomites of the Upper Cambrian Erdaoshui Formation (∈3e) and Sinian Dengying Formation (Zbd). Its heat source is heat flow from the upper mantle and the decay of radioactive elements. Continuous heat flow to the thermal reservoir is maintained through the fold fracture zone and faults in the core of the Hongshanwan anticline. The proposed genetic model of the Wuding geothermal field provides a scientific basis for the sustainable redevelopment and utilization of this geothermal resource and is of significance for regional low-carbon energy use and socio-economic sustainable development. Full article

Calcium–silicate–hydrate (C-S-H), the primary binding phase governing cement paste cohesion, undergoes progressive physicochemical transformation upon carbonation—a process that critically dictates concrete durability in atmospheric environments. When CO₂ penetrates the porous cement matrix, it triggers a cascade of degradation mechanisms: calcium leaching decalcifies the C-S-H structure, inducing polymerization of silicate chains from dimeric to longer-chain configurations, while concurrent precipitation of calcium carbonate and amorphous silica gel fundamentally reconstitutes the nanoscale architecture. These nanoscale alterations propagate to macroscopic property evolution, manifesting as initial strength and stiffness gains due to pore-filling carbonation products followed by eventual deterioration as the cohesive binding network deteriorates. This review synthesizes current understanding of carbonation-induced structural evolution, examining the coupled influences of environmental parameters—CO₂ concentration, relative humidity, and temperature—alongside C-S-H intrinsic chemistry (Ca/Si ratio, aluminum substitution, and alkali content) on reaction kinetics and material performance. However, significant knowledge gaps persist: predictive models for in-service carbonation rates remain elusive due to the disconnect between idealized laboratory conditions and the heterogeneous, cracked reality of field concrete; the causal linkage between nanoscale C-S-H alteration and macroscale cracking patterns along with physical performance is poorly resolved, and most mechanistic studies rely on synthetic C-S-H, neglecting the compositional complexity of real Portland cement systems. We further propose emerging protection strategies, including surface barrier coatings and low-carbon alternative binders (geopolymers, calcium sulfoaluminate cements, carbon-negative materials such as recycled cement), which demonstrate enhanced carbonation resistance. Future research priorities include developing effective coating barriers for carbonation protection, developing operando characterization techniques for real-time reaction monitoring, deploying machine learning algorithms to bridge atomistic simulations with structural-scale predictions, and establishing long-term field performance databases to validate laboratory-derived degradation models. Full article

Against the backdrop of dual-carbon goals and resource constraints, the high-value utilization of recycled fine aggregates (RFAs) remains limited, leading to inconsistent engineering performance and insufficient durability. Enzyme-induced carbonate precipitation (EICP) represents a promising low-carbon cementation method, yet its deposition uniformity and cementation efficiency are influenced by the pore structure of granular media and associated mass transfer pathways. This study employs a two-stage experimental design to investigate the synergistic effects of particle size distribution characteristics, represented primarily by d₅₀, and fiber addition on EICP-cemented RFA. Phase I (fiber-free; d₅₀ = 0.67–1.14 mm) results indicate that, across the tested gradation schemes, the CaCO₃ content generally decreased from 9.49% to 7.72% as the representative d₅₀ increased, while the dry density changed only slightly (1.637–1.617 g/cm³). However, the unconfined compressive strength (UCS) decreased from 1000 kPa to 541 kPa (45.9% reduction), indicating that strength is primarily governed by the connectivity of the cementation network rather than solely by the degree of densification. In Phase II, glass fiber (GF), polypropylene fiber (PPF), and jute fiber (JF) were incorporated into the ERFA4 gradation scheme selected for fiber modification. All three systems exhibited a unimodal optimum pattern: the peak CaCO₃ contents reached 10.71% (GF 0.5%), 10.11% (PPF 0.7%), and 11.46% (JF 0.7%), corresponding to peak UCS values of 1917, 1874, and 2450 kPa, respectively. Microscopic analysis suggested that fiber bridging coupled with CaCO₃ deposition may contribute to the formation of a “fiber-CaCO₃-particle” stress-transfer network, which is consistent with the observed enhancements in load-bearing capacity, ductility, and post-peak stability. Full article

Coal-fired power plants can adversely affect aquatic ecosystems through wastewater discharge, waste landfills, and the atmospheric deposition of toxic substances released during coal combustion. These processes degrade the water quality of nearby surface and underground water bodies. The study presents the impact of the coal-fired power plant Contour Global Maritza East 3 on the ecological status of the Sokolitsa River, reflected by changes in the composition and structure of the sensitive phytobenthos and macrozoobenthos communities and supporting environmental variables, including water temperature, pH, dissolved oxygen, conductivity, nutrients, sulfates, calcium, and calcium carbonate hardness. Methods for monitoring and assessing the ecological status of surface water bodies compliant with European and national legislation were applied to the studied biological quality elements and key physicochemical variables. Historical monitoring data from a ten-year period, 2013–2022, together with data collected during the study in 2023 and 2024 were analyzed and evaluated. The results indicated a significant increase in most physicochemical variables downstream of the CFPP compared with the upstream site, including water temperature, conductivity, calcium carbonate hardness, calcium, sulfates and nitrogen (N) nutrients (ammonium N, nitrite N, nitrate N, total N). The ecological status of the river deteriorated, as indicated by the negatively affected aquatic habitats and the changes in the taxonomic richness and abundance of the studied organism groups. Full article

In Mexico, pecan (Caria illinoienensis Wangenh K. Koch) cultivation is considered a primary agricultural activity of great importance, particularly in the state of Chihuahua. Due to the region’s climatic conditions, the soils used for this crop present several limitations that may restrict their agricultural use, as they often exhibit low or null fertility, classifying them as marginal soils. However, these soils can be rehabilitated through appropriate management practices. Among the main recovery strategies are the application of mineral and organic amendments and the use of plant-growth-promoting microorganisms, all of which are considered environmentally friendly alternatives. Therefore, the objective of this study was to identify the types of mineral and organic amendments suitable for the recovery of marginal soils in the agronomic management of pecan cultivation. This study was conducted in the San Cristóbal pecan orchard, located in the municipality of Jiménez, Chihuahua, using a 5⁶ factorial design, reduced to 25 treatments through the Taguchi L25 method. Statistical analysis was performed using response surface methodology, and the evaluated parameters included basic, physical, fertility, and cation-exchange properties of the soil. The results showed that zeolite (19.30 t ha⁻¹) and calcium carbonate (12.70 t ha⁻¹) were amendments that produced the greatest effect on the evaluated parameters. The use of these amendments can significantly complement annual fertilization programs, contributing to meeting the crop’s nutritional demands under a sustainable management approach for pecan production. Full article

This study presents a comprehensive characterization of Argopecten purpuratus (AP) shells—a marine-derived natural bioceramic composed predominantly of calcium carbonate (CaCO₃)—to evaluate their potential as biomaterials for regenerative medicine. Structural and compositional analyses were performed using micro-computed tomography (MicroCT), scanning electron microscopy (SEM), Fourier-transform infrared spectroscopy (FTIR), thermogravimetric analysis (TGA), and X-ray diffraction (XRD). These techniques confirmed a high CaCO₃ content (>96 wt%) and revealed distinct microstructural features: the outer surface showed irregular grooves and rough textures, while the inner surface exhibited smoother, foliated morphologies with mixed calcite and aragonite phases. To assess biocompatibility, human gingival mesenchymal stem cells (hGMSCs) were cultured on both shell surfaces. Viability and adhesion were evaluated via MTS assays and fluorescence microscopy at time points ranging from 30 min to four weeks. Both surfaces supported robust early metabolic activity and long-term proliferation, with cells covering the entire surface area after four weeks. Morphometric analysis indicated time-dependent changes in cell shape, transitioning from rounded to elongated morphologies, with minor differences linked to surface topography. The integration of structural, compositional, and biological data demonstrates that AP shells provide a cytocompatible and sustainable natural material platform capable of supporting cell adhesion and proliferation. Their inherent micro- and nanoscale surface features may facilitate protein adsorption and cell–material interactions. These findings highlight the importance of correlating microstructural material properties with cellular responses and support the future exploration of marine-derived bioceramics for regenerative medicine applications. Full article

Geopolymer concrete (GPC) has emerged as a promising low-carbon alternative to ordinary Portland cement (OPC), yet wider adoption is limited by the lack of standardised mix-design procedures. Precursor, activator, curing, and aggregates strongly interact to affect properties, but findings are scattered and hard to generalise. This review consolidates and normalises published findings to clarify how key parameters-precursor type, activator dosage and concentration, activator-to-binder ratio, curing temperature, and aggregate gradation-control fresh and hardened performance. Overall trends indicate that calcium-rich systems enhance early strength by 80–100% at typical replacement levels; while optimum activator conditions of 12 M NaOH and sodium silicate/sodium hydroxide ratio = 2.5 commonly improve strength by 40–60% relative to sub-optimal ratios; alkaline activator-to-binder ratios of 0.4–0.7 provide the most practical strength-workability balance. Heat curing at 80–100 °C significantly accelerates early-age property development by 50–200% compared to ambient curing, depending on duration and activator chemistry. A target-strength mix design is demonstrated through a 40 MPa case study. Using a compiled dataset for fly ash (FA)-based GPC, a modulus–strength framework is proposed; common OPC code equations over-predict elastic modulus for 15–50 MPa, and calibration yields a conservative, code-compatible relation: E = $2.75\sqrt{f{c}_{MPa}}$. Key limitations are highlighted, including variability in raw materials and durability uncertainties, and future directions are proposed toward performance-based design and standardisation to support structural use of GPC in sustainable infrastructure. Full article

Insufficient tensile strength, low abrasion resistance, and inadequate consistency in the fresh state led to fractures and decreased the durability of the concrete. Tensile stress resistance is the most challenging, resulting in the formation of microcracks that propagate to a macrolevel. Nanomaterials, with dimensions ranging from 0.1 to 100 nanometers, represent an innovative class of materials that can enhance the mechanical properties of concrete through the nano-core effect. These materials play significant roles in the formation of calcium–silicate–hydrate (C-S-H) gels, contribute to seeding effects, and augment cement hydration reactions. Given the above, the addition of nanomaterials makes concrete exhibit exceptional mechanical strength and improved durability performance. The primary objective of this review is to identify the potential nanomaterials suitable for the development of high-performance concrete. This article reviews the literature on the effects of nanoparticles, such as nano-calcium carbonates (NCCs), iron oxide (NI), nano-aluminum oxide (NA), graphene oxide (GO), nano-silica (NS), and nano-titanium oxide (NT) on the fresh and hardened properties of the material. The study identifies a promising nanomaterial for enhancing concrete, highlights research gaps, and suggests future research directions for its optimal application in future concrete constructions. Full article

The deterioration of mechanical properties and seepage issues in fractured rock masses represent critical technical bottlenecks in the field of geotechnical engineering. Traditional remediation techniques suffer from drawbacks such as environmental pollution, poor filling effects in microfissures, and susceptibility to secondary cracking, making it difficult to meet the requirements for long-term effectiveness and environmental compatibility in fractured rock mass reinforcement. Microbially induced calcium carbonate precipitation (MICP) technology, which drives the formation of calcium carbonate crystals through microbial metabolic activities, achieves fracture filling and rock mass reinforcement. This technology offers several advantages, including environmental friendliness, high permeability, and excellent compatibility; thus, it represents a cutting-edge direction for green remediation in geotechnical engineering. In this paper, the core mineralization mechanisms of MICP technology, key influencing factors, and engineering applications in fractured rock masses are systematically analysed. Research has indicated that MICP can significantly increase the compressive strength, impermeability, and liquefaction resistance of fractured rock masses, enabling both self-healing of rock fractures and precise filling of existing fissures. Compared with traditional techniques, it demonstrates superior environmental compatibility and remediation efficacy. This review aims to serve as a reference for theoretical research and engineering applications of MICP in fractured rock mass reinforcement. Full article

Curcumin exhibits potent anti-obesity and anti-inflammatory activities; however, its therapeutic application is limited by poor aqueous solubility and low oral bioavailability. A curcumin-loaded chewable gel was developed to transform into an in situ gastric gel upon contact with gastric fluid after mastication. Curcumin solid dispersions (CUR-SDs) were prepared with Eudragit^® EPO (1:1–1:7, w/w) using the solvent evaporation method. The optimized formulation (1:3) markedly enhanced solubility and dissolution in acidic medium (0.1 N HCl, pH 1.2) compared with crystalline curcumin and physical mixtures. The optimized CUR-SD was subsequently incorporated into chewable gels composed of sodium alginate and κ-carrageenan, with calcium carbonate as a gas-forming agent. The formulations formed buoyant matrices under acidic conditions, exhibiting floating lag times of 21–215 s and sustaining drug release for up to 8 h. Increasing polymer content improved mechanical strength and modulated release kinetics. Among the tested formulations, F7 achieved the optimal balance between texture properties, floating behavior, and controlled-release performance. In LPS-stimulated RAW264.7 macrophages, curcumin, CUR-SD, and F7 showed comparable and potent anti-inflammatory activity (IC₅₀ = 4.12–4.84 µg/mL), outperforming indomethacin. In 3T3-L1 adipocytes, F7 significantly reduced lipid accumulation (~47%) in a concentration-dependent manner. These findings demonstrate that this transformable chewable in situ gelling platform is a promising gastroretentive strategy for improving the oral therapeutic efficacy of poorly soluble bioactive compounds for anti-obesity applications. Full article

Calcium carbonate is a widely used filler in polymer composites due to its low cost and ability to improve stiffness, dimensional stability, and impact resistance. However, its hydrophilic surface limits compatibility with nonpolar polymer matrices, making surface modification essential to improve filler dispersion and interfacial adhesion. Stearic acid is commonly applied as a surface modifier for calcium carbonate because it readily chemisorbs onto the mineral surface and forms densely packed self-assembled monolayers that improve hydrophobic character. Despite its widespread use, stearic acid exhibits limited thermal and interfacial stability under polymer processing conditions, motivating the development of stabilization strategies. In this work, gamma and electron-beam irradiation were applied to stearic-acid-modified calcium carbonate to modify the surface-bound stearic acid layer with the aim of enhancing its interfacial stability, surface resistance, and hydrophobic performance, and to evaluate the influence of irradiation atmosphere on these effects. The modified materials were characterized in terms of structural integrity, surface wettability, surface free energy, thermal stability, and optical properties. The results demonstrate that ionizing radiation enhances surface hydrophobicity and coating durability while preserving the crystal structure of the CaCO₃ substrate. Gamma irradiation of stearic-acid-modified vaterite exhibited strong atmosphere dependence, with improved hydrophobicity under oxygen-free conditions, whereas electron-beam irradiation showed more robust and oxygen-insensitive behavior. Based on the observed improvements in hydrophobicity, surface free energy, and thermal stability, electron-beam irradiation emerges as a promising and less atmosphere-sensitive approach for producing durable stearic-acid-modified CaCO₃ fillers suitable for polymer composite applications. Full article

In desert ecosystems, deep-rooted plants like Alhagi sparsifolia contribute not only to wind prevention and sand fixation but also to the transport of carbon into deep soil layers through their root systems. However, the sources and stabilization mechanisms of soil organic carbon (SOC) following plant carbon input remain unclear. This study investigated a dominant A. sparsifolia community at the southern edge of the Taklimakan Desert. We analyzed plant traits and the vertical distribution (0–200 cm) of SOC fractions—particulate organic carbon (POC), mineral-associated organic carbon (MAOC), and calcium/iron-bound organic carbon (Ca/Fe-OC)—along with carbon sources (microbial biomass, microbial necromass, and plant residue). As growth advanced, stem and root biomass increased, while leaf and thorn biomass remained stable. SOC and POC decreased by 5.38–29.43% with soil depth, whereas MAOC and Ca/Fe-OC increased by 32.34–48.15%. Plant residue contributed more to SOC (average 30.56%) than microbial necromass (8.28%), and both contributions increased by 9.60–167.68% with soil depth. No significant correlation was found between plant residue and SOC fractions, but a significant correlation with microbial necromass. In conclusion, although plant residues constitute the primary source of SOC in desert ecosystems, microbial necromassa exerts a stronger influence on SOC stability. Full article

Ground granulated blast furnace slag (GGBFS)-based cementitious materials, known for their high strength and good fluidity, present an eco-friendly, low-carbon alternative to ordinary Portland cement (OPC). However, the high cost of activators poses a significant challenge, accounting for over 50% of alkali-activated material production costs. This study uses carbide slag (CS), a byproduct of polyvinylchloride (PVC) production, as an activator, along with other solid wastes such as GGBFS and fly ash (FA) as precursors to develop a novel, low-carbon alkali-activated material binder made entirely from solid waste. Various mixtures with different proportions of CS and GGBFS were prepared, and their workability and strength were tested at different ages. Additionally, the hydration characteristics and microstructure of the samples were analyzed using XRD, TG-DTG, FTIR, heat of hydration tests, and SEM-EDS. Results show that calcium hydroxide in CS activates the pozzolanic activity of GGBFS and FA, improving the strength as the proportion of CS increases. At the 5% CS content, the 7 days compressive strength of the GGBFS-based alkali-activated material increased by 79.7% compared to a 2% CS content. However, adding CS reduces the workability of the polymer slurry, with a spread decrease of 168.5 mm and 161.5 mm as the CS content increases from 2% to 8%. The inclusion of CS also increases the rate and total heat released during hydration, with the optimal performance observed at 5% CS. While FA incorporation reduces strength, it enhances slurry workability and reduces heat release during hydration. The strength development is attributed to the formation of AFt, C-S-H gel, C-(A)-S-H gel, and hydrocalumite-like hydrates. Full article