Search Results (8,217)

With intensifying watershed pollution pressures and growing ecological vulnerability, scientifically revealing and enhancing the water environmental carrying capacity is crucial for ensuring the long-term health of the basin and the sustainable socioeconomic development of the region. However, the dynamic regulatory mechanisms linking narrow-sense and broad-sense water environmental carrying capacity remain poorly understood, limiting the development of integrated management strategies. This study systematically investigated the changing trends of both the narrow-sense and broad-sense water environmental carrying capacity in the Harbin section of the Songhua River basin through model calculations, along with the regulatory mechanisms of its key influence indicators. The results of the study on the carrying capacity of the water environment in the narrow sense show that permanganate, total phosphorus, and ammonia nitrogen exhibited partial carrying capacity across water periods, while dissolved oxygen decreased during flat and dry periods, with only limited capacity remaining at the Ash River estuary and in the Hulan River. The biochemical oxygen demand in the Ash River was consistently overloaded, and total nitrogen showed insufficient capacity except during the abundant water period. Broad-sense analysis indicated that improving urbanization quality, water supply infrastructure, and drinking water safety could effectively reduce future overload risks, with projections suggesting a transition from critical to loadable levels by 2030, though latent threats persist. Correlation analysis between narrow- and broad-sense indicators informed targeted control strategies, including stricter regulation of nitrogen- and phosphorus-rich industrial discharges, restoration of aquatic vegetation, and periodic dredging of riverbed sediments. This work is the first to dynamically integrate pollutant and socio-economic indicators through a hybrid modelling framework, providing a scientific basis and actionable strategies for improving water quality and achieving sustainable management in the Songhua River Basin. Full article

Biopolymers have gained significant attention due to their environmental advantages, with insects emerging as a promising but underutilized source of chitin and chitosan. In this study, chitosan was extracted from the larval exuviae of Tenebrio molitor through sequential demineralization, deproteinization, and deacetylation steps. For selected analyses, the extracted chitosan was further purified via reprecipitation from an acid solution using a basic precipitant (1 M NaOH). Chitosan was then characterized using chemical and instrumental methods. The results indicated that the chitosan had a medium degree of deacetylation (72.27%) and viscosity-average molecular weight (612 kDa), along with minimal ash (0.33%) and amino acid (0.14%) content, suggesting high product quality. FTIR analysis identified characteristic functional groups present, and SEM analysis highlighted a fibrous and porous microstructure in the purified chitosan. The prepared films exhibited favorable properties, including low thickness (0.0197 mm), high swelling degree (335.07%), moderate water solubility (46.99%), and moisture content of 32.39%, supporting their practical applicability. T. molitor exuviae thus represents a sustainable and environmentally friendly source of high-quality chitosan, with beneficial structural and functional properties, supporting its use in a wide array of value-added applications. Full article

High-calcium fly ash (HCFA), produced from the lignite combustion, has emerged as a global concern due to its fine particle size and adverse environmental impacts. This study presents the characteristics of dispersed microspheres from HCFA obtained using modern techniques, such as XRD, SEM-EDS, ⁵⁷Fe Mössbauer spectroscopy, DSC-TG, particle size analysis, and magnetic measurements. It is found that an increase in microsphere size is likely due to the growth of the silicate glass-like phase, while the magnetic crystalline phase content remains stable. According to the ⁵⁷Fe Mössbauer spectroscopy, there are two substituted Ca-based ferrites—CaFe₂O₄ and Ca₂Fe₂O₅ with a quite different magnetic behavior. Besides, the magnetic ordering temperature of the brownmillerite (Ca₂Fe₂O₅) phase increases with the average diameter of the microspheres. FORC analysis reveals enhanced magnetic interactions as microsphere size increases, indicating an elevation in the concentration of magnetic microparticles, primarily on the microsphere surface, as supported by electron microscopy data. The discovered the magnetic crystallographic phases distribution on the microsphere’s surface claims the accessibility for further enrichment of the magnetically active particles and the possible application of fly ashes as a cheap source for magnetic materials synthesis. Full article

Loess has poor engineering properties, including wet subsidence and dynamic fragility, and the dynamic stability of the loess subgrades can be improved by compacted modified loess mixing industrial wastes such as fly ash and lignin. However, the performance of the modified loess under complex environmental conditions, including dry and wet cycles, as well as freeze-thaw cycles, remains unclear. In this study, the dynamic and structural characteristics of modified loess mixing fly ash and lignin under the coupling effect of dry-wet/freeze-thaw cycles were investigated through laboratory tests, including dry-wet–freeze/thaw cycle tests, dynamic triaxial tests, and scanning electron microscope tests. The cumulative plastic deformation characteristics of the improved loess under different dry-wet cycles and freeze-thaw cycles were analyzed. Combined with the scanning electron microscope test results, the attenuation mechanism of the strength of the improved loess under dry-wet/freeze-thaw coupling was analyzed. The results show that the dry-wet/freeze-thaw cycles have a significant effect on the dynamic deformation of the improved loess. With the increase in dry-wet/freeze-thaw cycles, the cumulative plastic deformation of the improved loess increases logarithmically with the rise in vibration times. With the increase in the number of dry-wet/freeze-thaw cycles, the improved loess becomes loose. The micro-cracks formed in the modified loess due to the connection and directional arrangement of the pores, and become wider and wider with the increase in dry-wet/freeze-thaw cycles. The apparent porosity, average porous diameter, and pore fractal dimension of the improved loess increase, while the probability entropy decreases. Compared with freeze-thaw cycles, dry-wet cycles had a greater effect on the microstructure of the improved loess, which made the deterioration of the dynamic stability of the improved loess more obvious. Full article

In recent years, recovering critical elements from coal has attracted considerable interest due to their significant potential and resulting advantages. A prime example is the coal-hosted Al-Ga-Li-REE deposit within the Jungar Coalfield of Inner Mongolia, northern China, where lithium (Li), gallium (Ga), and aluminum (Al) are successfully extracted from coal ash. However, the specific forms in which these elements exist, crucial for developing effective extraction methods, remain unquantified. This research investigated the distribution of Li, Ga, Nb, Zr, and rare earth elements (REEs) within the coal. The study employed a combination of analytical techniques, including inductively coupled plasma mass spectrometry (ICP-MS), sequential chemical extraction (SCE), scanning electron microscopy coupled with energy-dispersive X-ray spectrometry (SEM-EDS), and X-ray powder diffraction analysis (XRD). The analyzed coals exhibited enriched levels of Li, Ga, Zr, Nb, and REEs. Kaolinite and boehmite were the primary mineral constituents, along with minor amounts of calcite, pyrite, rutile, goyazite, and chlorite. Sequential chemical extraction revealed that Li and Ga are primarily associated with aluminosilicate phases (71.84%–84.39%) and, to a lesser degree, organic matter (12.15%–25.09%). Zirconium and Nb were also predominantly found within aluminosilicates (68.53%–95.96%). REEs occur mainly in carbonate (28.28%–60.78%), aluminosilicate (11.6%–33.08%), and organic (22.04%–29.42%) fractions. Full article

The environmental impact of cement production is strongly associated with the high clinker content and its corresponding CO₂ emissions. This study examines the performance of low-emission cement mortars incorporating supplementary cementitious materials (SCMs), such as ground granulated blast-furnace slag (GGBFS) and fly ash, which partially replace clinker and contribute to CO₂ reduction. Six cement types (CEM I, CEM II/B-V, CEM II/B-S, CEM III/A, CEM V/A (S-V), and CEM V/B (S-V)) were assessed in 104 mortar formulations using a polycarboxylate-based superplasticizer, under varied curing temperatures (10 °C, 20 °C, 29 °C, and 33 °C). The present study is an experimental analysis of the impact of different plasticising and superplasticising admixtures on the demand for admixtures to achieve high flowability and low air content in cement-standardised mortar for admixture testing. PN-EN 480-1. The results indicate that mortars containing CEM III/A and CEM V/B (S-V) exhibited compressive strengths comparable to or superior to CEM I at 28 days, with strength gains exceeding 60 MPa at 20 °C. Workability retention at elevated temperatures was most effective in slag-rich cements. The plasticizing efficiency of the admixture decreased at temperatures above 29 °C, especially in fly ash-rich systems. The incorporation of SCMs resulted in an estimated reduction of up to 60% in clinker, with a corresponding potential decrease in CO₂ emissions of 35–45%. These findings demonstrate the technical feasibility of using low-clinker, superplasticized mortars in varying thermal environments, supporting the advancement of sustainable cementitious systems. Full article

In industrial production, flue gas heat exchangers are often affected by the low-temperature condensation of industrial flue gas due to the influence of the working environment, resulting in serious ash deposition and corrosion. In order to solve this problem, in this study, we developed an ash deposition and corrosion monitoring system to compare the ash deposition prevention performance and corrosion resistance of different materials, as well as its influence on the heat transfer performance of different materials in the same environment. The following coatings were selected for the experiment (values in parentheses are the concentrations of the added compounds): ND, Q235, 316L, Ni-Cu (0.4 g/L)-P, Ni-P-SiO₂ (40 g/L), Ni-Cu (0.4 g/L)-P-SiO₂ (20 g/L), Ni-Cu (0.4 g/L)-P-SiO₂ (40 g/L), and Ni-Cu (0.4 g/L)-P-SiO₂ (60 g/L). The results show that the Ni-Cu (0.4 g/L)-P-SiO₂ (40 g/L) coating has excellent corrosion resistance, while the Ni-Cu (0.4 g/L)-P-SiO₂ (60 g/L) coating shows excellent antifouling performance. Through the comparative analysis of polarization curves, impedance spectra, and coupled corrosion experiments, the test materials were ranked as follows based on their corrosion resistance: 316L > Ni-Cu-P-SiO₂ (40 g/L) > Ni-Cu-P-SiO₂ (20 g/L) > Ni-P-SiO₂ > Ni-Cu-P-SiO₂ (60 g/L) > Ni-Cu-P > ND > Q235. It was also demonstrated that the new coated pipes were able to reduce the exhaust temperature below the dew point and maximize the recovery of energy from the exhaust gas. The acid–ash coupling mechanism of the coating in the flue gas environment was further analyzed, and an acid–ash coupling model based on Cu and SiO₂ is proposed. This model analyzes the effect of the coating under the acid–ash coupling mechanism. Using coated tubes in heat exchangers helps to recover waste heat from coal-fired boilers, enhance heat exchange efficiency, extend the service life of heat exchangers, and reduce costs. Full article

Background: Soybean (Glycine max (L.) Merr.), a nutrient-rich leguminous crop high in protein, lipids, and minerals, is extensively cultivated worldwide. The chemical composition of soybean seeds depends not only on the genetic characteristics of the cultivar but also on environmental conditions and agricultural practices. In recent years, biostimulants have gained increasing importance in crop production due to their ability to enhance physiological processes in plants and potentially influence nutrient accumulation. This study aimed to investigate how cultivar and biostimulant type influence the chemical composition of soybean seeds under varying weather conditions in Central Europe. Methods: A three-year field experiment (2017–2019) was conducted in eastern Poland (Central Europe) using a split-plot design. The experimental factors included three non-GMO soybean cultivars (Abelina, Merlin, and SG Anser) and two foliar biostimulants (Asahi SL and Improver). In addition to classical ANOVA, the multivariate analysis of the impact of the investigated factors included principal component analysis (PCA). Results: The applied factors significantly affected seed contents of fat, protein, dry matter, ash, fibre, and macronutrients (N, P, K). Cv. Merlin had the highest fat (22.65%) and fibre content (9.33%), while Abelina showed the highest protein (37.06%) and dry matter content (94.42%). Biostimulant application increased the accumulation of several seed components. Asahi SL significantly enhanced fat content (by 0.69%), protein content (by over 1.5%), and dry matter content (by nearly 0.2%) compared to the control. Improver was more effective in increasing nitrogen (by 0.24%), phosphorus (by 0.5%), and potassium (by 0.15%) contents. Weather conditions throughout the growing seasons significantly altered the impact of the biostimulants. The PCA analysis revealed distinct relationships among the chemical properties of seeds, meteorological factors, and the applied biostimulants. Full article

The present study explores the sustainable potential of volcanic ash sourced from the active Sakurajima volcano (Japan) as an eco-friendly alternative to Portland cement—a binder known for its high carbon emissions—in concrete and mortar production. The abundant pyroclastic material, currently a waste burden for the residents of Sakurajima and the Kagoshima Bay region, presents a unique opportunity for valorization in line with circular economy principles. Rather than treating this ash as a disposal problem, the research investigates its transformation into a valuable supplementary cementitious material (SCM), contributing to more sustainable construction practices. The investigation focused on the material characterization of the ash (including chemical composition, morphology, and PSD) and its pozzolanic activity index, which is a key indicator of its suitability as a cement replacement. Mortars were prepared with 25% of the commercial binder replaced by volcanic ash—both in its raw form and after mechanical activation—and tested for compressive strength after 28 and 90 days of water curing. Additional assessments included workability of the fresh mix (flow table test), apparent density, and flexural strength of the hardened composites. Tests results showed that the applied volcanic ash did not influence the workability of the mix and showed negligible effect on the apparent density (changes of up to 3.3%), although the mechanical strength was deteriorated (decrease by 15–33% after 7 days, and by 25–26% after 28 days). However, further investigation revealed that the simple mechanical grinding significantly enhances the pozzolanic reactivity of Sakurajima ash. The ground ash achieved a 28-day activity index of 81%, surpassing the 75% threshold set by EN 197-1 and EN 450-1 standards for type II mineral additives. These findings underscore the potential for producing low-carbon mortars and concretes using locally sourced volcanic ash, supporting both emissions reduction and sustainable resource management in construction. Full article

This study evaluated the feasibility of reusing abandoned copper mine tailings (Cu tailings) as a precursor in the production of fly-ash-based alkali-activated materials (FA-AAMs). Two formulations were developed by combining FA and Cu tailings with a mixture of sodium silicate and sodium hydroxide as alkaline activators at room temperature (20 °C). Formulation G1 consisted of 70% Cu tailings and 30% fly ash (FA), whereas G2 included the same composition with an additional 15% ordinary Portland cement (OPC). The materials were characterized using X-ray fluorescence (XRF), -X-ray diffraction (XRD), field emission scanning electron microscopy with energy-dispersive spectroscopy (FESEM-EDS), and particle size analysis. While FA exhibited a high amorphous content (64.4%), Cu tailings were largely crystalline and acted as inert fillers. After 120 days of curing, average compressive strength reached 24 MPa for G1 and 41 MPa for G2, with the latter showing improved performance due to synergistic effects of geopolymerization and OPC hydration. Porosity measurements revealed a denser microstructure in G2 (35%) compared to G1 (52%). Leaching tests confirmed the immobilization of hazardous elements, with arsenic concentrations decreasing over time and remaining below regulatory limits. Despite extended setting times (24 h for G1 and 18 h for G2) and the appearance of surface efflorescence, both systems demonstrated good chemical stability and long-term performance. The results support the use of Cu tailings in FA-AAMs as a sustainable strategy for waste valorization, enabling their application in non-structural and moderate-load-bearing construction components or waste encapsulation units. This approach contributes to circular economy goals while reducing the environmental footprint associated with traditional cementitious systems. Full article

The dataset presented in this manuscript consists of three distinct sets of data collected during a laboratory experiment aimed at quantifying the emissions of greenhouse gases (GHGs), specifically methane (CH₄), carbon dioxide (CO₂), and nitrous oxide (N₂O). The experiment was conducted in three phases, each initiated at different times. The first phase began on 6 June 2022, using a biocover composed of 60% fine-fraction waste, 20% clay soil, and 20% stabilized compost. The second phase commenced on 26 August 2022, with two biocover variants: one composed of 50% fine-fraction waste and 50% clay soil, and the other consisting of 40% fine-fraction waste, 40% clay soil, and 20% shredded paper. The final phase started on 27 October 2022, introducing two biocovers: one containing 25% dried algae, 25% fine-fraction waste, 25% gravel (0–20 mm), and 25% ash, and the other composed of 40% fine-fraction waste, 40% dried algae, and 20% chernozem. Emission assessments were conducted three weeks after the biocover installation to allow for settling and stabilization, followed by weekly measurements two to three days before irrigation with 250 mL of water to simulate field conditions. GHG emission quantification was carried out using the Cavity Ring-Down Spectroscopy gas measurement device, Picarro G2508. This dataset offers substantial scientific value for advancing biocover technologies aimed at reducing GHG emissions in landfill environments, particularly for mitigating methane emissions. In addition to initial experimental use, the dataset offers a wide range of possibilities for reuse, including modeling landfill gas emissions, validating gas flow measurement methods, developing machine learning models, and performing meta-analyses. Its detailed structure facilitates multi-faceted environmental research and supports optimization of landfill management. Full article

Portugal’s commitment to carbon neutrality by 2050 has intensified the search for renewable energy alternatives, with biomass gasification emerging as a promising pathway for hydrogen production. This comprehensive review analyzes the potential of 39 Portuguese biomass species for gasification processes, based on extensive laboratory characterization data including proximate analysis, ultimate analysis, heating values, and metal content. The studied biomasses encompass woody shrubland species (matos arbustivos lenhosos), forest residues, and energy crops representative of Portugal’s diverse biomass resources. Results indicate significant variability in gasification potential, with moisture content ranging from 0.5% to 14.9%, ash content from 0.5% to 5.5%, and higher heating values between 16.8 and 21.2 MJ/kg. Theoretical hydrogen yield calculations suggest that Portuguese biomasses could produce between 85 and 120 kg H₂ per ton of dry biomass, with species such as Eucalyptus globulus, Pinus pinaster, and Cytisus multiflorus showing the highest potential. Statistical analysis reveals strong negative correlations between moisture content and hydrogen yield potential (r = −0.63), while carbon content shows positive correlation with gasification efficiency. The comprehensive characterization provides essential data for optimizing gasification processes and establishing Portugal’s biomass-to-hydrogen production capacity, contributing to the national hydrogen strategy and renewable energy transition. Full article

Geopolymers are typically cured either at ambient temperature (~25 °C) or subjected to short-term heat curing before being stored under ambient conditions until testing. However, in hot-arid regions, the daily ambient temperature may exceed 45 °C during summer months. Therefore, such conditions should also be considered as high ambient curing, and their influence on low-calcium geopolymer performance needs to be investigated. In this study, pumice- and fly ash-based geopolymer mortars were produced to evaluate the effects of different curing regimes. In the pumice-based mixtures, 10 wt% of pumice was replaced with metakaolin to enrich the alumina content. Three curing conditions were applied: ambient curing, high ambient curing, and heat curing. Setting times of geopolymers were determined based on each curing regime. Physical properties, including density, water absorption, and sorption coefficient, were assessed. Compressive strength development was evaluated over 90 days. In addition, durability performance was assessed through water resistance, freeze–thaw durability, and resistance against sulphuric and hydrochloric acid. Fourier transform infrared spectroscopy and X-ray diffraction confirmed that geopolymerisation reactions continued significantly up to 90 days under high ambient curing, while mercury intrusion porosimetry showed a reduction in porosity. These findings explain the continuous increase in compressive strength. Pumice-based geopolymers cured under this condition exhibited significantly better long-term strength than those cured under other regimes. High ambient-cured fly ash-based geopolymers, a 3-day strength of 40.3 MPa was achieved, eliminating the need for heat curing. Thus, high ambient curing enables the in situ use of these geopolymers and offers a cost-effective and eco-friendly alternative. Full article

Alkali-activated fly ash and slag binders are regarded as environmentally friendly building materials. However, the creep properties of the alkali-activated materials differ from ordinary Portland cement-based materials. Currently, predicting the creep properties of alkali-activated materials is difficult. This study tested the creep properties of alkali-activated materials with various strengths and loading ages, exploring the similarities and differences in the creep properties between alkali-activated and cement-based materials. The result shows that the creep development of alkali-activated materials still conforms to the law of the hyperbolic power function commonly used to describe that of cement-based materials. Nevertheless, the proportion of the basic creep increases to about 70% of the drying creep in alkali-activated materials at 90 days. By modifying the parameters related to the relative humidity in the model of CEB-FIP MC2010, the creep behavior of alkali-activated fly ash and slag concrete could be well predicted. Full article

The manufacture of Portland cement (PC) emits a significant amount of CO₂ into the atmosphere. Therefore, the partial replacement of PC by supplementary cementitious materials (SCMs) possessing pozzolanic properties is considered a viable strategy to reduce its environmental impact. Recently, waste glass (WG) has been explored as a potential SCM. However, due to the wide variety of glass types and their differing physical and chemical properties, not all WG can be universally considered suitable for this purpose; therefore, this study investigates the use of recycled WG as an SCM for the partial replacement of PC. Two types of WG were evaluated: green waste glass from wide bottles (GWG) and laboratory waste glass (LWG), and their performance was compared to that of fly ash (FA). The physical, mechanical, and pozzolanic properties of the materials were assessed. Results show that both types of WG exhibit particle size distributions comparable to PC and have contents of SiO₂, Al₂O₃, and Fe₂O₃ exceeding 70%. Chemical, mineralogical, and pozzolanic analyses revealed that both GWG and LWG presented higher pozzolanic activity than FA, particularly at later ages. Notably, LWG demonstrated the most significant contribution to mechanical strength development. These findings suggest that recycled waste glass, especially LWG, can serve as a viable and sustainable SCM, contributing to the reduction of the environmental footprint associated with Portland cement production. Full article