Search Results (603)

This paper presents the development and characteristics of geopolymer foams modified with paraffin-based phase change materials (PCMs) encapsulated in diatomite. The aim was to increase both the thermal insulation and heat storage capacity of the foams while maintaining sufficient mechanical strength for construction applications. Eleven variants of composites with different PCM fractions (5–10% by mass) and grain sizes (<1.6 mm to >2.5 mm) were synthesized and tested. The inclusion of PCM encapsulated in diatomite modified the porous structure: the total porosity increased from 6.6% in the reference sample to 19.6% for the 1.6–1.8 mm_10% wt. variant, with pore diameters ranging from ~4 to 280 µm. Thermal conductivity (λ) ranged between 0.090–0.129 W/m·K, with the lowest values observed for composites 2.0–2.5 mm_5–10% wt. (≈0.090–0.091 W/m·K), which also showed high thermal resistance (R ≈ 0.287–0.289 m²·K/W). The specific heat (Cp) increased from 1.28 kJ/kg·K (reference value) to a maximum value of 1.87 kJ/kg·K for the 2.0–2.5 mm_10% mass variant, confirming the effective energy storage capacity of PCM-modified foams. Mechanical tests showed compressive strength values in the range of 0.7–3.1 MPa. The best structural performance was obtained for the 1.6–1.8 mm_10% wt. variant (3.1 MPa), albeit with a higher λ (≈0.129 W/m·K), illustrating the classic trade-off between porosity-based insulation and mechanical strength. SEM microstructural analysis and mercury porosimetry confirmed the presence of mesopores, which determine both thermal and mechanical properties. The results show that medium-sized PCM fractions (1.6–2.0 mm) with moderate content (≈10% by weight) offer the most favorable compromise between insulation and strength, while thicker fractions (2.0–2.5 mm) maximize thermal energy storage capacity. These findings confirm the possibility of incorporating natural PCMs into geopolymer foams to create multifunctional materials for sustainable and energy-efficient building applications. A unique contribution to this work is the use of diatomite as a natural PCM carrier, ensuring stability, compatibility, and environmental friendliness compared to conventional encapsulation methods. Full article

This study investigates the effects of slag and silica fume on the mechanical properties, transport behavior, and pore structure of cement-based mortars. Mortars incorporating different proportions of supplementary materials were evaluated by compressive and flexural strength, saturated water absorption, chloride permeability, and mercury intrusion porosimetry (MIP). Fractal analysis was further applied to assess pore structure complexity. At 28 days, the slag–silica fume blend SG20SF10 reached 46.5 MPa in compressive strength and 5.8 MPa in flexural strength, exceeding OPC. MIP showed a decrease in total porosity from ~14.5% to ~11.3% (about 22% lower) with a marked reduction in pores larger than 100 nm. Consistently, SG20SF10 exhibited the lowest water absorption and chloride permeability at both ages. These results indicate that the slag–silica fume synergy refines capillary porosity and increases pore-network complexity, thereby reducing directional connectivity and transport. Full article

This review provides a comprehensive examination of porosity and permeability as key parameters governing the durability and performance of construction materials, including natural stone, mortar, concrete, and other cementitious composites. It highlights the pivotal role of pore structure in transport phenomena and degradation mechanisms, examining how the variations in pore architecture, encompassing total vs. effective porosity, pore size distribution, and pore connectivity, dictate a material’s response to environmental stressors. A comparative evaluation of advanced pore characterization techniques is presented, including helium pycnometry, mercury intrusion porosimetry (MIP), nitrogen adsorption (BET/BJH), nuclear magnetic resonance (NMR) relaxometry, and imaging methods such as optical microscopy, scanning electron microscopy (SEM), and X-ray micro-computed tomography (micro-CT). Furthermore, it assesses how these porosity and permeability characteristics influence durability-related processes like freeze–thaw cycling, chloride ingress, sulphate attack, and carbonation. Case studies are discussed in which various additives have been employed to refine the pore structure of cement-based materials, and pervious concrete is highlighted as an example where deliberately high porosity and permeability confer functional benefits (e.g., enhanced drainage). Overall, these insights underscore the importance of tailoring porosity and permeability in material design to enhance durability and sustainability in construction engineering. Full article

Shale reservoirs offer significant potential for CO₂ geological sequestration due to their extensive nanopore networks and heterogeneous pore systems. This study comparatively assessed the CO₂ storage potential of the Lower Silurian Longmaxi and Lower Cambrian Qiongzhusi shales through an integrated approach involving organic geochemical analysis, mineralogical characterization through X-ray diffraction (XRD), mercury intrusion capillary pressure (MICP), low-pressure nitrogen and carbon dioxide physisorption, field-emission scanning electron microscopy (FE-SEM), stochastic 3D microstructure reconstruction, multifractal analysis, and three-dimensional succolarity computation. The results demonstrate that mineral assemblages and diagenetic history govern pore preservation: Longmaxi shales, with moderate maturity and shallower burial, retain abundant organic-hosted mesopores, whereas overmature and deeply buried Qiongzhusi shales are strongly compacted and mineralized, reducing pore availability. Multifractal spectra and 3D reconstructions reveal that Longmaxi develops broader singularity spectra and higher succolarity values, reflecting more isotropic meso-/macropore connectivity at the SEM scale, while Qiongzhusi exhibits narrower spectra and lower succolarity, indicating micropore-dominated and anisotropic networks. Longmaxi has nanometer-scale throats (D₅₀ ≈ 10–25 nm) with high CO₂ breakthrough pressures (P₁₀ ≈ 0.57 MPa) and ultra-low RGPZ permeability (mean ≈ 1.5 × 10⁻² nD); Qiongzhusi has micrometer-scale throats (D₅₀ ≈ 1–3 μm), very low breakthrough pressures (P₁₀ ≈ 0.018 MPa), and much higher permeability (mean ≈ 4.63 × 10³ nD). Storage partitioning further differs: Longmaxi’s median total capacity is ≈15.6 kg m⁻³ with adsorption ≈ 93%, whereas Qiongzhusi’s median is ≈12.8 kg m⁻³ with adsorption ≈ 70%. We infer Longmaxi favors secure adsorption-dominated retention but suffers from injectivity limits; Qiongzhusi favors injectivity but requires reliable seals. Full article

The root causes forcing the differential pore-throat performances and crude oil recoverability in heterogeneous shale lithofacies of saline-lacustrine fine-grained mixed sedimentary sequences are still debated. Especially application cases of fractal theory in characterizing pore-throat heterogeneity are still lacking and the significance of differential multifractal distribution patterns on reservoir assessment remains controversial. This present study focuses on the shale-oil reservoirs in saline-lacustrine fine-grained mixed depositional sequences of the Middle Permian Lucaogou Formation (southern Junggar Basin, NW China), and presents a set of new results from petrographical investigation, field-emission scanning electron microscopy (FE-SEM) imaging, fluid injection experiments (low-pressure N₂ adsorption and high-pressure mercury intrusion porosimetry (HMIP)), nuclear magnetic resonance (NMR) spectroscopy and T₁-T₂ mapping, directional spontaneous imbibition, as well as contact angle measurements. Our results demonstrated that the investigated lithofacies are mainly divided into a total of five lithofacies categories: felsic siltstones, sandy dolomitic sandstones, dolarenites, micritic dolomites, and dolomitic mudstones, respectively. More importantly, the felsic siltstone and sandy dolomitic siltstones can be identified as the most advantageous lithofacies categories exhibiting the strongest movable oil-bearing capacity owing to an acceptable complexity and heterogeneity of mesopore-throat structures, as evidenced by the corresponding moderate fractal dimension of mesopores (D₂) from HMIP and apparently lower fractal dimension of movable fluids’ pores (D₂) from NMR results. Particularly noteworthy is the relatively poor shale-oil movability recognized in the dolarenites, micritic dolomites, and dolomitic mudstones due to heterogeneous and unfavorable pore-throat systems, even though an acceptable micro-connectivity and a more oleophilic interfacial wettability prevails in crucial dolomitic components. Finally, a comprehensive and conceptual model is established for an effective and characteristic parameter system for assessing differential reservoir petrophysical properties, interfacial wettability, and shale-oil movability concerning heterogeneous lithofacies categories. Our achievements can serve as an analog for investigating saline-lacustrine mixed shale-oil reservoirs to gain a more comprehensive understanding of differential recoverability of dessert reservoir intervals, and to guide the assessment of “sweet spots” distribution and optimization of engineering technique schemes for commercial exploitation. Full article

While studies have shown that heavy metal sulfides in sediments are not bioavailable, most of them are acid-extractable (AE) and inseparable from non-sulfides in sediments. Exceptions were found recently that mercury and copper sulfides precipitated in sediments are non-AE because they are exclusively bi-sulfides. Therefore, quantifying mercury sulfide in sediments is possible for bioavailability assessment. To illustrate the application of this new approach for mercury bioavailability assessment, we quantified the distribution of mercury sulfide in sediments of the Apalachicola Bay, North Florida, USA. We extracted sediment cores and determined the total mercury, non-sulfide mercury, and sulfide mercury as well as the total sulfides, bulk density, and organic matter. The results showed that the mercury in the top 45 cm sediments were, on average, 13.3 ± 5.4 ng/cm³, of which 97.1 ± 2.5% were sulfide. The potentially bioavailable (non-sulfide) mercury was on average only 0.28 ± 0.22 ng/cm³ (2.9% of the total mercury). The total mercury and sulfide mercury were significantly correlated with the organic matter, which were dictated by the discharge pattern of the river input. This study demonstrates that aquatic sediments accumulate terrestrial mercury, and sulfidic sediments sequester most of it as sulfide. This new approach for mercury bioavailability assessment is simple yet chemically rigorous. Full article

The impact of mercury (Hg) on biological systems is well documented; however, the long-term effects of low-level exposure in children remain unclear, particularly with respect to oxidative stress and cognitive outcomes. This study evaluated Hg exposure and its associations with the gene expression and intelligence quotient (IQ) in two Afro-descendant child populations in Colombia. Hair total mercury (T-Hg) was quantified in 163 children under 7 years old, along with their sociodemographic data. Significant differences (p < 0.05) were found in fish consumption and mean hair T-Hg concentrations between children from Mahates (2.66 ± 0.30 meals/week; 0.32 ± 0.03 µg/g) and Zanjón (1.24 ± 0.09 meals/week; 0.24 ± 0.01 µg/g). The gene expression analysis revealed higher SOD1 expression in Mahates. The mean IQ scores were higher in Zanjón (74.7) than those in Mahates (71.7). Overall, Spearman’s correlation analysis showed no significant associations (p > 0.05) between T-Hg and the measured variables. The principal component analysis (PCA) revealed a clear separation between populations: Mahates, associated with a higher mercury burden and the upregulation of stress-response genes, and Zanjón, characterized by a better cognitive performance and lower mercury exposure. These findings suggest that despite the low overall exposure and non-significant bivariate correlations, the communities displayed distinct profiles, highlighting the value of integrated molecular–cognitive biomonitoring and motivate longitudinal studies addressing co-exposures and socioeconomic confounding. Full article

Western Pará, northern Brazil, is a significant region for mineral exploration, leading to the deposition of potentially toxic elements in soils and water basins. This study evaluated concentrations of mercury (Hg), lead (Pb), cadmium (Cd), and arsenic (As) in cattle muscle tissue from three municipalities: Oriximiná, Itaituba, and Monte Alegre. Metal concentrations were determined using inductively coupled plasma mass spectrometry (ICP-MS). The estimated daily intake (EDI) of toxic metals via beef consumption (71 g/person/day) was below oral reference doses values (RfDo). Target hazard quotient (THQ) and total THQ (TTHQ) values for all metals were below 1, indicating no significant non-carcinogenic health risk. Monte Alegre exhibited the highest THQ for As and Pb, Oriximiná for Cd, and Itaituba for Hg. Although the overall assessment suggests low risk, elevated Hg concentrations were detected in 10% of the samples, with at least one animal from each municipality exceeding the European Union maximum residue limit (0.01 mg/kg). These findings indicate localized contamination and potential mercury bioaccumulation. Given the rising anthropogenic activities (such as mining and deforestation), continued monitoring of heavy metal levels in animal tissues is recommended to ensure long-term food safety and public health. Full article

This study aims to evaluate the feasibility of using the mussel as a bioindicator for the rapid detection of heavy metal (such as Cd, Pb, Hg, Ni, Cr, Cu, As, and Zn) fluctuations in aquatic environments and the sensitivity of the bioaccumulation of heavy metals in muscle tissues over time. The seasonal bioaccumulation patterns of heavy metals within Asian green mussels (Perna viridis), from Vietnamese coastal waters of Hai Phong were investigated using inductively coupled plasma mass spectrometry (ICP-MS). Additionally, the health risks from the consumption of P. viridis by local people were assessed. Mussels of varying sizes were sampled on a monthly basis between March (dry season) and July 2024 (wet season). The results revealed that the hepatopancreas had substantially higher concentrations of metals at all times relative to their corresponding muscle tissues, confirming its appropriateness as a bioindicator organ. The concentrations of heavy metals in mussels were recorded as significantly lower than the guideline levels, except for arsenic (As). Zinc (Zn) showed the highest concentrations, while mercury (Hg) had the lowest concentrations. There were strong seasonal and monthly differences, with peak levels of Pb, Cr, and As during the dry season, and high levels of Cs and Cu during the rainy season. It was found that the condition index, physiological factors, and shell size all had major impacts on the absorption of specific heavy metals. It was indicated that Pb, Cr, As, Cs, and Cu bioaccumulation are both biologically and environmentally responsive and can be used as proxies for environmental contamination, while the accumulation of these metals correlated with biological traits (shell length, weight, and CI), which is useful in modeling efforts. Health risk assessments using target hazard quotients (THQs) and the total hazard index (THI) identified Pb in the hepatopancreas as a primary contributor to the non-carcinogenic risk (THQ > 1), particularly during the dry season. The findings revealed the suitability of P. viridis, particularly hepatopancreatic tissue, as a short-term biomonitoring tool for detecting spikes and rapid fluctuations of certain heavy metals and assessing related human health risks in coastal aquatic systems. Full article

Introduction: Globally, approximately 53 million children under the age of five live with some form of developmental disability. Exposure to heavy metals has been identified in the literature as a contributing factor in the etiology of neurodevelopmental disorders, however it usually is understudied. Even at low concentrations, these toxicants pose a risk to neurodevelopment, when affecting children early as in the prenatal period. This study aims to systematically review the literature on the associations between exposure to toxic heavy metals and neurodevelopmental outcomes in children. Method: The review was registered at the International Prospective Register of Systematic Review-PROSPERO, under number CRD420250653229 and searches were conducted in the PubMed, Scopus, Web of Science, EMBASE, Lilacs and PsycInfo databases. Results: A total of 68 articles were included, comprising 48 longitudinal studies and 20 cross-sectional studies, published between 2006 and 2025, with a combined sample of 215,195 individuals from 23 countries. Lead was the most consistently investigated metal, appearing in 75% of the studies, followed by mercury, cadmium, and arsenic. Most findings referred to prenatal exposure. Cognitive and motor outcomes were predominantly affected by exposure to Pb and Hg, while behavioral outcomes showed negative associations mainly with Pb and As. Conclusions: The majority of the studies analyzed indicated adverse effects resulting from exposure to heavy metals during pregnancy, especially in the early months, highlighting the vulnerability of the developing brain. Full article

Chemical hazards in food present a significant health risk. The objective of our review is to understand health risks associated with chemical contaminants in products of animal origin (POAO) in Cambodia, where there is no known published study. We followed the “Preferred Reporting Items for Systematic Reviews and Meta-Analyses” (PRISMA) guidelines. A total of 23 reports were included for review. The findings are presented according to the PRISMA guidelines. The studies mostly focused on fishery products, with arsenic and mercury being the most frequently studied hazards. The evidence of banned substances such as chloramphenicol and certain organochlorine pesticides (OCPs), including chlordane and Mirex, was reported in fish and meat. Additionally, mercury levels were measured in beef, pork, viscera, and eggs, but the average concentration remained significantly below the hazard index. The average concentration of polycyclic aromatic hydrocarbons (PAH) in smoked fish exceeded the EU limits, ranging from 0.034 to 17.2 mg/kg, with an average mean concentration of 1.92 mg/kg. The pooled geometric means of arsenic and mercury in fish were 0.40 mg/kg (95% CI: 0.25–0.66) and ~0.14 mg/kg (95% CI: 0.087 to 0.223), respectively. The health risk of mercury contamination in fishery products needs the attention of the risk managers. However, industrial contaminants such as polybrominated diphenyl ethers (PBDEs) and butyl tin in marine fishes were lower than those reported elsewhere, such as Japan. We discuss the implications of the findings for human health and national food control systems (NFCS), the capacity of different agencies to undertake chemical risk assessment, the utility of systematic literature reviews (SLRs) for risk assessment and communication in low- and middle-income countries (LMICs), and the need for further research. Full article

Ordinary steel slag serves as a supplementary cementitious material (SCMs) to enhance the resource efficiency of industrial waste and contribute to decarbonization and economic benefits. However, there are significant differences in the composition and properties between hot–stuffy steel slag and ordinary steel slag, and there has been little research focusing on hot–stuffy steel slag as an SCM. Herein, we investigated the application of hot–stuffy steel slag, coal bottom ash, slag powder, desulfurization gypsum, and cement as raw materials for developing new green, low-carbon, and economical cementitious materials. When the hot–stuffy steel slag content was 20%, the compressive and flexural strengths of the cementitious material at 28 days reached as high as 64.5 MPa and 11.3 MPa, respectively. Even when the hot–stuffy steel slag content is increased to 50%, the compressive and flexural strengths at 28 days remain 58.2 MPa and 6.1 MPa, respectively. Furthermore, an X-ray diffractometer (XRD) and scanning electron microscopy (SEM) show that the hydration products generated by the new low-carbon cementitious materials (LCM) are mainly C-(A)-S-H gels. Mercury intrusion porosimetry (MIP) indicates that when the hot–stuffy steel slag content is 20%, the total porosity (18.85%) of the LCM is the lowest, suggesting that the lower the porosity, the better the strength. Notably, the heavy metal ions released by hot–stuffy steel slag-based cementitious materials were far below hygienic standards for drinking water, confirming their ability to fix heavy metal ions. This work provides an excellent model and application prospect for the utilization of hot–stuffy steel slag in non-structural engineering projects such as river engineering, marine engineering, and road engineering, enabling the achievement of both low-carbon and economic objectives. Full article

Cement manufacturing is the second largest anthropogenic source of Hg emissions in the environment. Therefore, the establishment of analytical methodologies that can be utilized in the determination of Hg concentration from cement raw materials and cement is of great importance. The total Hg and Hg thermospecies in cement raw materials and cements were determined by thermal desorption techniques with a Zeeman Hg analyzer. No chemical pre-treatment of samples is required for this technique prior to analysis. An optimum single-stage temperature program was applied to determine total Hg at an optimum heating rate of approximately 5 °C s⁻¹ while Hg thermospecies were determined over four stages at an optimum heating rate of approximately 0.2 °C s⁻¹ per stage from ambient temperature to 720 °C. Total mercury concentrations in cement raw materials ranged between 2.19 ng g⁻¹ and 395 ng g⁻¹, while in cement, concentrations ranged between 1.32 ng g⁻¹ and 31.0 ng g⁻¹. The highest Hg contents were found in dust return (580 ng g⁻¹ and 679 ng g⁻¹). Hg thermospecies determination showed that cement raw materials and cements contain one Hg thermospecies that is released at 20–180 °C while dust return contained one to four Hg thermospecies that could be released at 20–180 °C, 180–360 °C, 360–540 °C, and/or 540–720 °C, thus indicating that new Hg compounds are formed during cement production. Full article

Shale pore architecture governs gas storage capacity, permeability, and production potential in reservoirs. Therefore, this study systematically investigates the pore structure features and influencing factors of the Niutitang Formation shale from the QX1 well in northern Guizhou using field emission scanning electron microscopy (FE-SEM), high-pressure mercury intrusion (HPMI), low-temperature nitrogen adsorption (LTNA), and nuclear magnetic resonance (NMR) experiments. The results show that ① The pore size of the QX1 well’s Niutitang Formation shale is primarily in the nanometer range, with pore types including intragranular pores, intergranular pores, organic matter pores, and microfractures, with the former two types constituting the primary pore network. ② Pore shapes are plate-shaped intersecting conical microfractures or plate-shaped intersecting ink bottles, ellipsoidal, and beaded pores. ③ The pore size distribution showed a multi-peak distribution, predominantly mesopores, followed by micropores, with the fewest macropores. ④ The fractal dimension D₁ > D₂ indicates that the shale pore system is characterized by a rough surface and some connectivity of the pore network. ⑤ Carbonate mineral abundances are the main controlling factors affecting the pore structure of shales in the study area, and total organic carbon (TOC) content also has some influence, while clay mineral content shows negligible statistical correlation. Full article

Introduction: Oxidative stress is a key factor in the pathogenesis of many chronic diseases, especially in postmenopausal women. Xylitol, a sugar alcohol with potential antioxidant properties, may affect oxidative balance when used as a sugar substitute. Aim: This pilot study aimed to assess the effect of replacing sucrose with xylitol on serum antioxidant capacity in postmenopausal women. Methods: This study included 34 women aged 50 to 65 years who successively consumed 5 g/d, 10 g/d, and 15 g/d of xylitol. The dietary intervention lasted a total of 6 weeks, with each phase covering a 2-week period. Diet was assessed twice based on a 7-day dietary interview (Diet 6.0, NIZP–PZH, Warsaw). The material for this study was venous blood. Antioxidant capacity was determined using the DPPH radical scavenging method and the ABTS cation radical scavenging method. Results: In both methods, a significant increase in serum antioxidant potential was observed after replacing sugar with xylitol (p < 0.0001). An increase in the ability to neutralize free radicals was observed in almost all women studied. Additional analysis of the effect of selected nutrients on the obtained effects of the nutritional intervention showed that the most significant effect could potentially be exerted by manganese, maltose, sucrose, and mercury, and the strongest positive correlation was exerted by vitamin A, retinol, and vitamin E. Although the values obtained in the constructed models were not statistically significant, the large effect indicates potentially significant relationships that could have a significant impact on serum antioxidant potential in the studied group of women. Conclusions: The results suggest a potential role of xylitol in enhancing antioxidant defense mechanisms in menopausal women. Although the sample size was relatively small, this study was powered at approximately 80% to detect large effects, supporting the reliability of the observed results. Nevertheless, given the pilot nature of this study, further research with larger cohorts is warranted to confirm these preliminary observations and to clarify the clinical significance of xylitol supplementation in populations exposed to oxidative stress. Full article