Sign in to use this feature.

Years

Between: -

Subjects

remove_circle_outline
remove_circle_outline
remove_circle_outline
remove_circle_outline
remove_circle_outline
remove_circle_outline
remove_circle_outline
remove_circle_outline

Journals

Article Types

Countries / Regions

Search Results (56)

Search Parameters:
Keywords = fine-earth fraction

Order results
Result details
Results per page
Select all
Export citation of selected articles as:
18 pages, 2083 KiB  
Article
Quantification of Microplastics in Urban Compost-Amended Farmland Soil Using an Elutriation Device
by Luigi Paolo D’Acqui, Sara Di Lonardo, Martina Grattacaso, Alessandra Bonetti and Ottorino-Luca Pantani
Agronomy 2025, 15(7), 1736; https://doi.org/10.3390/agronomy15071736 - 18 Jul 2025
Viewed by 228
Abstract
Microplastics (MPs) present in farmland soils, where urban compost has been distributed since 2005, were extracted using a device based on elutriation, a method developed for marine sediments but not yet used in soil. Since (i) fine earth (diameter < 2 mm) is [...] Read more.
Microplastics (MPs) present in farmland soils, where urban compost has been distributed since 2005, were extracted using a device based on elutriation, a method developed for marine sediments but not yet used in soil. Since (i) fine earth (diameter < 2 mm) is the standard fraction used for soil analysis and (ii) the size of MPs contained in urban compost may exceed that value, MP were recovered from both the entire soil and fine earth. The recovered MPs pieces were weighed, counted, and characterized using FTIR photoacoustic spectroscopy (FTIR-PAS). Both the mass and number of recovered MPs pieces (>34 µm) were comparable to those reported in the literature for soils. Polystyrene, polyethylene, and polypropylene are the primary polymers. Nevertheless, some issues were highlighted: (i) the importance of sampling the soil by volume, and (ii) the need of analyzing the entire soil sample rather than just the fraction below 2 mm, commonly used in soil analysis; (iii) the necessity of breaking up (i.e., by ultrasonication and/or dispersion) soil aggregates that may withstand the elutriation process. Full article
(This article belongs to the Section Agroecology Innovation: Achieving System Resilience)
Show Figures

Figure 1

16 pages, 2956 KiB  
Article
Utilization of Red Mud from Processing of Low-Quality Bauxites
by Sergey Gladyshev, Nazym Akhmadiyeva, Rinat Abdulvaliyev, Leila Imangaliyeva, Kenzhegali Smailov, Yerkezhan Abikak, Asya Kasymzhanova and Leila Amanzholova
Processes 2025, 13(7), 1958; https://doi.org/10.3390/pr13071958 - 20 Jun 2025
Viewed by 323
Abstract
Red mud from bauxite processing is among the large-tonnage technogenic waste that poses a significant ecological threat. At the same time, red mud serves as a raw material source for expanding the resource base for obtaining iron, rare metals, and rare earth elements. [...] Read more.
Red mud from bauxite processing is among the large-tonnage technogenic waste that poses a significant ecological threat. At the same time, red mud serves as a raw material source for expanding the resource base for obtaining iron, rare metals, and rare earth elements. Numerous studies on their utilization have shown that only through comprehensive processing, combining pyrometallurgical and hydrometallurgical methods, is it possible to maximize the extraction of all the useful components. This work addresses the first stage of a comprehensive technology for processing red mud through reduction smelting, separating iron in the form of pig iron, and producing slag. Studies were conducted on the reductive smelting of red mud using waste slurry from alumina production as the calcium-containing material, taken in proportions calculated to obtain a fluid slag with a hydraulic modulus of 0.55–0.8. The permissible mixing range of red mud with waste slurry was determined to be in the ratio of 0.56–1.2. In cases where the charge was prepared in violation of the required hydraulic modulus value, pig iron was not obtained during smelting. When the hydraulic modulus requirement was met, the temperature of the reductive smelting process was 1350–1400 °C. The total amount of recovered iron obtained as pig iron and fine fractions amounted to 99.5% of the original content. The low iron content (0.23–0.31%) in the non-magnetic slag fraction allows for the production of high-quality titanium oxide and rare earth element concentrates in the subsequent stages of the comprehensive hydrometallurgical processing of red mud, involving acid leaching. Based on the results of a phase analysis of the slag, pig iron, and melt, the reactions of the reductive smelting process were established, and their thermodynamic likelihood was determined. In fluid slags, the content of the sodium aluminosilicate phase is twice as high as that in slag with a higher hydraulic modulus. The reductive smelting of 100% red mud with the addition of calcium oxide, calculated to achieve a hydraulic module of 0.55 at a temperature of 1350–1400 °C, produced pig iron and slag with high alkali and iron contents. Full article
(This article belongs to the Topic Advanced Materials in Chemical Engineering)
Show Figures

Figure 1

18 pages, 6276 KiB  
Article
Geochemical Survey of Stream Sediments and Stream Water for Ion-Adsorption Type Rare Earth Deposits (IAREDs): A Pilot Study in Jiaping IARED, Guangxi, South China
by Junhong Liu, Zhixuan Han, Chunfang Dong, Xiaocheng Wei and Yingnan Chen
Minerals 2025, 15(6), 642; https://doi.org/10.3390/min15060642 - 13 Jun 2025
Viewed by 431
Abstract
Rare earth elements (REEs) are critical mineral resources that play a pivotal role in modern technology and industry. Currently, the global supply of light rare earth elements (LREEs) remains adequate. However, the supply of heavy rare earth elements (HREEs) is associated with substantial [...] Read more.
Rare earth elements (REEs) are critical mineral resources that play a pivotal role in modern technology and industry. Currently, the global supply of light rare earth elements (LREEs) remains adequate. However, the supply of heavy rare earth elements (HREEs) is associated with substantial risks due to their limited availability. Ion-adsorption type rare earth deposits (IAREDs), which represent the predominant source of HREEs, have become a focal point for exploration activities, with a notable increase in global interest in recent years. This study systematically collected stream sediments and stream water samples from the Jiaping IARED in Guangxi, as well as from adjacent granitic and carbonate background areas, to investigate the exploration significance of geochemical surveys for IAREDs. Additionally, mineralized soil layers, non-mineralized soil layers, and bedrock samples from the weathering crust of the Jiaping deposit were analyzed. The results indicate that stream sediments originating from the Jiaping IARED and granite-hosted background regions display substantially elevated REE concentrations relative to those from carbonate-hosted background areas. Moreover, δEu values in stream sediments can serve as an effective indicator for differentiating weathering products derived from granitic and carbonate lithologies. Within the mining area, three coarse-grained fractions of stream sediments (i.e., +20 mesh, 20–60 mesh, and 60–150 mesh) exhibit REE concentrations comparable to those observed in both granite-hosted and carbonate-hosted background regions. However, the HREEs content in the finer -150-mesh stream sediments from Jiaping IARED is markedly higher than that in the two background regions. The (La/Sm)N versus (La/Yb)N ratios of -150-mesh stream sediments in the Jiaping IARED may reflect the mixing processes involving HREE-enriched ore layer, non-mineralized layer, and LREE-enriched ore layer. This observation implies that fine-grained (-150-mesh) stream sediments can partially inherit the REE characteristics of mineralized layers within IAREDs. Scanning electron microscopy (SEM) observations indicate that the enrichment of REEs in fine-grained stream sediments primarily originates from REE-rich accessory minerals derived from parent rocks and mineralized weathering crusts. A comparative analysis reveals that the concentrations of REEs in stream water collected during the rainy season are significantly higher than those collected during the dry season. Moreover, the levels of REEs, especially HREE, in stream water from the Jiaping IARED substantially exceed those in background areas. Collectively, these findings suggest that the geochemical signatures of REEs in rainy season stream water possess diagnostic potential for identifying IAREDs. In conclusion, the integrated application of geochemical surveys of stream water and -150-mesh stream sediments can effectively delineate exploration targets for IAREDs. Full article
(This article belongs to the Special Issue Novel Methods and Applications for Mineral Exploration, Volume III)
Show Figures

Figure 1

25 pages, 17504 KiB  
Article
The Influence of Rare Earth Metals on the Microstructure and Mechanical Properties of 220 and 356.1 Alloys for Automotive Industry
by Herbert W. Doty, Shimaa El-Hadad, Ehab Samuel, Agnes M. Samuel and Fawzy H. Samuel
Materials 2025, 18(5), 941; https://doi.org/10.3390/ma18050941 - 21 Feb 2025
Cited by 1 | Viewed by 602
Abstract
Application of rare earths (RE) as grain refiners is well-known in the technology of aluminum alloys for the automotive industry. In the current study, Al-2.4%Cu-0.4%Mg alloy (coded 220) and Al-7.5%Si-0.35%Mg alloy (coded 356.1), were prepared by melting each alloy in a resistance furnace. [...] Read more.
Application of rare earths (RE) as grain refiners is well-known in the technology of aluminum alloys for the automotive industry. In the current study, Al-2.4%Cu-0.4%Mg alloy (coded 220) and Al-7.5%Si-0.35%Mg alloy (coded 356.1), were prepared by melting each alloy in a resistance furnace. Strontium (Sr) was used as a modifier, while titanium boride (TiB2) was added as a grain refiner. Measured amounts of Ce and La were added to both alloys (max. 1 wt.%). The alloy melts were poured in a preheated metallic mold. The main part of the study was conducted on tensile testing at room temperature. The results show that although RE would cause grain refining to be about 30–40% through the constitutional undercooling mechanism, grain refining with TiB2 would lead to approximately 90% refining (heterogenous nucleation mechanism). The addition of high purity Ce or La (99.9% purity) has no modification effect regardless of the alloy composition or the concentration of RE. Depending on the alloy ductility, the addition of 0.2 wt.%RE has a hardening effect that causes precipitation of RE in the form of dispersoids (300–700 nm). However, this increase vanishes with the decrease in alloy ductility, i.e., with T6 treatment, due to intensive precipitation of ultra-fine coherent Mg2Si-phase particles. There is no definite distinction in the behavior of Ce or La in terms of their high affinity to interact with other transition elements in the matrix, particularly Ti, Fe, Cu, and Sr. When the melt was properly degassed using high-purity argon and filtered using a 20 ppi ceramic foam filter, prior to pouring the liquid metal into the mold sprue, no measurable number of RE oxides was observed. In conclusion, the application of RE to aluminum castings would only lead to formation of a significant volume fraction of brittle intermetallics. In Ti-free alloys, identification of Ce- or La-intermetallics is doubtful due to the fairly thin thickness of the precipitated platelets (about 1 µm) and the possibility that most of the reported Al, Si, and other elements make the reported values for RE rather ambiguous. Full article
Show Figures

Figure 1

17 pages, 51050 KiB  
Article
Towards Environmentally Friendly Buildings: An Assessment of the Mechanical Properties of Soil Mixtures with Graphene
by Federico Iorio Esposito, Paola Gallo Stampino, Letizia Ceccarelli, Marco Caruso, Giovanni Dotelli and Sergio Sabbadini
C 2025, 11(1), 16; https://doi.org/10.3390/c11010016 - 19 Feb 2025
Viewed by 677
Abstract
This study investigates the potential of graphene-based additives to improve the mechanical properties of compacted soil mixtures in rammed-earth construction, contributing to the development of environmentally friendly building materials. Two distinct soils were selected, combined with sand at optimized ratios, and treated with [...] Read more.
This study investigates the potential of graphene-based additives to improve the mechanical properties of compacted soil mixtures in rammed-earth construction, contributing to the development of environmentally friendly building materials. Two distinct soils were selected, combined with sand at optimized ratios, and treated with varying concentrations of a graphene liquid solution and a graphene-based paste (0.001, 0.005, 0.01, 0.05, and 0.1 wt.% relative to the soil-sand proportion). The effects of these additives were analyzed using the modified Proctor compaction and unconfined compressive strength (UCS) tests, focusing on parameters such as optimum water content (OWC), maximum dry density (MDD), maximum strength (qu), and stiffness modulus (E). The results demonstrated that graphene’s influence on compaction behavior and mechanical performance depends strongly on the soil composition, with minimal variation between additive types. In finer soil mixtures, graphene disrupted particle packing, increased water demand, and reduced strength. In silt–sandy mixtures, graphene’s hydrophobicity and limited interaction with fines decreased water absorption and preserved density but likewise led to diminished strength. Conclusions from the experiments suggest a possible interaction between graphene, soil’s finer fraction, and potentially the swelling and non-swelling clay minerals, providing insights into the complex interplay between soil properties. Full article
(This article belongs to the Topic Application of Graphene-Based Materials, 2nd Edition)
Show Figures

Graphical abstract

33 pages, 13410 KiB  
Article
Near-Time Measurement of Aerosol Optical Depth and Black Carbon Concentration at Socheongcho Ocean Research Station: Aerosol Episode Case Analysis
by Soi Ahn, Meehye Lee, Hyeon-Su Kim, Eun-ha Sohn and Jin-Yong Jeong
Remote Sens. 2025, 17(3), 382; https://doi.org/10.3390/rs17030382 - 23 Jan 2025
Viewed by 965
Abstract
This study examined the seasonal variations and influencing factors for black carbon (BC) concentrations and aerosol optical depth (AOD) at the Socheongcho Ocean Research Station (SORS) on the Korean Peninsula from July 2019 to December 2020. An AOD algorithm was developed and validated [...] Read more.
This study examined the seasonal variations and influencing factors for black carbon (BC) concentrations and aerosol optical depth (AOD) at the Socheongcho Ocean Research Station (SORS) on the Korean Peninsula from July 2019 to December 2020. An AOD algorithm was developed and validated using the Geo-KOMPSAT-2A (GK-2A) satellite. The GK-2A AOD demonstrated comparable performance to that of Low Earth Orbit satellites, including the Terra/MODIS (R2 = 0.86), Aqua/MODIS (R2 = 0.83), and AERONET AODs (R2 = 0.85). Multi-angle absorption photometry revealed that seasonal average BC concentrations were the highest in winter (0.91 ± 0.80 µg·m−3), followed by fall (0.80 ± 0.66 µg·m−3), wet summer (0.75 ± 0.55 µg·m−3), and dry summer (0.52 ± 0.20 µg·m−3). The seasonal average GK-2A AOD was higher in wet summer (0.45 ± 0.37 µg·m−3) than in winter. The effects of meteorological parameters, AERONET AOD wavelength, and gaseous substances on GK-2A AOD and BC were investigated. The SHapley Additive exPlanations-based feature importance analysis for GK-2A AOD identified temperature, relative humidity (RH), and evaporation as major contributors. BC concentrations were increased, along with PM2.5 and CO levels, due to the effects of combustion processes during fall and winter. Analysis of high-aerosol-loading cases revealed an increase in the fine-mode fraction, emphasizing the meteorological effects on GK-2A AOD. Thus, long-range transport and local BC sources played a critical role at the SORS. Full article
(This article belongs to the Special Issue Air Quality Mapping via Satellite Remote Sensing)
Show Figures

Figure 1

14 pages, 2877 KiB  
Article
A Methodology to Optimize Natural By-Product Mixes for Rammed Earth Construction Based on the Taguchi Method
by Miguel Angel Martin-Antunes, Eduardo Prieto, Beñat Garcia, Céline Perlot and Andrés Seco
Appl. Sci. 2024, 14(22), 10431; https://doi.org/10.3390/app142210431 - 13 Nov 2024
Cited by 2 | Viewed by 944
Abstract
In this investigation, the Taguchi method was employed to optimize a mix based on four natural by-products for rammed earth construction. Two separate studies were conducted to enhance the dry density and the Unconfined Compressive Strength (UCS). The four materials were assessed across [...] Read more.
In this investigation, the Taguchi method was employed to optimize a mix based on four natural by-products for rammed earth construction. Two separate studies were conducted to enhance the dry density and the Unconfined Compressive Strength (UCS). The four materials were assessed across four different levels, with moisture content also factored in as a parameter within a statistical analysis of 16 combinations. The Taguchi method predicted the combinations in which the Particle Size Distribution optimized the dry density and UCS as well as their dry density and UCS values. From the results, Moisture Content was the parameter with the highest influence on the optimization as well as the dry density and the UCS. It was observed that there was a direct relationship between the bulk density of the different granulometric fractions and their influence on the mix’s dry density. The fines were the material constituents that showed the highest influence on the mix UCS. When using the Taguchi method in RE building, the factor that should be maximized should is the mechanical strength. Full article
(This article belongs to the Special Issue Technical Advances in Recycled Construction Materials)
Show Figures

Figure 1

13 pages, 2934 KiB  
Article
Recovery and Restructuring of Fine and Coarse Soil Fractions as Earthen Construction Materials
by Mazhar Hussain, Ines Lamrous, Antony Provost, Nathalie Leblanc, Hafida Zmamou, Daniel Levacher and Abdoulaye Kane
Sustainability 2024, 16(20), 8952; https://doi.org/10.3390/su16208952 - 16 Oct 2024
Viewed by 1278
Abstract
Excessive consumption of natural resources to meet the growing demands of building and infrastructure projects has put enormous stress on these resources. On the other hand, a significant quantity of soil is excavated for development activities across the globe and is usually treated [...] Read more.
Excessive consumption of natural resources to meet the growing demands of building and infrastructure projects has put enormous stress on these resources. On the other hand, a significant quantity of soil is excavated for development activities across the globe and is usually treated as waste material. This study explores the potential of excavated soils in the Brittany region of France for its reuse as earthen construction materials. Characterization of soil recovered from building sites was carried out to classify the soils and observe their suitability for earthen construction materials. These characteristics include mainly Atterberg limits, granulometry, organic matter and optimum moisture content. Soil samples were separated into fine and coarse particles through wet sieving. The percentage of fines (particles smaller than 0.063 mm) in studied soil samples range from 28% to 65%. The methylene blue value (MBV) for Lorient, Bruz and Polama soils is 1, 1.2 and 1.2 g/100 g, and French classification (Guide de terrassements des remblais et des couches de forme; GTR) of soil samples is A1, B5 and A1, respectively. The washing of soils with lower fine content helps to recover excellent-quality sand and gravel, which are a useful and precious resource. However, residual fine particles are a waste material. In this study, three soil formulations were used for manufacturing earth blocks. These formulations include raw soil, fines and restructured soil. In restructured soil, a fine fraction of soil smaller than 0.063 mm was mixed with 15% recycled sand. Restructuring of soil fine particles helps to improve soil matrix composition and suitability for earth bricks. Compressed-earth blocks of 4 × 4 × 16 cm were manufactured at a laboratory scale for flexural strength testing by using optimum molding moisture content and compaction through Proctor normal energy. Compressive strength tests were performed on cubic blocks of size 4 × 4 × 4 cm. Mechanical testing of bricks showed that bricks with raw soil had higher resistance with a maximum of 3.4 MPa for Lorient soil. Removal of coarse particles from soil decreased the strength of bricks considerably. Restructuring of fines with recycled sand improves their granular skeleton and increases the compressive strength and durability of bricks. Full article
Show Figures

Figure 1

43 pages, 5663 KiB  
Review
Review on Sampling Methods and Health Impacts of Fine (PM2.5, ≤2.5 µm) and Ultrafine (UFP, PM0.1, ≤0.1 µm) Particles
by Balendra V. S. Chauhan, Karina Corada, Connor Young, Kirsty L. Smallbone and Kevin P. Wyche
Atmosphere 2024, 15(5), 572; https://doi.org/10.3390/atmos15050572 - 7 May 2024
Cited by 21 | Viewed by 6350
Abstract
Airborne particulate matter (PM) is of great concern in the modern-day atmosphere owing to its association with a variety of health impacts, such as respiratory and cardiovascular diseases. Of the various size fractions of PM, it is the finer fractions that are most [...] Read more.
Airborne particulate matter (PM) is of great concern in the modern-day atmosphere owing to its association with a variety of health impacts, such as respiratory and cardiovascular diseases. Of the various size fractions of PM, it is the finer fractions that are most harmful to health, in particular ultrafine particles (PM0.1; UFPs), with an aerodynamic diameter ≤ 100 nm. The smaller size fractions, of ≤2.5 µm (PM2.5; fine particles) and ≤0.1 µm (PM0.1; ultrafine particles), have been shown to have numerous linkages to negative health effects; however, their collection/sampling remains challenging. This review paper employed a comprehensive literature review methodology; 200 studies were evaluated based on the rigor of their methodologies, including the validity of experimental designs, data collection methods, and statistical analyses. Studies with robust methodologies were prioritised for inclusion. This review paper critically assesses the health risks associated with fine and ultrafine particles, highlighting vehicular emissions as the most significant source of particulate-related health effects. While coal combustion, diesel exhaust, household wood combustors’ emissions, and Earth’s crust dust also pose health risks, evidence suggests that exposure to particulates from vehicular emissions has the greatest impact on human health due to their widespread distribution and contribution to air pollution-related diseases. This article comprehensively examines current sampling technologies, specifically focusing on the collection and sampling of ultrafine particles (UFP) from ambient air to facilitate toxicological and physiochemical characterisation efforts. This article discusses diverse approaches to collect fine and ultrafine particulates, along with experimental endeavours to assess ultrafine particle concentrations across various microenvironments. Following meticulous evaluation of sampling techniques, high-volume air samplers such as the Chem Vol Model 2400 High Volume Cascade Impactor and low-volume samplers like the Personal Cascade Impactor Sampler (PCIS) emerge as effective methods. These techniques offer advantages in particle size fractionation, collection efficiency, and adaptability to different sampling environments, positioning them as valuable tools for precise characterisation of particulate matter in air quality research and environmental monitoring. Full article
(This article belongs to the Section Air Quality and Health)
Show Figures

Figure 1

21 pages, 6413 KiB  
Article
Acid-Free Processing of Phosphorite Ore Fines into Composite Fertilizers Using the Mechanochemical Activation Method
by Kamshat Bazhirova, Kurmanbek Zhantasov, Tynlybek Bazhirov, Alexandr Kolesnikov, Zarina Toltebaeva and Nurlybek Bazhirov
J. Compos. Sci. 2024, 8(5), 165; https://doi.org/10.3390/jcs8050165 - 29 Apr 2024
Cited by 3 | Viewed by 1725
Abstract
The relevance of involving substandard raw materials for the production of composite phosphorus-containing fertilizer production is significant due to the problem of providing food products for the growing population of the Earth. The main raw materials for phosphorus and composite phosphorus-containing fertilizer production [...] Read more.
The relevance of involving substandard raw materials for the production of composite phosphorus-containing fertilizer production is significant due to the problem of providing food products for the growing population of the Earth. The main raw materials for phosphorus and composite phosphorus-containing fertilizer production are natural phosphate ores—phosphorites. However, in the process of mining and crushing, ~55–60% phosphorite ore fines are formed—a fraction of less than 10 mm, which is unsuitable for traditional processing into composite phosphorus-containing fertilizers. This article presents the results of physicochemical studies of the substandard fine fraction of phosphorite ore and the results of the studies of the possibility of their direct processing into phosphorus and composition of phosphorus-containing fertilizers using methods of mechanical and mechanochemical activation in the “Activator 4” planetary mill. The findings of the studies performed confirm the rather high efficiency of phosphorite ore fines’ mechanical activation and phosphorite-containing mixtures’ mechanochemical activation, which make it possible to significantly increase the content of assimilable phosphorus pentoxide P2O5 in composite phosphorus-containing fertilizers. The proposed innovative technology has fundamental differences from existing technologies, since the mechanochemical activation of a mixture of phosphorite ore fines and functional components will allow for direct acid-free and waste-free processing into phosphorus and composite phosphorus-containing mineral fertilizers. Full article
(This article belongs to the Section Composites Manufacturing and Processing)
Show Figures

Figure 1

23 pages, 6179 KiB  
Article
Fabrication and Mechanical Evaluation of Eco-Friendly Geopolymeric Mortars Derived from Ignimbrite and Demolition Waste from the Construction Industry in Peru
by Fredy Alberto Huamán-Mamani, Cris Katherin Palomino-Ñaupa, María del Mar Orta Cuevas and Santiago Medina-Carrasco
Geosciences 2024, 14(3), 80; https://doi.org/10.3390/geosciences14030080 - 15 Mar 2024
Cited by 3 | Viewed by 2339
Abstract
Ignimbrite rock is a volcanic material located in the Arequipa region (Peru), and for centuries, it has been used as a construction material, giving a characteristic light pastel, white to pink color to the city of Arequipa, with white being the most common. [...] Read more.
Ignimbrite rock is a volcanic material located in the Arequipa region (Peru), and for centuries, it has been used as a construction material, giving a characteristic light pastel, white to pink color to the city of Arequipa, with white being the most common. In the present study, the potential use of three types of Arequipa raw materials (ignimbrite rock powder, calcined clay powder, and demolition mortar powder) as the main source of new binders or the manufacture of environmentally friendly mortars, without the addition of ordinary Portland cement (OPC) is discussed. In this work, an in-depth characterization of the materials used was carried out. The proposed fabrication route for geopolymeric materials was considered for the manufacture of binders and mortars using an alkaline solution of NaOH with values between 12 and 18 molar, as a trigger for the geopolymerization process. Geopolymeric mortars were obtained by adding a controlled amount of fine sand to the previously prepared mixture of binder raw material and an alkaline solution. Conventional OPC and geopolymeric mortars manufactured under the same conditions were mechanically evaluated by uniaxial compression tests at a constant compression rate of 0.05 mm/min and under normal conditions of temperature and atmosphere, where the most optimal values were obtained for 15 molar alkaline solutions of ignimbrite without the addition of aggregates, with values of compressive strength of 42 MPa and a modulus elastic of 30 GPa. The results revealed a significant increase in the maximum strength and modulus of elasticity values when the volumetric fractions of OPC are completely replaced with geopolymeric binders in the study conditions of this work, demonstrating the enormous potential of the ignimbrite rock and construction waste studied, as raw material of alternative mortar binders without the addition of OPC. With this work, the ignimbrite rock, of great value in the region and also found in other areas of the Earth’s geography, was characterized and valued, in addition to the calcined clay and demolition mortar of the region. Full article
(This article belongs to the Section Geomechanics)
Show Figures

Graphical abstract

28 pages, 21321 KiB  
Article
The Improved U-STFM: A Deep Learning-Based Nonlinear Spatial-Temporal Fusion Model for Land Surface Temperature Downscaling
by Shanxin Guo, Min Li, Yuanqing Li, Jinsong Chen, Hankui K. Zhang, Luyi Sun, Jingwen Wang, Ruxin Wang and Yan Yang
Remote Sens. 2024, 16(2), 322; https://doi.org/10.3390/rs16020322 - 12 Jan 2024
Cited by 9 | Viewed by 2531
Abstract
The thermal band of a satellite platform enables the measurement of land surface temperature (LST), which captures the spatial-temporal distribution of energy exchange between the Earth and the atmosphere. LST plays a critical role in simulation models, enhancing our understanding of physical and [...] Read more.
The thermal band of a satellite platform enables the measurement of land surface temperature (LST), which captures the spatial-temporal distribution of energy exchange between the Earth and the atmosphere. LST plays a critical role in simulation models, enhancing our understanding of physical and biochemical processes in nature. However, the limitations in swath width and orbit altitude prevent a single sensor from providing LST data with both high spatial and high temporal resolution. To tackle this challenge, the unmixing-based spatiotemporal fusion model (STFM) offers a promising solution by integrating data from multiple sensors. In these models, the surface reflectance is decomposed from coarse pixels to fine pixels using the linear unmixing function combined with fractional coverage. However, when downsizing LST through STFM, the linear mixing hypothesis fails to adequately represent the nonlinear energy mixing process of LST. Additionally, the original weighting function is sensitive to noise, leading to unreliable predictions of the final LST due to small errors in the unmixing function. To overcome these issues, we selected the U-STFM as the baseline model and introduced an updated version called the nonlinear U-STFM. This new model incorporates two deep learning components: the Dynamic Net (DyNet) and the Chang Ratio Net (RatioNet). The utilization of these components enables easy training with a small dataset while maintaining a high generalization capability over time. The MODIS Terra daytime LST products were employed to downscale from 1000 m to 30 m, in comparison with the Landsat7 LST products. Our results demonstrate that the new model surpasses STARFM, ESTARFM, and the original U-STFM in terms of prediction accuracy and anti-noise capability. To further enhance other STFMs, these two deep-learning components can replace the linear unmixing and weighting functions with minor modifications. As a deep learning-based model, it can be pretrained and deployed for online prediction. Full article
(This article belongs to the Special Issue Remote Sensing for Land Surface Temperature and Related Applications)
Show Figures

Figure 1

13 pages, 3097 KiB  
Article
Effect of Fine-Grained Particles and Sensitivity Analysis of Physical Indexes on Residual Strength of Granite Residual Soils
by Chen Fang, Ying Li, Chunsheng Gu and Baodong Xing
Coatings 2024, 14(1), 105; https://doi.org/10.3390/coatings14010105 - 12 Jan 2024
Cited by 2 | Viewed by 1306
Abstract
Recently, stability analyses of structures built of granite residual soils, for example, earth dams or other urban structures, particularly when under vibration, are being recognized as much more important than previously imagined. In such analyses, it is emphasized that the residual strength should [...] Read more.
Recently, stability analyses of structures built of granite residual soils, for example, earth dams or other urban structures, particularly when under vibration, are being recognized as much more important than previously imagined. In such analyses, it is emphasized that the residual strength should be utilized considering the seismic effect. Therefore, the residual strength of granite residual soils must be evaluated accurately in order to reduce the damage to structures built on them. This paper presented a laboratory study designed to examine the effect of fine-grained particles (FGPs; particle size ≤ 0.075 mm) on residual strength by the multistage procedure of the Bromhead ring shear test and evaluate the physical indexes forecasting the residual strength of granite residual soils using soil samples composed of fifteen different percentages of FGPs artificially adjusted from a reservoir embankment soil sample. The results showed that the residual strength decreased along with the increase in FGPs and that the residual frictional angle was rarely dependent on the ratio of FGPs when the ratio was over 90%. Even in the residual state, a small amplitude of fluctuation in shear stress still existed and was affected by the coarse-grained particles (CGPs; particle size ≥ 0.075 mm), such as the quartz particles in the granite residual soils. It was also found that the amplitude of fluctuation was smaller when the FGP fraction was greater. In addition, under the same normal stress, the peak strength and residual strength decreased with an increase in the ratio of FGPs. Then, they remained almost the same when the ratios of FGPs were equal to 85% and 90%, respectively, and the post-peak attenuation tended to increase initially with an increase in the FGPs and then remained almost the same. Moreover, based on the sensitivity analysis, the order of influence of physical indexes on the residual frictional angle was also ranked for the granite residual soils. Full article
Show Figures

Figure 1

26 pages, 12140 KiB  
Article
Age and Petrogenesis of the Dongjin Rare Metal Mineralized Intrusion in the Northern Margin of the North China Craton
by Chenyu Liu, Gongzheng Chen, Jinfang Wang, Yi Cheng, Kangshuo Li, Zeqian Lu and Yutong Song
Minerals 2023, 13(12), 1477; https://doi.org/10.3390/min13121477 - 24 Nov 2023
Cited by 1 | Viewed by 1970
Abstract
Highly fractionated granites are widespread in the middle part of the northern margin of the North China Craton (MNNCC), and several are accompanied by rare metal mineralization. The Dongjin rare metal mineralized intrusion, which is representative of this region, is composed of fine-grained [...] Read more.
Highly fractionated granites are widespread in the middle part of the northern margin of the North China Craton (MNNCC), and several are accompanied by rare metal mineralization. The Dongjin rare metal mineralized intrusion, which is representative of this region, is composed of fine-grained alkali-feldspar granite (FAG) and kali-feldspar granite (KG). The FAG and KG evolve continuously, exemplifying the relationship between magmatic evolution and rare metal mineralization. In this contribution, we present integrated columbite U-Pb geochronology, mineralogy, and whole-rock geochemistry analyses of the Dongjin intrusion to determine the timing of the mineralization, petrogenesis, and geodynamic setting, from which the following results are obtained: (1) LA-ICP-MS U-Pb dating for columbite of the FAG and KG yielded the lower intercept ages between 248.9 ± 1.9 Ma and 250.1 ± 1.1 Ma on the Tera–Wasserburg concordia diagram; (2) Geochemically, the Dongjin intrusion is characterized by an enrichment in Si, Al, Rb, Th, U, Nb, and Zr and a strong depletion in Ba, Sr, P, and Ti, with extremely negative Eu anomalies, high LREE and HREE values, and a noticeable tetrad effect of rare earth elements; as a result, it belongs to high-K calc-alkaline rocks; (3) The Dongjin intrusion belongs to a highly differentiated I-type or A-type granite; (4) The fractional crystallization of plagioclase, K-feldspar, and biotite occurred during magmatic evolution; (5) The Dongjin intrusion was formed in a post-collisional extensional environment. In conclusion, the FAG and KG have a homologous evolution, and the FAG has a higher degree of fractional crystallization. The enrichment and mineralization of Nb-Ta are related to the highly fractionated crystallization of granitic magma and fluid–melt interactions in the final stages of magmatic evolution, and there is a rare metal mineralization related to highly fractionated granite in the MNNCC in the Early Triassic, which deserves full attention in future research and prospecting. Full article
(This article belongs to the Special Issue Critical Metals on Land and in the Ocean)
Show Figures

Figure 1

7 pages, 2053 KiB  
Proceeding Paper
Effects of Atmospheric Aerosol Types on Ultraviolet Flux at Different Stations in the Indo-Gangetic Plain
by Ankita Mall and Sachchidanand Singh
Environ. Sci. Proc. 2023, 27(1), 33; https://doi.org/10.3390/ecas2023-15118 - 14 Oct 2023
Viewed by 645
Abstract
Atmospheric aerosols play a crucial role in the scattering and absorption of solar radiation, directly influencing the UV flux reaching the Earth’s surface. This study investigates the impact of different atmospheric aerosol types on the ultraviolet (UV) flux at four stations over the [...] Read more.
Atmospheric aerosols play a crucial role in the scattering and absorption of solar radiation, directly influencing the UV flux reaching the Earth’s surface. This study investigates the impact of different atmospheric aerosol types on the ultraviolet (UV) flux at four stations over the Indo-Gangetic plain (IGP). For this study, high-resolution 1° × 1° UVA and UVB data were obtained from Clouds and the Earth’s Radiant Energy System (CERES). Various aerosol types present in the atmosphere were categorized based upon their optical properties and their quantitative influence on UVA and UVB flux was examined. Ground-level aerosol products were obtained from the NASA-based Aerosol Robotic Network (AERONET) at four stations in the IGP. Based on the optical properties of aerosols (fine mode fraction, single scattering albedo, aerosol optical depth and angstrom exponent), four distinct atmospheric aerosol types were inferred, namely dust-dominant (DT), polluted-continental-dominant (PCD), black-carbon-dominant (BCD), and organic-carbon-dominant (OCD). It is observed that the AOD of different aerosol types when separated do not seem to have made significant effects on UVA/B radiation (except at Kanpur), possibly due to the statistically smaller data set. For the entire combined AOD, the effects on UVA/B became quite significant at all the stations, which shows that a unit rise in AOD leads to a reduction of 5–7 Wm−2 in UVA and 0.14–0.23 Wm−2 in UVB. Full article
(This article belongs to the Proceedings of The 6th International Electronic Conference on Atmospheric Sciences)
Show Figures

Figure 1

Back to TopTop