The Qinghai-Tibetan Plateau (QTP) and the Arctic are prime examples of permafrost distribution in high-altitude and high-latitude regions. A nuanced understanding of soil thermal conductivity (STC) and the various influencing factors is essential for improving the accuracy of permafrost simulation models in these areas. Nevertheless, no comparative analysis of STC between these two regions has been conducted. Therefore, this study aims to investigate the characteristics and influencing factors of STC at varying depths within the active layer (5 to 60 cm) during freezing and thawing periods in the QTP and the Arctic, using the regional-scale STC data products simulated through the XGBoost method. The findings indicate the following: (1) the mean STC of permafrost in the QTP is higher than that in the Arctic permafrost region. The STC in the QTP demonstrates a declining trend over time, while the Arctic permafrost maintains relative stability. The mean STC values in the QTP permafrost region during the thawing period are significantly higher than those during the freezing period. (2) STC of the QTP exhibits a fluctuating pattern at different depths, in contrast, the average STC value in the Arctic increases steadily with depth, with an increase rate of approximately 0.005 Wm-1 K-1/cm. (3) The analysis of influencing factors revealed that although moisture content, bulk density, and porosity are the primary drivers of regional variations in STC between the QTP and the Arctic permafrost, moisture elements in the QTP region have a greater influence on STC and the effect is stronger with increasing depth and during the freeze-thaw cycles. Conversely, soil saturation, bulk density, and porosity in the Arctic have significant impacts. This study constitutes the first systematic comparative analysis of STC characteristics.

The ongoing permafrost degradation in the Three-River Source Region (TRSR) poses serious threats to ecosystems, water resources, and infrastructure projects. As the China Water Tower and a vital barrier for the high-altitude ecological security of China, the TRSR is particularly vulnerable to such changes. The extent and severity of permafrost degradation are primarily governed by heat transfer dynamics, with soil thermal conductivity (STC) playing a crucial role in regulating thermal equilibrium. However, research on STC is hindered by insufficient in-situ measurements. To address this gap, we conducted in-situ measurements of STC at soil depths of 0-40 cm across 58 plots at 12 sites in the TRSR (244 records) during July and August 2023. The driving mechanisms influencing STC variations were further analyzed through laboratory experiments in September and October 2023. Spatially, STC increases from west to east and vertically with soil depth. Control experiments revealed that STC at negative temperatures is markedly higher than that at positive temperatures and increases with volumetric moisture content, particularly in inorganic soils, sand and loamy sand. This effect is more pronounced at subzero temperatures. Meanwhile, our results show that an artificial neural network model (R-2 = 0.78, p < 0.0001) incorporating ten measured soil physical parameters, outperforms traditional theoretical and empirical models in predicting STC. These findings contribute to a deeper understanding of permafrost formation, evolution, and its responses to climate change in the TRSR.

Waste tire textile fiber (WTTF), a secondary product from the processing of end-of-life tires, is predominantly disposed of through incineration or landfilling-both of which present significant environmental hazards. The incineration process emits large quantities of greenhouse gases (GHGs) as well as harmful substances such as dioxins and heavy metals, exacerbating air pollution and contributing to climate change. Conversely, landfilling WTTF results in long-term environmental degradation, as the synthetic fibers are non-biodegradable and can leach pollutants into the surrounding soil and water systems. These detrimental impacts emphasize the pressing need for environmentally sustainable disposal and reuse strategies. We found that 80% of WTTF was used for the production of thermal insulation mats. The other part, i.e., 20% of the raw material, used for the twining, stabilization, and improvement of the properties of the mats, consisted of recycled polyester fiber (RPES), bicomponent polyester fiber (BiPES), and hollow polyester fiber (HPES). The research shows that 80% of WTTF produces a stable filament for sustainable thermal insulating mat formation. The studies on sustainable thermal insulating mats show that the thermal conductivity of the product varies from 0.0412 W/(m center dot K) to 0.0338 W/(m center dot K). The tensile strength measured parallel to the direction of formation ranges from 5.60 kPa to 13.8 kPa, and, perpendicular to the direction of formation, it ranges from 7.0 kPa to 23 kPa. In addition, the fibers, as well as the finished product, were characterized by low water absorption values, which, depending on the composition, ranged from 1.5% to 4.3%. This research is practically significant because it demonstrates that WTTF can be used to produce insulating materials using non-woven technology. The obtained thermal conductivity values are comparable to those of conventional insulating materials, and the measured mechanical properties meet the requirements for insulating mats.

Soil thermal conductivity (STC) plays a crucial role in regulating the energy distribution of both the surface and underground soil layers. It is widely applied in various fields, including engineering design, geothermal resource development and climate change research. A rapid and accurate estimation of STC remains a key focus in the study of soil thermodynamic parameters. However, the methods for estimating STC and their distinct characteristics have yet to be systematically reviewed. In this study, we used bibliometrics to comprehensively and systematically review the literature on STC, focusing on knowledge graph characteristics to analyze the development trend of calculation schemes. The main conclusions drawn from the study are as follows: (1) In recent years, most studies have been focused on soil thermal characteristics and their main contributing factors, the soil hydrothermal process in the Qinghai-Tibet Plateau, geothermal equipment and numerical simulations, and the exploration of geothermal resources. (2) A systematic review of various schemes indicates that no single scheme is universally applicable to all soil types. Moreover, a single parameterization scheme fails to meet the practical requirements of land surface process models. We evaluated the advantages and disadvantages of the traditional heat conduction schemes, parameterization schemes, and machine learning-based schemes and the findings suggest that a comprehensive scheme that integrates these three different schemes for STC simulations should be urgently developed.

Thermal conductivity of frozen soil is a crucial property that influences heat transfer rate and freezing depth during the freezing process. However, accurately evaluating frozen soil's thermal conductivity is challenging due to its complex compositions and structures. To address this challenge, this study proposed the frozen soil quartet structure generation set (FSQSGS) to generate reasonable representative volume elements (RVEs) of frozen soil. The FSQSGS incorporates the ice phase and accounts for the freezing process, with clear physical meanings of input parameters. Then, the soil thermal conductivity of RVEs is calculated by the lattice Boltzmann method (LBM). This proposed calculation method is validated by experimental and analytical results of soil samples with various textures. The verification shows the broad applicability of the proposed model, especially for soils with fine grains or high saturation. Further, the influence of soil components and pore-scale geometry on the soil thermal conductivity is analyzed, with direct visualization of heat transfer. Results show that despite the soil skeleton geometry, i.e., the granular size and anisotropy, soil components have important effects on the soil thermal conductivity. Contents and thermal conductivity of soil particles are the main factors, while water and ice filling soil pores provide pathways for heat conduction, thereby improving thermal conductivity.

Particle morphology has well-known effects on the mechanical properties of granular materials as it influences particle contact and packing density. Although thermal conduction of sands also depended on such two behaviors, the effects of particle morphology on thermal conductivity are not fully understood. Several series of laboratory experiments were conducted to determine particle roundness, sphericity, and thermal conductivity of five river sands prepared with the same gradation and mineral composition but different porosities. A new predictive model was proposed within the framework of the classical Cote and Konrad's model that could capture the experimental data well. The results showed that the statistical distributions of roundness and sphericity follow the normal distribution pattern, and the expected value can be used as an evaluating index to depict the particle morphology of sand samples. Thermal conductivity of dry natural sands decreased with increasing porosity that exhibited a linear decreasing trend in a semi-logarithmic scale. The decreasing rate was found to depend on the overall morphology factor, defined as the average expected value of particle roundness and sphericity. For a given porosity, thermal conductivity increased with increasing overall morphology factor. Interestingly, thermal conductivity was less affected by the particle morphology with increasing porosity. The new model incorporating the particle morphology and mineral composition with satisfactory accuracy was far superior to the Cote and Konrad's model. Additional research is recommended to assess the effects of threedimensional particle morphology, applied stress, and particle stiffness on thermal conduction of natural sands.

Thermal backfill is an integrated part of underground electrical cable infrastructures systems, ground heat source pumps and radioactive waste repositories, as it minimizes resistance to heat transfer away from these systems. The heat transfer capacity and current carrying capability of underground electrical cables are significantly affected by thermal conductivity of backfill material and the surrounding soil media. Therefore, this research paper compares the thermal conductivity and shrinkage results of compacted (low to high densities) fly ash- and sand-bentonite mixtures with bentonite contents of 30%, 50%, 60%, 80% and 100%. The thermal conductivity of mixtures increased from 1.05 Wm-1K-1 to 1.20 Wm-1K-1 with the addition of fly ash content from 20 to 70% by weight in bentonite. The thermal conductivity bentonite-sand mixture was also found to be increased from 1.21 Wm-1K-1 to 1.83 Wm-1K-1 with increasing sand content. Additional to this, the bentonite-sand and bentonite-fly ash-based backfill materials surrounding heat-sensitive structures experience shrinkage and desiccation cracking due to thermal drying. Therefore, the desiccation volumetric shrinkage tests of bentonite-sand and bentonite-fly ash mixtures were conducted and found that the presence of sand or fly ash reduces shrinkage strain. Based on the experimental results, this study suggests a sustainable utilization of fly ash up to 50%-70% as an effective thermal backfill material in electrical cable infrastructure systems. Thus, the application of fly ash as a construction material reduces environmental impact and cost, aligning with the goals of sustainable development.

The growing demand for environmentally sustainable and biodegradable materials has intensified interest in alternative solutions for thermal insulation. This study explores the development of composite materials using mango seed shell biochar (MSSB) and soy protein isolate (SPI) as a biodegradable matrix-filler system. Mango seed shells, an abundant agro-industrial waste, were subjected to pyrolysis at 500 degrees C for 2 hours to produce biochar. The resulting MSSB was incorporated into SPI with glycerol as a plasticizer to fabricate composite sheets containing 10%, 20%, and 30% biochar by weight Thermal conductivity tests showed that increasing MSSB content led to a notable reduction in thermal conductivity, with the 30% MSSB composite achieving a value of 0.035 W/mK-comparable to commercial synthetic foams such as expanded polystyrene. Mechanical analysis revealed a tradeoff between tensile and compressive properties. While tensile strength decreased from 1.8 MPa for pure SPI to 0.7 MPa at 30% MSSB, compressive strength improved with increasing biochar content, peaking at 1.5 MPa.Biodegradability was evaluated through an 8-week soil burial test, which demonstrated accelerated degradation in composites with higher MSSB content, reaching up to 55% weight loss at 30% loading. These findings highlight the potential of MSSB-SPI composites as eco-friendly insulation materials suitable for green building and packaging applications. Future work will focus on mechanical property enhancement to expand the material's structural utility.

High-temperature thermal desorption is effective for remediating organic-contaminated sites, but its damage to soil functions and high energy consumption raise concerns. In this work, the variation of fertility indicators of two soils with thermal treatment temperature was investigated experimentally. To overcome the difficulties in measuring soil thermophysical properties under sealing and high-temperature conditions, two apparatus matching with the Hot Disk device were established and by which massive data were measured. The results show that, as temperature rises up to 500 degrees C, the combustion and decomposition of organic components and soil minerals gradually enhance, leading to a decrease in most fertility indicators, but an increase in grain size and pH. Available phosphorus and exchangeable potassium decrease with temperature rise first, but increase over 400 degrees C. Soil thermal conductivity and specific heat are positively correlated with temperature and water content. Water diffusion will intensify over 40 similar to 60 degrees C, leading to an intense increase in soil thermal conductivity. The results are expected to provide data basis and theoretical guidance for the comprehensive consideration of remediation effects, land reuse, and energy consumption in practical applications of thermal desorption remediation.

The earthen construction sector attracts worldwide attention, and earthen bricks are widely used. The conThe earthen construction sector attracts worldwide attention, and earthen bricks are widely used. The construction industry has also progressed in its use of natural green resources such as plant fibers to design building struction industry has also progressed in its use of natural green resources such as plant fibers to design building materials that are both economically and ecologically sustainable. However, the valorization of plant waste in materials that are both economically and ecologically sustainable. However, the valorization of plant waste in construction represents a crucial environmental challenge. The present study focuses on the development and construction represents a crucial environmental challenge. The present study focuses on the development and characterization of a new, low-cost earth-based building material stabilized with cement and corn straw fibers in characterization of a new, low-cost earth-based building material stabilized with cement and corn straw fibers in southeastern Morocco. Different earth bricks stabilized with different cement contents and corn straw fibers were southeastern Morocco. Different earth bricks stabilized with different cement contents and corn straw fibers were developed. The physico-chemical characterization of the soils used in the design of the bricks was carried out, developed. The physico-chemical characterization of the soils used in the design of the bricks was carried out, using physico-chemical, mineralogical and geotechnical characterization, including X-ray diffractometer (XRD) using physico-chemical, mineralogical and geotechnical characterization, including X-ray diffractometer (XRD) analysis, Fourier transform infrared (FTIR) spectra and energy dispersive X-ray (EDX) analysis. The first results analysis, Fourier transform infrared (FTIR) spectra and energy dispersive X-ray (EDX) analysis. The first results reveal that the predominant minerals in oasis soils include ferrous clinochlore, muscovite, calcite and quartz, reveal that the predominant minerals in oasis soils include ferrous clinochlore, muscovite, calcite and quartz, which are mainly composed of silt and sand. Then, the eligibility of these soils for compressed earth brick (CEB) which are mainly composed of silt and sand. Then, the eligibility of these soils for compressed earth brick (CEB) construction was assessed, adhering to established guidelines for the identification of suitable soil types. In construction was assessed, adhering to established guidelines for the identification of suitable soil types. In addition, the thermal properties of the bricks were determined, finding that the use of corn straw fibers improves addition, the thermal properties of the bricks were determined, finding that the use of corn straw fibers improves the thermal performance of the bricks, and cement stabilization leads to an improvement in the bricks' methe thermal performance of the bricks, and cement stabilization leads to an improvement in the bricks' mechanical properties. chanical properties.