Dust microparticles， as key components of atmospheric aerosols， have significant impacts on climate change and atmospheric environments. Based on continuous observations from November 2022 to January 2024， this study systematically analyzed the deposition characteristics of dust microparticles in snow and ice， glacial meltwater， as well as atmospheric precipitation and meltwater-fed Mingyong river water in the Mingyong Glacier， Meili Snow Mountain， southeastern Qinghai-Xizang Plateau. The results showed that： （1） The number concentration of microparticles in glacier meltwater runoff had pronounced seasonal variations， and the monsoon season was higher than in the non-monsoon season. （2） During the period of intense glacier melting （May—October）， the number concentration of microparticle in the Mingyong river water showed notable diurnal variations， nighttime concentrations were higher than daytime values. This phenomenon was mainly attributed to a decrease in the rate of glacier ablation at night， which slowed down meltwater runoff and thus prolonged the retention time of suspended particles in the river water. Through the continuous observation of meltwater runoff during day-night， it was found that the peak concentration of microparticles appeared around 20：00 CST， which further proved that there was a responsive relationship between the diurnal variation of microparticles in meltwater runoff and the strong ablation process of the glacier. （3） Fine particles （0.57~2 μm in diameter） dominated the number concentration of microparticles in water bodies. The volume-diameter distribution of microparticles in different water bodies generally exhibited a unimodal pattern， with small median particle sizes， indicating that dust microparticles in this glacier region predominantly originated from long-range atmospheric transport and deposition. This study revealed the deposition characteristics of dust microparticles in snow， ice and water bodies in the Meili Snow Mountain glacier area， providing significant insights for analyzing the mechanisms of the rapid ablation of the cryosphere and its response to regional climate change in the context of global warming.
The accelerated glacier melting under the intensification of global warming has significantly altered glacial erosion and weathering processes within the cryosphere， with unprecedented enhancement observed in recent decades. In warm glacier catchments， these enhanced processes may exert substantial impacts on the global carbon balance and climate change. Specifically， chemical weathering regulates the carbon cycle by consuming atmospheric CO₂， playing a crucial regulatory role in global climate change over geological timescales. However， with the accelerated melting of glaciers， the chemical weathering rate may change， and its specific impact on the carbon cycle requires further investigation. Mingyong Glacier catchment， located on the southeastern margin of the Qinghai-Xizang Plateau， was selected as the research area. A two-year monitoring campaign （from October 2018 to October 2020） of river water hydrological indicators and daily sampling was conducted， ultimately acquiring 731 river water samples. Multiple analytical approaches were employed， including mass balance calculations， Gibbs diagram analysis， mathematical statistics， and hydrochemical characterization. The hydrochemical characteristics of the river water in Mingyong Glacier catchment were investigated， and the chemical weathering rate of rocks and the carbon sink/source rate in the catchment were quantified. The results showed that river water exhibited significant seasonal variations in Mingyong Glacier catchment， with higher anion and cation concentrations in river water during the non-monsoon periods and lower values during the monsoon periods； the water hydrochemical type was classified as HCO₃-Ca. The anions and cations were predominantly derived from carbonate rock weathering， with participation of sulfuric acid in carbonate weathering contributing the largest proportion （62.1%） to chemical composition in river water. Other sources include carbonic acid in carbonate rock weathering （32.4%）， silicate weathering （4.5%）， and atmospheric deposition （1.0%）. Quantitatively， the silicate weathering rate and atmospheric CO₂ consumption flux averaged 0.16 t·km-2·a-1 and 0.31×103 mol·km-2·a-1， respectively. In contrast， sulfuric acid-driven carbonate weathering exhibited higher rates （3.34 t·km-2·a-1） and corresponding CO₂ release （4.00×103 mol·km-2·a-1）， yielding a net carbon source flux of 3.70×103 mol·km-2·a-1. This indicated that CO₂ release rates through chemical weathering in the study area exceeded its consumption rates by up to 13 times， exhibiting pronounced seasonal variability with monsoon periods showing significantly higher values than non-monsoon periods. Further analysis of the influencing factors for the above characteristic changes revealed that runoff was identified as the primary controlling factor affecting chemical weathering rates in the Mingyong Glacier catchment， with air temperature exerting greater impact than precipitation. The carbon fluxes in the Mingyong Glacier catchment were directly controlled by chemical weathering rates， while runoff and rainfall indirectly controlled these fluxes by modulating the weathering processes. In conclusion， chemical weathering in warm glacier catchments plays a pivotal role in regulating both local hydrochemical characteristics and ecosystems， as well as global carbon balance and climate change. Consequently， research in this field holds substantial scientific and social value， and deserves widespread attention. Future research should focus on the interaction mechanism between chemical weathering process and climate change to provide a scientific basis and decision-making support for addressing global climate change.
Supraglacial debris comprising rock fragments， soil， and gravel， accumulates on glacier surfaces primarily due to processes such as mountain collapses， glacial erosion， and the exposure of englacial debris. It influences sub-debris ablation patterns through energy exchange and albedo variations， resulting in distinctive mass balance responses， hydrological effects， and hazard processes in debris-covered glaciers compared to debris-free glaciers. The impact of debris on underlying glacier melt is predominantly determined by the unique thermal processes driven by variations in debris thickness. When debris thickness is below a threshold （approximately 2~3 cm）， the absorbed heat is efficiently transferred to the sub-debris ice， accelerating glacial melt and generating basal meltwater that facilitates glacier movement. In contrast， thicker debris layers impede heat transfer， reducing melt rates， and potentially leading to over- or underestimation of glacier runoff. The spatially heterogeneous distribution of debris thickness results in differential melting across the glacier surface， giving rise to ice cliffs and supraglacial lakes. Ice cliffs absorb more solar radiation， intensifying localized melt and posing risks of collapse， while expanding supraglacial lakes can lead to glacial lake outburst floods （GLOFs）， threatening downstream populations and ecosystems. The thickness of supraglacial debris is thus a key factor in simulating glacier melt and accurately quantifying glacier runoff. It provides essential data support for research on dynamics， mass balance， and hydrological modeling of debris-covered glaciers， contributing to enhanced disaster risk management and water resource planning in downstream areas. The Langtang basin， located in the central Himalayas， is characterized by extensive supraglacial debris cover. Its unique geographical setting and glacial features make it a critical area for studying Himalayan glaciers and their responses to climate change. However， current research on supraglacial debris in this region remains predominantly focused on field measurements， with limited investigations into debris thickness and its spatial distribution at the watershed scale. It significantly impedes a comprehensive understanding of glaciers with debris coverage within this area. In response to the above questions， using Landsat 8 remote sensing imagery and high temporal resolution meteorological station data， this study calculated surface temperature， sensible heat flux， and net radiation flux in the Langtang region to solve the energy balance equation. Based on this approach， the spatial distribution of supraglacial debris thickness across glaciers in the Langtang region was retrieved. The study further analyzed the spatial distribution characteristics of debris thickness in representative glaciers and investigated the factors contributing to the heterogeneity in supraglacial debris thickness distribution. The study yielded the following findings： （1） The average thickness of supraglacial debris in the Langtang Basin glaciers was （0.25±0.02） m. Specifically， Lirung glacier had a thickness of （0.55±0.02） m， Shalbachum glacier （0.48±0.02） m， Langshisha glacier （0.31±0.02） m， and Langtang glacier （0.25±0.02） m. （2） Along the longitudinal profiles， the supraglacial debris thickness increased from the upper to the lower parts of the ablation zones. For Lirung， Shalbachum， and Langtang glaciers， the debris accumulation rates first decreased and then increased along the longitudinal profiles， whereas Langshisha glacier showed a continuous decrease. In terms of the transverse profiles， the thickness of the supraglacial debris was greater on the right side of the glacier movement direction for Lirung， Shalbachum， and Langtang glaciers， while Langshisha glacier exhibited thicker debris on both sides and thinner debris in the middle. （3） The variation in debris accumulation rates along the longitudinal profiles was primarily attributed to differences in surface flow velocities in the lower ablation zones. （4） The uneven distribution of debris thickness along the transverse profiles near the glacier termini was mainly due to differences in surface flow velocities， melt rates， and topographic features.
Glaciers are widely distributed in polar regions and mid-to-high-latitude mountains. Formed by accumulated snowfall， they retain critical records of glacial formation and evolution. Drilling ice cores in polar ice sheets or mountain glaciers is essential for obtaining paleoclimate data， understanding glacier dynamics， and predicting global environmental changes. In scientific research， the amount of ice core samples is often insufficient to satisfy research requirements. Therefore， large-diameter ice cores or more replicate ice cores need to be drilled. While large-diameter ice core drilling faces depth limitations and impracticality for broad application， the directional ice core drilling technology can drill branch holes within the parent hole to obtain replicate ice cores at a minimum cost. Currently， there are three primary directional ice core drilling technologies， namely the directional ice core drilling technology using whipstock， the directional ice core drilling technology based on natural deviation-correction of the drill， and the directional ice core drilling technology with power push. Directional ice core drilling technology using whipstock can be divided into two approaches based on drill type： “whipstock + thermal coring drill” and “whipstock + electromechanical drill”. The former typically uses two different types of whipstocks， which are fixed whipstock and retrievable whipstock. This study systematically reviews the working principles， drilling processes， and applications of these technologies， while clarifying their advantages and disadvantages through comparison and analysis. In general， the directional ice core drilling technology with “fixed whipstock + thermal coring drill”， developed in the early 1970s， remains prevalent for bypassing the stuck drill. The technology is characterized by simple operation and low cost. Additionally， the directional core drilling technology with “retrievable whipstock + thermal coring drill” has been developed. However， the technology has only been tested in the laboratory and cannot achieve the orientation of branch holes in any direction. Since the early 21st century， Russia has developed the directional ice core drilling technology based on natural deviation-correction of the drill， which can only drill branch holes at the low side of the borehole. Therefore， the technology prohibits the re-entry of the drill into the parent hole. Since the 2010s， the U.S. has pioneered the development of the directional ice core drilling technology with power push， which has the highest cost and the most complex drilling process. This technology can drill branch hole at the high side of the borehole. At present， the directional ice core drilling technology based on natural deviation-correction of the drill and the directional ice core drilling technology with power push are relatively mature. In recent years， the U.S. has proposed the directional ice core drilling technology with “retrievable whipstock + electromechanical drill”， which is more universal and economical. However， the technology is only in the stage of conceptual design and has never been tested. In general， Russia and the U.S. lead directional ice core drilling development， while China lags behind technically in this field. In addition， compared with the directional rock core drilling technology in the fields of geology and petroleum drilling， the directional ice core drilling technology remains less mature. In the future， in order to improve the development of directional ice core drilling technologies， priority should be given to developing the directional ice core drilling technology with “retrievable whipstock + electromechanical drill”. Meanwhile， efforts should focus on enhancing retrievable whipstocks and developing compatible supporting technologies for thermal coring drills， while optimizing the small-diameter directional coring drill with power push.
Typical alpine landscape elements such as glaciers， cold deserts， alpine meadows， and alpine steppes constitute a unique alpine mountain landscape system in the inland river basins of northwest China. Their spatiotemporal variations and distribution characteristics directly affect runoff generation， confluence process， and water balance in the upper reaches of inland rivers. To investigate the landscape distribution characteristics in the alpine mountainous areas of inland river basins， this study selected the upper reaches of the Shule River， one of China’s three major inland rivers， as the study area. It classified alpine landscape types in detail and analyzed their spatiotemporal variations and influencing factors using landscape dynamic degree， transfer matrix， landscape pattern index， and PLUS model. The results showed that： （1） alpine steppe and cold desert were the dominant landscape types in the study area （>85% area coverage）. From the 1990s to the 2020s， the areas of alpine steppe and bare land showed significant increasing trends， while the areas of cold desert， glacier， and shrubland decreased markedly. Alpine meadow and swamp meadow changed minimally （relative change rates of 0.09% and -0.03%， respectively）. It was expected that grassland areas would continue to expand， while cold desert and glacier areas would further shrink by the 2030s. （2） The increase in alpine steppe area was mainly due to conversion from cold desert， indicating a positive trend in vegetation development in the study area. （3） The landscape pattern became more fragmented， and overall landscape heterogeneity and unevenness increased. （4） Temperature and precipitation were identified as the main influencing factors of alpine landscape change in the study area. This study improves the understanding of alpine landscape patterns and their dynamic changes in the context of climate warming and humidification， providing a reference for ecological and hydrological studies in inland river basins of alpine mountainous areas.
Lakes on the Qinghai-Xizang Plateau play a critical role in regional and global water-heat cycles within the climate system. However， significant knowledge gaps remain in understanding their heat storage dynamics due to the scarcity of long-term water-heat monitoring data. Focusing on Qinghai Lake， China’s largest saline lake， this study developed an integrated framework combining MODIS remote sensing and process-based modeling to quantify heat storage variations from 2000 to 2023. This study first reconstructed continuous lake surface temperature （LST） time series by employing the Random Forest algorithm to fill cloud-induced gaps in MODIS data， achieving high accuracy （RMSE： 1.7~1.9 ℃； R²： 0.95~0.96）. The gap-filled LST， combined with ERA5 meteorological forcing and lake bathymetry， was used to drive the FLake model at 12-hour time steps to simulate the lake’s vertical thermal structure. Heat storage was estimated using both FLake-simulated temperature profiles and ERA5 energy balance components. The results revealed pronounced seasonality in LST （summer peaks： 18~20 ℃； winter minima： <0 ℃） and strong thermal stratification from June to October， contrasting with well-mixed conditions observed in May and November-December. Notably， Qinghai Lake consistently functioned as a heat sink during 2000—2023， exhibiting a statistically insignificant increasing trend in heat storage （0.9 W·m-²/decade， P>0.05） that fluctuated within a range of -5 to 5 W·m-². This thermal accumulation was primarily driven by regional climate warming （0.37 ℃/decade in air temperature， r=0.58）， decreasing wind speeds （-0.08 m·s-¹/decade， r=-0.27）， and shortening ice duration （-7.3 days/decade， r=-0.51）. The study demonstrates significant scientific contributions. First， it validates Random Forest as a robust method for reconstructing LST in cloud-prone， high-altitude lakes. Second， the FLake model， while exhibiting a systematic cold bias （RMSE： 2.8 ℃ at 0.5 m depth）， effectively reproduces key thermal characteristics， including depth-dependent warming trends （0.19 ℃/decade at the surface vs. -0.01 ℃/decade at 15 m）. Third， this study provides 24 years quantification of heat storage for a mega-lake in Qinghai-Xizang Plateau， highlighting its role as a regional heat capacitor under climate change. The integrated satellite-model framework provides a transferable methodology applicable to data-scarce regions， generating critical understanding of lake-atmosphere interactions and supporting improved parameterization in climate models for the “Asian Water Tower” region. These findings inform water resource management strategies in climate-sensitive ecosystems where lakes serve as key indicators of environmental change.
Under the influence of warming and humidification on the Tibetan Plateau， frozen soil has been undergoing rapid degradation， thereby triggering a large number of frozen soil landslides. To thoroughly investigate the instability mechanism of landslides in frozen soil regions， direct shear tests on silt and clay from a landslide instability region on the active layer （thawed soil） of frozen soil were performed， along with tests on the soil-ice interface. By utilizing the discrete element analysis software MatDEM， a modified model corresponding to the direct shear test was established. Then， the results of numerical simulations and direct shear tests were compared and analyzed. The results showed that the modified model could effectively simulate both silt and clay. The shear characteristic curves and shear strength fitting curves obtained from the simulation and test results exhibited generally consistent trends. Notably， the shear strength of clay was significantly lower than that of silt， indicating that shear strength decreased with reduced particle size. At the soil-ice interface， clay-ice exhibited the lowest shear strength， demonstrating the weakest stability. The displacement field diagrams and element connecting state diagrams in the simulation results showed that a distinct shear band formed during the shear process. Moreover， the variation patterns of average coordination number of particles on the interface and non-interface of thawed soil demonstrated that the particles in the shear band played a dominant role in the deformation of the samples. In addition， the heat variation curves showed that the heat generated during the shear process primarily originated from the frictional heat produced by the upper and lower shear boxes in the shear band. This study can provide an effective reference model for numerical simulations on shear strength of soils from landslides in frozen soil regions on the Tibetan Plateau.
Frozen soil is widely distributed in China， including the eastern monsoon region， the arid northwestern regions， and the Qinghai-Xizang Plateau， while permafrost is mainly distributed on the Qinghai-Xizang Plateau. In recent years， the implementation of national strategies such as the “Belt and Road Initiative” and “Western Development Strategy” has accelerated the construction of infrastructure， including railways across the Qinghai-Xizang Plateau. Considering the sensitivity and vulnerability of permafrost， the “bridge-for-embankment” approach has been widely implemented in railway construction to ensure the quality of the project and minimize thermal disturbance to the surrounding permafrost. Pile-supported bridges are widely used in railway construction in permafrost regions due to the advantage of minimal thermal impact on the permafrost. However， in permafrost regions， the thickness of the permafrost layer and the seasonal active layer are greatly affected by local temperature variations. Seasonal variations and global warming change the thermal and mechanical properties of foundation soils， consequently affecting the vertical bearing characteristics of pile foundations in permafrost regions. These changes introduce substantial uncertainties in the bearing capacity of pile foundations， which directly affect the long-term stability and safety of bridges. To quantitatively analyze the effect of permafrost layer on the vertical bearing characteristics of existing railway bridge pile foundations， this study took the high-cap pile foundations widely used in Qinghai-Xizang Plateau as the research objects， and investigated the load-bearing performance of pile foundations under non-frozen soil conditions （control group） and permafrost conditions （with a 140 cm thickness）. Additionally， small-scale indoor model tests were conducted to examine the failure characteristics of soil around the piles. The results showed that under the condition of non-frozen soil， a nearly rectangular closed crack formed on the soil surface around the pile， radiating from its four corners. Significant surface displacement occurred within a range of 0.5 times the diameter of the pile， accompanied by a single primary crack on the soil surface. In contrast， under permafrost conditions， no noticeable surface displacement was observed， although an open rectangular crack occasionally appeared around the pile. In addition， the presence of permafrost significantly improved the vertical ultimate bearing capacity of pile foundations. The maximum bearing capacity under non-frozen soil conditions was approximately 40 kN， while it reached approximately 178 kN under permafrost conditions， representing a 4.5-fold increase. This increase in bearing capacity of pile foundations primarily resulted from a substantial rise in pile side friction resistance within the permafrost soil layer. The maximum side friction resistance under non-frozen soil conditions was 106.39 kPa， and increased to 752.20 kPa under permafrost conditions， demonstrating a sevenfold enhancement. In contrast， the influence of permafrost on the end bearing capacity of pile foundations was relatively minor. The maximum end bearing capacity of pile foundations was 12.5 kN under non-frozen soil conditions and 13.6 kN under permafrost conditions， representing an 8.8% increase. Overall， the presence of permafrost layer significantly changes the vertical bearing characteristics of pile foundations， including the failure characteristics of soil around pile， the bearing capacity of pile foundations and the exertion of side friction resistance. Therefore， it is essential to fully consider the effects of permafrost when evaluating the bearing performance of pile foundations for railway bridges in permafrost regions.
Microencapsulated phase change materials （MPCM） exhibit excellent temperature regulation capabilities. Their integration into grouting materials for surrounding rock reinforcement can effectively alleviate freezing damage of tunnels. Due to periodic and drastic environmental temperature fluctuations， tunnels in cold regions are prone to freeze-thaw damage including water leakage， ice formation， and cracking during operation. The freezing of groundwater is a prerequisite for these damages to occur. The use of grouting materials to reinforce the surrounding rock layers has been proven to effectively reduce groundwater infiltration and mitigate freeze-thaw damage in tunnel projects. However， conventional cement-based grouting materials demonstrate limited durability under freeze-thaw conditions， highlighting the need for the development of new grouting materials to control surrounding rock heave in tunnels. Phase change materials （PCM）， with their thermal energy storage and temperature regulation capabilities， have attracted considerable attention. MPCMs demonstrate excellent dispersibility and compatibility in cement-based materials， offering a novel approach to enhancing the freeze-thaw resistance of grouting materials. However， incorporating MPCM significantly deteriorates the workability and mechanical properties of cement-based materials. Therefore， it is essential to optimize the MPCM dosage to prevent adverse effects on material performance， offering valuable insights for freeze-thaw damage prevention in cold-region tunnels. Current research on MPCM predominantly focuses on concrete structures， whereas grouting materials require specific performance characteristics， including fluidity， bleeding rate， setting time， and gelation rate. To address these issues， a four-factor， four-level orthogonal experiment was conducted to systematically investigate the effects of water-to-binder ratio， MPCM dosage， silica fume dosage， and accelerator content on the fluidity， bleeding rate， setting time， compressive strength， flexural strength， and freeze-thaw resistance of composite cement-based grouting materials. Range analysis was used to assess the effect of each factor on material performance， and a multiple linear regression model was established to determine the optimal mix ratio for achieving superior workability and mechanical properties. This research could establish an experimental basis for the preparation and application of MPCM-based cementitious grouting materials with dual functionality in thermal insulation and load-bearing capacity. The experimental results showed that： （1） as the water-to-binder ratio increased from 0.6 to 0.9， the fluidity of the grouting material improved by 87.25%. When the silica fume content was 15%， the bleeding rate decreased by 91.07%， significantly improving the slurry stability. With 1.5% accelerator content， the initial and final setting times were shortened by 22.35% and 27.55%， respectively. The incorporation of MPCM negatively affected the workability of the material. A 15% MPCM dosage resulted in a 30.86% decrease in fluidity， a 57.25% increase in bleeding， and a 24% extension in setting time， collectively compromising the material’s injectability. （2） Prior to freeze-thaw cycling， increasing the water-to-binder ratio and MPCM content significantly reduced the compressive and flexural strengths， with maximum reductions of 34.10% and 41.67%， respectively. The compressive and flexural strengths peaked with 10% silica fume content， showing increases of 27.81% and 41.87%， respectively， compared to the non-silica fume group. The accelerator contributed to strength enhancement only at the 7-day curing period. After 100 freeze-thaw cycles， the optimal freeze-thaw resistance was observed in the group with 10% MPCM content， with a compressive strength to 28-day strength ratio reaching 0.93—representing an increase of 86.02% compared to the non-MPCM group. （3） MPCM particles formed strong interfacial bonds with the surrounding binder materials， promoting the formation of dense hydration products. However， numerous small-sized MPCM particles tended to aggregate， increasing porosity. The thermal regulation capability of MPCM helped preserve the structural integrity of the hydration gel under freeze-thaw cycles， thereby enhancing the freeze-thaw resistance. （4） The optimal comprehensive performance of the grouting material was achieved with a water-to-binder ratio of 0.7， 10% silica fume， and 1.5% accelerator content. The inclusion of MPCM in the range of 0%~15% ensured compliance with required standards for material performance. These findings provide scientific evidence and practical guidance for the prevention of freeze-thaw damage in cold-region tunnels.
The stability of permafrost subgrades is closely related to the surrounding hydrothermal environment. Under the influence of climate warming and humidification on the Qinghai-Xizang Plateau， the extensive scale and segmented design of permafrost subgrades in expressways lead to significant ponding issues. Based on long-term field investigations， unmanned aerial vehicle image modelling， and ground-penetrating radar surveys of Gonghe-Yushu Expressway （GYE）， combined with ground temperature and moisture monitoring in typical ponding sections， this study analyzed the spatial distribution of permafrost subgrade distress and their relationship with roadside ponding in the 340-km section from Elashan to Qingshuihe of the GYE. Additionally， it revealed how roadside ponding affected the development of large-scale permafrost subgrade distress. The results showed that subgrade distress in the permafrost sections of the GYE were primarily classified into three types： uneven settlement （77.3%）， transition settlement （13.5%）， and cracks （8.6%）. In the 340-km study section， more than 60% of the sections showed signs of subgrade distress， which were mainly distributed in the high plains and intermountain basins from Changshitoushan to Duoqinankelang and from Yeniugou to Qingshuihe. The distress rate reached up to 60% in permafrost regions with high temperatures and high ice content. The distress rate of the entire study section was 8.4%， while the distress rate in the permafrost section was significantly higher， reaching 18.05%. A strong correlation was observed between roadside ponding and the development of subgrade distress. Approximately 31% of the permafrost sections exhibited roadside ponding， which was mainly distributed in flat terrain. About 66.1% of subgrade distress was associated with roadside ponding. The severity of these distress increased with larger ponding area， greater ponding depth， and shorter distance to the subgrade slope foot. In the ponding sections， moisture content and temperature at the subgrade foot were significantly higher than those in the non-ponding sections， and the permafrost table beneath the subgrade was notably lower than that in the non-ponding sections. Roadside ponding served as a long-term heat source， continuously transferring heat to the permafrost layer beneath the subgrade. During the warm season， ponding absorbed external heat and stored it internally， while simultaneously transferring heat to the permafrost layer. In the early-to-mid cold season， the ponding surface froze， forming an ice layer that acted as a barrier to heat exchange with the external environment. However， due to the high salt content of ponding water， the freezing point was lowered， enabling continued heat transfer from the bottom of the ponding to the permafrost layer. This resulted in a shorter cold season for the soil beneath the ponding area， reducing the amount of cold absorbed by the soil. As a result， the ground temperature in the ponding area increased significantly， leading to asymmetric temperature distribution in the permafrost subgrade area. This process， coupled with increased moisture content， ultimately led to partial thawing of the permafrost layer beneath the subgrade， disrupting the subgrade and inducing various types of subgrade distress. The findings of this study provide valuable insights into the relationship between roadside ponding and subgrade distress in permafrost regions. The results provide a scientific basis for formulating preventive measures and maintenance strategies to mitigate ponding-induced distress in permafrost subgrades. Additionally， the study contributes to a deeper understanding of hydrothermal dynamics affecting subgrade stability and offers practical guidance for future construction and maintenance of subgrades in water-rich permafrost areas. Furthermore， the study highlights the critical role of roadside ponding in the management of permafrost subgrades.
The interaction between frozen soil and structures is a critical and widespread concern in various engineering applications， including pile foundations， channels， oil and gas pipelines， and supporting structures. Investigating the mechanical properties of frozen soil and the interface between soil and structures is fundamental for effectively addressing this interaction. Consequently， understanding the shear failure characteristics， ultimate bearing capacity， and service life of the frozen soil-structure interface is of great significance for engineering design， construction， and operation. Previous studies have explored the strength characteristics of the frozen soil-structure interface by using methods such as direct shear tests， dynamic devices， and particle image velocimetry （PIV） technology. However， these studies often simplify the three-dimensional stress state of soil and structures into a two-dimensional framework， mainly focusing on direct shear tests under constant normal stress. In practical engineering scenarios， the normal stress at the interface is not constant under three-dimensional stress conditions. Therefore， it is crucial to investigate the shear characteristics of the frozen soil-structure interface under three-dimensional stress and conduct in-depth research on its strength. In this study， the effects of confining pressure， water content， and roughness on the mechanical properties of the frozen soil-steel interface were investigated using prefabricated frozen soil-steel triaxial test specimens at -5 ℃. An orthogonal experimental design was utilized to analyze the effect of confining pressure， temperature， roughness， and water content on the shear strength of the interface. A damage mechanics model was developed to characterize the frozen soil-steel interface， incorporating the effects of confining pressure， roughness， and water content. The model parameters were validated through experimental data. The results showed that the axial stress-strain curve of the frozen soil-steel interface exhibited typical strain-softening behavior under different confining pressures. Under constant water content and roughness， the peak stress increased with higher confining pressure. This could be attributed to closer contact between the frozen soil and steel， reduced internal soil porosity， and strengthened interparticle bonding， all of which collectively enhanced the interfacial shear strength. The interface peak stress initially increased and then decreased with increasing water content， reaching its maximum at the optimal water content of 16.6%. At a lower water content （11%）， the interfacial cemented ice content was minimal， resulting in weak ice cementation. In this case， the interfacial strength was primarily controlled by the cementation and friction of ice within the frozen soil. After reaching the peak stress， the stress decreased gradually. Furthermore， the interface peak stress initially increased and then decreased with increasing roughness. When the steel surface was smooth， the interfacial shear strength was predominantly determined by ice cementation. As roughness increased， deeper grooves on the steel surface allowed more soil to embed within them. At this stage， the interfacial shear strength was not only influenced by ice cementation but also by the interlocking action between soil particles and the grooves， significantly increasing the peak stress. However， as roughness continued to increase， the interfacial shear strength began to decline， although it remained higher than that of a smooth interface. This reduction might be attributed to the “damage” of the soil particle structure near the interface caused by the increased roughness under load， leading to a decrease in strength. Orthogonal experiment revealed that the factors influencing the shear strength of the frozen soil-steel interface were water content， temperature， roughness， and confining pressure in descending order of significance. A mechanical damage model for the frozen soil-steel interface was proposed， considering the effects of confining pressure， roughness， and water content. This model effectively described the shear stress-displacement relationship before peak strength. As the structural roughness， soil moisture content， and confining pressure increased， the failure mode of the frozen soil-steel interface shifted from brittle to plastic. The research findings provide valuable references for determining ultimate bearing capacity of frozen soil-structure interfaces.
Glazed hollow bead thermal insulation concrete （GHBC） exhibits excellent thermal insulation and frost resistance performance. To explore the characteristics of long-term mechanical performance degradation of GHBC as a self-insulating material after freeze-thaw damage， comprehensive analyses were conducted after 0 to 60 freeze-thaw cycles， including surface morphology observations， uniaxial compression tests， splitting tensile tests， graded compression creep tests， and scanning electron microscopic （SEM） analyses. The results indicated that with increasing freeze-thaw cycles， surface spalling and pitting corrosion of the concrete intensified， apparent porosity increased， and pore size expanded. After 0， 20， 40， and 60 freeze-thaw cycles， the total apparent porosity of GHBC was 8.32%， 12.83%， 14.28%， and 15.21%， respectively， while that of normal concrete （NC） was 9.05%， 11.62%， 13.39%， and 20.78%， respectively. After 60 cycles， the compressive strength and tensile strength of NC decreased by 22.87% and 23.53%， respectively， while those of GHBC decreased by 20.69% and 21.67%， demonstrating the beneficial effect of glazed hollow beads in enhancing concrete’s resistance to freeze-thaw damage. GHBC creep test results indicated that with increasing freeze-thaw cycles and stress levels， creep strain and rate continuously increased， leading to continuous performance degradation until failure at critical stress. After 60 freeze-thaw cycles， creep strength decreased by 20.19%， and total creep duration was reduced by 0.33 hours. The test data were well fitted by the Burgers model. Comparison of microscopic morphology between the two types of concrete revealed that after freeze-thaw cycles， internal damage worsened， porosity increased， and microcracks gradually connected， cement matrix structure loosened， ultimately resulting in the loss of load-bearing capacity. The unique closed-cell honeycomb structure of glazed hollow beads effectively released frost heave forces during the initial stage of freeze-thaw damage， providing an internal curing effect and maintaining macroscopic stability. However， with increasing numbers of freeze-thaw cycles， this closed-cell structure failed， and the interfacial bonding strength between the cement matrix and glazed hollow beads decreased， leading to a sharp decline in the mechanical strength. This study provides valuable references for the application of GHBC in cold-region engineering projects.
Ambient temperature fluctuations in cold regions significantly affect the physical and mechanical properties of subgrade soils. Additionally， the hydrothermal behavior of subgrades is significantly influenced by freeze-thaw cycles. Infrastructure construction in cold regions inevitably introduces significant thermal disturbances to subgrades， leading to accelerated degradation. Moreover， frost heave caused by the volumetric expansion of water during freezing leads to pavement cracking， severely compromising traffic safety. Sisal fiber， a natural material， offers advantages such as low density， high tensile strength， renewability， and excellent resistance to alkali. These advantages enable its widespread application in soil reinforcement， cement-based material enhancement， and related fields. Within the matrix， sisal fiber forms a three-dimensional network structure that disperses stress， suppresses crack propagation， and maintains structural integrity during freeze-thaw cycles， thereby enhancing freeze-thaw resistance. However， the reinforcement effect of fiber modification alone on the mechanical properties of soil is limited. Subgrade stability is frequently compromised under the combined effects of traffic-induced cyclic loading and freeze-thaw cycles. Alkali-activated materials， used as chemical stabilizers， have attracted considerable attention due to their outstanding engineering performance and potential to reduce environmental pollution during construction. Geopolymerization in soils refers to a series of chemical reactions between alkaline activators and aluminosilicate materials. By rationally designing the mix proportions of raw materials and alkaline activators， the engineering performance of geopolymers can be significantly improved in terms of energy efficiency， strength， and corrosion resistance. Among various raw materials， geopolymer-stabilized soil using metakaolin as a precursor exhibits superior mechanical properties compared to soils stabilized with cement or lime. Although considerable research has focused on soil improvement materials， the combined application of natural fibers and geopolymers has received relatively limited attention. Therefore， reinforcing soil with green， low-carbon materials is of great significance， necessitating evaluations of mechanical properties and hydrothermal deformation behavior. In this study， experimental models were constructed for a silty clay subgrade and a geopolymer-sisal fiber synergistically stabilized soil subgrade. The initial water content of the subgrade fill materials was uniformly set at 16%， and the sisal fiber content in the geopolymer-sisal fiber synergistically stabilized subgrade was fixed at 0.3%. The subgrade models were cured for 28 days at an ambient temperature of 25 °C to ensure internal temperature stability and complete hydration. Subsequently， four freeze-thaw cycles were conducted， each lasting 192 hours. The effectiveness of the stabilized subgrade in mitigating frost heave was evaluated by monitoring changes in soil temperature， heat flux， volumetric unfrozen water content， and displacement throughout the freeze-thaw cycles. The experimental results showed that low-temperature regions gradually expanded downward from the surface， while high-temperature regions contracted during freeze-thaw cycles. Rapid thermal exchange occurred near the subgrade surface， where ambient temperature fluctuations exerted a more pronounced impact. As soil temperature propagated downward， its variation amplitude decreased with increasing depth and gradually lagged behind the ambient temperature. The pattern of heat flux variation at different subgrade depths corresponded to that of temperature change， with the most significant changes observed during the first freeze-thaw cycle. Due to the lag in soil temperature response， heat flux variations in the subgrade model were delayed， which was attributed to the hysteresis of the water-ice phase transition. Furthermore， under significant soil temperature fluctuations， the geopolymer-sisal fiber synergistically stabilized subgrade exhibited greater stability in residual volumetric unfrozen water content compared to the silty clay subgrade. Changes in volumetric unfrozen water content exhibited a stronger correlation with soil temperature variations than with the number of freeze-thaw cycles. Additionally， the displacement variation in the geopolymer-sisal fiber synergistically stabilized subgrade was smaller than the net deformation observed in the silty clay subgrade. The net displacement of both subgrades gradually decreased， while cumulative displacement increased until dynamic stabilization was achieved. After four freeze-thaw cycles， the cumulative displacements of the geopolymer-sisal fiber synergistically stabilized subgrade and the silty clay subgrade were 0.53 mm and 1.32 mm， respectively.
Four machine learning （ML） algorithms， namely Decision Trees （DT）， Multilayer Perception （MLP）， Support Vector Machines （SVM）， and Gaussian Processes （GP） were employed to investigate the performance and application of machine learning （ML） methods in predicting mechanical parameters of frozen soil. Based on a dataset comprising 116 sets of directional shear test data for frozen clay， prediction models were established using the coefficient of principal stress ratio b， principal stress direction angle α， mean principal stress p， and temperature T as inputs， and the mechanical parameters of frozen clay （Stress-Strain Curve （SSC） pattern and failure strength qd ） as outputs. The prediction performance of the ML models was evaluated using cross-validation and comparison with supplementary test data. Furthermore， the distribution of mechanical parameters of frozen clay in multi-parameter input space was analyzed based on the optimal ML model， followed by parameter sensitivity analysis combining model interpretability （SHAP （SHapley Additive exPlanations） method）. The results indicated that ML methods could accurately predict the SSC pattern and qd of frozen clay， with the MLP model demonstrating the optimal prediction performance. The ML prediction models could simulate the complex nonlinear relationships of the SSC pattern and failure strength qd of frozen clay with different input parameters within multi-parameter input spaces. The SHAP method effectively quantified the influence degree of four input parameters on the mechanical parameters of frozen clay. The influence of four parameters on SSC pattern， from largest to smallest， was found to be in the order of α， p， T， and b， while for qd， the order was T， b， α， and p. This study provides new insights for the theoretical research on frozen soil mechanics and engineering design in cold regions.
Hydrothermal changes in ice-rock debris accumulation under freeze-thaw cycles are a key concern for geological disaster early warning and prevention in alpine regions. The mechanism of hydrothermal coupling remains a key challenge in current research. To address this issue， model tests were conducted in a freezer on ice-rock debris accumulation with different numbers of freeze-thaw cycles and volumetric ice contents （12%， 16%， 20%）. Temperature sensors were deployed to monitor hydrothermal interactions， while water migration under freeze-thaw cycles was observed. The experiment analyzed temperature response differences at key locations （slope foot， slope face， and slope crest）， analyzing the effects of ice content and freeze-thaw cycles on heat transfer during heating and cooling phases. Particular focus was given to the “zero-point curtain” phenomenon and its contributing factors. The results showed that： （1） there were obvious differences in the response of debris accumulation to ambient temperature changes at different locations. Specifically， the temperature change characteristics differed significantly between the slope foot， slope face， and slope crest， with response degree decreasing in the order： slope foot＞slope face＞slope crest. （2） When volumetric ice content increased from 12% to 20%， the peak temperature decreased by about 15%， and the time to reach peak temperature was delayed by about 20 minutes. Higher ice content resulted in lower sensitivity of ice-rock debris accumulation to ambient temperature changes， and the presence of ice debris significantly prolonged the soil’s response time to temperature changes. （3） With increasing ice content， during warming phase， the heating rate and maximum temperature decreased， with reduced thawing depth. During cooling phase， the cooling rate remained consistent and the minimum temperature was stable， while freezing depth increased. The “zero-point curtain” phenomenon occurred mainly within the depth range of 16.5~30 cm， with position deepening and duration shortening as freeze-thaw cycles increased. （4） With increasing freeze-thaw cycles， the debris accumulation exhibited enhanced temperature sensitivity to ambient changes， while the soil’s thawing depth first decreased and then increased， with both thawing and freezing depths becoming larger， showing stronger heat accumulation. （5） The slope face and slope crest served as main heat exchange paths， with their intersection showing more complex heat transfer mechanisms during freeze-thaw cycles due to bidirectional boundary temperature effects. This study analyzes the water-heat coupling mechanism in ice-rock debris accumulation under freeze-thaw cycles， revealing the effects of ice content and cycle numbers on temperature sensitivity， response time， and heat transfer patterns.
Electrokinetic remediation is an in situ remediation technology suitable for low-permeability soils， where pollutant migration is closely related to moisture migration. While existing research has explored the moisture migration patterns in thawed soils under electric fields， the patterns of moisture migration in heavy metal-contaminated frozen soil remain unclear. This study investigated the moisture migration patterns of lead （Pb）-contaminated frozen soil under an electric field， examining the effects of temperature， Pb²⁺ concentration， and electric potential gradient on both moisture migration volume and current. The results showed that under the influence of the electric field， the current variation pattern gradually transitioned from a peaked to a non-peaked form as the temperature， Pb²⁺ concentration， and potential gradient decreased， with the time of peak current occurrence progressively delayed. Additionally， moisture migrated towards the cathode. The volume of moisture migration decreased as Pb²⁺ concentration increased and increased with higher potential gradients. The effect of temperature on moisture migration was closely related to Pb²⁺ migration pattern. Although higher potential gradients promoted moisture migration， under the conditions of low temperature and low Pb²⁺ concentration， they could induce the premature formation of insoluble precipitates at the cathode. These precipitates hindered further moisture migration， thereby reducing the overall efficiency of electrokinetic remediation. Therefore， in practical applications， it is essential to comprehensively consider the combined effects of potential gradient and temperature to optimize moisture migration and minimize precipitate formation.
The water transfer capacity of the South-to-North Water Transfer Middle Route Project is limited during ice periods， which has become a major challenge to its safe operation and full realization of social benefits. To improve winter water transfer capacity， it is imperative to thoroughly investigate the evolution patterns of ice regimes and their driving factors in the main channel of the Middle Route. Based on measured winter data from 2014 to 2022， including ice regimes， water temperature， hydraulic parameters， and meteorological factors at typical cross-sections such as Beijuma River， Cao River， and Hutuo River， this study investigated the spatiotemporal distribution characteristics of ice regimes and the statistical patterns of different influencing factors across various ice regimes. Key factors influencing ice regimes were identified and quantified using Grey Relational Analysis （GRA） and eXtreme Gradient Boosting （XGBoost）. The results showed that ice-affected regions were mainly located in the section from Qili River inverted siphon to Beijuma River culvert， while high-risk zones of ice cover and ice jams were concentrated between the Hutuo River and Beijuma River sections. Since the project began operation， both ice period duration and freeze-up duration have shown decreasing trends. Indicators such as water temperature， air temperature， and flow rate exhibited significant differences and unimodal distribution characteristics across different types of ice regimes. The Grey relational coefficients of water temperature， daily average temperature， minimum temperature， three-day sliding temperature sum， three-day sliding negative accumulated temperature， and flow rate all exceeded 0.9， and their corresponding feature importance was above 400， indicating strong effects on ice regimes. Other factors showed comparatively weak effects. These research findings provide a reliable basis for developing an intelligent prediction model for water temperature and ice regimes in the main channel， and offer valuable insights for enhancing winter operation management of the project.
The alpine mountainous regions at medium and low latitudes are abundant in freshwater resources， which are vital for ensuring water supply to downstream areas. The loose sediments in the seasonally frozen soil regions serve as vital channels connecting the mountains to rivers. The interplay between groundwater and surface water significantly affects the availability of water resources and the stability of ecosystems in these regions. To investigate the interaction mechanism between groundwater and surface water in the seasonally frozen soil region of an alpine watershed， this paper took the seasonally frozen soil region of the Hulugou catchment in the Qilian Mountains as the research object. Based on the hydrogeological conditions and groundwater level monitoring data of the region， a three-dimensional groundwater flow numerical model was constructed using GMS software to simulate and analyze groundwater-surface water exchanges under seasonal freeze-thaw conditions. The results showed that： （1） During the cold season （January to March， October to December）， the frozen state of the seasonally frozen layer hindered the water supply to the tributary streams. However， due to its discontinuous distribution， there were still some unfrozen areas under the riverbed of the tributaries， allowing groundwater to contribute to streamflow in the east and west tributaries， with total conversion amounts of 4 927 m³ and 4 796 m³， respectively. These conversion amounts were positively correlated with the hydraulic gradient between recharge and discharge zones of the alluvial-proluvial porous aquifer. （2） During the warm season （April to September）， tributary streams received more water from rainfall and snowmelt， and the interaction shifted to surface water recharging groundwater， with total conversion amounts of 120 060 m³ and 141 208 m³， respectively. （3） During the thawed period， the seasonally frozen soil layer had completely thawed， and the alluvial-proluvial porous aquifers exhibited strong hydraulic conductivity and water storage capacity. The interaction between groundwater and surface water was characterized by stream water in the east and west tributaries recharging groundwater， with total conversion amounts of 505 283 m³ and 889 461 m³， respectively. （4） During the refreezing period， with the seasonally frozen soil layer gradually freezing and precipitation events being relatively sparse， the water replenishment to the east and west tributaries decreased. The interaction between groundwater and surface water in the east and west tributaries was characterized by groundwater discharging into surface water， with total conversion amounts of 272 261 m³ and 100 394 m³， respectively. Additionally， the interaction between groundwater and surface water in the mainstream throughout the hydrological year was characterized by groundwater discharging to surface water， with the total contribution amount and ratio of 9 235 476 m³ and 70.84%， respectively. Moreover， the contribution amount and contribution ratio of groundwater varied with the seasons. Compared with the other three periods， groundwater contribution was higher during the thawed period， although its proportion was lower （62%）. However， the accuracy of this study in examining the spatiotemporal scales of groundwater and surface water interaction processes in seasonally frozen soil regions remained limited. Throughout the year， groundwater remained the primary contributor to streamflow at the catchment outlet， with seasonal variations in contribution volume and proportion. Compared to the cold season （90.12%）， the warm season had a higher groundwater contribution volume but a lower proportion （65.76%）. The research results provide a theoretical basis for studying the runoff formation mechanism in alpine mountainous areas and its response to climate change. They have important practical significance for the scientific management， rational development and utilization of water resources in cold regions， and sustainable socio-economic development.
Rainstorms are the primary causes of flash flood disasters on the northern slope of the Kunlun Mountains. Limited observational data have resulted in relatively insufficient research on rainstorms in this region. Using hourly rainfall data from automatic weather stations in summer （2016—2023）， this study compared and analyzed the detailed characteristics and altitudinal differences of rainstorms in the western and central sections of the northern slope of the Kunlun Mountains. Furthermore， the altitude-dependent variations in these characteristics were quantified， thereby providing a scientific basis for deepening the understanding of rainstorm dynamics in arid mountainous regions and enhancing forecasting accuracy， early warning capabilities， and disaster mitigation efforts related to rainstorms on the northern slope of the Kunlun Mountains. The results showed that in the western section， both the number of rainstorm days and stations experiencing rainstorm initially increased and then decreased with increasing altitude， while showing continuous increase in the central section. The average rainfall of rainstorms in the western section was lower compared to that in the central section. The maximum rainstorm rainfall occurred in areas at altitudes exceeding 1 500-2 000 m in the western section and below 1 500 m in the central section， respectively. Furthermore， the proportion of rainstorm days and stations experiencing short-duration heavy rainfall events in the western section （central section） was generally higher （lower） than the average in southern Xinjiang. With increasing altitude， the proportion of rainstorms with short-duration heavy rainfall in the western section decreased from 56.0% to 11.1%， while in the central section it remained below 50.0%. Nocturnal rainfall predominated at all altitudes in the western section （55.0%~73.6%）. In the central section， nocturnal rainfall dominated in the plain and low mountainous areas （accounting for 54.3%~59.1%）， while daytime rainfall was more prevalent in the mid and high mountainous areas （accounting for 51.3%~56.8%）. The average duration of rainstorm events was 12.0 hours in the western section and 15.5 hours in the central section. In both sections， the average rainstorm duration increased with altitude. A “three-peak” pattern was observed in the diurnal variation characteristics of rainfall amounts during rainstorms in both the western and central sections， but with differing peak timings and intensities. With increasing altitude， the nighttime and morning rainfall peaks in the central section weakened， while the afternoon peak strengthened. In the western section， the temporal distribution of rainfall peaks remained relatively stable across altitudes， predominantly occurring during nighttime hours. The nighttime peak in the western section resulted from the combined effects of high rainfall frequency and intensity. In the central section， the nighttime peak in plains and low mountainous areas was primarily caused by high rainfall intensity， while the daytime peak was attributed to high rainfall frequency. The afternoon peak in the high mountainous areas resulted from both high frequency and intensity. Currently， automatic weather stations on the northern slope of the Kunlun Mountains are unevenly distributed in the western and central sections， with a concentration in low-altitude areas， which limits the comprehensive characterization of the fine-scale characteristics of summer rainstorms in the region. This study focuses solely on statistical analysis， with minimal investigation into the underlying mechanisms. Future research should employ synoptic analysis， diagnostic methods， and numerical modeling to better understand the causes of varying rainstorm distributions across different regions on the northern slope of the Kunlun Mountains.
The Qilian Mountain National Nature Reserve in Gansu and the Important Water Source Recharge Ecological Functional Area of Yellow River in Gannan are two major ecological functional areas in Gansu. Establishing a scientific and effective ecological compensation mechanism is crucial for ensuring ecological security and promoting sustainable development in the region. To address this issue， this study selected data from four prefecture-level cities in the Qilian Mountain National Nature Reserve in Gansu and the Important Water Source Recharge Ecological Functional Area of Yellow River in Gannan from 2010 to 2023， and analyzed their ecological compensation performance， main obstacle factors， and the coupling coordination among economic， social， and ecological performance using the entropy-weighted TOPSIS method， obstacle factor diagnostic model， and coupling coordination degree model. The results showed that： （1） the comprehensive ecological compensation performance of the Qilian Mountain National Nature Reserve in Gansu increased from 0.234 to 0.701， improving from a poor level to a good level， while that of the Important Water Source Recharge Ecological Functional Area of Yellow River in Gannan fluctuated from 0.349 to 0.606， shifting from a qualified level to a good level. （2） Among the four prefecture-level cities， the ecological compensation performance of the three cities under the jurisdiction of the Qilian Mountain National Nature Reserve in Gansu showed regional heterogeneity. Among them， Jinchang ranked highest， Zhangye was in the middle， and Wuwei ranked the lowest. （3） The main obstacle factors affecting the ecological compensation performance of the Qilian Mountain National Nature Reserve in Gansu included the value of production of ecological material products in economic performance， the number of people covered by unemployment insurance in social performance， and the daily treatment capacity of urban wastewater in ecological performance. For the Important Water Source Recharge Ecological Functional Area of Yellow River in Gannan， main obstacle factors included the green coverage rate of built-up areas in social performance and the total water consumption in ecological performance. The results indicated regional heterogeneity in the ecological compensation performance across the cities. （4） The coupling coordination degree of ecological compensation performance in the Qilian Mountain National Nature Reserve in Gansu increased from 0.466 to 0.844， improving from borderline imbalance to good coordination. In the Important Water Source Recharge Ecological Functional Area of Yellow River in Gannan， the coordination degree fluctuated from 0.530 to 0.785， shifting from barely coordinated to moderately coordinated. Therefore， it is recommended to improve the ecological compensation mechanism by refining laws and regulations， standardizing compensation criteria， clarifying compensation subjects and targets， diversifying funding sources， and strengthening performance evaluation， so as to provide a basis for strengthening the ecological security barrier in western China and promoting the positive interaction between ecological protection and economic development in the important water source recharge area of the upper reaches of the Yellow River.
This study aims to advance the automation of frozen soil observation and improve monitoring accuracy to address the limitations of traditional manual observation methods including operational complexity， significant subjective errors， and inability to achieve continuous monitoring. To this end， by comparing observation data from five types of automatic frozen soil observers （DTD1-DTD5） with manual frost tubes， this study comprehensively evaluated their data quality to provide a scientific basis for meteorological operation. Parallel observation data were collected from DTD1、DTD2、DTD3、DTD4 and DTD5 automatic frozen soil observers and manual frost tubes installed at 1 172 meteorological observation stations across 24 provinces （autonomous regions/municipalities） in China from 2022 to 2024. The data quality was evaluated from five aspects： data integrity （completeness rate ≥98%）， accuracy （standard deviation ≤2 cm）， consistency rate （≥80%）， mean misjudgment （≤6 cm）， and freeze-thaw trend （correlation of maximum frozen soil depth data ≥0.8）. As of winter 2024， there were 349 sets of devices in the first operational stage， 364 sets in the second stage， and 459 sets in single-track operation stage. The results showed that the DTD2 and DTD3 automatic frozen soil observers showed excellent performance in all five aspects， with pass rates of 88.73% and 88.24% for single-track operation， respectively， significantly higher than those of other types of devices. These findings indicate that the DTD2 and DTD3 automatic frozen soil observers provide high-quality data that meet the requirements for meteorological operation and are recommended for prioritized implementation in future operational activities.
To address the challenges of insufficient interdisciplinary integration， weak practical training， and inadequate incorporation of professional ideological and political education in the postgraduate teaching of polar remote sensing， this study proposes a three-stage progressive course group of “theory-technology-frontier” and constructs a practical training framework driven by expedition， while exploring effective approaches to integrate professional training with ideological and political education. By integrating earth system science， remote sensing technology， and frontier research topics， polar expedition data are transformed into teaching resources. Through tiered field practices and Arctic expeditions， this study strengthens the coordination between technological development and scientific inquiry. A framework for ideological and political education aligned with national strategic needs is designed to broaden students’ global perspectives. Practical results show that this method can effectively promote interdisciplinary knowledge integration and cultivate versatile professionals for polar studies.
