The instability of soil bank slopes induced by freeze-thaw cycles at the northern foot of Tianshan Mountain is very common.The failure not only caused a large amount of soil erosion,but also led to serious reservoir s...The instability of soil bank slopes induced by freeze-thaw cycles at the northern foot of Tianshan Mountain is very common.The failure not only caused a large amount of soil erosion,but also led to serious reservoir sedimentation and water quality degradation,which exerted a lot of adverse effects on agricultural production in the local irrigation areas.Based on field investigations on dozens of irrigation reservoirs there,laboratory tests were carried out to quantitatively analyze the freeze-thaw effect on the soil engineering characteristics to reveal the facilitation on the bank slope instability.The results show that the softening characteristics of the stressstrain curves gradually weaken,the effective cohesions decline exponentially,the seepage coefficients enlarge,and the thermal conductivities decrease after 7 freeze-thaw cycles.The freeze-thaw effect on the specimens with low confining pressures,low dry densities and high water contents is more significant.The water migration and the phase transition between water and ice result in the variations of the soil internal microstructures,which is the main factor affecting the soil engineering characteristics.Sufficient water supply and the alternation of positive and negative temperatures at the reservoir bank slopes in cold regions make the water migration and phase transition in the soil very intensely.It is easy to form a large number of pores and micro cracks in the soil freezing and thawing areas.The volume changes of the soil and the water migration are difficult to reach a dynamic balance in the open system.Long-term freeze-thaw cycles will bring out the fragmentation of the soil particles,resulting in that the micro cracks on the soil surfaces are developing continuously.The soil of the bank slopes will fall or collapse when these cracks penetrate,which often happens in winter there.展开更多
The contact between contaminant and washing solution is a fundamental factor that limits the contaminant removal efficiency of chemical washing.In this study,the magnetization technique was employed to improve the phy...The contact between contaminant and washing solution is a fundamental factor that limits the contaminant removal efficiency of chemical washing.In this study,the magnetization technique was employed to improve the physicochemical properties of ethylene diamine tetraacetic acid(EDTA)solutions for the removal of lead(Pb)and cadmium(Cd)from a contaminated clayey soil.Furthermore,EDTA concentration,magnetization strength,and magnetization time were varied as parameters for enhancing the contact between contaminant and washing solution to improve remediation efficiency.The results showed that after magnetization,the viscosities,surface tensions,and contact angles of EDTA solutions decreased,whereas the electrical conductivity and pH increased.In particular,the viscosities of high-concentration EDTA solutions increased with increasing magnetic field strength and magnetization time.The magnetized EDTA solutions increased the maximum removal rates of Cd and Pb by 64.46% and 35.49%,respectively,compared to the unmagnetized EDTA solutions.The results highlighted the efficient metal removal by magnetized washing solutions due to the better contact between the washing solutions and the contaminants.The magnetic-enhanced soil washing method was proven to be efficient,cost-effective,and easily implementable for enhancing heavy metal removal.This study provides a valuable reference for improving the efficiency of chemical washing for heavy metal-contaminated clayey soils.展开更多
The source region of the Yellow River(SRYR),with its semi-humid to semi-arid climate,is crucial for understanding water resource dynamics.Precipitation is key for replenishing surface water and balancing the ecosystem...The source region of the Yellow River(SRYR),with its semi-humid to semi-arid climate,is crucial for understanding water resource dynamics.Precipitation is key for replenishing surface water and balancing the ecosystem’s water cycle.However,the soil moisture response to precipitation across climate zones and soil layers remains poorly understood due to limited long-term data.This study examines the response of soil moisture to precipitation at multiple time scales in the SRYR,using data from Maqu,Mado,Ngoring Lake sites,and the Maqu monitoring network(MMN),along with CN05.1 precipitation and GLEAM v3.8a soil moisture data.Results show that the semi-humid area requires more precipitation to trigger soil moisture responses compared to the semi-arid area in the SRYR.Surface soil at Maqu,MMN,Ngoring Lake,and Mado sites require at least 8.6,8.4,5.2,and 2.84 mm of precipitation,respectively,for effective replenishment.Significant responses to precipitation events were observed in soil layers at 40 cm and above in the semi-humid area,while at 20 cm and above in the semi-arid area.Precipitation volume is the primary factor influencing soil moisture,affecting both the increment and time lag to maximum moisture.Precipitation intensity and pre-rain moisture have no direct effect.In the central SRYR,accumulated precipitation has a greater impact.Root-zone soil moisture has a weaker correlation with precipitation compared to surface soil moisture but persists longer,responding for up to 10 days,while surface soil moisture responds more immediately but only lasts about 5 days.展开更多
Sudden temperature drops cause soils in natural environments to freeze unidirectionally,resulting in soil expansion and deformation that can lead to damage to engineering structures.The impact of temperature-induced f...Sudden temperature drops cause soils in natural environments to freeze unidirectionally,resulting in soil expansion and deformation that can lead to damage to engineering structures.The impact of temperature-induced freezing on deformation and solute migration in saline soils,especially under extended freezing,is not well understood due to the lack of knowledge regarding the microscopic mechanisms involved.This study investigated the expansion,deformation,and water-salt migration in chlorinated saline soils,materials commonly used for canal foundations in cold and arid regions,under different roof temperatures and soil compaction levels through unidirectional freezing experiments.The microscopic structures of saline soils were observed using scanning electron microscopy(SEM)and optical microscopy.A quantitative analysis of the microstructural data was conducted before and after freezing to elucidate the microscopic mechanisms of water-salt migration and deformation.The results indicate that soil swelling is enhanced by elevated roof temperatures approaching the soil's freezing point and soil compaction,which prolongs the duration and accelerates the rate of water-salt migration.The unidirectional freezing altered the microstructure of saline soils due to the continuous temperature gradients,leading to four distinct zones:natural frozen zone,peak frozen zone,gradual frozen zone,and unfrozen zone,each exhibiting significant changes in pore types and fractal dimensions.Vacuum suction at the colder end of the soil structure facilitates the upward migration of salt and water,which subsequently undergoes crystallization.This process expands the internal pore structure and causes swelling.The findings provide a theoretical basis for understanding the evolution of soil microstructure in cold and arid regions and for the management of saline soil engineering.展开更多
Since scarce knowledge of soil mercury(Hg)concentrations and risks in the vulnerable Xinjiang,topsoils(0-15 cm)from its typical landscapes were extensively sampled.Topsoil total mercury(THg)concentrations varied broad...Since scarce knowledge of soil mercury(Hg)concentrations and risks in the vulnerable Xinjiang,topsoils(0-15 cm)from its typical landscapes were extensively sampled.Topsoil total mercury(THg)concentrations varied broadly between 0.9 and 35.3 ng/g,of which16.8%exceeded the background value of soil Hg for Xinjiang.Topsoil THg concentrations across various landscapes exhibited a declining order:farmland(11.7±6.0 ng/g)>grassland(10.5±8.5 ng/g)>woodland(10.2±8.2 ng/g)>desert(7.0±5.8 ng/g).The average topsoil THg concentration was higher in northwestern Xinjiang(11.3±7.2 ng/g)than that in southeastern Xinjiang(6.3±6.1 ng/g).Relatively high topsoil THg concentrations were observed near the cities with intensive human activities,followed by a gradual decline to the surroundings.The concentrations of topsoil THg were strongly correlated with the contents of total organic carbon(TOC),clay,silty,and sandy,and the distance from each sampling site to its nearest city,suggesting that the variation of topsoil Hg was significantly influenced by TOC content,soil granularity,and anthropogenic Hg emissions.Silty and TOC were the principal affecting factors,explaining 48.7%and 7.9%of the THg variation,respectively.The contamination and potential ecological risk evaluations revealed that topsoils in regions with dense populations were polluted with Hg and contained higher potential ecological risks.The health risk evaluations indicated that exposure risks of topsoil Hg were higher for children than those for adults.Fortunately,topsoil Hg posed acceptable risks to human health.展开更多
Due to the high water content in warm frozen soil,the pore water pressure and pore ice pressure generated within the sample during loading significantlyinfluencethe deformation and strength of the soil skeleton.Theref...Due to the high water content in warm frozen soil,the pore water pressure and pore ice pressure generated within the sample during loading significantlyinfluencethe deformation and strength of the soil skeleton.Therefore,it is essential to develop a constitutive model for warm frozen soil that can capture the changes in ice pressure and water pressure.This study introduces a macro-meso constitutive model based on a binary-medium framework to describe the mechanical behavior of warm frozen soil.In this model,warm frozen soil is conceptualized as consisting of bonded and frictional elements from a meso perspective.The bonded elements are modeled using a macro-meso elastic constitutive approach based on poromechanics,while the frictional elements employ a macro-meso elastoplastic approach,also grounded in poromechanics.These two elements are then linked within the binarymedium model framework.By replicating the experimental curves of warm frozen soils,the theoretical results from the proposed model show excellent agreement with experimental data.This consistency indicates that the model effectively simulates the strain softening and volumetric expansion behaviors of warm frozen soil samples under various conditions.Additionally,the constitutive model predicts changes in unfrozen water pressure,frozen temperature,unfrozen water saturation,and porosity during the loading process of warm frozen soil samples.展开更多
Affected by climate warming and anthropogenic disturbances,the thermo-mechanical stability of warm and ice-rich frozen ground along the Qinghai-Tibet engineering corridor(QTEC)is continuously decreased,which may delay...Affected by climate warming and anthropogenic disturbances,the thermo-mechanical stability of warm and ice-rich frozen ground along the Qinghai-Tibet engineering corridor(QTEC)is continuously decreased,which may delay the construction of major projects in the future.In this study,based on chemical stabilization of warm and icerich frozen ground,the soil-cement column(SCC)for ground improvement was recommended to reinforce the foundations in warm and ice-rich permafrost regions.To explore the validity of countermeasures mentioned above,both the original foundation and the composite foundation consisting of SCC with soil temperature of-1.0℃were prepared in the laboratory,and then the plate loading tests were carried out.The laboratory investigations indicated that the bearing capacity of composite foundation consisting of SCC was higher than that of original foundation,and the total deformation of original foundation was greater than that of composite foundation,meaning that overall stability of foundation with warm and ice-rich frozen soil can be improved by SCC installation.Meanwhile,a numerical model considering the interface interaction between frozen soil and SCC was established for interpretating the bearing mechanism of composite foundation.The numerical investigations revealed that the SCC within composite foundation was responsible for the more applied load,and the applied load can be delivered to deeper zone in depth due to the SCC installation,which was favorable for improving the bearing characteristic of composite foundation.The investigations provide the valuable guideline for the choice of engineering supporting techniques to major projects within the QTEC.展开更多
The construction of water conservancy projects in cold regions experiences freezing-thawing cycles,which can greatly change the engineering properties of soil and have a significant impact on the construction of proje...The construction of water conservancy projects in cold regions experiences freezing-thawing cycles,which can greatly change the engineering properties of soil and have a significant impact on the construction of projects.Lianghekou Hydropower Station(LHS),is a controlling station with the largest installed capacity among the 7 middle reach projects in the Yalong River,the secondary tributary of the Yangtze River.LHS is located in a seasonally frozen soil area.Based on the measured data of air and ground temperature in winter in the dam core wall,the freezing-thawing variation of gravelly soil and contact clay during the filling process of the core wall are compared and analyzed,then the main impact factors of the freezing-thawing variation of soils are discussed.The results show that under the influence of air temperature,soil freezes unidirectionally from ground surface downward and deepens gradually,and the thawing processes are different at the aspects of thawing direction and rate.Air temperature and physical properties of soil including soil type,moisture content and dry density affect the freezingthawing processes of soils.And the impact of engineering construction is more remarkable than natural factors.The engineering construction affects soil temperature and freezing-thawing process by controlling the initial temperature of soil,the speed and duration of the technological conversion of paving,compaction,and the length of placed duration at night.Due to the long placed duration of soil with the slow construction method,the initial temperature of soil gradually reduces,the heat transfer process inside soil is fast.Then the internal heat of soil releases,the decreasing rate of ground temperature of soil at different depths is fast and the frozen depth deepens.While due to the short placed duration of soil with the rapid construction process,the initial temperature of soil is high,high internal heat of soil is supplied every day,and the heat transfer process inside soil is slow.Then the decreasing rate of temperature of soil at different depths is slow,and the variation amplitude of frozen depth is small.This study provides useful guidance for the freezingthawing prevention during the construction process of core wall dams located at high altitude region in winter.展开更多
Microplastics(MPs)become ubiquitous in soil and are an environmental and public health concern worldwide.However,the status of MPs in natural and farmland soils in remote areas remains poorly understood.In this study,...Microplastics(MPs)become ubiquitous in soil and are an environmental and public health concern worldwide.However,the status of MPs in natural and farmland soils in remote areas remains poorly understood.In this study,we investigated the characteristics of MPs in natural and farmland soils along two transects in the Qilian Mountains of the northern Tibetan Plateau.The average abundance of MPs in natural and farmland soils was 29,778 and 56,123 items kg^(-1),respectively,with a detection size range of 10-1000μm.MPs in the size range of 10-100μm accounted for 84.1%of particles detected.Among the 21 polymers detected,polyethylene dominated in both farmland and natural soils.The shape of MPs was dominated by fragments(95.8%),followed by fibers(3.8%)and beads(0.4%).The abundance of MPs was positively correlated with increasing altitude in natural soils.There was no significant correlation between the abundance of MPs and soil physicochemical properties due to the narrow range of values of soil physicochemical properties.With the growing concern regarding MPs pollution,research on the status of MPs in high altitude and remote areas is critical to understanding their global cycle.展开更多
The warm and ice-rich frozen soil is characterized by high unfrozen water content, low shear strength and large compressibility, which is unreliable to meet the stability requirements of engineering infrastructures an...The warm and ice-rich frozen soil is characterized by high unfrozen water content, low shear strength and large compressibility, which is unreliable to meet the stability requirements of engineering infrastructures and foundations in permafrost regions. In this study, a novel approach for stabilizing the warm and ice-rich frozen soil with sulphoaluminate cement was proposed based on chemical stabilization. The mechanical behaviors of the stabilized soil, such as strength and stress-strain relationship, were investigated through a series of triaxial compression tests conducted at -1.0℃, and the mechanism of strength variations of the stabilized soil was also explained based on scanning electron microscope test. The investigations indicated that the strength of stabilized soil to resist failure has been improved, and the linear Mohr-Coulomb criteria can accurately reflect the shear strength of stabilized soil under various applied confining pressure. The increase in both curing age and cement mixing ratio were favorable to the growth of cohesion and internal friction angle. More importantly, the strength improvement mechanism of the stabilized soil is attributed to the formation of structural skeleton and the generation of cementitious hydration products within itself. Therefore, the investigations conducted in this study provide valuable references for chemical stabilization of warm and ice-rich frozen ground, thereby providing a basis for in-situ ground improvement for reinforcing warm and ice-rich permafrost foundations by soil-cement column installation.展开更多
The formation and growth of segregation ice dominate the frost heave during soil freezing,which is closely related to water migration.To analyze segregation ice during soil freezing for different soils,a freezing-thaw...The formation and growth of segregation ice dominate the frost heave during soil freezing,which is closely related to water migration.To analyze segregation ice during soil freezing for different soils,a freezing-thawing experiment was conducted with Lanzhou loess(LZL)and Qinghai-Tibet Plateau silty clay(QSC)using a novel layered nuclear magnetic resonance approach.During LZL freezing,the unfrozen water content first increased and then decreased with decreasing temperature near the freezing front,but decreased with decreasing temperature in other layers,whereas during the freezing of QSC,the unfrozen water content in different layers(including the freezing front)decreased with decreased temperature.Notably,the increased liquid water near the freezing front during LZL freezing was primarily adsorbed water.In addition to the temperature gradient,the squeezing action during soil freezing was another important factor affecting water migration,especially at the early stage of soil freezing.However,which of the two factors,squeezing action and temperature gradient,was the dominant one causing water migration depended on soil structure.At the early stage of soil freezing,the squeezing action had a significant effect on the water migration of LZL,but no significant effect on that of QSC.Furthermore,water accumulation of LZL near the freezing front due to squeezing action at the early stage of freezing limited the formation and growth of segregation ice.This study provided an improved understanding for ice segregation and water migration during soil freezing.展开更多
Soil microbial communities are pivotal in permafrost biogeochemical cycles,yet the variations of abundant and rare microbial taxa and their impacts on greenhouse gas emissions in different seasons,remain elusive,espec...Soil microbial communities are pivotal in permafrost biogeochemical cycles,yet the variations of abundant and rare microbial taxa and their impacts on greenhouse gas emissions in different seasons,remain elusive,especially in the case of soil archaea.Here,we conducted a study on soil abundant and rare archaeal taxa during the growing and non-growing seasons in the active layer of alpine permafrost in the Qinghai-Tibetan Plateau.The results suggested that,for the archaeal communities in the sub-layer,abundant taxa exhibited higher diversity,while rare taxa maintained a more stable composition from the growing to non-growing season.Water soluble organic carbon and soil porosity were the most significant environmental variables affecting the compositions of abundant and rare taxa,respectively.Stochastic and deterministic processes dominated the assemblies of rare and abundant taxa,respectively.The archaeal ecological network influenced N_(2)O flux through different modules.Rare taxa performed an essential role in stabilizing the network and exerting important effects on N_(2)O flux.Our study provides a pioneering and comprehensive investigation aimed at unravelling the mechanisms by which archaea or other microorganisms influence greenhouse gas emissions in the alpine permafrost.展开更多
The thawing and warming of ice-rich permafrost present a considerable threat to the long-term stability of the Qinghai-Xizang Railway(QXR)on the roof of the world—that is,the Qinghai-Xizang Plateau(QXP).In this revie...The thawing and warming of ice-rich permafrost present a considerable threat to the long-term stability of the Qinghai-Xizang Railway(QXR)on the roof of the world—that is,the Qinghai-Xizang Plateau(QXP).In this review,we explore the extent of the observed permafrost degradation and embankment damage under the coupled impacts of climate change and engineering construction.The ice-rich permafrost beneath the embankment presents a substantial threat to the thermal-mechanical stability of the embankment due to the permafrost’s accelerated and amplified degradation.The observed embankment deformation has a potential high risk of thaw settlement,especially for 656 embankment-bridge sections,whose potential high risk of thaw settlement may be as great as 25%.Several techniques for roadbed cooling can be used to alleviate these impacts,including crushed rock structure embankments(CRSEs),thermosyphons,and reinforcement measures,which have been demonstrated to be successful in cooling the underlying permafrost and stabilizing an embankment.Under future climate change and permafrost degradation,however,the QXR still faces a high risk of embankment damage caused by permafrost degradation and requires more effective methods to reinforce the thermal-mechanical stability of permafrost.Therefore,a better understanding of such high-risk regions is needed,and roadbed cooling techniques will require further adaption in order to address the issues brought by climate change.展开更多
Permafrost,a critical component of Earth’s climate system,is increasingly subject to abrupt thaw events,which jeopardize infrastructure,reshape landforms,alter hydrological regimes,and disrupt ecosystems,thereby posi...Permafrost,a critical component of Earth’s climate system,is increasingly subject to abrupt thaw events,which jeopardize infrastructure,reshape landforms,alter hydrological regimes,and disrupt ecosystems,thereby posing substantial threats to global sustainability.However,the underlying mechanisms that trigger these abrupt transitions remain incompletely understood.Here,we present decade-long in-situ observations from HRQ1,a marginal permafrost site in the Headwater Area of the Yellow River,northeastern Qinghai-Xizang Plateau.These data reveal the formation and growth of a talik,indicative of a permafrost tipping point.Absent before 2017,the talik subsequently formed and progressively deepened,extending to the maximum observation depth of 300 cm by 2024.The transition from perennially frozen to thawed conditions was accompanied by a substantial increase in mean annual soil temperature(MAST)throughout the entire soil profile.From 2015 to 2023,MAST in the upper 200 cm rose from sub-zero(−0.30 to−0.49℃)to consistently above 0℃(0.07 to 1.08℃).Concurrently,maximum daily soil temperatures in deeper layers(200–300 cm)became positive,indicating thaw propagation into the relict permafrost.This warming coincided with a marked increase in unfrozen soil moisture,particularly within the expanding talik.The rapid,non-linear deepening of the talik,far exceeding rates attributable to conductive heat transfer alone,was driven by a strong convective mechanism(Rayleigh-Darcy instability).This advective process was triggered when the soil profile became fully saturated,a condition resulting from the convergence of intensified rainfall and enhanced water retention linked to decadal vegetation greening.Intriguingly,despite the accelerated subsurface warming,the annual amplitude of ground surface temperature decreased from 29.0±2.8℃ to 24.5±3.6℃ following talik formation,likely due to the buffering effect of increased vegetation cover,which modified the surface energy balance.Our results demonstrate that climatic warming and wetting can initiate a cascade of internal feedbacks,propelling marginal permafrost beyond an abrupt tipping point.These findings emphasize the acute vulnerability of marginal permafrost and highlight the urgent necessity for sustained monitoring to assess ecosystem stability and quantify associated greenhouse gas emissions.展开更多
The strength characteristics of ice materials are crucial for the analysis of the interaction between ice and structure in ocean engineering and ice engineering.In this investigation,six machine learning methods were ...The strength characteristics of ice materials are crucial for the analysis of the interaction between ice and structure in ocean engineering and ice engineering.In this investigation,six machine learning methods were utilized to predict the strength of the envelope surface of ice materials.The database for the ice strength was first established by collecting 1,481 testing data reported in the previous literatures.A quadric strength criterion was adopted to describe failure behaviors of ice materials under different conditions of material property and laboratory.Three model parameters in this strength criterion were forecasted by using six machine learning methods.The prediction capacities of six machine learning methods were evaluated by three statics indices,and the integrated simulation ability of six machine learning methods was arranged.Three machine learning algorithms were selected to be improved and optimized,and the simulation capacity of the three algorithms was further explored.The optimization results indicate that the improved potential of the Ensemble algorithm is much higher than that of the SVM algorithm and the GPR algorithm for predicting the ice strength.展开更多
Microplastics have emerged as one of the most significant threats to the Earth's ecosystems due to their persistence,ability to carry high loads of contaminants,and biotoxicity.The Tibetan Plateau is a hotspot for...Microplastics have emerged as one of the most significant threats to the Earth's ecosystems due to their persistence,ability to carry high loads of contaminants,and biotoxicity.The Tibetan Plateau is a hotspot for global biodiversity conservation,but its ecosystem is fragile.This study systematically investigated the characteristics,distribution,sources,and ecological risk of microplastics in rivers and lakes across the Tibetan Plateau using the Laser Direct Infrared Imaging Spectroscopy(LDIR).The results indicated that the mean abundances of microplastics in water and sediments were 4250 items/m^(3)(n=50)and 3750 items/kg(n=44),respectively.Microplastics with small sizes(50-200μm),characterized by transparent and white fragments,were predominant.The most common polymers identified were polyamide(PA),polyurethane(PU),polyethylene terephthalate(PET),polyvinyl chloride(PVC),polypropylene(PP),and polyethylene(PE).Water sampling sites near urban/suburban effluent outfalls showed high levels of contamination.Microplastics in water are primarily derived from sewage effluent and atmospheric deposition.No single driver has been identified as the key factor influencing the spatial distribution of microplastics in water.The abundance of microplastics in sediments was significantly negatively correlated with the distance to the nearest city/town(p<0.01,R=-0.56)and significantly positively correlated with precipitation(p<0.01,R=0.60).Discarded or landfilled plastic waste is a major source of microplastics in sediments,which accumulate through transport by stormwater runoff caused by precipitation.Three ecological risk assessment models for microplastics were applied,and the high proportion of hazardous polymers such as PU,PVC,and PA was found to be responsible for the high ecological risk in the study area.This study provides an accurate and detailed exploration of the characteristics,sources,and spatial distribution of microplastic pollution by advanced automatic detection method in rivers and lakes on the Tibetan Plateau.展开更多
Snowmelt runoffis an important component of water resources in the Northwest China(NWC).With global cli-mate warming and the increasing frequency of extreme events,snowmelt floods have caused significant damage.Howeve...Snowmelt runoffis an important component of water resources in the Northwest China(NWC).With global cli-mate warming and the increasing frequency of extreme events,snowmelt floods have caused significant damage.However,current studies lack comprehensive research and systematic risk assessments of snowmelt floods across the NWC.Based on the snowmelt runoffsimulated by GLDAS-NOAH model(1948-2022),the multiple indicators of snowmelt floods were retrieved by Peaks Over Threshold(POT)model in the NWC,and comprehensive risk assessment was conducted by integrating socio-economic data.The results indicated that the snowmelt runoffin the NWC shows a significant increasing trend and exhibits a spatial pattern of being more abundant in the northwest and southwest edges while less in the central and eastern regions.In Northern Xinjiang,snowmelt floods occurred relatively infrequently but with large magnitudes,while around the Qilian Mountains,snowmelt floods were more frequent but of smaller magnitudes.The longest duration of snowmelt floods was observed in the Kashgar and Yarkant River.Basins near mountainous areas are prone to snowmelt floods,especially the Tongtian and Lancang River basins,as well as the Ebinur Lake,Ili River basin,and the rivers south of the Altai Mountains,which face the highest risk of snowmelt floods.Based on comprehensive assessment of hazard,expo-sure,vulnerability and adaptability,high and very high-risk areas account for 15.5%of the NWC.It is urgent to enhance monitoring,early warning systems,and implement corresponding disaster prevention and mitigation measures in large mountainous basins.展开更多
Under global warming,Asian glaciers have experienced accelerated retreats and increased mass loss.Utilizing data from the World Glacier Monitoring Service(WGMS),this study selected 16 representative glaciers across As...Under global warming,Asian glaciers have experienced accelerated retreats and increased mass loss.Utilizing data from the World Glacier Monitoring Service(WGMS),this study selected 16 representative glaciers across Asia to analyse the temporal and spatial changes of glacial mass balance(GMB),equilibrium line altitude(ELA),and accumulation area ratio(AAR)in the past several decades.Based on structural equation modelling and correlation analysis,we evaluated the responses of glacier change to climate change.The results indicated that 14 glaciers experienced mass loss,with the Parlung No.94 Glacier exhibiting a severe loss and significant retreat.In contrast,the Abramov,Muztag Ata No.15,Chhota Shigri,and Yala glaciers showed an increase in GMB,consistent with the"Karakoram Glacier anomaly".Additionally,a latitudinal gradient was observed,with ELA decreasing,AAR rising,and the rate and magnitude of glacier mass loss decreasing as latitude increased.GMB was negatively correlated with ELA and positively correlated with AAR,with the Vodopaniy No.125 Glacier showing the highest sensitivity to GMB variations.GMB fluctuation is influenced by energy(surface net solar radiation,air temperature)and precipitation.The significant decline of the Parlung No.94 Glacier was ascribed to rising temperature.From west to east in the Himalayas,the negative effects of energy on GMB decreased,with positive precipitation having a particularly large impact on the Yala Glacier.The Chhota Shigri,Djankuat,and Hamaguri Yuki glaciers displayed different states of mass balance due to the influence of climatic factors.This study pro-vides valuable insights into the comprehensive understanding of glacier change in Asia and its responses to climate change.展开更多
Glacier mass balance is a key indicator of glacier health and climate change sensitivity.Influencing factors include both climatic and nonclimatic elements,forming a complex set of drivers.There is a lack of quantitat...Glacier mass balance is a key indicator of glacier health and climate change sensitivity.Influencing factors include both climatic and nonclimatic elements,forming a complex set of drivers.There is a lack of quantitative analysis of these composite factors,particularly in climate-typical regions like the Tanggula Mountains on the central Tibetan Plateau.We collected data on various factors affecting glacier mass balance from 2000 to 2020,including climate variables,topographic variables,geometric parameters,and glacier dynamics.We utilized linear regression models,ensemble learning models,and Open Global Glacier Model(OGGM)to analyze glacier mass balance changes in the Tanggula Mountains.Results indicate that linear models explain 58%of the variance in glacier mass balance,with seasonal temperature and precipitation having significant impacts.Our findings show that ensemble learning models made the explanations 5.2%more accurate by including the impact of topographic and geometric factors such as the average glacier height,the slope of the glacier tongue,the speed of the ice flow,and the area of the glacier.Interpretable machine learning identified the spatial distribution of positive and negative impacts of these characteristics and the interaction between glacier topography and ice dynamics.Finally,we predicted the responses of glaciers of different sizes to future climate change based on the results of interpretable machine learning.It was found that relatively large glaciers(>1 km~2)are likely to persist until the end of this century under low emission scenarios,whereas small glaciers(<1 km~2)are expected to nearly disappear by 2080 under any emission scenario.Our research provides technical support for improving glacier change modeling and protection on the Tibetan Plateau.展开更多
Carbon fluxes are essential indicators assessing vegetation carbon cycle functions.However,the extent and mechanisms by which climate change and human activities influence the spatiotemporal dynamics of carbon fluxes ...Carbon fluxes are essential indicators assessing vegetation carbon cycle functions.However,the extent and mechanisms by which climate change and human activities influence the spatiotemporal dynamics of carbon fluxes in arid oasis and non-oasis area remains unclear.Here,we assessed and predicted the future effects of climate change and human activities on carbon fluxes in the Hexi Corridor.The results showed that the annual average gross primary productivity(GPP),net ecosystem productivity(NEP),and ecosystem respiration(Reco)in the Hexi Corridor oasis increased by 263.91 g C·m^(-2)·yr^(-1),118.45 g C·m^(-2)·yr^(-1)and 122.46 g C·m^(-2)·yr^(-1),respectively,due to the expansion of the oasis area by 3424.84 km^(2) caused by human activities from 2000 to 2022.Both oasis and non-oasis arid ecosystems in the Hexi Corridor acted as carbon sinks.Compared to the non-oasis area,the carbon fluxes contributions of oasis area increased,ranging from 10.21%to 13.99%for GPP,8.50%to11.68%for NEP,and 13.34%to 17.13%for Reco.The contribution of the carbon flux from the oasis expansion area to the total carbon flux change in the Hexi Corridor was 30.96%(7.09 Tg C yr^(-1))for GPP,29.57%(3.39 Tg C yr^(-1))for NEP and 32.40%(3.58 Tg C yr^(-1))for Reco.The changes in carbon fluxes in the oasis area were mainly attributed to human activities(oasis expansion)and temperature,whereas non-oasis area was mainly due to climate factors.Moreover,the future increasing trends were observed for GPP(64.99%),NEP(66.29%)and Reco(82.08%)in the Hexi Corridor.This study provides new insights into the regulatory mechanisms of carbon cycle in the arid oasis and non-oasis area.展开更多
基金supported by the National Key Research and Development Program of China(Grant No.2018YFC0809605,2018YFC0809600)the Key Research Program of Frontier Sciences of Chinese Academy of Sciences(Grant No.QYZDY-SSWDQC015)+2 种基金the National Natural Science Foundation of China(Grant No.41230630)the National Science Fund for Distinguished Young Scholars(Grant No.41825015)the Key Research Program of the Chinese Academy of Sciences(Grant No.ZDRW-ZS-2020-1)。
文摘The instability of soil bank slopes induced by freeze-thaw cycles at the northern foot of Tianshan Mountain is very common.The failure not only caused a large amount of soil erosion,but also led to serious reservoir sedimentation and water quality degradation,which exerted a lot of adverse effects on agricultural production in the local irrigation areas.Based on field investigations on dozens of irrigation reservoirs there,laboratory tests were carried out to quantitatively analyze the freeze-thaw effect on the soil engineering characteristics to reveal the facilitation on the bank slope instability.The results show that the softening characteristics of the stressstrain curves gradually weaken,the effective cohesions decline exponentially,the seepage coefficients enlarge,and the thermal conductivities decrease after 7 freeze-thaw cycles.The freeze-thaw effect on the specimens with low confining pressures,low dry densities and high water contents is more significant.The water migration and the phase transition between water and ice result in the variations of the soil internal microstructures,which is the main factor affecting the soil engineering characteristics.Sufficient water supply and the alternation of positive and negative temperatures at the reservoir bank slopes in cold regions make the water migration and phase transition in the soil very intensely.It is easy to form a large number of pores and micro cracks in the soil freezing and thawing areas.The volume changes of the soil and the water migration are difficult to reach a dynamic balance in the open system.Long-term freeze-thaw cycles will bring out the fragmentation of the soil particles,resulting in that the micro cracks on the soil surfaces are developing continuously.The soil of the bank slopes will fall or collapse when these cracks penetrate,which often happens in winter there.
基金the financial support from the National Natural Science Foundation of China(Nos.42471155,U2004181,and 41371092)partially supported by the Natural Science Foundation of Heilongjiang Province,China(No.LH2024D025)+2 种基金the Scientific Research Foundation for the Returned Overseas Chinese Scholars,State Education Ministry,China(No.SKLFSE201917)the Key Scientific and Technological Project of Henan Province,China(No.192102310503)the National Key Scientific and Technological Project of Henan Province Office of Education,China(No.14B170007)。
文摘The contact between contaminant and washing solution is a fundamental factor that limits the contaminant removal efficiency of chemical washing.In this study,the magnetization technique was employed to improve the physicochemical properties of ethylene diamine tetraacetic acid(EDTA)solutions for the removal of lead(Pb)and cadmium(Cd)from a contaminated clayey soil.Furthermore,EDTA concentration,magnetization strength,and magnetization time were varied as parameters for enhancing the contact between contaminant and washing solution to improve remediation efficiency.The results showed that after magnetization,the viscosities,surface tensions,and contact angles of EDTA solutions decreased,whereas the electrical conductivity and pH increased.In particular,the viscosities of high-concentration EDTA solutions increased with increasing magnetic field strength and magnetization time.The magnetized EDTA solutions increased the maximum removal rates of Cd and Pb by 64.46% and 35.49%,respectively,compared to the unmagnetized EDTA solutions.The results highlighted the efficient metal removal by magnetized washing solutions due to the better contact between the washing solutions and the contaminants.The magnetic-enhanced soil washing method was proven to be efficient,cost-effective,and easily implementable for enhancing heavy metal removal.This study provides a valuable reference for improving the efficiency of chemical washing for heavy metal-contaminated clayey soils.
基金supported by the National Natural Science Foundation of China(Grant No.42325502,and 42275045)the West Light Foundation of the Chi-nese Academy of Sciences(Grant No.xbzg-zdsys-202215)+1 种基金the Sci-ence and Technology Research Plan of Gansu Province(Grant Nos.23JRRA654 and 20JR10RA070)iLEAPs(Integrated Land Ecosystem-Atmosphere Processes Study).
文摘The source region of the Yellow River(SRYR),with its semi-humid to semi-arid climate,is crucial for understanding water resource dynamics.Precipitation is key for replenishing surface water and balancing the ecosystem’s water cycle.However,the soil moisture response to precipitation across climate zones and soil layers remains poorly understood due to limited long-term data.This study examines the response of soil moisture to precipitation at multiple time scales in the SRYR,using data from Maqu,Mado,Ngoring Lake sites,and the Maqu monitoring network(MMN),along with CN05.1 precipitation and GLEAM v3.8a soil moisture data.Results show that the semi-humid area requires more precipitation to trigger soil moisture responses compared to the semi-arid area in the SRYR.Surface soil at Maqu,MMN,Ngoring Lake,and Mado sites require at least 8.6,8.4,5.2,and 2.84 mm of precipitation,respectively,for effective replenishment.Significant responses to precipitation events were observed in soil layers at 40 cm and above in the semi-humid area,while at 20 cm and above in the semi-arid area.Precipitation volume is the primary factor influencing soil moisture,affecting both the increment and time lag to maximum moisture.Precipitation intensity and pre-rain moisture have no direct effect.In the central SRYR,accumulated precipitation has a greater impact.Root-zone soil moisture has a weaker correlation with precipitation compared to surface soil moisture but persists longer,responding for up to 10 days,while surface soil moisture responds more immediately but only lasts about 5 days.
基金supported by the Open Fund of State Key Laboratory of Frozen Soil Engineering (Grant No.SKLFSE201806)the National Natural Science Foundation of China (Grant No.42177155).
文摘Sudden temperature drops cause soils in natural environments to freeze unidirectionally,resulting in soil expansion and deformation that can lead to damage to engineering structures.The impact of temperature-induced freezing on deformation and solute migration in saline soils,especially under extended freezing,is not well understood due to the lack of knowledge regarding the microscopic mechanisms involved.This study investigated the expansion,deformation,and water-salt migration in chlorinated saline soils,materials commonly used for canal foundations in cold and arid regions,under different roof temperatures and soil compaction levels through unidirectional freezing experiments.The microscopic structures of saline soils were observed using scanning electron microscopy(SEM)and optical microscopy.A quantitative analysis of the microstructural data was conducted before and after freezing to elucidate the microscopic mechanisms of water-salt migration and deformation.The results indicate that soil swelling is enhanced by elevated roof temperatures approaching the soil's freezing point and soil compaction,which prolongs the duration and accelerates the rate of water-salt migration.The unidirectional freezing altered the microstructure of saline soils due to the continuous temperature gradients,leading to four distinct zones:natural frozen zone,peak frozen zone,gradual frozen zone,and unfrozen zone,each exhibiting significant changes in pore types and fractal dimensions.Vacuum suction at the colder end of the soil structure facilitates the upward migration of salt and water,which subsequently undergoes crystallization.This process expands the internal pore structure and causes swelling.The findings provide a theoretical basis for understanding the evolution of soil microstructure in cold and arid regions and for the management of saline soil engineering.
基金supported by the Second Tibetan Plateau Scientific Expedition and Research Program(STEP)(No.2019QZKK0605)the National Natural Science Foundation of China(No.42201161)the Startup Foundation for Introducing Talent of NUIST(No.2022r024)。
文摘Since scarce knowledge of soil mercury(Hg)concentrations and risks in the vulnerable Xinjiang,topsoils(0-15 cm)from its typical landscapes were extensively sampled.Topsoil total mercury(THg)concentrations varied broadly between 0.9 and 35.3 ng/g,of which16.8%exceeded the background value of soil Hg for Xinjiang.Topsoil THg concentrations across various landscapes exhibited a declining order:farmland(11.7±6.0 ng/g)>grassland(10.5±8.5 ng/g)>woodland(10.2±8.2 ng/g)>desert(7.0±5.8 ng/g).The average topsoil THg concentration was higher in northwestern Xinjiang(11.3±7.2 ng/g)than that in southeastern Xinjiang(6.3±6.1 ng/g).Relatively high topsoil THg concentrations were observed near the cities with intensive human activities,followed by a gradual decline to the surroundings.The concentrations of topsoil THg were strongly correlated with the contents of total organic carbon(TOC),clay,silty,and sandy,and the distance from each sampling site to its nearest city,suggesting that the variation of topsoil Hg was significantly influenced by TOC content,soil granularity,and anthropogenic Hg emissions.Silty and TOC were the principal affecting factors,explaining 48.7%and 7.9%of the THg variation,respectively.The contamination and potential ecological risk evaluations revealed that topsoils in regions with dense populations were polluted with Hg and contained higher potential ecological risks.The health risk evaluations indicated that exposure risks of topsoil Hg were higher for children than those for adults.Fortunately,topsoil Hg posed acceptable risks to human health.
基金the financial support from the funding of the National Natural Science Foundation of China(NSFC)(Grant Nos.42401160 and U22A20596)the Science and Technology Plan Project of Linzhi(Grant No.SYQ2024-13).
文摘Due to the high water content in warm frozen soil,the pore water pressure and pore ice pressure generated within the sample during loading significantlyinfluencethe deformation and strength of the soil skeleton.Therefore,it is essential to develop a constitutive model for warm frozen soil that can capture the changes in ice pressure and water pressure.This study introduces a macro-meso constitutive model based on a binary-medium framework to describe the mechanical behavior of warm frozen soil.In this model,warm frozen soil is conceptualized as consisting of bonded and frictional elements from a meso perspective.The bonded elements are modeled using a macro-meso elastic constitutive approach based on poromechanics,while the frictional elements employ a macro-meso elastoplastic approach,also grounded in poromechanics.These two elements are then linked within the binarymedium model framework.By replicating the experimental curves of warm frozen soils,the theoretical results from the proposed model show excellent agreement with experimental data.This consistency indicates that the model effectively simulates the strain softening and volumetric expansion behaviors of warm frozen soil samples under various conditions.Additionally,the constitutive model predicts changes in unfrozen water pressure,frozen temperature,unfrozen water saturation,and porosity during the loading process of warm frozen soil samples.
基金supported by the National Natural Science Foundation of China(No.41471062,No.41971085,No.41971086)。
文摘Affected by climate warming and anthropogenic disturbances,the thermo-mechanical stability of warm and ice-rich frozen ground along the Qinghai-Tibet engineering corridor(QTEC)is continuously decreased,which may delay the construction of major projects in the future.In this study,based on chemical stabilization of warm and icerich frozen ground,the soil-cement column(SCC)for ground improvement was recommended to reinforce the foundations in warm and ice-rich permafrost regions.To explore the validity of countermeasures mentioned above,both the original foundation and the composite foundation consisting of SCC with soil temperature of-1.0℃were prepared in the laboratory,and then the plate loading tests were carried out.The laboratory investigations indicated that the bearing capacity of composite foundation consisting of SCC was higher than that of original foundation,and the total deformation of original foundation was greater than that of composite foundation,meaning that overall stability of foundation with warm and ice-rich frozen soil can be improved by SCC installation.Meanwhile,a numerical model considering the interface interaction between frozen soil and SCC was established for interpretating the bearing mechanism of composite foundation.The numerical investigations revealed that the SCC within composite foundation was responsible for the more applied load,and the applied load can be delivered to deeper zone in depth due to the SCC installation,which was favorable for improving the bearing characteristic of composite foundation.The investigations provide the valuable guideline for the choice of engineering supporting techniques to major projects within the QTEC.
基金supported by National Natural Science Funds of China(Nos.41771066,41825015)the Science and Technology Project of Yalong River Hydropower Development Company(No.LHKA-G201906)。
文摘The construction of water conservancy projects in cold regions experiences freezing-thawing cycles,which can greatly change the engineering properties of soil and have a significant impact on the construction of projects.Lianghekou Hydropower Station(LHS),is a controlling station with the largest installed capacity among the 7 middle reach projects in the Yalong River,the secondary tributary of the Yangtze River.LHS is located in a seasonally frozen soil area.Based on the measured data of air and ground temperature in winter in the dam core wall,the freezing-thawing variation of gravelly soil and contact clay during the filling process of the core wall are compared and analyzed,then the main impact factors of the freezing-thawing variation of soils are discussed.The results show that under the influence of air temperature,soil freezes unidirectionally from ground surface downward and deepens gradually,and the thawing processes are different at the aspects of thawing direction and rate.Air temperature and physical properties of soil including soil type,moisture content and dry density affect the freezingthawing processes of soils.And the impact of engineering construction is more remarkable than natural factors.The engineering construction affects soil temperature and freezing-thawing process by controlling the initial temperature of soil,the speed and duration of the technological conversion of paving,compaction,and the length of placed duration at night.Due to the long placed duration of soil with the slow construction method,the initial temperature of soil gradually reduces,the heat transfer process inside soil is fast.Then the internal heat of soil releases,the decreasing rate of ground temperature of soil at different depths is fast and the frozen depth deepens.While due to the short placed duration of soil with the rapid construction process,the initial temperature of soil is high,high internal heat of soil is supplied every day,and the heat transfer process inside soil is slow.Then the decreasing rate of temperature of soil at different depths is slow,and the variation amplitude of frozen depth is small.This study provides useful guidance for the freezingthawing prevention during the construction process of core wall dams located at high altitude region in winter.
基金financial support from the National Natural Science Foundation of China(42322105,42071082)Outstanding Youth Fund of Gansu Province(23JRRA612)。
文摘Microplastics(MPs)become ubiquitous in soil and are an environmental and public health concern worldwide.However,the status of MPs in natural and farmland soils in remote areas remains poorly understood.In this study,we investigated the characteristics of MPs in natural and farmland soils along two transects in the Qilian Mountains of the northern Tibetan Plateau.The average abundance of MPs in natural and farmland soils was 29,778 and 56,123 items kg^(-1),respectively,with a detection size range of 10-1000μm.MPs in the size range of 10-100μm accounted for 84.1%of particles detected.Among the 21 polymers detected,polyethylene dominated in both farmland and natural soils.The shape of MPs was dominated by fragments(95.8%),followed by fibers(3.8%)and beads(0.4%).The abundance of MPs was positively correlated with increasing altitude in natural soils.There was no significant correlation between the abundance of MPs and soil physicochemical properties due to the narrow range of values of soil physicochemical properties.With the growing concern regarding MPs pollution,research on the status of MPs in high altitude and remote areas is critical to understanding their global cycle.
基金supported by the National Natural Science Foundation of China (No. 41471062, No. 41971085, No. 41971086)。
文摘The warm and ice-rich frozen soil is characterized by high unfrozen water content, low shear strength and large compressibility, which is unreliable to meet the stability requirements of engineering infrastructures and foundations in permafrost regions. In this study, a novel approach for stabilizing the warm and ice-rich frozen soil with sulphoaluminate cement was proposed based on chemical stabilization. The mechanical behaviors of the stabilized soil, such as strength and stress-strain relationship, were investigated through a series of triaxial compression tests conducted at -1.0℃, and the mechanism of strength variations of the stabilized soil was also explained based on scanning electron microscope test. The investigations indicated that the strength of stabilized soil to resist failure has been improved, and the linear Mohr-Coulomb criteria can accurately reflect the shear strength of stabilized soil under various applied confining pressure. The increase in both curing age and cement mixing ratio were favorable to the growth of cohesion and internal friction angle. More importantly, the strength improvement mechanism of the stabilized soil is attributed to the formation of structural skeleton and the generation of cementitious hydration products within itself. Therefore, the investigations conducted in this study provide valuable references for chemical stabilization of warm and ice-rich frozen ground, thereby providing a basis for in-situ ground improvement for reinforcing warm and ice-rich permafrost foundations by soil-cement column installation.
基金supported by the Key Project of the Natural Science Foundation of China(No.41630636)the National Natural Science Foundation of China(No.41501072)+1 种基金the Independent Foundation of State Key Laboratory of Frozen Soil Engineering,China(No.SKLFSE-ZT-202107)the Natural Science Foundation of Gansu,China(No.22JR5RA057).
文摘The formation and growth of segregation ice dominate the frost heave during soil freezing,which is closely related to water migration.To analyze segregation ice during soil freezing for different soils,a freezing-thawing experiment was conducted with Lanzhou loess(LZL)and Qinghai-Tibet Plateau silty clay(QSC)using a novel layered nuclear magnetic resonance approach.During LZL freezing,the unfrozen water content first increased and then decreased with decreasing temperature near the freezing front,but decreased with decreasing temperature in other layers,whereas during the freezing of QSC,the unfrozen water content in different layers(including the freezing front)decreased with decreased temperature.Notably,the increased liquid water near the freezing front during LZL freezing was primarily adsorbed water.In addition to the temperature gradient,the squeezing action during soil freezing was another important factor affecting water migration,especially at the early stage of soil freezing.However,which of the two factors,squeezing action and temperature gradient,was the dominant one causing water migration depended on soil structure.At the early stage of soil freezing,the squeezing action had a significant effect on the water migration of LZL,but no significant effect on that of QSC.Furthermore,water accumulation of LZL near the freezing front due to squeezing action at the early stage of freezing limited the formation and growth of segregation ice.This study provided an improved understanding for ice segregation and water migration during soil freezing.
基金supported by Gansu Provincial Science and Technology Program(22ZD6FA005)"Light of the West"Cross-team Project of the Chinese Academy of Sciences(xbzgzdsys-202214)+1 种基金the National Natural Science Foundation of China(41871064)Qinghai Province High-level Innovative"Thousand Talents"Program.
文摘Soil microbial communities are pivotal in permafrost biogeochemical cycles,yet the variations of abundant and rare microbial taxa and their impacts on greenhouse gas emissions in different seasons,remain elusive,especially in the case of soil archaea.Here,we conducted a study on soil abundant and rare archaeal taxa during the growing and non-growing seasons in the active layer of alpine permafrost in the Qinghai-Tibetan Plateau.The results suggested that,for the archaeal communities in the sub-layer,abundant taxa exhibited higher diversity,while rare taxa maintained a more stable composition from the growing to non-growing season.Water soluble organic carbon and soil porosity were the most significant environmental variables affecting the compositions of abundant and rare taxa,respectively.Stochastic and deterministic processes dominated the assemblies of rare and abundant taxa,respectively.The archaeal ecological network influenced N_(2)O flux through different modules.Rare taxa performed an essential role in stabilizing the network and exerting important effects on N_(2)O flux.Our study provides a pioneering and comprehensive investigation aimed at unravelling the mechanisms by which archaea or other microorganisms influence greenhouse gas emissions in the alpine permafrost.
基金financially supported in part by the Second Tibetan Plateau Scientific Expedition and Research Program(STEP)(2021QZKK0205)the National Natural Science Foundation of China(42230512).
文摘The thawing and warming of ice-rich permafrost present a considerable threat to the long-term stability of the Qinghai-Xizang Railway(QXR)on the roof of the world—that is,the Qinghai-Xizang Plateau(QXP).In this review,we explore the extent of the observed permafrost degradation and embankment damage under the coupled impacts of climate change and engineering construction.The ice-rich permafrost beneath the embankment presents a substantial threat to the thermal-mechanical stability of the embankment due to the permafrost’s accelerated and amplified degradation.The observed embankment deformation has a potential high risk of thaw settlement,especially for 656 embankment-bridge sections,whose potential high risk of thaw settlement may be as great as 25%.Several techniques for roadbed cooling can be used to alleviate these impacts,including crushed rock structure embankments(CRSEs),thermosyphons,and reinforcement measures,which have been demonstrated to be successful in cooling the underlying permafrost and stabilizing an embankment.Under future climate change and permafrost degradation,however,the QXR still faces a high risk of embankment damage caused by permafrost degradation and requires more effective methods to reinforce the thermal-mechanical stability of permafrost.Therefore,a better understanding of such high-risk regions is needed,and roadbed cooling techniques will require further adaption in order to address the issues brought by climate change.
基金funded by the Science and Technology program of Gansu Province(Grant No.23ZDFA017)Longyuan Young Talents(D.Luo),Western Young Scholars Project of the Chinese Academy of Sciences(D.Luo)National Natural Science Foundation of China(U2243214).
文摘Permafrost,a critical component of Earth’s climate system,is increasingly subject to abrupt thaw events,which jeopardize infrastructure,reshape landforms,alter hydrological regimes,and disrupt ecosystems,thereby posing substantial threats to global sustainability.However,the underlying mechanisms that trigger these abrupt transitions remain incompletely understood.Here,we present decade-long in-situ observations from HRQ1,a marginal permafrost site in the Headwater Area of the Yellow River,northeastern Qinghai-Xizang Plateau.These data reveal the formation and growth of a talik,indicative of a permafrost tipping point.Absent before 2017,the talik subsequently formed and progressively deepened,extending to the maximum observation depth of 300 cm by 2024.The transition from perennially frozen to thawed conditions was accompanied by a substantial increase in mean annual soil temperature(MAST)throughout the entire soil profile.From 2015 to 2023,MAST in the upper 200 cm rose from sub-zero(−0.30 to−0.49℃)to consistently above 0℃(0.07 to 1.08℃).Concurrently,maximum daily soil temperatures in deeper layers(200–300 cm)became positive,indicating thaw propagation into the relict permafrost.This warming coincided with a marked increase in unfrozen soil moisture,particularly within the expanding talik.The rapid,non-linear deepening of the talik,far exceeding rates attributable to conductive heat transfer alone,was driven by a strong convective mechanism(Rayleigh-Darcy instability).This advective process was triggered when the soil profile became fully saturated,a condition resulting from the convergence of intensified rainfall and enhanced water retention linked to decadal vegetation greening.Intriguingly,despite the accelerated subsurface warming,the annual amplitude of ground surface temperature decreased from 29.0±2.8℃ to 24.5±3.6℃ following talik formation,likely due to the buffering effect of increased vegetation cover,which modified the surface energy balance.Our results demonstrate that climatic warming and wetting can initiate a cascade of internal feedbacks,propelling marginal permafrost beyond an abrupt tipping point.These findings emphasize the acute vulnerability of marginal permafrost and highlight the urgent necessity for sustained monitoring to assess ecosystem stability and quantify associated greenhouse gas emissions.
基金supported by the National Key R&D Program of China(2022YFC2903903)the National Natural Science Foundation of China(42271153,42471164)+2 种基金Western light project of Chinese Academy of Sciences of China(xbzg-zdsys-202311)The Science and Technology program of Gansu Province(23ZDFA017)Natural Science Foundation of Gansu province of China(24JRRA102)。
文摘The strength characteristics of ice materials are crucial for the analysis of the interaction between ice and structure in ocean engineering and ice engineering.In this investigation,six machine learning methods were utilized to predict the strength of the envelope surface of ice materials.The database for the ice strength was first established by collecting 1,481 testing data reported in the previous literatures.A quadric strength criterion was adopted to describe failure behaviors of ice materials under different conditions of material property and laboratory.Three model parameters in this strength criterion were forecasted by using six machine learning methods.The prediction capacities of six machine learning methods were evaluated by three statics indices,and the integrated simulation ability of six machine learning methods was arranged.Three machine learning algorithms were selected to be improved and optimized,and the simulation capacity of the three algorithms was further explored.The optimization results indicate that the improved potential of the Ensemble algorithm is much higher than that of the SVM algorithm and the GPR algorithm for predicting the ice strength.
基金supported by the National Natural Science Foundation of China(42322105)Outstanding Youth Fund of Gansu Province(23JRRA612)Postdoctoral Fellowship Program of CPSF(GZC20232952).
文摘Microplastics have emerged as one of the most significant threats to the Earth's ecosystems due to their persistence,ability to carry high loads of contaminants,and biotoxicity.The Tibetan Plateau is a hotspot for global biodiversity conservation,but its ecosystem is fragile.This study systematically investigated the characteristics,distribution,sources,and ecological risk of microplastics in rivers and lakes across the Tibetan Plateau using the Laser Direct Infrared Imaging Spectroscopy(LDIR).The results indicated that the mean abundances of microplastics in water and sediments were 4250 items/m^(3)(n=50)and 3750 items/kg(n=44),respectively.Microplastics with small sizes(50-200μm),characterized by transparent and white fragments,were predominant.The most common polymers identified were polyamide(PA),polyurethane(PU),polyethylene terephthalate(PET),polyvinyl chloride(PVC),polypropylene(PP),and polyethylene(PE).Water sampling sites near urban/suburban effluent outfalls showed high levels of contamination.Microplastics in water are primarily derived from sewage effluent and atmospheric deposition.No single driver has been identified as the key factor influencing the spatial distribution of microplastics in water.The abundance of microplastics in sediments was significantly negatively correlated with the distance to the nearest city/town(p<0.01,R=-0.56)and significantly positively correlated with precipitation(p<0.01,R=0.60).Discarded or landfilled plastic waste is a major source of microplastics in sediments,which accumulate through transport by stormwater runoff caused by precipitation.Three ecological risk assessment models for microplastics were applied,and the high proportion of hazardous polymers such as PU,PVC,and PA was found to be responsible for the high ecological risk in the study area.This study provides an accurate and detailed exploration of the characteristics,sources,and spatial distribution of microplastic pollution by advanced automatic detection method in rivers and lakes on the Tibetan Plateau.
基金supported by China-Pakistan joint program of the Chi-nese Academy of Sciences(Grant No.046GJHZ2023069MI)National Natural Science Foundation of China(Grant No.42371145)the program of the Key Laboratory of Cryospheric Science and Frozen Soil Engineering,CAS(Grant No.CSFSE-ZZ-2402).
文摘Snowmelt runoffis an important component of water resources in the Northwest China(NWC).With global cli-mate warming and the increasing frequency of extreme events,snowmelt floods have caused significant damage.However,current studies lack comprehensive research and systematic risk assessments of snowmelt floods across the NWC.Based on the snowmelt runoffsimulated by GLDAS-NOAH model(1948-2022),the multiple indicators of snowmelt floods were retrieved by Peaks Over Threshold(POT)model in the NWC,and comprehensive risk assessment was conducted by integrating socio-economic data.The results indicated that the snowmelt runoffin the NWC shows a significant increasing trend and exhibits a spatial pattern of being more abundant in the northwest and southwest edges while less in the central and eastern regions.In Northern Xinjiang,snowmelt floods occurred relatively infrequently but with large magnitudes,while around the Qilian Mountains,snowmelt floods were more frequent but of smaller magnitudes.The longest duration of snowmelt floods was observed in the Kashgar and Yarkant River.Basins near mountainous areas are prone to snowmelt floods,especially the Tongtian and Lancang River basins,as well as the Ebinur Lake,Ili River basin,and the rivers south of the Altai Mountains,which face the highest risk of snowmelt floods.Based on comprehensive assessment of hazard,expo-sure,vulnerability and adaptability,high and very high-risk areas account for 15.5%of the NWC.It is urgent to enhance monitoring,early warning systems,and implement corresponding disaster prevention and mitigation measures in large mountainous basins.
基金supported by the National Key Research and Devel-opment Program of China(2023YFC3206300)the National Natural Science Foundation of China(42477529)the Gansu Provincial Science and Technology Program(22ZD6FA005).
文摘Under global warming,Asian glaciers have experienced accelerated retreats and increased mass loss.Utilizing data from the World Glacier Monitoring Service(WGMS),this study selected 16 representative glaciers across Asia to analyse the temporal and spatial changes of glacial mass balance(GMB),equilibrium line altitude(ELA),and accumulation area ratio(AAR)in the past several decades.Based on structural equation modelling and correlation analysis,we evaluated the responses of glacier change to climate change.The results indicated that 14 glaciers experienced mass loss,with the Parlung No.94 Glacier exhibiting a severe loss and significant retreat.In contrast,the Abramov,Muztag Ata No.15,Chhota Shigri,and Yala glaciers showed an increase in GMB,consistent with the"Karakoram Glacier anomaly".Additionally,a latitudinal gradient was observed,with ELA decreasing,AAR rising,and the rate and magnitude of glacier mass loss decreasing as latitude increased.GMB was negatively correlated with ELA and positively correlated with AAR,with the Vodopaniy No.125 Glacier showing the highest sensitivity to GMB variations.GMB fluctuation is influenced by energy(surface net solar radiation,air temperature)and precipitation.The significant decline of the Parlung No.94 Glacier was ascribed to rising temperature.From west to east in the Himalayas,the negative effects of energy on GMB decreased,with positive precipitation having a particularly large impact on the Yala Glacier.The Chhota Shigri,Djankuat,and Hamaguri Yuki glaciers displayed different states of mass balance due to the influence of climatic factors.This study pro-vides valuable insights into the comprehensive understanding of glacier change in Asia and its responses to climate change.
基金funding from the National Key Research and Development Program of China(2023YFC3206300)the Gansu Provincial Science and Technology Program(22ZD6FA005)+2 种基金the Gansu Youth Science and Technology Fund(E4310103)the Gansu Postdoctoral Science Foundation(E339880112)the Tibet Science and Technology Program(XZ202301ZY0001G and XZ202401JD0007)。
文摘Glacier mass balance is a key indicator of glacier health and climate change sensitivity.Influencing factors include both climatic and nonclimatic elements,forming a complex set of drivers.There is a lack of quantitative analysis of these composite factors,particularly in climate-typical regions like the Tanggula Mountains on the central Tibetan Plateau.We collected data on various factors affecting glacier mass balance from 2000 to 2020,including climate variables,topographic variables,geometric parameters,and glacier dynamics.We utilized linear regression models,ensemble learning models,and Open Global Glacier Model(OGGM)to analyze glacier mass balance changes in the Tanggula Mountains.Results indicate that linear models explain 58%of the variance in glacier mass balance,with seasonal temperature and precipitation having significant impacts.Our findings show that ensemble learning models made the explanations 5.2%more accurate by including the impact of topographic and geometric factors such as the average glacier height,the slope of the glacier tongue,the speed of the ice flow,and the area of the glacier.Interpretable machine learning identified the spatial distribution of positive and negative impacts of these characteristics and the interaction between glacier topography and ice dynamics.Finally,we predicted the responses of glaciers of different sizes to future climate change based on the results of interpretable machine learning.It was found that relatively large glaciers(>1 km~2)are likely to persist until the end of this century under low emission scenarios,whereas small glaciers(<1 km~2)are expected to nearly disappear by 2080 under any emission scenario.Our research provides technical support for improving glacier change modeling and protection on the Tibetan Plateau.
基金The Foundation for Distinguished Young Scholars of Gansu Province,No.22JR5RA046Key Research Program of Gansu Province,No.23ZDKA0004+2 种基金The Joint Funds of the National Natural Science Foundation of China,No.U22A202690Interdisciplinary Youth Team Project from the Key Laboratory of Cryospheric Science and Frozen Soil Engineering,No.CSFSE-ZQ-2408The Youth Innovation Promotion Association CAS to X.W.,No.2020422。
文摘Carbon fluxes are essential indicators assessing vegetation carbon cycle functions.However,the extent and mechanisms by which climate change and human activities influence the spatiotemporal dynamics of carbon fluxes in arid oasis and non-oasis area remains unclear.Here,we assessed and predicted the future effects of climate change and human activities on carbon fluxes in the Hexi Corridor.The results showed that the annual average gross primary productivity(GPP),net ecosystem productivity(NEP),and ecosystem respiration(Reco)in the Hexi Corridor oasis increased by 263.91 g C·m^(-2)·yr^(-1),118.45 g C·m^(-2)·yr^(-1)and 122.46 g C·m^(-2)·yr^(-1),respectively,due to the expansion of the oasis area by 3424.84 km^(2) caused by human activities from 2000 to 2022.Both oasis and non-oasis arid ecosystems in the Hexi Corridor acted as carbon sinks.Compared to the non-oasis area,the carbon fluxes contributions of oasis area increased,ranging from 10.21%to 13.99%for GPP,8.50%to11.68%for NEP,and 13.34%to 17.13%for Reco.The contribution of the carbon flux from the oasis expansion area to the total carbon flux change in the Hexi Corridor was 30.96%(7.09 Tg C yr^(-1))for GPP,29.57%(3.39 Tg C yr^(-1))for NEP and 32.40%(3.58 Tg C yr^(-1))for Reco.The changes in carbon fluxes in the oasis area were mainly attributed to human activities(oasis expansion)and temperature,whereas non-oasis area was mainly due to climate factors.Moreover,the future increasing trends were observed for GPP(64.99%),NEP(66.29%)and Reco(82.08%)in the Hexi Corridor.This study provides new insights into the regulatory mechanisms of carbon cycle in the arid oasis and non-oasis area.
