Abstract:During the Last Glacial Period,global climate fluctuated frequently,profoundly shaping the evolution and migratory histories of mammals.The abundant geological and biological records preserved within the Hanzhong Tiankeng Group provide invaluable resources for reconstructing past climates and environments.Tianxingyan shaft is situated in Ganhegou Village,Xiaonanhai town,Nanzheng district,Hanzhong city.It is one of the largest and most complete shafts within the Xiaonanhai Tiankeng Group.It is a spectacular 82-m-deep collapse feature,elevated at 932 meters above sea level.Tianxingyan shaft opens through limestones of the Late Permian Wujiaping Formation,which dip gently to southeast and are rhythmically bedded with layers measuring 30-40 cm,with some layers being 5-8 cm.A small rock-shelter excavated 26 m below the rim on the eastern wall yielded a fragmentary left second lower molar of Stegodon orientalis as described by Li et al.(2021).The specimen preserves only five lophids along a crown length of 80 mm,a width of 85 mm,and a height of 40 mm,resulting in a lophid frequency of 3.7.The enamel is thin(≈3 mm),strongly folded,and the valleys are densely packed with cement-morphometric features that align unambiguously with S.orientalis specimens from Panxian Dadong,Chongzuo Hejiang,and other classic Late Pleistocene cave sites in South China. To determine the absolute age of this northernmost record,we applied two independent techniques to the same individual.U-series dating was conducted on both enamel and a thin micritic carbonate rind adhering to the fossil surface.Enamel chips(TXYF-01-A,-B)were micro-drilled,spiked with a 229Th-233U-236U tracer,and analyzed on a Neptune Plus MC-ICP-MS at Xi'an Jiaotong University,following the protocols of Cheng et al.(2013).The high U contents(50-60 ppm)and elevated 230Th/232Thinitial ratios(≈8×10-6)yielded two precise apparent ages of 24.0±0.4 kyr and 14.2±0.1 kyr(2σ),but diagenetic uptake of U renders these minima.A third analysis of the surface carbonate(TXYF3-2)produced 32.3±1.6 kyr(uncorrected)and 22.1±14.5 kyr after detrital Th correction;the large uncertainty stems from low 230Th/232Th and underscores the difficulty of dating thin vadose precipitates. To circumvent open-system behavior,we turned to enamel AMS 14C.After removing the outer 2 mm,the remaining enamel powder was subjected to 2％NaClO(48 h)and 1 M acetic acid(24 h)to eliminate organics and secondary carbonates.CO2 was extracted by H3PO4 digestion,graphitised,and measured at the Xi'an AMS Centre on a 3 MV tandem accelerator.The raw 14C activity(5.54±0.09 pMC,δ13C=-17.23 ‰)translates to a calibrated age of 27 501±130 cal yr BP(IntCal20,median probability).Because enamel is virtually collagen-free,this result is considered robust against contamination from exogenous carbon.Bayesian integration of the three chronometers-allowing for U-uptake bias-estimates the death of the animal to 27.5+1.2/-0.9 kyr BP,coinciding with the Greenland Interstadial 3(DO 3)warm event within MIS 3. At the regional scale,this age aligns with a pronounced negative δ18O excursion recorded in the Didonghe stalagmite 25 km to the west and mirrored by contemporaneous speleothem minima in Yangzi,Furong,Hulu and Qingtian caves.Palynological spectra from the Hanzhong Basin register a synchronous expansion of temperate-subtropical deciduous broad-leaf forest(Quercus,Ulmus,Betula),indicating mean annual temperatures 2-3℃ higher and precipitation 15％-20％greater than today.Such conditions created a dense C3 forest-wetland mosaic ideal for a specialized browser. Stable-carbon isotope studies of coeval Stegodon orientalis populations across South China yield a narrow δ13C range centered about-16 ‰(-16.7 ‰ to-14.7 ‰),confirming strict C3 folivory.In contrast,the sympatric Asian elephant(Elephas maximus)displays a broader isotopic envelope(-17.9 ‰ to-11.9 ‰),reflecting flexible mixed feeding that includes C4 grasses.We argue that this dietary specialization made S.orientalis particularly vulnerable when monsoon strength waned after 27 kyr BP.Heinrich Stadial 3 and subsequent stadials caused rapid forest fragmentation and southward displacement of subtropical biomes.By the Last Glacial Maximum(LGM),the combined effects of extreme cold(mean annual temperature below 6 ℃)and aridity exceeded the physiological tolerance of these species,leading to regional extinction north of the Yangtze River.Elephas maximus,with its broader ecological niche and smaller body mass,survived in refugial pockets in Yunnan and Guangxi. The Tianxingyan record thus captures a brief,climate-driven range expansion of Stegodon orientalis into the northern subtropics during a DO warm pulse-a pattern consistent with the final south-to-north dispersal episode proposed for Chinese stegodontids.By integrating precise geochronology with high-resolution palaeoclimate archives,this study demonstrates that millennial-scale variability,rather than long-term orbital forcing,determined the ultimate fate of this emblematic Pleistocene megafauna.

Abstract:Terrestrial ecosystems,as a core component of the global carbon cycle,play a crucial role in carbon source/sink dynamics,which are significant for mitigating climate change and formulating strategies on sustainable development.Karst ecosystems,characterized by unique geological features such as carbonate rock dissolution,shallow soil,and high ecological fragility,exhibit distinct carbon sequestration mechanisms compared to non-karst regions.The southwest region of China boasts the world's largest contiguous karst area.Through rock weathering and vegetation restoration,the regional carbon sink capacity has been significantly enhanced.However,its carbon cycle is vulnerable to climate fluctuations and human activities.Although existing studies have focused on the carbon sink effect of karst ecosystems,the long-term spatiotemporal comparative analysis of carbon sources/sinks in karst and non-karst regions is still insufficient,and the influence mechanism of climate factors on carbon fluxes has not yet been fully clarified.In addition,the climate conditions associated with cloudy and rainy weather restrict the acquisition of traditional remote sensing data,thereby impeding the development of large-scale dynamic monitoring.Addressing these gaps is essential for optimizing ecological restoration strategies and advancing global carbon cycle models. Net Ecosystem Productivity(NEP),defined as the difference between Net Primary Productivity(NPP)and Heterotrophic respiration(Rh),serves as a key indicator for quantifying carbon sink/source dynamics.This study utilized the Google Earth Engine(GEE)platform and integrates MODIS MOD17A3HGF net primary productivity data,with a spatial resolution of 500 meters,spanning from 2003 to 2019,along with the ERA5-Land climate dataset,which included temperature and precipitation variables.The spatiotemporal evolution characteristics of vegetation carbon sources/sinks and their climatic driving factors in the karst and non-karst regions of Southwest China were systematically analyzed.All datasets were reprojected to the WGS_1984_UTM_Zone48N coordinate system and resampled to 500-meter resolution with the use of nearest-neighbor interpolation.The research methods include:(1)quantifying the carbon source/sink intensity through the NEP model,where soil Heterotrophic respiration(Rh)was estimated through an empirical formula incorporating temperature(T)and precipitation(R);(2)identifying the long-term trend of NEP by using Theil-Sen median slope estimation method and the Mann-Kendall significance test,and categorizing the results into nine significance levels;(3)analyzing the spatial heterogeneity of temperature and precipitation effects on NEP based on partial correlation analysis.Regions with p-values less than 0.05 were mapped to visualize spatial heterogeneity. The research findings show that:(1)From 2003 to 2019,the average annual NEP in the southwest region was 718.18 gC·m-2,showing a significant overall upward trend at a growth rate of 3.11 gC·(m-2·a)-1.Notably,the growth rate in the karst area was 4.27 gC·(m2·a)-1,significantly higher than the 2.76 gC·(m2·a)-1 observed in non-karst regions.(2)Carbon sink areas accounted for 99.994％of the total study area,while the carbon source areas(0.006％)were sparsely distributed,primarily in urbanized or high-altitude non-karst regions.(3)Spatially,NEP displayed a latitudinal gradient,decreasing from the tropical southern regions(e.g.,Yunnan,Guangxi)to temperate northern zones.High NEP values(1,152.5 gC·m-2 to 1,920.84 gC·m-2)were correlated with dense forests and favorable hydrothermal conditions,whereas low values(＜384.17 gC·m-2)were found in the alpine regions of Sichuan.Over 73％of the study area showed increasing NEP trends,concentrated in the Sichuan Basin and karst-dominated provinces such as Guizhou and Hunan.Declines(23.5％)were prominent in Xishuangbanna(Yunnan),where elevated temperatures intensified soil respiration.(4)Positive correlations between NEP and temperature dominated 86.89％of the regions,particularly in central karst zones where moderate warming enhanced photosynthesis.Negative correlations(13.11％)were localized in southern Yunnan,where excessive heat impaired enzymatic activity.Negative correlations prevailed in monsoon-dominated regions(e.g.,Guangdong,51.7％),where heavy rainfall exacerbated soil erosion and anthropogenic disturbances.Conversely,positive correlations(48.3％)occurred in arid karst hills(e.g.,Guangxi),where precipitation alleviated water stress. This study combines high-resolution remote sensing data with climate models to reveal the spatial differentiation of carbon sink functions and their climate-driven mechanisms in the karst regions of Southwest China.It provides a scientific basis for regional ecological restoration policies,such as the management of rocky desertification.The integration of GEE and MODIS data enabled high-resolution,long-term monitoring of carbon fluxes in ecologically fragile karst landscapes,overcoming traditional limitations posed by cloud-contaminated imagery.Further research indicates that moderate warming can enhance the productivity of karst vegetation,whereas extreme high temperatures or heavy precipitation may suppress the carbon sink capacity.Future studies should incorporate factors such as land-use change and human interference to comprehensively assess carbon management strategies for fragile ecosystems and provide references for carbon cycle research in comparable karst landform regions worldwide.

Abstract:Karst water is a significant water resource in the Pingliang region.Investigating the formation mechanism of karst water is crucial for the sustainable utilization of karst water resources,the protection of water sources,and the formulation of environmental protection measures in the area.Such studies provide a scientific basis and theoretical support for promoting the sustainable development of regional water resources and maintaining the health of the water environment.The hydrochemical composition of karst water can reveal the processes of recharge,runoff,and discharge,while isotopic tracing methods help delineate the extent and dynamic changes within the karst water system. To uncover the genesis mechanism of karst water in Pingliang City,we conducted a comprehensive analysis of its hydrochemical characteristics and sources using methods such as Piper trilinear diagrams,mathematical modeling,and ion ratio coefficients.The results indicate that the groundwater in the region can be mainly classified into two types:HCO3-Ca and HCO3·SO4-Na,with Ca2+and Na+as the dominant cations and HCO3-as the primary anion.The pH value ranges from 6.72 to 6.90,exhibiting overall weakly alkaline hydrochemical characteristics.Total Dissolved Solids(TDS)concentrations in the groundwater range from 158.01 mg·L-1 to 1,519.40 mg·L-1.Spearman correlation analysis shows that the hydrochemistry of karst water in the study area is primarily controlled by the dissolution of minerals such as dolomite and evaporites.TDS is highly positively correlated with the contents of Na+,Mg2+,Cl-,SO42-and HCO3-.Additionally,the content of Mg2+is significantly positively correlated with the contents of the main anions Cl-,SO42-and HCO3-(r＞0.70,p＜0.01),and the content of Na+also shows a significant positive correlation with the contents of Cl-and SO42-(r＞0.98,p＜0.01).In the analysis of ion proportional coefficients,the hydrochemical characteristics of karst water in Pingliang City are mainly influenced by rock weathering.Na+not only originates from the dissolution of rock salt,but may also come from the dissolution of sulfate or silicate minerals.Mg2+is derived from the combined action of calcite and dolomite.Ca2+is produced not only from the dissolution of dolomite but also from the dissolution of calcite and dolomite.During the rock weathering process,dolomite,calcite,and evaporites dominate the hydrochemical formation of karst water in Pingliang City.The Gibbs diagram combined with the analysis of mineral saturation indices further confirms that the dissolution of evaporites,carbonates,and silicate minerals is the natural source of hydrochemical components in Pingliang City.Ca2+,Mg2+and HCO3-in the karst groundwater of Pingliang City mainly originate from the combined dissolution of calcite and dolomite.Hydrogeological conditions and hydrogen-oxygen isotope analyses show that δD values range from-75.45 ‰ to-64.80 ‰,with an average of-69.20‰;while δ18O values range from-11.26‰ to-9.16‰,averaging-10.07‰.These results indicate that all groundwater is recharged by infiltration of atmospheric precipitation.Based on the identification of the gensis model for karst water,it has been determined that there are two genesis modes of karst water in the Pingliang region.Mode 1:Atmospheric precipitation infiltrates through the overlying Quaternary loess layer,continuously dissolving sulfate minerals within the loess,and enters the limestone confined aquifer through karst fissures formed by faults,eventually emerging as springs at the interface between the loess and limestone aquifer.In this mode,the chemical type of karst water is mainly HCO3·SO4-Na.Mode 2:Atmospheric precipitation infiltrates through the overlying Quaternary sandstone layer,continuously dissolving carbonate minerals in the sandstone layer,and enters the limestone confined aquifer through karst fissures formed by faults,eventually emerging as springs at the interface between the sandstone and limestone aquifers.In this mode,the chemical composition of karst water is mainly HCO3-Ca.Although both modes receive atmospheric precipitation recharge from the windward side of the mountain and enter the aquifer through karst fissures in the overlying strata,differences in these strata result in distinct hydrochemical characteristics.This indicates that the mineral dissolution in the overlying strata is the main factor influencing the hydrochemical composition of karst water in Pingliang.

Abstract:To actively address global climate change and achieve the strategic goals of carbon peak and carbon neutrality,Chinese geologists have recently confirmed from multiple perspectives that the potential of karst carbon sinks is substantial.Studying the factors influencing karst processes is fundamental to accurately quantifying the intensity of karst carbon sinks.This study took multiple karst springs within the same aquifer,characterized by similar land use but different elevations in the Lijiang Basin-the Jinshajiang karst area as the research objects.Based on hydrological and hydrochemical data,the mass concentration of CO2 consumed by carbonate rock weathering and the carbon sink flux at each level of the groundwater system were calculated by the hydrochemical-runoff method. The results show that climatic conditions are the main factors controlling karst carbon sink effects.The mass concentration of CO2 consumed by carbonate rock weathering is mainly influenced by temperature and is negatively correlated with altitude.In other words,the lower the altitude,the higher the mass concentration of CO2 consumed by carbonate rock weathering.Additionally,the rate of increase in the mass concentration of CO2 consumed by carbonate rock weathering tends to rise as altitude decreases.The carbon sink flux is mainly controlled by temperature and precipitation.In high-altitude mountainous regions where carbonate rocks are mainly affected by freeze-thaw weathering,the carbon sink flux is mainly controlled by precipitation and shows a positive correlation with altitude;that is,higher altitude receive greater precipitation,resulting in an increased carbon sink flux.Conversely,when carbonate rocks are primarily affected by chemical weathering,the carbon sink flux is mainly controlled by temperature and affected by precipitation,exhibiting a negative correlation with altitude.In this case,lower altitudes correspond to a greater carbon sink flux from carbonate rock weathering,with an increasing trend in magnitude.However,this change is less pronounced than the variation in the mass concentration of CO2 consumed by carbonate rock weathering,which decreases due to the reduction of precipitation.This indicates that the variations in altitude in a three-dimensional climate zone give rise to different climate types,such as precipitation form and amount,temperature,air pressure,evaporation,sunshine,etc.,thereby controlling the distribution of vegetation types and organisms,the intensity of weathering,and indirectly controlling the development and formation processes of karst and distribution of soil.Therefore,differences in altitude alter nearly all external environmental factors that control and affect karst development except for the hydraulic gradient.This results in the formation of diverse karst morphologies and distinct karst water system characteristics,which further amplify variations in karst features and carbon sink intensity.This is the main reason for the differences in karst and carbon sink intensity observed within the same area.The hydrological characteristics of karst water systems,along with vegetation and soil cover conditions,are important factors influencing the mass concentration of CO2 consumed by carbonate rock weathering and the carbon sink flux.These factors can even have a greater impact than climatic conditions.Therefore,human modifications of the external environment can change the intensity of karst carbon sinks,supporting strategic goals related to carbon peak and carbon neutrality.This study provides a geological basis for accurately assessing the intensity of karst carbon sinks,which is of great significance for understanding the global carbon cycle and advancing efforts toward carbon peak and carbon neutrality.

Abstract:Over the years,geological hazards such as collapses,landslides,hazardous rockfalls,and karst collapses have frequently occurred in Guangxi.These events are widely distributed,have prolonged impacts,affect large populations,and have caused heavy economic losses.Providing fundamental scientific knowledge for disaster prevention and mitigation in the region is of practical importance,as is conducting early prediction and risk assessment of geological hazards.The risk of geological hazards refers to the likelihood of a specific type and scale of hazard occurring within a defined area and time frame,influenced by certain triggering factors.Early prediction and risk assessment of geological hazards remain major challenges in disaster prevention and mitigation.Numerous factors influencing the risk assessment,and various evaluation methods have been employed. This study adopted Xiangzhou county in Guangxi as a case and employed an information modeling method based on an investigation of the main geological conditions controlling potential hazards.Based on the overlay analysis function of ArcGIS on spatial data,eight evaluation indicators were selected according to the characteristics of geological hazard development and potential risks in the study area.These indicators include landform type,geological structure,engineering geological rock group and terrain slope,degree of karst development,slope structure,vegetation coverage,and human engineering activities.The engineering geological rock group and terrain slope were taken as the main controlling factors,while the remaining factors served as secondary factors for overlay zoning.After the natural breakpoint method in statistics was used to reclassify the susceptibility zones,an evaluation grid based on the value of information was generated to assess the susceptibility of geological hazards.The susceptibility of geological hazards in Xiangzhou county is divided into four levels:low,medium,high,and extremely high susceptibility.Areas with extremely high and high susceptibility are mainly located in river terraces,peak forests,and valleys where underground karst development is intense,as well as in rocky mountainous regions,and areas with significant human engineering activities.Areas with medium and low susceptibility are mainly found in hilly and low-mountain terrain.On the basis of susceptibility assessment and the meteorological characteristics of the study area,the maximum 24-hour rainfall data for various return periods were collected from rainfall stations in Xiangzhou county and its surrounding areas.The Kriging method in AcrGIS was used to generate contour maps for rainfall events with return periods in 10,20,50,and 100 years.The maps for assessment of geological hazard susceptibility and contour maps for different rainfall conditions were normalized,and spatial overlay analysis was conducted to produce maps for risk assessment of geological hazards corresponding to different rainfall return periods,quantified by the value of information.The risk probabilities was divided into four categories-extremely high risk,high risk,medium risk,and low risk-with the use of the natural breakpoint method,resulting in risk assessments of geological hazards for varying rainfall return periods. The evaluation results indicate that as the return period of rainfall increases,the distribution area in which occur geological hazards with high and extremely high risks also expands.This result reflects that the impact of rainfall on geological hazards is significant.In Xiangzhou county,areas with extremely high geological hazard risk are mainly distributed in the central part near Sicun Town,characterized by river terrace landforms and rock formations with double-layer soil interbedded with sand gravel and clay.Additionally,extremely high-risk zones extend from the eastern Dale town to Baizhang town and to the western Maping town,where peak-forest valley landforms and hard limestone and dolomite rock formations characterized by karst intensely developed from the thick to blocky rocks are prevalent.The high-risk areas are mainly distributed in the hilly and river terrace landforms,including the northeast of Yunjiang Town,the area from Sicun Town to Dale and Baizhang Town,as well as the western part of Maping town.The remaining areas are mainly classified as medium-to low-risk zones,with hills and low mountains as the main geomorphic units.This study scientifically evaluates the geological hazard risks in Xiangzhou county,Guangxi,highlighting the key factors and adapting measures to local conditions.It categorizes different levels of geological hazard risks,and clarifies the zoning of these risks under different rainfall conditions.The findings provide a valuable reference for warning and forecasting geological hazards,improving the technical support system for hazard identification,zoning,and control in the study area.At the same time,the evaluation results can inform national spatial planning by guiding the population and economic activities to concentrate in low-risk areas in an orderly manner.

Abstract:At present,increasing human activities have brought about increasingly significant and severe adverse impacts on the sustainable development capacity of landscape areas in various karst regions around the world.In order to clarify the relationship between the Sustainable Development Capacity of Karst Landscape Areas(SDCKLA)and four influencing factors,including karst landscape,regional geology,regional natural environment,and human factors,this study combines a method of dynamic response with a systematic perspective.Based on an analysis of the composition of the SDCKLA and the main current situations and challenges these areas face,this study initially sorts out the complex dynamic response relationships,processes,and characteristics between SDCKLA and these four major influencing factors,concluding as follows: (1)The SDCKLA includes five major capabilities:development(quantity-target dimension),protection(protection dimension),sustainability(time dimension),resistance to interference(adaptability dimension),and health(quality dimension).These capabilities are measured through different specific indicators or characteristics,which collectively form a complex,dynamic,and variable system for the sustainable development capacity of karst landscape areas-similar yet distinct.(2)Karst landscapes are the resource prerequisite of the SDCKLA and serve as the common focus of other factors.The type and characteristics of karst landscapes-including their development,distribution,combinations,and six key attributes:aggregation,complexity,typicality,systematicness,completeness,and superiority-are fundamental in determining the strength of the SDCKLA.Additionally,the level,type,and area of karst landscapes exert a certain degree of influence on the strength of the SDCKLA.(3)Regional geological factors,comprising two sub-factors-regional strata(including distribution patterns,distribution area,lithology,burial,thickness,occurrence,solubility,degree of fragmentation,conditions of karst water occurrence,and water-bearing formations)and structure(including the type,intensity,and duration of tectonic movements,as well as faults,folds,joints,fractures,terrain,topography,and erosion base level)-provide an overall stable,consistent,yet distinct material foundation and inherent conditions for the SDCKLA.These factors control and influence the strength of the SDCKLA at both the material and structural levels.(4)Regional natural environment factors provide relatively brief but complex and varied external natural environment conditions with timely changes for the SDCKLA.①Water(including its types,hydrodynamic conditions,chemical characteristics,flow parameters,and water quality parameters,etc.)directly participates in the sustainable development process of karst landscape areas through hydrodynamic changes and directly controls and influences the strength of the SDCKLA.② Air(including CO2 content,exchange volume,pollution level,air quality index,etc.)and climate(including climate type,precipitation,temperature,climate stability,etc.)directly participate in the sustainable development process of landscape areas through the changes in CO2 content and their inherent characteristics,respectively,thereby affecting the strength of the SDCKLA.③ Soil(including soil type,CO2 content,thickness,aeration property,its utilization and contamination degree,etc.)and organisms(including plants,animals,microorganisms,their respective characteristics,rate of vegetation cover,biodiversity,etc.)indirectly participate in the process of sustainable development of landscape areas by changing soil CO2 content and metabolic behavior,respectively,thus influencing the strength of the SDCKLA.④ These five sub-factors are mutually integrated,complementary,and interactive.(5)Human factors encompass the specific decision-making and operational elements and serve as the central nerve of the SDCKLA.The SDCKLA is realized,maintained,and enhanced mainly through scientific research("think tank"),development and utilization("implementer"),protection("guardian"),and by changing the characteristics of other factors and their interrelationships("double-edged sword"),which may have favorable or unfavorable effects,and the ways and degrees of effects are closely and positively correlated with the manner and intensity of human activities. Based on the aforementioned research and by integrating the types,characteristics,relationships,and patterns of karst landscapes,this study discusses regulation techniques and measures to enhance the sustainable development capacity of point,linear,and areal landscapes.This approach follows the concept of"individual → local →whole",strengthening scientific research,formulating rational and evidenced-based plans,reducing geological disaster risks,implementing ecological restoration,optimizing the environmental,enhancing tourism appeal,scientifically regulating tourist numbers,conducting comprehensive regulation,establishing a monitoring systems,and developing a long-term operation and management system.These efforts aim to cultivate new high-quality productivity in karst tourism characterized by diverse types,distinctive features,and varied styles.

Abstract:Soil heavy metals in carbonate rock regions often exhibit natural high-background characteristics due to secondary enrichment during pedogenesis,posing potential risks to soil health,agricultural product safety,and ecological sustainability.Understanding the pollution patterns and sources of heavy metals in such high-background zones is critical for formulating targeted environmental protection strategies and safeguarding human health.This study focused on the carbonate rock region of central Shandong,a typical northern Chinese karst region dominated by Cambrian-Ordovician limestone and dolomite as parent rocks.A comprehensive investigation was conducted by collecting and analyzing samples of rock,surface soil,vertical soil profile,and atmospheric dustfall.Multiple analytical methods,including Enrichment Factor(EF)analysis,Principal Component Analysis(PCA),annual heavy metal increment simulation from dustfall,and Pearson correlation analysis,were employed to explore the pollution characteristics,sources,and influencing factors of soil heavy metals. Carbonate rock regions are globally significant for their unique pedogenic processes,where heavy metals undergo secondary enrichment due to intense chemical weathering and leaching of carbonate minerals.This natural enrichment,combined with potential anthropogenic inputs(e.g.,atmospheric dustfall),complicates the identification of heavy metal sources and their ecological impacts.Previous studies have primarily focused on single-medium(soil-only or rock-soil)analyses,lacking systematic multi-medium investigations.This study aimed to bridge this gap by integrating data on rock,soil,and atmospheric dustfall to comprehensively characterize the behavior of heavy metals in carbonate rock regions. The study area,located at the junction of the mountainous area in central Shandong and the northern Shandong plain,experiences a semi-humid continental monsoon climate characterized by distinct seasonal precipitation.Parent rocks are primarily carbonate(limestone and dolomite),with soil development dominated by chemical weathering.Soil samples were collected from natural woodlands and wilderness grasslands with minimal human disturbance.Rock samples were collected at the outcrop of bedrock.Atmospheric dustfall samples were collected over a one-year period of dry deposition.All samples were processed and analyzed in a certified laboratory,with heavy metal concentrations measured by Inductively Coupled Plasma Mass Spectrometry(ICP-MS),X-ray Fluorescence(XRF),and Atomic Fluorescence Spectrometry(AFS).Additionally,physicochemical properties,including pH,cation exchange capacity,and organic matter,were determined. The results show as follows:(1)The contents of soil heavy metals(Cu,Pb,Zn,Cr,Ni,As,Cd,and Hg)are 2.76 to 6.82 times higher than those in parent rocks.The contents of As,Cr,and Ni in atmospheric dustfall is lower than those in soil(enrichment coefficient between 0.47 and 0.65),while the contents of Cu,Pb,Zn,Hg,and Cd are higher(enrichment coefficient between 1.17 and 8.67),with Cd being the most significantly enriched.(2)The average pollution degree of soil heavy metals,ranked by EF values,is:Hg＞Cd＞Ni＞Cu＞As＞Zn＞Pb＞Cr.Most metals exhibit low pollution levels(EF＜2),except for minor Hg cases(EF＞5).Cr and Ni show negligible anthropogenic influence(all EF＜2),while Cd and Hg have relatively higher EF values,indicating potential external inputs.(3)Atmospheric dustfall contribute to the accumulation of soil heavy metals,with annual growth rates calculated as follows:Cd(0.55％),Hg(0.20％),Zn(0.16％),and Pb(0.09％).Cd and Hg,with the highest growth rates,were more significantly affected by dust deposition.(4)Soil Organic Matter(SOM)is strongly correlated with Cd and Hg(P＜0.01),showing similar vertical distribution patterns(surface accumulation).Cation Exchange Capacity(CEC)is significantly correlated with Cu,Pb,Zn,Cr,Ni,and As(P＜0.01),with stable vertical variations.These results indicate that Cd and Hg are primarily controlled by SOM and superimposed by dustfall inputs,while Cu,Pb,Zn,Cr,Ni,and As are mainly derived from parent rock weathering. This study provides a systematic multi-media(rock-soil-dustfall)analysis of heavy metal behavior in carbonate rock regions,emphasizing the combined effects of natural parent materials and anthropogenic dustfall.By integrating enrichment factor analysis,PCA,dustfall increment simulation,and correlation analysis,we identified the sources and controlling factors of soil heavy metals.These findings provide scientific support for strategies of evidence-based soil pollution control in similar carbonate rock regions,particularly prioritizing the management of Cd and Hg based on their higher accumulation rates and anthropogenic contributions.

Abstract:The study area is Xuanwei City,Qujing City,Yunnan Province,located in the southern section of the Wumeng Mountains on the central Yunnan-Guizhou Plateau.The overall landforms consist of deep-cut mid-mountain and low-mid-mountain terrain.The predominant tectonic line direction is NE-SW.The most widely exposed strata are the Permian Xuanwei Formation(P2xn)and the Emeishan Formation(P2β).The rock mass of the basement is soft and hard,with the rocks exhibiting weak weathering resistance and poor mechanical properties.Mining and quarrying represent the largest-scale human engineering activities in Xuanwei City,where coal mines are the most widely distributed,and goaf areas continue to expand.The main types of geological hazards include landslides,ground collapses,debris flows,and subsidence.These hazards are mainly small to medium in scale,with most currently stable or basically stable.To identify as many potential geological hazard points as possible and provide guidance for ground investigations,this study integrates conventional InSAR deformation data and optical images.By fully considering the development conditions and disaster-bearing elements of geological hazards,and establishing indicators related to susceptible environments and human activities,a set of comprehensive interpretation markers have been developed.This approach addresses the limitations of single-parameter interpretation methods,improves interpretation accuracy,and is applied effectively within the study area. A total of 88 geological disaster points were identified and interpreted.To evaluate the effectiveness of these interpretation markers,an entropy weight-fuzzy evaluation method was developed to evaluate their quality.The comprehensive recognition rate was 65％,with 17％classified as basically correct and 18％as incorrect.Field verification confirmed that 61 points were correct,seven were basically correct,and 20 were incorrect.This corresponds to a recognition accuracy of 69％,the basic accuracy was 8％,and an incorrect rate of 23％.The actual verification results align with the quality evaluation results obtained with the use of entropy weight-fuzzy comprehensive method.Among the points,35 were identified as existing geological hazards,and 33 were newly discovered geological hazards.Nineteen new points pose a threat to residents and are distributed across 13 townships,such as Baoshan,Dongshan,Longchang,and Tianba.A detailed list has been submitted to the Xuanwei Natural Resources Bureau to facilitate the implementation of appropriate prevention and control measures in the next phase. The susceptible environment forms the basis for the occurrence of geological disasters,serving as a target area and aggregation for identifying potential hazards.Markers for landslide-prone environments primarily consider slope structures dominated by consequent and oblique slopes.Collapses mainly occur on slopes above 45°,particularly those with reverse,transverse,or oblique slope structures,as well as slopes exhibiting joint development.For the beds of debris flow gullies,a slope gradient exceeding the threshold of 30‰ and a catchment area larger than 0.18 km2 are used as thresholds for interpreting markers of the water sources,while a total deposit volume greater than 5,000 m3 in the source area serves as the threshold for solid source markers.Karst collapses mainly involve carbonate strata,whereas goaf collapses are associated with coal-bearing strata and their direct overlying layers.A threshold of-20 mm·a-1 is applied to InSAR deformation to detect goaf collapses,supplemented by the boundary of mining rights and identification of the markers of mining activities.Markers of human activities are obtained from land survey data and optical remote sensing images.For roads and railways,attention is given to whether muck yard stockpiles are located in ditches,the presence of buildings and structures downstream and nearby,and the potential formation of chain disasters.The results show that the comprehensive interpretation markers established in Xuanwei City exhibit good quality and effectively identify potential geological hazards.

Abstract:Karst caves in Guangxi contain a large number of Quaternary vertebrate fossils;however,research on taxonomy and biostratigraphy remains insufficient.Therefore,more detailed reports on fossil assemblages are essential.Between 2014 and 2016,the excavation of two caves(Cave A and Cave B)in Maoshan,Lipu,northern Guangxi,yielded over 200 vertebrate fossils,of which 151 were identified in taxonomy.These animal fossils originated from two distinct sedimentary formations:calcareous nodules and sandy clay.For the fossils in the calcareous nodules,the uranium-series age of four mammal teeth was determined to be 211 to 158.8 ka BP.For the fossils in the sandy clay,the carbon-14 age of a deer tooth was established as 8590±30 BP,with a calibration of 9563 to 9521 cal BP;the uranium series age of five additional animal teeth was determined to be 7 to 4.7 ka BP.When the sedimental characteristics,as well as the carbon-14 and uranium-series dating results,are taken into the consideration,the Maoshan fossil remains can be classified into two groups:the Middle Pleistocene fauna and the Early Holocene fauna. Morphological analyses have shown that the Middle Pleistocene fauna of Maoshan includes nine taxa:Hystrix brachyura,Panthera tigris,Ailuropoda melanoleuca baconi,Arctonyx collaris,Rhinocerotidae gen.et sp.indet.,Sus scrofa,Muntiacus sp.,Cervus nippon,and Rusa unicolor.While there are no significant morphological differences between these fossils and their modern-day counterparts,the sizes of Malayan porcupines(Hystrix brachyura),tigers(Panthera tigris),and greater hog badgers(Arctonyx collaris)are significantly larger than those of their Holocene counterparts.This suggests that the forest habitat at that time was more developed than during the Holocene. The Maoshan Early Holocene fauna is comprised of 20 species,including Viperidae gen.et sp.indet.,Cuora sp.,Rhizomys sp.,Hystrix brachyura,Macaca sp.,Hylobatidae gen.et sp.indet.,Panthera tigris,Paguma larvata,Cuon alpinus,Nyctereutes procyonoides,Ailuropoda melanoleuca,Arctonyx collaris,Arctonyx albogularis,Rhinoceros sondaicus,Sus scrofa,Muntiacus reevesi,Muntiacus gigas,Cervus nippon,Rusa unicolor,and Bubalus sp.The fauna is dominated by cerviae,including a large number of primates and small carnivores,as well as a small population of rhinoceroses and buffaloes.This composition reflects an ecological environment dominated by forests and a significant extent of wetlands.Thus we can speculate that the climate at that time was relatively warm and humid. The Maoshan Early Holocene fauna consists almost entirely of extant species.Several Holocene faunas containing extinct members of the"Ailuropoda-Stegodon fauna"have been reported throughout southern China;however,their taxonomic identification or stratigraphic age remain uncertain.Available evidence suggests that the modern fauna of southern China originated in the Early Holocene and did not include any extinct species from the"Ailuropoda-Stegodon fauna". However,the Maoshan Early Holocene fauna contains a significant number of regionally extinct species,including giant pandas(Ailuropoda melanoleuca),greater hog badgers(Arctonyx collaris),Javan rhinos(Rhinoceros sondaicus),giant muntjacs(Muntiacus gigas),and wild buffalo(Bubalus sp.).These species underwent a gradual extinction from Guangxi after the Middle Holocene or were replaced by smaller related species.It reflects the profound ecological transformation caused by human activities,such as agricultural development and population growth.

Abstract:Southwest China is a typical karst development area,and the groundwater system is extremely complex,with a high degree of heterogeneity and complexity.The karst geological features in this area usually show a fissure-pore dual-media structure,and this geohydrological feature leads to the obvious nonlinear behavior of groundwater flow patterns.These special geological conditions not only pose significant challenges to the development and utilization of groundwater resources,but also complicate the accurate prediction of groundwater dynamics.In particular,when the tunnel construction is conducted in karst areas,it is easy to affect the groundwater flow field and produce water inrush disasters,which will have a far-reaching impact on the local groundwater resources,ecological environment,and even social and economic activities.Therefore,it is of great practical significance to study and understand the law of groundwater flow in karst areas and to accurately predict the amount of groundwater inflow and flow modes during tunnel construction,so as to ensure the safety of engineering construction,the protection of water resources,and the prevention of groundwater pollution. In this study,the MODFLOW-CFPv2 dual-media coupling model has been adopted.This model integrates two mechanisms-pipeline flow and matrix flow-enabling effective simulation of the complex water flow interaction between the fractured pipeline and the surrounding matrix in karst systems.The introduction of this model enables researchers to more accurately describe the laminar and turbulent flow characteristics in karst groundwater systems,and provides a powerful tool for in-depth understanding and simulation of the dynamics of karst groundwater.By integrating Gempy 3D geological modeling technology,this study further improves the fitting ability of the model to the complex geological structures of karst areas,thereby providing a more realistic depiction of groundwater flow characteristics within the tunnel area.During the simulation,key parameters,including the hydraulic conduction coefficient,recharge coefficient,pipeline size,and friction coefficient,have been calibrated through actual geological and hydrological data to ensure the accuracy and reliability of the model results. The main objective of this study is to quantitatively evaluate the water inflow and its influence on the groundwater flow field during tunnel construction in karst areas through numerical simulation,so as to provide theoretical support for the hydrological management of tunnel construction.In order to ensure the reliability of the simulation results,a large number of field monitoring data were used for model calibration.Specifically,the long-term monitoring data of borehole water level and spring flow were used as calibration objective functions to reflect the hydrological trend before and after tunnel construction.After calibration,the results showed that the Pearson correlation coefficient between the simulated water level and the measured water level is more than 0.98.This indicates that the model can accurately reflect the actual groundwater dynamics and provides a reliable basis for subsequent predictions. Simulation results revealed a significant variation in water inflow during tunnel construction.At the beginning of tunnel excavation,the predicted peak water inflow exceeded 20,000 m3·d-1 due to the drastic changes in the groundwater flow field caused by excavation,indicating a substantially increased risk of water inrush disasters.The simulation also showed that the drainage channel formed after the tunnel excavation caused a rapid drop in groundwater levels,far exceeding natural fluctuations.Even after the completion of the construction,groundwater levels had not returned to pre-excavation levels and remained approximately two meters lower,indicating a lasting impact of tunnel construction on the hydrological system.These findings provide important evidence for the hydrological management during tunnel construction,highlighting the need to consider the long-term effects of such projects on groundwater flow and water levels,especially in karst areas. Furthermore,this study revealed the profound impact of tunnel construction on groundwater flow and spring flow variations.As the tunnel excavation progresses,groundwater is rapidly discharged through karst pipelines,leading to significant changes in regional groundwater flow and spring discharge.The research findings indicate that during tunnel construction,groundwater flow is influenced not only by fissure flow but also interacted with matrix flow,further complicating the groundwater flow patterns.By analyzing the model results,researchers can more accurately identify the extent of the impact of tunnel construction on the groundwater flow field and propose corresponding hydrological management measures.

Abstract:This study adopted the stalagmite sample TK22-1 collected from Tiankeng Cave in Youyang Autonomous County,Chongqing,China,as the research object.A high-resolution δ18O sequence spanning the past century was reconstructed through a combination of high-precision 230Th dating and stalagmite laminae counting.This study reveals that the δ18O values of stalagmite TK22-1 exhibited a range of-6.03‰ to-7.29‰,with a mean value of-6.57‰.The positive shifts of δ18O(peaks)correspond well with recorded major drought events in the Sichuan-Chongqing region,such as the 2006 summer drought and the 1960 drought disaster.Correlation analyses show that δ18O variations exhibit a significant positive correlation with annual mean temperature but significant negative correlations with both annual mean humidity and the number of annual precipitation days.Although negatively correlated with total annual precipitation,this relationship does not reach statistical significance.Notably,the δ18O record closely corresponds to local drought events,indicating that regional hydrological conditions-such as temperature,the number of precipitation days,and humidity-are the dominant factors influencing stalagmite δ18O values. The nearly 100-year stalagmite δ18O time series shows distinct phases:δ18O remained consistently negative from 1900 to 1910,shifted to positive between 1910 and 1960,briefly decreased from 1960 to 1970,and have exhibited a consistently positive trend since 1970.Principal component analysis demonstrates that the positive δ18O trend in stalagmites from the Chinese monsoon region is spatially widespread,with a significant weakening observed after 1980.The observed weakening of the Asian Summer Monsoon(ASM)results from a combination of natural variability,such as 11-year solar cycles and Pacific Decadal Oscillation phase shifts,and anthropogenic forcing including greenhouse gases and aerosols.The primary driving mechanisms including ENSO regime transitions,weakening of Atlantic Meridional Overturning Circulation(AMOC)and Pacific Walker Circulation(PWC),and aerosol effects. This trend is significantly associated with global rise in temperature,an increased frequency of extreme ENSO events,and the weakening of both the AMOC and the PWC.Wavelet analysis identifies significant ENSO-related periodicities(2 years to 7 years)in the δ18O record.Between 1960 and 2000,the ENSO system progressively shifted toward El Niño-like states,with Central Pacific(CP)El Niño events suppressing monsoon intensity.The weakening of AMOC reduces land-sea thermal gradients,while the weakening of PWC alters zonal sea surface temperature gradients;together,these changes diminish monsoon dynamics.

Abstract:Rocky desertification is a significant constraint on socio-economic development and ecological construction in Southwest China.This study investigates the spatiotemporal evolution characteristics and future trends of rocky desertification in the Beipanjiang River Basin using the first,second,third,and fourth rocky desertification survey and monitoring datasets from the National Forestry and Grassland Administration.The Beipanjiang River,a major tributary of the Pearl River,originates in the Wumeng Mountains of Yunnan Province and traverses Guizhou Province.Characterized by significant topographical relief and extensive karst distribution,the Beipanjiang River Basin is a vital ecological functional area in Southwest China.This study aims to provide scientific support for regional ecological protection and rocky desertification control.Data from 2006 to 2022-including vegetation coverage,bare rock exposure rate,vegetation type,soil layer thickness,and rocky desertification degree-were analyzed with the use of"3S"technology(Remote Sensing,Geographic Information Systems,and Global Positioning Systems)alongside field surveys.The spatiotemporal evolution characteristics were assessed through dynamic analysis methods,and future trends were predicted with the use of the Markov model. Results show that from 2005 to 2021,vegetation coverage increased from 29.6％to 40.6％,the bare rock exposure rate decreased from 34.2％to 27.9％,and the proportion of rocky desertification land area shrank from 42.2％to 18.9％.Rocky desertification land was mainly concentrated in the middle and lower reaches,where areas experiencing moderate and severe rocky desertification accounted for over 35％of the karst area.Predictions indicate that by 2026 and 2031,the extent of moderately and severely desertified land will decrease by 241.53 km2 and 408.61 km2,respectively.Over the past 15 years,rocky desertification has been effectively controlled,although some areas still experience instability and face the risk of deterioration.Future efforts,supported by policy measures,are expected to further improve the situation,despite ongoing challenges in severely affected regions.This study recommends to further strengthen ecological protection and restoration,increase financial and technological investment,and improve the dynamic monitoring and scientific evaluation system to support policy optimization.Additionally,further research is needed to understand the impact mechanisms of climate change on rocky desertification and explore new governance pathways adapted to climate change.

Abstract:Due to the early extensive development,the geomorphic landscape,land resources,and forest vegetation have been severely damaged.Coupled with the fragile ecological environment in the plateau-mountainous areas,the ecological problems caused by abandoned mines have significantly affected the regional natural ecosystem and human settlements,thereby restricting economic and social development.In recent years,China has continued to promote the ecological restoration of mines,resulting in a marked improvement in environmental quality.However,some abandoned mines suffer from unclear restoration goals,improper management practices,and poor restoration outcomes due to insufficient investigation and inadequate comprehensive evaluation of ecological issues. In this study,Qujing City,a typical area in the plateau-mountainous region of eastern Yunnan,was selected as the research object.We systematically analyzed the geological environmental issues caused by abandoned mines in the area,as well as the ecological and environmental conditions of the sites where these mines are located.A comprehensive evaluation of the ecological issues associated with abandoned mines within the region was conducted.The ecological issues in the mining areas in the study area have been classified into different severity levels.The assessment results indicate that areas with severe(Level Ⅰ)and moderately severe(Level Ⅱ)ecological problems in the abandoned mines cover a total area of 999.01 hectares,accounting for 90.18％of the total area.Among these,areas with severe ecological problems(Level Ⅰ)are mainly located in Shizong,Luoping,and Fuyuan Counties along the Nanpanjiang River Basin,whereas areas with moderately severe ecological problems(Level Ⅱ)are primarily found in Shizong County and Fuyuan County along the Nanpanjiang River Basin,as well as in Xuanwei City along the Beipanjiang River Basin. Based on the comprehensive evaluation of the ecological issues associated with abandoned mines in the study area,and in conjunction with territorial spatial planning,the Nanpanjiang River Basin,which is identified as the most prominent and representative in terms of environmental problems,is prioritized.Additionally,considering the natural geographical patterns and focusing on the protection of the ecological barriers at the source of the Pearl River and the upper reaches of the Yangtze River,as well as addressing key ecological challenges such as soil erosion and rocky desertification,the study area is divided into four restoration zones:(1)the restoration area for water conservation and rocky desertification prevention and control in the Nanpanjiang River Basin at the source of the Pearl River;(2)the restoration area for water conservation in the Beipanjiang River Basin in the upper reaches of the Pearl River;(3)the restoration area for soil and water conservation in the Xiaojiang River Basin in the upper reaches of the Yangtze River;and(4)the restoration area for biodiversity conservation in the Niulanjiang River Basin in the upper reaches of the Yangtze River. For areas classified as Type Ⅰ,which face severe ecological problems,the main strategy is to carry out ecological restoration,expand forests and grasslands,and enhance the overall function and value of the ecosystem.In contrast,for areas classified as Type Ⅱ and Type Ⅲ,where ecological issues are relatively concentrated but less severe,the focus is on balancing development with ecological protection while meeting land use needs.By categorizing regions based on the severity of ecological problems,more precise and targeted ecological restoration measures can be proposed,thereby providing valuable reference and guidance for ecological protection and restoration in other similar plateau-mountainous areas.

Abstract:Puding county is located in the west-central part of Guizhou Province,covering a total area of 1,091 km2.It experiences a humid subtropical monsoon climate,characterized by an average annual precipitation of 1,378.2 mm and an average annual temperature of 15.1 ℃.As of 2021,Puding county had a resident population of 376,300,including an urban population of 144,900,resulting in an urbanization rate of 38.51％.The county's annual Gross Domestic Product(GDP)was 15.463 billion yuan,with the value added of the primary industry contributing 2.808 billion yuan,reflecting a year-on-year increase of 8.2％.The value added of the secondary industry was 4.785 billion yuan,a year-on-year increase of 10.06％,while the value added of the tertiary industry contributed 7.870 billion yuan,up 11.10％.This region is characterized by the typical development of karst geomorphology,and it frequently faces ecological challenges such as soil erosion and rocky desertification.Therefore,uncovering and predicting the impacts of land use change on Ecosystem Service Value(ESV)in karst mountainous areas under different scenarios is of great significance for maintaining regional ecological security,enhancing the value of ecosystem services,and formulating ecological protection and restoration policies.In order to deeply analyze the land use patterns and their response to ecosystem service value over an extended time series in Puding county,research and discussion were carried out across the three temporal dimensions:past,present,and future.This study aims to provide a scientific foundation and valuable insights for the sustainable development of ecosystems in the study area. Based on five periods of land use data from 1973,1989,2003,2010 and 2020,the equivalent factor method,which incorporates localized adjustments of food prices,was used to assess the ESV for each historical period.Additionally,the PLUS model was applied to simulate land use and ESV changes projected for 2030 under three scenarios,natural evolution,ecological protection,and economic development.The results indicate as follows. (1)The area of cultivated land in Puding county decreased sharply from 1973 to 2020,with a total reduction of 25.08％over the last 50 years.In contrast,the areas of forest land and construction land increased annually,with increases of 6,338.56 hm2 and 9,408.00 hm2,respectively. (2)The ESV of the study area from 1973 to 2020 was recorded at 3.100 billion yuan,2.238 billion yuan,2.598 billion yuan,3.277 billion yuan,and 3.510 billion yuan,respectively,exhibiting a general fluctuating upward trend.Regarding the ESV of various land types,the ESVs of forest land,grassland,and watershed all showed annual increases from 1989 to 2020,serving as main contributors to the overall increase in ESV.Specifically,in terms of the value of individual ecosystem service functions,hydrological regulation and climate regulation services made the most significant contribution to ESV,with the combined total of these two services accounting for 47.97％of the total ESV. (3)In the natural evolution scenario,the ecological protection scenario,and the economic development scenario projected for 2030,the areas of cultivated land,grassland,and unused land in Puding county are all expected to decline,mainly converted into forested land and construction land.Notably,the area of cultivated land is projected to experience the greatest loss under the ecological protection scenario,amounting to 5,196.42 hm2.The spatial distribution across the three simulation scenarios shows that the area of construction land is point-surface in the central part of the study area. (4)The ESVs for the natural evolution scenario,ecological protection scenario,and economic development scenario are projected to be 3.638 billion yuan,3.778 billion yuan,and 3.597 billion yuan,respectively,all of which exceed the ESVs recorded for the study area in 2020.From a spatial distribution perspective,the ESVs for Puding county as a whole present the characteristics of being higher in the east and west and lower in the center.Furthermore,the ESV of each land use type has passed the sensitivity test,indicating strong credibility in the results.

Abstract:Karst ground collapse is one of the most common geological hazards in karst areas.It is characterized by concealment,sudden occurrence and inhomogeneity,along with various other complex features.Understanding the mechanisms of karst ground collapse and conducting risk assessments for such events are of great significance for urban development and engineering construction.In November 2020,a large-scale karst ground collapse occurred in Chengnan community of Yingde City,Guangdong Province.A total of 31 collapse pits were identified,predominantly exhibiting elliptical and circular shapes,and spatially distributed in three strips.The duration was notably lengthy,resulting in relatively severe disaster impacts. Comprehensive investigation results and analysis show that the karst ground collapse in the study area primarily occurred in the main groundwater runoff zone,which is characterized by relatively thick overlaying layers and significant karst development.The spatial distribution of the strip align with the arrangement of three fault zones in the study area.In the vicinity of a sewage treatment plant,the stacking of karst caves is evident,characterized by a significant cumulative thickness of the caves,high permeability of the rock layers,and loose overlying soil with low cohesion.These factors created fundamental conditions for the concentrated occurrence of ground collapse.In the study area,the triggering mechanisms of karst ground collapse are influenced by frequent fluctuations in the water levels of the nearby Beijiang River,as well as human activities that involve groundwater pumping and draining.These factors induce hydrodynamic effects,including subsurface erosion and vacuum suction erosion of groundwater.Additionally,the presence of sewage leakage near the sewage treatment plant at the center of the study area altered hydrochemical properties of groundwater,resulting in chemical dissolution.Therefore,the primary mechanisms driving karst ground collapse in this area are chemical dissolution and hydrodynamic effects. In order to facilitate the formulation of targeted preventive measures,we selected eight susceptibility indicators and two vulnerability indicators after screening each indicator factor in the study area.These indicator factors were combined with the Analytic Hierarchy Process(AHP)to establish a comprehensive index model of karst ground collapse risk suitable for the study area.By leveraging GIS spatial analysis functions,we conducted a relatively accurate risk assessment of the study area.The results show that the risk of karst ground collapse in the study area can be categorized into two levels:high-risk and moderate-risk.The high-risk zone is mainly distributed around the sewage treatment plant and cement plant area,comprising 70.83％of the total study area.Conversely,the moderate-risk zone is mainly located in the northwest corner of the study area,accounting for 29.17％of the total. In conclusion,it is recommended to strengthen the dynamic monitoring and management of groundwater,along with implementing measures to prevent and control surface sewage seepage.These actions are essential to protect the region from ground collapse hazards and to reduce the risk of disasters.

Abstract:Tunnel construction can disrupt the groundwater balance,impacting the drainage of both surface water and groundwater,as well as causing other eco-environmental effects.This study takes a water-diversion tunnel as the research object.Prompted by a pronounced decline in the storage of the adjacent reservoir of the tunnel,it integrates hydrogeological surveying and tracer tests to characterize the altered recharge-flow-discharge conditions,elucidate the hydraulic interactions between the tunnel and the surrounding groundwater system,and quantitatively evaluate the tunnel's impact on the observed reservoir-storage variations. Field investigations indicate that groundwater in the study area can be divided into three categories:karst water from carbonate rock fissures,karst water from fissures characterized by carbonate rock interbedded with clastic rock,and karst water from pores and fissures characterized by mudstone interbedded with silty mudstone.The water bearing formations of karst water from carbonate rock fissures consist of the Lower Triassic Jialingjiang Formation(T1j)and the Daye Formation(T1d3+4)along the axis and wings of an anticline.These units exhibit significant water abundance and are well developed with karst landforms,such as karst depressions,sinkholes,caves,and underground rivers.Karst water from fissures characterized by carbonate rock interbedded with clastic rock occurs within the first and third members of the Middle Triassic Badong Formation(T2b1)along the axis and wings of a syncline.The water abundance of the formation is moderate,and karst features are only locally developed.Karst water from pores and fissures characterized by mudstone interbedded with silty mudstone is primarily stored in the second member of the Middle Triassic Badong Formation(T2b2)and exhibits comparatively low water abundance.Groundwater recharge is derived primarily from atmospheric precipitation and surface water bodies such as reservoirs and fish ponds.Due to the large terrain cutting,the speed of surface water runoff is fast. The catchment of the reservoir is located west of the axis of the water-diversion tunnel on the southeast wing of the anticline.Exposed strata comprise limestone,dolomitic limestone,dolomite,and rock-solution breccia of T 1j and T1d3+4,as well as limestone,argillaceous limestone,argillaceous dolomite,and mudstone of T2b.Within the Jialingjiang and Daye Formations,sinkholes,depressions,and dissolution fissures are well developed,facilitating efficient infiltration of rainwater through karst conduits to the saturated zone.Although karst development is weak in the Badong Formation,secondary structures have intensely fractured the rock mass;rainwater recharge,therefore,occurs dominantly through fissures.Overall,the catchment exhibits favorable groundwater recharge conditions.After infiltration,groundwater migrates southwestward along either longitudinal karst conduits or fissure networks.The deeply cut watercourse in which the reservoir is located,along with the dense network of tributary gullies,ultimately leads to the discharges of groundwater in the form of karst springs within these gullies. The water-diversion tunnel crosses the anticline,traversing limestone and dolomite of T1d and T1j,with T1j serving as the principal aquifer.The anticlinal axis functions as a watershed,resulting in the southern and northern segments of the tunnel each forming an independent groundwater system.The tunnel site is deeply cut,resulting in poor recharge conditions.Scattered precipitation accumulates only within the upper narrow peak-cluster depressions,subsequently infiltrating vertically along sinkholes.Southwest of the tunnel,the reservoir catchment consists of T1j,T1d,and T2b formations,which are characterized by well-developed sinkholes,karst depressions,and corrosion fissures that create favorable discharge conditions.Following rainfall events,groundwater is directed southwestward along longitudinally oriented karst conduits.These conduits are cut by gullies,where groundwater ultimately discharges as karst springs.Before the construction of the water-diversion tunnel,atmospheric precipitation infiltrated through surface karst depressions,sinkholes,dolines,or corrosion fissures to recharge groundwater.Afterward,a portion of the precipitation flowed through the aquifer and discharged in the form of an underground river along the riverbank.Another portion of flowed through the runoff that crossed fissures perpendicular to the structural trend,and discharged in the form of karst springs(including the S01 spring point)or underground rivers within the gully and watercourse that cut the south-eastern wing of the anticline.The spring points exposed in the gully and watercourse were the main source of water supply for the reservoir.Because the water-diversion tunnel intersected the transition zone between the vertical and horizontal circulation cells of the karst aquifer,its excavation repeatedly intersected underground rivers and cave systems.Severe water inflows were encountered,resulting in twelve springs within a 3-km radius becoming either completely or partially dewatered.Springs located to the southwest of the tunnel were less affected than those to the northwest. Analytical calculations indicate that the influence radius of the water-diversion tunnel on surface water and groundwater extends from 649 to 2,073 m,covering 13.7 km2.The overlapping area of the reservoir catchment is 4.02 km2.Tracer tests confirm a strong hydraulic connection between the surface sinkholes located above the tunnel,and the drainage outlet of the water-diversion tunnel and several spring points.Consequently,a portion of the reservoir's recharge has been diverted to runoff at the tunnel exit and subsequently discharged,thereby reducing the storage capacity of the reservoir.The findings demonstrate that the alteration of regional groundwater recharge-flow-discharge conditions induced by the tunnel project is the primary cause of the observed decline in groundwater-derived inflow to the nearby reservoir.

Abstract:The region along the Belt and Road is a critical global hub for energy production and supply,containing 55％of the world's oil reserves and 76％of its natural gas reserves.Carbonate rock oil and gas reservoirs hold an extremely important position in global hydrocarbon resources.Statistics show that carbonate reservoirs account for approximately 70％of the world's total oil and gas resources,50％of proven recoverable reserves,and 60％of global production.By the end of 2013,there were 53 UNESCO World Heritage Sites featuring karst landscapes worldwide,including 42 designated as World Natural Heritage Sites.The stunning karst landscapes and unique cave formations have become major tourist attractions,while the abundant karst water resources and carbonate rock oil and gas reserves support human survival and development.The karst regions along the Belt and Road encompass over 50％of the global karst areas,which coincide with intensive human activities.In the context of global change,these regions face prominent environmental challenges,including karst drought,rocky desertification,water pollution,and severe geological hazards such as collapses and depression waterlogging,posing substantial threats to regional eco-environmental security. Supported by a project of the China Geological Survey,this study employed MODIS Reprojection Tool(MRT)and the Environment for Visualizing Images(ENVI)software to conduct remote sensing interpretation of collected datasets,including annual precipitation,mean temperature,evaporation,elevation data,and satellite imagery.A specialized map of the karst geological environment along the Belt and Road was compiled,which laid a foundation for further classification of key types of karst belt along the route and serving the International Karst Science Program.By integrating remote sensing images,geological maps,literature,and other data,and combining with field verification,this study has compared the karst characteristics of plateaus,large slopes,plains,and coastal areas within their geological and climatic contexts.The main conclusions are as follows. (1)Karst distribution areas along the Belt and Road span about 12.3 million km2,representing over half of the global karst coverage.Among the countries along the Belt and Road,China,Russia,and Kazakhstan have the largest karst areas,ranking as the top three in terms of karst coverage. (2)The characteristics of karst distribution under different elevations,temperatures,rainfall levels,and evaporation rates along the Belt and Road are quantitatively analyzed.Karst areas located between 0 m and 1,000 m in elevation account for 74％of the total karst area,whereas those above 3,500 m represent only 8％.Karst areas with surface temperatures above 9 ℃ comprise 65.3％,while those below 9 ℃ account for 34.7％.Regarding annual rainfall,karst areas receiving 0 mm to 210 mm constitute 31％of the total area,those receiving 210 mm to 540 mm account for 32％,540 mm to 840 mm cover 18％,and areas with annual rainfall exceeding 840 mm represent 19％.Additionally,karst areas with evaporation rates below 205 mm account for 51.4％of the total. (3)A comparative analysis of karst development conditions and controlling factors in Ethiopia,Croatia,Turkey,Iran,Thailand,and South China reveals that the lithology and tectonics of soluble rocks serve as intrinsic drivers of karst development,establishing the fundamental framework for karst processes.Meanwhile,climate acts as an extrinsic driving force,with both factors jointly shaping the development of karst landforms.Taking the karst in South China as an example,this study analyzes the influence of tectonic uplift on the differentiation of karst landforms.Distinct vertical hydrological profiles and erosion-dissolution base levels have been formed during different geological periods.To adapt to changes in these base levels,karst geomorphological zones have been developed at varying elevations.Moreover,the significant disparities in elevation also induce variations in climate,hydrology,and tectonic conditions,which in turn cause geomorphological differentiation in karst landforms.Meanwhile,China's Qinghai-Xizang Plateau on the first terrain ladder is characterized by high altitude,low temperatures,and scarce rainfall.The development of modern karst is limited in this region,exhibiting only micro-karst formations on rock surfaces.In contrast,Southwest China(Yunnan,Sichuan,and Chongqing),located on the second terrain ladder,experiences abundant rainfall and steep slopes.This area undergoes intense fluvial downcutting,forming canyons and peak-cluster valleys.Meanwhile,Guangxi(China),Thailand,and other Indochina Peninsula plains lie on the third terrain ladder.These areas are characterized by a hot,humid climate and low-elevation terrains near sea level,exhibiting vigorous surface and subsurface karstification and developing classic karst landforms such as peak-cluster valleys,peak-forest plains,and isolated-peak plains.

Abstract:Sichuan Province is located in the Southwest China,with its western mountainous area serving as a transitional zone between the Qinghai-Xizang Plateau and the Sichuan Basin.The climate is complex,characterized by abundant rainfall,and the terrain is mainly mountainous,featuring significant variations in elevation.The geological conditions are complex,tectonic activities are frequent,and geological disasters occur regularly.In addition,with the increasing intensity of human activities,exposed slopes and rock masses are widely distributed.The weathering and detachment of rock fragments can easily trigger secondary disasters,posing potential threats.The widespread presence of rocky slopes makes these areas prone to such events,underscoring the urgent need for ecological restoration.Mosses play a critical role in ecological succession and soil formation on rock surfaces,acting as pioneer species that promote the development of thin soil layers.Exploring the impact of moss growth on rock weathering processes is beneficial for finding ways to promote ecological restoration.This study aims to investigate the weathering processes and mechanisms in this region by analyzing weathered rock bodies and bedrock properties under varying weathering conditions to elucidate their microscopic characteristics.Additionally,the influence of moss growth on rock weathering was further investigated.We collected samples from carbonate rocks and sandstones at various sites within several counties in western Sichuan Province.Our study focused on sites with varying degrees of moss coverage and differing weathering durations.The analyses included examining the microstructural features of weathered rock surfaces,assessing mineral composition,and analyzing elemental variations to understand how mosses interact with these geological materials.These investigations were conducted by using electron microscopy,scanning electron microscopy(SEM),X-ray diffraction(XRD)for mineral composition,energy-dispersive spectroscopy(EDS),and other analytical techniques. The results indicate that as weathering progressed,the breakdown of mineral crystal structures,the development of fractures in the rock mass,and the formation of secondary minerals occurred in both sandstone and limestone.These processes were accompanied by the infiltration of iron oxides and organic matter,and they intensified over time.Notably,sandstone exhibited a more pronounced weathering response during the early stages compared to limestone.During the weathering of carbonate rocks,a large amount of secondary minerals was produced,and the mineral composition evolved from simple to complex.In contrast,the main component of sandstone weathering has consistently been quartz;as weathering progressed,secondary minerals disappeared,and the mineral composition shifted from complex to single.The elemental content in limestone did not change significantly during the early stages of weathering,while the elemental content in sandstone changed markedly.In total,results show that the weathering of carbonate rocks is predominantly chemical,whereas physical weathering is more pronounced in sandstone. Furthermore,the impact of mosses on rock weathering is complex.For carbonate rocks,initial weathering stages exhibited minimal elemental changes with moss presence;however,with prolonged exposure,significant modifications in structural integrity and chemical composition occurred.The percentage of carbon and other elements,such as calcium and magnesium,changed markedly,due to the bioerosion effects of moss-generated organic acids,with carbon increasing and calcium and magnesium decreasing.Microstructural analysis revealed that moss-covered rocks exhibited deeper and wider fissures compared to their bare counterparts.This increase in fissure size is correlated with the mechanical and biochemical actions of mosses,which exploited small crevices to enhance their growth and further facilitate the weathering process.Over time,mosses create a conducive environment for microbial activity,which adds to the biochemical weathering of the rock substrate.When mosses grew on the surface of sandstone,it exacerbated the already intense physical weathering of sandstone during the early stages and resulted in compositional changes.Overall,moss growth accelerates the weathering process of rocks,but its influence is not significant during the early stages. The findings indicate that mosses significantly contribute to both the physical and chemical weathering processes of rocks,which in turn influence soil formation and ecological stability.These insights have important implications for ecological restoration strategies on exposed rock slopes,particularly in areas susceptible to erosion and geological instability.By harnessing the natural weathering capabilities of mosses,we can develop sustainable methods for restoring degraded landscapes and mitigating ecological risks associated with exposed rock surfaces.For the ecological restoration of limestone slopes,the use of mosses is more effective than its application on sandstone,as it provides protective benefits over time.Therefore,it is essential to consider the differences in rock types when we select suitable plants for ecological rehabilitation.Future studies should explore the long-term effects of moss-induced weathering on soil development and ecosystem restoration,particularly in sensitive mountainous regions.

Abstract:Tongling City,located in the south-central part of Anhui Province on the southern bank of the middle and lower reaches of the Yangtze River,lies within the hilly region of the riverine plain and experiences a subtropical humid monsoon climate.With a total area of 2,991.87 square kilometers,it is a crucial region within the Wanjiang Economic Belt.Renowned as the "Ancient Copper Capital of China",Tongling is abundant in natural resources,particularly minerals,including copper,sulfur,iron,gold,silver,coal,and limestone.As a significant mining area in China,there are currently 220 licensed mines in Tongling,which are extracting 30 million cubic meters of ore annually,with a total mining and processing output exceeding two billion yuan.The carbonate rock strata in Tongling are highly developed,with a cumulative thickness of over 1,500 m.These strata are primarily concentrated in the Middle-Upper Carboniferous to Lower Permian and Middle-Lower Triassic geological periods.Due to factors such as mining dewatering and groundwater pumping,Tongling has been vulnerable to geological hazards such as karst collapses. The sites with potential geological hazards are typically found in regions exhibiting clear signs of surface deformation.Real-time monitoring of surface deformation allows for comprehensive identification of the sites with potential geological hazards and timely early warnings.The simple monitoring methods,such as pile-embedding and painting to observe known hazard sites,have been employed;however,these techniques cannot capture large-scale subsidence data,making it difficult to detect and monitor unknown hazards.In recent years,Interferometric Synthetic Aperture Radar(InSAR)has been widely used as a large-scale,high-precision deformation monitoring tool.It offers several advantages over traditional methods,including all-weather capability,continuous operation,extensive spatial coverage,and high accuracy.With the development of time-series InSAR techniques like Persistent Scatterers InSAR(PSI)and Small Baseline InSAR(SBAS-InSAR),high-precision surface deformation monitoring using coherent pixels within InSAR data has become increasingly important in identifying and monitoring geological hazards. This study focuses on Tongguan District and Yi'an District in Tongling City,situated in the south-central part of Anhui Province,along the southern bank of the middle and lower reaches of the Yangtze River.The study area boasts extensive soluble rock distributions and rich mineral resources like gold,silver,copper,iron,and sulfur,with a mining history spanning over 3,500 years.Consequently,geological hazards like karst collapses and mining collapses are prevalent.Fig.1 marks 130 locations of historical karst collapse,primarily concentrated near Shizishan in Tongguan District.Fig.1a illustrates the terrain and karst development within the study area,while Fig.1b depicts the landform,characterized by higher terrain in the south and lower,flat terrain in the north(the Yangtze River alluvial plain,with elevations ranging from 6.5 to 20 m)and hilly terrain in the south(with significant topographic relief and elevations generally between 50 and 250 m,peaking at 493 meters at Tongguan Mountain). This study utilizes SBAS-InSAR technology to process Sentinel-1 data covering Tongling City,identifying local deformation zones from 2015 to 2021,including the Xinqiao Mining Area,Laoyaling,Bijia Mountain,and Liuguo Chemical Plant.The maximum deformation rate,observed in the Xinqiao Mining Area,is approximately 118 mm/yr.Analysis of these deformation zones indicates that the combined effects of karst geological conditions and human activities like mining have contributed to the observed deformation characteristics.Notably,deformation in the Laoyaling tailings pond is also influenced by rainfall.Our findings demonstrate that InSAR technology can be effectively employed for large-scale geological hazard identification and monitoring,providing vital information for disaster prevention and control.For areas with significant deformation,it is recommended to install corresponding ground monitoring measures to assess risks in detail.With the launch of China's land exploration satellites and future satellite missions,abundant SAR satellite data will become available for more detailed analysis of deformation characteristics,enabling more precise monitoring and assessment of hazard sites.InSAR technology will play an increasingly critical role in disaster monitoring in this region.

Abstract:The karst ecological environment is characterized by fragility,sensitivity,vulnerability,heterogeneity,and limited natural regenerative capacity.The ecosystem formed through karst ecological restoration and conservation provides essential ecological products(eco-products)for human beings.Realizing the value of these products is an important initiative for addressing human-land conflicts in fragile environments,sustaining the benefits of ecological restoration,promoting the sustainable development of poverty alleviation efforts,and practicing the principle that "lucid waters and lush mountains are invaluable assets". Hebei Province,which surrounds Beijing and Tianjin,is characterized by high terrain in the northwest and low terrain in the southeast,with a variety of landforms.Two major mountain ranges,the Yanshan Mountains and the Taihang Mountains,cover 48.1％of the total area of the province.China is implementing restoration and protection projects for karst forest ecosystems through the Three-North Shelterbelt Forest Program.These ecosystems are ecologically significant,as they contribute to the conservation of water,soil,and biodiversity.They serve as primary providers of eco-products and form a crucial ecological security barrier for the North China Plain.Recognizing the intrinsic value of eco-products in this region is essential,as it will act as a key driver for transforming green mountains into invaluable assets in the karst ecologically fragile areas-an approach that reflects distinctive Chinese and Hebei characteristics.Therefore,given the unique features of the karst terrain in Hebei,it is imperative to assess the value of eco-products based on localized data.This approach will enhance the realization of their value and optimize transformation rates in response to environmental heterogeneity and other factors.This study holds significant academic and reference values for Hebei and even the broader northern karst regions. In the karst regions of Hebei,the Three-North Shelterbelt Forest Program has implemented large-scale karst ecological restoration and protection efforts,but raising critical questions:Can these ecosystems further optimize their service functions?Can they provide additional high-quality eco-products to meet people's growing need for a beautiful environment?Can green mountains be effectively transformed into invaluable assets?The chain process of karst eco-products valuation,value transformation,and the value realization mechanisms and pathways becomes the key scientific challenge underlying the technical bottlenecks that must be addressed in this region. The realization of the value of eco-products refers to the process of transforming their ecological value into economic profits through the rational development and utilization of eco-products under the premise of maintaining ecosystem stability and integrity.The mechanisms for realizing the value of eco-products include policy,market and technology approaches to promote the value realization.The total economic value of eco-products transformed through various pathways is termed the amount of value transformed.Addressing the shortcomings of the existing eco-product mechanisms and pathways-such as low premium effects and inefficient value transformation-this study employs 35 regions in Hebei with the karst area exceeding 10％of the total area as a case study.Based on localized data accounting,it calculates the Gross Ecological Product(GEP)and evaluates the value transformation rate of eco-products.By analyzing influencing factors from the perspective of value transformation efficiency,this study proposes mechanisms and pathways to enhance the realization of eco-product value.The results show that the GEP of karst regions in Hebei in 2022 was 602.822 billion yuan,the value transformed from eco-products was 217.211 billion yuan,and the value transformation rate is about 36.03％.Material products and cultural service products contributed 35.21％of the value transformation rate,representing the most effective eco-products in the karst regions of Hebei,while regulating services contributed only 0.83％.The study reveals the existence of fragile ecosystem mechanisms,imperfect safeguard mechanisms,and a limited range of realization pathways in the karst regions of Hebei.Accordingly,differentiated improvement strategies are proposed:at the mechanism level,it is suggested to strengthen ecological protection and restoration,improve basic security and establish long-term incentives;at the level of implementation pathway,a trigram model encompassing government leadership,market-driven mechanisms,and government-market coordination should be introduced.