Online First

Articles in press have been peer-reviewed and accepted, which are not yet assigned to volumes/issues, but are citable by Digital Object Identifier (DOI).
Display Method:
Field experiment on hydraulic channel sealing via grouting to prevent groundwater pollution in karst region
JI Zhihao, CHEN Shiwan, WU Jiaoji, YU Huiyun, WU Pan, MA Lanjian
, Available online  , doi: 10.11932/karst2025y021
Abstract:
The karst regions in southwestern China are characterized by intense karstification, complex hydrogeological conditions, and well-developed karst conduits with pronounced spatial heterogeneity. These factors contribute to the inherent vulnerability of karst groundwater systems, rendering them highly susceptible to contamination. Additionally, large-scale mining activities in these areas generate substantial volumes of wastewater and waste materials, exacerbating groundwater pollution. Consequently, the development of scientific technologies for the prevention, control, and assessment of groundwater pollution is of significant importance. This study focuses on the Zimudang mining area in Guizhou Province, where curtain grouting experiments were conducted to seal identified karst conduits, targeting the dominant hydraulic pathways of groundwater contamination. Real-time in-situ monitoring using electrical resistivity methods was employed throughout the grouting process to evaluate the effectiveness of the sealing measures.The Zimudang depression is a critical surface water convergence area within the study region, where the converging surface water is transformed into groundwater through the K20 drainage cave located beneath a steep cliff on the northeastern side of the depression. Mining activities have compromised the water-blocking function of the F1 fault, altering the groundwater flow so that it converges toward the mined-out areas and mining tunnels. Within the mining area, the K20 drainage cave serves as a channel for the concentrated recharge of groundwater by atmospheric precipitation; once entering the K20 drainage cave, the principal karst hydraulic conduits extend roughly in an east−west direction. Taking into account the characteristics of subterranean river channels, topography, and surface structures, the curtain grouting test site was determined to be located in the northern part of the tailings pond. Drilling and borehole television surveys were conducted at the site, and analysis of core logs and borehole TV results confirmed significant karst development in the underlying strata, which serve as the dominant hydraulic pathways for groundwater contamination migration. To ensure that the grout solution adequately permeates and fills fractures and karst cavities, high-pressure intermittent grouting was adopted, with grouting performed sequentially from ZJ08 to ZJ01, followed by a second round after the injected grout cooled. Throughout the entire grouting process, high-density resistivity and transient electromagnetic methods were employed to monitor changes in formation resistivity.In this experiment, one high-density electrical measurement line and eleven transient electromagnetic measurement lines were deployed. Three electrode configurations—Wenner, dipole, and Schlumberger—were utilized, with measurement depths of 15 m, 15 m, and 17 m, respectively. All three configurations demonstrated a clear increase in formation resistivity within the grouted zone, with the low-resistivity regions adjacent to the boreholes exhibiting more pronounced improvements post-grouting. For instance, among the transient electromagnetic measurement survey lines (S3, S5, S7, S8, S10, and S11), significant increases in formation resistivity were observed in lines S3, S5, S7, and S8, indicating effective grouting and sealing. In contrast, lines S10 and S11 showed either negligible changes or a decrease in resistivity after grouting. This discrepancy is attributed to the fact that line S10 was situated beyond the grouting influence zone due to its distance from the grouting wells, while line S11 exhibited localized resistivity reductions, likely caused by the displacement of water from karst cavities and fractures as grout infiltrated these features. Analysis of the geophysical monitoring data revealed that the high-density electrical method is more suitable for detecting shallow resistivity variations in areas with limited terrain, whereas the transient electromagnetic method is more effective for characterizing deeper subsurface electrical properties.To quantitatively assess the grouting effectiveness, formation porosity was derived from resistivity measurements using Archie's formula. By comparing porosity variations before and after grouting, the grout diffusion area was delineated, and the effectiveness of blocking groundwater pollution pathways was evaluated. For instance, in measurement lines S3, S5, S7, and S8, the grout diffusion area within a 2-meter radius of the grouting wells ranged from 21.42 to 99.32 m2. The maximum reduction in formation porosity reached 65.7%, with an average porosity reduction of 39.9%. This study demonstrates that electrical resistivity monitoring enables real-time in-situ evaluation of the grouting sealing effectiveness in karst conduits. In addition, by converting resistivity data into formation porosity for quantitative analysis, it is possible to accurately delineate the grouting diffusion area and sealing range, thereby assessing whether key hydraulic pathways have been effectively sealed. This approach provides robust technical support for evaluating the performance of curtain grouting in blocking the dominant groundwater contamination pathways in karst regions.
Mechanism of karst Waterlogging formation and effective control
HUANG Qibo, KANG Zhiqiang, DENG Zhong, TANG Yongchen, WU Huaying, ZOU Changpei, LI Tengfang, LIAO Hongwei, MA Junfei, LIANG Jian
, Available online  , doi: 10.11932/karst2025y020
Abstract:
The global karst area is about 22 million km2, accounting for 15% of the global land area. The people in karst areas are threatened to varying degrees by droughts and floods. Waterlogging is a geological hazard formed by the superposition of karst geological and geomorphological environment and human activities. The closed karst terrain combined with strong human engineering activities causes serious soil erosion. Soil leaks into the lower karst pipeline through the sinkhole, causing underground pipeline blockage , drainage obstruction, and frequent occurrence of waterlogging; With the increase of extreme weather, human activities, soil erosion in low-lying areas, and blockage of karst pipelines, if left untreated for a long time, the waterlogging time in low-lying areas will become more frequent and severe.Karst Waterlogging disasters have caused significant losses to people in karst areas, seriously threatening their production and life. The comprehensive management of these disasters has a major national demand. The characteristics of Waterlogging disasters are periodicity, group occurrence, and suddenness. The enclosed karst landform and the special "binary" structure of the karst aquifer are the internal factors that cause karst Waterlogging. The subtropical monsoon climate with concentrated rainfall is the external condition for the occurrence of karst Waterlogging. Unreasonable engineering activities have caused a large amount of soil and water loss, blocking underground karst channels, which is the human factor leading to increasingly karst Waterlogging. Severe karst Waterlogging mainly occurs in karst valleys and depressions where underground rivers and pipelines are developed. The recharge area, runoff area, and discharge area of an underground river have different mechanisms for causing internal Waterlogging.At present, there is a lack of systematic research and characterization of the "binary" structure of karst aquifers. Soil erosion leads to a decrease in the rainfall threshold for causing Waterlogging, and no relevant studies have been conducted on the impact of soil erosion on degeneration of underground pipeline water conveyance capacity. There is a lack of in-depth research on the formation mechanism of karst Waterlogging disasters, and it is even more impossible to predict the extent of karst Waterlogging disasters and the losses caused under extreme climate events, which seriously affects the effectiveness of karst Waterlogging control. In the later stage, systematic observations of the hydrological dynamics and soil erosion dynamics that lead to urban Waterlogging should be carried out, characterize the karst aquifer fracture-cave "dual" structure in detail, clarify the rainfall threshold and its changing characteristics that cause urban Waterlogging, elucidate the hydrological processes and soil erosion processes and their controlling factors that lead to the formation of karst Waterlogging disasters, analyze the relationship between reduction coefficient of outlet flow and the amount of soil erosion in low-lying areas, and systematically reveal the mechanism, evolution laws, and principles of karst Waterlogging formation, and then propose scientifically effective countermeasures for karst Waterlogging regulation.
Analysis of characteristics and control factors of underground river pipeline based on tracer test and crack measurement-Take Luohandu Underground River as an example.
LI Tengfang, SHEN Lina, HUANG Qibo, WU Qingpeng, MA Junfei, LIAO Hongwei, WU Huaying, ZOU Changpei, PU Zhenggong, LENG Rubing
, Available online  
Abstract:
The karst development in southwest China is very remarkable. At present, there are 3066 karst underground rivers that have been proved. As the main space of groundwater resources, it is of great significance to study the distribution characteristics and development control factors of karst pipelines. In this paper, Luohandu underground river in Gongcheng county was taken as the research object, and a 1: 50000 hydrogeological survey was carried out. It was found that there was an upper karst cave at the outlet of Luohandu underground river, which was supposed to be the original discharge outlet. The length of the karst cave was 567.9m, and according to the investigation, it was found that the pipeline of the lower underground river was about 1.6km long. According to the regional geological data, Luohandu Underground River is located near the structural belt of Chestnut-Heping fault and Jiahui translational fault, in which Chestnut-Heping fault develops in the north-south direction and Jiahui translational fault develops in the east-west direction. The chestnut-Heping fault is cut in the working area, and the structure controls the development of underground river pipelines.In order to find out the controlling factors of pipeline development and development, groundwater tracing test and fracture measurement are carried out. The tracer test was put into the skylight of the underground river in the upper reaches of the underground river, and the tracer was received only in 1.5 hours. The tracer concentration reached the peak in 1.7 hours, and then began to decrease. It was calculated that the maximum velocity of groundwater between the skylight and the outlet of the underground river was 550.4 m·h−1, and the average velocity was 447.7 m·h−1 , which showed that the underground water flow between the skylight and the outlet of the underground river was closely related to the underground water, and the underground water migration path was relatively smooth, and the karst was developed in the shape of a single pipe. At the same time, four groups of cracks were measured by statistical window method, including three groups of structural cracks and one group of bedding cracks. In order to study the control of cracks on the development of karst pipelines, the statistical analysis of crack measurement results shows that the direction of cracks in the first and fourth groups is basically consistent with the development direction of underground rivers. Further analysis shows that high-angle structural fractures provide an important channel for the recharge of underground rivers. By calculating the principal value of permeability tensor of structural fractures, it was found that the dip directions of the third principal permeability tensor (K3) at five measurement points ranged from 254° to 292°, with dip angles mostly less than 25°. The direction of maximum permeability governs the seepage direction of karst groundwater, and long-term erosion and dissolution along this direction ultimately control the development of the underground river conduit.On the basis of 1: 50000 hydrogeologic survey and regional geological data, this study understands the structural pattern, describes the distribution and spatial characteristics of underground river pipelines in detail based on high-precision tracer tests, and analyzes the control of structural fractures on underground river pipelines by combining fracture measurement and calculation of permeability tensor. Through various technical means, not only the distribution characteristics of underground river pipelines are systematically grasped, but also the controlling factors of underground river formation are deeply revealed, which provides an important scientific basis for the subsequent investigation of underground rivers and water resources evaluation.
Relationship between surface soil pollen and modern vegetation at the Guangxi Karst Huanjiang Observation Station
HAO Xiudong, LU Yaxian, OUYANG Xuhong, LI Lixue, QIN Linjuan, WEI Jiasheng, WANG Ailan, HUANG Linqian, LIN Chunyu
, Available online  , doi: 10.11932/karst2025y017
Abstract:
This study takes surface pollen samples from different land use methods/vegetation types at the Huanjiang Observation and Research Station for Karst Ecosystems, Chinese Academy of Sciences (hereinafter referred to as the Huanjiang Station) as its research object. The Huanjiang station is located in the southern part of Huanjiang Maonan Autonomous County, Hechi City, Guangxi and represents typical karst peak cluster depression ecosystem in China. It is situated in the subtropical monsoon climate zone, with a mild climate and abundant rainfall throughout the county. The forest communities are primarily composed of evergreen broadleaf forests, followed by some deciduous broadleaf and mixed evergreen coniferous and broadleaf forests.The article aims to explore the characteristics of surface pollen assemblages under different land use methods/vegetation types at the Huanjiang Station, establish a correspondence between surface pollen and modern vegetation, so as to provide theoretical references for ecological restoration, Quaternary paleoenvironmental and paleoclimate reconstruction, and historical research on human interference activities in the study area and similar karst regions.All 24 topsoil and moss samples were prepared at the Key Laboratory of Environment Change and Resources Use in Beibu Gulf (Nanning Normal University), Ministry of Education, and then standard conventional acid-base methods to extract the pollen, that is weighing about 30 g of dry samples of topsoil samples and about 3 g of dry samples of moss samples. Add HCL to dissolve calcareous minerals, HF to digest silica, and several distilled water rinses. Finally, a 7 - μm nylon sieve was used to remove unwanted small particles, then collect the pollen to a 5 ml centrifuge tube. A pill of Lycopodium spores (10,315 grains/tablet) was added to each sample to calculate pollen concentration. The percentage of each pollen taxa is based on the total terrestrial pollen sum only, whereas that of spores is based on the sum of both pollen and spores. Pollen and spores were identified using a Leica DM4000 B microscope with 200/400x magnification. More than 300 pollen grains of per sample were counted. The programs Tilia (version 1.7.16) was used to construct the pollen diagrams. Using the Canoco (versions 5.0) software, principal component analysis (PCA) was applied to the pollen percentage data.The results show, (1) A total of 49 pollen taxa (genera or family)were identified from 24 topsoil (or moss) samples in the Huanjiang Station, 25 taxa belonged to trees and shrubs, there are mainly Pinus, Cupressaceae/ Taxodiaceae, Fabaceae, Euphorbiaceae, Magnoliaceae, Moraceae, among them, Pinus had the highest content (averaging 56.8% and reaching a maximum of 87.62%). And 20 taxa were Herbaceous, there are mainly Poaceae, Asteraceae, Araceae. The spores of ferns are mainly Nephrolepis, Dicranopteris and Pteris. In addition, freshwater algae ( Concentricystis ) spores also appeared in the samples.(2)There was a large difference in the concentration of topsoil pollen among different land use methods/vegetation types in the depression of Huanjiang Station, the lowest pollen concentration was 4,131 grains · g−1 in the topsoil samples of the secondary growth of forest, and the highest was 41,6781 grains · g−1 in planted restoration forest. The average pollen concentration was relatively low, at 54,432 grains · g−1. There was a significant difference in the average concentrations of topsoil samples and moss samples, which were 27,371 grains · g−1 and 189,738 grains · g−1, respectively. Among all the samples, Pinus pollen had the highest concentration, reaching 19,232 · g−1, followed by Asteraceae ( 2,280 grains · g−1 ), Poaceae ( 1,535 grains · g−1 ) and Euphorbiaceae ( 1,461 grains · g−1 ). In addition, the spore concentration of ferns was relatively high, with an average of 6, 353 spores · g−1. (3)The result of principal component analysis ( PCA ) show that the pollen assemblage was well discrete and was heterogeneous, which could roughly achieve classification. Among different land use methods/vegetation types, corn fields correspond clearly with Zea, and coniferous woodland correspond clearly with Moraceae, enabling effective differentiation. Secondary growth of forest and planted restoration forest can be concentrated relatively well.The conclusion of this article is, (1)The topsoil pollen composition corresponds well with the vegetation types of each land use type/vegetation type and the combination of surface pollen can basically reflect the overall characteristics of vegetation around the depression. (2)PCA analysis can effectively distinguish grassland, planted restoration forest, coniferous woodland, secondary growth of forest, and cornfields, it shows that the surface pollen of different land use / vegetation types has obvious differentiation. However, mulberry forest cannot be well distinguished, which may be related to the fact that Morus sampling time and pollen preservation conditions.(3)The pollen concentrations of different land use methods/vegetation types are in the order of planted restoration forest > mulberry forests > cornfields > secondary growth of forest > grasslands > coniferous woodland, which may be closely related to vegetation composition, soil disturbance, and pollen preservation conditions.
Evaluation of karst hydrogeological conditions and reservoir leakage analysis in the basin of Yangquan River, Fengjie County, Chongqing City
WU Jian, MI Xiangli, LAN Meng
, Available online  , doi: 10.11932/karst2025y014
Abstract:
Southwest China constitutes the world's largest karst region with concentrated exposure and distribution of carbonate rocks.Within this area, Chongqing City is a pivotal component of the southwestern karst system, with karst landscapes covering approximately 30,000 km2, primarily concentrated in the northeastern and southeastern of Chongqing City. This region has experienced multiple phases of strong karstification, resulting in well-developed karst landforms such as solution caves, sinkholes, karst springs, and underground rivers. Abundant surface water and groundwater have triggered frequent karst geohazards, including reservoir leakage, water inrush in tunnels, and karst collapses. These events have seriously constrained the safety construction of hydraulic projects and local economic development.The Yangquan River basin in Fengjie County, Chongqing City covers an area of approximately 45.5 km2, with a total river length of about 14 km. The daily average river water level is 895.1 m, while the average annual flow is 0.686 m3∙s−1, corresponding to a average annual runoff of 21.63 million m3. The basin has a subtropical warm and humid monsoon climate, characterized by an average annual precipitation of 1163.1 mm, an average annual evaporation of 1267.8 mm, and an average annual temperature of 18.7 ℃. Limestone and dolomite strata are developed in the basin, with undeveloped and small-scale faults located on the slopes of both banks. In contrast, fold structures are extensively developed, generally trending parallel to the Yangquan River. The left bank of the Yangquan River exhibits multiple gullies controlled by lithology and NW-trending fold structures. The topographic divide is the Jinfeng Mountain with elevations ranging from 1800 m to 1900 m. The right bank constitutes an interstream block between the Yangquan River and the Taoyuan River, characterized by a topographic divide elevation of approximately 1450~1600 m. Therefore, the left and right banks of the Yangquan River have steep topography, forming a typical “V”-shaped longitudinal valley. Overall, the karst hydrogeological conditions are complex, and karst leakage has become a crucial issue in the construction of pumped storage power stations in this area.This paper evaluates the karst hydrogeological conditions of Yangquan River basin by using geological survey and mapping, hydrogeological field experiments, and karst water system analysis. Subsequently, the karst leakage type, karst leakage location, and karst leakage passage are systematically analyzed during the impoundment of the Yangquan River reservoir. Ultimately, the three-dimensional seepage filed of the Yangquan River under natural and impounding conditions are conducted by using MODFLOW software. The karst leakage rates are calculated and validated through numerical modelling and analytical formulas. The results show that in the Yangquan River basin, karst development is mainly concentrated in the high-purity zone of carbonate rocks, structural fracture development zone, and discharge base level, forming five concentrated zones that exhibit a northeast-trending banded distribution. The degree of karst development gradually decreases with the increase of depth, exhibiting significant elevation zoning characteristics. This results in a dual shell-core structure characterized by strong karst development on the surface and weak karst development internally. Moreover, the karst groundwater system in the Yangquan River is a typical type of karstic fissure-tube-underground river system in the anticline mountainous of Southwest China, which can be spatially divided into strong karst anticline zone, strong karst syncline zone, and moderate karst syncline zone. Based on the water balance theory, the karst groundwater system in the site is classified as a secondary hydrogeological unit, namely II-2 interstream block. The recharge, runoff, and discharge modes of karst groundwater in the basin are primarily characterized by rainfall infiltration and concentrated drainage through longitudinal-transverse conduit-fissure flow systems. Packer tests and groundwater tracer tests indicate that the left bank of the Yangquan River develops an interconnected karst conduit system, while the right bank exhibits a dual-media system composed of fissure networks and karst conduits. During the impoundment of the lower reservoir in the Yangquan River, pore leakage may occur at the dam foundation, while karstic tube leakage and karstic tube-fissure coupling leakage may develop on the both left and right banks; however, there will be no leakage in the lower adjacent valley. The analytical solutions for the pore leakage and karstic tube leakage are 9505.13 m3∙d−1 and 117979.20 m3∙d−1, respectively. As a comparison, the numerical result of karst leakage is approximately 12184.60 m3∙d−1, indicating that more efficient and reasonable numerical methods and anti-seepage control measures need to be adopted to address karst groundwater tube system on both banks to achieve the conditions for dam construction and reservoir formation. This study can provide some suggestions for hydraulic projects in Southwest China.
Comprehensive Evaluation and Restoration Management of Ecological Issues in Historical Abandoned Mines in Plateau Mountain Areas: A Case Study of Qujing City, Yunnan
WANG Bo, ZHAO Li, GUO Yun, CHEN Xiaomei, SONG Zenghong
, Available online  , doi: 10.11932/karst2025y016
Abstract:
Due to the early extensive development, the geomorphic landscape, land resources and forest vegetation have been seriously damaged, coupled with the fragile ecological environment in the plateau and mountain areas, the ecological problems of the abandoned mines left over from history have seriously affected the regional natural ecosystem and human settlements, restricting economic and social development. In recent years, China has continued to promote the ecological restoration of mines, and the quality of the ecological environment has been significantly improved, but some abandoned mines have unclear restoration goals, improper management measures and poor restoration results due to inadequate investigation and inadequate comprehensive evaluation of ecological problems.This article selects Qujing City, a typical area in the eastern plateau mountainous region, as the research subject. It systematically analyzes the geological environmental issues caused by historical abandoned mines in the area, as well as the ecological and environmental conditions of the areas where these abandoned mines are located. A comprehensive evaluation of the ecological issues of historical abandoned mines within the region is conducted.The ecological issues of the mining areas in the study zone have been classified into different levels. The assessment results indicate that the area with severe (Level I) and moderately severe (Level II) ecological problems in the abandoned mines covers a total of 999.01 hectares, accounting for 90.18% of the total area. Among these, the areas with severe ecological problems (Level I) are mainly located in the Shizong, Luoping, and Fuyuan counties along the Nanpan River basin, whereas the areas with moderately severe ecological problems (Level II) are primarily found in the Shizong county and Fuyuan county along the Nanpan River basin, as well as in the Xuanwei city along the Beipan River basin.Based on the comprehensive assessment results of the ecological issues of historical abandoned mines in the study area, combined with the territorial spatial planning, the Nanpanjiang River Basin, which is the most prominent and typical in terms of problems, is taken as a priority. At the same time, considering the natural geographical pattern, 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 the key ecological issues of soil erosion and rocky desertification, the study area is divided into four restoration zones (the Nanpanjiang River Basin water conservation and rocky desertification prevention and control restoration area at the source of the Pearl River, the Beipanjiang River Basin water conservation restoration area in the upper reaches of the Pearl River, the Xiaojiang River Basin soil and water conservation restoration area in the upper reaches of the Yangtze River, and the Niu Lanjiang River Basin biodiversity conservation restoration area in the upper reaches of the Yangtze River).For the severely ecological problem areas classified as Type I, the main strategy is to carry out ecological restoration, expand the scale of forests and grasslands, and enhance the overall function and value of the ecosystem; for areas classified as Type II and Type III where ecological issues are relatively concentrated but not as severe, the emphasis is on ensuring that development and ecological protection can proceed in a coordinated manner while meeting land use needs. By dividing the regions according to the severity of ecological problems, more precise targeted ecological restoration measures are proposed, providing reference and lessons for the ecological .
Risk Assessment of Geological Hazard Based On GIS and Information Modeling Methods
XIE Siqin, LUAN Song, ZHOU Dahai
, Available online  , doi: 10.11932/karst2025y013
Abstract:
Over the years, geological hazard such as collapses landslide, dangerous rock, and karst collapse have occurred frequently in Guangxi, with a wide distribution area, long impact time, a large number of people affected, and heavy economic losses. It has practical guidance significance to provide basic scientific for disaster prevention and reduction work in the area, and to carry out early prediction and evaluation of geological hazard risk.The risk of geological hazard refers to the possibility of a specific scale and type of geological hazard occurring within a certain area and time period under the influence of certain triggering factors.The early prediction and evaluation of geological hazard risk is currently a major challenge in disaster prevention and reduction. There are many influencing factors and evaluation methods for risk assessment of geological hazard. This article takes Xiangzhou County in Guangxi Province as an example, and selects the information model method based on the investigation of the main control geological conditions for potential hazards. Based on the overlay analysis function of ArcGIS on spatial data, according to the characteristics of geological hazard development and potential hazards in the work area, 8 evaluation indicators are selected, including landform type, geological structure, engineering geological rock group and terrain slope, karst development degree, slope structure, vegetation coverage, and human engineering activities. The engineering geological rock group and terrain slope are taken as the main control factors, and other factors are used as secondary factors for overlay zoning. After using the natural breakpoint method in statistics to reclassify the prone zoning, an evaluation grid measured by the value of information is generated to evaluate the susceptibility of geological hazards. The susceptibility of geological hazards in Xiangzhou County is divided into four levels, including low susceptibility, medium susceptibility, high susceptibility, and extremely high susceptibility. Among them, extremely high and high susceptibility are mainly distributed in river terraces, peak forests and valleys where the underground karst areas is strong development, and in the rocky mountain areas, and areas with strong human engineering activities. Medium and low susceptibility are mainly distributed in hilly and low mountain hilly terrain areas. On the basis of susceptibility assessment, according to the meteorological characteristics of the study area, the maximum 24-hour rainfall at each return period of rainfall stations in Xiangzhou County and surrounding areas was collected. The Kriging method in AcrGIS was used to generate contour maps of rainfall once in10 years, once in 20 years, once in 50 years, and once in 100 years. The geological hazard susceptibility assessment map and contour maps of different rainfall conditions were normalized, and spatial superposition analysis was carried out to generate geological hazard risk assessment maps under different rainfall return periods measured by the value of information. The probability was divided into extremely high risk, high risk, medium risk, and low risk using the natural breakpoint method, and the geological hazard risk assessment under different rainfall conditions return periods was obtained. The evaluation results indicate that the larger the recurrence period of rainfall conditions, the larger the distribution area of high and extremely high risk geological hazards, and the impact of rainfall on geological hazards is significant. The areas with extremely high geological hazard risk in Xiangzhou County are mainly distributed in the central part near the Sicun Town, where is the river terrace landform units, and the sand gravel clay double-layer structure soil rock formation areas, the eastern Dale Town to Baizhang Town and the western Maping Town, where is the peak forest valley landform units, and the thick to blocky strong rock melted hard limestone and dolomite rock formation areas; The high-risk areas are mainly distributed in the hilly and river terrace landform units, including the northeast of Yunjiang Town, Sicun Town to Dale and Baizhang Township, as well as the west of Maping Town; The remaining areas are mainly classified as medium to low risk areas, with hills and low mountain hills being the main geomorphic units.This article scientifically evaluates the geological hazard risk in Xiangzhou County, Guangxi, highlighting the key points and adapting measures to local conditions, dividing different geological hazard risk levels, and clarifying the geological hazard risk zoning under different rainfall conditions, to provides a certain reference basis for geological hazard warning and forecasting, and improves the technical support system for geological hazard identification, zoning, and control in the research area. At the same time, its evaluation results can serve as the basis for national spatial planning, guiding population and economy to gather in low-risk areas in an orderly manner.
Genetic mechanism of karst water revealed by hydrochemistry and isotopes in Pingliang, Gansu province
ZHANG Chengwen, ZHENG Haofan, HE Jianbo, LIU Zilong, MAO Xumei
, Available online  , doi: 10.11932/karst2025y015
Abstract:
Karst water is one of the significant water resources 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. It provides a scientific basis and theoretical support for promoting the sustainable development of regional water resources and 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 indicate the scope and dynamic changes of the karst water system. To uncover the genetic mechanism of karst water in Pingliang City, we comprehensively analyzed the hydrochemical characteristics and sources of karst water in Pingliang City using methods such as Piper trilinear diagrams, mathematical approaches, and ion ratio coefficients. The research results indicate that the groundwater in the region can be mainly divided into two types: HCO3-Ca and HCO3·SO4-Na, with Ca2+ and Na+ as the primary cations and ${\rm{HCO}}_3^{-}$ as the primary anion. The pH value ranges from 6.72 to 6.9, exhibiting weakly alkaline hydrochemical characteristics overall. The total dissolved solids (TDS) value of groundwater ranges from 158.01 mg·L−1 to 1519.40 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, ${\rm{SO}}_4^{2-}$, and ${\rm{HCO}}_3^{-}$. Additionally, the content of Mg2+ is significantly positively correlated with the contents of the main anions Cl, ${\rm{SO}}_4^{2-}$, and ${\rm{HCO}}_3^{-}$ (r > 0.7, p < 0.01), and the content of Na+ also has a significant positive correlation with the contents of Cl and ${\rm{SO}}_4^{2-}$ (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 Pingliang karst water. Gibbs diagram combined with mineral saturation index analysis further confirms that the dissolution of evaporites, carbonates, and silicate minerals is the natural source of hydrochemical components in Pingliang City. Ca2+, Mg2+, and ${\rm{HCO}}_3^{-}$ in the karst groundwater of Pingliang City mainly originate from the combined dissolution of calcite and dolomite. Hydrogeological conditions and hydrogen-oxygen isotope results 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‰, with an average of -10.07‰, indicating that all groundwater is recharged by atmospheric precipitation infiltration. Based on the identification of the karst water genetic model, it is determined that there are two genetic modes of karst water in the Pingliang area. Mode 1: Atmospheric precipitation infiltrates through the overlying Quaternary loess layer, continuously dissolving sulfate minerals in 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 aquifer. In this mode, the chemical type of karst water is mainly HCO3-Ca. Although both modes receive atmospheric precipitation recharge from the front of the mountain and enter the aquifer through karst fissures through the overlying strata, the differences in the overlying strata lead to different hydrochemical characteristics. This indicates that the mineral dissolution in the overlying strata is the main factor in the formation of the hydrochemical composition of Pingliang karst water.
, Available online  
Abstract: