Temporal and spatial distribution, sources and health risk assessment of trace elements in a typical karst river basin in Southwest China: Influence of acid mine drainage from abandoned coal mines.

Geochemical behaviour and health risks of trace elements in karst water systems: Role of allogenic water in mitigating contamination.

The drainage of groundwater in mountainous tunnel projects always leads to substantial decline of the regional water table, which may induce numerous environmental issues, such as spring depletion, surface subsidence, vegetation degradation, and impacts on local water supplies, especially in the enclosed karst aquifers of anticlines in the area, such as the Jura mountain type. A systematic hydrological monitoring was conducted during the excavation of the Wufu Tunnel in Chongqing, China. The monitoring data includes discharge rate and water level collected from tunnels, boreholes, coal mines, springs, and ponds, respectively. Hydrological responses of karst aquifers and surface water bodies to tunnel drainage and precipitation were investigated by statistical analysis, Mann–Kendall test, heat map, and wavelet analysis. Results show that the enclosed karst water system has strong hydraulic connections and good water storage conditions. Tunnel drainage is the dominant factor causing dynamic changes at monitoring points, while the influence of rainfall is relatively limited. Borehole water levels and coal mine drainage have a close correlation with tunnel inflow, while springs are influenced by both rainfall and tunnel drainage. Few pond monitoring points are related to rainfall. Tunnel drainage has transformed the regional groundwater dynamic conditions, causing local groundwater flow direction reversal and reconstructing the groundwater recharge-flow-discharge pattern.

There are 23 carbonate karst areas in Albania with a total area of 6440 km2, or 24% of the country’s territory. Karst aquifers are the richest in the country and about 80% of the water supply for the population living in cities is supplied by karst water. One of the most interesting karst massifs of Albania is called Mali me Gropa (MMG) with a total surface area of 157 km2. It is the subject of this paper. Although this massif has attracted attention due to its exceptional development of surface karst landforms (karst pits, sinkholes, swallow holes) and its large and high-quality groundwater resources, it has not been the subject of comprehensive research. In this paper, for the first time, is a summary of the results of a combination of specialized studies, including geomorphological characterization, analysis of long-term groundwater regime observations in relationship with meteorological data, water balance studies applying the recently developed WaterbalANce software method, assessment of groundwater quality and its variability, determination of the groundwater flow velocity with an artificial tracer, and the use of hydrochemistry and runoff data to determine groundwater flow patterns and sensitivity of spring water to contamination. The results of the multi-method studies conducted on the MMG karst massif will inform future studies of the numerous carbonate karst regions in Albania. A final important objective of this article is to raise public awareness about the vulnerability of karst waters and the need to protect the associated ecosystem, especially now that the MMG karst massif is in the spotlight for tourism development.

Professor Ira Sasowsky is Professor of Geosciences at the University of Akron, USA, who has made many outstanding scientific contributions to the karstological community in karst hydrogeology, geomorphology, geochemistry and dating. He completed his undergraduate studies in geology at the University of Delaware and defended his doctoral thesis at Pennsylvania State University. He is known by his colleagues and students for his broad knowledge and experience gained during his extensive field work early in his career in oil fields and later in various parts of the world (Brazil, Croatia, Italy, Slovenia, Spain, USA). His research focuses on groundwater flow in carbonate aquifers, sediment transport and palaeomagnetic dating of cave deposits. He has authored numerous scientific papers and book chapters, edited several scholarly volumes and mentored many undergraduate and graduate students. He has received many honours, to name just few of them: Outstanding Teacher Award (Eastern Section American Association of Petroleum Geologists), Science Award (National Speleological Society), Distinguished Service Award (Geological Society of America, Hydrogeology Division), Presidential Citation (Association of Environmental and Engineering Geologists), and Service Recognition Award (Karst Waters Institute). Prof Sasowsky is active in many geoscience professional organisations in the USA and abroad.

The karst area is a typical ecologically fragile and soil erosion area. The agroforestry derived from soil and water conservation plays an important role in its ecological restoration and sustainable development.However, research on the value realization mechanisms and paths for agroforestry ecological products in karst soil and water conservation remains limited. In this study, three typical karst demonstration areas of Bijie Salaxi, Guanling-Zhenfeng Huajiang and Qingzhen Hongfenghu were taken as examples to create an ecological product classification system.Employing methods such as ecological product value accounting and spatial analysis. It evaluates the GEP across these regions and conversion rate, revealing the realization mechanisms and paths under a multi-stakeholder approach.Results indicate: The Salaxi study area recorded total GEP of 679.1433 million yuan, with a total value conversion rate of 15.12%. Huajiang GEP was 403.7665 million yuan, with a total value conversion rate of 13.65%. Hongfenghu GEP: 495.8981 million yuan, total value conversion rate is 19.12%. All three study areas exhibited the highest value in regulating services and the lowest in cultural services. Moreover, the conversion rates of total ecological product value across the three study areas primarily showed the highest conversion for material products, while conversion rates for regulating and cultural services remained relatively low. Current value realization still relies predominantly on traditional agricultural products, with the market potential of regulating and cultural services yet to be fully tapped. This study not only enriches the theoretical framework for value realization mechanisms and pathways of ecological products in soil and water conservation but also provides scientific reference for implementing the “Two Mountains” theory in ecological protection and sustainable development within karst soil and water conservation areas.

Earthquakes are among the most catastrophic natural disasters, primarily due to their immediate potential to cause loss of human life. However, their impact extends beyond the initial seismic event, particularly in karst systems, where groundwater resources are highly sensitive to geodynamic disturbances. The abundance of karst springs within these terrains makes them critical water sources for many communities, yet earthquakes can significantly disrupt their discharge patterns and degrade water quality. This study examines the vulnerability of karst springs to seismic activity, focusing on two case studies that illustrate distinct earthquake-induced hydrogeological effects. The first case investigates the temporary failure of the Opačac Spring near Imotski, Croatia, following the Mw 3.7 earthquake on 7 September 2018. This spring experienced a complete cessation of discharge for four days, as recorded by continuous hydrograph monitoring, before recovering due to the release of accumulated groundwater behind a temporarily blocked conduit. The second case explores the impact of seismic activity on water quality, focusing on the sensitive freshwater lens of the karstic Island of Vis in response to the Mw 6.1 earthquake on 22 April 2022, near Stolac, Bosnia and Herzegovina. Despite the epicenter being over 150 km away, water quality monitoring revealed notable changes, emphasizing the influence of seismic disturbances on fragile groundwater systems in carbonate island environments. Using a multidisciplinary approach, integrating seismic data analysis with hydrological and hydrogeological observations, this study investigates the mechanisms through which earthquakes alter karst water systems. A proposed vulnerability assessment framework is introduced, aiming to correlate earthquake intensity, proximity, and hydrogeological response to better predict karst spring failure and water quality degradation. This model provides valuable insights for disaster preparedness, water resource management, and risk mitigation strategies in karst terrains, highlighting the necessity of incorporating karst hydrogeology into regional earthquake response planning.

Karst groundwater is widely distributed in China, and karst water resources are the main source of water for human life, industry, and agriculture. To scientifically understand and rationally exploit karst groundwater, it is necessary to analyze the runoff conditions of karst groundwater. This study comprehensively applied statistical methods, Shukalev classification, reverse hydrogeochemical modeling, and Kriging interpolation in ArcGIS to analyze the hydrochemical characteristics and runoff conditions of the three karst groundwater runoff belts in the Fengfeng mining area. The results show that: (1) The hydrochemical type in the study area is mainly HCO3·SO4-Ca·Mg type, and the eastern region changes greatly, while the western region changes little; (2) The chemical reactions and water-rock interactions occurring during the flow of groundwater in different runoff belts of the study area are different; (3) The runoff conditions derived from hydrogeochemical methods are consistent with existing geological data, indicating that this method is suitable for identifying groundwater runoff conditions. In this study, the hydrogeochemical reaction of karst groundwater in the flow process is quantitatively evaluated from the spatial point of view, and the runoff conditions of different runoff belts are analyzed, so as to provide new methods and new ideas for the determination of groundwater runoff conditions.

Influence of ion concentration in karst water on calcium leaching from cement hydration products: A molecular dynamics and metadynamics study

Integrating multiple methods to identify groundwater runoff characteristics in karst water inflow areas of an underground pumping station in North China

Karst structures significantly impact the environment and engineering projects. The presence of water-bearing karst structures alters the shallow stratigraphic temperature field. The shallow temperature measurement method offers a simple and efficient approach to obtain shallow ground temperature data, enabling the inference of karst structure distribution through temperature anomalies. In this study, the feasibility of using shallow thermometry to detect karst pipeline structures was investigated via numerical simulation at the Hongsheng Coal Coking Plant and its surrounding sites in Panzhou City, Guizhou Province, China. The results indicate that variations in the burial depth of karst structures markedly influence shallow stratum temperatures. For a single karst conduit with an equivalent diameter of 0.5 m and water temperature of 12 °C, the detectable depth limit is approximately 66 m. Although an increase in the effective flow cross-sectional area affects shallow stratigraphic temperatures, changes in equivalent diameter under the site-specific conditions alter the temperature at 2 m depth by less than 0.02 °C, making it difficult to identify the effective flow cross-sectional area using shallow thermometry. Variations in fluid temperature within a certain range (12–18 °C) also affect shallow ground temperatures, with the influence of lower-temperature fluids being more pronounced. This study provides a rapid, cost-effective, and relatively accurate method for investigating subsurface karst structures, offering important implications for related engineering applications.

Slovenia is among the few countries where the olm, Proteus anguinus, is found, with its habitat largely coinciding with Natura 2000 sites. In these regions, various agricultural and food-processing activities, including the dairy industry, have developed. Krepko, a dairy facility, is situated directly within the olm’s habitat. Current legislation prohibits the direct discharge of dairy wastewater into the environment and mandates prior treatment. This study examined the primary treatment phase, specifically the chemical processing steps of neutralisation, coagulation, and flocculation. Field jar tests, pH measurements, and laboratory analyses of chemical oxygen demand (COD) were employed to assess the effectiveness of various chemicals. The findings indicate that sodium hydroxide with higher molarity enables faster and more stable neutralization, while polyaluminum coagulants and acidic flocculants are more effective than traditional reagents in reducing COD. The optimised chemical treatment process substantially reduced the organic load of wastewater and, consequently, the potential impacts on karst habitats. The improved treatment system represents a significant advancement in reducing pressure on karst water resources and protecting the habitat of the olm, thereby contributing to the achievement of the United Nations Sustainable Development Goals, particularly SDG 6 (Clean Water and Sanitation), SDG 12 (Responsible Consumption and Production), and SDG 15 (Life on Land).

Understanding the occurrence and genesis of groundwater is vital for management and utilization. This study examines the hydrogeochemical characteristics and influencing factors of groundwater around Ji’an City, southern China, with 235 groundwater samples collected from pore, fissure–pore, karst, and bedrock fissure aquifers. Methods such as multivariate statistical analysis, Piper plot, Gibbs plots, and ion ratio coefficient were used for data analysis. Results indicated that groundwater hydrochemical types primarily were HCO3-Ca, HCO3·Cl-Na·Ca, and HCO3-Na·Ca. The TDS and pH values ranged from 139.92 to 329.66 mg/L and from 4.7 to 8.5, respectively, indicating freshwater with a weakly acidic to neutral nature. Groundwater composition was shaped by a combination of rock weathering/dissolution, cation exchange, and anthropogenic activities. Karst water was notably affected by carbonate rock weathering/dissolution, whereas bedrock fissure water was primarily influenced by silicate rock weathering. Human activities showed a minimal impact on karst and bedrock fissure water, while pore and red-bed fissure–pore water were significantly impacted. The contributions of natural and anthropogenic input to groundwater chemistry were constrained by PCA, showing the rate was 78.09% 15.79%, respectively. Our findings provide insights into the distinct hydrogeochemical processes within different aquifer systems, contributing valuable data and methodologies for groundwater research and management in multi-aquifer systems.

Abstract. The interaction mechanism between karst aquifers and streams remains unclear, particularly regarding the impact of dynamic groundwater saturation processes under variable precipitation. This challenge hinders the accurate modeling of karst hydrology. This study developed a Darcy–Brinkman–Stokes model to analyze these complex interactions. The model integrates water-air two-phase flow and employs multiple water retention models to characterize variably saturated flow in porous media. We validated the DBS approach by comparing its numerical results against the MODFLOW-Conduit Flow Process v2 for generalized karst models. The key conclusions are as follows: Rainfall intensity is the dominant driver of the interaction. Higher intensities lead to more complex processes, involving multi-media collaborative recharge and shifting discharge contribution ratios from different media. During consecutive rainfall events, groundwater stored in porous media (matrix) significantly influences subsequent stream levels, whereas conduit storage shows negligible carry-over impact due to rapid drainage. Uncertainty analysis demonstrated that conduit geometry, epikarst permeability, and matrix porosity differentially influence system hydrology, controlling the magnitude, timing, and distribution of peak discharges. The validated DBS model is a robust tool that accurately depicts the complex two-phase interactive flows (including infiltration, overflow, and recession) controlled by dynamic saturation. It successfully reveals the dynamic interactions between the epikarst, conduits, matrix, and stream, which is essential for understanding and managing karst water resources.

Abstract Karstic systems supply more than a quarter of the drinking water needs in the world, yet modeling these aquifer systems is constrained by their complexity and the extensive data requirements. Advances in data collection technologies enabled access to high-resolution hydrogeological data, but gaps in these datasets continue to limit their utility. To address this challenge, this study introduces a novel hybrid methodology that integrates self-organizing maps (SOM) and bidirectional long short-term memory (Bi-LSTM) networks to impute missing water level intervals and forecast future water levels in karstic systems. The feasibility of the proposed approach is demonstrated through its successful application in analyzing the spatiotemporal dynamics of karst water levels in the Bükk Mountains, Northern Hungary. Initially the Bi-LSTM model was employed to impute missing intervals in the precipitation and water level datasets. The SOM analysis revealed that spring water levels are correlated with precipitation, reflecting immediate recharge dynamics. In contrast, the wells displayed a delayed response due to slower recharge processes. Subsequently, the SOM features, including grid coordinates and distances, were incorporated into the Bi-LSTM model to add contextual information and improve its predictive capability. To assess the reliability of the forecasts, a bootstrap uncertainty analysis was conducted. This enabled reliable prediction and forecasting of karst water levels, achieving predictive accuracy exceeding 92% while also providing estimates of potential uncertainty. The overall trend of the forecasted water levels showed spatial variability, with most monitoring stations exhibiting increasing trends and gradual decline observed at one site, underscoring the importance of site-specific management.

This study used the Tenglong Coal Mine in northern Guizhou as a case study to prevent or control bed separation water disasters caused by complex hydrogeological conditions in karst mining areas. A systematic research approach integrating theoretical modeling, quantitative monitoring, and on-site prevention and control was used to analyze the dynamic evolution of overburden separation in karst areas and establish a prevention system. The rock mechanics theory was used to identify the location of bed separation and establish a mechanical model of the roof containing a conical funnel-shaped karst cave. The cusp catastrophe theory was applied to derive a safety distance criterion between the karst cave and the separation zone. The box-counting fractal dimension (D) was used to quantify the dynamic evolution of the separation. It was 1.1881 after the working face reached 240 m, and the maximum separation was 2.64 m. A similarity simulation was conducted, and fiber Bragg grating (FBG) sensors and digital image correlation (DIC) were employed to measure the separation space. A site-specific system was developed to analyze bed separation water disasters, perform spatiotemporal prediction, and prevent or control them. The following was observed. (1) The higher the karst water pressure, the higher the load, and the thinner the rock layer, the more prone the area was to water inrush disasters. (2) The fractal dimension accurately described bed separation. Bed separation became critical when D exhibited a sudden step-like increase above 1.15. (3) A strong positive correlation existed between the strain and the separation ratio F. The maximum subsidence of high-level separation derived from DIC was 10.5 mm, and the highest bed separation position occurred beneath the thick Changxing Formation limestone. (4) The proposed surface and underground drainage approach improved the drainage efficiency. This research provides theoretical support and technical guidance to prevent or control bed separation water disasters in karst mining areas.

Nitrogen response and transformation processes in karst water system using bacterial indicators

ABSTRACT In karst ecosystems like the Gaoping River Basin (Zunyi, Guizhou Province, China), widespread evaporite deposits and exogenous acids inputs drive a shift in water chemistry from carbonate-dominated to sulfate-dominated regimes. Characterizing sulfate ( SO 4 2 − ) sources and spatiotemporal dynamics is critical for managing vulnerable karst water resources. This study uses hydrochemistry, sulfur–oxygen ( δ 34 S S O 4 , δ 18 O S O 4 ) , and water (δD, δ 18 O H 2 O ) isotopes, combined with the SIAR model, to trace SO 4 2 − sources across river reaches and hydrological seasons. Results show that sulfate in the Gaoping River originates from both natural and anthropogenic sources: In the upstream, water–rock interactions during groundwater (GW)–surface water (SW) recharge drive gypsum dissolution in carbonate formations, contributing 20.9–21.7 % of SO 4 2 − in SW and 20.7-30.4 % in GW. In midstream, where agricultural land use dominates, soil-derived sulfate becomes the primary source, accounting for 23.3–25.8 % (SW) and 24.6–28.3 % (GW), correlated with land-use intensity. In downstream, intensive human activities (sewage discharge, fertilizer application) elevate anthropogenic inputs, with sewage contributing approximately 20.1 % to SO 4 2 − loads in both SW and GW, and fertilizer inputs accounting for 24.0 %. The SIAR model confirms a transition from geogenic (gypsum, soil sulfate) to anthropogenic dominance downstream, with overall water chemistry shifting to a HCO3·SO4-Ca type, indicative of carbonate-to-sulfate evolution. These findings underscore the interplay between karst geology, land use, and hydrological processes in shaping sulfate budgets. The study provides a data-driven framework for targeted management: protecting upstream gypsum outcrops, optimizing midstream agricultural practices, and improving downstream wastewater treatment, thereby advancing sustainable karst water resource management in vulnerable ecosystems.

Clarifying the mechanism of grouting to block karst water outbursts is essential for ensuring effective sealing. This article studies the grouting blocking problem related to the prevention and control of water surge disasters in karst tunnels, focusing on the grouting blocking mechanism of efficiently plugs expanding material (EPEM) under dynamic water conditions. We propose a grouting diffusion formula and blocking criterion that take into account the self-expanding properties of the slurry. First, based on the equilibrium relationship between the friction force and anti-splitting force between the blocking body and the rock wall, we establish an effective blocking condition. Second, by combining capillary theory with Newton’s fluid constitutive equation, we derive the diffusion distance formula for self-expanding slurry under dynamic water conditions. We then construct a mechanical model that uses the length of the critical blocking body as a criterion, revealing the coupling influences of groundwater pressure, grouting pressure, and grouting time. The results indicate that groundwater pressure is positively correlated with grouting pressure and grouting time, while grouting pressure is negatively correlated with grouting time. Finally, we verify the practicality of the proposed criterion through the project at Quanmutang Reservoir in Hunan Province, successfully implementing a parameter combination of 0.5 MPa grouting pressure and 20 min of grouting time to block surge water. This research provides a theoretical basis and engineering guidance for designing water surge grouting in karst tunnels.

Karst formations in Albania cover an area of 6750 km², which represents 24% of the country's territory. The country has 110 karst springs with discharges exceeding 100 litters per second. Among these, Bistrica springs stands out as the largest, with an average discharge of 18.4 cubic meters per second. This study focuses on the Southern Mountain Region of Albania, known for its important karst water resources. In this region, 12 karst springs are protected due to their essential natural, scientific, educational, aesthetic and economic value. The objective of this research is to perform a geoinformatics analysis and evaluation of these protected karst resources. To achieve this, we collected extensive literature on protected springs, as well as reach data about the protected springs of the study area and analysed them using ArcGIS 10.1 software to generate geoinformation about these resources. This geoinformation includes a wide range of geographic and geologic-hydrogeological data. We aim to improve the understanding and promotion of protected karst resources in the Southern Mountain Region of Albania