Karst Water Research Articles

Monitoring Direct Current Resistivity During Coal Mining Process for Underground Water Detection: An Experimental Case Study

Karst water may break into coal tunnels through the rock fissures and cause severe coal mine disasters. The direct current resistivity (DCR) is sensitive to underground water and can be used to detect fissures during the coal mining process. However, the three-dimensional (3D) measurement of the DCR is still a challenging task and has not been applied to the practical coal mining dynamic process. To bridge this research gap, this study proposes a new 3D cross-borehole method by monitoring the direct current resistivity at multiple points to analyze the geoelectrical field evolution in the underground coal mining process. Based on forward and inversion theoretical analysis, a DCR observation system is developed for a real unground coal mine to evaluate the cross-borehole points. The 3D resistivity distributions at different positions in the coal mining process are calculated. The analysis result demonstrates obvious resistivity changes with the evolution of the Karst water zone during the coal mining; and the location and movement of the Karst water can be well estimated. As a result, the proposed 3D cross-borehole method is very effective for monitoring the DCR and is able to accurately detect the underground water.

Hydrogeology of alpine lakes in the Northern Calcareous Alps: a comparative study on the role of groundwater in Filblingsee and Eibensee

Abstract In the Northern Calcareous Alps (NCA) there are countless small lakes with small orographic catchments that are often located only slightly below the respective summit regions. On the one hand, the lakes are located in karstable aquifers and their existence is likely to be related to karstification. Then, they are expected to be directly connected to the karst water body. These lakes are classified as karst lakes. On the other hand, the alpine environment is also influenced by glacial processes and lakes might be related to glacial erosion and deposition. For these glacial lakes, the share of groundwater inflow and outflow is regarded as subordinate even within high permeable karst lithologies. Here we compare two alpine lakes of potentially different origin in the NCA in Salzburg with the aim to provide a basis for an aerial survey of the numerous small alpine lakes in the NCA region and their characterization using the guiding parameters elaborated here. We consider (a) the lake geometry, (b) potential inflow and outflow systems, and (c) physicochemical parameters and hydrochemistry of the Filblingsee and the Eibensee, both located in the Fuschlsee region. Filblingsee was initially considered as a typical karst lake and Eibensee as a moraine-dammed glacial lake. Some clear differences arise in lake geometry, which in the karst lake shows a nearly round surface and concentric depth profile, while the glacial lake is elongated in the direction of glacier flow and has the deepest areas just upstream of the moraine dam. Both lakes show very little to no surficial inflow. Inflow and outflow occur in groundwater in both cases but are not directly tied to a highly permeable karst system. The depth profiles of the field parameters of the two lakes differ only slightly and show a dominant groundwater inflow in mid-depth regions but no flow through at the lake bottom. Water chemistry in both lakes and their potential outflows correspond to the respective aquifer in terms of solution load. Filblingsee can be characterized as a hanging lake in a secondarily sealed doline, Eibensee lies in a glacially excavated depression sealed by glacial sediments. While the inflow and outflow conditions and the hydrochemistry of both lakes are very similar, the lake geometry is a clear distinguishing feature that can be attributed to the different genesis of the two lakes. This can therefore be used as a guiding parameter for the classification of the numerous small alpine lakes in the NCA.

Accelerated Corrosion Behaviour and Microstructure of Alkali-Activated Slag in Karst Water Solution

Accelerated Corrosion Behaviour and Microstructure of Alkali-Activated Slag in Karst Water Solution

ЕВОЛЮЦІЯ ТА САМООРГАНІЗАЦІЯ КАРСТОВИХ ГІДРОГЕОЛОГІЧНИХ СИСТЕМ СОЛЯНИХ РОДОВИЩ КАРПАТСЬКОГО РЕГІОНУ

It has been established that hydrogeological systems in the conditions of the technologically altered geological environment of the salt deposits of the Carpathian region (Stebnytskyi, Kalush-Holinskyi, Solotvynskyi) behave as typical dissipative systems capable of evolution and self-organization. The evolution of karst hydrogeological systems consists in their genesis associated with the beginning of inflows of karst waters into mining productions, the successive growth of their aggressiveness and flow, the activation of karst collapse phenomena, undercutting of walls in mines and sides in quarries, self-isolation of exits of easily soluble minerals and suppression of man-made activated karst, up to complete cessation when salt-snow deposits are completely flooded. Selforganization of karst hydrogeological systems occurs through a cyclic change of four stages: 1) leaching of easily soluble minerals in an aggressive environment; 2) release of poorly soluble and insoluble components; 3) inhibition of leaching due to temporary blocking of easily soluble minerals by a protective layer of the released insoluble residue of terrigenous and poorly soluble minerals; 4) erosion-corrosion disintegration of the protective layer with a cyclical transition to stage 1. The established regularities of the evolution and self-organization of karst hydrogeological systems make it possible to predict the state of mining massifs disturbed by mining operations and salt karst, as well as to propose scientifically based solutions geoecological problems

Hydrological Modeling of Karst Watershed Containing Subterranean River Using a Modified SWAT Model: A Case Study of the Daotian River Basin, Southwest China

Karst watershed refers to the total range of surface and underground recharge areas of rivers (including subterranean rivers and surface rivers) in karst areas. Karst water resources, as the primary source of domestic water supply in southwest China, are vital for the social and economic development of these regions. It is greatly significant to establish a high-precision hydrological model of karst watershed for guiding water resources management in karst areas. Choosing the Daotian river basin in the Wumeng Mountains of Southwest China as the study area, this paper proposed a method for simplifying karst subterranean rivers into surface rivers by modifying the digital elevation model (DEM) based on a field survey and tracer test. This method aims to solve the inconsistency between the topographical drainage divides and actual catchment boundaries in karst areas. The Soil and Water Assessment Tool (SWAT) model was modified by replacing the single-reservoir model in the groundwater module with a three-reservoir model to depict the constraints of multiple media on groundwater discharge in the karst system. The results show that the catchment areas beyond topographic watershed were effectively identified after simplifying subterranean rivers to surface rivers based on the modified DEM data, which ensured the accuracy of the basic model. For the calibration and two validation periods, the Nash–Sutcliffe efficiencies (NSE) of the modified SWAT model were 0.87, 0.83, and 0.85, respectively, and R2 were 0.88, 0.84, and 0.86, respectively. The NSE of the modified SWAT model was 0.09 higher than that of the original SWAT model in simulating baseflow, which effectively improved the simulation accuracy of daily runoff. In addition, the modified SWAT model had a lower uncertainty within the same parameter ranges than the original one. Therefore, the modified SWAT model is more applicable to karst watersheds.

Recharge sources and hydrogeochemical evolution of groundwater in a heterogeneous karst water system in Hubei Province, Central China

Although numerous studies on hydrogeochemistry in karst catchments have been performed, some challenges in understanding their hydrogeochemical behavior remain due to the unique architecture of karst groundwater systems and the high heterogeneity of the karst medium. Here we used a multicriteria approach combining hydrodynamic, hydrochemical, and stable isotopic tools to investigate the impact of heterogeneity on karst hydrogeochemistry in a mountainous area of Hubei Province, Central China. Our results showed that groundwater was dominated by Ca2+, Mg2+, HCO3−, and SO42−, and typically characterized by HCO3–Ca·Mg type in the shallow aquifer and by SO4–Ca·Mg type in the deep aquifer. With increasing circulation depth, water-rock interactions and the heterogeneity of the karst medium produced water with increased Ca2+, Mg2+, Sr2+, and SO42− concentrations, and also increased the dissolved total solids. Calcite, dolomite, and gypsum dissolution in local and intermediate flows were important geochemical processes in groundwater evolution, and calcite precipitation occurred in the regional flow due to dedolomitization, supported by PHREEQC modeling of minerals. The decreased major ions and increased nitrate with increasing δ18O due to the dilution of shallow groundwater by high δ18O recharge and nitrogen fertilizer required during the summer rainy season were found relying on Plots of δ18O vs major ions, which offer an alternative approach to learn seasonal effects of hydrogeochemistry. All advances presented were integrated into a hydrogeochemical conceptual model, including local, intermediate, and regional flows, hydrogeochemical evolution, horizontal and vertical karst zones, hydrochemistry, and stable isotopes of groundwater, providing a typical model for multiple karst groundwater systems in Central China.

Multi-Step Combined Control Technology for Karst and Fissure Water Inrush Disaster During Shield Tunneling in Spring Areas

Shield tunneling in highly fractured karst water-rich conditions easily results in water inrush disaster or even causes the roof of the karst caves to collapse. Severe water inrush disasters have occurred during the EPB (earth pressure balance) shield machine of the Jinan Metro Line R1 advanced through a karst and fissure groundwater-rich limestone ground in the spring area. To cope with the extreme water inrush risk, a multi-step combined control technology was put forward. First, a detailed geological exploration was carried out by ahead geophysical prospecting using high-density resistivity method, geological radar, etc., and geological borehole drilling was conducted from the ground surface before excavation. As a result, the distribution orientation, size, fissure development degree, and water inflow channel within the surrounding rock of the karst caves were detected. Second, multi-step grouting was performed to reinforce the surrounding rock, including pre-grouting treatment and filling rock blocks to the big karst caves from the ground surface, multiple grouting with a small amount of inert slurry each time inside the tunnel, and secondary circumferential hoop grouting at the shield tail. Third, the tunneling process was optimized, including optimizing the tunneling parameters, making full use of the air-pressurized tunneling technology of the EPB to press bentonite into the fractures around the excavation cabin to seal the fissure water, and using the drainage system of EPB and muck improvement technology to reduce the water inrush disaster. Meanwhile, shield protection slurry technology is applied to cutter inspection and replacement in the pressurized chamber under dynamic water flow environment of the spring terrain. The practice shows that the water inrush on the tunnel face is obviously alleviated after the shield machine advanced into the grouting area. According to statistics, the water inflow on the tunnel face decreases from about 4 m3/h before treatment to less than 0.3 m3/h after the abovementioned control, and the water seepage between the segmental linings reduces to almost zero. The average advance rate increased from 3 m/day without stopping or even zero when the shield machine needs to shut down 2–3 days for drainage to about 6 m/day. In addition, the treatments prevented the shield machine from jamming and the head descending disaster. This study provided a reliable control method for shield tunneling through the karst and fissure water-rich area and played an essential role in protecting the spring water.

On the Role of Density‐Driven Dissolution of CO2 in Phreatic Karst Systems

AbstractDensity‐driven dissolution of carbon dioxide in water is a well‐known and much described mechanism in geological sequestration of this greenhouse gas. It is remarkable that such enhanced dissolution does not receive attention in karst hydrology and speleology. Models and hypotheses on karst development are complex and consider many different processes. We focus here on the influence of CO2 partial gas pressures at the interface between atmosphere and karst water on the dynamics of dissolved CO2 concentrations below the water table. Seasonal variations of microbial soil activity and root respiration or barometric‐pressure changes cause fluctuations in CO2 partial pressures. Dependent on the existence and strength of a karst‐water background flow, fingering regimes might be triggered causing enhanced dissolution of CO2. This allows replenishment of CO2, and, thus, dissolutional power even deep in the water body without the need for percolating water to transport dissolved CO2. We present and discuss simplified and generic experimental and computational scenarios to strengthen our claim, and we try to give answers to: how much? and under which circumstances? The applied numerical model solves the Navier‐Stokes equation with water density dependent on CO2 concentration and temperature. We show that calculated CO2 mass fluxes into the water bodies are dependent on the ratio of Péclet to Rayleigh numbers (Pe/Ra) and show a local minimum around Pe/Ra = 1, i.e. when natural and forced convection are about equal. Concluding, we claim that there is sufficient reason to consider density‐driven dissolution as a process of relevance in karstification if circumstances are given.

New Data on Hydrogeochemical and Isotopic Composition of Natural Waters of the Baidar Valley (Crimean Peninsula)

Abstract —Results of study of natural waters of the Baidar valley (southwestern Crimean Peninsula) obtained during the 2018–2019 field works are presented. Major groundwater resources of the study area are confined to the Upper Jurassic aquifer complex, which serves as a recharge source for the aquifer systems of the Plain Crimean and the Azov–Kuban’ artesian basins and hydrogeologic folded region of the Crimean Mountains mega-anticlinorium. The regional waters are fresh and ultrafresh, predominantly of calcium bicarbonate composition, with TDS varying from 208 to 1269 mg/dm3. The study enabled their classification into eight geochemical groups: (1) waters of a regional fracture zone in carbonate-terrigenous rocks affected by continental salinization; (2) waters of a regional fracture zone affected by leaching of aluminosilicates and sulfide oxidation; (3) waters of a regional fracture zone dominated by sodium aluminosilicates in the fracture filling (long-term interaction in the water–rock system), affected by continental salinization; (4) regional fracture zones dominated by sodium aluminosilicates affected by anthropogenic continental salinization; (5) groundwaters in fracture–vein aquifers affected by leaching of aluminosilicates and sulfide oxidation; (6) fracture–vein aquifers affected by leaching of sodium aluminosilicates (long-term interaction in the water–rock system); (7) waters in fractured karst aquifers; and (8) surface waters subjected to continental salinization. Fracture karst waters, which were found to be most protected against human impact and continental salinization processes, are slightly alkaline (pH = 7.7), fresh (with average TDS = 444 mg/dm3), with low silicon concentrations (2.23 mg/dm3), and of calcium bicarbonate composition. Waters residing in regional fracture and fracture–vein zones are affected by continental salinization and anthropogenic load and are neutral to alkaline (pH = 7.1–8.6), predominantly fresh (TDS = 269–1269 mg/dm3), with average silicon concentrations of 4.61–4.70 mg/dm3, of calcium bicarbonate composition, with high concentrations of sulfate ion, magnesium, and sodium. The waters of the Chernaya River, Chernorechensk reservoir, and lakes, which are also affected by continental salinization, are slightly alkaline (pH = 8.3), brackish (TDS = 207–364 mg/dm3), with an average silicon concentration of 1.18 mg/dm3, of calcium bicarbonate composition, with high concentrations of chlorine ion, magnesium, and sodium. The calculated intensity of chemical-element migration in waters of the background composition follows the descending order: very strong, I17.7 > Br14.4; strong, Se2.83 > B2.22 > Sr1.46 > Sb1.12 > Be1.07 > Hg1.06; moderately strong, Zn0.74 > Mo0.50 > Li0.46 > Sc0.41 > Ag0.18 > As0.16 > Si0.123 > Ba0.122; weak, Cr0.10 > Cu0.096 > Bi0.080 > Sn0.068 > Tl0.067 > P0.062 > Ni0.043 > Ta0.040 > Ge0.034 > Cd0.028 > Fe0.026 > Rb0.024 > Co0.023 > Pb0.020 > W0.017 > V0.012; very weak (inert), Nb0.008 > Hf0.0033 > Mn0.0031 > La0.0029 > Cs0.0022 > Ti0.0018 > Ga0.0016 > Y0.0013 > Al0.0008 > Zr0.0008. All the studied waters are found to be of atmospheric origin and located along the global (GMWL) and local (LMWL) meteoric water lines. Their δ18O value varies from –9.9 to –3.3‰, and δD value, from –64.2 to –32.5‰. Sedimentary carbonate rocks, atmospheric carbon dioxide, organic compounds, and hydrolysis of aluminosilicate minerals serve as the source of δ13C bicarbonate ion in natural waters of the Baidar valley. Surface waters have a heavier carbon isotope composition (δ13C = –9.2 to –6.2‰), which is due to atmospheric CO2, plant growth, and associated microbial activity. Fracture karst waters are characterized by a lighter carbon isotope composition (δ13C = –12.8 to –11.0‰) because of their interaction with dispersed organic matter. Waters of the regional fracture and fracture–vein zones display the widest variation in δ13C (–15.5 to –6.9‰), which is associated with a mixed type of “isotope supply” to the waters. A complex hydrogeochemical field that has formed in the Baidar valley tends to be increasingly affected by the anthropogenic factor.

Temporal and spatial evolution characteristics of fracture distribution of floor strata in deep coal seam mining

With the increase in mining coal seam depth year by year, the high-pressure karst water hazard of coal seam floor poses a serious threat to mine safety. To solve this karst water disaster beneath the coal seam floor, it is necessary to Prevention-control the water-conducting passages developed in coal seam floor strata. Therefore, mathematical model analysis and Brillouin optical time domain reflection technology (BOTDRT) were used in this study to monitor the microstrain of floor rock in deep coal seam mining, and other methods were used to elucidate the mechanism of floor failure in deep coal seam mining. The results show that the maximum depth of floor rock breakage in coal seam mining is near the peak stress propagation line in front of the coal wall of coalface and reveals the stacking uplift of floor rock in goaf. Based on the measured data of preburied metal cable-based distributed optical fiber sensor (MCDOFS), the time–space evolution characteristics of floor breakage in coal seam mining and the law of floor breakage were revealed more finely. This study provides a basis for the prevention and control of high confined water hazard of limestone in a coal seam floor in deep seam mining.

The controlling factors of the karst water hydrochemistry in a karst basin of southwestern China

The controlling factors of the karst water hydrochemistry in a karst basin of southwestern China

Investigation on pollution sources of a Karst Underground River in southwest Guizhou

by means of karst hydrogeology investigation, pollution source investigation, water pollution status investigation, water quality sampling and detection, The water pollution of large karst underground river in Muerdong of southwest Guizhou Province was investigated and demonstrated. The analysis shows that:(1) the catchment area of groundwater unit in Muerdong-qingping River is about 270 km2, and there are many karst pipelines in the area, and finally discharge at the exit of the underground river at the lowest discharge datum level in the area. (2)there are mainly four replenishment subsystems in the underground river, it is found that the karst water system of Dajiang and Tanping river is finally discharged through the Q4, Q5 and Q6 karst springs or the underground river of Muerdong River, and neither the spring water nor the underground river is polluted, the outcrops of Yangjiaba Karst water system and Bayan karst water system in Muerdong underground river are Q1, Q2 And K35. The spring water and groundwater in the cave are polluted (3) the main pollution of the underground river of Muerdong is from the excrement of livestock and poultry in DK farm in the karst water system of yangjiaba, which is discharged into the underground pipeline of the underground karst river through the falling water cave. The water source area of Muerdong underground river is located in the strong karst area, the geological environment is fragile, and the suitability of developing large-scale aquaculture industry is poor. The government needs to enhance the understanding and use for reference in attracting investment.

The floating karst flow of migrants as a rite of passage through the Eastern European border

ABSTRACT Since the so-called ‘migrant crisis’ in 2015, the Balkan route has resumed its old function as an overland passage from Eastern to Central Europe and the area between Italy and Slovenia has constituted a migratory crossroads towards Northern Europe. In the last two years, there has been a constant increase of rejection policies in Italy and in the Western Balkans that has forced asylum seekers on undercover paths, with stops, blocks, rejections and many attempts to overcome the militarized borders. The article reports the consequences of the new migration policies on the Balkan route toward Italy, with a particular focus on the exclusion and the resistance of migrants that, like karst waters, are changing trajectories and tactics along the road. The Balkans constitute a liminal area where the process of ‘bordering’ is played both by migrants and by European policies. Through the concept of ‘tidemark’ the underground flow of migrants is interpreted as a typical rite of passage with suspended temporality and reflux mobility where the Balkans constitute a ‘waiting room’ and a liminal transit area with a ‘waiting game’ toward Central Europe.

Radiological Risk Assessment for Karstic Springs Used as Drinking Water in Rural Romania

Seasonal variations of the radon and radium activity concentrations in karstic water sources originating in karstic formations were investigated as part of a premiere systematic survey conducted in Romania. A database including a total of 228 drinking water samples collected from 30 distinct water sources adjacent to rural communities was compiled. The radon and radium activity concentrations for all seasons, assessed based on solid scintillation, ranged from 2.1 to 19.7 Bq/L and from 0.6 to 3.0 Bq/L, respectively. Overall, the detected radon and radium contents did not exceed the radioprotection standards recommended by national and European legislation. However, in at least one season, the measured values for 31% of the samples exceeded the 11.1 Bq/L maximum contaminant level for radon in drinking water recommended by the Environmental Protection Agency of the United States. The associated radiological risk, reported in terms of annual effective dose, was calculated to be between 9.8 × 10−6 and 6.0 × 10−5 mSv/y for radon and between 5.9 × 10−5 and 2.7 × 10−4 mSv/y for radium, which are considerably below the WHO (World Health Organization) guidelines at a value of 0.1 mSv/y.

A study of the thermal behaviour of exposed karst water systems in a mountainous area of Zigui County, Hubei Province, Central China

A study of the thermal behaviour of exposed karst water systems in a mountainous area of Zigui County, Hubei Province, Central China

Key problems on hydro-engineering-environmental geology along the Sichuan-Tibet Railway corridor: Current status and development direction

The Sichuan-Tibet Railway is a century project under construction. The complex geological evolution history has led to large differences in geo-environmental conditions along the railway. Hydrogeological, engineering geological, and environmental geological problems are complex and changeable, which deserves great attention in engineering construction and future operations. Based on a brief review of the past geological work on the Sichuan-Tibet Railway corridor, the hydro-engineering-environmental geological problems that may be faced during the railway construction have been described. The hydrogeological problems include 1) high-pressure water inrush from plateau tectonic karst, 2) high-pressure water inrush and mud outburst from faulted bedrock fissures, 3) high-temperature hot water thermal damage. The engineering geological problems include 1) active faults and strong earthquake disasters, 2) high in-situ stress and rock burst or large deformation in deep tunnel, 3) problem rocks or soils and their disaster effects, 4) high-position landslide disaster chain. The environmental geological problems include 1) acidic water corrosiveness from coal-bearing strata and hydrothermal deposits, 2) wetland ecological degradation, 3) interaction effects between the railway construction and the sensitive ecological environment. In the meanwhile, key scientific and technological issues, which should be deeply studied in the future, are put forward. In terms of hydrogeology, such as 1) sequence law of plateau karst development and types of tectonic karst water storage structures, 2) disaster-generating models and prediction methods of water and mud bursts in deep-buried tunnels, 3) active fault control mechanisms and geothermal water circulation models, 4) identification of high-temperature heat hazard risk and geothermal resources utilization technology. In terms of engineering geology and geohazard, such as 1) investigation of fine features of active faults and related engineering fault effects, 2) development features of deep tectonic stress fields in complex geological structures, 3) engineering geological properties of tectonic melange belts and related disaster effects, 4) surrounding rock stability and disaster effects of deep-buried tunnel under water-mechanical-thermal multi-field coupling condition, 5) mechanisms of high-position run-out landslide and risk control technology under internal and external dynamic coupling. In terms of environmental geology, such as 1) mechanisms of plateau multi-source water conversion cycle and the technology of ecological water demand control in the ecologically fragile area, 2) hydro-ecological environmental effect of tunnel construction, 3) key technology of ecological geological environment monitoring, evaluation and protection, 4) geo-ecological environmental effect of global climate warming, etc. From the view of combining non-profit geological surveys and commercial engineering surveys, a response strategy has been proposed that geological surveys are the foundation, scientific and technological research is the key, and the monitoring of potential hazards and engineering control should be promoted, which provides suggestions on developing direction for hydro-engineering-environmental geology work on major project planning areas.

Seasonal Variation and Sources Identification of Dissolved Sulfate in a Typical Karst Subterranean Stream Basin Using Sulfur and Oxygen Isotopes

Karst water, which provides approximately 25% of the world's drinking water, is especially vulnerable to anthropogenic pollutants. To determine the variations between high and low flow periods and the sources of dissolved sulfate (SO42-) in small karst basins, SO42- concentrations, stable sulfur and oxygen isotopes (δ34S-SO4 and δ18O-SO4), and oxygen isotopes of water (δ18O-H2O) were investigated in surface and groundwaters, during the high and low flow seasons, within the Babu subterranean stream basin. Analysis showed that: ① the water samples that were directly impacted by acid mine drainage exhibited high SO42- concentrations (≥250 mg·L-1) and significant seasonal variation, while the seasonal variation of non-AMD-impacted water with low SO42- concentrations was not significant. ② During the high flow season, the mean δ34S-SO4 and δ18O-SO4 values of surface water were -10.5‰ and 4.7‰, respectively, and -11.5‰ and 1.3‰ during the low flow period; the mean values of δ34S-SO4 and δ18O-SO4 in groundwater samples were -2.9‰ and 7.1‰ during the high flow period, respectively, and -3.2‰ and 6.2‰ during the low flow period. Both surface and groundwater samples exhibited higher δ34S-SO4 and δ18O-SO4 values during the high flow period than during the low flow period. ③ The values of δ34S-SO4 in the surface and groundwater samples were relatively stable, indicating that the sources of SO42- at specific sampling sites were stable.④ The main sources of SO42- in surface and groundwaters were rain, sulfide, and gypsum, accounting for 13%, 40%, and 47%, respectively, of SO42- in samples taken from the basin outlet during the high flow season, and 18%, 39%, and 43%, respectively, in samples obtained during the low flow season.

Super-absorbent swellable polymer as grouting material for treatment of karst water inrush

Grouting is the most commonly used method to control water inrush in underground engineering. Traditional cement-based materials are easy to dilute and hard to coagulate under the influence of large flow and high-velocity water inrush. To address these deficiencies, a new type of polymer grouting material with an excellent expansion ratio was synthesised. The material quickly absorbs water and has an expansion ratio of 1:300. The material is composed of a superabsorbent polymer (SAP), glycerol, and ethanol. The effects of water quality on the expansion ratio and expansion rate of the material were examined, and the best solid–liquid ratio for the slurry was determined by fluidity measurements. A karst specially designed pipeline water inrush test device showed that 800 g of SAP can achieve 0.6 m/s water flow blockage in the smooth pipeline, demonstrating that the ability of the SAP slurry to block water inrush is superior to those of other materials. This study provides a reference for water inrush plugging, and has important implications for the reduction and control of karst pipeline-type water inrush disasters, ensuring the safety of construction sites and preventing loss of life and damage to property.

Distribution of Antibiotic Resistance Genes in Karst River and Its Ecological Risk

In recent years, karst water has been polluted by emerging pollutants such as antibiotics. In this study, the bacterial communities and antibiotic resistance genes (ARGs) in antibiotics contaminated karst river was studied in summer and winter. The concentration of antibiotics in winter karst river is higher than that in summer, and there are significant differences in structure of bacterial community and ARGs between karst river water samples. Aminoglycoside, beta-lactamase and multidrug are the main types of ARGs, and transposons play an important role in the spread of ARGs. The horizontal gene transfer (HGT) of ARGs between bacteria mediated by mobile genetic elements (MGEs) would cause the spread of ARGs and bring potential ecological risks. In addition, we found that the risk of antibiotic resistant pathogenic bacteria (ARPB) in winter was possibly higher than that in summer. It was suggested that the discharge of antibiotics, water amount and seasonal occurrence time of human intestinal diseases affect the risks caused by antibiotics contaminants. This study helps us to understand the transmission mechanism of ARGs and their potential seasonal ecological risks in complex karst water systems.

Systematic Triggering of Large Earthquakes by Karst Water Recharge: Statistical Evidence in Northeastern Italy

It is known that surface water accumulation by natural or anthropic causes like precipitation and reservoir impoundment can trigger earthquakes. The phenomenon is amplified and sped up in karst areas, where fracture systems can store large quantities of water and facilitate its percolation to seismogenic depths, increasing both elastic stress and pore pressure on pre-existent faults. The present work explored the possibility that this mechanism had systematically triggered major earthquakes in northeastern Italy, where seismicity is concentrated along the pre-Alpine thrust belt, characterized by the alignment of a series of karst massifs. The time occurrence of damaging and destructive earthquakes (moment magnitude Mw between 4.8 and 6.4) since 1901 was compared with the evolution of the Palmer Drought Severity Index (PDSI), an index of soil moisture that summarizes precipitation and, through temperature, water evaporation. Statistical analysis based on the bivariate Ripley’s K-function shows a significant time correlation between earthquakes and the peaks of PDSI since 1934, with the two strongest earthquakes (1936 Alpago-Cansiglio earthquake and 1976 Friuli earthquake, Mw 6.1 and 6.4, respectively) placed by the two PDSI maxima. The analysis was extended back in time to the last millennium, showing a time correlation between the occurrence of destructive earthquakes (Mw ≥ 6.2) and the peaks of ice extension in the European Alps, assumed as a proxy for groundwater accumulation in the study area. This evidence presented herein coupled with geological characteristics of the area and recent observations on large crustal deformations induced by heavy precipitation suggests that, if PDSI is a valid ground water indicator, karst water recharge may play a role in triggering major earthquakes in northeastern Italy, also relating their occurrence to the large scale climate changes affecting precipitation and evaporation.