Search Results (1,320)

Rural settlements serve as the core spatial carriers of rural living space, and their spatial evolution and functional transformation reflect the dynamic restructuring of human–land relationships. In karst mountainous areas, complex topography, fragmented land resources, and uneven distribution of public facilities significantly influence settlement patterns and residents’ living spaces. This study aims to quantify the relationship between settlement clustering characteristics and living-space demand and to construct a spatially explicit framework for rural settlement restructuring from a living-space perspective. Taking the Qixingguan District of Bijie City, Guizhou Province—a representative karst mountainous area in Southwest China—as a case study, we develop an integrated analytical framework encompassing spatial identification, demand measurement, and zoning optimization. Settlement clusters were identified using the Nearest Neighbor Index and Kernel Density Analysis, while accessibility to essential services—including education, healthcare, and shopping—was quantified via a Gaussian-based two-step floating catchment area method. Living-space demand was further assessed by integrating accessibility gradients with residential conditions, and restructuring types were classified based on the Living Space Index and the distance from settlements to town centers. The results indicate that (1) rural settlements in Qixingguan District exhibit significant clustering, with high-density zones concentrated around urban peripheries and along transportation corridors; (2) accessibility to living services follows a distance-decay pattern modulated by transportation networks, forming hotspots in suburban and town-center areas and cold spots in peripheral karst mountainous areas; and (3) based on the comprehensive assessment, settlements are categorized into four types—urbanizing villages, central villages, preserved villages, and relocation villages—with corresponding targeted spatial restructuring strategies proposed. This study advances the geographical understanding of rural settlement restructuring in karst mountainous areas and provides empirical evidence for optimizing human–land relationships and promoting more equitable and sustainable spatial development in mountainous regions. Full article

The carbonate massifs of the southern Italian Apennines host extensive karst aquifers, which represent the principal drinking water resources. This study focuses on the Dragone Plain polje, a vast closed karst depression located in the main recharge sector of the Terminio–Tuoro carbonate massif. The polje drains a ~55 km² endorheic catchment and may be flooded during the cold and wet season, forming a temporary lake. We employed continuous hydroclimatic time series (rainfall, groundwater level, spring discharge, and river level) together with sparse Sentinel-2 true color satellite images for the period 2020–2024 to analyze the flooding process in the polje and its hydraulic connection with the saturated zone of the karst aquifer. Results indicate that lake formation depends on the balance among soil moisture, rainfall intensity, and runoff development, which were modeled on a daily scale. Daily recharge was also estimated and compared with groundwater level time series from the deep karst aquifer. The modeling was integrated with cross-correlation analysis of the time series, providing insights into the propagation of precipitation pulses through the hydrogeological system. This case study represents an important example for understanding the relationship between karst polje hydrological functioning and climate in a Mediterranean area. Full article

In ecologically fragile karst regions, surface water leakage and spatial mismatches between supply and demand exacerbate water scarcity and ecosystem degradation. In this context, sustainable water resource allocation is of great significance for achieving the United Nations Sustainable Development Goals (SDGs). This study proposes a Dual-stage Prediction and Optimization Coupled Allocation Model (DPOCAM), which integrates an LSTM–Transformer-based intelligent water demand forecasting model with the NSGA-III multi-objective optimization algorithm. The forecasting model was trained on data from 2001 to 2020 and tested on data from 2021 to 2024, achieving a mean absolute percentage error of 2.89%. The model incorporates ecological water demand as an independent optimization objective, quantified using the Tennant method, aiming to coordinate the relationship between domestic and productive water use with aquatic ecosystem protection. Applied to Sinan County, a typical karst area in Guizhou Province, China, the model projects sectoral water demands for 2035 and conducts water resource allocation based on water network planning. Results show that under the current water network, the comprehensive water shortage rate reaches 17.7%, with ecological deficit accounting for 10.1%, posing dual threats to human water security and ecosystem integrity. Following the planned construction of a water network centered on the Huatanzi Reservoir, the overall shortage rate drops to 0.6%, and the ecological deficit declines to 4.6%, demonstrating significant improvements in both water supply reliability and ecological flow guarantee. The water network construction plays a positive role in reducing water shortage rates and enhancing ecological flow protection, providing a scientific basis and practical reference for sustainable water resource management in karst regions. Full article

Soil nutrient loss and infertility in rocky desertification areas severely constrain ecological restoration. Exploring the impacts of external field remediation technologies on soil quality in these regions may offer novel strategies for soil enhancement and ecosystem recovery. This study conducted a three-month experiment to investigate the impact of continuous electric (ET, 20 V) and magnetic (MT, 200 mT) field treatments on soil nutrients, enzyme activities, and bacterial communities in simulated moderate and severe rocky desertification soils. Results showed that although an overall declining trends in total contents of key soil nutrients (Total nitrogen, total phosphorus, and total potassium), both electric and magnetic field treatments effectively mitigated the decreases of total nitrogen and potassium content (with the exception of total phosphorus) in rocky desertification soils, while improving their available contents compared to the control (CK). Electric field application significantly reduced the pH of moderate and severe rocky desertification soils through electrolysis, shifting the soil from alkaline (pH 7.69 and 7.73, respectively) to slightly acidic (pH 6.71 and 6.37, respectively); Both electric and magnetic field treatments enhanced urease and sucrase activities in moderately and severely rocky desertified soils. Compared to the CK, the increases were 21.92%, 4.46%, 5.70%, and 66.43% in moderately rocky desertified soil, and 10.06%, 42.15%, 20.66%, and 0.93% in severely rocky desertified soil, respectively. Their effects on phosphatase and catalase activities varied with the degree of rocky desertification. However, in severely rocky desertified soil, both treatments significantly increased phosphatase and catalase activities by 19.55%, 24.63%, 61.07%, and 38.05% compared to the CK, respectively. Furthermore, both electric and magnetic treatments significantly reduced bacterial α-diversity (chao1, ACE, Shannon, Simpson, and Pielou J indices) but optimized community structure by enriching dominant phyla with specific ecological functions, such as Pseudomonadota (7.63–41.10%), Bacteroidota (13.52–69.29%), and Verrucomicrobiota (38.26–104.81%). Functional prediction revealed that the abundances of dominant pathways (such as chemoheterotrophy, aerobic chemoheterotrophy, and nitrogen fixation) was enhanced following both treatments. Mantel analysis further indicated strengthened correlations among soil nutrients, enzyme activities, and bacterial communities, particularly under magnetic field treatment. These findings demonstrate that electric and magnetic field applications effectively facilitate nutrient cycling, stimulate enzyme activities, and optimize microbial community structure, thereby improving soil ecological functions and overall quality in rocky desertification regions, highlighting their potential for ecological restoration in karst areas. Full article

Groundwater drainage-induced karst collapse is a major geohazard in coal-mining regions of central Hunan, threatening residential safety and infrastructure. This study focuses on the Tuoshan minefield in the Jinzhushan mining area by integrating multi-source field data, including surveys of 170 collapse points, long-term groundwater monitoring at six boreholes, and high-density electrical geophysics. A topographically corrected MODFLOW seepage-field model is developed and calibrated for 2014 (RMSE = 0.32 m; NSE = 0.85) and validated for 2015–2016 (RMSE = 0.41 m; NSE = 0.81). To address the large groundwater-level simulation errors commonly encountered in subtropical hilly karst mining settings, the model incorporates a topographic correction, improving simulation accuracy by 12% relative to an uncorrected model. The simulations capture rapid “steep rise–slow fall” groundwater dynamics: Heavy rainfall (>100 mm/day) raises groundwater levels by 2.8–3.1 m within 2–3 days, whereas pumping (200 m³/h) causes a 1.9–2.2 m decline within one week. A 1.2 km drawdown funnel forms and overlaps with 89% of collapse points, indicating that seepage-field evolution and groundwater-level decline control collapse clustering, with soil suffusion and soil–water–rock interaction acting as key amplifying processes. Based on Terzaghi’s effective stress principle and the Theis solution, a collapse prediction formula is derived and validated using measured events (accuracy = 87.5%), and a region-specific critical hydraulic gradient (i_n = 0.85) is determined, lower than values reported for North China. The proposed workflow provides quantitative thresholds and model-based guidance for karst collapse prevention in subtropical mining areas. Full article

Investigating the cycling characteristics of dissolved inorganic carbon (DIC) in karst groundwater within arid and semi-arid regions is crucial for understanding its role in the global carbon cycle and its contribution to atmospheric carbon sinks. This study is centered on the Liulin Spring area of North China, based on sampling data from April 2019. We employed hydrogeochemical analysis and environmental isotopic tracing methods to (1) characterize the spatial distribution of DIC along the groundwater flow path; (2) elucidate the sources of HCO₃⁻; (3) calibrate groundwater ¹⁴C ages. Results indicate that the HCO₃⁻ concentration initially increases and then decreases along the flow path, peaking in the spring discharge zone. Conversely, δ¹³C values initially decrease and then increase, reaching a minimum in the discharge zone, exhibiting a negative correlation with the HCO₃⁻ concentration. The contribution of soil/biogenic CO₂ dissolution to HCO₃⁻ ranges from 26% to 62%, with the highest values (56–62%) observed in recharge, runoff, and discharge zones and lower values (26–49%) observed in stagnant zones; this contribution generally decreases towards the western boundary. Calibrated ¹⁴C ages are significantly reduced and align better with expected groundwater dynamics. Full article

Arsenic contamination in polymetallic mining areas is closely linked to surrounding iron-rich manganese minerals. However, conclusive evidence remains limited regarding the retention and migration process of As(V) in naturally manganese-rich manganese ores (especially those with different manganese/iron mass ratios) under dynamic flow conditions. This study investigated As(V) adsorption and transport by four natural manganese minerals (FM1–FM4) through batch/column experiments, characterization, and numerical modeling. Their Mn/Fe mass ratios were 22.7 for FM1, 4.2 for FM2, 3.7 for FM3, and 16.4 for FM4. Batch experiments showed that As(V) adsorption on FM1–FM3 was better described by the Freundlich model, indicating heterogeneous adsorption behavior. Under the tested experimental conditions, the apparent Langmuir qₘ values of these minerals decreased from 0.066 to 0.015 mmol·g⁻¹ with decreasing Mn/Fe ratio. However, As(V) adsorption on FM4, which had the lowest Mn and Fe contents, followed the Langmuir model (qₘ = 0.012 mmol·g⁻¹), suggesting monolayer adsorption. Column experiments demonstrated rapid As(V) retention for all minerals. In the time domain, increasing the flow rate from 0.5 to 2.0 mL·min⁻¹ generally advanced breakthrough and shortened the desorption tail, although the breakthrough behavior expressed in pore-volume coordinates was not strictly monotonic for all minerals. The Two-Site Kinetic Attachment Model (TSKAM) successfully simulated these dynamics (R² > 0.90, RMSE < 0.05), revealing adsorption controlled by fast and slow kinetic sites, with slow-site contributions diminishing at higher flow rates. Characterization results indicated that adsorbed arsenic on FM1 remained mainly as As(V) and was immobilized primarily through surface complexation involving surface hydroxyl and Fe/Mn–O groups. XRD and SEM-EDS suggested the participation of Fe/Mn-bearing phases, while XPS on FM1 showed pronounced changes in Mn surface species during adsorption. Therefore, As(V) removal by these natural manganese minerals is a coupled physicochemical process influenced by both mineral properties, including Mn/Fe ratio, specific surface area, pore structure, pH_PZC, and Mn surface-state changes, and hydrodynamic conditions in the polymetallic mining areas. Full article

Oenanthe javanica (LY) and Oenanthe linearis (SQ), collectively known as water dropwort, are popular aquatic vegetables in China. Their blanching cultivation produces tender, etiolated tissues with reduced lignin content and improved sensory qualities. To clarify the effects of shading cultivation on lignin synthesis and accumulation in these two cultivars, this study investigated their shading responses in terms of morphological traits, physiological indices, enzyme activities, cellular structure, and lignin synthesis-related gene expression levels. The results showed significant differences between the two cultivars during the 24-day shading treatment. Compared with ‘SQ’, ‘LY’ exhibited upright growth and marked elongation of new petioles, while old petioles were significantly decreased. The entire plant turned light yellow or white, conferring commercial value typical of blanched water dropwort. During the initial 0–16 d of shading, lignin content was higher in ‘SQ’; however, by day 24, it was 92.26 mg·g⁻¹ lower in ‘SQ’ than in ‘LY’. In terms of enzyme activity, shading generally decreased the activities of PAL, CAD, and C4H, while increasing 4CL activity. Notably, shading reduced POD activity in ‘SQ’ but increased it in ‘LY’. Histological observation revealed that shading led to a gradual loosening of xylem cell arrangement in water dropwort; furthermore, the number and size of xylem cells in ‘LY’ were significantly larger than those in ‘SQ’. At the molecular level, shading significantly downregulated the expression of OlPAL, Ol4CL, OlCCR, OlCCoAOMT, and OlCAD1 in ‘SQ’, a trend that correlated with the observed decrease in lignin content and thus appears to be a primary cause of altered lignin accumulation. In ‘LY’, the expression level of OjPAL2 decreased, showing a positive correlation with both PAL enzyme activity and lignin content, suggesting it acts as a key regulator of lignin synthesis under these conditions. In conclusion, compared with ‘SQ’, ‘LY’ exhibits a higher degree of lignification but possesses stronger resistance to shading stress, making it more suitable for producing high-quality etiolated water dropwort. Full article

Owing to topographical constraints, rural domestic sewage management in karst areas faces unique challenges (scattered pollution sources, fragile hydrogeology, and inadequate infrastructure), but research on decentralized treatment technologies and their microbial mechanisms in this area remains scarce. This study aimed to evaluate the efficiency of a physicobiological process (pre-treatment + BAF) for decentralized rural sewage treatment in karst areas and clarify the relationship between microbial community composition and treatment efficiency under different scales. Annual analyses of influent/effluent pollutants and 16S rRNA gene sequencing were conducted for BAF systems of varying scales. The average removal rates of COD, TN, NH₃-N, and TP were 65.35–79.25%, 32.09–66.66%, 49.50–75.42%, and 44.92–67.69%, respectively. Treatment efficiency varied significantly with scale, being higher in larger systems (p < 0.001). All scales shared a core microbial community (dominated by Proteobacteria, Bacteroidetes, and Chlorobi), but the relative abundance of core taxa decreased with decreasing scale. Nitrification and denitrification were positively associated with NH₃-N and TN removal, respectively. Smaller treatment units were more prone to miscellaneous bacteria proliferation, potentially reducing treatment stability. This study fills the research gap of decentralized BAF application in rural karst areas and provides a scientific basis for the scale optimization of rural wastewater treatment facilities. Full article

Potentially toxic element (PTE) co-contamination in farmland severely threatens global food safety. To identify effective remediation strategies, large-scale field trials were conducted in two karst regions of Southwest China highly co-contaminated with Cd, Pb, As, Cr, and Hg. The efficacy of seven commercial soil amendments (biochar (BC), fused calcium–magnesium phosphate (FCMP), humic acid (HA), potassium humate (KH), oyster shell powder (OS), composite passivator (PA), and quicklime (QL)) on soil physicochemical properties, PTE bioavailability, maize (Zea mays L.) yield, and plant tissue distribution was systematically evaluated. The results indicated that organic amendments, specifically BC, HA, and KH, consistently outperformed inorganic treatments. These organic materials significantly decreased the diethylenetriaminepentaacetic acid (DTPA)-extractable fractions of cationic PTEs (e.g., Cd and Pb decreased by up to 39.5% under KH treatment) without inadvertently mobilizing As, unlike the alkaline inorganic amendments. This reduction in soil bioavailability closely correlated with improved plant performance, leading to maximum increases in root biomass (up to 130% with BC) and grain yield (up to 27.6% with HA). Furthermore, BC and humic substances effectively restricted PTE accumulation in grains (Cd and Pb reduced by up to 42.1%). Tissue distribution analysis revealed a consistently low root-to-stem translocation factor (TF < 0.2), indicating that roots acted as the primary sink for absorbed PTEs. This study indicates that commercial organic amendments support the use of a superior, broad-spectrum strategy for mitigating multi-PTE risks and ensuring safe agricultural utilization in severely co-contaminated areas. Full article

Agricultural land transformation significantly affects ecosystem services (ES), yet its impacts across different topographic gradients remain unclear, hindering integrated land management in karst mountainous areas. Using Puding County, Guizhou Province, as a case study, this research employed the land-use transfer matrix, the InVEST model, and Spearman correlation analysis to examine the spatiotemporal patterns and relationships between agricultural land transformation and ES from 2004 to 2024. The findings indicate: (1) Agricultural land transformation shows distinct topographic differentiation: non-agricultural conversion and agricultural intensification dominate low-topographic positions; ecological land use conversion and agricultural intensification coexist in mid-topographic positions; and ecological land use conversion prevails in high-topographic positions. (2) ES vary consistently along topographic gradients: soil retention and carbon storage increase with elevation, food supply concentrates in low topographic positions, and water yield changes are most pronounced at low topographic positions. (3) Topography regulates the ecological effects of transformation pathways: ecological land use conversion enhances regulating services in high-topographic positions, while farmland abandonment increases erosion risk; composite transformation promotes a dynamic balance between services in mid-topographic positions; and agricultural intensification improves food supply but intensifies water competition in low-topographic positions, whereas non-agricultural conversion degrades multiple ecosystem services. This study provides a scientific basis for zoned land management and sustainable development in karst mountainous areas. Full article

In karst mountainous areas where high-dimensional features coexist with extremely limited sample sizes, accurate landslide susceptibility mapping remains challenging. To address this issue, we propose an ensemble framework termed the Triple-Source Probabilistic Fusion Bidirectional Long Short-Term Memory network (TSPF-BiLSTM). The approach was tested in Sangzhi County, Hunan Province, by integrating three base learners—Random Forest (RF), LightGBM, and AdaBoost. Their raw outputs were first calibrated using five-fold Platt scaling to generate posterior probabilities on a unified scale. A bidirectional LSTM was then employed to perform deep nonlinear fusion of these cross-model probability features. Using a total of 618 landslide and 618 non-landslide samples (split into training and testing sets), the TSPF-BiLSTM model achieved a mean AUC of 0.9525 (±0.0115) under ten-fold cross-validation, outperforming not only the individual base learners but also standalone deep learning models (CNN and Transformer). The frequency ratio in the very high susceptibility zone reached 3.97, significantly exceeding all benchmark models and confirming its superior capability in high-risk area identification. Multi-model importance analysis identified NDVI, elevation, and annual rainfall as the dominant regional landslide predisposing factors. Within the specific ranges of NDVI 0–0.686, elevation 155–462 m, and annual rainfall 1273.6–1301 mm, landslide frequency ratios consistently exceeded 1.96. The proposed framework, with its probability-level fusion and embedded regularization mechanisms, effectively mitigated overfitting despite the small sample size, providing a robust technical solution for geological hazard risk identification and prevention in the data-scarce karst terrain of the Wuling Mountains. Full article

The Turpan–Hami Basin, a critical energy hub in northwestern China, is plagued by frequent ground collapses induced by extensive mining over karst geology, threatening ecology and safety. Current hazard assessment methods, mainly single linear or traditional machine learning models, fail to capture the complex nonlinear interactions inherent to this coupled geo-mining environment. This study addresses this gap by establishing a multi-dimensional “Geology-Mining-Hydrology-Environment” index system comprising 14 critical factors—including lithology, goaf distribution, mining intensity, and their interaction terms. A coupled gradient boosting decision tree and logistic regression (GBDT-LR) model, optimized for the multi-factor coupling characteristics of ground collapse in arid mining basins, was applied for the hazard assessment. The results reveal a distinct spatial pattern of “core agglomeration with multi-level gradient differentiation.” Extremely high-hazard areas, covering 9.21% of the area, are concentrated in the core mining areas northwest of Turpan and southwest of Hami, while high-hazard areas (4.63%) form surrounding belts. The GBDT-LR model (AUC = 0.871) demonstrated significantly superior performance over a single logistic regression model (AUC = 0.813), proving its enhanced capability to identify high-hazard areas by modeling complex factor interactions. This work provides an essential scientific foundation for implementing zonal hazard management and prioritizing disaster prevention projects in key areas of the basin. Full article

Karst water systems are highly vulnerable to land use pressures, requiring integrated assessments to support conservation and management. This study evaluated the physicochemical, microbiological, and pesticide-related water quality in the Environmental Protection Area Nascentes do Rio Vermelho (APANRV), a karst conservation unit in the Brazilian Cerrado. Sixteen sampling sites (rivers, springs, and cave waters) were monitored during the dry (May 2024) and rainy (October 2024) seasons. Analyses included nutrients, major ions, Escherichia coli, and a broad spectrum of pesticides. The results showed marked spatial and seasonal variability, with elevated hardness and conductivity in karst areas due to carbonate dissolution. Nitrate and total phosphorus reached peak values of 13.59 and 0.132 mg L⁻¹, respectively, indicating localized nutrient enrichment. E. coli concentrations reached ≥2419.6 MPN 100 mL⁻¹, exceeding regulatory limits, particularly during the rainy season at recreational cave sites. Pesticides were detected in both seasons, with 11 compounds in the dry season and 8 in the rainy season, including atrazine degradation products, and maximum quantified concentrations up to 1.8 µg L⁻¹ (acephate). These findings highlight the combined influence of geology, seasonality, and land use on karst water quality and reinforce the need for continuous monitoring and targeted management strategies. Full article

This article presents the results of hydrological research on the Ruda River, which is the largest tributary of the Cetina River, located in the Dinaric karst of Croatia. The hydrology of this river has been altered after the construction of the Orlovac Hydropower Plant (HP) and the Buško Blato reservoir in 1973. The main aim of this study was to generate new knowledge about the hydrological functioning of the river, with a focus on the discharge and water temperature regimes that experienced the most severe alterations. The methodology is based on classical hydrological, statistical, and time-series analysis methods, adapted to the particularities of the study area and available data. Daily and hourly time series of air temperature, precipitation, water temperature, and discharge are analyzed to find trends, change points, inter-annual, seasonal, and sub-daily variations, durations, time shifts, and linear dependencies. The results obtained provide information on the effects of climate change, the duration of diffuse, conduit, and mixed flow, the importance of groundwater exchange, retention times, heat transfer times, and reference water temperatures. It determined the role of the operational mode of the Orlovac HP in discharge from the spring, in inter-annual and sub-annual water redistribution, and in hydropeaking and thermopeaking. The obtained information defines the present state of the Ruda River hydrology and illustrates alterations. Full article