Search Results (1,314)

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

The natural regeneration of planted forests in karst landscapes is severely constrained by extreme substrate heterogeneity and fragile edaphic conditions. However, the relative importance and interaction pathways of environmental versus stand structural drivers remain poorly quantified. In this study, 54 plots (10 m × 10 m) were surveyed across Cupressus funebris plantations in the karst landscape of the Lijiang River Basin, southern China. To identify the key factors and causal pathways governing regeneration, redundancy analysis (RDA), variation partitioning, partial least squares structural equation modeling (PLS-SEM), and threshold analyses were applied. Regeneration exhibited pronounced spatial heterogeneity, with 42.6% of plots showing complete recruitment failure and a characteristic inverted J-shaped size class distribution. The analysis identified soil rock fragment content (as a negative constraint) and canopy gap area (as a positive driver) as the two dominant predictors. PLS-SEM revealed that environmental factors influence regeneration primarily through an indirect pathway mediated by stand structure ($R^2=0.683$) rather than through direct effects. Threshold analyses identified quantitative benchmarks for key drivers, including a gap area breakpoint of approximately 10 ${\mathrm{m}}^2$ and a presence–absence effect of soil rock fragments. These findings contribute to a more sophisticated mechanistic understanding of forest regeneration in karst ecosystems and provide an empirical foundation for silvicultural management that aims to encourage natural regeneration and ecological restoration of degraded karst plantations. Full article

Background: The adaptability of leguminous plant–rhizobia symbionts enables enhanced plant stress tolerance in environmentally stressed areas. However, how rock desertification (RD) severity affects the endophytic and nitrogen-fixing bacterial communities in Pisum sativum root nodules remains unclear. Methods: We systematically surveyed the microbial communities of P. sativum nodules across a gradient of four RD areas. We sequenced 16S rRNA and nifH amplicons, determined soil physicochemical properties, and performed bioinformatic analyses to relate nodule microbiome diversity to soil variables. Results: The dominant endophytic genera across all sites were Allorhizobium–Neorhizobium–Pararhizobium–Rhizobium and Pseudomonas, with Rhizobium identified as the primary nitrogen-fixing taxon. Soil pH and total phosphorus (TP) showed significant correlations with the overall endophytic bacterial community, whereas total nitrogen (TN), TP, and soil water content (SWC) were associated with nitrogen-fixing taxa. Notably, P. sativum nodules from areas of slight rocky desertification (SRD) harbored higher endophytic bacterial diversity and enhanced carbohydrate metabolism compared to those from moderately rocky desertified (MRD) sites. Conclusions: This study sheds light on how bacterial communities within legume root nodules respond to RD stress, deepening our understanding of plant–microbe co-adaptation and informing microbial-assisted restoration strategies in karst desertification areas. Full article

Fly ash (FA) captures most mercury (Hg) in the waste stream during municipal solid waste incineration (MSWI), and the content and speciation of Hg in MSWI fly ash (MSWI-FA) have a significant impact on the ecological environment. In this study, 245 fly ash samples were collected from 18 MSWI facilities in Guizhou Province, a fragile karst area with a high Hg background in Southwest China. The results indicate that total Hg ranged from 0.52 to 444 mg/kg among samples, while the geometric means varied from 0.85 to 223.33 mg/kg for different incinerators, with a weighted geometric mean of 22.14 mg/kg, more than double the national average. Substantial temporal variability in Hg content suggested intermittent inputs of Hg-rich waste into the MSW stream. While positive correlations (p < 0.05) were observed between Hg and chlorine, potassium, and cadmium, the moderate to low R² values indicate that Hg enrichment is a complex multi-factor system influenced by heterogeneous waste compositions and transient thermochemical conditions. Speciation analysis revealed that most of the Hg exists in its elemental form (F4), constituting over 80% of the total Hg. However, the water-soluble fraction (F1) and the ion-exchangeable fraction (F2) each reached up to 26–29% in some samples, indicating substantial environmental mobility. These findings demonstrate that MSWI-FA in Guizhou contains elevated Hg levels, posing considerable ecological and environmental risks. Enhancing the classification and management of Hg-containing waste in MSW is critical to mitigating the environmental risks of fly ash, particularly in karst ecological areas. Full article

Plant invasions severely threaten the stability and biodiversity of fragile ecosystems in karst areas. Elucidating the microbial mechanisms underlying the interactions between invasive plants and native plants in rhizosphere soil is crucial for preventing plant invasions. In this study, high-throughput sequencing was used to compare the differences in rhizosphere fungi between two invasive and native plants in the Guizhou karst region. These findings provide theoretical support for understanding the ecological impact of invasive plants and for developing ecological management strategies based on soil microorganisms. The results revealed the following: (1) A total of 16 soil samples were included in the study, which comprised 1 phylum, 50 classes, 112 orders, 245 families, 463 genera and 629 species. (2) No significant differences were observed in the Ace, Chao, Shannon, Simpson and Sobs indices of the rhizosphere fungal communities between invasive plants and native plants (p > 0.05). (3) At the phylum level, no significant difference was observed in the community compositions of invasive and native plants; the dominant phyla were Ascomycota, Mortierellomycota and Basidiomycota; at the genus level, there were significant differences in the community composition of invasive and native plants, and the relative abundances of Minimedusa, Monocillium and Gymnopus in the rhizosphere soil of invasive plants were significantly higher (p < 0.05). (4) Functional predictions based on FUNGuild indicated a higher relative abundance of saprotrophic fungi associated with invasive plants. Community assembly processes for both invasive and native plants were primarily governed by stochastic ecological processes (e.g., drift). These findings suggest that plant invasion is associated with shifts in the composition and potential ecological functions of rhizosphere fungal communities in the karst area. Full article

Regional curtain grouting for water interception serves as a critical technique for achieving safe and efficient mining under complex hydrogeological conditions in deep mine deposits. This study focuses on the Cuihongshan Iron-Polymetallic Mine, where repeated incidents of water inrush and sand outbursts have occurred due to complex hydrogeological conditions. By identifying the water-conducting pathways and characterizing the spatial distribution of relative aquitards within the mining area, a precise hydrogeological model was established. On this basis, the engineering application and performance evaluation of horizontal curtain grouting were systematically investigated. Through field monitoring and multi-method joint analysis, the water-blocking effectiveness of the grouting technique was comprehensively assessed. The results demonstrate a significant sequential reduction in grout take per meter for primary, secondary, and tertiary grouting holes, indicating a clear cumulative grouting effect. The grout effectively filled karst fractures, forming a continuous and stable water-resisting curtain. The project successfully severed the hydraulic connection between the highly water-rich Quaternary aquifer and the mine workings, substantially reducing mine water inflow. This study provides important theoretical support and practical reference for water hazard control in similar deep metal mines. Full article

Climate change is increasing forest vulnerability, and extreme disturbances such as windstorms can cause major economic and social losses. Forest recovery after such events often relies on salvage logging and extensive planting of seedlings produced in nurseries to rapidly restore forest cover. While effective, these interventions, particularly when applied over large areas, may also produce environmental impacts that are largely absent under spontaneous regeneration. Following the Vaia windstorm in northern Italy in 2018, several reforestation interventions were implemented to restore forest cover. We focused on one intervention and conducted a life cycle assessment to quantify its environmental impacts, using the planting of 800 four-year-old Norway spruce (Picea abies (L.) H. Karst) seedlings as the functional unit, combined with chipping on the site of forest biomass residues. The largest contributions were to global warming potential (443.91 kg CO₂ eq), human toxicity (167.72 kg 1,4-DCB eq), and freshwater ecotoxicity (142.43 kg 1,4-DCB eq). Seedling production and field establishment dominated these impact categories. Among field operations, manufacturing and transporting plastic shelters for seedling protection accounted for the highest share of global warming potential. Full article