The compliant discharge of landfill leachate constitutes a pivotal factor for the effective implementation of integrated water resource management. Aged landfill leachate exhibits complex composition and an imbalanced carbon-to-nitrogen ratio. Electrocatalytic oxidation technology, as an efficient advanced oxidation process, demonstrates promising application potential. This study employed Ti/RuO2–IrO2 Anodes for the electrocatalytic oxidation treatment of aged landfill leachate. The removal efficiencies and variation patterns of chemical oxygen demand (COD), ammonia nitrogen, and total nitrogen at different current densities and reaction times were systematically investigated, along with an analysis of energy consumption and current efficiency. The degradation and transformation processes of organic matter were elucidated using Three-dimensional Excitation–Emission Matrix (EEM) Spectra. Fresh anodes and those used for 1000 h were characterized by scanning electron microscopy (SEM) and energy-dispersive spectroscopy (EDS) to elucidate their failure mechanisms. The results demonstrate that electrocatalytic oxidation achieves efficient pollutant removal. At a current density of 1000 A/m2 and a reaction time of 30 min, the effluent concentrations of ammonia nitrogen and total nitrogen satisfied the discharge standards, while COD complied with emission requirements after 60 min. The pollutant removal efficiencies were positively correlated with current density and reaction time. EEM analysis revealed that the electrocatalytic process effectively disrupts the structure of macromolecular organic matter, degrading it into smaller molecules and eventually achieving complete mineralization. Electrode characterization identified titanium substrate corrosion due to coating cracks and coating detachment as the primary causes of electrode failure. This study confirms the effectiveness of electrocatalytic oxidation technology for treating aged landfill leachate, and provides a theoretical foundation and technical support for its practical engineering application. The technology exhibits considerable theoretical significance and promising application potential in the treatment of landfill leachate.

Fungicide contamination is an increasing global environmental concern, due to the harm they may pose to non-target organisms, their contribution to antimicrobial resistance, and the potential risks to human health when drinking water (DW) sources are impacted. Many fungicides used in agriculture are chiral and may exist as racemates, or a combination of diastereoisomers and/or enantiomers. Since enantiomers can differ in environmental fate, distribution, and toxicity, enantioselective analysis of chiral fungicides is crucial. The aim of this study was to develop and validate an analytical method for the determination of azole chiral and achiral fungicides in DW using solid-phase extraction followed by liquid chromatography-tandem mass spectrometry (SPE-LC-MS/MS). Chromatographic separation of one achiral fungicide and five chiral fungicides was achieved using a polysaccharide chromatographic column under reverse elution mode. The validated method demonstrated high sensitivity with method detection limits (MDL) below 0.86 ng L−1 and was successfully applied to 13 DW samples collected from various supply networks across Portugal. Seven out of the 15 targeted analytes were found at trace concentrations (>MDL). Fluconazole was the most frequently detected (~87% of the samples). The hazard quotients (HQs) for individual compounds for each individual fungicide (sum of the enantiomers for those chiral) and the hazard index (HI, sum of the individual HQ values) were calculated in each DW sample, indicating no significant health risks to consumers, since it is well below 0.1 for all compounds.

One of the most serious problems Yemen is facing is water scarcity, driven by low rainfall, high agricultural water consumption, and limited reuse of treated wastewater in irrigation, resulting in a sharp decline in groundwater, the country’s primary water source. The main objective of this study is to investigate the water governance and policy gaps in Yemen using indicators derived from previous field studies that assessed the quality of treated wastewater for irrigation reuse and calculated water requirements of banana crop. This analysis, conducted using the BROOK90 hydrological model and CROPWAT software, provides observational evidence for identifying key indicators and strategies to reduce pressure on scarce water resources and mitigate groundwater depletion. The findings were subsequently compared with the water governance practices in China and Singapore, focusing on governance frameworks, institutional arrangements, environmental and social impact dimensions, and policy integration rather than direct technological replication, acknowledging the substantial economic differences between the countries. The findings show that reusing wastewater, together with supplying crops with the optimal amount of irrigation, can significantly mitigate groundwater depletion and preserve limited water supplies. However, to achieve these outcomes, the suggested policies and programs must be effectively implemented, monitoring must be reinforced, and the local communities must actively participate in decision-making and planning processes.

Gravitational fingering often occurs for water flow in the vadose zone and accurate modeling of this important flow process remains a significant scientific challenge. This paper presents the latest theoretical developments of the optimality-based active region model (ARM), a macroscopic framework developed for describing gravitational fingering flow in the vadose zone. ARM divides the soil into active (fingering) and inactive regions, introducing a relationship between water flux and hydraulic gradient derived from the principle of optimality that the system self-organizes to maximize water flow conductivity. Unlike traditional models, ARM’s hydraulic conductivity depends on both capillary pressure or water saturation and water flux, reflecting the unstable nature of fingering flow. The paper provides an updated mathematical derivation of ARM relationships using calculus of variations and extends ARM to account for small water flux in the non-fingering zone, resulting in a dual-flow field model. These new developments should make ARM more rigorous and realistic for field-scale applications.

Analysis of the likelihood of structural or hydraulic failures of levees is a crucial part of flood risk assessment and is affected by many uncertainties. This paper evaluates a critical area along the Danube River in the Szigetköz floodplain, where hydraulic risk has been increasing due to rising flood levels. Blanket theory approaches demonstrated the probability of failure relative to erosional failure, and Monte Carlo simulations generated fragility curves. The results of the case study show that the thickness of the aquifer layer has a slight effect if it is deeper than 30 m. The research also reveals that the probability of failure is highly affected by the distance from the river to the riverside levee toe; the shorter this distance, the higher the hydraulic risk. Sensitivity analyses emphasize the effect of variable inhomogeneity; as the leakage factor increases, the probability of failure due to underseepage increases. Comparing coefficients of variation across different floodwater levels showed that at low floodwater levels, a lower coefficient of variation corresponds to a lower probability of failure. In contrast, at higher floodwater levels, the same coefficient produced a higher probability of failure.

Compost-derived humic acids (HAs) and fulvic acids (FAs) play an essential role in enhancing soil microbial diversity and activity by facilitating metabolic processes through electron transfer. Herein, the effect of bioleaching dewatered sludge (BDS) in comparison with filter press dewatered sludge (FDS) on the electron transfer capacity (ETC) of humic substances during composting was investigated as a novel attempt. A variety of characterization methods including UV-Vis, FTIR, 3D-EEM, and electrochemical measurements, were used to explore the change in humic substances during composting. The results indicated that bioleaching treatment significantly influenced the organic matter composition and hindered the accumulation of redox-active functional groups during composting. Notably, the ETC of HA increased by 24.07% in the FDS group but declined by 40.62% in the BDS group. This divergence stemmed from the organic matter loss during bioleaching, leading to reduced quinone-like and tryptophan-like substances associated with electron transfer in HA during composting. Furthermore, BDS showed lower pH, water content, and organic matter, but higher concentrations of ammonium nitrogen (NH4+-N) and ammonia nitrogen NH3−-N, all of which potentially influenced humification efficiency. These findings not only clarify the electron-transfer dynamics of humic fractions but also highlight the importance of optimizing sludge pretreatment for improved composting performance and resource recovery.

Tropical estuarine hydrodynamic processes are governed by complex interactions between tides, monsoons, and fluvial runoff. To obtain long-term (≥30 years) hydrodynamic conditions of the Mekong River Estuary, this study established a Finite Volume Coastal Ocean Model (FVCOM) coupled with validated Weather Research and Forecast (WRF) wind forcing for a 32-year (1988–2019) high-resolution simulation. Validation against in situ observations confirms the model’s robustness. Temporal–spatial patterns of water level and current were analyzed, and extreme parameters for 1–100 year return periods were derived via the Pearson-III probability distribution. Results indicate the study area is a mesotidal environment (tidal range = 3.58 m) dominated by SSE-NNW reciprocating tidal currents. Relative to Vietnam’s national elevation datum, 100-year return period extreme high/low water levels are 2.15 m and −2.03 m, with a maximum storm surge setup of 2.09 m. The 100-year return period maximum current velocity reaches 4.58 m/s (A21 station), and Mekong River runoff exerts a negligible influence (<5% velocity change). This study provides high-precision baseline data for offshore wind farm engineering and disaster risk assessment, offering a methodological reference for tropical estuarine hydrodynamic simulations.

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.

Brines in playas and salt lakes provide crucial raw materials for potassium and lithium products in fertilizers and the energy sector. In this contribution, elemental and multiple H, O, Sr, B, and Li isotopic constraints were employed to determine the sources and origin of brines in the Bieletan Section (BLT) of Qarhan Salt Lake, northwestern China. The δD-δ18O results demonstrate that the brines of BLT mainly originated from river waters. The correlations of [Li] vs. [B], δ7Li vs. [Li] and δ11B vs. [B]/[Cl] suggest that the original provenance and silicate weathering played important roles in the elemental and isotopic signatures of B and Li in these river waters, which had been obscured by evaporation and concentration of brines and the related precipitation and redissolution of salt minerals during the evolution of brines in the salt lake. Strontium isotopes rule out the recharge of CaCl2 fluids from the northern fault zones for brines in BLT. Finally, the combination of elemental composition and Li, Sr, and B isotopes suggests that the current brine in BLT is mainly sourced from the Wutumeiren River and has experienced constant and intense evaporation to form the highly concentrated brine. By contrast, the contribution of the Golmud River/Tuolahai River and the CaCl2 spring water from the north fault zone to the brines in BLT is negligible. Our results highlight that integrated elemental and multiple isotope analyses are more effective for achieving a precise and comprehensive understanding of the source-to-sink process in the river–salt lake system.

Soil moisture and saturation are crucial hydrological variables for understanding the soil’s condition and modeling improvement. The National Water Model (NWM), a large-scale model, simulates the hydrologic cycle across the Contiguous United States, Hawaii, and Puerto Rico. The study’s objective was to evaluate the NWM’s performance in estimating and forecasting soil moisture in Puerto Rico from the year 2021 to 2023. The datasets used included in situ stations, model outputs, and remotely sensed data from the Soil Moisture Active Passive (SMAP) mission. Then, we used Volumetric bias (Vbias), Mean Absolute Error (MAE), and Kling–Gupta Efficiency (KGE) to measure performance. The analysis assimilation results showed that three stations in each dataset had an inversely predominant error equal to 25% or less. This low error was reflected in the obtained Vbias and MAE results. Meanwhile, the KGE analysis indicated that the NWM achieves low to moderate soil moisture performance, with better agreement against SMAP than in situ observations. However, the forecasted datasets did not produce satisfactory results. Short-range forecasts exhibited negative KGE values, highlighting the importance of data assimilation, the persistent influence of bias, and scale mismatch. Although the NWM’s primary focus is streamflow forecast, these findings highlight the potential application of the model beyond its primary focus.