Search Results (231)

River-connected lakes are characterized by complex hydrological regimes, where hydrodynamic conditions serve as key physical drivers of aquatic ecosystem evolution and eutrophication. However, traditional water-balance methods struggle to accurately quantify water exchange under strong seasonal water-level fluctuations and the backwater effect of the Yangtze River, resulting in significant gaps in understanding lake hydrodynamic features and their seasonal eutrophication response patterns. Taking Dongting Lake as an example, this study employed a two-dimensional hydrodynamic model coupled with the advection–dispersion equation of a conservative tracer to simulate the spatiotemporal patterns of flow velocity and water turnover time during the dry season, rising-water season, wet season, and receding-water season using observed hydrological data from 2017 to 2025. Field sampling data and structural equation modeling were further used to identify the pathways through which hydrodynamic conditions affect lake trophic status. Flow velocity and water turnover time exhibited significant spatiotemporal heterogeneity: water turnover time was generally within 10 d in main flood channels but exceeded 60 d in stagnant floodplain areas and local topographic depressions. Seasonally, it was shortest in the wet season due to enhanced hydrological connectivity, yet longest in the dry season because of weakened hydraulic connection. The effects of hydrodynamics on trophic status were strongly season-dependent: during the rising-water season, hydrodynamics inhibited nutrient accumulation through dilution and flushing; during the wet season, strong runoff promoted external nutrient input; and during the dry season, hydrodynamics mainly affected trophic status by modifying physical habitat conditions for algal growth. These findings reveal the hydrological and hydrodynamic mechanisms regulating eutrophication in typical river-connected lakes, providing direct scientific support for hydrological regulation optimization, zonal eutrophication prevention and control, and water environmental carrying capacity assessment in Dongting Lake and similar systems, enabling lake managers to formulate differentiated pollution control strategies based on the hydrodynamic–trophic status response relationships across different hydrological seasons. Full article

History matching traditionally assumes a spatially uniform clay adsorption coefficient Kd, overlooking the fractal heterogeneity of clay mineral distributions in real reservoirs. This study generalizes the classical advection–dispersion framework by treating Kd as a non-uniform field whose logarithmic fluctuations follow fractional Brownian motion (fBm) statistics with Hurst exponent H, and by coupling the resulting heterogeneous retardation to a fractional advection–dispersion equation through the continuous-time random walk bridge β = 2/(2H + 1). A Karhunen–Loève (K-L) expansion compresses the field into a small set of spectral modes, and an adjoint-gradient inversion recovers the clay field from tracer data. The main operational limitation of the K-L approach is that sub-grid variability below the retained spectral cutoff is smoothed; within this boundary the inversion is efficient and numerically stable. Two independent validation paths are pursued. First, a cross-fitting experiment shows that when the true physics is sub-diffusive (β = 0.85), the classical advection–dispersion equation yields a negative coefficient of determination (R2 = −0.927), whereas the correctly specified fractional model fits the data, establishing fractional derivatives as physically necessary rather than mathematically optional. Second, the publicly available EGS Collab DNA-tracer dataset independently confirms statistically significant clay adsorption (retardation R = 1.250 ± 0.009, p < 0.0001). The recovered clay field attains pixel-scale accuracy R2η = 0.844 (Spearman ρ = 0.923) and R2 > 0.94 at reservoir-relevant scales of five cells or coarser. These results indicate that fractal-aware clay-field inversion provides a physically verifiable, rather than purely empirical, pathway for history matching, with direct implications for field-scale contaminant transport prediction and environmental subsurface management, and the evaluation of flue gas enhanced thermal recovery in thin-layer heavy oil reservoirs. Full article

Airborne microplastics (AMPs) are increasingly recognized as an emerging air pollutant. However, observational data remain scarce in Southeast Asia. This study provides the first observations of AMPs in Phnom Penh, Cambodia, using µFTIR-ATR imaging. Number concentration, morphology, polymer composition, aerodynamic size distribution, Feret diameter, and surface aging characteristics were investigated together with meteorological parameters, gaseous pollutants, water-soluble ionic tracers, and HYSPLIT backward trajectories to examine possible source attribution. AMPs were dominated by polyethylene (PE), polypropylene (PP), and polyethylene terephthalate (PET), with 52% classified as fragments and 82% having Feret diameter smaller than 30 µm. Across four independent 72-h sampling periods (n = 4), AMP concentrations ranged from 0.55 to 1.27 MP m⁻³ in TSP, with a mean ± standard deviation of 0.97 ± 0.30 MP m⁻³, and from 0.23 to 0.49 MP m⁻³ in the PM_2.5 fraction, with a mean ± standard deviation of 0.33 ± 0.10 MP m⁻³. In total, 134 particles were identified in TSP, of which 46 were detected in the PM_2.5 fraction. Carbonyl and hydroxyl indices indicated that PE and PP were relatively fresh and in low-to-moderate surface aging states. Pearson correlations suggested that the abundances of individual polymers were varied differently in relation to local environmental and precipitation-related variables; however, the limited number of sampling periods precludes source or process attribution. In addition, HYSPLIT backward trajectories showed that some air masses arriving in Phnom Penh had passed over marine regions under southwest monsoon flow. These findings provide the first baseline dataset for AMP pollution in Phnom Penh, Cambodia, and highlight the combined importance of local emissions and regional atmospheric transport in Southeast Asia. Full article

Nitrous oxide (N₂O) is a potent greenhouse gas and a major ozone-depleting substance of the nitrogen cycle. While global N₂O budgets focus on microbial soil sources, evidence suggests that living plants can also contribute to N₂O emissions. However, the origin of plant-associated N₂O fluxes is contested: measured emissions may arise from endogenous plant metabolism or merely from transport of soil-derived N₂O. In this review, we clarify these pathways and synthesize current findings from laboratory and field studies. Experimental evidence from ¹⁵N-tracer and axenic-culture studies supports N₂O formation linked to nitrate (NO₃⁻) and nitrite (NO₂⁻) in photosynthetic organisms, although mechanistic resolution varies among taxa. In angiosperms, proposed plastid/chloroplast and hypoxia-associated mitochondrial routes are linked to NO₃⁻/NO₂⁻ metabolism and NO formation, but the terminal NO-to-N₂O step remains unresolved and differs from the flavodiiron-dependent mechanism demonstrated in algae. We discuss key environmental and physiological controls (substrate availability, light, O₂ status, reductant supply) on these processes and highlight methodological challenges in source attribution (chamber artefacts, destructive sampling, isotope analysis). Our analysis suggests that plant-associated N₂O fluxes are real, but highly variable and context-dependent. Rather than assuming generic “plant emission factors”, we emphasize source-specific approaches that distinguish endogenous formation from soil-derived transport and microbial production. This framework can improve N₂O budgets and guide mitigation by indicating whether management should target soil N availability and microbial processes or physiological conditions favouring plant-associated N₂O formation. Full article

Hospital wastewater has begun to act as an important source of emerging contaminants, including rare earth elements (REEs), mostly lanthanides, and radiopharmaceutical residues originating from diagnostic and therapeutic nuclear medicine procedures. The increasing use of gadolinium-based contrast agents, lutetium-containing therapeutics, technetium-99m tracers, iodine-131, yttrium-90, and gallium-68 radiopharmaceuticals has raised growing concerns regarding the release of radioactive and metal-containing compounds into aquatic environments. Conventional wastewater treatment plants are often inefficient in removing these contaminants because of their high chemical stability, low environmental concentrations, and complex aqueous speciation. In this context, hybrid nanomaterials containing silver nanoparticles (AgNPs) have attracted increasing interest for both monitoring and remediation applications. AgNP-based systems exhibit unique plasmonic, catalytic, antimicrobial, and sensing properties that can be exploited in adsorption, photocatalysis, membrane filtration, electrochemical detection, and surface-enhanced Raman spectroscopy (SERS). This review critically analyzes recent advances in hospital wastewater treatment and how hybrid nanomaterials containing silver nanoparticles (AgNPs) are emerging. The review places a particular focus on contamination by REEs and radiopharmaceuticals residues, which to date, as far as we know, remains a challenging and understudied aspect, as reflected by limited publications. Full article

Soils developing in ultramafic (serpentinite) provinces are naturally enriched in Mg, Ni and Cr, which makes it difficult to separate the natural geochemical background from technogenic contamination near chrysotile asbestos mining operations. This problem is examined for the agricultural soils in the impact zone of the Zhitikara chrysotile asbestos quarry (Kostanay Region, Kazakhstan), one of the largest such operations in the world. The elemental composition of the soils was characterised by portable X-ray fluorescence, verified against ICP-OES, and complemented by X-ray diffraction. When contamination was assessed against the global crustal background (upper continental crust), nickel and chromium appeared enriched; however, relative to the local geochemical background, these elements fall within the natural lithogenic range, showing that global crustal values generate false-positive contamination signals in ultramafic terrains. Magnesium was the only element enriched above the local background and the only one that decreased systematically with distance from the quarry, identifying it as the most sensitive tracer of aerogenic serpentinite dust among the elements measured. The discordance between total and acid-soluble chromium is consistent with chromium being hosted mainly in a refractory chromite phase, so that total chromium contents overestimate the environmentally relevant fraction. The study demonstrates the pitfall of applying global crustal backgrounds in ultramafic provinces and supports a locally referenced, differentiated approach to soil-contamination assessment in such settings. Full article

This study presents the development and application of a continuous monitoring system to operate in hybrid mode for the atmospheric and oceanic environments. The developed system integrates a smart version of the underwater in situ sensor named KATERINA to a stationary platform in order to operate as a real-time communication tool. The data are transferred using a mobile telephony network and the power is generated for all modules by a solar panel. The system is applied for a period of around six months in different seasons to detect and identify gradients of environmental radioactivity in the atmosphere. The system observed gamma-ray emitters during dry and wet periods, exhibiting enhanced radon progenies during wet periods as identified in the acquired spectra. Moreover, the gross gamma-ray intensity depends on the radon progenies and is used as a tracer to interpret rainfall events in a qualitative manner. The background gamma-ray spectra during dry periods for different seasons are also discussed in terms of seasonality. The correlation of gamma-ray intensity rate with the rainfall rate is also studied for the wet periods, providing a R² value of around 75%. Full article

The growing urbanisation of India is a major contributor to the production of 72,368 million litres of wastewater daily. Unfortunately, not even 28 to 31% of the generated wastewater receives proper treatment before disposal, putting public health, water quality, and ecological conditions at risk. Traditional wastewater treatment technologies have been proven effective, but they cannot be applied in decentralised settings due to excessive initial investment costs, continuous power needs, and the need for expert supervision. Constructed wetlands (CWs) provide an efficient and environmentally friendly option for decentralised treatment, but these systems suffer from a gradual loss of effectiveness associated with the problem of media-clogging in traditional setups. This research investigates the functioning and efficiency of the Modified Towery Bio-rack Constructed Wetland (MTBRCW) technology designed specifically to mitigate media-clogging issues. The MTBRCW is tested on the basis of its performance under continuous operating conditions for thirteen months (January 2025 to January 2026), as well as on the effectiveness of the treatment at eight different hydraulic retention times (days 1 to 8). A pilot-scale MTBRCW system was monitored through two periodic sampling events (S1 and S2) conducted during each month of operation. The pilot-scale MTBRCW unit is made up of an inlet storage tank (volume 0.099 m³) followed by two wetland containers (volume 0.034 m³ each) planted with Typha angustifolia and Chrysopogon zizanioides (vetiver grass). In continuous testing mode, influent–effluent paired samples are collected for eight days at each HRT (totalling eighty samples), and samples are analysed according to APHA Standard Methods for pH, BOD, COD, TN, and TP. In continuous testing mode, the MTBRCW exhibits high removal efficiencies at the levels of 89.8% for BOD, 87.5% for COD, 78.2% for TN, and 74.4% for TP. The BOD/COD of the effluent was within the prescribed CPCB discharge limits for all thirteen months of the study, and the TN levels were adhered to in 12 out of 13 months, with one non-compliance event recorded only in July 2025 (effluent TN = 10.8 mg/L), coinciding with the peak monsoon hydraulic loading rate of 0.28 m³/m²·d. TP remained within CPCB limits in all thirteen months. In batch testing mode, removal efficiencies are 94.9% for BOD and 89.9% for COD by day 8. In addition, there were no indications of clogging or any reduction in hydraulic performance during the entire period of the tests through the use of visual inspections and measurement of the outlet flows, but this can only be seen as an observation in a field operation, and not as proof of the hydraulic performance of the system, since no tracer test or measurement of hydraulic conductivity was conducted. Full article

Identifying sediment sources in mining-impacted watersheds is essential for understanding sediment dynamics and supporting environmental management. This study applies a geoenvironmental modeling approach based on geochemical sediment fingerprinting to quantify the relative contribution of three sediment sources in the Colca River micro-watershed (southern Peru): agricultural areas (ZAGR), non-mining areas (QSAM), and mining-influenced zones (ZAM). Water and sediment samples were collected during dry and wet seasons, and 31 elements were analyzed using inductively coupled plasma mass spectrometry (ICP-MS), supported by complementary analytical techniques. Source apportionment was performed using the FingerPro model in R 4.5.0, applying Conservation Index (CI), Consensus Ranking (CR), and Consistent Tracer Selection (CTS) methods. Results indicate that non-mining zones dominate sediment sources, contributing approximately 58–60%, while mining-influenced zones contribute up to 31.5% in downstream areas. Although ZAM represents a lower contribution, it is associated with elevated concentrations of Zn, Pb, Cd, and As. The selected tracers (Ca, Mg, P, and Y) showed high discriminatory power. These findings demonstrate that sediment fingerprinting provides a robust framework for assessing sediment source contributions in mining-affected watersheds. Full article

Landfill tire fires are complex environmental disasters generating toxic pollutants with severe health risks. This study quantified emission dynamics and toxicological consequences of a large-scale tire fire in an urban ecosystem. A comprehensive source-to-receptor approach was applied, integrating Hybrid Single-Particle Lagrangian Integrated Trajectory (HYSPLIT) atmospheric dispersion modeling with comparison against air quality monitoring data. Soil samples collected from the fireground and surrounding urban allotment gardens were analyzed for tire-specific tracers (Zn) and 16 priority polycyclic aromatic hydrocarbons (PAHs). Human health risks were assessed using Incremental Lifetime Cancer Risk (ILCR), Toxic Equivalency Quotient (TEQ), and Mutagenic Equivalency Quotient (MEQ) metrics. Fire emissions were dominated by particulate matter (PM₁₀: 1.34 t) and PAHs (17.7 kg). Soil at the fire site showed severe contamination (Σ PAHs: 148.9 mg/kg), with benzo[a]pyrene as the primary carcinogen. The cumulative ILCR for children reached 9.7 × 10⁻⁴, exceeding the commonly used upper regulatory benchmark of 10⁻⁴. Dermal contact was identified as the dominant exposure pathway for pyrogenic PAHs. Elevated risk levels persisted at distal residential sites (ILCR: 10⁻⁵–10⁻⁴), indicating long-term environmental contamination Ecological risk quotients (RQ) exceeded unity for PAHs across all fire-impacted locations and for Zn and Cu in the immediate vicinity of the fire scene. These findings demonstrate that acute tire fire events can evolve into persistent terrestrial health hazards, highlighting the critical role of dermal exposure in PAH uptake and the need for long-term environmental monitoring and adaptive land-use management strategies to mitigate chronic health risks in urban populations. Full article

4-Chlorophenoxyacetic acid (4-CPA), a synthetic auxin analog, is employed in agriculture both as a plant growth regulator and as a constituent of herbicide formulations. Consequently, the establishment of simple and rapid detection methods is essential for effective environmental monitoring. This study reports the first development of a homogeneous fluorescence polarization immunoassay (FPIA) for the determination of 4-CPA. The monoclonal antibody (M1), raised against 4-CPA, was evaluated as a recognition element. Furthermore, two fluorescently labeled 4-CPA tracers—with ethylenediamine fluorescein thiocarbamate and aminohexylaminocarbonylfluorescein—were synthesized and purified, and their structures were unequivocally confirmed by high-performance liquid chromatography coupled with high-resolution mass spectrometric detection (HPLC-HRMS). Optimal concentrations of monoclonal antibodies and tracers were established, yielding a limit of detection of 1.2 ng/mL. The assay demonstrated a broad dynamic range of 2.3–300 ng/mL and a rapid analysis time of 15 min. Validation via the standard addition method in authentic open water samples resulted in recovery rates of 98–112%. To address the cross-reactivity with the prevalent herbicide 2,4-dichlorophenoxyacetic acid (2,4-D), two novel strategies were devised and successfully implemented. The first approach involves the concurrent execution of two separate FPIAs—one for 2,4-D and one for 4-CPA—followed by the mathematical resolution of two analyte concentrations from the two measured binding values. The second strategy entails the preliminary selective removal of 2,4-D from sample matrices using affinity chromatography columns with immobilized anti-2,4-D antibodies prior to FPIA for 4-CPA. These proposed methodologies appear highly promising for overcoming the inherent limitations of traditional immunoassays when faced with significant cross-reactivity among structurally analogous compounds. Full article

Introduction: Otoliths have been widely used in recent years as tracers of fish life history, ranging from visual aging to chemical analyses that reconstruct environmental conditions, migration patterns, and metabolic changes. Yet, Iberian endemic or endangered species are understudied. This study focuses on Andalusian barbel (Luciobarbus sclateri), endemic to the southern half of the Iberian Peninsula. Objective: The aim was to evaluate whether otolith chemical profiles can simultaneously support age estimation and reveal the impact of environmental variations, particularly hypoxia. Methodology: Fish were caught in two sites with different environmental properties, including strong hypoxia: the Guadalquivir estuary and the dock of Seville (which is isolated from the main river channel by a ship lock and could, therefore, be used as a control). Otolith chemical composition was analyzed from core-to-edge transects with a laser-inductively coupled plasma mass spectrometer (LA ICP-MS). Results: Patterns of variation in Mg and Mn in relation to hypoxia and environmental conditions are discussed. We visually counted growth rings in the sections, and we found a strong correlation (R² = 0.904) in Mg:Ca peaks with growth rings. Body condition, assessed using Fulton’s condition factor (K), differed between sites, with fish from the estuary exhibiting a lower condition than those from the dock. Conclusions: The strong correlation between counter growth rings and Mg:Ca peaks suggests that chemical analysis could be used as a valid method for supporting aging. The pattern of lower condition in fish from the estuary is consistent with persistent hypoxic events documented in the estuary but not within the dock environment. This whole approach provides a powerful framework to assess habitat quality and support conservation of L. sclateri in the Guadalquivir estuary. Full article

Mapping the spatial distribution of fallout radionuclides in soil is essential for environmental assessments and evaluating potential future radiological risks, while also supporting the interpretation of spatial variability relevant to their use as soil redistribution tracers. However, model performance depends on data characteristics and spatial context, which limits the possibility of defining a universally optimal interpolation method. This study aimed to model the spatial distribution of ¹³⁷Cs at the national scale in Serbia by systematically applying and comparing 33 interpolation techniques, classified as deterministic or stochastic. A total of 193 soil samples, collected in accordance with International Atomic Energy Agency guidelines, were analyzed for ¹³⁷Cs activity using gamma spectrometry. The performance of interpolation techniques was evaluated through leave-one-out cross-validation (LOOCV) and an appropriateness index (AI) for comparison. Among the tested techniques, Empirical Bayesian Kriging Regression Prediction (EBKRP), which incorporates a digital elevation model (DEM) as an additional explanatory variable, achieved the best performance (AI = 0.8548). The resulting map of ¹³⁷Cs activity reveals a pronounced spatial gradient, with values ranging from below 22 Bq/kg to approximately 148 Bq/kg, reflecting the combined effects of initial ¹³⁷Cs deposition following the Chernobyl accident and subsequent long-term soil redistribution. Higher activities are restricted to the hilly and mountainous regions of western, eastern, and southeastern Serbia. Interpolation uncertainty increases in regions with elevated ¹³⁷Cs activities and should be accounted for in spatial interpretation. Full article

Land degradation and declining groundwater availability threaten the sustainability of rural livelihoods across semi-arid regions. This study evaluates the hydrological performance of contour-based trenches as a low-cost and replicable nature-based solution (Nbs) for soil restoration, runoff regulation, and potential distributed managed aquifer recharge (MAR) in Guerrero, Mexico. The structures were installed on 12% slopes and designed using a simplified water balance criterion based on trench storage capacity, runoff coefficient, and representative rainfall events. Each trench was constructed along contour lines with overflow notches and connecting micro-trenches to improve hydraulic continuity, reduce erosion, and enhance infiltration opportunities under degraded field conditions. After one year of field monitoring, the trenches reached an average filling efficiency of approximately 90% per effective rainfall event, with estimated infiltration rates ranging from 0.0069 to 0.011 L·s⁻¹. Soil moisture in the upper soil layer showed a relative increase of approximately 10–18% compared to adjacent untreated areas, while visible reductions in runoff velocity, sediment transport, and surface erosion were observed across the treated plot. Based on trench storage capacity, observed infiltration behavior, and assumed deep percolation fractions, the potential induced recharge was estimated between 216 and 360 m³·yr⁻¹ (43–72 mm·yr⁻¹). These values represent indicative plot-scale estimates rather than direct measurements of aquifer recharge, since no tracer studies or piezometric validation were performed. The results demonstrate that contour-based trenches contribute not only to infiltration enhancement and runoff control, but also to short-term soil restoration and improved water availability in rainfed agricultural systems. Their low-cost implementation, combined with community-based maintenance and adaptation to local environmental conditions, makes them a viable complementary strategy for strengthening decentralized water management, soil resilience, and climate adaptation in semi-arid rural landscapes. However, long-term effectiveness remains dependent on maintenance continuity, institutional support, and local governance conditions. Further multi-year monitoring and direct hydrogeological validation are recommended to improve the design and replicability of decentralized MAR systems. Full article

High-fluoride (F⁻) groundwater is a widespread environmental problem that poses significant risks to human health in many regions worldwide. Understanding the origin, circulation, and evolution of fluoride-rich groundwater is therefore essential for effective groundwater management and mitigation strategies. In recent years, stable isotope techniques have helped to address key gaps in understanding the hydrogeochemical processes governing F⁻ enrichment, particularly regarding the source identification and water-rock interaction mechanisms that remain poorly constrained. This study reviews the applications of hydrogen–oxygen, strontium–calcium, and lithium–boron isotopes in research on high-F⁻ groundwater systems. Hydrogen and oxygen isotopes (δ²H and δ¹⁸O) are widely used to identify groundwater recharge sources, mixing processes, and evaporative effects, thereby providing key constraints on the origin of fluoride-rich groundwater. Strontium and calcium isotopes (⁸⁷Sr/⁸⁶Sr and δ^44/40Ca) serve as effective tracers of water-rock interactions and associated hydrogeochemical processes, including mineral weathering and dissolution, cation exchange, and secondary mineral precipitation, which play critical roles in fluoride mobilization and enrichment. In addition, lithium, and boron isotopes (δ⁷Li and δ¹¹B) provide valuable insights into the influence of geothermal fluids and deep hydrothermal processes on fluoride accumulation in groundwater systems. Overall, the integrated application of these stable isotope systems offers a robust framework for elucidating the formation mechanisms and evolutionary pathways of high-F⁻ groundwater. Moving beyond qualitative source identification, future research should prioritize the development of Bayesian isotope mixing models that explicitly quantify uncertainty in fluoride source apportionment and utilize sensitivity analysis to test competing hydrogeochemical mechanisms. Full article