Search Results (5,999)

Oil–particle aggregate (OPA) formation, fragmentation, and settling govern the fate of oil that strands on sediment-rich shorelines, yet no publicly accessible, size-resolved software tool currently couples these three processes within a single population balance framework. Existing models either resolve OPA formation without breakup or resolve breakup from a prescribed initial distribution, forcing practitioners to chain tools manually. We address this gap by developing OPA-Z, a software tool whose kernel unifies (i) A-DROP coagulation/attachment, (ii) binary fragmentation and shell shredding, and (iii) an analytical advection–diffusion settling solution within a single discretized population balance model. The integrated kernel is wrapped in a graphical user interface (GUI) that enables non-expert scenario testing on a web-hosted application. Model inputs include oil properties (interfacial tension, viscosity, density), particle properties (sand, clay, mixtures, sizes, density), turbulence intensity, and water depth. Outputs include time-resolved OPA size distributions, oil trapping efficiency (OTE), oil-to-sediment ratio (OSR), and cumulative oil settled to the bed. The model operates in a pulse mode of oil release that simulates a slick arriving at the shorelines, representative of nearshore spill response scenarios such as beached oil remobilization or slick stranding events. Model fidelity is demonstrated by reproducing benchmark coagulation data in laboratory systems. The software is designed to integrate with GIS-based particle fields, supporting fast, transparent assessments of nearshore OPA fate to respond to oil spills and for contingency planning. Full article

Against the backdrop of global climate change and carbon neutrality strategies, land use carbon emissions have become a prominent topic amid regional efforts toward low-carbon transformation. However, existing studies on land-use carbon emissions have predominantly focused on humid and economically developed regions, while the unique carbon metabolism pathways of arid oasis–desert ecosystems, which are characterized by extremely low environmental carrying capacity and high sensitivity to land-use disturbance, remain largely unexplored. This study takes the oasis urban cluster in the Tarim Basin in southern Xinjiang Uygur Autonomous Region as the research object. This region belongs to a typical oasis–desert composite ecosystem, with a simple structure and low environmental carrying capacity (reflected by sparse vegetation cover <20%, annual precipitation <100 mm, extremely limited water resources, and high sensitivity to land disturbance). Its carbon metabolism pathway (i.e., the dynamic balance between carbon sources and sinks induced by land-use change) is fundamentally different from that in humid areas, and thus merits dedicated investigation. This study selects the period from 2000 to 2020 as the research period, which completely covers the acceleration period of urbanization and agricultural expansion in the Tarim Basin oasis urban cluster since the advancement of China’s Western Development Initiative. The data have a temporal resolution of 5 years (samples in 2000, 2005, 2010, 2015, 2020) and a spatial resolution of 30 m for land use and prefecture level for socio-economic indicators. Based on this, to fill the above-mentioned research gap, a research framework integrating the carbon emission coefficient accounting method, landscape pattern index, spatial autocorrelation analysis and geographic detector is adopted. Specifically, this study aims to systematically quantify the spatio-temporal evolution of land use carbon emissions and identify the most robust driving factors in the Tarim Basin oasis urban cluster by integrating multiple models, an approach that has not been previously applied to arid oasis regions. The research results show: (1) Based on the carbon emission coefficient method, total carbon emissions increased from 1.4455 million tons to 22.364 million tons, following a ‘slow-then-fast’ trajectory. In terms of temporal evolution, the study period can be further divided into three sub-stages: 2000–2005 (slow diffusion, with emission center skewed toward the northern energy-intensive zone), 2005–2015 (rapid restructuring, characterized by a ‘unipolar surge’ in Aksu and spread to the central oasis belt), and 2015–2020 (high-intensity stabilization, forming a cross-regional emission belt). Meanwhile, the land use structure has undergone a significant transformation. Construction land and cultivated land have continued to expand, while ecological land has significantly shrunk, resulting in a complex transformation pattern of oasis–desert ecotone. (2) The overall landscape became increasingly fragmented and diversified, the integrity of ecological space was damaged, and the regional carbon sink function was weakened. (3) The spatial autocorrelation analysis indicates that the spatial distribution of carbon emissions shows a heterogeneous pattern, forming a high-emission concentration area centered around Aksu-Bayingol. However, the global Moran’s I index is negative (such as −0.171 in 2020, p > 0.05), suggesting that carbon emissions have not formed a significant spatial clustering. (4) Carbon emissions are dominated by human and economic factors, and the interaction of factors is significant. The geographic detector identifies population density (average q value 0.904) and the proportion of construction land (average q value 0.858) as the key determinants of spatial variation in carbon emissions, reflecting the sensitive response of the human-nature system of arid zones to the urbanization process. These findings not only clarify the spatio-temporal features and driving forces of land use carbon emissions in the Tarim Basin oasis urban cluster, but also provide a replicable analytical framework for carbon-emission research in other arid and semi-arid regions worldwide. Based on these findings, we discuss the unique driving mechanisms of carbon emissions in arid regions, conclude that construction land expansion and population density are the dominant factors, and recommend a three-tier zoning governance system (carbon source control zone, carbon sink enhancement zone, coordinated development zone) for low-carbon spatial planning in arid areas. Full article

The Sumapaz páramo, the most extensive continuous páramo complex on a global scale and a strategic component in the hydrological regulation of central Colombia, is undergoing a progressive ecohydrological degradation whose integrated characterization through multitemporal biophysical indicators remains limited. To address this gap, the present study examines the transformation dynamics of the system by articulating four analytical components: precipitation modeling based on IDEAM stations (1995–2025), thermal trend analysis from WorldClim grids (2000–2024), multitemporal spectral analysis of four normalized difference indices (NDVI, NDWI, NDSI, NBR) derived from Landsat imagery (2000–2025), and Corine Land Cover cartography (2000–2018). The findings reveal a spatial decoupling between the precipitation distribution, which tends to shift toward lower altitudinal belts, and the storage areas in peat and Andosols of the páramo core, with a consequent reduction in effective recharge regardless of the total precipitated volume. Paradoxically, an almost complete contraction of surfaces with a positive water signal coexists with the expansion of photosynthetic activity, a phenomenon attributable to processes of shrub encroachment, thermophilization, and nutrient enrichment rather than to a functional recovery of the ecosystem. The cartographic analysis, in turn, confirms the advance of agricultural and livestock uses over native regulating covers. The convergence of these vectors configures a multivectorial degradation scenario that escapes monitoring based on a single index and that demands management strategies oriented simultaneously toward anthropic pressure, the spatial redistribution of precipitation, and the implementation of integrated ecohydrological surveillance systems. Full article

To address the potential ecological risks and environmental persistence of organosilicon-fluorine viscosity reducers in conventional silicone-fluoride drilling fluid systems, this work designs and synthesizes a non-organosilicon-fluorine, high-temperature, comb-shaped zwitterionic polymer viscosity reducer, AD-XSJ. The viscosity reducer is prepared via aqueous free-radical polymerization of acrylic acid (AA), acrylamide (AM), 2-acrylamido-2-methylpropane sulfonic acid (AMPS), and dimethyl diallyl ammonium chloride (DADMAC), and it exhibits low molecular weight, uniform molecular weight distribution, and excellent thermal stability. Analyses by FT-IR, thermogravimetry, particle size, zeta potential measurements and Electrostatic potential (ESP) demonstrate that AD-XSJ dismantles the bentonite network structure through the synergistic combination of hydrogen-bonding adsorption and electrostatic repulsion, releasing trapped free water and thereby substantially reducing viscosity and gel strength. Compared with conventional organosilicon-fluorine viscosity reducers, AD-XSJ exhibits superior viscosity reduction capability under high-solid, high-temperature, and high-salinity calcium-contamination conditions, achieving viscosity reduction rates of 33.3% and 50.0% in fluids contaminated with 10.0% NaCl and 1.0% CaCl₂, respectively. In field applications under conditions of high bentonite content and calcium contamination, the viscosity reduction rates reach 57.7% and 62.5%, accompanied by markedly improved rheological properties and an average borehole enlargement rate of only 5.7%, indicating effective shale inhibition and anti-sloughing performance. Integrating efficient viscosity reduction, dispersion stabilization, and inhibition capabilities, this viscosity reducer can replace traditional organosilicon-fluorine products, reduce potential hazards to aquatic ecosystems at the source, and holds considerable promise for engineering and environmentally conscious deployment. Full article

Urban water security in many cities in the Global South is increasingly challenged by ageing infrastructure and the presence of persistent chemical contaminants. This study investigated the Harare metropolitan water continuum between 2020 and 2024 using a longitudinal, systems-oriented observational framework encompassing wastewater discharge, surface water reservoirs, drinking water treatment, and municipal distribution networks. A three-stage approach was employed, comprising qualitative screening for selected pharmaceuticals at the Lake Chivero water–sediment interface in 2020, spatial assessment of physicochemical stability across the treatment and distribution system in 2021, and targeted qualitative evaluation of pharmaceutical and agrochemical occurrence in wastewater-impacted matrices in 2024. Sulfamethoxazole and trimethoprim were qualitatively identified using high-performance liquid chromatography (HPLC), while atrazine was confirmed by gas chromatography–mass spectrometry (GC–MS). These analyses indicated the continued presence of pharmaceutical and agrochemical residues within wastewater-impacted aquatic compartments associated with the Harare water supply. Physicochemical monitoring revealed elevated ammonia concentrations and reduced free residual chlorine across sections of the distribution network. These conditions coincided with detectable heterotrophic bacterial regrowth at distal consumer endpoints. Phenotypic antimicrobial susceptibility testing of bacterial isolates recovered at the source interface showed limited inhibition responses to sulfamethoxazole and trimethoprim under the experimental conditions used. While the observational nature of this study precludes causal inference, the co-occurrence of chemical residues, physicochemical instability, and bacterial isolates exhibiting reduced inhibition responses highlights conditions of potential relevance for antimicrobial resistance risk within wastewater-influenced urban water systems. These findings underscore the importance of integrated water management strategies addressing wastewater control, source water protection, and distribution system integrity within a One Health context. Full article

Deterministic empirical formulas often fail to capture the epistemic uncertainties of dam failure mechanisms, leading to biased risk estimations. To address this, we propose the Probabilistic Hydro-Risk Forecasting System (PHRFS), a stochastic framework integrating Latin Hypercube Sampling (LHS) with HEC-RAS 2D hydrodynamic modeling. Applied to the Honghu-Erji Reservoir (Inner Mongolia), an ensemble of 60 stratified scenarios was generated based on a multi-model envelope of breach parameters and simulated over a $12.5\mathrm{m}$ ALOS PALSAR DEM using the Full Momentum Shallow Water Equations with the Eulerian–Lagrangian method (SWE-ELM). The SWE-ELM simulations reveal a heavy-tailed distribution of peak discharge (mean $2.65\times {10}^4{\mathrm{m}}^3/\mathrm{s}$; max $5.85\times {10}^4{\mathrm{m}}^3/\mathrm{s}$), significantly exceeding deterministic estimates. Sensitivity analysis identifies a physical dichotomy: breach depth ($D_b$) primarily controls flood magnitude ($r\approx 0.7$), whereas formation time ($t_f$) governs the arrival timeline. This temporal uncertainty propagates downstream, creating a distinct longitudinal gradient in SWE-ELM-derived warning time—ranging from rapid onset ($33.0\pm 19.3\min$) in proximal zones to a substantial lead time ($33.1\pm 4.2\mathrm{h}$) in the distal Hailar District. Consequently, a moderate coupling ($r=0.65$) emerges between economic loss and loss of life, while their spatial patterns remain strongly differentiated by warning time and exposure. Upstream settlements face high mortality risks due to insufficient evacuation windows, whereas the downstream urban center faces high economic exposure (∼1.57 billion CNY) but limited life loss (∼12.15 persons). These findings provide a scientific basis for differentiating emergency strategies, shifting from immediate life-saving in upstream reaches to asset protection in downstream areas. Full article

Pressure management in water distribution networks requires the integration of hydraulic modeling and discrete device allocation, naturally leading to mixed-integer nonlinear programming (MINLP) formulations. This study presents a MINLP problem for the joint placement of pressure-reducing valves and pumps as turbines, using the Global Excess Power index to quantify energy inefficiencies related to excess pressure and leakage. The formulation incorporates nonlinear hydraulic equations, leakage–pressure relationships, and operational constraints. Application to a real network illustrates model behavior and highlights the computational challenges associated with energy-oriented pressure control in practical water distribution systems. Full article

This study investigates the spatial variability of benthic foraminiferal assemblages across the shoreface–inner shelf transition of the Porto Pino coastal system (SW Sardinia, western Mediterranean). Porto Pino is a microtidal, wave-dominated embayment characterized by an environmental gradient extending from siliciclastic shoreface sands to mixed bioclastic sediments associated with the Posidonia oceanica meadow. A total of 33 sediment samples were analyzed for grain size, benthic foraminiferal assemblages, morphotypes and diversity indices. Cluster analysis and Principal Component Analysis (PCA) were used to investigate the spatial variability of the assemblages. Three main benthic foraminiferal assemblages were identified, each corresponding to a distinct benthic habitat: shallow unvegetated shoreface sands, a transitional zone near the upper limit of the P. oceanica meadow, and deeper mixed bioclastic sediments associated with its lower boundary. The distribution of the foraminiferal assemblage reflects the combined influence of hydrodynamic energy, substrate composition, water depth, and proximity to the meadow. Diversity indices indicate generally low-stress environmental conditions, whereas morphotype composition reflects changes in habitat structure and substrate characteristics along the shoreface–inner shelf gradient. These results demonstrate that benthic foraminifera effectively track environmental and sedimentological gradients in Mediterranean embayed systems and highlight their value for environmental reconstructions and biomonitoring applications. Full article

Sustainable management of hydrogeological systems that supply water and exhibit high hydrologic complexity can be studied through pragmatic numerical modeling supported by field-constrained conceptualization. This study develops a local-scale three-dimensional groundwater flow numerical model using FEFLOW for the Barranca Lebrija settlement in Aguachica town, where the Lebrija River, the Musanda floodplain lake, and groundwater system converge. The numerical model incorporates: (i) the three-dimensional distribution of geological units and lithology; (ii) water level observations from the Musanda floodplain lake; (iii) stage records from the Lebrija River; (iv) boundary conditions and flux estimates inherited from a previous regional groundwater model; and (v) hydraulic heads from two monitoring wells and five community wells. Steady-state and transient conditions were calibrated, and a sensitivity analysis was performed to identify the parameters that most strongly control surface water–groundwater exchange. The simulations reproduce seasonal groundwater level trends and demonstrate the exchange pathways among the river, floodplain lake, and groundwater system. Results indicate dual behavior: during wet periods, flooding of the Musanda floodplain lake driven by high river levels seeps into the underlying aquifer, whereas in dry periods the floodplain lake reverses its role and becomes a principal discharge boundary. This local-scale, boundary-driven approach provides a computationally tractable framework to quantify SW–GW exchange in data-scarce tropical floodplains and supports monitoring design and water-supply management. Full article

Micro gas turbines are small-scale systems based on the Brayton cycle and represent a viable solution for distributed generation. However, the main limitation to extending their application range is the cycle efficiency. Numerical and experimental analyses of power plants are important for evaluating the energy performance of different cycle configurations. Another issue is the formation of pollutants, including nitrogen oxide emissions. The humidified gas turbine cycle is one alternative to address these problems. Among wet cycles, the regenerative evaporative cycle offers a means to improve gas turbine efficiency. However, this configuration is less commonly discussed in the literature, which focuses more on steam injection cycles. Therefore, this paper presents an energy, exergetic, and nitrogen oxide formation analysis of an evaporative regenerative cycle for a 30 kW micro gas turbine across the gas turbine load range to define the most suitable operational system regime. The novelty of this study lies in an integrated assessment that simultaneously covers the operation of the micro gas turbine at full and part load under different conditions of water injection into the evaporator. The analyses conducted show that, for the micro turbine operating at full load, the benefits in terms of energy and pollutant formation are positive for all fractions of injected water. However, decreases in cycle performance are reported at power outputs below 19 kW compared with the dry cycle. Although nitrogen oxide formation decreases with increasing water injection, the reduction is less pronounced at lower microturbine power levels. Full article

Maintaining effective fluid-loss control in water-based drilling fluids under coupled high-salinity, high-temperature, and high-density conditions remains a critical challenge in deep and ultra-deep drilling operations. In this study, a low-molecular-weight polymer fluid-loss additive (LM-ASQF) was synthesized via redox-initiated copolymerization of acrylamide, dimethyldiallylammonium chloride, and sodium allyl sulfonate. The synthesis route and proposed polymer structure were further illustrated to clarify the incorporation of amide, quaternary ammonium, and sulfonate functional units within the LM-ASQF molecular architecture. The polymer exhibited a controllable number-average molecular weight of 18.2–29.4 kDa with a unimodal distribution. Thermal analysis confirmed that no main-chain-dominated degradation occurred below 220 °C, indicating structural stability under high-temperature conditions. In drilling-fluid systems containing NaCl, CaCl₂, and mixed salts (0–20%), LM-ASQF maintained stable rheological properties, with apparent viscosity ranging from 26.1 to 41.6 mPa·s, while the API fluid loss was controlled within 5.8–11.2 mL. After thermal aging at 220 °C for 16 h, the API fluid loss remained below 13 mL in both freshwater and mixed-salt systems. In high-density systems (1.80–2.40 g/cm³), the drilling fluids preserved continuous rheological structures and showed no abrupt increase in filtration. Mechanistically, fluid-loss control was primarily attributed to synergistic interfacial adsorption of amide groups, hydration stabilization induced by sulfonate functionalities, and particle rearrangement-driven filter-cake densification, rather than viscosity enhancement through long-chain entanglement. This mechanism enables effective filtration control without excessive viscosity increase, thereby maintaining rheological compatibility under complex conditions. These results demonstrate that the low-molecular-weight design strategy provides a reliable approach for achieving stable fluid-loss control in water-based drilling fluids under high salinity, elevated temperature, and high-density conditions. Full article

Climate change is profoundly altering precipitation and temperature patterns across high-altitude regions worldwide. The Qinghai–Tibet Plateau (QTP), known as the “Third Pole” and the “Asian Water Tower,” is among the most climate-sensitive regions and plays a critical role in the Asian water cycle, cryospheric stability, and regional ecological security. However, the complex topography and diverse climate of the QTP result in substantial discrepancies among meteorological products over this region, highlighting the necessity of a comprehensive evaluation against in situ observational records. Using records from 85 stations (1960–2022), we evaluated four products: China’s 1 km monthly dataset (CN_1km), the Climatic Research Unit gridded Time Series (CRU TS), the fifth-generation European Centre for Medium-Range Weather Forecasts land reanalysis (ERA5-Land), and TerraClimate—selected for their long-term continuity, diverse product types, and widespread regional applications. Subsequently, we compared these products with Earth System Model (ESM) simulations from the NASA Earth Exchange Global Daily Downscaled Projections based on CMIP6 (NEX–GDDP–CMIP6). This evaluation was conducted using key statistical metrics, including the coefficient of determination (R²), root mean square error (RMSE), Kling–Gupta efficiency (KGE), and bias, together with spatially distributed long-term trend analysis using the Sen’s slope estimator and Mann–Kendall test. Station-based evaluation shows that temperature datasets generally outperform precipitation datasets, with monthly mean temperature yielding R² values of 0.85–0.94, RMSE values of 2.38–4.79 °C, and KGE values ranging from −0.04 to 0.86. Monthly precipitation R² values of 0.74–0.81, RMSE values of 20.60–36.12 mm, and KGE values of 0.42–0.86. For anomalies, temperature performs better (R² = 0.41–0.67; RMSE = 0.80–1.41 °C) than precipitation (R² = 0.28–0.44; RMSE = 16.87–20.73 mm). Overall, CN_1km and TerraClimate provide the most reliable station-based temperature estimates, while TerraClimate shows the most robust precipitation performance. All four datasets consistently indicate warming and wetting trends, with temperature rising at 0.21–0.24 °C decade⁻¹ and precipitation increasing at 4.5–5.8 mm decade⁻¹, featuring stronger warming in the west and greater precipitation increases in the northeast; however, the precipitation trend in ERA5-Land does not reach statistical significance. NEX–GDDP–CMIP6 simulations reproduce comparable warming and moistening signals (0.22–0.23 °C decade⁻¹ and 4.1–4.7 mm decade⁻¹), though their precipitation distribution differs markedly from the other datasets, with the discrepancy primarily reflected in a pronounced latitudinal gradient. These results provide a reference for the selection of climate-forcing datasets in hydrological, ecological, and cryospheric studies across the QTP. Full article

Microplastic pollution in tropical urban rivers has become an increasing environmental concern due to rapid urbanization, inadequate waste management, and hydrological transport processes. This study investigated the occurrence, characteristics, and spatiotemporal distribution of microplastics in the Can Tho River, Vietnam, along an urban–peri-urban–rural gradient during dry and wet seasons. Surface-water samples were collected at 15 sites and analyzed for microplastic abundance, density, shape, color, and size composition using stereomicroscopic identification and statistical analyses. Microplastics were detected at all sampling sites in both seasons, indicating widespread contamination throughout the river system. Although seasonal differences in overall abundance and density were not statistically significant at the basin scale, clear spatial variability was observed, particularly in urban and peri-urban regions. Fibers and fragments were the dominant shapes, while blue, purple, and green particles were the most common color categories. Particles larger than 1000 µm accounted for the largest proportion of detected microplastics, and continuous size-distribution analysis revealed broadly similar overall distributions, although a greater proportion of smaller particles was observed during the dry season. The results suggest that hydrological conditions, urbanization, and land-use characteristics may contribute to the observed spatial and seasonal patterns of microplastic distribution in the Can Tho River. Peri-urban zones exhibited the greatest seasonal variability, highlighting their role as transitional areas that may influence microplastic redistribution in tropical river systems. This study provides baseline information for understanding microplastic pollution in the Mekong Delta and supports future river management strategies. Full article

Trace water is one of the most critical matrix contaminants in ultra-high-purity (UHP) process gases, like argon (Ar), nitrogen (N₂), and many others. Even trace amounts can severely degrade the quality of many products that are reliant on these gases. Despite its importance to advanced technology sectors, notably semiconductor manufacturing, it has proven quite difficult to realize preparative or analytical trace water metrology over the full amount fraction range needed or in the broad spectrum of industrially relevant matrix gases. Within the EU-funded PROMETH2O project consortium, this challenge has been addressed through the development or significant improvement of traceable measurement methods and standards spanning 5 nmol⋅mol⁻¹ to 5 µmol⋅mol⁻¹, tailored for use in UHP process gas production, such as Ar, N₂ and clean dry air (CDA). The measurement ranges were extended and the uncertainties were improved while being consistent with the current best practice at primary humidity standard laboratories. The developed standards provide combined standard uncertainties ranging from approximately 0.4 % to 1.5 % in water vapor amount fraction and from 0.03 °C to 0.07 °C in frost-point temperature, while the comb-assisted CRDS system achieves detection limits in the sub-ppb to ppt range. These capabilities were validated in applications that are relevant to process instrumentation and the gas industry. A distributed metrological infrastructure at various European national metrology institutes and partner sites now provides SI-traceable trace water measurements in UHP gases, strongly supporting and extending the calibration capabilities for the gas and semiconductor industries and the associated stakeholders. Full article

Introduction: Oil pulling therapy has gained increasing attention as a natural oral hygiene practice; however, evidence regarding its clinical effectiveness remains limited and inconclusive. This study aimed to evaluate the effects of oil pulling therapy on dental plaque regrowth and tooth discoloration compared with chlorhexidine. Materials and Methods: One hundred systemically healthy dental students were randomly allocated to five groups: chlorhexidine, coconut oil, black cumin seed oil, terebinth oil, and distilled water. Following professional prophylaxis, participants refrained from mechanical oral hygiene for four days and used their assigned intervention twice daily. Plaque accumulation was assessed using the Turesky modification of the Quigley–Hein Plaque Index, gingival inflammation using the Gingival Index, and tooth color using CIELAB color difference measurements. Data were analyzed using one-way ANOVA or Kruskal–Wallis test with appropriate post hoc tests, depending on the distribution of data. Results: Plaque scores differed significantly among groups (p < 0.001), with chlorhexidine showing superior plaque inhibition compared with all oil-based interventions and distilled water. Gingival index values were lowest in the chlorhexidine group, although differences among oil groups were not statistically significant. Tooth discoloration was significantly greater with chlorhexidine than with all oil-based interventions (p < 0.001). Conclusions: Oil pulling therapies demonstrated lower anti-plaque efficacy than chlorhexidine but resulted in less tooth discoloration. These findings suggest that oil pulling may serve as an adjunct rather than an alternative to conventional plaque control. Full article