Search Results (314)

Polders are typical semi-artificial and human-dominated ecosystems widely distributed in the middle and lower reaches of the Yangtze River Basin. They serve as important sinks and sources of nitrogen (N) and phosphorus (P) in agricultural watersheds. Long-term intensive human intervention substantially alters the hydrological and biogeochemical processes of polder ecosystems, resulting in complex and uncertain effects on water quality that remain insufficiently understood. This study conducts a systematic literature review and narrative synthesis of evidence on N and P transport in polders across the middle–lower Yangtze River plain. The evidence is derived from field monitoring, plot experiments, and numerical simulations. The review focuses on the spatiotemporal patterns of nutrient variation, sink–source conversion functions of ditches and small ponds, drivers of nutrient loss, and current research bottlenecks under artificial sluice-pump regulation. The synthesized results indicate that polders exhibit a distinctive nutrient transport pattern characterized by dispersed in situ retention under conventional water management and concentrated pulse export during drainage events. Artificial sluice-pump operation drives episodic nutrient export throughout the crop growth period, imposing persistent pressure on the water quality of downstream rivers and lakes. N and P transformations are jointly controlled by natural hydrological fluctuations and human activities. Within agricultural lands of polders, fertilizers account for 73.3% of total nitrogen inputs and 87.9–93.5% of total phosphorus inputs. Crop harvesting and regulated drainage constitute the two dominant pathways for nutrient export. Hydraulic regulation prolongs water residence time in polder ditches and ponds, resulting in retention efficiencies of 52–65% for allochthonous N and P. However, seasonal flooding and waterlogging can induce sediment hypoxia and endogenous nutrient release, thereby causing secondary internal pollution and increasing the eutrophication risk of adjacent receiving water bodies. Three major research gaps are identified: insufficient long-term continuous multi-indicator monitoring data, limited model applicability for simulating human-regulated hydrology–nutrient coupling, and poorly defined critical thresholds for polder sink–source functional reversal. This regional systematic review advances the understanding of human–hydrology–nutrient coupling mechanisms in Yangtze River polder systems. It also provides targeted theoretical support for agricultural non-point source pollution mitigation and water environment management in floodplain agricultural areas. Full article

The Pinglu Canal, the first river-to-sea canal project since the founding of the People’s Republic of China, reshapes basin-scale ecosystem services by altering land use/land cover, landscape patterns, and soil–water processes. This study assesses spatiotemporal variations in net primary production (NPP), soil conservation, water yield, and nitrogen/phosphorus output in the Pinglu Canal Basin from 2000 to 2024. Hotspot analysis, the interannual fluctuation index, Random Forest and Shapley additive explanations, climate–NPP residual analysis, and Geodetector were integrated. The results indicate that: (1) Over the past 25 years, ecosystem services have generally improved, with NPP increasing significantly and nitrogen/phosphorus outputs declining; northern hilly and low-mountain forests formed stable service supply areas, whereas water yield was more prominent in southern plains and river valleys. Water yield showed the strongest interannual fluctuation, while soil conservation remained relatively stable. (2) Hotspot stability was mainly regulated by population density, normalized difference vegetation index (NDVI), elevation, and precipitation, with evident nonlinear threshold effects. When the NDVI reaches about 0.63, the NPP and nutrient retention capacity are significantly enhanced, indicating that vegetation coverage and community structure can exert their ecological regulation functions effectively after reaching a certain level. (3) During construction, negative NPP disturbances expanded along the canal. The Geodetector results showed that while the explanatory power of population density was enhanced during the construction stage of the Pinglu Canal, precipitation, NDVI, and topographic/hydrothermal conditions remain foundational constraints for ecosystem services spatial differentiation. Furthermore, interactions, such as population–NDVI and population–precipitation, generally manifest as bivariate enhancement. This study supports ecological monitoring, risk warning, and zoned restoration for large linear infrastructure projects. Full article

Urban flood control basins without forced drainage operate as one-shot systems: they must perform within a single event and cannot empty themselves until it ends. The timing of gate closure is therefore decisive—closing early wastes storage, whereas closing late lets stored water drain back to the falling channel—yet the recovery-based Reliability–Resiliency–Vulnerability (RRV) framework does not capture this trade-off. We reformulated the RRV indices for non-drainable basins and applied them to a full-scale experimental channel reproduced with high-resolution Structure-from-Motion terrain and simulated with the two-dimensional Nays2D Flood model. The three indices provide complementary performance dimensions: Reliability describes temporal threshold attainment, Resiliency describes event-integrated retention, and Vulnerability describes the maximum instantaneous deficit. Five gate-closing scenarios were compared with the no-gate reference. For this single-site, single-hydrograph event on the calibrated 211 × 111 grid, the net inflow at the inlet reversed at about t = 2611 s, and closures made before this instant avoided backflow. Closing just before reversal (t = 2574 s) gave the highest Resiliency (0.995), the lowest Vulnerability (0.074), and the largest net inflow (1487 m³) among the tested scenarios; delaying closure reduced Resiliency to 0.809 and raised Vulnerability to 0.255. The exact values are specific to the adopted grid and event, whereas the principal result is the reversal-based closure window. The method identifies this window using observed or forecast water level or flow direction information, without requiring new forced-drainage or pumping infrastructure. Full article

Accurate characterization of pore-fluid mobility is essential for evaluating tight sandstone reservoirs. This study investigates ten tight sandstone samples from the Sangonghe Formation in the Junggar Basin using petrophysical measurements, X-ray diffraction, scanning electron microscopy, low-field nuclear magnetic resonance (NMR), and multifractal analysis. Saturated–centrifugation NMR results show that the conventional single-T₂-cutoff model cannot fully separate bound and movable fluids. A dual-cutoff framework was therefore used to classify pore fluids into totally bound, partially movable, and totally movable states. The experimentally determined T_2C1 and T_2C2 values range from 0.127 to 0.582 ms and 155.340 to 265.210 ms, respectively. An adaptive second-order difference method was further applied to the fully saturated T₂ spectrum to estimate the dual cutoffs. Within the investigated dataset, the model-derived values show strong agreement with the centrifugation-derived results, with MAPE values of 3.040% for T_2C1 and 3.820% for T_2C2. Correlation, multifractal, and grey relational analyses indicate that T_2C1 is more strongly associated with clay-mineral-related fluid retention and pore heterogeneity, whereas T_2C2 is more closely associated with porosity and permeability. These results demonstrate the potential of the proposed approach for NMR-based evaluation of fluid mobility in tight sandstone, although further validation using larger and more diverse datasets is required. Full article

Dongting Lake is one of the most important floodplain lakes in China and plays a critical role in regional flood regulation, ecological conservation, and water-resource management. Understanding long-term variations in lake water storage is therefore essential for evaluating hydrological responses to climate change and human activities. In this study, a hydrodynamic-simulation-based storage estimation framework was developed to quantify wet-season water storage variations in Dongting Lake during 1990–2022. The proposed estimation equation showed strong agreement with hydrodynamic-simulation-derived water storage, with a coefficient of determination (R²) of 0.972 and a root mean square error (RMSE) of 0.86 billion m³. Results indicate that both annual peak water storage and mean wet-season water storage exhibited significant declining trends over the study period. Mann–Kendall analysis revealed an evident decrease in peak storage after 2008 and a major hydrological transition around 2003, corresponding to the initial operation of the Three Gorges Dam (TGD). Comparative analysis showed that the average annual peak storage decreased from 17.27 billion m³ during 1990–2002 to 14.41 billion m³ during 2003–2022, while mean wet-season storage decreased from 8.16 billion m³ to 7.23 billion m³. Reduced inflow from both the Yangtze River and the Four Rivers was identified as the dominant factor controlling the decline in water storage. Although lakebed erosion increased the potential storage volume associated with bathymetric evolution by approximately 0.95 billion m³, its contribution was substantially smaller than the reduction in inflow runoff. Although long-term storage decreased, Dongting Lake retained substantial flood-regulation capacity, with only limited changes observed in flood-retention performance during major flood events. The findings contribute to a better understanding of long-term hydrological changes in Dongting Lake and provide useful information for flood control and water-resource management in the middle Yangtze River basin. Full article

Methane production from water-bearing coal reservoirs is governed not only by methane adsorption capacity but also by the accessibility of adsorption domains and the efficiency of pore-scale transport during pressure depletion. However, the interfacial mechanism by which coal wettability and water occurrence regulate methane adsorption–desorption reversibility remains insufficiently understood. In this study, three representative Ordos Basin coal samples with different pore structures and surface polarities, denoted as OBC-L, OBC-M, and OBC-H, were investigated to explore the pore-scale mechanisms governing water-mediated methane storage and release rather than to establish basin-wide statistical relationships. A combined experimental workflow involving N₂ adsorption–desorption, FTIR and XPS analyses, contact angle and Zeta potential measurements, low-field NMR, high-pressure methane adsorption–desorption tests, kinetic modeling, hysteresis evaluation, and Pearson correlation analysis was used to clarify the coupling among pore structure, coal–water interfacial properties, water occurrence, methane storage, and methane release. The results show that OBC-H possesses the strongest dry-state methane storage potential, with the BET surface area increasing from 5.82 m²/g for OBC-L to 12.94 m²/g for OBC-H and the fitted Langmuir volume (V_L) reaching 22.3 cm³/g. Nevertheless, OBC-H also shows stronger water affinity, as reflected by an increase in the XPS-derived O/C atomic ratio from 0.118 to 0.186, a decrease in contact angle from 82.6° to 51.8°, and an increase in bound water fraction from 46.3% to 69.4%. With the transition from dry to saturated conditions, the fitted V_L of OBC-H decreases from 22.3 to 15.2 cm³/g, while the Langmuir pressure (P_L) increases from 1.38 to 3.00 MPa, indicating a simultaneous reduction in the model-estimated maximum methane adsorption capacity and apparent methane affinity. More importantly, the desorption results demonstrate that high adsorption capacity does not necessarily correspond to high methane deliverability. For OBC-H, the final desorption efficiency decreases from 79.6% to 54.2%, the effective diffusion coefficient decreases from 2.74 × 10⁻¹¹ to 0.86 × 10⁻¹¹ m²/s, and the hysteresis index increases from 12.8% to 36.4% under saturated water conditions. Correlation analysis further confirms that bound water fraction is positively associated with adsorption–desorption hysteresis but negatively associated with desorption efficiency, desorption rate constant, and effective diffusion coefficient. These findings are consistent with two distinct water-mediated constraints: adsorbed/bound interfacial water contributes to surface-site shielding, whereas capillary and saturated water occupation contributes to pore-throat transport restriction; together, these effects reduce methane release efficiency and enhancing desorption irreversibility. This study provides an interfacial interpretation of methane deliverability based on representative water-bearing coal samples and offers a mechanistic basis for understanding wettability- and water-retention-related transport constraints; broader applicability across the Ordos Basin requires validation using a larger number of samples from different coal seams and reservoir settings. Full article

Sustainable Urban Drainage Systems (SUDSs) have recently emerged as an alternative to traditional drainage systems, offering better stormwater management and improved resilience in road infrastructure. However, their uptake is still slow in Small Island Developing States (SIDSs) such as Mauritius. The aim of this study was to understand the potential for integrating various SUDS in major road projects and identify existing barriers and potential enablers. Semi-structured interviews with 20 highway experts showed that for Mauritius, the most feasible solutions were swales, soakaways and infiltration trenches, due to their ease of implementation and lower costs. However, topography, soil infiltration and water table levels pose significant challenges. Other SUDS types, such as permeable paving areas, retention/detention ponds, infiltration basins and constructed wetlands were not considered favourably. Potential enablers identified included enhancing the local technical expertise on SUDS, developing adapted guidance documents and policies and the implementation of pilot projects as showcases for SUDS efficacy in managing stormwater. The study has contributed to identifying the most suitable SUDS components for implementation in road projects in Mauritius and pathways to increase their adoption. Full article

The Paraopeba River basin has been exposed to long-term anthropogenic pressures, including urbanization, wastewater discharge, land-use changes, and mining. These impacts were intensified by the Brumadinho tailings dam collapse in 2019, which released approximately 1.6 million m³ of iron-mining tailings into the Paraopeba River. This study evaluated spatial and temporal dynamics of zooplankton communities and their relationships with environmental gradients. Eighteen sampling campaigns were conducted at nineteen monitoring sites, integrating physicochemical variables, nutrients, and metals with biological indicators. Sampling began approximately one year after the collapse and therefore does not capture the acute response to the initial tailings pulse. During the monitoring period, zooplankton assemblages showed no marked differences between upstream and downstream areas. Community structure was more strongly associated with hydrological seasonality and ongoing anthropogenic pressures, particularly nutrient enrichment and urban effluents. Turbidity, metals, and nutrients were important environmental correlates of richness, diversity, and density. Rotifers and copepods dominated, while the invasive Kellicottia bostoniensis persisted across sites and seasons. Tributaries supported higher densities and more exclusive species, potentially reflecting differences in nutrient availability, hydrodynamic conditions, and habitat retention. Overall, hydrological dynamics and contemporary anthropogenic stressors were more closely associated with community patterns than the upstream–downstream spatial gradient. Full article

Understanding hydrocarbon accumulation in deep and ultra-deep tectonically active basins demands an integrated evaluation of conventional and unconventional petroleum systems. The Kuqa Depression, a gas-prone foreland basin along the northern margin of the Tarim Basin, serves as an ideal case for investigating hydrocarbon enrichment mechanisms within a tectonically reworked Whole Petroleum System. Through burial and thermal history reconstruction, structural analysis, and petroleum-system evaluation, this study elucidates the evolution of hydrocarbon generation, redistribution, and retention. The results reveal that rapid Neogene-Quaternary burial accelerated the maturation of Triassic–Jurassic source rocks, triggering concentrated gas generation and widespread overpressure development. Successive foreland deformation has persistently modified reservoirs, migration pathways, and trap geometries, resulting in large-scale hydrocarbon redistribution via fault–fracture networks. Conventional and unconventional accumulations share common source kitchens, burial histories, pressure systems, and tectonic controls, but differ in hydrocarbon retention mechanisms. Conventional accumulations are dominated by migration processes, whereas unconventional accumulations are governed by retention processes. A generation–redistribution–retention framework is proposed to explain hydrocarbon enrichment within a tectonically reworked Whole Petroleum System. This framework provides a unified interpretation of conventional–unconventional hydrocarbon accumulation in the Kuqa Depression and offers insights for deep and ultra-deep petroleum exploration in tectonically active basins. Full article

Cooling-water intake basins in coastal power plants may experience particle retention and sediment deposition when complex inlet geometry produces large-scale recirculation and low-velocity zones near intake structures. This study examines the use of submerged barriers to mitigate particle retention in a de-identified coastal power-plant intake basin using hydraulic model experiments and hydraulic-model-supported three-dimensional computational fluid dynamics (CFD). A geometrically consistent model-scale configuration, including the inlet channel, main basin, three intake openings, and two outlet passages, was used to preserve site confidentiality while retaining the essential hydraulic mechanisms. Surface-flow patterns, water-depth variations, and sediment-deposition behavior were measured in the physical model and used to assess the numerical model. The numerical results, supported by the available hydraulic-model observations, reproduced the dominant counterclockwise recirculation and a broadly similar retention-prone region. The simulated water depths agreed closely with the measurements, with relative errors below 0.50% for the finest mesh. A water-depth-based grid-sensitivity assessment using 1,221,165; 2,414,216; and 3,378,840 computational cells further showed that the predicted mean water depths remained within 1.15% of the experimental measurements. The assessed numerical model was then applied to examine submerged-barrier configurations installed near the inlet-to-basin transition, with the barrier-performance interpretation limited to the tested mesh, the assumed representative particle condition, and the available qualitative flow/deposition evidence. Under this assumed particle-tracking condition, the original configuration retained 6989 particles at t = 200 s, whereas the 6 cm submerged barrier reduced the retained-particle count to 4956, corresponding to a reduction of approximately 29.1%. In contrast, the 15 cm emergent barrier increased the retained-particle count to 7573 because it blocked overtopping flow and induced new separated low-velocity regions. These results indicate that, among the tested configurations and under the assumed representative particle condition, the 6 cm submerged barrier yielded the lowest retained-particle count, whereas an excessively high barrier may deteriorate the internal flow structure and increase particle accumulation. Full article

Per- and polyfluoroalkyl substances (PFASs) are persistent, surface-active contaminants for which soil represents the largest terrestrial reservoir. This review synthesizes a rapidly expanding but fragmented body of literature in order to reframe PFAS not merely as a groundwater transport problem but as a systemic stressor of soil health, drawing together their reported effects on the chemical, physical and biological properties of soils and giving particular attention to the calcareous, alkaline, carbon-poor and seasonally dry soils of the Mediterranean. The reviewed evidence suggests that, chemically, PFASs perturb the coupled carbon and nitrogen cycles rather than the bulk soil reaction, transiently stimulating and then depressing organic carbon turnover, drawing down the dissolved organic carbon pool and disturbing nitrification, while their retention and bioavailability are governed chiefly by organic carbon, chain length and pH. Physically, the surfactant character that defines these molecules lowers the surface tension of soil water and concentrates PFASs at the air–water interface, so that in unsaturated and drought-prone soils much of the burden is retained and then released episodically, most clearly on rewetting after dry periods. Biologically, the literature consistently reports dose-dependent declines in microbial viability, diversity and enzyme activity, alongside toxicity to earthworms and other soil fauna, with sensitivity strongly modulated by soil texture and organic matter. Across all three domains, the Mediterranean emerges as both potentially vulnerable and conspicuously understudied, the available data being clustered in a few western countries and effectively absent for much of the eastern and southern basin, so that the regional assessment offered here rests largely on mechanistic inference rather than on direct observation. The review argues that these coupled mechanistic and geographic gaps define an urgent, region-specific research agenda for the protection of soil health. Full article

While low-impact development and retention strategies are widely studied in urban and agricultural contexts, a distinct knowledge gap remains regarding the quantitative evaluation of dispersed, natural microretention structures in small, ungauged, mountainous forested catchments under complex topographic conditions. To address this limitation, this study provides a novel quantitative assessment of how natural bioretention interventions—specifically arcuate deadwood log barriers, cascading reservoir systems, and strategic afforestation—influence runoff reduction and substrate infiltration dynamics. Focusing on the 4.57 km² basin of the Stankowice Stream in southwestern Poland, the research integrates field geodetic and hydrological measurements with Iszkowski’s empirical flow formulas and high-resolution digital elevation modeling (SCALGO platform). Delineation of 10 key subcatchments revealed that surface runoff potential is heavily concentrated within specific flow pathways rather than determined solely by subbasin area. In unit No. 9, deploying an arcuate arrangement of 19 deadwood logs achieved an 11% reduction in surface runoff (retaining 8662.50 m³), whereas coupling these log structures with a downstream cascading two-dam system significantly enhanced retention performance by establishing 79,065.68 m³ of depression storage and driving 264,066.16 m³ of subsurface infiltration. Furthermore, multi-scenario land use modeling demonstrated that transforming land cover to forest reduced surface runoff by over 70% in topographically steep subcatchments (e.g., unit No. 7). These findings demonstrate that effective flood mitigation in headwater catchments requires a systemic, targeted hybrid strategy combining decentralized bioretention with localized storage nodes, offering a transferable framework for sustainable regional water governance. Full article

The Shaximiao Formation in the Sichuan Basin hosts abundant tight oil resources; however, its reservoirs are typified by low porosity, low permeability, pronounced pore–throat structural heterogeneity, and highly complex microscopic crude oil seepage behavior. This study systematically investigates the microscopic flow mechanisms of crude oil in the Shaximiao Formation using a microfluidic experimental platform coupled with an integrated physical simulation system that enables real-time monitoring of dynamic imbibition throughout the fracturing–shut-in–flowback cycle. Experiments were conducted across three reservoir quality classes (Class I, II, and III), seven discrete shut-in durations (4, 8, 12, 24, 36, 42, and 54 h), and two representative fracturing fluid injection rates (12 and 20 m³/min). The results show that (1) residual-oil exhibits a distinct spatial distribution pattern: enrichment in large pores and large throats, with minimal retention in small pores and small throats; (2) moderate extension of shut-in duration significantly enhances movable oil saturation, whereas excessive shut-in time drives partial movable oil to transform into film flow or become trapped in dead-end pores, thereby exacerbating residual-oil retention; (3) the proportion of movable oil decreases gradiently with declining reservoir quality, following the order: Class I > Class II > Class III reservoirs; and (4) for the same reservoir type, a lower injection rate (12 m³/min) improves sweep efficiency in small pore–small throat regions and reduces residual oil retention, while a higher rate (20 m³/min) tends to induce an unbalanced seepage phenomenon, “preferential breakthrough in large pores and persistent retention in small pores”, which impairs the overall reservoir stimulation effect. Full article

Coastal litter accumulates along urban shorelines, yet the floating and stranded litter compartments of tourism-intensive coastal cities are rarely characterised side by side. We conducted monthly macro-litter surveys over one year (April 2023–March 2024) at two Dubrovnik sites less than 200 m apart, each representing a different litter compartment: Porat harbour, a semi-enclosed basin retaining floating litter, and Posat, an urban beach collecting stranded debris. Surveys followed the updated European MSFD marine litter monitoring guidance. In total, 1325 items were recorded at Porat and 1768 at Posat. The harbour was far more variable month to month (coefficient of variation 135% versus 77%), consistent with episodic basin retention. Artificial polymers dominated both compartments (84.9% at Porat; 79.2% at Posat), but the leading category differed: plastic fragments in the harbour and expanded polystyrene on the beach. Composition differed significantly between the two compartments (PERMANOVA, p = 0.038), though the separation was modest. Because each compartment requires a different sampling method, compartment and sampling method are fully confounded; absolute magnitudes are therefore reported separately and not compared. At Posat, where cleaning was suspended, the Clean Coast Index averaged 7.1 (moderate) but ranged from 1.5 to 21.9 between months, spanning all five cleanliness classes. These distinct signatures indicate that single-compartment monitoring may overlook urban coastal heterogeneity, and that mitigation requires compartment-specific measures. Full article

The East Qinling Mountains serve as a key national ecological security barrier and the core water source area of the Middle Route of the South-to-North Water Diversion Project in China, where vegetation restoration is a core measure for regional ecological conservation. However, existing studies have mostly focused on the individual hydrological characteristics of either the litter layer or soil layer, with limited understanding of their synergistic effects and the functional differences among typical restored vegetation types. In this study, we investigated the hydrological functions of the litter layer and 0~40 cm soil layer across seven vegetation restoration types (five forest stands, grassland and farmland control) in the upper Danjiang River Basin, southern foot of the East Qinling Mountains. Key hydrological indicators, including litter biomass, water-holding capacity, effective interception capacity, soil porosity, organic matter content, and water storage capacity, were measured and comprehensively evaluated. Furthermore, we explored the underlying mechanisms by which vegetation restoration enhances the hydrological functions of the litter layer and soil profile. The results showed that vegetation restoration in the East Qinling Mountains significantly altered the litter characteristics, with broad-leaved, coniferous and mixed forests exhibiting higher litter thickness and biomass than grassland and farmland. Litter water-holding capacity varied markedly across vegetation types: Pinus tabuliformis-Quercus variabilis mixed forest (Pt-Qvmf) and Quercus variabilis Blume (Qv) showed the highest 24 h water-holding rate, water-holding depth, and effective retention depth, while grassland had the lowest values. Litter water retention followed a logarithmic function with soaking time, and water absorption rate exhibited exponential decay, with the semi-decomposed layer showing stronger water retention performance. Vegetation restoration effectively improved the soil bulk density, porosity, and water-holding capacity, with more pronounced amelioration in the topsoil layer, and significant differences were observed among vegetation types. Comprehensive evaluation via the entropy weight method revealed that Robinia pseudoacacia L. (Rp) and Pinus tabuliformis Carrière (Pt) had the optimal integrated hydrological functions of the litter-soil profile, while grassland and Platycladus orientalis (L.) Franco (Po) performed the poorest. Structural equation modeling further quantified the driving mechanisms: soil porosity was the dominant direct driver of soil hydrological function, while litter biomass exerted an indirect effect through a significant serial mediation pathway via root biomass, soil organic matter (SOM), and aggregate stability, with the model explaining 83% of the total variance in soil hydrological function. This study provides targeted theoretical support and practical guidance for vegetation restoration, optimal tree species configuration, and forest ecosystem management in the water source area of the South-to-North Water Diversion Project. Full article