Search Results (1,651)

Urban rivers face increasing degradation from wastewater, runoff, and land-use change, yet multi-season tropical estuarine datasets remain scarce. This study compared physicochemical water quality, metals, and salinity dynamics over one year in the Juan Díaz and Pacora rivers, two contrastingly urbanized Panama Bay watersheds. Juan Díaz showed higher nutrient concentrations, lower dissolved oxygen, and greater variability than Pacora. Dissolved oxygen in Juan Díaz fell below 5 mg/L in five of nine campaigns and ammonia nitrogen exceeded 3.7 mg/L in all three dry-season campaigns, versus two of seven campaigns below 5 mg/L in Pacora. Total dissolved solids exceeded 500 mg/L in four of nine Juan Díaz campaigns, all in the wet season, but stayed compliant in Pacora. Total nitrogen and total phosphorus were up to 10-fold and seven-fold higher, respectively, in Juan Díaz during the dry season. Cu exceeded its USEPA criterion in two of three detections; Cd was detected once, in Juan Díaz, below its saltwater criterion (0.0079 mg/L). Salinity confirmed stronger tidal influence in Juan Díaz (up to 24.7 g/kg) than Pacora (0.03–2.74 g/kg). PCA separated the two rivers along a nutrient–oxygen gradient explaining 53.6% of variance. Overall, Juan Díaz shows greater degradation, while Pacora remains less contaminated but requires continued monitoring amid rapid urbanization. Full article

This study investigates the spatiotemporal distribution of heavy metals in urban soils of Thessaloniki, Greece, over a four-year monitoring period (2021–2024). A total of 664 soil samples were collected across diverse land-use types during both wet (winter) and dry (summer) seasons. Soil physicochemical properties were analyzed alongside cadmium (Cd), copper (Cu), lead (Pb), and zinc (Zn) concentrations. The results reveal distinct, element-specific accumulation dynamics driven by continuous anthropogenic inputs. Statistical and geospatial analyses confirm that Cd exhibits a highly significant, progressive accumulation and spatial expansion toward residential areas. In contrast, Cu and Pb demonstrate a gradual, chronic enrichment, eventually reaching a saturation point where winter precipitation is insufficient to offset summer deposition. Zn presents as a severe but temporally stable contamination burden, anchored to the northwestern industrial–port sector. Furthermore, the alkaline properties of the local urban soils were found to act as an effective sink, immobilizing contaminants and preventing downward leaching. The Geo-accumulation Index (I_geo) confirms a progressive decline in soil quality driven primarily by cadmium, while the other trace elements exhibit persistent, stable profiles. Overall, this study establishes a vital geochemical baseline of total heavy metal loading in Mediterranean urban soils, emphasizing the need for targeted emission controls and future mobile-fraction assessments to guide sustainable urban management. Full article

Extreme climate events, particularly precipitation extremes, pose significant risks to ecosystems, infrastructure, and socio-economic systems globally. In Peru, the diversity of its climate, driven by its complex topography, makes it highly vulnerable to such events, especially in the Andes and Amazon regions. This study evaluates the performance of 25 CMIP6 GCMs in simulating extreme precipitation events during both the wet and dry seasons at the national level. Gridded precipitation data from the PISCO product and CMIP6 model simulations for the period 1981–2014 were used to estimate extreme precipitation indices, including Rx1day, Rx5day, SDII, CDD, CWD, R10mm, and PRCPTOT. Performance was assessed using statistical metrics such as PBIAS, NRMSE, and the Pattern Correlation Coefficient (PCC), integrated through a TOPSIS ranking. Results indicate that NorESM2-MM, MPI-ESM1-2-LR, and CESM2 exhibit the best performance, achieving TOPSIS scores above 0.8. These models show high spatial correlation (PCC frequently >0.8) and relatively low biases. In contrast, models like FGOALS-g3 and CanESM5 show significant limitations, with PBIAS exceeding 80% in Rx1day and Rx5day and TOPSIS scores below 0.5. The ensemble reveals a persistent ‘drizzle bias,’ with wet day frequency (R1mm) generally overestimated by 20–40% in the wet season and by 40–80% during the dry season across most CMIP6 models. Furthermore, indices of temporal persistence (CWD and CDD) remain the most challenging, with CWD overestimations often exceeding 100–200%. These findings highlight the critical need for statistical or dynamical downscaling, together with bias correction, before using CMIP6 projections for local adaptation strategies in the Andes and Amazon regions. Full article

Seasonal hydrological variation can reorganize fluorescent dissolved organic matter (FDOM) in floodplain lakes; yet, its expression in Poyang Lake remains uncertain. We assessed campaign differences in FDOM composition by comparing 32 excitation–emission matrices from 16 fixed sites sampled during the dry and wet periods of 2024 using parallel factor analysis (PARAFAC), fluorescence indices, paired tests with Benjamini–Hochberg correction, and principal component analysis. Rank 4 fitted better and resolved two humic-like and two protein-like regions, although incomplete validation limited component-specific interpretation. In the wet period, C2 and combined humic-like maximum fluorescence intensity (Fmax) decreased (q = 0.00836), whereas bulk total organic carbon (TOC) and total Fmax did not differ. Mean protein-like contribution rose from 25.0% to 37.5% (q = 0.00322); the biological index increased, the humification index decreased, and the fluorescence index was unchanged. The first two principal components explained 78.11% of the variance, and an exact paired multivariate test detected an overall period difference (p = 3.05 × 10⁻⁵). No component–environment correlation survived correction or differed between periods. FDOM composition therefore underwent a campaign-specific reorganization without a corresponding change in bulk carbon, but the two-campaign design and incomplete validation preclude causal or source-specific inference. Full article

Odorants present a persistent challenge in drinking water treatment due to their low odor threshold concentrations (OTCs) and their resistance to conventional processes. This study investigated the seasonal occurrence of eight odorants across 20 surface water sources in Shandong, China. It evaluated their degradation using UV photolysis and four UV-based advanced oxidation processes (UV-AOPs): UV/H₂O₂, UV/PMS, UV/Cl, and UV/TiO₂. Total odorant concentrations ranged from 8 to 496 ng L⁻¹ in the wet season and from 5 to 184 ng L⁻¹ in the dry season, with 2-MIB as the dominant compound (detection frequency: 95%; contributions: 58.48% and 48.88%, respectively). Pearson correlation analysis revealed a seasonal shift in environmental drivers: total phosphorus (TP) and dissolved oxygen (DO) in the wet season versus NH₃-N and COD_Mn in the dry season. Across all five processes, degradation efficiency followed a consistent, structure-dependent hierarchy, ranking as CTA >> 2,4,6-TCA ≈ IPMP > IPO > 2-MIB ≈ GSM, with CTA achieving 74.66–95.03% removal while 2-MIB and GSM remained largely refractory (≤29.70%). Process-specific selectivity was also observed: UV/H₂O₂ was most effective for IPO, IPMP, and GSM; UV/PMS excelled for CTA and 2,4,6-TCA; and UV/Cl showed a slight advantage for 2-MIB. These findings provide mechanistic insights into structure-dependent odorant oxidation and suggest that UV-AOP performance may vary according to target-compound characteristics. Further validation in real water matrices is required before practical application. Full article

This study investigates the spatiotemporal dynamics of Land Use/Land Cover (LULC) along precipitation gradients across Türkiye by integrating high-resolution satellite-based precipitation datasets (CHIRPS, TerraClimate, and TRMM) with the European Space Agency (ESA) WorldCover (10 m) product and multi-sensor Normalized Difference Vegetation Index (NDVI) composites (Landsat, MODIS, Sentinel-2). Türkiye’s heterogeneous climate, characterized by a sharp contrast between humid coastal belts and semi-arid interiors, serves as a natural laboratory to assess ecosystem responses to moisture availability. The results reveal a systematic and non-linear transformation of LULC classes as precipitation increases. In low-rainfall zones (200–400 mm), agricultural activities and bare surfaces predominate, reflecting human-induced land management in water-constrained environments. A critical ecological threshold was identified between 400 mm and 700 mm, where grassland areas expand rapidly, becoming the dominant class. Beyond the 900 mm isohyet, forest cover exhibits a sharp increase, approaching nearly 100% dominance in regions exceeding 1200 mm, effectively displacing other LULC categories. Comparative analysis of precipitation products shows that while all datasets capture the “coastal-wet/inland-dry” pattern, TRMM tends to overestimate winter precipitation (exceeding 100 mm), whereas CHIRPS and TerraClimate provide more conservative estimates (75–80 mm). Overlay analyses between seasonal NDVI and precipitation confirm a pronounced “time-lag effect” in vegetation phenology. Despite peak precipitation occurring in winter (~75 mm), NDVI reaches its minimum (~0.03) due to thermal limitations and dormancy. Conversely, vegetation greenness peaks during the dry summer months (NDVI ~0.14 to 0.40), utilizing antecedent soil moisture stored during the spring recharge. High-resolution Sentinel-2 data proved superior in delineating micro-topographic vegetation responses compared to Landsat and MODIS. These findings provide a scientific baseline for sustainable land management and climate adaptation strategies, highlighting that precipitation thresholds are the primary determinants of Türkiye’s ecological boundaries. Full article

Climate change is increasing drought frequency and severity in Central Europe, with consequences for the productivity and stability of mixed broadleaf forests. We analyzed annual radial growth of European beech (Fagus sylvatica L.) and sessile oak (Quercus petraea (Matt.) Liebl.) along a water-availability gradient on the Swabian Alb (southwestern Germany). At three nearby sites, 45 trees per species were sampled. Tree-ring chronologies were related to meteorological variables and integrated drought indices (PDSI/scPDSI, SMI). Extreme dry and wet years were identified from detrended growing-season indices, and event responses were quantified using resistance, recovery, and resilience metrics and their humid-year analogues. Annual growth variation was primarily site-driven rather than species-driven, highlighting strong control by local soil water availability. Correlation analyses showed that integrated drought and soil-moisture indices explained radial growth more consistently than single climate variables. Oak showed higher drought resistance than beech in several events, although the magnitude and significance of this difference depended on site and drought year. Resistance generally declined toward recent events, particularly at Site 2, while recovery tended to increase. Recovery did not consistently favor either species, and resilience remained broadly stable, except for a decline in beech during the most recent drought events. Overall, sensitivity to drought is jointly controlled by species identity and fine-scale site conditions: oak has a comparatively robust resistance advantage, whereas post-drought recovery and resilience are strongly context-dependent. These findings support site-specific species mixtures and silvicultural strategies to sustain forest function under increasing drought risk. Full article

Ribbed Smoked Sheet (RSS) rubber production in southern Thailand relies extensively on rubber-wood combustion, potentially generating substantial emissions of fine particulate matter and polycyclic aromatic hydrocarbons (PAHs). Despite the economic importance of this sector, systematic characterization of biomass-derived PAHs under tropical monsoonal and coastal conditions remains limited. This study investigates the particle size distribution, concentration levels, seasonal variability, and atmospheric dynamics of PAHs associated with RSS production in Chumphon Province, Thailand. Size-segregated particulate matter was collected using an eight-stage Andersen cascade impactor at two contrasting sites during a seven-month monitoring period from March to September 2025, covering the transition from the late dry/summer season to the rainy season in southern Thailand. Fifteen priority PAHs were quantified by high-performance liquid chromatography with fluorescence detection. Results indicate that emissions from rubber-wood combustion inside smokehouses exhibit a unimodal distribution dominated by submicron particles (MMAD = 0.85 µm; GSD = 2.71). Ambient aerosols displayed a bimodal structure, with an accumulation-mode peak (~0.6 µm) associated with combustion processes and a coarse-mode peak (~4 µm) linked to mechanical and marine aerosol sources. Particle-bound PAHs were predominantly associated with fine particles (~0.59 µm), although seasonal hygroscopic growth under high humidity shifted modal diameters toward ~1.8 µm during the rainy season. PAH profiles were dominated by 3–4 ring compounds characteristic of biomass combustion. Total PAH concentrations exhibited a strong positive correlation with monthly RSS production, while precipitation demonstrated an exponential scavenging effect. Monsoonal circulation and sea spray aerosol (SSA) interactions were identified as key regulators of gas–particle partitioning, transport pathways, and removal efficiency. The findings reveal that the coastal atmosphere of southern Thailand functions as a dynamic multiphase system in which emission intensity, hygroscopic particle growth, monsoonal transport, and wet deposition collectively govern PAH behavior. This study provides the first integrated assessment linking rubber-sheet production dynamics to size-resolved PAH distributions under tropical coastal conditions and offers a scientific foundation for emission mitigation strategies in biomass-dependent agro-industrial regions. Full article

The Huaibei region is a critical grain and energy–chemical base in northern China, characterized by substantial water demand for industrial and agricultural production. Karst groundwater systems constitute the primary water supply source in this area. Under the superimposed impacts of intensive exploitation, climate change, and anthropogenic activities, karst aquifers have encountered a series of geo-environmental problems, including groundwater level decline and expansion of cones of depression. Most previous studies have predominantly focused on water quality assessment and groundwater resource quantification, yet systematic investigations into the multi-scale characteristics and driving mechanisms of karst groundwater level dynamics remain insufficient. In this study, based on long-term groundwater level and rainfall monitoring data (2014–2024) from three monitoring wells representing different types of karst aquifers, continuous wavelet transform (CWT) and wavelet coherence (WTC) approaches are introduced to identify the periodic patterns of karst groundwater levels and reveal the dominant controlling factors of groundwater level dynamics. The results demonstrate that groundwater levels in all types of karst aquifers exhibit distinct multi-scale periodic variations. The groundwater levels of HB01 and HB02 share dominant oscillation periods of 18~19 months and 9 months with regional rainfall, while the groundwater level at HB03 displays a more complex, multi-scale, periodic combination of 41 months, 18~19 months, and 9 months. Periodic variations in regional rainfall serve as the dominant controlling factor for the intra-annual and inter-annual periodic fluctuations of karst water levels, with a prominent resonance relationship identified between the two variables at dominant periodic scales. Distinct heterogeneity is observed in the response magnitude and lag time of different karst aquifer types to rainfall; specifically, the lag time of water level response to rainfall on the annual periodic scale ranges from 2.7 to 2.9 months. The correlation between annual average water level and pumping discharge is moderate for boreholes HB01 and HB03, whereas a strong correlation is detected for borehole HB02, implying that its water level regime is likely subjected to pronounced pumping disturbance. The degree of karst development, aquifer burial depth, and overlying stratum architecture are the key geological factors accounting for such heterogeneous response patterns. For the first time, this study utilizes long-term water level time series data from the karst water exploitation zone of the Huaibei Plain, complemented by synchronous precipitation and pumping records. Integrated with regional hydrogeological settings, wavelet analysis is employed to conduct an in-depth investigation into the dynamic variations in karst water levels in the Huaibei region from the perspective of groundwater recharge–discharge relationships. The results provide a scientific underpinning for the remediation of karst water over-exploitation and the optimal allocation of water resources. Specifically, pumping and artificial recharge schemes can be proactively adjusted based on periodicity forecasts. Zoned management strategies for water resources are put forward: artificial regulation and storage are recommended for zones with sensitive hydrological responses, while preventive protection is prioritized for zones with sluggish responses. By incorporating periodic characteristics and lag durations, targeted pumping strategies for dry and wet seasons can be developed, and a coupled water level–rainfall–pumping early warning system can be established to realize the long-term sustainable regulation of karst water resources. Full article

Reducing external phosphorus (P) inputs is central to eutrophication control, but sediment P release can sustain internal loading and delay lake recovery. This study assessed sediment P composition, vertical distribution, and short-term release potential in Datong Lake, a shallow lake formerly affected by intensive aquaculture. Total phosphorus (TP), dissolved total phosphorus (DTP), and particulate phosphorus (PP) were measured in surface and overlying waters during the dry and wet seasons. Surface-sediment P fractions were characterized in both seasons, whereas dry-season sediments were used for adsorption and release tests, vertical profiling, and depth-specific incubations. Wet-season samples had higher TP, DTP, and PP concentrations in surface water and higher TP and PP concentrations in overlying water. Surface-sediment P was predominantly inorganic, with Ca-P as the largest inorganic fraction; bioavailable P accounted for about 32% of TP. In the 24-h batch tests, the adsorbed P amount exceeded the released amount. Total P and its NaOH-extractable and organic fractions were enriched in the upper sediment. Across the 1–5 to 21–25 cm intervals, 15-d cumulative P release decreased from 22.9 ± 1.9 to 7.2 ± 1.0 mg·kg⁻¹, and the initial 3-d release rate decreased from 1.13 ± 0.18 to 0.24 ± 0.07 mg·kg⁻¹·d⁻¹. Overall, Datong Lake sediments contained high P concentrations but exhibited limited short-term release, with the greatest release amount and rate occurring in the upper sediment. Full article

Ochroma lagopus is a fast-growing, low-density broadleaf tree species with increasing importance for tropical plantation forestry and lightweight bio-based materials. However, juvenile plantations may be sensitive to seasonal changes in water availability and soil nutrient status, particularly in tropical monsoon regions with strong drywet season transitions. In this study, two-year-old O. lagopus plantations in Xishuangbanna, Yunnan Province, China, were used to compare leaf anatomical structure, non-structural carbohydrate (NSC) components in leaves and roots, and C:N:P stoichiometric characteristics between the wet and dry seasons. Correlations among leaf structure, carbon allocation, and nutrient stoichiometry were also analyzed. The results showed significant seasonal differences in leaf anatomical structure. Leaves in the wet season had more developed vascular bundles and midrib tissues, whereas leaves in the dry season had deeper substomatal chambers and higher tissue looseness. NSC components were mainly affected by organ differentiation, whereas seasonal effects were weak. Roots maintained relatively high and stable carbohydrate levels. C:N:P stoichiometric characteristics were affected by both season and organ, and root P concentration and P-related ratios were more sensitive to seasonal transition. Leaf and root N/P ratios were generally below 14, indicating a nutritional status associated with relative N limitation. Correlation analysis showed that leaf anatomical traits were significantly correlated with leaf NSC, C, N, and P concentrations and stoichiometric ratios, revealing a coordinated structural carbon nutrient response of O. lagopus during the dry wet season transition. These findings suggest that the response of juvenile O. lagopus plantations to seasonal environmental variation is not driven by water availability alone, but is jointly regulated by leaf structural plasticity, root carbon pool stability, nutrient leaching during the wet season, and P availability in red soil. This study provides a theoretical basis for the introduction and cultivation, nutritional diagnosis, and seasonal management of juvenile O. lagopus plantations in tropical regions. Full article

Assessing nitrate sensitivity to hydroclimatic variability is important for evaluating water-quality vulnerability under hydroclimatic variations in coupled surface-water and groundwater systems. This study applies a hybrid, scenario-based projection framework combining a Long Short-Term Memory (LSTM) model and Weighted Regression on Time, Discharge, and Season with Projections (WRTDS-P) to examine nitrate plus nitrite responses under idealized wet and dry conditions across seven U.S. river basins and three associated groundwater wells. LSTM projections evaluate conditional sensitivity to altered precipitation forcing, while WRTDS-P projections assess discharge-conditioned responses based on empirically derived concentration–discharge relationships. Results show strong basin-scale heterogeneity in nitrate sensitivity. Agriculturally dominated Midwestern and central U.S. basins generally exhibit higher nitrate concentrations under the idealized wet scenarios, whereas basins influenced by groundwater buffering, flow regulation, or managed hydrology show weak or slightly negative wet–dry responses. For the three evaluated wells, groundwater projections show site-specific damped or delayed responses relative to nearby surface-water systems, reflecting aquifer storage and legacy nitrogen effects, although the Illinois well shows a larger projected wet–dry amplitude than the associated river. Cross-framework comparison reveals moderate agreement in response direction but notable differences in magnitude, highlighting sensitivity to model structure and forcing assumptions. These findings emphasize the value of hybrid projection frameworks for cross-framework sensitivity analysis and for interpreting nitrate vulnerability under hydroclimatic variation while accounting for uncertainty across surface-water and groundwater systems. Full article

Morocco, located at the southern margin of the Mediterranean climate-change hotspot, is exposed to a rapidly evolving precipitation regime whose national-scale characterization remains incomplete. This study delivers an integrated assessment of the spatio-temporal variability and trends of precipitation and its extremes over the country during the most recent World Meteorological Organization (WMO) climate-normal period (1991–2020), based on daily observations from 31 synoptic stations operated by the Direction Générale de la Météorologie (DGM). Trends in annual, seasonal and monthly precipitation were quantified using the non-parametric Mann–Kendall test combined with Sen’s slope estimator, while the structural transformation of the rainfall regime was characterized through three indices recommended by the Expert Team on Climate Change Detection and Indices (ETCCDI): the Consecutive Dry Days (CDDs), the Simple Daily Intensity Index (SDII) and the amount of precipitation from very wet days (R95pTOT). The results reveal an apparent tendency toward a negative trend, with a predominance of negative precipitation trends in winter and early spring, most pronounced in February, that reach statistical significance at only a limited number of stations, partly offset by a spatially coherent wetting in November over central and eastern Morocco. The joint analysis of the three ETCCDI indices indicates a north–south contrasted reorganization: northern stations exhibit longer dry spells coexisting with intensified extreme rainfall, whereas southern stations show a generalized weakening of both intensity and extremes. These findings point to a structural shift toward more episodic and contrasted precipitation regimes, with the wet season starting later, ending earlier and concentrating rainfall into fewer but more intense events. The analysis provides an updated observational baseline for the validation of CMIP6 based regional projections and for the design of climate-resilient water and agricultural strategies in Morocco. 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

Field measurements undertaken in six paired primary school classrooms in Anambra State, Nigeria, previously demonstrated that interlocking compressed earth block (ICEB) classrooms maintained significantly lower occupied-hour temperatures than adjacent sandcrete block (SCB) classrooms. This study applies DesignBuilder/EnergyPlus simulation, evaluated against field measurements, to investigate the physical mechanisms underlying this observed thermal advantage and to explore seasonal performance beyond the period accessible through field monitoring. Simulation models were developed using literature-derived thermophysical properties and validated against field measurements collected at Awkuzu Primary School on 2 July 2024. Model accuracy was assessed using ASHRAE Guideline 14 metrics. The ICEB model achieved NMBE of −6.4% and CV(RMSE) of 6.8%, satisfying both recommended thresholds. The SCB model achieved CV(RMSE) of 15.6%, while NMBE of −14.0% marginally exceeded the recommended threshold because of conservative TMYx boundary conditions. Results indicate that the superior wet-season performance of ICEB classrooms is attributable to the interaction between high thermal mass (μ = 0.31; φ = 9.1 h) and continuous cross-ventilation. Parametric crossover simulations demonstrated that ventilation was the dominant cooling mechanism, while ICEB wall thermal mass provided an additional independent thermal benefit of approximately 0.31 °C. This material contribution is secondary in magnitude to the ventilation effect and is not presented as a standalone practical advantage. Dry-season simulations suggested a possible reversal of performance under near-calm harmattan conditions; however, the magnitude and direction of this effect remain uncertain because of EPW boundary-condition limitations. The findings suggest that classroom thermal performance depends on the interaction between envelope thermal mass and ventilation configuration rather than material properties alone and highlight the potential importance of controllable ventilation in naturally ventilated educational buildings in tropical climates. Full article