Search Results (479)

Rapid urbanization has fostered the proliferation of urban villages (UVs), high-density informal settlements that pose unique challenges for environmental management. Despite their prevalence, the dynamics of pollutant accumulation in these transitional neighborhoods remain underexplored. This study investigated nitrogen and phosphorus accumulation in road-deposited sediment (RDS) within Shenzhen, a representative megacity in southern China, utilizing field sampling and statistical analysis to identify dominant drivers. The results indicate that UVs function as significant pollution hotspots, with RDS accumulation rates approximately 3.7 times higher than in formal built-up areas. Analysis revealed that pollution intensity is primarily driven by natural factors such as slope, whereas pollution load is controlled by anthropogenic supply factors. This creates a critical input–output imbalance where high pollutant inputs exceed the natural removal capacity. Consequently, effective mitigation of urban non-point source pollution requires shifting from traditional engineering solutions to spatially sensitive planning strategies, offering practical guidance for enhancing urban sustainability in rapidly urbanizing regions. Full article

The Atacama Desert in northern Chile is characterized by its naturally high metal concentrations; however, human activities have significantly increased their availability and concentration in aquatic environments. In the Loa River basin, copper mining is the main economic activity, and the extremely arid conditions contribute to high levels of evaporation and salinity. This study evaluated the concentrations of As, Cd, and Cu in the 63 µm sediment fraction from three areas, Lequena, La Finca, and Quillagua, during the years 2014, 2015, 2017, and 2023. Contamination levels were assessed using multiple approaches, including the Geoaccumulation Index (Igeo), the Enrichment Factor (EF), the Pollution Load Index (PLI), and the mean Probable Effect Concentration Ratio (m-PEC-Q). The results showed that Lequena (upper river zone) had no evidence of anthropogenic contamination over time; however, the ecological risk assessment highlighted the significant natural contribution of arsenic, representing a potential risk to the ecosystem. In contrast, La Finca (mid-river zone) and Quillagua (river mouth) showed significantly high levels of contamination. The Geoaccumulation Index consistently classified these sites as “moderately” to “heavily” contaminated or “heavily contaminated” for arsenic, while the Enrichment Factor indicated “very high enrichment” for arsenic, reflecting a strong anthropogenic influence. Ecological risk assessments indicated a persistent 76% probability of toxicity at La Finca throughout all sampling years, a level also observed at Quillagua in 2017 and 2023, with concentrations frequently exceeding international sediment quality guidelines. These patterns are attributed to the proximity of mining activities in the middle zone and the downstream transport of contaminated sediments to the river’s mouth, resulting in persistently high ecological risks over time. This study provides important baseline information for pollution control and ecological safety in the Loa River basin. Full article

Long-term particulate matter (PM) chemical composition measurements were performed in Cyprus at two different sites (an urban/traffic site (“LIMTRA”) and a remote/background site (“AGM”)) in an effort to assess (i) the spatial and temporal variability of fine (PM2.5) particulate matter in the eastern Mediterranean; (ii) the main sources contributing to their levels and their relationship with the characteristics of the sampling location; and (iii) the enhancement effect of local anthropogenic and natural biogenic sources on PM levels. To this end, the simultaneous determination of 118 individual Secondary Organic Aerosol (SOA) components (carboxylic acids, organosulfates, and organonitrates) was performed. The “AGM” station showed average SOA yields more than three times higher than those at the “LIMTRA” station (15 ng∙m⁻³ and 4.4 ng∙m⁻³, respectively), whilst the organonitrate levels were higher at “LIMTRA” than at “AGM” (3.3 ng∙m⁻³ and 1.8 ng∙m⁻³, respectively). The most abundant SOA species were hydroxy-acetone sulfate, glycolic acid sulfate, and lactic acid sulfate (21 ng∙m⁻³ at “LIMTRA” and 84 ng∙m⁻³ at “AGM”). The highest SOA load was observed in spring at “AGM” (18 ng∙m⁻³) and in summer at “LIMTRA” (6.8 ng∙m⁻³). Two statistical factorization tools, Principal Component Analysis and Positive Matrix Factorization, were applied to extract common patterns and point to possible SOA sources and SOA formation pathways; the different categorization approaches produced similar results. Full article

With rapid socioeconomic development and intensified human activities, nitrogen (N) loads have continued to rise, exerting significant impacts on the environment. Most existing studies focus on single cities or short time periods, which limits their ability to capture nitrogen dynamics under rapid urbanization. Based on statistical data from multiple cities in Zhejiang Province from 2011 to 2021, this study applied nitrogen balance accounting and statistical analysis to systematically evaluate the spatiotemporal variations in nitrogen inputs, outputs, and surpluses, as well as their driving factors. The results indicate that although nitrogen inputs and outputs fluctuated over the past decade, the overall nitrogen surplus showed an increasing trend, with the nitrogen surplus per unit area rising from 49.89 kg/(ha·a) in 2011 to 62.59 kg/(ha·a) in 2021. Zhejiang’s nitrogen load was higher than the national average but remained below the levels of highly urbanized regions such as the Yangtze River Delta and Pearl River Delta. Accelerated urbanization and increasing anthropogenic pressures were identified as major contributors to the rising nitrogen surplus, with significant inter-city disparities. Cities like Hangzhou, Ningbo, Wenzhou, and Jinhua were found to face higher risks of nitrogen pollution. Redundancy analysis and Pearson correlation analysis revealed that nitrogen surplus was positively correlated with cropland area, livestock population, total population, precipitation, GDP, and industrial output, further highlighting the dominant role of human activities in nitrogen cycling. This study provides the long-term quantitative assessment of nitrogen balance under multi-city coupling at the provincial scale and identifies key influencing factors. These findings provide scientific support for integrated nitrogen management across multiple environmental compartments in Zhejiang Province, including surface water, groundwater, agricultural systems, and urban wastewater, under conditions of rapid urbanization. Full article

Soil contamination by potentially toxic elements (PTEs) is a growing environmental concern, particularly in agricultural regions where soil quality directly affects crop safety and human health. This study evaluates PTE concentrations and ecological risks in agricultural soils of Hautat Sudair, central Saudi Arabia, using contamination indices, multivariate statistics, and GIS-based spatial modeling supported by RS-derived land use/land cover (LULC) mapping. The results show that the mean concentrations of Ni (35.97 mg/kg) and Mn (1230 mg/kg) exceed international thresholds in several locations, while Pb (8.34 mg/kg), Cr (33.00 mg/kg), Zn (60.09 mg/kg), and As (4.25 mg/kg) remain within permissible limits in most samples. Contamination indices, including the Enrichment Factor (EF), Contamination Factor (CF), and Geo-Accumulation Index (Igeo), highlight hotspot behavior, with isolated sites showing elevated concentrations approaching screening levels (e.g., Pb up to 32.0 mg/kg and Cr up to 52.0 mg/kg), whereas Ni and Mn exhibit the most pronounced local enrichment. The Pollution Load Index (PLI) varies from 0.24 to 0.80, indicating low to moderate contamination levels, while the Risk Index (RI) ranges from 10.43 to 41.38, signifying low ecological risk. Multivariate statistical analyses, including correlation matrices and principal component analysis (PCA), reveal that Ni, Cr, and Mn share a common source, possibly linked to anthropogenic inputs and natural geological background. Kaiser–Meyer–Olkin (KMO) and Bartlett’s test confirm the adequacy of the dataset for PCA (KMO = 0.797; χ² = 563.845, p < 0.001). Spatial distribution maps generated using GIS and RS highlight contamination hotspots, reinforcing the necessity for periodic monitoring. By integrating indices, multivariate patterns, and spatial context, this study provides a replicable, research-driven framework for interpreting PTE controls in arid agricultural soils. Full article

An integrated field–analytical framework was applied to quantify the impact of two small-settlement treatment facilities (TF1 and TF2) on the Irtysh River (East Kazakhstan). The main objective of this study is to quantify effluent-driven dilution and non-conservative changes in key water-quality indicators downstream of TF1 and TF2 and to evaluate parsimonious models for predicting effluent-outlet BOD and COD from upstream measurements. Paired upstream–downstream control sections are sampled in 2024–2025 for 22 indicators, and plant influent–effluent records are compiled for key wastewater variables. Chloride-based conservative mixing indicated very strong dilution (approximately $D\approx 2.0\times {10}^3$ for TF1 and $D\approx 4.2\times {10}^2$ for TF2). Deviations from the mixing line were summarized using a transformation diagnostic $\theta$. At TF1, several constituents exceeded mixing expectations ($\theta \approx 13$ for COD, $\theta \approx 42$ for ammonium, and $\theta \approx 6$ for phosphates), while nitrate shows net attenuation $\theta <0$. At TF2, $\theta$ values cluster near unity, indicating modest deviations. Under a small-sample regime $\left(\mathrm{N}=10\right)$ and leave-one-out validation, regularized regression provided accurate forecasts of effluent-outlet BOD and COD. Lasso under LOOCV performed best (BOD_after: RMSE = 0.626, MAE = 0.459, and $R^2=0.976$; COD_after: RMSE = 0.795, MAE = 0.634, and $R^2=0.997$). The results reconcile strong reach-scale dilution with constituent-specific local departures and support targeted modernization and operational forecasting for water-quality management in small facilities. Full article

As a sink for microplastics (MPs) in the aquatic environment, sediments have garnered considerable attention. However, the occurrence characteristics of MPs in sediments of different water seasons are not clear, especially for reservoir sediment cores. This study aimed to elucidate the occurrence, spatial and vertical distribution, fragmentation and pollution risk of MPs in the sediment cores of the Xiangxi River, Three Gorges Reservoir (TGR) during different seasons. In sediment cores, the average abundance of MPs was 8.57 × 10³ ± 5.65 × 10³ items/kg DW in the wet season (WS) and 7.98 × 10³ ± 4.00 × 10³ items/kg DW in the dry season (DS), respectively. The abundance of MPs in surface sediments and sediment cores exhibited spatial heterogeneity, reflecting seasonally contrasting hydrodynamic conditions between sites S1 and S3. However, the abundance of MPs in the river estuary was the highest, both in surface sediments and sediment cores. Interestingly, the occurrence characteristics of MPs in surface sediments indicated that in addition to anthropogenic activity, hydrological conditions of the river can also have an impact on the spatial distribution of MP abundance in surface sediments. Polypropylene (PP), polyethylene (PE), polystyrene (PS), and polyethylene-propylene copolymer (EPM) were identified as the dominant polymer types (57–99%), with small-sized microplastics (SMPs, 0–300 μm) being the most prevalent. Water seasons influenced the size distribution of MPs in surface sediments. Using a conditional fragmentation model, MP sources were inferred by comparing fragmentation parameters (λ and α) in sediments with those reported for atmospheric deposition, reservoir water, and water-level fluctuation zone soils. Furthermore, the pollution load index (PLI) exceeded 1, indicating MP accumulation in the sediments. The pollution risk index (PRI) values indicated a considerable (300 < PRI < 1000) pollution risk in two water seasons, primarily due to the presence of polyvinyl chloride (PVC). This study enhances the understanding of MP behavior and associated environmental risks in reservoir sediments, offering valuable insights for future research and pollution mitigation efforts. Full article

The Veracruz Reef System National Park (VRSNP), located in the central Gulf of Mexico, is one of the country’s most ecologically and economically significant coral systems. Despite its high biodiversity and ecosystem functionality, it is affected by anthropogenic inputs such as fluvial discharges, urban effluents, and port and tourism activities that contribute organic and bacteriological loads. This study aimed to identify the presence of Enterococcus spp. and Vibrio spp. during three climatic seasons—dry, rainy, and north winds—at two water column depths (surface and bottom) across three reefs (Enmedio, Chopas, and Gallega) within the VRSNP during the 2022 annual cycle. Samples were analyzed according to national and international standards. Results showed that Vibrio spp. were influenced mainly by temporal factors, with higher values during north winds and the dry season (>1100 MPN/100 mL); otherwise, rainy conditions reported the lowest load (184.89 ± 15.00 MPN/100 mL). While Enterococcus spp. exhibited greater spatial influence, particularly in surface waters, Enmedio Reef recorded the highest load (478.34 ± 37.28 CFU/100 mL); in addition, Chopas Reef reported the lowest at the bottom (12.43 ± 1.26 CFU/100 mL). The findings highlight the need to strengthen microbiological monitoring protocols in marine coastal ecosystems to assess water quality, public health risks, and the ecological integrity of coral reef environments, as well as the implementation of molecular identification techniques. Full article

The lake systems of the Qinghai–Tibet Plateau, while serving as vital hubs for socioeconomic development, have become critical zones of heavy metal contamination, posing severe threats to the fragile “Third Pole” ecosystem and regional environmental security. This study investigated the concentration, distribution, sources, and ecological risks of eight heavy metals (As, Cd, Co, Cr, Cu, Ni, Pb, and Zn) in lake sediments and riparian soils of Bangong Co Lake, a remote alpine lake on the Qinghai–Tibet Plateau. Lake sediment and soil samples were collected and tested from various shoreline types, including natural and human-affected areas. The Pollution Load Index (PLI) was applied to assess contamination levels, and source apportionment was performed using principal component analysis (PCA) combined with the Absolute Principal Component Score–Multiple Linear Regression (APCS-MLR) receptor model. Results revealed that heavy metal concentrations were generally higher in soils than in sediments. Compared to regional background values, elevated levels of most heavy metals were observed in human-affected shores, while natural-type soils exhibited higher concentrations of Co, Cr, Ni, and As. In sediments, only Cd and As were notably elevated in human-affected areas. The PLI results indicated that most sampling sites were either uncontaminated or slightly contaminated, with higher pollution levels occurring primarily in human-affected shoreline zones. Source apportionment demonstrated that heavy metals in sediments were predominantly derived from natural sources such as rock weathering, with anthropogenic contributions being relatively limited. In contrast, soils exhibited significant anthropogenic influences, with industrial, transportation, and agricultural activities contributing substantially to Cu (53.27%), Pb (58.64%), Zn (57.98%), Cd (34.09%), and As (39.87%). The research underscores the differential impacts of human activities on heavy metal accumulation in sediments and soils of high-altitude lake systems. It offers valuable baseline data for monitoring and managing heavy metal pollution in ecologically sensitive alpine regions. Full article

The Clearwater River, located in western Washington, USA, is a free-flowing river with high precipitation rates impacted by spatially extensive logging throughout the 1900s. Declining salmon productivity within the watershed has been linked to the effects of legacy deforestation, including increased fine sediment loads, a lack of large wood and physical habitat complexity, and potential channel incision coupled with side channel and floodplain disconnection. To test a conceptual model positing that the river’s geomorphic diversity was declining, potentially due to anthropogenic incision, we employed a dual approach, combining historical geomorphic mapping and current-condition hydraulic modeling using SRH-2D. A dual approach allows us to identify mainstem river reaches with the greatest potential for floodplain and side channel reconnection by utilizing increased roughness as a proxy for large wood effects on the river stage. Based on our geomorphic mapping, the area occupied by the mainstem river and surrounding geomorphic units has remained relatively stable through time. However, there was a marked decrease in the side channel connections within the downstream-most 30 river kilometers, confirmed through the hydraulic modeling results. Between river kilometers 10 and 20, river stages at 2-year recurrence interval peak discharge are located over 2 m below young Holocene terraces and could indicate a recent anthropogenic incision contributing to side channel disconnection. A decrease in unvegetated alluvium through time also indicates that there could be less dynamic lateral channel movement and overbank inundation between 1980 and 2017, despite a similar history of high peak flows. Overall, even though the river is able to balance the loss of the active geomorphic unit area with the incorporation of new geomorphic units through lateral channel changes, this area is likely concentrated in a smaller number of individual channels and floodplains, specifically in the lower 30 river kilometers. This study provides a framework for a site-screening-level analysis in impacted watersheds, using a watershed impacted by legacy logging without flow regulation, where the impacts are often less pronounced than in dammed river systems. Full article

Hulun Lake, the largest freshwater lake in the Eurasian steppe, is a critically climate-sensitive water body facing severe ecological threats. This systematic review synthesizes multidisciplinary evidence from 1961 to 2025 to examine the characteristics and drivers of its water environment and quality evolution. The findings reveal that the primary driver of the lake’s hydrological degradation shifted from natural climate variability to anthropogenic land-use change around 1998. While ecological water diversion has partially alleviated water scarcity, it also introduces a significant external nutrient load, creating a paradox where increased water volume coincides with aggravated eutrophication. Furthermore, overgrazing in the catchment not only enhances conventional runoff pollution but also facilitates a unique “tumbleweed-mediated cross-media pollution” pathway. This review concludes that the restoration of Hulun Lake necessitates a shift from singular water quantity regulation to an integrated management strategy that concurrently addresses water quantity, quality, and aquatic ecosystem health. The insights gained are crucial for informing the sustainable management of Hulun Lake and other inland lakes in cold, arid regions under global change. Full article

The European wildcat (Felis silvestris) is a mesocarnivore widely distributed across Europe, with populations in the Iberian Peninsula experiencing decline due to habitat fragmentation, hybridization with domestic cats, and anthropogenic factors. Among the parasites commonly found in wildcats are cestodes of the genus Hydatigera, which includes cryptic species within the Hydatigera taeniaeformis complex. This study aimed to identify Hydatigera species within this complex infecting wildcats in central Spain using both morphological and molecular methods. A total of 26 road-killed wildcats were collected between 2021 and 2023 from Castilla and León and Castilla-La Mancha. Cestodes were recovered from 73% of individuals, yielding a total of 240 Hydatigera specimens. Molecular analysis of the mitochondrial cox1 gene and a newly developed multiplex PCR targeting cox1, cytb and nad4 genes enabled differentiation between Hydatigera kamiyai and European Hydatigera sp., confirming their presence in definitive hosts in Spain for the first time. Mixed infections were detected in 60% of infected wildcats. The high prevalence and parasite load observed highlight the role of rodents in the transmission cycle. This study expands the known distribution of the H. taeniaeformis complex species in Europe and provides a reliable molecular tool for their identification, essential for further epidemiological investigations. Full article

The safety, conservation, and efficient management of existing road bridges have assumed a key role in recent years due to the strategic importance of these structures for local territories and their exposure to natural and anthropogenic risks. Many assets are in a state of degradation due to adverse environmental conditions, unforeseen loads in the design phase, and lack of maintenance, with often dramatic consequences. In response to these critical issues, integrated approaches based on the exploitation of different digital technologies are emerging to support inspection, monitoring, and maintenance activities. This paper proposes a digital workflow for bridge inspection management, based on the integration of information modeling, online databases, and automated data exchange and updating. The designed workflow enables the creation of a dynamic information model that evolves with the time-dependent data collected during periodic inspections by means of a Visual Programming Language. The data, stored in an online database, are filtered, analyzed, and dynamically associated with model elements, ensuring consistency, traceability, and reduction in manual input errors. The workflow was validated through a field application to an existing bridge, demonstrating its effectiveness in automating information management and providing the basis for the development of an interoperable and scalable platform for the digital management of infrastructure assets. Full article

This study investigated the physicochemical properties and nutrient dynamics on the Romanian shelf of the northwestern Black Sea in July 2024, collecting data across 36 stations (13–1116 m depth) heavily influenced by Danube discharges. Vertical CTD profiling revealed a pronounced seasonal thermocline and a deep-lying permanent halocline. The Cold Intermediate Layer (CIL) boundary, defined by the 8 °C isotherm, was absent, indicating warmer subsurface waters. Surface nutrient concentrations, particularly for nitrate (NO₃) and phosphate (PO₄), were considerably lower than peak eutrophication periods, approaching pre-1970s values, suggesting a positive trend due to reduced anthropogenic loading. They are also comparable to or lower than other coastal regions in the Black Sea. Vertical nutrient profiles confirmed the typical anoxic Black Sea structure, but with regional specifics: the PO₄ maximum was slightly deeper, and the NO₃ maximum position and concentration mirrored the pre-eutrophication period, further supporting reduced anthropogenic nitrogen input. Silicate (SiO₄) concentrations were consistently low throughout the water column, suggesting the northwest shelf functions as a SiO₄ sink compared to the southeastern Black Sea. Overall results indicate a shift towards a less eutrophic state on the Romanian shelf while highlighting the continued dominance of Danube-driven hydrodynamics. In addition to those investigations, this study assessed nutrient preservation techniques, finding that pasteurization was significantly superior to freezing for maintaining the stability of PO₄ and NOx (losses up to 20% and 47% for frozen samples, respectively) over six months. Though SiO₄ was stable under both methods, the freezing produced lower concentrations, possibly from incomplete depolymerization during thawing. These findings stress that pasteurization could be taken into consideration as a reliable preservation technique for long-term storage of nutrient samples. Full article

Most risk assessment and source apportionment studies of the heavy metals in the surface soils in China have focused primarily on East China, whereas studies focused on Northwest China, particularly regarding heavy metals in surface soils in the central and western areas, remain limited. In this study, surface soils in the central–western Ali region were investigated, and the concentrations of nine heavy metals were determined. Moreover, the distribution patterns and ecological risks of these heavy metals were elucidated via a combination of the geoaccumulation index, pollution load index ($PLI$), comprehensive potential ecological risk index ($RI$), and integrated X-ray diffraction (XRD)–multivariate statistical techniques. Additionally, the pollution characteristics and sources were analyzed. The results indicated the following: (1) The spatial distribution of heavy metal pollution is closely linked to the geological background, and high–pollution zones (e.g., Cr, Ni, Co, Cu, As, and Cd) conform well with the distributions of ultramafic rocks and iron/chromite ore beds. The geoaccumulation index revealed that Cd caused slight and moderate contamination at 29.1% and 5.5% of the sites, respectively, whereas As affected 14.6% of the sites. The pollution load index indicated moderate pollution in 20% of the sites, and the potential ecological risk index indicated that 41.8% of the sites posed moderate risks, which was largely driven by Cd (mean $E_r^i$ = 43.1). The comprehensive ecological risk index ($RI$ = 115) confirmed a moderate risk level overall. Principal component analysis revealed three primary sources: natural weathering (Cr–Ni–Co–Cu, 39.1%); a mixed source influenced by nonagricultural anthropogenic activities such as transport and regional deposition, combined with natural processes such as arid climate and alkaline soil conditions that influence Cd mobility (Cd–Mo–Pb, 20.8%); and industrial/mining activities (As–Sb, 14.2%). Mineralogical analyses further indicated that heavy metals are present via lattice substitution, adsorption, and precipitation. This study systematically clarifies the composite pollution pattern and sources of heavy metals in the alpine Ali region, supporting targeted contamination control. Full article