Search Results (3,055)

The Black Sea is a semi-enclosed basin that has experienced significant environmental degradation driven by nutrient enrichment and pollution from insufficiently treated wastewater discharges. While previous reviews have focused primarily on ecological impacts and eutrophication dynamics, no bibliometric study has systematically examined the representation of wastewater treatment technologies within this literature. This review addresses that gap, providing the first bibliometric synthesis to jointly analyse environmental research trends and wastewater treatment technology development in the Black Sea basin. A total of 1002 peer-reviewed publications indexed in the Web of Science Core Collection between January 2000 and March 2026 were analysed using a Preferred Reporting Items for Systematic Reviews and Meta-Analyses-based framework to examine research trends, thematic clusters, and geographic distribution. A targeted subset of 101 publications directly addressing wastewater treatment technologies was extracted for detailed technological classification. The results reveal a clear increase in research output over the past two decades, with eutrophication, nutrient enrichment, and water-quality degradation as dominant themes. Geographic analysis shows that Türkiye (n = 383), Russia (n = 232), and Romania (n = 129) are the leading contributors, with riparian countries accounting for 83.8% of publications. However, only 101 of the 1002 publications (10.1%) directly address wastewater treatment technologies, with most studies focused on conventional WWTP infrastructure (75.2%) and biological nutrient removal (22.8%). Advanced treatment technologies and nature-based solutions each represent only 3.0% of the wastewater subset. These findings are consistent with a meaningful gap in the regional evidence base for technological approaches to reducing nutrient inputs to the Black Sea, though it should be noted that publication volume alone cannot fully characterise the state of technological development in the region, as it is also shaped by funding structures, disciplinary traditions, and indexing practices. Nevertheless, expanding research on innovative and sustainable wastewater treatment technologies could play an important role in improving wastewater management and supporting long-term ecosystem recovery. Full article

Lake eutrophication and water quality deterioration are increasingly jeopardizing both ecological integrity and human health. As a typical eutrophic shallow lake on plateaus, Yilong Lake currently faces the primary issue of excessive COD_Cr levels. Through systematic sampling and analysis, as well as static release of COD_Cr from sediment experiments, we have categorized the release process of COD_Cr and identified factors that are highly correlated with COD by using RDA and random forest analyses. The aim is to investigate the release patterns of COD_Cr in Yilong Lake, explore the primary factors influencing COD_Cr, and understand the causes of water quality pollution in the lake. The principal findings of this study are as follows: the static release of COD_Cr from sediment experiments was conducted to estimate the COD_Cr release flux from the sediments of Yilong Lake using Fick’s first law, and the release process was divided into three stages: initial release, intermediate adsorption, and late equilibrium. The RDA results indicate that SedpH and SedTP are positively correlated with both COD_Cr and COD_Mn; COD_Mn is statistically most closely related to SedAP; and COD_Cr exhibits the strongest synergy with SedpH. The random forest model output demonstrates that BOD₅ is the factor most highly correlated with COD_Cr, followed by SedAP. The results of the submerged plant humic degradation experiments show that the organic matter released during the humic degradation process of submerged plants has a significant impact on COD_Cr in water bodies, and that algal activity also affects COD_Cr. These findings provide a scientific basis for environmental protection and pollution control in Yilong Lake and similar lakes. Full article

Aquaculture has rapidly expanded, surpassing capture fisheries and playing a vital role in global food security. However, this growth raises environmental concerns, especially regarding nitrogen waste accumulation in recirculating aquaculture systems (RASs). Nitrogen compounds from uneaten feed and fish excreta, mainly ammonia (NH₃) and nitrite (NO₂⁻), lead to water pollution, eutrophication, and greenhouse gas emissions. This study describes the setup and the efficiency of a new photo-electrocatalytic (PEC) system in reducing nitrogen waste in a high-density RAS for rainbow trout (30 kg/m³). The PEC system, an evolution of a pure photocatalytic system, was integrated in the units of the RAS and tested for the first time in field conditions, combining photocatalysis and electrochemical oxidation to convert toxic nitrogen species (NH₃) into less harmful nitrogen forms (NO₃⁻ and N₂), aiming to mitigate both water and atmospheric pollution. Over a 4-week period, water nitrogen compounds, ammonia and greenhouse gases (carbon dioxide, nitrous oxide and methane) emitted by water were continuously monitored in two groups of three tanks (PEC vs. control). Each tank was equipped as an independent RAS unit. PEC treatment led to significantly lower NH₃ concentrations (0.96 ± 0.2 mg/L vs. 1.78 ± 0.2 mg/L, p < 0.01), lower NO₂⁻ levels and higher NO₃⁻ levels (61.77 ± 2.14 mg/L vs. 53.10 ± 2.14 mg/L, p < 0.01) in water, indicating efficient nitrogen oxidation. Gaseous emissions were also reduced: NH₃ (1.49 vs. 2.64 mg/m²/day, p < 0.05) and N₂O (1.44 vs. 2.88 mg/m²/day, p < 0.05). These results support PEC technology as a promising solution for improving nitrogen management in intensive aquaculture. Although challenges remain in optimizing energy use and scalability, PEC offers a valuable strategy for reducing environmental impact while sustaining productivity in the aquaculture industry. Full article

Phosphate concentrations in agricultural drainage water frequently exceed those observed in municipal wastewater and, when discharged directly into river systems, pose a significant risk to their ecological status and potential. Developing cost-effective and scalable solutions for phosphate interception at the source is therefore essential for achieving the water quality goals outlined in environmental sustainability frameworks. This study evaluated the phosphate removal capacity of calcium hydroxide-modified metakaolin-based reactive materials as a sustainable approach to limiting agricultural nutrient loads entering river ecosystems. Two synthesis methods were compared: a fusion method and a low-temperature method. The resulting materials—metakaolin (M), low-temperature synthesized metakaolin (MLT), and Ca(OH)₂-modified low-temperature metakaolin (CaMLT)—were characterized by X-ray diffraction (XRD), X-ray fluorescence (XRF), textural property analysis, and scanning electron microscopy (SEM). Phosphate removal performance was evaluated in batch experiments under varying reactive material dosages (2.5–10.0 g·L⁻¹), initial phosphate concentrations (1.0–7.0 mg·L⁻¹), and contact times (1–144 h). The CaMLT material achieved the highest phosphate removal efficiency of 56% at a phosphate concentration of 1.0 mg·L⁻¹, a dose of 10.0 g·L⁻¹, and a contact time of 144 h. At higher phosphate concentrations (3.0 and 7.0 mg·L⁻¹), removal efficiencies decreased to 23% and 21%, respectively, under the same experimental conditions. The results were benchmarked against data reported in the literature. The findings indicate that low-temperature synthesized metakaolin modified with calcium hydroxide demonstrates potential as a reactive material for phosphate capture in agricultural drainage systems, offering a promising pathway toward more sustainable water resource management and freshwater ecosystem protection. Full article

Large-scale fishing bans are increasingly implemented to restore aquatic ecosystems, yet their effects on lower trophic levels remain poorly understood. As one of the world’s largest estuarine systems, the Yangtze River Estuary has been subjected to a ten-year fishing ban since 2021, providing a unique opportunity to potentially examine the response of plankton community to reduced fishing pressure along a steep salinity–nutrient gradient. This study relies on one-off environmental and plankton field surveys conducted in autumn 2024 (a sampling instead of multi-year time-series monitoring), we applied redundancy analysis, Mantel tests, and threshold indicator taxa analysis to tentatively clarify the roles of nutrients and salinity in structuring post-ban plankton communities. Species richness may have increased substantially compared with pre-ban levels, but community evenness declined and the dominance of Skeletonema costatum could have intensified, revealing a possible non-equilibrium recovery pattern. Zooplankton density increased substantially, which may not be fully consistent with the expectation under a simple top-down release scenario. Threshold analysis showed that S. costatum exhibited bidirectional responses to dissolved inorganic nitrogen and phosphate, with its positive response thresholds matching ambient nutrient concentrations in the inner estuary; this discrepancy is only a plausible inference since we lack direct measurements of fish predation and zooplankton grazing rates to verify causal trophic interactions. Our findings suggest that bottom-up forces driven by persistent eutrophication remain the dominant control on plankton community structure three years after the ban. From a watershed management perspective, our observational results provide a tentative implication that substantial reductions in nutrient loading might be required to mitigate unbalanced plankton community recovery; otherwise, the structural integrity of plankton assemblages could lag far behind the recovery of species richness under the current eutrophic background. Full article

Marine chlorophyll-a (Chl-a) concentration is a key proxy for phytoplankton biomass and an important indicator for eutrophication assessment, ecological monitoring, and harmful algal bloom early warning. Accurate forecasting of Chl-a concentration therefore has substantial scientific and practical value for marine environmental management. Nevertheless, existing deep models still have difficulty coupling relatively stable large-scale spatial structure with locally time-varying interactions, and many of them do not provide reliable uncertainty estimates, which limits their use in harmful algal bloom early warning and high-chlorophyll event assessment. To address these issues, this study proposes an uncertainty-quantified dynamic graph ordinary differential equation network, termed UQDGODE, for marine Chl-a concentration forecasting. The model combines a multivariate diffusion graph convolutional branch for stable spatial diffusion modeling with a dynamic graph ordinary differential equation branch for continuously evolving local interactions. A gating mechanism fuses the two branches, and a multivariate probabilistic prediction module outputs predictive means and covariance information for uncertainty quantification. Experiments on the Bohai Sea and South China Sea datasets show that the UQDGODE performs better in both point forecasting accuracy and probabilistic forecasting quality and produces more informative predictive distributions and more adaptive prediction intervals for marine ecological alerting. Full article

Shallow lakes are vulnerable to multiple anthropogenic stressors. However, the spatial responses of benthic ecosystems to these composite disturbances and the underlying mechanisms driving them remain poorly understood. Nansi Lake is a strategic water-regulating reservoir of the Eastern Route of the South-to-North Water Transfers. It has long been subjected to multiple human activities, and its aquatic ecological environment exhibits pronounced spatial heterogeneity. A systematic assessment is thus needed to evaluate the spatial distribution patterns of surface-sediment diatom communities and their trophic response characteristics. This study integrates the Trophic Diatom Index (TDI) with multivariate statistical approaches. It analyzes the spatial distribution and driving factors of surface-sediment diatom assemblages based on diatom and water quality data from 62 sampling sites. The results reveal three distinct community zones across the lake. The first is a high-disturbance zone dominated by hydraulic regulation and mining activities. In this zone, Stephanodiscus parvus Stoermer & Håkansson is the absolute dominant species, indicating a clear eutrophic status. The second is a hydrochemically stable zone dominated by Achnanthidium minutissimum (Kützing) Czarnecki, exhibiting relatively high community integrity. The third is a vast central open-water zone characterized by the dominance of Pseudostaurosira brevistriata (Grunow) Williams & Round, representing a mesotrophic transitional state. Partial redundancy analysis (pRDA) shows that multiple explanatory variables jointly explain 28.91% of the community variation. The independent explanatory powers of anthropogenic variables (9.12%) and environmental factors (7.94%) are both higher than that of pure spatial dispersal processes (0.35%). Redundancy Analysis (RDA) indicates that different types of human activities—such as reservoir regulation, coal mining, and estuarine inflows—may influence the spatial distribution patterns of surface-sediment diatoms. They do so by jointly driving variations in lake trophic status and the ionic environment, particularly Mg²⁺ and SO₄²⁻. This study provides a scientific basis for the water resource management of shallow lakes subject to anthropogenic impacts. Full article

The planned Lubiatowo–Kopalino nuclear power plant (NPP) on the Polish Baltic coast requires a cooling technology that balances energy security, economic efficiency, and compliance with a multi-layered framework governing thermal discharge in a sensitive sea. This article integrates regulatory analysis across four instruments (EU Water Framework Directive, Polish discharge standards, HELCOM Baltic guidelines, and IAEA practice) with site-specific evidence from a 2D advection-diffusion thermal plume model. Four cooling options (once-through seawater, closed-loop towers, dry-air, and hybrid) are evaluated against regulatory criteria and against the documented vulnerabilities of the southern Baltic: eutrophication, restricted flushing, and ongoing warming. The modelling indicates that the acute thermal plume (ΔT ≥ 2 °C) remains limited to approximately 1.18 km² even under summer 90th-percentile conditions, whereas low-magnitude warming (ΔT = 0.1–0.5 °C) extends over approximately 1886.6 km². Although the once-through system with a multi-port diffuser satisfies current regulatory criteria, the extensive far-field anomaly represents an additional ecological stressor for an already eutrophic and warming marine ecosystem. A staged hybrid approach, with the first unit on validated once-through cooling and subsequent units on hybrid dry/wet systems, emerges as the most sustainable pathway, balancing empirical learning, regulatory foresight, and long-term climate resilience. The analysis offers a transferable framework for thermal-discharge assessment in shallow, microtidal, nutrient-enriched coastal seas, while demonstrating consistency with established regulatory practice and published knowledge on thermal-plume behaviour. Full article

The accurate determination of chlorophyll a (Chl a) is often limited by the instability of conventional fluorescence height algorithms in algal bloom waters characterized by diverse phytoplankton morphology and red-shifted reflectance peaks. In this study, we propose the Normalized Dynamic Fluorescence Height (NDFH) as a novel hyperspectral algorithm for assessing sun-induced chlorophyll fluorescence. Using in situ bio-optical data and multi-source satellite observations (Advanced Hyperspectral Imager (AHSI) onboard ZY-1E, Hyperspectral Imager for the Coastal Ocean (HICO) onboard ISS, and Ocean Color Instrument (OCI) onboard PACE), NDFH was evaluated and compared with existing algorithms, such as the normalized Fluorescence Line Height, Cyanobacterial Index (CI), and Maximum Algal Line Height (MALH). The results show that NDFH has robust exponential correlations with Chl a concentrations in inland waters and can reliably detect fluorescence peak band shifts in bloom-dominated environments. Case studies in Lake Taihu confirm that NDFH is more effective at delineating bloom extent and Chl a distributions than conventional methods, particularly in algae-dominated waters. These findings show the potential of NDFH for operational monitoring of eutrophication and harmful algal blooms across diverse aquatic environments. Full article

High-frequency monitoring provides a practical approach for detecting short-term oxygen instability and pre-transition stress accumulation in eutrophic shallow lakes. In this study, dissolved oxygen (DO), pH, water temperature, and electrical conductivity (EC) were monitored at 5 min intervals in a restored shallow urban lake in Wuhan, China. A total of 112,896 synchronized observations from 392 complete daily profiles were analyzed to characterize diel physicochemical dynamics, identify a site-specific DO threshold, and evaluate process-based early-warning indicators. DO and pH showed pronounced synchronized diel oscillations; whereas, temperature mainly reflected seasonal background variation and EC showed weaker diel regularity. Correlation analysis and PCA indicated that DO and pH represented the dominant metabolic gradient, with DO serving as the most responsive indicator of oxygen instability. Piecewise logistic regression identified a site-specific DO threshold of 3.62 mg L⁻¹ associated with persistent hypoxia-related oxygen-stress states. During the August 2021 transition period, low-oxygen duration increased rapidly, oxygen-stress exposure intensified, and daytime recovery rate declined, indicating progressive oxygen-stress accumulation and weakened recovery capacity. These results show that high-frequency DO dynamics can provide early-warning information on persistent hypoxia-related oxygen stress, although the identified threshold should be interpreted as site-specific rather than universal. Full article

HVAC air filtration systems can be designed as either disposable or reusable units, with each approach involving different material, operational, and end-of-life requirements. However, the environmental performance of reusable HVAC filtration systems remains insufficiently characterized. This study conducted a cradle-to-grave Life Cycle Assessment (LCA) comparing reusable and disposable HVAC air filters under equivalent service conditions using the TRACI 2.1 impact assessment method in accordance with ISO 14040 and ISO 14044 standards. The analysis compared one reusable Delta M filter with eight equivalent disposable filters over the same filtration service period. Initial single-cycle comparisons showed that the reusable filter exhibited higher impacts due to increased structural material requirements associated with durable design. However, repeated refurbishment and reuse substantially reduced overall life cycle environmental burdens. At the defined functional unit, the reusable filtration system reduced global warming potential by approximately 69% (6.20 vs. 20.27 kg CO₂ eq) while also reducing ozone depletion, smog formation, acidification, eutrophication, respiratory effects, ecotoxicity, fossil fuel depletion, and non-carcinogenic impacts relative to the disposable filtration system. Environmental break-even analysis indicated that the reusable system began outperforming the disposable alternative after approximately two operational filtration cycles, while end-of-life material recovery further improved environmental performance beyond the baseline landfill scenario. Contribution analysis identified PVC frame production, polyester filtration media manufacturing, and galvanized steel mesh production as the dominant environmental hotspots. The results demonstrate that combining durable product design, repeated reuse, and end-of-life material recovery can substantially improve the long-term environmental performance of commercial HVAC filtration systems while supporting circular economy and sustainable building objectives. Full article

The increasing stresses imposed on forests by climatic changes require agile and adaptive management, in which tree breeding plays a crucial role. Assessment of G×E interactions has been highlighted as an explicit source of information for targeted breeding for resilience and productivity via better coupling of the demands of genotypes and locally anticipated climatic changes. Commonly, the genetic effects are evaluated for morphometric traits, which are a cumulative representation of the past conditions. In this study, the variability of increment and its relation to weather fluctuations were addressed as a climate-sensitive functional trait. Parallel Scots pine (Pinus sylvestris) progeny trials representing hemiboreal conditions and a local productivity (edaphic) gradient in Lithuania were studied to evaluate G×E effects on increment, combining tree-ring analysis and quantitative genetics. Scots pine progenies showed low environmental sensitivity of radial increment, which, however, showed complex region-specific relationships with winter temperature and summer moisture regimes. Negligible genetic controls were estimated for the weather sensitivity of increment, yet the genetic controls manifested in response to the co-occurrence of meteorological extremes. The genetic control over increment showed nonlinear relationships with site productivity, being strongest under oligotrophic and eutrophic rather than extremely poor or mesotrophic site conditions. Site productivity showed marginal effects on climatic controls over heritability estimates, indicating weak environmental interactions. Hence, the observed relationships suggest some limited potential for targeted pine breeding based on local populations. Full article

Phytoplankton communities are highly sensitive to environmental change and serve as key indicators of lake ecosystem health. In this study, four typical lakes in the middle Yangtze River (Xiandao, Bao’an, Wanghu, and Cihu Lake) were investigated through field monitoring to reveal the spatiotemporal patterns of phytoplankton communities and their driving environmental factors. Significant seasonal variation and spatial heterogeneity were observed. Although species composition varied, Chlorophyta, Cyanobacteria, and Bacillariophyta were dominant in all lakes. In the eutrophic Bao’an, Cihu, and Wanghu lakes, Cyanobacteria dominated the annual average abundances. Based on Reynolds’ functional group (FG) classification, 27 groups were identified. Dominant FG had seasonal successions. Canonical Correspondence and redundancy analyses indicated that water transparency, suspended solids, phosphate, and water temperature were the key environmental factors driving phytoplankton community succession. This study elucidated the response patterns of phytoplankton communities in lakes with varying nutrient levels to seasonal changes as well as the mechanisms underlying shifts in their growth strategies, thereby providing a theoretical framework for the ecological restoration of eutrophic lakes. Full article

Iberian reservoirs are highly vulnerable to droughts, warming temperatures, and agricultural runoff, which accelerate eutrophication. Monitoring these dynamics is crucial for sustainable management. This study investigated long-term trends in chlorophyll-a (Chl-a) and water transparency Secchi depth and developed empirical models for the Alto Rabagão (Rb) and Aguieira (Ag) reservoirs in Portugal. We used Sentinel-2 Level-2A reflectance data coupled with 153 in situ observations (2014–2024) for model calibration (n = 95) and validation (n = 58). Temporal trends were assessed using linear regression and Mann–Kendall analyses. Empirical models based on spectral indices (TBDO1, TBDO, MCI, NDWI) were evaluated using walk-forward time-series cross-validation. Results revealed a significant Chl-a increase (0.38 µg L⁻¹ year⁻¹; p = 0.016) and a simultaneous decline in transparency (p < 0.001) in Rb, indicating progressive eutrophication. In contrast, no significant trends were detected in Ag. Reservoir-specific models achieved moderate-to-high predictive performance, particularly for Chl-a (R² up to 0.75; cross-validated R² = 0.67–0.68, RMSE = 1.1 µg L⁻¹, MAE = 0.82 µg L⁻¹). Models using combined datasets showed lower accuracy, highlighting the importance of site-specific calibration. Wilcoxon signed-rank tests confirmed the absence of systematic bias between observed and predicted values. Ultimately, Sentinel-2 imagery combined with time-series cross-validation provides a reliable and cost-effective framework for the long-term monitoring of inland water quality. Full article

Planktothrix species are among the most widespread bloom-forming cyanobacteria in freshwater ecosystems and are of particular concern because of their ability to produce cyanotoxins and form persistent harmful algal blooms (HABs). Among them, Planktothrix agardhii and Planktothrix rubescens are the most extensively studied species and are responsible for a large proportion of bloom events reported in European lakes. This review synthesizes current knowledge on the taxonomy, ecophysiology, toxin production, environmental drivers, species interactions, and management of Planktothrix blooms, with a particular focus on European freshwater ecosystems. The available evidence highlights marked ecological differences between the two dominant species. P. agardhii is primarily associated with shallow, eutrophic, and well-mixed lakes, whereas P. rubescens is typically found in deep, stratified, and relatively transparent water bodies, where it forms persistent metalimnetic populations. These contrasting ecological strategies influence bloom development, toxin dynamics, detection, and management. Nutrient availability, light climate, temperature, water column stability, and biological interactions all contribute to bloom establishment and persistence, while climate change is expected to further modify bloom frequency, duration, and geographic distribution. The review also examines current monitoring and mitigation approaches, highlighting the limitations of conventional surface-based surveys for detecting deep P. rubescens populations and emphasizing the need for integrated monitoring strategies combining depth-resolved sampling, molecular tools, and toxin analyses. Overall, understanding the ecological and physiological diversity of Planktothrix species is essential for improving risk assessment, developing effective management measures, and mitigating the impacts of cyanobacterial blooms in European freshwaters. Full article