Water

26 pages, 3706 KB

Open AccessArticle

Enhanced Biosorption of Triarylmethane Dyes by Immobilized Trametes versicolor and Pleurotus ostreatus: Optimization, Kinetics, and Reusability

by Ruchi Upadhyay, Wioletta Przystaś, Roman Turczyn and Marcelina Jureczko

Water 2025, 17(17), 2600; https://doi.org/10.3390/w17172600 - 2 Sep 2025

Abstract

The discharge of synthetic dyes from industries poses severe environmental challenges, necessitating eco-friendly remediation strategies. This study investigated the biosorption of triarylmethane dyes Crystal Violet (CV), and Brilliant Green (BG) using self-immobilized and sponge-immobilized biosorbents of Trametes versicolor (strain CB8, CB8/S2) and Pleurotus [...] Read more.

The discharge of synthetic dyes from industries poses severe environmental challenges, necessitating eco-friendly remediation strategies. This study investigated the biosorption of triarylmethane dyes Crystal Violet (CV), and Brilliant Green (BG) using self-immobilized and sponge-immobilized biosorbents of Trametes versicolor (strain CB8, CB8/S2) and Pleurotus ostreatus (strain BWPH, BWPH/S2). Tests were conducted with live and autoclaved biomass under varying conditions of dye concentration (100–400 mg/L), temperature (15–55 °C), and pH (2–10). Sponge-immobilized live biomass (CB8/S2 and BWPH/S2) showed superior performance, removing up to 90.3% and 81.7% of BG and 43.9% and 39.3% of CV, respectively, within 6 h, demonstrating 3–5 times higher efficiency than self-immobilized biomass for both dyes. Maximum sorption of 379.4 mg/g of BG and 48.9 mg/g of CV was achieved by CB8/S2 at 400 mg/L. Principal Component Analysis biplot confirmed immobilization efficacy, where Dim1 (85.9–91.8% variance) dominated dye concentration and contact time. The optimized conditions for BG removal by CB8/S2 was 20.85–32.17 °C and pH 3.4–6, and for CV, at pH 6.5–7.5 and 30 °C. The percentage of dye sorption data fitted well with the quadratic model (p < 0.05). Fourier transform infrared spectroscopy (FT-IR) analysis indicated that hydrogen bonding and electrostatic interactions facilitated dye binding onto fungal mycelium. Notably, sponge-immobilized biosorbents were reusable without additional treatment. The findings support fungal biomass immobilization as a viable strategy to augment the bioremediation potential in treating dye-laden wastewater. Full article

(This article belongs to the Special Issue Biodegradation Strategies for Sustainable Removal of Persistent Pollutants and Xenobiotics in Wastewater Treatment)

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17 pages, 821 KB

Open AccessArticle

Refining Management Strategies for Common Squid (Todarodes pacificus) Fishing Vessel Fisheries in Korean Waters

by Sung-Su Lim and Bong-Kyu Jung

Water 2025, 17(17), 2599; https://doi.org/10.3390/w17172599 - 2 Sep 2025

Abstract

This study develops integrated bioeconomic management strategies for the common squid (Todarodes pacificus) fishery in Korea’s coastal waters, addressing both biological conservation and economic sustainability amid severe stock depletion and declining fishery profitability. Drawing on recent catch data and cost structures [...] Read more.

This study develops integrated bioeconomic management strategies for the common squid (Todarodes pacificus) fishery in Korea’s coastal waters, addressing both biological conservation and economic sustainability amid severe stock depletion and declining fishery profitability. Drawing on recent catch data and cost structures for six Total allowable Catch (TAC)-managed fishery types, common squid-specific economic indicators were estimated using a stepwise cost allocation method. Based on previous research using the Catch—Maximum Sustainable Yield (CMSY) model with limited Catch Per Unit Effort (CPUE) data, the biomass in 2020 was estimated at approximately 56% of Biomass at Maximum Sustainable Yield (BMSY), indicating an overfished state. Scenario-based simulations identified TAC allocation thresholds at which net profits reach zero, providing a benchmark for adaptive quota redistribution. Results show variation in economic sensitivity and common squid dependency among fishery types: common squid-dependent gears such as offshore jigging and East Sea trawl exhibit high vulnerability, while multi-species fisheries such as purse seine remain resilient. These results provide a basis for developing tailored management strategies for each fishery, thereby enhancing the effectiveness of interventions. Accordingly, policy recommendations include dynamic TAC adjustments, expanded monitoring, introduction of an Individual Transferable Quota system, and coordinated stock assessments with China and Japan. These findings contribute to refining Korea’s TAC system by aligning stock recovery goals with the economic viability of fishing operations. Full article

(This article belongs to the Special Issue Coastal Ecology and Fisheries Management)

20 pages, 4280 KB

Open AccessArticle

Application of Positive Mathematical Programming (PMP) in Sustainable Water Resource Management: A Case Study of Hetao Irrigation District, China

by Jingwei Yao, Julio Berbel, Zhiyuan Yang, Huiyong Wang and Javier Martínez-Dalmau

Water 2025, 17(17), 2598; https://doi.org/10.3390/w17172598 - 2 Sep 2025

Abstract

Water scarcity and soil salinization pose significant challenges to sustainable agricultural development in arid and semi-arid regions globally. This study applies Positive Mathematical Programming (PMP) to analyze agricultural water resource management in the Hetao Irrigation District (HID), China. The research constructs a comprehensive [...] Read more.

Water scarcity and soil salinization pose significant challenges to sustainable agricultural development in arid and semi-arid regions globally. This study applies Positive Mathematical Programming (PMP) to analyze agricultural water resource management in the Hetao Irrigation District (HID), China. The research constructs a comprehensive multi-stress-factor integrated PMP model to evaluate the compound impacts of water resource constraints, pricing policies, and environmental stress on agricultural production systems. The model incorporates crop-specific salinity tolerance thresholds and simulates farmer decision-making behaviors under various scenarios including water supply reduction (0–100%), water pricing increases (0.2–1.0 CNY/m³), and soil salinity stress (0–10 dS/m). The results reveal that the agricultural system exhibits significant vulnerability characteristics with critical thresholds concentrated in the 60–70% water resource utilization interval. Water pricing policies show limited effectiveness in low-price ranges, with wheat demonstrating the highest price sensitivity (−23.8% elasticity). Crop salinity tolerance analysis indicates that wheat–sunflower rotation systems maintain an 85% planting proportion even under extreme salinity conditions (10 dS/m), significantly outperforming individual crops. The study proposes a hierarchical water resource quota allocation system based on vulnerability thresholds and recommends promoting salt-tolerant rotation systems to enhance agricultural resilience. These findings provide scientific evidence for sustainable water resource management and agricultural adaptation strategies in water-stressed regions, contributing to both theoretical advancement of the PMP methodology and practical policy formulation for irrigation districts facing similar challenges. Full article

(This article belongs to the Special Issue Challenges and Innovations in Resilience of the Water-Energy-Food Nexus)

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25 pages, 3590 KB

Open AccessArticle

Spatio-Temporal Trends of Monthly and Annual Precipitation in Guanajuato, Mexico

by Jorge Luis Morales Martínez, Victor Manuel Ortega Chávez, Gilberto Carreño Aguilera, Tame González Cruz, Xitlali Virginia Delgado Galvan and Juan Manuel Navarro Céspedes

Water 2025, 17(17), 2597; https://doi.org/10.3390/w17172597 (registering DOI) - 2 Sep 2025

Abstract

This study examines the spatio-temporal evolution of precipitation in the State of Guanajuato, Mexico, from 1981 to 2016 by analyzing monthly series from 65 meteorological stations. A rigorous data quality protocol was implemented, selecting stations with more than 30 years of continuous data [...] Read more.

This study examines the spatio-temporal evolution of precipitation in the State of Guanajuato, Mexico, from 1981 to 2016 by analyzing monthly series from 65 meteorological stations. A rigorous data quality protocol was implemented, selecting stations with more than 30 years of continuous data and less than 10% missing values. Multiple Imputation by Chained Equations (MICE) with Predictive Mean Matching was applied to handle missing data, preserving the statistical properties of the time series as validated by Kolmogorov–Smirnov tests (

p = 1.000

for all stations). Homogeneity was assessed using Pettitt, SNHT, Buishand, and von Neumann tests, classifying 60 stations (93.8%) as useful, 3 (4.7%) as doubtful, and 2 (3.1%) as suspicious for monthly analysis. Breakpoints were predominantly clustered around periods of instrumental changes (2000–2003 and 2011–2014), underscoring the necessity of homogenization prior to trend analysis. The Trend-Free Pre-Whitening Mann–Kendall (TFPW-MK) test was applied to account for significant first-order autocorrelation (

ρ_{1} > 0.3

) present in all series. The analysis revealed no statistically significant monotonic trends in monthly precipitation at any of the 65 stations (

α = 0.05

). While 75.4% of the stations showed slight non-significant increasing tendencies (Kendall’s

τ

range: 0.0016 to 0.0520) and 24.6% showed non-significant decreasing tendencies (

τ

range: −0.0377 to −0.0008), Sen’s slope estimates were negligible (range: −0.0029 to 0.0111 mm/year) and statistically indistinguishable from zero. No discernible spatial patterns or correlation between trend magnitude and altitude (

ρ = - 0.022

,

p > 0.05

) were found, indicating region-wide precipitation stability during the study period. The integration of advanced imputation, multi-test homogenization, and robust trend detection provides a comprehensive framework for hydroclimatic analysis in semi-arid regions. These findings suggest that Guanajuato’s severe water crisis cannot be attributed to declining precipitation but rather to anthropogenic factors, primarily unsustainable groundwater extraction for agriculture. Full article

(This article belongs to the Special Issue Impacts of Climate Change on Water Resources: Assessment and Modeling, 2nd Edition)

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15 pages, 1110 KB

Open AccessArticle

Natural Radionuclides ²²²Rn and ²²⁶Ra in Shallow Groundwater of Nysa County (SW Poland): Concentrations, Background, and Radiological Risk

by Piotr Maciejewski and Jakub Ładziński

Water 2025, 17(17), 2596; https://doi.org/10.3390/w17172596 - 2 Sep 2025

Abstract

Natural radionuclides may occur in groundwater and pose health risks when present in elevated concentrations. This study evaluates the quality of shallow groundwater in Nysa County (SW Poland) based on the activity concentrations of natural radionuclides radon (²²²Rn) and radium ( [...] Read more.

Natural radionuclides may occur in groundwater and pose health risks when present in elevated concentrations. This study evaluates the quality of shallow groundwater in Nysa County (SW Poland) based on the activity concentrations of natural radionuclides radon (²²²Rn) and radium (²²⁶Ra) and estimates the associated radiological risk from water ingestion. Twenty-three groundwater samples were collected from private wells located within two distinct geological units: the Fore-Sudetic Block and the Opole Trough. Activity concentrations of ²²²Rn and ²²⁶Ra were measured using the liquid scintillation counting method. A spatial distribution model for ²²²Rn was developed using inverse distance weighting in QGIS. Local hydrogeochemical background levels were determined using the Q-Dixon test, interquartile range, and Shapiro–Wilk normality test. The background ranged from 2.6 to 3.9 Bq·L⁻¹ in the Opole Trough and from 0 to 10.7 Bq·L⁻¹ in the Fore-Sudetic Block. The lower detection limit (0.05 Bq·L⁻¹) for ²²⁶Ra activity concentration measurements was not exceeded. Effective dose rates were calculated in accordance with the recommendations of the International Commission on Radiological Protection and United Nations Scientific Committee on the Effects of Atomic Radiation. Doses ranged from <1 µSv to over 120 µSv·y⁻¹. Although all samples met national regulatory standards (≤1 mSv·y⁻¹), the World Health Organization reference level (0.1 mSv·y⁻¹) was exceeded in two cases. The results support the need for the radiological monitoring of unregulated private wells and provide a scientific basis for the refinement of legal frameworks and health protection strategies. Full article

(This article belongs to the Section Hydrogeology)

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15 pages, 6366 KB

Open AccessArticle

Archaeo-Hydraulic Investigations of the Ancient Water Supply System in the Lorestan Province

by Seyed Yaghoub Karimi, Safar Marofi, Carlo De Michele, Yadollah Heidari Babakamal, Amir Hamzeh Haghiabi and Kazem Shahverdi

Water 2025, 17(17), 2595; https://doi.org/10.3390/w17172595 - 2 Sep 2025

Abstract

Excavations in Iran’s Lorestan province uncovered a 200-year-old water system consisting of four earthenware jars connected by clay pipes, each jar built from six or seven pottery sections. Due to local conditions, the dimensions and spacing of the jars in this water supply [...] Read more.

Excavations in Iran’s Lorestan province uncovered a 200-year-old water system consisting of four earthenware jars connected by clay pipes, each jar built from six or seven pottery sections. Due to local conditions, the dimensions and spacing of the jars in this water supply system design deviate from the established standards in historical water science literature (a diameter-to-length ratio of less than 1:4). This deviation prompted detailed archaeo-hydraulic investigations, including fieldwork analyses and hydraulic calculations of the discovered water supply system. The system was designed to serve both public and governmental purposes. Structural modifications (diameter-to-length ratio < 1:4) improved durability and strength for regional conditions. The jars divided, ventilated, and filtered water from mud and sand. Comparative analyses suggest the water supply system dates to the late Zand and Qajar periods (18th–19th centuries). Full article

(This article belongs to the Section Hydraulics and Hydrodynamics)

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21 pages, 5876 KB

Open AccessArticle

Efficient Regulation and Prediction Model Construction for Water and Fertilizer Management Through Resource Utilization of Manure and Urea Co-Application

by Kaiqi Qi, Xiaofeng Tang, Jianhong Ma, Rui Zhao, Junan Bao, Pengshan Tang, Jiaqi Liu, Dandan Pei, Xiaohou Shao and Xinyu Mao

Water 2025, 17(17), 2594; https://doi.org/10.3390/w17172594 - 2 Sep 2025

Abstract

In intensive agriculture, the excessive application of chemical fertilizers leads to approximately 50% nitrogen loss, which exacerbates water pollution and the greenhouse effect. Meanwhile, nitrogen and phosphorus emissions from livestock manure have far exceeded those from chemical fertilizers, becoming the primary source of [...] Read more.

In intensive agriculture, the excessive application of chemical fertilizers leads to approximately 50% nitrogen loss, which exacerbates water pollution and the greenhouse effect. Meanwhile, nitrogen and phosphorus emissions from livestock manure have far exceeded those from chemical fertilizers, becoming the primary source of agricultural non-point-source pollution. This study aims to clarify the comprehensive effects of combining manure with urea application and precision irrigation on the soil environment, lettuce growth, and quality, and to determine the optimal water and fertilizer management strategy. The results indicate that combining manure with urea application and precision irrigation can effectively mitigate non-point-source pollution, enhance soil nutrients, promote lettuce growth, and improve quality. When the irrigation volume reaches 75–78% of field capacity and the ratio of manure to urea nitrogen ranges from 7:3 to 1:1, key indicators for soil health, lettuce growth, and quality can exceed 90% of their respective maximum levels. This study provides a scientific basis and practical guidance for the resource utilization of manure and precise water–fertilizer management in intensive lettuce production. Full article

(This article belongs to the Special Issue Water and Soil Pollution from Agriculture: Mechanisms, Assessments and Mitigation Strategies)

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32 pages, 8209 KB

Open AccessArticle

Hydraulic Response of Dam-Break Flood Waves to Converging Channel Geometries: A Numerical Investigation

by Amir Ghaderi, Hooman Shahini, Hossein Mohammadnezhad, Hossein Hamidifar and Jaan H. Pu

Water 2025, 17(17), 2593; https://doi.org/10.3390/w17172593 - 2 Sep 2025

Abstract

The topography of the flood path significantly influences the hydraulic characteristics of flood events, necessitating in-depth analysis to better understand the continuous dynamics during dam failure scenarios. These analyses are useful for the hydraulic evaluation of infrastructures downstream of a dam site. This [...] Read more.

The topography of the flood path significantly influences the hydraulic characteristics of flood events, necessitating in-depth analysis to better understand the continuous dynamics during dam failure scenarios. These analyses are useful for the hydraulic evaluation of infrastructures downstream of a dam site. This study examined the effects of four distinct converging configurations of guide-banks on the propagation of unsteady flow in a rectangular channel. The configurations studied included trapezoidal and crescent side contractions, as well as trapezoidal and crescent barriers located at the channel’s center, each with varying lengths and widths. Numerical simulations using computational fluid dynamics (CFD) simulation were validated against experimental data from the literature. The results reveal that the flow experienced a depth increase upon encountering converging geometries, leading to the formation of a hydraulic jump and the subsequent upstream progression of the resulting wave. The width of the obstacles and contractions had a marked influence on the flow profile. Increased channel contraction led to a more pronounced initial water elevation rise when the flood flow encountered the topography, resulting in a deeper reflected wave that propagated upstream at less time. The reflected wave increased the water elevations up to 0.64, 0.72, and 0.80 times the initial reservoir level (0.25 m), respectively, for cases with 33%, 50%, and 66% contraction ratios to the channel width (0.3 m). For the same cases at a certain time of t = 5.0 s, the reflected wave reached 1.1 m downstream, 0.5 m downstream, and 0.1 m upstream of the initial dam location. Waves generated by the trapezoidal configuration affected the upstream in less time than those formed by the crescent contraction. The length of the transitions or their placement (middle of/across the channel) did not significantly affect the flow profile upstream; however, within the converging zone, longer configurations resulted in a wider increased water elevation. Overall, the intensity of the hydraulic response can be related to one factor in all cases, namely, the convergence intensity of the flow lines as they entered the contractions. Full article

(This article belongs to the Special Issue Coastal Engineering and Fluid–Structure Interactions)

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21 pages, 5922 KB

Open AccessReview

Bibliometric Analysis of the Impact of Soil Erosion on Lake Water Environments in China

by Xingshuai Mei, Guangyu Yang, Mengqing Su, Tongde Chen, Haizhen Yang and Sen Wang

Water 2025, 17(17), 2592; https://doi.org/10.3390/w17172592 - 1 Sep 2025

Abstract

With the increasing attention to China’s ecological environment protection and the prominence of lake water environment problems, the impact of soil erosion on lake ecosystems has become an important research topic for regional sustainable development. Based on the CiteSpace bibliometric method, this study [...] Read more.

With the increasing attention to China’s ecological environment protection and the prominence of lake water environment problems, the impact of soil erosion on lake ecosystems has become an important research topic for regional sustainable development. Based on the CiteSpace bibliometric method, this study systematically analyzed 225 research articles on the impact of soil erosion on the water environment of lakes in China in the core collection of Web of Science from 1998 to 2025, aiming to reveal the research hotspots, evolution trends and regional differences in this field. The results show that China occupies a dominant position in this field (209 papers), and the Chinese Academy of Sciences is the core research institution (93 papers). The research hotspots show obvious policy-driven characteristics, which are divided into slow start periods (1998–2007), accelerated growth periods (2008–2015), explosive growth periods (2016–2020) and stable development periods (2021–2025). A keyword cluster analysis identified nine main research directions, including sedimentation effect (#0 cluster), soil loss (#2 cluster) and nitrogen and phosphorus migration (#11 cluster) in the Three Gorges Reservoir area. The study found that the synergistic effects of climate change and human activities (such as land use change) are becoming a new research paradigm, and the Yangtze River Basin, the Loess Plateau and the Yunnan–Guizhou Plateau constitute the three core research areas (accounting for 72.3% of the total literature). Future research should focus on a multi-scale coupling mechanism, a climate resilience assessment and an ecological engineering effectiveness verification to support the precise implementation of lake protection policies in China. This study provides a scientific basis for the comprehensive management of the soil erosion–lake water environment system, and also contributes a Chinese perspective to the sustainable development goals (SDG6 and SDG15) of similar regions in the world. Full article

(This article belongs to the Special Issue Soil Erosion and Soil and Water Conservation, 2nd Edition)

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3 pages, 121 KB

Open AccessEditorial

Advances in Agricultural Irrigation Management and Technology

by Xingye Zhu

Water 2025, 17(17), 2591; https://doi.org/10.3390/w17172591 - 1 Sep 2025

Abstract

Agriculture is the cornerstone of global food security, yet water scarcity and inefficient irrigation practices pose significant challenges to sustainable production [...] Full article

(This article belongs to the Special Issue Advances in Agricultural Irrigation Management and Technology)

22 pages, 4626 KB

Open AccessReview

Biochar for Mitigating Nitrate Leaching in Agricultural Soils: Mechanisms, Challenges, and Future Directions

by Lan Luo, Jie Li, Zihan Xing, Tao Jing, Xinrui Wang and Guilong Zhang

Water 2025, 17(17), 2590; https://doi.org/10.3390/w17172590 - 1 Sep 2025

Abstract

Nitrate leaching from agricultural soils is a major contributor to groundwater contamination and non-point source pollution. Controlling this loss remains challenging due to the complexity of soil–water–nutrient interactions under intensive farming practices. Biochar, a porous, carbon-rich material derived from biomass pyrolysis, has emerged [...] Read more.

Nitrate leaching from agricultural soils is a major contributor to groundwater contamination and non-point source pollution. Controlling this loss remains challenging due to the complexity of soil–water–nutrient interactions under intensive farming practices. Biochar, a porous, carbon-rich material derived from biomass pyrolysis, has emerged as a promising amendment for nitrate mitigation. This review summarizes recent advances in understanding the roles of biochar in nitrate retention and transformation in soils, including both direct mechanisms—such as surface adsorption, ion exchange, and pore entrapment—and indirect mechanisms—such as enhanced microbial activity, soil structure improvement, and root system development. Field and laboratory evidence shows that biochar can reduce NO₃⁻-N leaching by 15–70%, depending on its properties, soil conditions, and application context. However, inconsistencies in performance due to differences in biochar types, soil conditions, and environmental factors remain a major barrier to widespread adoption. This review also suggests current knowledge gaps and research needs, including long-term field validation, biochar material optimization, and integration of biochar into precision nutrient management. Overall, biochar presents a multifunctional strategy for reducing nitrate leaching and promoting sustainable nitrogen management in agroecosystems. Full article

(This article belongs to the Special Issue Advanced Research in Non-Point Source Pollution of Watersheds)

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17 pages, 2666 KB

Open AccessArticle

Effluent Dissolved Carbon Discharge from Two Municipal Wastewater Treatment Plants to the Mississippi River

by Anamika Dristi and Yijun Xu

Water 2025, 17(17), 2589; https://doi.org/10.3390/w17172589 - 1 Sep 2025

Abstract

Nutrient and carbon transport from the Mississippi River to the Gulf of Mexico have been investigated intensively. However, little is known about the direct human contribution of carbon from wastewater treatment plants (WWTPs) to this large river, a source that can be termed [...] Read more.

Nutrient and carbon transport from the Mississippi River to the Gulf of Mexico have been investigated intensively. However, little is known about the direct human contribution of carbon from wastewater treatment plants (WWTPs) to this large river, a source that can be termed as Cultural Carbon. This study analyzed dissolved carbon in effluents from two municipal WWTPs on the bank of the Mississippi River in Baton Rouge, South Louisiana, USA. One of the WWTPs (WWTP North) is a conventional wastewater treatment facility with a treatment capacity of 40 million gallons per day (MGD), while the other (WWTP South) is a recently upgraded facility with a treatment capacity of 200 MGD. From September 2022 to November 2024, river water and effluent samples were collected monthly to analyze dissolved organic carbon (DOC) and dissolved inorganic carbon (DIC) concentrations and their mass transport. The study found significantly higher monthly average DIC (56.80 ± 16.51 mg/L) and DOC (29.52 ± 8.68 mg/L) concentrations in the effluent of WWTP North than in the effluent of WWTP South (DIC: 42.64 ± 10.50 mg/L and DOC: 12.93 ± 3.68 mg/L). Effluents from both WWTPs had substantially greater DOC and DIC levels than the Mississippi River water (DIC: 28.92 ± 4.91 mg/L and DOC: 5.47 ± 2.35 mg/L). WWTP North discharged, on average, 3.80 MT of DIC and 1.95 MT of DOC per day, whereas WWTP South discharged 6.27 MT of DIC and 1.92 MT of DOC per day, resulting in a total annual load of 3808 MT of DIC and 1459 MT of DOC entering the Mississippi River. Considering the large number of WWTPs within the Mississippi River Basin, these findings highlight a significant contribution of effluents to riverine carbon, suggesting that basin-wide carbon budgets and regional climate assessments must take them into account. The findings from this study can be useful for federal and state policymakers, as well as researchers and engineers involved in carbon science, climate change, and water quality assessment of the Mississippi River Basin and beyond. Full article

(This article belongs to the Special Issue Biogeochemical Processes in Lakes, Ponds and Reservoirs of Urban Environments)

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20 pages, 9454 KB

Open AccessArticle

Peroxymonosulfate Activation by Sludge-Derived Biochar via One-Step Pyrolysis: Pollutant Degradation Performance and Mechanism

by Yi Wang, Liqiang Li, Hao Zhou and Jingjing Zhan

Water 2025, 17(17), 2588; https://doi.org/10.3390/w17172588 (registering DOI) - 1 Sep 2025

Abstract

Municipal wastewater treatment relies primarily on biological methods, yet effective disposal of residual sludge remains a major challenge. Converting sludge into biochar via oxygen-limited pyrolysis presents a novel approach for waste resource recovery. This study prepared sludge-based biochar (SBC) through one-step pyrolysis of [...] Read more.

Municipal wastewater treatment relies primarily on biological methods, yet effective disposal of residual sludge remains a major challenge. Converting sludge into biochar via oxygen-limited pyrolysis presents a novel approach for waste resource recovery. This study prepared sludge-based biochar (SBC) through one-step pyrolysis of sewage sludge and applied it to activate peroxymonosulfate (PMS) for degrading diverse contaminants. Characterization (SEM, XPS, FTIR) revealed abundant pore structures and diverse surface functional groups on SBC. Using Acid Orange 7 (AO7) as the target pollutant, SBC effectively degraded AO7 across pH 3.0–9.0 and catalyst dosages (0.2–2.0 g·L⁻¹), achieving a maximum observed rate constant (k_obs) of 0.3108 min^–1. Salinity and common anions showed negligible inhibition on AO7 degradation. SBC maintained 95% degradation efficiency after four reuse cycles and effectively degraded sulfamethoxazole, sulfamethazine, and rhodamine B besides AO7. Mechanistic studies (chemical quenching and ESR) identified singlet oxygen (¹O₂) and superoxide radicals (O₂^•− ) as the dominant reactive oxygen species for AO7 degradation. XPS indicated a 39% reduction in surface carbonyl group content after cycling, contributing to activity decline. LC-MS identified five intermediates, suggesting a potential degradation pathway driven by SBC/PMS system. ECOSAR model predictions indicated significantly reduced biotoxicity of the degradation products compared to AO7. This work provides a strategy for preparing sludge-derived catalysts for PMS activation and pollutant degradation, enabling effective solid waste resource utilization. Full article

(This article belongs to the Special Issue Application of Advanced Oxidation Processes (AOPs) for Wastewater Treatment)

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21 pages, 4910 KB

Open AccessArticle

Paleontological Evidence for a Northward Shift of the Climate Zone During the Qin and Han Dynasties—A Case of Paleontology from Lake Deposits in the Salawusu River Basin, Mu Us Desert, China

by Dongfeng Niu, Baosheng Li, Shuhuan Du, Xiaohao Wen, Yansheng Wen, Peixian Shu, Qingyuan Bai, Fengnian Wang, Yuejun Si and Min Chen

Water 2025, 17(17), 2587; https://doi.org/10.3390/w17172587 - 1 Sep 2025

Abstract

The lacustrine horizon (thickness of 8.75 cm thick) of the Qin and Han dynasties (221 BC–220 AD) was determined based on AMS-¹⁴C analysis conducted by the Beta Analytic Radiocarbon Dating Laboratory on the Dishaogouwan section (37°43′ N, 108°31′ E) in the [...] Read more.

The lacustrine horizon (thickness of 8.75 cm thick) of the Qin and Han dynasties (221 BC–220 AD) was determined based on AMS-¹⁴C analysis conducted by the Beta Analytic Radiocarbon Dating Laboratory on the Dishaogouwan section (37°43′ N, 108°31′ E) in the Salawusu River Basin, Mu Us Desert, located in the temperate zone of China. The identification results of the ostracod and charophyta fossils from the four samples at this horizon show the following results: 1. All the samples contain 458 ostracod fossil valves, belonging to six genera and eight species. Their quantity (valves) and percentage, in descending order of abundance, are Candoniella albicans (Brady), 255/55.68%, Ilyocypris bradyi Sars, 73/15.94%, Eucypris inflata Sars, 46/10.04%, Cyclocypris serena Koch, 26/5.68%, Candona kirgizica Mandelstam, 18/3.93%, Ilyocypris biplicata (Koch), 17/3.71%, Candoniella mirabilis Schneider14/3.06% and Leucocytherella sinensis Huang, 6/1.31%. 2. All the samples contain 99 fossil charophyte gyrogonites, belonging to one genera and four species. In terms of quantity/percentage, the Chara sp. is the most abundant, with 41 pieces (41.41%), followed by Chara braunii Gemlin, with 26 pieces (26.26%); Chara leptosperma Braun and Chara canescens Loiseleur account for 19 pieces (19.19%) and 13 pieces (13.13%), respectively. Based on the analysis of the ecological environment of the existing species of these ostracods and charophytes, combined with the fossilized Ilyocypris brady, Ilyocypris biplicata, and Gyraulus convexiusculus Hutton found in all the samples—which indicate very warm, even subtropical climates then—it can be concluded that during the Qin and Han Dynasties, the Salawusu River Basin was primarily characterized by a freshwater lake environment under a warm climate, with the average annual temperature and precipitation in this area approximately 2.1 °C and 100 mm higher than they are currently. The prevailing East Asian summer monsoon pushed the warm temperate climate at least 110 km northwestward from this basin. During this period, there were at least four episodes of brief subtropical climate fluctuations, occurring approximately every 110 years. Full article

(This article belongs to the Special Issue Trend Prediction and Analysis of Climate and Hydrological Changes in the Basin)

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23 pages, 6078 KB

Open AccessArticle

Hydroclimate Drivers and Spatiotemporal Dynamics of Reference Evapotranspiration in a Changing Climate

by Aamir Shakoor, Sabab Ali Shah, Muhammad Nouman Sattar, Akinwale T. Ogunrinde, Raied Saad Alharbi and Faizan ur Rehman

Water 2025, 17(17), 2586; https://doi.org/10.3390/w17172586 - 1 Sep 2025

Abstract

Evapotranspiration (ET) variation is typically influenced by climatic factors, which are considered the primary drivers of agricultural water requirements. Any changes in ET rates directly affect crop water demands. In this study, temporal trends and magnitudes of key climatic variables, and their impacts [...] Read more.

Evapotranspiration (ET) variation is typically influenced by climatic factors, which are considered the primary drivers of agricultural water requirements. Any changes in ET rates directly affect crop water demands. In this study, temporal trends and magnitudes of key climatic variables, and their impacts on reference evapotranspiration (ETo) during 1981–2020, were evaluated across 36 districts of Punjab, Pakistan. Positive serial correlations, ranging from 0.29 to 0.48, were identified and removed using the pre-whitening technique. Increasing trends in maximum temperature (Tmax) and wind speed (WS) across Punjab and its subregions were observed, while relative humidity (RH) exhibited both increasing and decreasing trends. No significant trends were detected for the minimum temperature (Tmin). On a monthly scale, in the Southern Punjab (SP) region, Sen’s slope estimated an increase in ETo, ranging from 0.239 mm/year in November to 0.636 mm/year in May, at a significance level of α = 0.05 (5%). At the provincial scale, significant upward trends in ETo were observed for the annual, Kharif, and autumn seasons, with Z-values of 2.04, 2.16, and 3.13, respectively, at α = 0.05 and 0.01. It was determined that, on an annual scale in Punjab, ETo sensitivity to climatic parameters followed the following order: Tmax > wind speed (WS) > Tmin > RH. The best-fitted models for Tmax, Tmin, WS, and RH were Gaussian, exponential, and spherical. ETo was found to increase spatially from North to South Punjab, with an approximate rise of 70–80 mm/decade. The results provide a scientific basis for understanding hydroclimatic drivers of ETo in semi-arid regions and contribute to improving climate impact assessments on agricultural water use. The observed ETo increases, particularly in South Punjab and lower Central Punjab, highlight the need for region-specific irrigation scheduling and water allocation. These findings can guide cropping calendars, improve irrigation efficiency, and increase canal water supplies to high-ETo areas, supporting adaptive strategies against climate variability in Punjab. Full article

(This article belongs to the Special Issue Advances and Challenges in Hydro-Climatological Modeling and Uncertainty Analysis)

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23 pages, 5495 KB

Open AccessArticle

Assessing the Accuracy of Gridded Precipitation Products in the Campania Region, Italy

by Muhammad Shareef Shazil, Muhammad Aleem, Sheharyar Ahmad, Abdullah Abdullah and Roberto Greco

Water 2025, 17(17), 2585; https://doi.org/10.3390/w17172585 - 1 Sep 2025

Abstract

Accurate precipitation data are essential for hydrological modeling, climate studies, and water resource management. Indeed, there is an increasing focus on understanding shifts in precipitation events to monitor the risks of floods and droughts, as well as to ensure sustainable water resource management. [...] Read more.

Accurate precipitation data are essential for hydrological modeling, climate studies, and water resource management. Indeed, there is an increasing focus on understanding shifts in precipitation events to monitor the risks of floods and droughts, as well as to ensure sustainable water resource management. This study compares four reanalysis and satellite precipitation products (ERA5-Land, CHIRPS, PERSIANN, and TerraClimate) with ground data from 2003 to 2022. Among the datasets evaluated, ERA5-Land has the best performance (overall) in reproducing ground data, with a minimal mean bias error (MBE) of 1.91 mm, the highest correlation coefficient (R² = 0.93), and the most favorable Nash–Sutcliffe efficiency (NSE = 0.93). In contrast, CHIRPS, PERSIANN, and TerraClimate significantly underestimate precipitation as compared to ground data. The categorical metrics also highlight ERA5-Land’s superior performance in identifying wet months. Spatial analysis shows that ERA5-Land and other datasets generally exhibit agreement regarding precipitation patterns. However, PERSIANN displays notable variances, particularly in northern regions, where it overestimates precipitation. To investigate possible changes in precipitation patterns, a longer period (1983–2022) is selected for trend analysis based on gridded precipitation products. Sen’s slope analysis does not reveal any significant annual precipitation trend. In autumn, the PERSIANN dataset indicates a significant increasing trend of +1.81 mm/year, which is also confirmed by ERA5-Land (+2.68 mm/year) and CHIRPS (+1.34 mm/year), although without statistical significance. The findings emphasize the need for more sophisticated satellite algorithms and integration with ground observations to improve precipitation accuracy. Full article

(This article belongs to the Section Hydrology)

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1 pages, 116 KB

Open AccessCorrection

Correction: Ma, Y.; Song, T. A Bibliometric Review and Interdisciplinary Analysis of the Brahmaputra River. Water 2024, 16, 3115

by Yisha Ma and Tao Song

Water 2025, 17(17), 2584; https://doi.org/10.3390/w17172584 - 1 Sep 2025

Abstract

There was an error in the original publication [...] Full article

(This article belongs to the Special Issue The Interrelationship Between Climate Change, Human Activities and Hydrological Processes (3rd Edition))

20 pages, 2498 KB

Open AccessArticle

Combined Effects of Carbon-to-Nitrogen (C/N) Ratio and Nitrate (NO₃⁻-N) Concentration on Partial Denitrification (PD) Performance at Low Temperature: Substrate Variation, Nitrite Accumulation, and Microbial Transformation

by Ying Cai, Yujun Song, Tangbing Yin, Miao Zhang and Junjie Ji

Water 2025, 17(17), 2583; https://doi.org/10.3390/w17172583 - 1 Sep 2025

Abstract

In this study, the combined effects of influent carbon-to-nitrogen ratio (C/N = 0.8, 1.5, 2.5, 3.5, 4.5) and nitrate (NO₃⁻-N) concentration (40 and 80 mg/L, labeled as R₄₀ and R₈₀) on the partial denitrification (PD) performance were [...] Read more.

In this study, the combined effects of influent carbon-to-nitrogen ratio (C/N = 0.8, 1.5, 2.5, 3.5, 4.5) and nitrate (NO₃⁻-N) concentration (40 and 80 mg/L, labeled as R₄₀ and R₈₀) on the partial denitrification (PD) performance were investigated using an intermittent sequencing batch reactor (SBR) process. With sodium acetate as an additional carbon source, the substrate variation, microbial diversity, and functional bacteria evolution were also explored to reveal the nitrite (NO₂⁻-N) accumulation mechanism at low temperatures (3–12 °C). The results showed that the 3.5-R₄₀ and 2.5-R₈₀ systems both presented the optimal NO₂⁻-N accumulation at a temperature of 10 °C, with the NO₂⁻-N transformation rate (NTR) of 66.89% and 76.79%, respectively. In addition, as the temperature reduced from 10 °C to 5 °C, the NO₂⁻-N accumulation performance was significantly suppressed, where the average effluent NO₂⁻-N of 3.5-R₄₀ (20.00 → 11.00 mg/L) and 2.5-R₈₀ (43.00 → 18.90 mg/L) systems reduced by nearly half. It is worth noting that there was almost no NO₂⁻-N accumulation at a C/N ratio of 0.8, although higher NO₃⁻-N concentration promoted NTR under the same C/N ratio. The high-throughput sequencing showed that the minimum Shannon value of 3.81 and the maximum Simpson value of 0.095 both occurred at a C/N ratio of 2.5, suggesting the downshifted microbial richness. Proteobacteria and Bacteroides increased significantly from 35.31% and 18.34% to 51.69–60.35% and 18.08–35.21%, as compared with the seeding sludge. Thauera and Flavobacterium as the main contributors to NO₂⁻-N accumulation accounted for 31.83% and 20.30% at the C/N ratio of 2.5 under a low temperature of 5 °C. The above discussion suggested that higher temperature (10 °C), lower C/N ratio (2.5–3.5), and higher NO₃⁻-N concentration (80 mg/L) were more favorable for the stable PD formation. Full article

(This article belongs to the Section Wastewater Treatment and Reuse)

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16 pages, 1739 KB

Open AccessArticle

Synthesis and Characterization of Visible-Light-Responsive TiO₂/LDHs Heterostructures for Enhanced Photocatalytic Degradation Performance

by Jing Wei and Liying Ren

Water 2025, 17(17), 2582; https://doi.org/10.3390/w17172582 - 1 Sep 2025

Abstract

A novel composite material comprising titanium dioxide and layered double hydroxides (TiO₂/LDHs) was innovatively proposed and prepared using the co-precipitation method to overcome the shortcomings of titanium dioxide, such as low efficiency in separating electron–hole pairs induced by light and a [...] Read more.

A novel composite material comprising titanium dioxide and layered double hydroxides (TiO₂/LDHs) was innovatively proposed and prepared using the co-precipitation method to overcome the shortcomings of titanium dioxide, such as low efficiency in separating electron–hole pairs induced by light and a low utilization rate of visible light. This material was used to study the visible-light-driven photocatalytic degradation of methylene blue. The experimental results show that by constructing efficient heterojunction structures through the alignment of interface band energies and regulating the interface charge transfer pathways, the recombination rate of photogenerated electron–hole pairs is significantly reduced, and the photocatalytic activity is greatly enhanced. Among the tested samples, the TiO₂/LDHs composite material with an aluminum-to-titanium molar ratio of 1:1 (AT11) demonstrated the best photocatalytic performance. Within 70 min of simulated sunlight exposure, the degradation rate of methylene blue reached 98.2%, and the optimal concentration of the catalyst was 1 g/L. The photocatalytic process follows a first-order kinetic model. After four cycles of use, the degradation efficiency of methylene blue by the AT11 composite material was 78.93%, demonstrating good stability. The free radical capture experiments indicated that the main active substances for the photocatalytic degradation of methylene blue were h⁺ and ·OH. The constructed TiO₂/LDHs heterostructure system significantly enhanced the photocatalytic performance of TiO₂ materials, which was conducive to the efficient utilization of solar energy. Full article

(This article belongs to the Special Issue Science and Technology for Water Purification, 2nd Edition)

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