Water Research最新文献

{"title":"The neglected role of forest eco-hydrological process representation in regulating watershed nitrogen loss","authors":"Xintong Cui, Wei Ouyang, Jiamei Wang, Roberto Xavier Supe Tulcan, Weihong Zhu","doi":"10.1016/j.watres.2025.123735","DOIUrl":"https://doi.org/10.1016/j.watres.2025.123735","url":null,"abstract":"Forest eco-hydrological functions are relevant to multiple water and ecosystem services essential for watershed management. However, these have received limited attention compared to pollution sources such as farming and fossil fuel power plants. In this study, we systematically analyzed the characteristics, pathways, and sources of nitrogen (N) loss in a forested watershed using a combination of field sampling, remote sensing, and a modified Soil and Water Assessment Tool (SWAT) model with enhanced forest eco-hydrological representation. The modified SWAT has improved the performance in simulating forest leaf area index (LAI), evapotranspiration (ET), and water and sediment yield from a mechanistic perspective (the coefficient of determination increased by 0.64 and 0.11 for monthly LAI and ET, respectively). The modified SWAT and in situ sampling were then utilized to identify the N loss pattern and physical mechanism of various sources. The results show that organic N (ORGN) loss dominated the forest N loss and contributed up to 44.37% of the total ORGN load in the upstream area. High nitrate leaching was observed in both upstream forest (0.11 ± 0.3 kg/ha) and farmland (16.21 ± 36.13 kg/ha) due to the high gravel content and soil saturated hydraulic conductivity. A comparison with forests or forested watersheds in similar northern temperate regions worldwide revealed that less-developed soil with high permeability usually has a higher nitrate leaching load than other soil types, ranging from 0.5 to 39 kg/ha/yr. Most notably, comparative analysis shows the original SWAT substantially overestimated the ORGN, nitrate loss, and nitrate leaching load from forestland by 9.69%, 26.98%, and 24.03%, respectively. Such a large difference in N source calculation can potentially mislead mitigation strategies that aim to reduce N load from diffuse sources. Advanced watershed management for sustainability and water quality should adopt an integrated approach that acknowledges the forest eco-hydrological functions in the soil-aquatic continuum.","PeriodicalId":443,"journal":{"name":"Water Research","volume":"34 1","pages":""},"PeriodicalIF":12.8,"publicationDate":"2025-04-27","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143878014","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"环境科学与生态学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Deciphering the synergistic effects and mechanisms of biochar and magnetite contained in magnetic biochar for enhancing methane production in anaerobic digestion of waste activated sludge","authors":"Hong-Yu Jin, Yong-Xiang Ren, Cong-Cong Tang, Shuai Zhang, Jiabin Wang, Ai-Juan Zhou, Bin Liang, Wenzong Liu, Aijie Wang, Zhang-Wei He","doi":"10.1016/j.watres.2025.123734","DOIUrl":"https://doi.org/10.1016/j.watres.2025.123734","url":null,"abstract":"Adding conductive materials is one of the most extensive enhancement strategies while treating waste activated sludge via anaerobic digestion. Magnetic biochar (MBC), as one composite conductive material, is capable of enhancing methane yield and production rate because of its favorable characteristics. However, whether the synergistic effects formed or not between biochar and magnetite contained in MBC on anaerobic digestion is still unclear. This study investigated the synergistic effects and corresponded mechanisms of biochar and magnetite contained in MBC with semi-continuous anaerobic digestion mode. Results showed that the co-addition of biochar and magnetite performed non-synergistic effects on methane production potential, with decrease ratios of 2.2% and 7.4% respectively compared to that in biochar and magnetite groups. Interestingly, the biochar and magnetite contained in MBC formed synergistic effects, with an extra improvement of 5.5% compared to the sum of those obtained in biochar and magnetite groups. The synergistic effects came from efficient hydrolysis and acidogenesis stages, including the thorough degradation of soluble organic matters and the rapid conversion of acetic acids. MBC also produced synergistic effects on the hydrophilia and redox properties of extracellular polymeric substances, the activities of enzymes involved in interspecies electron transfer like cytochrome c, and the contents of adenosine triphosphate (ATP). Specifically, the enhancement potentials contributed by MBC exceeded the total enhancement potential contributed by biochar and magnetite, with the extra enhancement ratios of 13.1% and 19.4% for cytochrome c and ATP, thus, the biochar and magnetite contained in MBC formed synergistic effects for promoting electron transmembrane and transfer from kinetic aspects. The correlation coefficient between methane production performance and the microbial electron transfer activity reached 0.96, correspondingly, the highest electron transfer activity of microorganism was presented in MBC. As for microbial communities, the functional and electro-active microorganisms were enriched with the addition of MBC, such as <em>Peptoclostridium, Anaerolineaceae, Methanosarcina</em>, and <em>Methanosaeta</em>, which facilitated the conversion of organic matters and established direct interspecies electron transfer methanogenesis. The findings of this study revealed the synergistic effects and mechanisms between biochar and magnetite contained in magnetic biochar in enhancing sludge anaerobic digestion, and provided an effective strategy to recover bioenergy from waste activated sludge, potentially boosting carbon neutrality in wastewater treatment.","PeriodicalId":443,"journal":{"name":"Water Research","volume":"35 1","pages":""},"PeriodicalIF":12.8,"publicationDate":"2025-04-27","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143878013","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"环境科学与生态学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Fast-selective electro-driven membrane reactor in fluoride/silica crystallization for microelectronic wastewaters recycling","authors":"Yangbo Qiu, Lei Xia, Long-Fei Ren, Chao Wan, Yiping Wan, Yan Zhao, Raf Dewil, Bart Van der Bruggen, Jiahui Shao, Chuyang Y. Tang","doi":"10.1016/j.watres.2025.123725","DOIUrl":"https://doi.org/10.1016/j.watres.2025.123725","url":null,"abstract":"Rapid growth of the microelectronic industry leads to a significant increase in the generation of microelectronic wastewaters containing complex pollutants. Resource recovery technologies offer promising solutions for effective wastewater reuse in the microelectronics sector. However, how to simultaneously achieve high-efficiency crystallization and high crystal purity of ionic resources from complex wastewater remains a challenge. Here, for the first time, we propose an electro-driven membrane reactor (EMR) for the <em>ex-situ</em> crystallization of fluoride/silica from microelectronic wastewaters as high-purity fluorosilicates. This EMR with independent chambers combines a bipolar membrane to produce protons for SiF₆^2- generation from the reaction between fluoride and silica. An internal ultrafiltration membrane is used to reject nanoparticles/organics while providing ion channels for protons and SiF₆^2- migration. Selective recovery of Na₂SiF₆ from the coexisting ions (Cl^-, SO₄^2-, NO₃^- and PO₄^3-)/nanoparticles (SiO₂, Al₂O₃ and CeO₂)/organics (tetramethylammonium hydroxide, isopropyl alcohol, bovine serum albumin, sodium alginate and humic acid) is demonstrated. Over 99.5% Na₂SiF₆ purity and 64.5% crystallization rate are verified under the optimal conditions (voltage of 8 V, UH050 membrane, operation mode Ⅰ, and forward permeate flux of 1 mL min^-1). This EMR with the advantages of accurate capture capability may be an innovative strategy for enlarging the scale of pollutant elimination, ionic resources and fresh water recovery from micro-electronic wastewaters.","PeriodicalId":443,"journal":{"name":"Water Research","volume":"135 1","pages":""},"PeriodicalIF":12.8,"publicationDate":"2025-04-26","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143876282","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"环境科学与生态学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Effects of microplastics on atrazine removal in constructed wetlands: Insight into the response characteristics of microorganisms, enzyme activity, and functional genes","authors":"Qianyin Yuan, Bo Chen, Zhen Hu, Longmian Wang, Qiaoping Kong, Jianjun Lian, Haiming Wu","doi":"10.1016/j.watres.2025.123730","DOIUrl":"https://doi.org/10.1016/j.watres.2025.123730","url":null,"abstract":"Constructed wetlands (CWs) technology has been widely used to treat agricultural non-point source pollution. However, knowledge about the impact mechanism and distribution characteristics of microplastics (MPs) on pesticide treatment in CWs is limited. This study employed atrazine (ATZ), a representative pesticide, as a model contaminant, to systematically investigate the impacts of polyethylene microplastics (PE MPs) on the removal of ATZ and nutrients, as well as the enzyme activity and the distribution of functional genes in vertical subsurface-flow CW microcosm. The results showed that compared to the control group (CK), CWs treated with different concentrations of MPs had no significant difference in the removal of ATZ. Moreover, in the second stage (ATZ=400 μg/L), the average removal efficiency of ATZ by CWs containing MPs was slightly higher than that of the CK group. PE MPs reduced the nitrogen removal efficiency of CWs by 1.57%-3.03%, but had no significant effect on TP removal. The concentration distribution of PE MPs in the substrate layer exhibited a decreasing trend from top to bottom, and the interception capacity of CWs gradually decreased with time (from 100% to 97.4%); When exposed to PE MPs, the activities of enzymes in substrate related to nitrogen metabolism were inhibited; Moreover, the addition of PE MPs in CWs promoted the removal of ATZ by increasing the abundance of ATZ metabolizing bacteria (<em>Hydrogenophaga, Zoogloea, Rhizobium</em>, etc.) and ATZ degradation key genes (<em>atzA</em> and <em>trzN</em>). These results not only provide theoretical support for the practical application of CWs in the treatment of pesticide wastewater, but also provide a theoretical basis for the environmental risk control of pesticide non-point source pollution ecological treatment technology in the presence of MPs.","PeriodicalId":443,"journal":{"name":"Water Research","volume":"7 1","pages":""},"PeriodicalIF":12.8,"publicationDate":"2025-04-26","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143877964","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"环境科学与生态学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Coupled nitrogen and phosphorus cycles mediated by coordinated variations of functional microbes in industrial recirculating aquaculture system","authors":"Shenqun An, Jiaxi Li, Jinyu Du, Li Feng, Lianbo Zhang, Xiaohua Zhang, Zhong Zhuang, Zelong Zhao, Guang Yang","doi":"10.1016/j.watres.2025.123726","DOIUrl":"https://doi.org/10.1016/j.watres.2025.123726","url":null,"abstract":"Industrial Recirculating Aquaculture Systems (IRAS) represent a sustainable and efficient approach to aquaculture, offering significant benefits in water conservation and environmental management. A comprehensive understanding of nitrogen (N) and phosphorus (P) cycling is essential for optimizing system design and operational strategies, enabling the maintenance of a balanced ecosystem within IRAS.Here, water microbial communities in the shrimp aquaculture pond (AP) and nitrification tank (NT) of the IRAS were investigated using a metagenomics-based approach to explore the mechanisms of N and P coupling cycles. Results showed that (1) N and P cycling genes were more abundant in AP water than in NT, with higher potentials for degrading organic N and P compounds, nitrate reduction, denitrification, and phosphate uptake in AP; and their hosts (functional bacteria) were identified as <em>Marivivens</em> for nitrate reduction, <em>Polaribacter</em> and <em>Erythobacter</em> for organophosphorus hydrolysis, and <em>Fluviibacter</em> and <em>Sediminibacterium</em> for phosphate uptake; (2) the coupling of N and P cycles was observed through the abundance of functional genes, likely mediated by coordinated variations in host composition, with nitrite content as a key factor influencing this variation; several bacterial species possessing both N and P cycling genes were identified, primarily engaged in the degradation of organic N and P compounds, denitrification, and phosphate uptake.This study highlights the coupling of N and P cycling in IRAS and the important role of functional bacteria in maintaining water quality. The results also have important implications for the management and improvement of IRAS for more effective aquaculture activities.","PeriodicalId":443,"journal":{"name":"Water Research","volume":"130 1","pages":""},"PeriodicalIF":12.8,"publicationDate":"2025-04-26","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143877965","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"环境科学与生态学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Aging of textile-based microfibers in both air and water environments","authors":"Shuyu Ma, Xiaopeng Min, Lin Xu, Xiaolong Jiang, Yanan Liu, Pin Gao, Peng Ji, Hyunjung Kim, Li Cai","doi":"10.1016/j.watres.2025.123731","DOIUrl":"https://doi.org/10.1016/j.watres.2025.123731","url":null,"abstract":"Textile-based microfibers (MFs) are a predominant source of global microplastics (MPs) pollution. Yet, less is known about the aging of textile-based MFs. This study explored the aging behavior of textile-based polyethylene terephthalate (PET) MFs with white (without pigment) and black (with carbon black as pigment) colors in both air and water environments. Ultraviolet (UV) and plasma aging were carried out to simulate the short- and long-term aging of MFs. Results indicated that white MFs exhibited more pronounced surface changes, formed more -OH bonds, and showed a higher increase in the oxygen-to-carbon(O/C) ratio than black MFs in both air and water environments. For example, in the air environment, the percentage increase of O/C for white MFs was 24.43%, compared to 16.4% for black MFs during plasma aging process. Further investigations were conducted to elucidate the mechanisms driving higher degree of aging of white MFs. It was verified that the carbon black in the black MFs could enhance their tensile strength and hardness, thereby countering the aging process. Furthermore, excitation-emission-matrix (EEM) analysis of dissolved organic matter (DOM) released from MFs, combined with the detection of reactive oxygen species (ROS) generated by MFs in the water environment, confirmed that carbon black functioned as an effective anti-aging additive. Its protective role, attributed to UV and plasma shielding and reactive radical-trapping mechanisms, led to higher aging degree in white MFs compared to black MFs. These findings provide insights into predicting the aging behaviors of textile-based MFs with different colors in air and water environments.","PeriodicalId":443,"journal":{"name":"Water Research","volume":"22 1","pages":""},"PeriodicalIF":12.8,"publicationDate":"2025-04-26","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143878016","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"环境科学与生态学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Sodium citrate enhances anaerobic fermentation of granular sludge: the multifaceted roles of structure disruption and metabolic regulation","authors":"Jinte Zou, Zhou Ye, Haibo Ma, Lei Cai, Jiaqi Yang, Fengfan Yu, Yinglong Su, Yifeng Chen, Jun Li","doi":"10.1016/j.watres.2025.123729","DOIUrl":"https://doi.org/10.1016/j.watres.2025.123729","url":null,"abstract":"Anaerobic fermentation is an efficient approach for recovering organic carbon and other valuable resources from waste sludge, yet its efficiency is constrained by the structural stability of extracellular polymeric substances (EPS), especially for aerobic granular sludge (AGS). Despite the abundant physical-chemical pre-treatment approaches for enhancing EPS dissolution, biocompatible strategies coordinating structural disruption with metabolic regulation remain unexplored. Herein, sodium citrate (SC) was used to enhance the performance of anaerobic fermentation of AGS. The results suggested that SC significantly enhanced the hydrolysis efficiency and volatile fatty acids (VFAs) production of AGS. Despite the direct conversion of SC to acetate, indirect enhancement played more important roles in AGS fermentation. Mechanism analysis indicated that SC disrupted granular sludge structure by chelating Ca²⁺ and facilitated the release of EPS and hydrolytic enzymes, which was conducive to sludge hydrolysis and acidification. At the level of microbial community, SC facilitated the accumulation of VFAs by enriching the acid-producing microorganisms and inhibiting the acid-consuming microorganisms. Furthermore, SC regulated the genes involved in the direct generation of acetate and pyruvate-centric metabolism, resulting in the massive accumulation of VFAs. Finally, the economic benefits resulting from increased VFA production versus SC costs. Overall, SC enhanced the anaerobic fermentation of AGS by simultaneously affecting EPS structure and regulating metabolism, and this study provided efficient methods for AGS anaerobic treatment.","PeriodicalId":443,"journal":{"name":"Water Research","volume":"6 1","pages":""},"PeriodicalIF":12.8,"publicationDate":"2025-04-26","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143877966","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"环境科学与生态学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Breakpoint electrochlorination in ammonia removal: Unveiling the impact of convective mass transfer","authors":"Aksana Atrashkevich, Dominic Varda, Kaitlyn Yeager, Maria Gomez-Mingot, Carlos M. Sánchez-Sánchez, Sergi Garcia-Segura","doi":"10.1016/j.watres.2025.123732","DOIUrl":"https://doi.org/10.1016/j.watres.2025.123732","url":null,"abstract":"Breakpoint chlorination, the point at which ammonia is completely oxidized by chlorine to nitrogen gas, may occur during electrochemical water treatment due to the simultaneous abundance of inorganic nitrogen species and chloride ions in many water matrices. Nevertheless, little is known about the difference between the chemical breakpoint chlorination and electrochemical ammonia abatement as well as the impact of the electrode-electrolyte interface that drives the breakpoint electrochlorination. This study investigates the influence of the interface on ammonia oxidation by comparing indirect breakpoint electrochlorination with chemical approach and by examining the impact of varying convective mass transfer on breakpoint electrochlorination. Our results revealed that, under identical conditions and bulk pH, breakpoint electrochlorination releases much lower residual chlorine species in the bulk solution before ammonia is oxidized, as compared to chemical breakpoint chlorination. It was observed that lower convective mass transfer not only accelerates ammonia removal but also increases the chlorine evolution reaction. Results from a closed divided cell experiment confirmed that chlorine evolution is enhanced under lower convective mass transfer, which suggests a relevant role of species distribution within electrode-electrolyte interface. We hypothesize that this effect may be due to a more acidic local pH under lower mass transfer conditions, which favors chlorine evolution over oxygen evolution reaction. These findings provide insights into the fundamental differences of chemical breakpoint chlorination and indirect breakpoint electrochlorination. The results can guide operating strategies for electrochemical water treatment that can potentially reduce energy consumption by lowering flow speeds, while achieving higher chlorine yield and faster ammonia removal.","PeriodicalId":443,"journal":{"name":"Water Research","volume":"16 1","pages":""},"PeriodicalIF":12.8,"publicationDate":"2025-04-26","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143878017","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"环境科学与生态学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Advancing aquatic ecological risk assessment of imidacloprid in global surface water with mesocosm-based thresholds","authors":"Huizhen Li, Lingzhi Xie, Zewei Xu, Fei Cheng, Jing You","doi":"10.1016/j.watres.2025.123728","DOIUrl":"https://doi.org/10.1016/j.watres.2025.123728","url":null,"abstract":"Aquatic ecological risk posed by neonicotinoids has become a growing concern due to their widespread use and documented environmental impacts. However, current risk assessments predominantly rely on laboratory-based toxicity data, which often lack ecological relevance and may introduce substantial biases. In this study, we addressed a critical knowledge gap in neonicotinoid risk assessment by establishing the first global-scale comparison between traditional laboratory-based and ecologically realistic mesocosm-derived toxicity thresholds. Analysis of literature-reported concentrations revealed significant regional variations in imidacloprid pollution at a global scale, with the highest median concentrations detected in Oceania, followed by Asia, Africa, America, and Europe, although extreme concentrations were observed in America. The mesocosm-based hazard concentration for 5% of species (HC5) was determined to be 0.013 μg/L, which was significantly lower than the laboratory-based HC5 of 0.086 μg/L. Risk assessment using the laboratory-based threshold identified 1.2% of the 1,378 freshwater samples as high risk (risk quotient, RQ&gt;10) and 7.1% as medium risk (1&lt;RQ&lt;10), with majority of sites at risk located in American. In contrast, applying the mesocosm-based threshold revealed a substantial increase in risk, with 5% of sites classified as high risk and 32% as medium risk. In addition, the dominant medium-risk sites shifted from America to Asia and Europe. These findings underscore that the laboratory-based threshold significantly underestimates aquatic ecological risk of imidacloprid on a large scale, especially in Asia. Alternatively, the mesocosm-based threshold provides a more ecologically relevant assessment of risks in real-world aquatic environments. The present study highlights the critical need for incorporating ecologically relevant toxicity data into global risk assessments to better inform regulatory decisions and environmental protection strategies.","PeriodicalId":443,"journal":{"name":"Water Research","volume":"31 1","pages":""},"PeriodicalIF":12.8,"publicationDate":"2025-04-26","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143876240","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"环境科学与生态学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Bicarbonate Boosts the Anaerobic Generation of Reactive Oxygen Species by Hydrochar: Surface Oxygenated Functional Groups Activation and Hexavalent Chromium Removal","authors":"Na Chen, Xianglei Zhang, Yongliang Xu, Zelin Hao, Lang Zhu, Hanzhong Jia","doi":"10.1016/j.watres.2025.123727","DOIUrl":"https://doi.org/10.1016/j.watres.2025.123727","url":null,"abstract":"Hydrochar can generate reactive oxygen species (ROS) via activating molecular oxygen under sunlight. However, whether and how hydrochar generates ROS in the dark and anaerobic environments remains unknown. Herein, we found that combining hydrochar with the co-existing bicarbonate could generate superoxide radicals (O₂^•−) under alkaline conditions, with the maximum concentration reaching 24.7 μmol L⁻¹. Interestingly, the O₂^•−generation was not affected by eliminating the molecular oxygen but highly depended on the abundance of the oxygenated functional groups (OFGs) on hydrochar surface. The results of electrochemical analysis, density functional theory calculation, and surface characterization elucidated that the bicarbonate first inner-sphere complexed with surface OFGs, followed by the electron transfer from bicarbonate to OFGs. This enabled the activation of oxygen inside OFGs into active oxygen (O*) while bicarbonate was oxidized to carbonate radical (CO₃^•-). The CO₃^•- further reacts with O* through an oxygen transfer mechanism, resulting in the generation of O₂^•-. The generated O₂^•− was used for the Cr(VI) treatment, which could efficiently reduce over 95% into Cr(III). The findings provide a novel pathway for developing hydrochar-based advanced oxidation processes and highlight the potential of hydrochar in pollutant transformation mediated by ROS in dark and anaerobic water environments.","PeriodicalId":443,"journal":{"name":"Water Research","volume":"69 1","pages":""},"PeriodicalIF":12.8,"publicationDate":"2025-04-26","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143878015","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"环境科学与生态学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}