Pub Date : 2026-02-01DOI: 10.1016/j.watres.2026.125490
Bingqian Xu, Hao Xing, Lu Yao, Yao Guo, Jinhui Pang, Kaixuan Wu, Jingjie Cheng, Zhenbin Wu, Qiaohong Zhou
Constructed wetlands have been widely applied in wastewater treatment. However, the dynamics of greenhouse gas (GHG) fluxes from these systems remain unclear, particularly for large-scale wetlands operating in field conditions. Here, based on a one-year field-scale investigation of an integrated vertical flow constructed wetland, we identified the key drivers of GHG fluxes fluctuations. Specifically, nitrogen input levels and variations in dissolved organic matter (DOM) characteristics played dominant roles. Our results indicated that CO2 and CH4 fluxes peaked during the plant senescence stage, with mean values of 1.20 g m‒2 h‒1, and 0.12 mg m‒2 h‒1, respectively, whereas N2O fluxes were the highest during the seedling stage, averaging 0.17 mg m‒2 h‒1. Through network and correlation analyses, we found that core species such as Algoriphagus and Stenotrophobacter were strongly associated with GHG fluxes. The partial least squares path modeling demonstrated that variations in nitrogen input (especially nitrate and ammonium) and DOM characteristics (aromaticity and molecular size) were the primary drivers influencing core species dynamics across different plant growth stages, thereby affecting GHG fluxes. Overall, our study provides new insights into the dynamics of GHG emissions in continuously operated field scale constructed wetlands, highlighting that variations in nitrogen input and DOM characteristics ultimately influence GHG fluxes.
人工湿地在污水处理中得到了广泛的应用。然而，来自这些系统的温室气体（GHG）通量的动态尚不清楚，特别是对于在野外条件下运行的大型湿地。通过对一个垂直流人工湿地进行为期一年的野外调查，我们确定了温室气体通量波动的关键驱动因素。其中，氮输入水平和溶解有机质（DOM）特征的变化起主导作用。结果表明，CO2和CH4通量在植物衰老期达到峰值，平均值分别为1.20 g m-2 h-1和0.12 mg m-2 h-1，而N2O通量在苗期最高，平均值为0.17 mg m-2 h-1。通过网络和相关分析发现，核心物种如褐藻和窄滋养菌与温室气体通量密切相关。偏最小二乘路径模型表明，氮输入（尤其是硝酸盐和铵态氮）和DOM特征（芳香性和分子大小）的变化是影响植物不同生长阶段核心物种动态的主要驱动因素，从而影响温室气体通量。总的来说，我们的研究为连续运行的野外规模人工湿地的温室气体排放动态提供了新的见解，强调了氮输入和DOM特征的变化最终影响温室气体通量。
{"title":"Nitrogen and DOM inputs alter greenhouse gas dynamics in field scale constructed wetlands treating wastewater plant effluent: insights from core species activity","authors":"Bingqian Xu, Hao Xing, Lu Yao, Yao Guo, Jinhui Pang, Kaixuan Wu, Jingjie Cheng, Zhenbin Wu, Qiaohong Zhou","doi":"10.1016/j.watres.2026.125490","DOIUrl":"https://doi.org/10.1016/j.watres.2026.125490","url":null,"abstract":"Constructed wetlands have been widely applied in wastewater treatment. However, the dynamics of greenhouse gas (GHG) fluxes from these systems remain unclear, particularly for large-scale wetlands operating in field conditions. Here, based on a one-year field-scale investigation of an integrated vertical flow constructed wetland, we identified the key drivers of GHG fluxes fluctuations. Specifically, nitrogen input levels and variations in dissolved organic matter (DOM) characteristics played dominant roles. Our results indicated that CO2 and CH4 fluxes peaked during the plant senescence stage, with mean values of 1.20 g m‒2 h‒1, and 0.12 mg m‒2 h‒1, respectively, whereas N2O fluxes were the highest during the seedling stage, averaging 0.17 mg m‒2 h‒1. Through network and correlation analyses, we found that core species such as Algoriphagus and Stenotrophobacter were strongly associated with GHG fluxes. The partial least squares path modeling demonstrated that variations in nitrogen input (especially nitrate and ammonium) and DOM characteristics (aromaticity and molecular size) were the primary drivers influencing core species dynamics across different plant growth stages, thereby affecting GHG fluxes. Overall, our study provides new insights into the dynamics of GHG emissions in continuously operated field scale constructed wetlands, highlighting that variations in nitrogen input and DOM characteristics ultimately influence GHG fluxes.","PeriodicalId":443,"journal":{"name":"Water Research","volume":"1 1","pages":""},"PeriodicalIF":12.8,"publicationDate":"2026-02-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"146101919","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}
The river continuum is fundamentally disrupted by dense cascade damming, yet the resultant CH4 emission patterns remain poorly understood. This study conducted a comprehensive annual investigation of CH4 dynamics across 15 small cascade reservoirs in the montane Wubu River, China. We found these reservoirs constitute significant CH4 hotspots, with a mean flux of 2.73 ± 2.70 mmol m-2 d-1 calculated from monthly measurements across all reservoirs. CH4 fluxes exhibited highly spatio-temporal heterogeneity in the small cascade reservoirs system. In contrast to previous reports in large river–reservoir systems, where CH4 fluxes often peak in upstream reservoirs and exhibit a pronounced longitudinal attenuation due to efficient organic matter interception, we observed marked spatial discontinuity in CH4 fluxes along this small cascade system. Rather than following longitudinal position, CH4 emission hotspots were primarily governed by reservoir scale, with relatively larger reservoir consistently exhibiting higher fluxes associated with enhanced organic matter retention and a consequent shift in sediment microbial communities toward elevated methanogenic potential (higher mcrA/pmoA gene ratio). Ebullition was the dominant emission pathway, contributing contributed an average of approximately 70.5% of total fluxes and exhibiting strong sensitivity to reservoir size, whereas diffusive fluxes showed no significant scale dependence. We calculated the annually total CH4-C release from each reservoir based on extrapolation and further quantified its ratio to the organic carbon stock within the water body (defined as “CH4 release efficiency”). We identified a progressive downstream enhancement in “CH4 release efficiency” despite spatial discontinuity in fluxes, revealing a novel “cascading efficiency” effect of intensifies methanogenic carbon processing. These findings establish that small cascade reservoirs operate under distinct biogeochemical rules where physical configuration and material transport create a spatially discontinuous yet highly efficient CH4 emission regime. Accurate assessment of their climate impact requires integration of both scale-dependent emission patterns and downstream efficiency gains in global greenhouse gas inventories.
{"title":"Scale-dependent processes drive spatially discontinuous methane emissions from small cascade reservoirs","authors":"Dongfeng Li, Yuewei Zhang, Xiaofeng Wang, Honglin Chen, Shengnan Wu, Tingting Liu, Yixin He","doi":"10.1016/j.watres.2026.125491","DOIUrl":"https://doi.org/10.1016/j.watres.2026.125491","url":null,"abstract":"The river continuum is fundamentally disrupted by dense cascade damming, yet the resultant CH<sub>4</sub> emission patterns remain poorly understood. This study conducted a comprehensive annual investigation of CH<sub>4</sub> dynamics across 15 small cascade reservoirs in the montane Wubu River, China. We found these reservoirs constitute significant CH<sub>4</sub> hotspots, with a mean flux of 2.73 ± 2.70 mmol m<sup>-2</sup> d<sup>-1</sup> calculated from monthly measurements across all reservoirs. CH<sub>4</sub> fluxes exhibited highly spatio-temporal heterogeneity in the small cascade reservoirs system. In contrast to previous reports in large river–reservoir systems, where CH<sub>4</sub> fluxes often peak in upstream reservoirs and exhibit a pronounced longitudinal attenuation due to efficient organic matter interception, we observed marked spatial discontinuity in CH<sub>4</sub> fluxes along this small cascade system. Rather than following longitudinal position, CH<sub>4</sub> emission hotspots were primarily governed by reservoir scale, with relatively larger reservoir consistently exhibiting higher fluxes associated with enhanced organic matter retention and a consequent shift in sediment microbial communities toward elevated methanogenic potential (higher <em>mcrA/pmoA</em> gene ratio). Ebullition was the dominant emission pathway, contributing contributed an average of approximately 70.5% of total fluxes and exhibiting strong sensitivity to reservoir size, whereas diffusive fluxes showed no significant scale dependence. We calculated the annually total CH<sub>4</sub>-C release from each reservoir based on extrapolation and further quantified its ratio to the organic carbon stock within the water body (defined as “CH<sub>4</sub> release efficiency”). We identified a progressive downstream enhancement in “CH<sub>4</sub> release efficiency” despite spatial discontinuity in fluxes, revealing a novel “cascading efficiency” effect of intensifies methanogenic carbon processing. These findings establish that small cascade reservoirs operate under distinct biogeochemical rules where physical configuration and material transport create a spatially discontinuous yet highly efficient CH<sub>4</sub> emission regime. Accurate assessment of their climate impact requires integration of both scale-dependent emission patterns and downstream efficiency gains in global greenhouse gas inventories.","PeriodicalId":443,"journal":{"name":"Water Research","volume":"5 1","pages":""},"PeriodicalIF":12.8,"publicationDate":"2026-02-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"146101918","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}
Pub Date : 2026-02-01DOI: 10.1016/j.watres.2026.125494
Yanan Yang , Kunfu Pi , Siyu Zhang , Mingcong Su , Yumin Zhang , Yang Wang , Yanxin Wang
The genesis of geogenic fluoride (F−)-contaminated groundwater is frequently attributed to abiotic processes, while the roles of biotransformation kinetics of redox-sensitive iron (Fe) oxides have largely been underestimated. Aluminum (Al) substitution alters the structure and surface properties of natural Fe oxides, driving dynamic shifts between F− sinks and source by modulating F− mobilization-immobilization during redox-driven Fe-oxide transformation, but the influence of Al substitution on microbial Fe(III)-oxide reduction and F− turnover remains unclear. Through field investigations, microcosm experiments, and new kinetic modeling, this research delineates biogeochemical effects of microbially-mediated reductive dissolution of varying Al(III)-substituted Fe oxides (goethite) on F− enrichment in groundwater. Results show that Al substitution governs F− mobilization-immobilization dynamics during dissimilatory goethite bioreduction. Low-level Al(III) substitution weakened the mineral lattice and enhanced F-bearing goethite bioreduction and F− release. Co-mobilized Al3+ facilitated F− stabilization by forming Al-F complexes. X-ray photoelectron spectroscopy and Fourier transform infrared spectroscopy analyses suggest that Al-F complexes reduced free F−, alleviating F− biotoxicity toward Fe-reducing bacteria and sustaining Fe(III)-oxide bioreduction even at high dissolved F− concentrations. High-level Al(III) substitution promoted Al(III) accumulation on mineral surfaces (surface-associated Al(III)), thereby preempting microbe-mineral contact sites and suppressing Fe(III) bioreduction and F− release. Bioreduction of Fe(III) in goethite led to partial F− release during the early stages, and then surface-bound Al(III) acted as a cation bridge to re-immobilize F− via surface complexation. This inhibiting effect explains decoupled Fe and F behaviors in aquifers where Fe(III) bioreduction proceeds but F− is re-immobilized by surface-bound Al(III). Our results highlight an underappreciated mechanism driving high-F groundwater under Fe(III)-reducing conditions and unravel the critical roles of microbe-mineral interactions for F mobilization/immobilization by Al(III)-substituted Fe oxides. The findings have broad implications for deciphering anionic toxic compounds enrichment in reducing groundwater and guiding rehabilitation of geogenic F-contaminated groundwater.
{"title":"Microbe-mineral interactions control fluoride mobilization from aluminum-substituted goethite into groundwater","authors":"Yanan Yang , Kunfu Pi , Siyu Zhang , Mingcong Su , Yumin Zhang , Yang Wang , Yanxin Wang","doi":"10.1016/j.watres.2026.125494","DOIUrl":"10.1016/j.watres.2026.125494","url":null,"abstract":"<div><div>The genesis of geogenic fluoride (F<sup>−</sup>)-contaminated groundwater is frequently attributed to abiotic processes, while the roles of biotransformation kinetics of redox-sensitive iron (Fe) oxides have largely been underestimated. Aluminum (Al) substitution alters the structure and surface properties of natural Fe oxides, driving dynamic shifts between F<sup>−</sup> sinks and source by modulating F<sup>−</sup> mobilization-immobilization during redox-driven Fe-oxide transformation, but the influence of Al substitution on microbial Fe(III)-oxide reduction and F<sup>−</sup> turnover remains unclear. Through field investigations, microcosm experiments, and new kinetic modeling, this research delineates biogeochemical effects of microbially-mediated reductive dissolution of varying Al(III)-substituted Fe oxides (goethite) on F<sup>−</sup> enrichment in groundwater. Results show that Al substitution governs F<sup>−</sup> mobilization-immobilization dynamics during dissimilatory goethite bioreduction. Low-level Al(III) substitution weakened the mineral lattice and enhanced F-bearing goethite bioreduction and F<sup>−</sup> release. Co-mobilized Al<sup>3+</sup> facilitated F<sup>−</sup> stabilization by forming Al-F complexes. X-ray photoelectron spectroscopy and Fourier transform infrared spectroscopy analyses suggest that Al-F complexes reduced free F<sup>−</sup>, alleviating F<sup>−</sup> biotoxicity toward Fe-reducing bacteria and sustaining Fe(III)-oxide bioreduction even at high dissolved F<sup>−</sup> concentrations. High-level Al(III) substitution promoted Al(III) accumulation on mineral surfaces (surface-associated Al(III)), thereby preempting microbe-mineral contact sites and suppressing Fe(III) bioreduction and F<sup>−</sup> release. Bioreduction of Fe(III) in goethite led to partial F<sup>−</sup> release during the early stages, and then surface-bound Al(III) acted as a cation bridge to re-immobilize F<sup>−</sup> via surface complexation. This inhibiting effect explains decoupled Fe and F behaviors in aquifers where Fe(III) bioreduction proceeds but F<sup>−</sup> is re-immobilized by surface-bound Al(III). Our results highlight an underappreciated mechanism driving high-F groundwater under Fe(III)-reducing conditions and unravel the critical roles of microbe-mineral interactions for F mobilization/immobilization by Al(III)-substituted Fe oxides. The findings have broad implications for deciphering anionic toxic compounds enrichment in reducing groundwater and guiding rehabilitation of geogenic F-contaminated groundwater.</div></div>","PeriodicalId":443,"journal":{"name":"Water Research","volume":"294 ","pages":"Article 125494"},"PeriodicalIF":12.4,"publicationDate":"2026-02-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"146097843","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}
Pub Date : 2026-01-31DOI: 10.1016/j.watres.2026.125486
Xinyu Sun, Kendra Spence Cheruvelil, Patrick J. Hanly, Katherine E. Webster, Patricia A. Soranno
{"title":"Interactions Between Human Activities and Natural Processes Shape Specific Conductance and Ion Composition of United States Lakes","authors":"Xinyu Sun, Kendra Spence Cheruvelil, Patrick J. Hanly, Katherine E. Webster, Patricia A. Soranno","doi":"10.1016/j.watres.2026.125486","DOIUrl":"https://doi.org/10.1016/j.watres.2026.125486","url":null,"abstract":"","PeriodicalId":443,"journal":{"name":"Water Research","volume":"58 1","pages":""},"PeriodicalIF":12.8,"publicationDate":"2026-01-31","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"146095586","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}
Pub Date : 2026-01-31DOI: 10.1016/j.watres.2026.125475
Bartholomeus E.M. Schaub, Gea H. van der Lee, Michiel H.S. Kraak, J. Arie Vonk, Piet F.M. Verdonschot
{"title":"Half a century of nutrient trends across spatial scales in the Rhine delta: overall improvements, but polder ditches lag behind","authors":"Bartholomeus E.M. Schaub, Gea H. van der Lee, Michiel H.S. Kraak, J. Arie Vonk, Piet F.M. Verdonschot","doi":"10.1016/j.watres.2026.125475","DOIUrl":"https://doi.org/10.1016/j.watres.2026.125475","url":null,"abstract":"","PeriodicalId":443,"journal":{"name":"Water Research","volume":"290 1","pages":""},"PeriodicalIF":12.8,"publicationDate":"2026-01-31","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"146095585","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}
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