Pub Date : 2026-03-01Epub Date: 2026-02-17DOI: 10.1016/j.jconhyd.2026.104896
Stanislav Paseka , Daniel Marton , Michael Krapesch , Helmut Habersack , Martin Bednář , Marlene Haimann
Sediment transport plays a key role in riverine processes and water quality regulation, yet remains challenging to quantify, particularly in transboundary and regulated catchments. This study presents a coordinated, long-term monitoring approach across eight stations in the Thaya River basin (Austria and Czech Republic), combining turbidity sensors, flow data, and manual sampling. Relationships between turbidity and suspended sediment concentration were established through site-specific regression, with R2 values exceeding 0.95 at three stations. Results revealed pronounced spatial variability in sediment loads, driven by land use, reservoir trapping, and tributary inputs. The Vranov, Znojmo and Nové Mlýny reservoirs significantly reduced sediment transport, although downstream recovery occurred due to tributary inflows. Maintenance requirements, sensor fouling, and deployment geometry strongly influenced data reliability, underscoring the need for standardized protocols in multi-site networks. The dataset enhances sediment budget estimation and reservoir sedimentation forecasts, supporting adaptive catchment-scale sediment management and meeting European water policy objectives.
{"title":"Integrated monitoring of suspended sediment transport in a transboundary river basin: Insights into sediment fluxes and reservoir effects in the Thaya catchment","authors":"Stanislav Paseka , Daniel Marton , Michael Krapesch , Helmut Habersack , Martin Bednář , Marlene Haimann","doi":"10.1016/j.jconhyd.2026.104896","DOIUrl":"10.1016/j.jconhyd.2026.104896","url":null,"abstract":"<div><div>Sediment transport plays a key role in riverine processes and water quality regulation, yet remains challenging to quantify, particularly in transboundary and regulated catchments. This study presents a coordinated, long-term monitoring approach across eight stations in the Thaya River basin (Austria and Czech Republic), combining turbidity sensors, flow data, and manual sampling. Relationships between turbidity and suspended sediment concentration were established through site-specific regression, with R<sup>2</sup> values exceeding 0.95 at three stations. Results revealed pronounced spatial variability in sediment loads, driven by land use, reservoir trapping, and tributary inputs. The Vranov, Znojmo and Nové Mlýny reservoirs significantly reduced sediment transport, although downstream recovery occurred due to tributary inflows. Maintenance requirements, sensor fouling, and deployment geometry strongly influenced data reliability, underscoring the need for standardized protocols in multi-site networks. The dataset enhances sediment budget estimation and reservoir sedimentation forecasts, supporting adaptive catchment-scale sediment management and meeting European water policy objectives.</div></div>","PeriodicalId":15530,"journal":{"name":"Journal of contaminant hydrology","volume":"278 ","pages":"Article 104896"},"PeriodicalIF":4.4,"publicationDate":"2026-03-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"146227115","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"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 : 2026-03-01Epub Date: 2026-02-10DOI: 10.1016/j.jconhyd.2026.104886
Sifat Azad Papry , Reza Rahimi , Tarek L. Rashwan , Pulin Mondal , Mehran Behazin , Peter G. Keech , Magdalena Krol
The long-term performance of the Canadian deep geologic repository (DGR) relies significantly on bentonite clay, as sealing materials intended for use in the engineered barrier system (EBS). One particular safety concern is microbiologically influenced corrosion of the used fuel containers (UFCs) which may occur if bisulfide (HS−) transports through the bentonite buffer to reach the UFC surface and corrode the copper coating. Understanding HS− sorption onto bentonite is therefore an important aspect of this problem, as HS− sorption can reduce the extent of copper corrosion. However, sorption dynamics onto bentonite are not yet well-understood. As such, this study performed laboratory batch experiments to investigate HS− sorption onto bentonite slurries as a function of temperature (10–40 °C), pH (9–11), and ionic strength (0.01 M–1 M NaCl). These conditions were aimed to reflect the range of possible DGR geochemical conditions. The experimental results showed that HS− sorption onto bentonite increased with increasing temperature but decreased with increasing pH and ionic strength. A 3-way ANOVA (analysis of variance) showed that the variables' individual and 2-way interaction effects are statistically significant, which implies that they should be incorporated into a sorption mechanism. A thermodynamic-based sorption model was also developed in PHREEQC assuming that sorption was driven by three key processes: (i) redox reaction with the structural Fe3+ sites, (ii) surface precipitation as FeS (mackinawite), and (iii) surface complexation reactions with surface hydroxyl group (OH) at the edge sites of montmorillonite. The model successfully described the main experimental trends and provided valuable insights into the relative contribution of these processes to the total HS− sorption mechanism. Altogether, this study provides novel insights from experimental and numerical modelling findings that enhance the understanding of HS− sorption onto bentonite, in the context of Canadian DGR design as well as other nuclear repositories worldwide.
{"title":"Exploring the effects of pH, ionic strength, and temperature on bisulfide sorption onto bentonite via experiments and numerical modelling","authors":"Sifat Azad Papry , Reza Rahimi , Tarek L. Rashwan , Pulin Mondal , Mehran Behazin , Peter G. Keech , Magdalena Krol","doi":"10.1016/j.jconhyd.2026.104886","DOIUrl":"10.1016/j.jconhyd.2026.104886","url":null,"abstract":"<div><div>The long-term performance of the Canadian deep geologic repository (DGR) relies significantly on bentonite clay, as sealing materials intended for use in the engineered barrier system (EBS). One particular safety concern is microbiologically influenced corrosion of the used fuel containers (UFCs) which may occur if bisulfide (HS<sup>−</sup>) transports through the bentonite buffer to reach the UFC surface and corrode the copper coating. Understanding HS<sup>−</sup> sorption onto bentonite is therefore an important aspect of this problem, as HS<sup>−</sup> sorption can reduce the extent of copper corrosion. However, sorption dynamics onto bentonite are not yet well-understood. As such, this study performed laboratory batch experiments to investigate HS<sup>−</sup> sorption onto bentonite slurries as a function of temperature (10–40 °C), pH (9–11), and ionic strength (0.01 M–1 M NaCl). These conditions were aimed to reflect the range of possible DGR geochemical conditions. The experimental results showed that HS<sup>−</sup> sorption onto bentonite increased with increasing temperature but decreased with increasing pH and ionic strength. A 3-way ANOVA (analysis of variance) showed that the variables' individual and 2-way interaction effects are statistically significant, which implies that they should be incorporated into a sorption mechanism. A thermodynamic-based sorption model was also developed in PHREEQC assuming that sorption was driven by three key processes: (i) redox reaction with the structural Fe<sup>3+</sup> sites, (ii) surface precipitation as FeS (mackinawite), and (iii) surface complexation reactions with surface hydroxyl group (OH) at the edge sites of montmorillonite. The model successfully described the main experimental trends and provided valuable insights into the relative contribution of these processes to the total HS<sup>−</sup> sorption mechanism. Altogether, this study provides novel insights from experimental and numerical modelling findings that enhance the understanding of HS<sup>−</sup> sorption onto bentonite, in the context of Canadian DGR design as well as other nuclear repositories worldwide.</div></div>","PeriodicalId":15530,"journal":{"name":"Journal of contaminant hydrology","volume":"278 ","pages":"Article 104886"},"PeriodicalIF":4.4,"publicationDate":"2026-03-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"146201949","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"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 : 2026-03-01Epub Date: 2026-02-16DOI: 10.1016/j.jconhyd.2026.104888
Zhixin Chen , Rainer Helmig , Liming Hu
In-situ thermal desorption is widely applied to remediate vadose-zone soils impacted by non-aqueous phase liquids (NAPLs), yet the role of adsorbed-phase desorption kinetics in thermal processes has received little attention. Moreover, although several thermal technologies have been studied separately, there is still a lack of quantitative comparison of their remediation performance and energy efficiency within a unified modelling framework. Here, we extend a non-isothermal compositional multiphase-flow model by explicitly coupling a kinetic description of contaminant desorption from the adsorbed phase, and apply it to simulate the removal of n-dodecane (C12) from unsaturated soil using three representative thermal approaches: saturated steam-enhanced extraction (Sat-SEE), superheated steam-enhanced extraction (SSEE), and thermal conductive heating (TCH). The model is used to compare multiphase removal efficiencies and specific energy consumption, and to perform a sensitivity analysis of the kinetic parameters. Simulation results show that, with increasing injection rate, SSEE achieves substantially higher removal of C12 than TCH at comparable or lower specific energy consumption. Both the injection rate and the temperature of the injected steam enhance remediation performance by enlarging the superheated zone that controls adsorbed-phase desorption. The sensitivity analysis identifies activation energy as the dominant kinetic parameter, exerting a stronger control on desorption behavior and required heating temperature than the pre-exponential factor or reaction model. The extended model thus provides a mechanistic basis for designing thermal remediation strategies and selecting appropriate thermal technologies for NAPL-contaminated sites.
{"title":"Numerical investigation of multiphase contaminant removal from NAPL-impacted soils: A comparative study of thermal desorption approaches","authors":"Zhixin Chen , Rainer Helmig , Liming Hu","doi":"10.1016/j.jconhyd.2026.104888","DOIUrl":"10.1016/j.jconhyd.2026.104888","url":null,"abstract":"<div><div>In-situ thermal desorption is widely applied to remediate vadose-zone soils impacted by non-aqueous phase liquids (NAPLs), yet the role of adsorbed-phase desorption kinetics in thermal processes has received little attention. Moreover, although several thermal technologies have been studied separately, there is still a lack of quantitative comparison of their remediation performance and energy efficiency within a unified modelling framework. Here, we extend a non-isothermal compositional multiphase-flow model by explicitly coupling a kinetic description of contaminant desorption from the adsorbed phase, and apply it to simulate the removal of n-dodecane (C<sub>12</sub>) from unsaturated soil using three representative thermal approaches: saturated steam-enhanced extraction (Sat-SEE), superheated steam-enhanced extraction (SSEE), and thermal conductive heating (TCH). The model is used to compare multiphase removal efficiencies and specific energy consumption, and to perform a sensitivity analysis of the kinetic parameters. Simulation results show that, with increasing injection rate, SSEE achieves substantially higher removal of C<sub>12</sub> than TCH at comparable or lower specific energy consumption. Both the injection rate and the temperature of the injected steam enhance remediation performance by enlarging the superheated zone that controls adsorbed-phase desorption. The sensitivity analysis identifies activation energy as the dominant kinetic parameter, exerting a stronger control on desorption behavior and required heating temperature than the pre-exponential factor or reaction model. The extended model thus provides a mechanistic basis for designing thermal remediation strategies and selecting appropriate thermal technologies for NAPL-contaminated sites.</div></div>","PeriodicalId":15530,"journal":{"name":"Journal of contaminant hydrology","volume":"278 ","pages":"Article 104888"},"PeriodicalIF":4.4,"publicationDate":"2026-03-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"146258241","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"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 : 2026-03-01Epub Date: 2026-02-22DOI: 10.1016/j.jconhyd.2026.104902
Matt Dumont , Connor Cleary , Richard McDowell
Rigorously incorporating the lag between management actions and changes in water quality is essential to better manage NO3N (nitrate nitrogen) in groundwater. We present a fast data driven Bayesian inference model. It combines lumped parameter age models with measured NO3N concentrations to estimate historical and future NO3N concentrations for systems with negligible denitrification. Numerical experiments showed the model to be reasonably accurate. It can accelerate the detection of, and increase the detected effect size of, NO3N reductions relative to frequentist approaches. For instance, the model detects 20%–60% of the true effect as compared to 5%–25% for frequentist approaches when the mean residence time is greater than 10 years. Using the model for all groundwater sites with age data in New Zealand, we predict NO3N concentrations in New Zealand will increase significantly, with 20% of monitored wells exceeding the drinking water standard at steady state. NO3N reductions of 20% or more are required to maintain the current 15% of wells over the standard. The model allows much faster, lower cost, investigations with fewer data requirements than traditional approaches. We find that the model is a useful tool for incorporating lag into NO3N management decisions, testing hypotheses about historical land management, and providing parallel lines of evidence to support decision-making.
{"title":"Bayesian inference to predict past and future nitrate concentrations","authors":"Matt Dumont , Connor Cleary , Richard McDowell","doi":"10.1016/j.jconhyd.2026.104902","DOIUrl":"10.1016/j.jconhyd.2026.104902","url":null,"abstract":"<div><div>Rigorously incorporating the lag between management actions and changes in water quality is essential to better manage NO<sub>3</sub> <img>N (nitrate nitrogen) in groundwater. We present a fast data driven Bayesian inference model. It combines lumped parameter age models with measured NO<sub>3</sub> <img>N concentrations to estimate historical and future NO<sub>3</sub> <img>N concentrations for systems with negligible denitrification. Numerical experiments showed the model to be reasonably accurate. It can accelerate the detection of, and increase the detected effect size of, NO<sub>3</sub> <img>N reductions relative to frequentist approaches. For instance, the model detects 20%–60% of the true effect as compared to 5%–25% for frequentist approaches when the mean residence time is greater than 10 years. Using the model for all groundwater sites with age data in New Zealand, we predict NO<sub>3</sub> <img>N concentrations in New Zealand will increase significantly, with 20% of monitored wells exceeding the drinking water standard at steady state. NO<sub>3</sub> <img>N reductions of 20% or more are required to maintain the current 15% of wells over the standard. The model allows much faster, lower cost, investigations with fewer data requirements than traditional approaches. We find that the model is a useful tool for incorporating lag into NO<sub>3</sub> <img>N management decisions, testing hypotheses about historical land management, and providing parallel lines of evidence to support decision-making.</div></div>","PeriodicalId":15530,"journal":{"name":"Journal of contaminant hydrology","volume":"278 ","pages":"Article 104902"},"PeriodicalIF":4.4,"publicationDate":"2026-03-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"147283045","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"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 : 2026-03-01Epub Date: 2026-02-21DOI: 10.1016/j.jconhyd.2026.104897
Fatemeh Omidi , Kimia Karimi , Marjan Hosseini , Reza Kerachian
Variations in water quality along the length and depth of a reservoir reveal anisotropic conditions, which pose significant challenges when designing effective monitoring networks. Geostatistical techniques like Bayesian maximum entropy (BME) have proven effective in designing monitoring systems, but they fall short when it comes to planning water quality monitoring in the depth and length of reservoirs. This paper introduces a novel approach for designing long-term, routine water quality monitoring networks specifically tailored for deep reservoirs. Due to the considerable anisotropy in the data and the large length-to-depth ratio of the reservoir, we modeled the anisotropies by scaling the longitudinal distances and rotating the coordinate axes. To examine long-term variations in water quality within reservoirs, a calibrated CE-QUAL-W2 hydrodynamic and water quality simulation model was employed, along with a regular hexagonal grid pattern to determine potential locations for monitoring stations. The proposed methodology outlined the ideal configuration for a reservoir water quality monitoring network, specifying the number of monitoring stations needed and the sampling frequency. The quality monitoring network was designed based on two crucial criteria: the variance of estimation error of the BME method and the sampling cost. The BME method, which can integrate information from various sources, including both hard (deterministic) and soft (stochastic) data, reduces the variance of the estimation error compared to traditional geostatistical methods, leading to more accurate estimates. Using the evidential reasoning (ER) method based on the criteria mentioned earlier, we ranked various alternatives for the locations of monitoring stations and their sampling frequencies.
We applied the proposed methodology to the Karkheh Dam reservoir, the largest reservoir in Iran, which faces notable challenges related to thermal stratification and water quality. The results suggest a monitoring network of 10 sampling stations with a 75-day sampling interval for effective water quality management. This approach offers a robust framework for water quality monitoring and resource management in large reservoirs by helping decision-makers balance accuracy, cost, and uncertainty to design resilient and cost-effective monitoring networks.
{"title":"Optimizing the spatiotemporal configuration of water quality monitoring networks in reservoirs using anisotropic Bayesian maximum entropy method","authors":"Fatemeh Omidi , Kimia Karimi , Marjan Hosseini , Reza Kerachian","doi":"10.1016/j.jconhyd.2026.104897","DOIUrl":"10.1016/j.jconhyd.2026.104897","url":null,"abstract":"<div><div>Variations in water quality along the length and depth of a reservoir reveal anisotropic conditions, which pose significant challenges when designing effective monitoring networks. Geostatistical techniques like Bayesian maximum entropy (BME) have proven effective in designing monitoring systems, but they fall short when it comes to planning water quality monitoring in the depth and length of reservoirs. This paper introduces a novel approach for designing long-term, routine water quality monitoring networks specifically tailored for deep reservoirs. Due to the considerable anisotropy in the data and the large length-to-depth ratio of the reservoir, we modeled the anisotropies by scaling the longitudinal distances and rotating the coordinate axes. To examine long-term variations in water quality within reservoirs, a calibrated CE-QUAL-W2 hydrodynamic and water quality simulation model was employed, along with a regular hexagonal grid pattern to determine potential locations for monitoring stations. The proposed methodology outlined the ideal configuration for a reservoir water quality monitoring network, specifying the number of monitoring stations needed and the sampling frequency. The quality monitoring network was designed based on two crucial criteria: the variance of estimation error of the BME method and the sampling cost. The BME method, which can integrate information from various sources, including both hard (deterministic) and soft (stochastic) data, reduces the variance of the estimation error compared to traditional geostatistical methods, leading to more accurate estimates. Using the evidential reasoning (ER) method based on the criteria mentioned earlier, we ranked various alternatives for the locations of monitoring stations and their sampling frequencies.</div><div>We applied the proposed methodology to the Karkheh Dam reservoir, the largest reservoir in Iran, which faces notable challenges related to thermal stratification and water quality. The results suggest a monitoring network of 10 sampling stations with a 75-day sampling interval for effective water quality management. This approach offers a robust framework for water quality monitoring and resource management in large reservoirs by helping decision-makers balance accuracy, cost, and uncertainty to design resilient and cost-effective monitoring networks.</div></div>","PeriodicalId":15530,"journal":{"name":"Journal of contaminant hydrology","volume":"278 ","pages":"Article 104897"},"PeriodicalIF":4.4,"publicationDate":"2026-03-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"147306331","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"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 : 2026-03-01Epub Date: 2026-02-09DOI: 10.1016/j.jconhyd.2026.104884
Matan Cohen, Brian Berkowitz
Transport of chemicals through geological porous media can exhibit a wide range of behavior, from Fickian to highly anomalous, including a range of asymptotically-Fickian behavior wherein transport conforms to Fickian behavior only at long times and/or large distances. Asymptotically-Fickian transport behavior remains under-explored in the literature, and in many cases transport is considered simply either Fickian or anomalous. Here, a spectrum-based perspective for transport of chemicals is presented, which can better describe the subtleties of asymptotically-Fickian transport. A continuous time random walk particle tracking (CTRW-PT) model is used to describe transport through porous media, considering a wide parameter space representative of a broad range of transport behavior, all within the asymptotically-Fickian regime. Experimental results of column experiments are then analyzed using the same CTRW-PT model. Combined, these two sets of results – pure simulations and modeling of experiments – show the validity and utility of allowing a wide parameter space for CTRW-PT modeling. Additionally, several easy-to-calculate parameters are assessed as possible indicators for trends in the degree of anomalous transport, particularly in the context of evolving systems.
{"title":"Exploring asymptotically-Fickian chemical transport in porous media","authors":"Matan Cohen, Brian Berkowitz","doi":"10.1016/j.jconhyd.2026.104884","DOIUrl":"10.1016/j.jconhyd.2026.104884","url":null,"abstract":"<div><div>Transport of chemicals through geological porous media can exhibit a wide range of behavior, from Fickian to highly anomalous, including a range of asymptotically-Fickian behavior wherein transport conforms to Fickian behavior only at long times and/or large distances. Asymptotically-Fickian transport behavior remains under-explored in the literature, and in many cases transport is considered simply either Fickian or anomalous. Here, a spectrum-based perspective for transport of chemicals is presented, which can better describe the subtleties of asymptotically-Fickian transport. A continuous time random walk particle tracking (CTRW-PT) model is used to describe transport through porous media, considering a wide parameter space representative of a broad range of transport behavior, all within the asymptotically-Fickian regime. Experimental results of column experiments are then analyzed using the same CTRW-PT model. Combined, these two sets of results – pure simulations and modeling of experiments – show the validity and utility of allowing a wide parameter space for CTRW-PT modeling. Additionally, several easy-to-calculate parameters are assessed as possible indicators for trends in the degree of anomalous transport, particularly in the context of evolving systems.</div></div>","PeriodicalId":15530,"journal":{"name":"Journal of contaminant hydrology","volume":"278 ","pages":"Article 104884"},"PeriodicalIF":4.4,"publicationDate":"2026-03-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"146173044","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"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 : 2026-03-01Epub Date: 2026-02-04DOI: 10.1016/j.jconhyd.2026.104881
Zechen Ding , Oubai Elagab , Qingqi Zhao , Dimin Fan , Neal Durant , Anthony Danko , Charles J Werth , Cheng Chen
The injection of granular activated carbon (GAC)-based amendments in artificially-induced fractures provides a promising solution for addressing chlorinated solvent contamination in clay-rich, low-permeability subsurface formations. Achieving high hydraulic conductivity of GAC-filled fractures is critical for long-term treatment efficiency. The evolution of the hydraulic conductivity of GAC-filled fractures in shallow clay formations against various stress and injection conditions has not been fully investigated. To close this knowledge gap, the hydraulic conductivity evolution of GAC-filled fractures created in clay-rich soil was experimentally studied. The hydraulic conductivity and permeability evolutions of sand- and GAC-filled fractures are significantly different. Under low effective stress, the hydraulic conductivity of GAC-filled fractures is more sensitive to variations in effective stress compared to sand-filled fractures, indicating that changes in ground loads might affect the long-term treatment efficiency of GAC-based amendments in shallow formations. The experiments also tested the scenario in which a mixture of sand and GAC particles is placed in the fracture. There exists a critical effective stress at which the benefit of fracture permeability enhancement caused by increased GAC mass fraction is offset by the disadvantage of fracture permeability reduction due to the low mechanical strength of GAC. Our experiments illustrate that this critical effective stress is approximately 500 psi. In practice, the closure stress imposed on an artificially-induced hydraulic fracture is generally lower than 100 psi because in shallow subsurface remediation the formation depth is usually less than 100 ft. Therefore, increasing the GAC mass fraction in particle injections is generally advantageous for enhancing fracture permeability. A double-exponential model was developed to interpret the laboratory data and to predict the minimum hydraulic conductivity of a GAC/sand-filled fracture. This work not only advances the fundamental science in contaminant hydrology, but also supports practical applications of GAC-based amendment injections for subsurface contaminant remediation.
{"title":"Placement of sand and granular activated carbon in hydraulic fractures for contaminant remediation in low-permeability formations","authors":"Zechen Ding , Oubai Elagab , Qingqi Zhao , Dimin Fan , Neal Durant , Anthony Danko , Charles J Werth , Cheng Chen","doi":"10.1016/j.jconhyd.2026.104881","DOIUrl":"10.1016/j.jconhyd.2026.104881","url":null,"abstract":"<div><div>The injection of granular activated carbon (GAC)-based amendments in artificially-induced fractures provides a promising solution for addressing chlorinated solvent contamination in clay-rich, low-permeability subsurface formations. Achieving high hydraulic conductivity of GAC-filled fractures is critical for long-term treatment efficiency. The evolution of the hydraulic conductivity of GAC-filled fractures in shallow clay formations against various stress and injection conditions has not been fully investigated. To close this knowledge gap, the hydraulic conductivity evolution of GAC-filled fractures created in clay-rich soil was experimentally studied. The hydraulic conductivity and permeability evolutions of sand- and GAC-filled fractures are significantly different. Under low effective stress, the hydraulic conductivity of GAC-filled fractures is more sensitive to variations in effective stress compared to sand-filled fractures, indicating that changes in ground loads might affect the long-term treatment efficiency of GAC-based amendments in shallow formations. The experiments also tested the scenario in which a mixture of sand and GAC particles is placed in the fracture. There exists a critical effective stress at which the benefit of fracture permeability enhancement caused by increased GAC mass fraction is offset by the disadvantage of fracture permeability reduction due to the low mechanical strength of GAC. Our experiments illustrate that this critical effective stress is approximately 500 psi. In practice, the closure stress imposed on an artificially-induced hydraulic fracture is generally lower than 100 psi because in shallow subsurface remediation the formation depth is usually less than 100 ft. Therefore, increasing the GAC mass fraction in particle injections is generally advantageous for enhancing fracture permeability. A double-exponential model was developed to interpret the laboratory data and to predict the minimum hydraulic conductivity of a GAC/sand-filled fracture. This work not only advances the fundamental science in contaminant hydrology, but also supports practical applications of GAC-based amendment injections for subsurface contaminant remediation.</div></div>","PeriodicalId":15530,"journal":{"name":"Journal of contaminant hydrology","volume":"278 ","pages":"Article 104881"},"PeriodicalIF":4.4,"publicationDate":"2026-03-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"146157284","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"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 : 2026-03-01Epub Date: 2026-02-09DOI: 10.1016/j.jconhyd.2026.104877
R. Álvarez-Alonso , P.A. Robledo Ardila , S. Deudero , C.A. Melo-Aguilar , C. Alomar , F. Micheo , J.J. Durán , S. Pérez , F. Árcega Cabrera , S. Martínez Pérez
Groundwater in Mediterranean coastal aquifers supplies a large part of the demand for freshwater but is increasingly threatened by seawater intrusion and anthropogenic pollution. During the springs of 2023 and 2024, six coastal carbonate aquifers in Mallorca were sampled to assess the present-day spatial and vertical variability of salinization and pollution. Hydrochemistry showed elevated Cl− (2140–18,800 mg/L), Na+ (1317–10,983 mg/L) and SO₄2− (440–2890 mg/L), with high electrical conductivity (7480–53,850 μS/cm in 2023 and 16,200–42,000 μS/cm in 2024). Nutrients (NO₃−, NH₄+, PO₄3−, NO₂−) and fecal indicators (Escherichia coli, Enterococci) were detected. Vertical profiles showed salinity increases with depth (except at Drac de Santanyí). The ƒsea index indicated marine intrusion in >96% of samples. Modified Piper indices (GQIPiper(mix), GQIPiper(dom)) and GQISWI values (28–56 in 2023; 32–51 in 2024) pointed to dominant to mixed NaCl facies. PCA and hierarchical clustering revealed marked hydrochemical heterogeneity among sites, with differences between 2023 and 2024 and site-specific anomalies associated with freshwater inputs and anthropogenic pressure. Overall, the results document widespread brackish to saline groundwater conditions and the co-occurrence of microbiological contamination in Mallorca's coastal aquifers, highlighting their high vulnerability to salinization and water-quality degradation.
This work presents a data-driven, site-specific conceptual model of the marine intrusion system in Mediterranean coastal aquifers, characterized by a laterally extensive brackish zone overlying saline groundwater and a limited or locally absent freshwater lens near the coast. These findings underscore the need for integrated groundwater management, including salinity monitoring, regulation of abstraction, and improved wastewater treatment, to mitigate ecological and public-health risks in Mediterranean coastal aquifer systems.
{"title":"Multivariate assessment of groundwater contamination levels associated with saline intrusion processes in Mediterranean coastal aquifers","authors":"R. Álvarez-Alonso , P.A. Robledo Ardila , S. Deudero , C.A. Melo-Aguilar , C. Alomar , F. Micheo , J.J. Durán , S. Pérez , F. Árcega Cabrera , S. Martínez Pérez","doi":"10.1016/j.jconhyd.2026.104877","DOIUrl":"10.1016/j.jconhyd.2026.104877","url":null,"abstract":"<div><div>Groundwater in Mediterranean coastal aquifers supplies a large part of the demand for freshwater but is increasingly threatened by seawater intrusion and anthropogenic pollution. During the springs of 2023 and 2024, six coastal carbonate aquifers in Mallorca were sampled to assess the present-day spatial and vertical variability of salinization and pollution. Hydrochemistry showed elevated Cl<sup>−</sup> (2140–18,800 mg/L), Na<sup>+</sup> (1317–10,983 mg/L) and SO₄<sup>2−</sup> (440–2890 mg/L), with high electrical conductivity (7480–53,850 μS/cm in 2023 and 16,200–42,000 μS/cm in 2024). Nutrients (NO₃<sup>−</sup>, NH₄<sup>+</sup>, PO₄<sup>3−</sup>, NO₂<sup>−</sup>) and fecal indicators (<em>Escherichia coli</em>, <em>Enterococci</em>) were detected. Vertical profiles showed salinity increases with depth (except at Drac de Santanyí). The ƒ<sub>sea</sub> index indicated marine intrusion in >96% of samples. Modified Piper indices (GQI<sub>Piper(mix)</sub>, GQI<sub>Piper(dom)</sub>) and GQI<sub>SWI</sub> values (28–56 in 2023; 32–51 in 2024) pointed to dominant to mixed Na<img>Cl facies. PCA and hierarchical clustering revealed marked hydrochemical heterogeneity among sites, with differences between 2023 and 2024 and site-specific anomalies associated with freshwater inputs and anthropogenic pressure. Overall, the results document widespread brackish to saline groundwater conditions and the co-occurrence of microbiological contamination in Mallorca's coastal aquifers, highlighting their high vulnerability to salinization and water-quality degradation.</div><div>This work presents a data-driven, site-specific conceptual model of the marine intrusion system in Mediterranean coastal aquifers, characterized by a laterally extensive brackish zone overlying saline groundwater and a limited or locally absent freshwater lens near the coast. These findings underscore the need for integrated groundwater management, including salinity monitoring, regulation of abstraction, and improved wastewater treatment, to mitigate ecological and public-health risks in Mediterranean coastal aquifer systems.</div></div>","PeriodicalId":15530,"journal":{"name":"Journal of contaminant hydrology","volume":"278 ","pages":"Article 104877"},"PeriodicalIF":4.4,"publicationDate":"2026-03-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"146173045","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"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 : 2026-02-01Epub Date: 2025-12-16DOI: 10.1016/j.jconhyd.2025.104815
Yandan Li , Tianxiang Xia , Dan Zhang , Danyang Zhang , Miao Li
The mechanisms of triclosan (TCS) adsorption onto polyamide (PA), polystyrene (PS), polyvinylchloride (PVC) and low-density polyethylene (LDPE) microplastics (MPs) were investigated, along with the effects of solution pH, ionic strength, and dissolved organic matter (DOM). The Linear model better described TCS adsorption isotherms suggesting that hydrophobic partitioning was the primary mechanism for TCS adsorption, while the Freundlich and Langmuir model fittings showed that TCS adsorption onto MPs was favorable. Following normalization by the specific surface area (SSA) of MPs, adsorption distribution coefficient (Kd) values of 105.70, 0.56, 0.20, and 0.08 L/m2 were determined for PA, PS, PVC, and LDPE MPs, respectively. Hydrophobic interaction was the main adsorption mechanism, although other mechanisms, governed by the specific structure and functional groups of the MPs, also contributed. These included the formation of hydrogen bonds between the –OH on TCS (H-bond-donating) and the amide groups on PA (H-bond-accepting), and the π-π interactions between the benzene rings of PS and TCS, and hydrogen bonds between -OH on TCS and –COO-/–COOH on PVC MPs. TCS adsorption by MPs was found to be pH-dependent, indicating that TCS0 was the main species involved in adsorption. The effects of ionic strength on TCS adsorption were not significant and therefore could be ignored. Humic acid (HA) impeded the adsorption of TCS by PA, PS, and LDPE MPs, potentially due to the hydrophobic interactions of HA with the three MPs, the hydrogen bonds with PA MPs, and the π-π interactions with PS MPs, all of which competed with TCS for adsorption sites. Fulvic acid (FA) inhibited TCS adsorption onto PS MPs, as FA could be sorbed by PS MPs through π-π interactions, competing with TCS for adsorption sites. These findings improve the accuracy of risk evaluations for organic pollutants such as TCS when co-occurring with MPs, furthering our understanding of the impacts of complex pollutant mixtures on both human and environmental health.
{"title":"Adsorption behavior of triclosan by different microplastics and the impact of water chemistry","authors":"Yandan Li , Tianxiang Xia , Dan Zhang , Danyang Zhang , Miao Li","doi":"10.1016/j.jconhyd.2025.104815","DOIUrl":"10.1016/j.jconhyd.2025.104815","url":null,"abstract":"<div><div>The mechanisms of triclosan (TCS) adsorption onto polyamide (PA), polystyrene (PS), polyvinylchloride (PVC) and low-density polyethylene (LDPE) microplastics (MPs) were investigated, along with the effects of solution pH, ionic strength, and dissolved organic matter (DOM). The Linear model better described TCS adsorption isotherms suggesting that hydrophobic partitioning was the primary mechanism for TCS adsorption, while the Freundlich and Langmuir model fittings showed that TCS adsorption onto MPs was favorable. Following normalization by the specific surface area (SSA) of MPs, adsorption distribution coefficient (K<sub>d</sub>) values of 105.70, 0.56, 0.20, and 0.08 L/m<sup>2</sup> were determined for PA, PS, PVC, and LDPE MPs, respectively. Hydrophobic interaction was the main adsorption mechanism, although other mechanisms, governed by the specific structure and functional groups of the MPs, also contributed. These included the formation of hydrogen bonds between the –OH on TCS (H-bond-donating) and the amide groups on PA (H-bond-accepting), and the π-π interactions between the benzene rings of PS and TCS, and hydrogen bonds between -OH on TCS and –COO<sup>-</sup>/–COOH on PVC MPs. TCS adsorption by MPs was found to be pH-dependent, indicating that TCS<sup>0</sup> was the main species involved in adsorption. The effects of ionic strength on TCS adsorption were not significant and therefore could be ignored. Humic acid (HA) impeded the adsorption of TCS by PA, PS, and LDPE MPs, potentially due to the hydrophobic interactions of HA with the three MPs, the hydrogen bonds with PA MPs, and the π-π interactions with PS MPs, all of which competed with TCS for adsorption sites. Fulvic acid (FA) inhibited TCS adsorption onto PS MPs, as FA could be sorbed by PS MPs through π-π interactions, competing with TCS for adsorption sites. These findings improve the accuracy of risk evaluations for organic pollutants such as TCS when co-occurring with MPs, furthering our understanding of the impacts of complex pollutant mixtures on both human and environmental health.</div></div>","PeriodicalId":15530,"journal":{"name":"Journal of contaminant hydrology","volume":"277 ","pages":"Article 104815"},"PeriodicalIF":4.4,"publicationDate":"2026-02-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145819491","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"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 : 2026-02-01Epub Date: 2026-01-24DOI: 10.1016/j.jconhyd.2026.104868
Bowen Wang, Sotheavuth Sin, Wilson Susanto, Shintaro Matsushita, Tetsuya Suekane
Hydrogen peroxide (H2O2)-based in situ chemical oxidation (ISCO) is a commonly applied technique for remediating groundwater contaminated by dense non-aqueous phase liquids (DNAPL) such as trichloroethylene (TCE). However, the overall remediation efficiency is often constrained by oxidant self-decomposition and gas-induced pore blockage, which hinder oxidant accessibility to contaminants. To improve the remediation performance, this study experimentally investigated three optimization strategies: follow-up water injection, chemical stabilization, and staged oxidant injection. These three strategies aim to remobilize trapped phases and restore oxidant access, directly suppress H2O2 self-decomposition by introducing a stabilizer, and reintroduce fresh oxidant to reboot the oxidation process, respectively. The pore-scale remediation processes were visualized using time-resolved three-dimensional micro-computed tomography (3D micro-CT) to quantify the spatial and temporal evolution of TCE and gas phases in porous media. Results show that the combined strategy of follow-up water injection and stabilizer achieved a significant enhancement in overall TCE remediation under 5 wt% H2O2 condition, obtaining the highest TCE removal of 78.7%. This study provides direct mechanistic evidence of how physical and chemical measures can jointly enhance oxidant delivery during the remediation process. The pore-scale insights offer guidance for optimizing oxidant management and injection strategies in groundwater environments, and highlight the need to consider gas-liquid-DNAPL interactions when designing field-scale remediation systems.
{"title":"Pore-scale optimization of H2O2-based TCE remediation using stabilizer-enhanced oxidant delivery and follow-up water injection","authors":"Bowen Wang, Sotheavuth Sin, Wilson Susanto, Shintaro Matsushita, Tetsuya Suekane","doi":"10.1016/j.jconhyd.2026.104868","DOIUrl":"10.1016/j.jconhyd.2026.104868","url":null,"abstract":"<div><div>Hydrogen peroxide (H<sub>2</sub>O<sub>2</sub>)-based in situ chemical oxidation (ISCO) is a commonly applied technique for remediating groundwater contaminated by dense non-aqueous phase liquids (DNAPL) such as trichloroethylene (TCE). However, the overall remediation efficiency is often constrained by oxidant self-decomposition and gas-induced pore blockage, which hinder oxidant accessibility to contaminants. To improve the remediation performance, this study experimentally investigated three optimization strategies: follow-up water injection, chemical stabilization, and staged oxidant injection. These three strategies aim to remobilize trapped phases and restore oxidant access, directly suppress H<sub>2</sub>O<sub>2</sub> self-decomposition by introducing a stabilizer, and reintroduce fresh oxidant to reboot the oxidation process, respectively. The pore-scale remediation processes were visualized using time-resolved three-dimensional micro-computed tomography (3D micro-CT) to quantify the spatial and temporal evolution of TCE and gas phases in porous media. Results show that the combined strategy of follow-up water injection and stabilizer achieved a significant enhancement in overall TCE remediation under 5 wt% H<sub>2</sub>O<sub>2</sub> condition, obtaining the highest TCE removal of 78.7%. This study provides direct mechanistic evidence of how physical and chemical measures can jointly enhance oxidant delivery during the remediation process. The pore-scale insights offer guidance for optimizing oxidant management and injection strategies in groundwater environments, and highlight the need to consider gas-liquid-DNAPL interactions when designing field-scale remediation systems.</div></div>","PeriodicalId":15530,"journal":{"name":"Journal of contaminant hydrology","volume":"277 ","pages":"Article 104868"},"PeriodicalIF":4.4,"publicationDate":"2026-02-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"146073936","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"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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