Pub Date : 2026-02-01Epub Date: 2025-12-15DOI: 10.1016/j.jconhyd.2025.104816
Yaguang Zhu , Kun Jia , Roger D. Beckie
Groundwater flow in coastal aquifers is influenced by density differences between freshwater and saline water, forming a complex density-dependent flow system. The relatively narrow zone where freshwater and saline water mix is the location of strong geochemical gradients, which can drive reactions. Understanding the dynamics of this mixing zone is crucial to understand the biogeochemical reactions that occur during saline intrusion. In this study, we characterized flow and dispersive mixing in a confined sand aquifer subjected to saline intrusion, using both field observations and numerical modeling. Observations from an extensive monitoring network revealed a saline wedge extending approximately 500 m inland. We simulated density-dependent flow with MIN3P and used PEST++ to estimate dispersivity and diffusion from field observations. In effect, we use salinity data to measure the dispersivity through inverse modeling. The longitudinal and transverse dispersivity were calibrated at 0.1 m and 0.001 m, respectively, while the molecular diffusion coefficient was 1.2 × 10−9 m2/s. Sensitivity analyses show that transverse dispersivity affects mixing-zone characteristics more than longitudinal dispersivity. Our results highlight the importance of accurately estimating dispersivity values to model the width of the mixing zone, which strongly controls geochemical reactions at the site. These findings provide insights into the processes driving freshwater–saline water mixing in coastal aquifers and offer guidance for future modeling studies on geochemical dynamics during saline intrusion.
{"title":"Density-dependent flow, solute transport and mixing in the Fraser River delta aquifer","authors":"Yaguang Zhu , Kun Jia , Roger D. Beckie","doi":"10.1016/j.jconhyd.2025.104816","DOIUrl":"10.1016/j.jconhyd.2025.104816","url":null,"abstract":"<div><div>Groundwater flow in coastal aquifers is influenced by density differences between freshwater and saline water, forming a complex density-dependent flow system. The relatively narrow zone where freshwater and saline water mix is the location of strong geochemical gradients, which can drive reactions. Understanding the dynamics of this mixing zone is crucial to understand the biogeochemical reactions that occur during saline intrusion. In this study, we characterized flow and dispersive mixing in a confined sand aquifer subjected to saline intrusion, using both field observations and numerical modeling. Observations from an extensive monitoring network revealed a saline wedge extending approximately 500 m inland. We simulated density-dependent flow with MIN3P and used PEST++ to estimate dispersivity and diffusion from field observations. In effect, we use salinity data to measure the dispersivity through inverse modeling. The longitudinal and transverse dispersivity were calibrated at 0.1 m and 0.001 m, respectively, while the molecular diffusion coefficient was 1.2 × 10<sup>−9</sup> m<sup>2</sup>/s. Sensitivity analyses show that transverse dispersivity affects mixing-zone characteristics more than longitudinal dispersivity. Our results highlight the importance of accurately estimating dispersivity values to model the width of the mixing zone, which strongly controls geochemical reactions at the site. These findings provide insights into the processes driving freshwater–saline water mixing in coastal aquifers and offer guidance for future modeling studies on geochemical dynamics during saline intrusion.</div></div>","PeriodicalId":15530,"journal":{"name":"Journal of contaminant hydrology","volume":"277 ","pages":"Article 104816"},"PeriodicalIF":4.4,"publicationDate":"2026-02-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145788229","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: 2026-01-14DOI: 10.1016/j.jconhyd.2026.104856
Hyeongseok Song , Kwang-Sik Lee , Nohsung Jeong , Sunghyen Cho , Dongguen Lee , Cheolho Yoon , Woo-Jin Shin
The nitrate apportionment approach provides valuable insights into efficient water quality management. Water samples were collected from the South Han River (SHR), and the three tributaries of the SHR showed relatively high nutrient levels. Water samples were collected from the North Han River (NHR), another contaminated stream (Gyeongan Stream, GA), and wastewater treatment plants (WWTP). The objectives of this study were to identify the sources impacting water chemistry in the SHR and its tributaries, especially nitrate contaminants, and to estimate the apportionment of nitrate sources. Plots of SO4/Cl and NO3/Cl showed relatively low ratios for the tributary, GA, and WWTPs samples compared to those of the SHR and NHR. Interestingly, samples from the lowest reaches of a tributary showed considerably high SO4/Cl and low NO3/Cl, with distinct δ34S values, indicating a specific contaminant source in its watershed and subsequently influencing SHR water chemistry. The contributions of each source to nitrate in SHR and tributaries were estimated to be 58.9% to 93.3% and 0.2% to 95.7% for soil N and 15.9% to 40.3% and 4.1% to 99.4% for manure/domestic sewage, respectively, using a Bayesian isotope mixing model. These source contributions were not clearly consistent with the land-use patterns. δ11B related to δ15N-NO3 values for SHR samples indicate that domestic wastewater exerts a greater influence on water chemistry than agricultural inputs. We suggest a comprehensive approach for identifying nitrate contaminants in water using multiple isotopes, including nitrate isotopes, with a Bayesian isotope mixing model.
{"title":"Nitrate source apportionments in the South Han River basin and its main tributaries using multi-isotopes and Bayesian approaches","authors":"Hyeongseok Song , Kwang-Sik Lee , Nohsung Jeong , Sunghyen Cho , Dongguen Lee , Cheolho Yoon , Woo-Jin Shin","doi":"10.1016/j.jconhyd.2026.104856","DOIUrl":"10.1016/j.jconhyd.2026.104856","url":null,"abstract":"<div><div>The nitrate apportionment approach provides valuable insights into efficient water quality management. Water samples were collected from the South Han River (SHR), and the three tributaries of the SHR showed relatively high nutrient levels. Water samples were collected from the North Han River (NHR), another contaminated stream (Gyeongan Stream, GA), and wastewater treatment plants (WWTP). The objectives of this study were to identify the sources impacting water chemistry in the SHR and its tributaries, especially nitrate contaminants, and to estimate the apportionment of nitrate sources. Plots of SO<sub>4</sub>/Cl and NO<sub>3</sub>/Cl showed relatively low ratios for the tributary, GA, and WWTPs samples compared to those of the SHR and NHR. Interestingly, samples from the lowest reaches of a tributary showed considerably high SO<sub>4</sub>/Cl and low NO<sub>3</sub>/Cl, with distinct δ<sup>34</sup>S values, indicating a specific contaminant source in its watershed and subsequently influencing SHR water chemistry. The contributions of each source to nitrate in SHR and tributaries were estimated to be 58.9% to 93.3% and 0.2% to 95.7% for soil N and 15.9% to 40.3% and 4.1% to 99.4% for manure/domestic sewage, respectively, using a Bayesian isotope mixing model. These source contributions were not clearly consistent with the land-use patterns. δ<sup>11</sup>B related to δ<sup>15</sup>N-NO<sub>3</sub> values for SHR samples indicate that domestic wastewater exerts a greater influence on water chemistry than agricultural inputs. We suggest a comprehensive approach for identifying nitrate contaminants in water using multiple isotopes, including nitrate isotopes, with a Bayesian isotope mixing model.</div></div>","PeriodicalId":15530,"journal":{"name":"Journal of contaminant hydrology","volume":"277 ","pages":"Article 104856"},"PeriodicalIF":4.4,"publicationDate":"2026-02-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"146010543","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: 2026-01-13DOI: 10.1016/j.jconhyd.2026.104854
Yefeng Ji, Lu Cao, Yun Gao, Zhongyan Huo, Zhequan Leng, Qi Chen, Zhutao Ding, Ying Xiong
Since their emergence in the 20th century, plastics have been extensively utilized worldwide. Owing to their pronounced hydrophobicity, chemical inertness, and resistance to microbial degradation, plastics persist in the environment and are difficult to eliminate. Rivers serve as an important pathway for microplastics (MPs) to flow into the ocean. The mechanisms that affect the migration, transportation and fate of MPs in rivers are not yet clear. This poses obstacles to understanding the dynamics of MPs in the ocean, determining their main aggregation areas, and conducting sampling in the ocean. Through a comprehensive series of settling experiments, this study demonstrates that the settling dynamics of MPs are significantly modulated by suspended solid concentration (SSC) and salinity gradients—factors that are particularly characteristic of estuarine transition zones at the river–ocean interface. The results indicate that SSC significantly enhance the settling velocity of MPs, with a maximum increase of 15.6%. However, this promoting effect diminishes as sediment concentration increases, and an inhibitory effect emerges under high concentrations. Conversely, elevated salinity markedly suppresses settling velocity, with a maximum reduction of 33.96%, though the magnitude of this influence gradually decreases with further increases in salinity. Based on the experimental results, a modified settling velocity model that integrates the effects of SSC and salinity was developed. Validation indicates that the model reliably predicts MPs settling velocity under a wide range of environmental conditions. This study provides a theoretical framework for advancing the understanding of MPs transport processes in estuarine and coastal environments and offers valuable insights for marine environmental management and remediation.
{"title":"The influence of sediment content and salinity in estuarine areas on the settling velocity of microplastics","authors":"Yefeng Ji, Lu Cao, Yun Gao, Zhongyan Huo, Zhequan Leng, Qi Chen, Zhutao Ding, Ying Xiong","doi":"10.1016/j.jconhyd.2026.104854","DOIUrl":"10.1016/j.jconhyd.2026.104854","url":null,"abstract":"<div><div>Since their emergence in the 20th century, plastics have been extensively utilized worldwide. Owing to their pronounced hydrophobicity, chemical inertness, and resistance to microbial degradation, plastics persist in the environment and are difficult to eliminate. Rivers serve as an important pathway for microplastics (MPs) to flow into the ocean. The mechanisms that affect the migration, transportation and fate of MPs in rivers are not yet clear. This poses obstacles to understanding the dynamics of MPs in the ocean, determining their main aggregation areas, and conducting sampling in the ocean. Through a comprehensive series of settling experiments, this study demonstrates that the settling dynamics of MPs are significantly modulated by suspended solid concentration (SSC) and salinity gradients—factors that are particularly characteristic of estuarine transition zones at the river–ocean interface. The results indicate that SSC significantly enhance the settling velocity of MPs, with a maximum increase of 15.6%. However, this promoting effect diminishes as sediment concentration increases, and an inhibitory effect emerges under high concentrations. Conversely, elevated salinity markedly suppresses settling velocity, with a maximum reduction of 33.96%, though the magnitude of this influence gradually decreases with further increases in salinity. Based on the experimental results, a modified settling velocity model that integrates the effects of SSC and salinity was developed. Validation indicates that the model reliably predicts MPs settling velocity under a wide range of environmental conditions. This study provides a theoretical framework for advancing the understanding of MPs transport processes in estuarine and coastal environments and offers valuable insights for marine environmental management and remediation.</div></div>","PeriodicalId":15530,"journal":{"name":"Journal of contaminant hydrology","volume":"277 ","pages":"Article 104854"},"PeriodicalIF":4.4,"publicationDate":"2026-02-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"146010585","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: 2026-01-08DOI: 10.1016/j.jconhyd.2026.104848
Charles E. Schaefer , Graig M. Lavorgna , David R. Lippincott , Shilai Hao , J. Conrad Pritchard , Christopher P. Higgins
Increases in perfluorinated sulfonic acid (PFSA) porewater concentrations over a 35 month duration following in situ flushing were monitored at an aqueous film-forming foam (AFFF) site using porous cup suction lysimeters within a highly instrumented test cell. Results provided evidence that perfluorooctane sulfonate (PFOS) slow desorption kinetics contributed to slow contaminant rebound in measured porewater concentrations. PFSAs in the shallow (0.23 m depth) highly PFSA-impacted soils migrated downward during the monitored post-flushing period, with short-chained PFSAs migrating more rapidly in porewater than long-chained PFSAs. Following flushing, apparent equilibrium porewater concentrations at a depth of 0.61 m below ground surface were attained within two months for perfluoropentane sulfonate (PFPeS), between 2 and 20 months for perfluorohexane sulfonate (PFHxS), and 25 months for PFOS. For PFPeS and PFHxS, apparent steady-state rebound concentrations (to 38% of their pre-flushing baseline levels, with no increasing or decreasing trend over time subsequently observed) were reasonably predicted based on an equilibrium model. PFOS rebound and ultimately vertical migration were highly impacted by non-equilibrium soil desorption. Excavation of elevated PFSAs in surface soils had no impact on PFSA porewater concentrations 0.38 m below the excavation over a 1.2 year post-excavation monitoring period. Together, these long-term rebound data highlight the potential importance of mass transfer-controlled processes for PFOS leaching, and suggest that removal of elevated PFSAs in surface soils may take years until PFSA discharges to groundwater are diminished.
{"title":"Long term rebound and transport of perfluorinated sulfonic acids (PFSAs) in the vadose zone following flushing","authors":"Charles E. Schaefer , Graig M. Lavorgna , David R. Lippincott , Shilai Hao , J. Conrad Pritchard , Christopher P. Higgins","doi":"10.1016/j.jconhyd.2026.104848","DOIUrl":"10.1016/j.jconhyd.2026.104848","url":null,"abstract":"<div><div>Increases in perfluorinated sulfonic acid (PFSA) porewater concentrations over a 35 month duration following in situ flushing were monitored at an aqueous film-forming foam (AFFF) site using porous cup suction lysimeters within a highly instrumented test cell. Results provided evidence that perfluorooctane sulfonate (PFOS) slow desorption kinetics contributed to slow contaminant rebound in measured porewater concentrations. PFSAs in the shallow (0.23 m depth) highly PFSA-impacted soils migrated downward during the monitored post-flushing period, with short-chained PFSAs migrating more rapidly in porewater than long-chained PFSAs. Following flushing, apparent equilibrium porewater concentrations at a depth of 0.61 m below ground surface were attained within two months for perfluoropentane sulfonate (PFPeS), between 2 and 20 months for perfluorohexane sulfonate (PFHxS), and 25 months for PFOS. For PFPeS and PFHxS, apparent steady-state rebound concentrations (to 38% of their pre-flushing baseline levels, with no increasing or decreasing trend over time subsequently observed) were reasonably predicted based on an equilibrium model. PFOS rebound and ultimately vertical migration were highly impacted by non-equilibrium soil desorption. Excavation of elevated PFSAs in surface soils had no impact on PFSA porewater concentrations 0.38 m below the excavation over a 1.2 year post-excavation monitoring period. Together, these long-term rebound data highlight the potential importance of mass transfer-controlled processes for PFOS leaching, and suggest that removal of elevated PFSAs in surface soils may take years until PFSA discharges to groundwater are diminished.</div></div>","PeriodicalId":15530,"journal":{"name":"Journal of contaminant hydrology","volume":"277 ","pages":"Article 104848"},"PeriodicalIF":4.4,"publicationDate":"2026-02-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145966331","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: 2026-01-19DOI: 10.1016/j.jconhyd.2026.104861
Oliver A.H. Jones , Alexander Brindle , Mikaela Sterjovski , Shadha Al-Mashari , Pacian Netherway , Phoebe Lewis , Jennifer Martin , Matthew Currell
Understanding the sources, fate, and transport of per- and polyfluoroalkyl substances (PFAS) in coastal aquifers is essential for assessing the risk to these systems. We investigated PFAS concentrations within the Quaternary Aquifer of the Mornington Peninsula, Australia. The goals were to identify the sources of any observed contamination and assess the risk to ecological receptors associated with surface water bodies that interact with the aquifer. Fifteen bores were sampled at various depths. Multiple PFAS were detected in eight bores at ng/L concentrations (maximum ∑8PFAS = 78.8 ng/L), while seven bores contained no detectable PFAS. Notable compounds included legacy perfluoroalkyl acids, such as PFOA, PFOS, and PFHxS, as well as the fluorotelomers 6:2 FTS and 6:2 diPAP. Several potential sources were identified, including two local landfills, a wastewater treatment plant, and the use of recycled water for irrigation in local agriculture. The bores with the highest total PFAS concentrations were located near the identified sources, particularly the landfills. No clear source was apparent for several PFOS-contaminated bores. Concentrations of PFOS at six bores were just above the current ecological guideline values for 99% species protection (0.00023 μg/L) but below the value for 95% species protection (0.13 μg/L). The risk to aquatic ecological receptors from contaminant discharge from groundwater into local watercourses is considered low, due to relatively low PFAS concentrations and moderate groundwater velocities; however, the combined total risk from seasonal fluxes and surface water runoff, and other discharges could be higher. Further monitoring and risk assessment are therefore recommended.
{"title":"Occurrence and transport of per- and polyfluoroalkyl substances (PFAS) within a coastal groundwater aquifer","authors":"Oliver A.H. Jones , Alexander Brindle , Mikaela Sterjovski , Shadha Al-Mashari , Pacian Netherway , Phoebe Lewis , Jennifer Martin , Matthew Currell","doi":"10.1016/j.jconhyd.2026.104861","DOIUrl":"10.1016/j.jconhyd.2026.104861","url":null,"abstract":"<div><div>Understanding the sources, fate, and transport of per- and polyfluoroalkyl substances (PFAS) in coastal aquifers is essential for assessing the risk to these systems. We investigated PFAS concentrations within the Quaternary Aquifer of the Mornington Peninsula, Australia. The goals were to identify the sources of any observed contamination and assess the risk to ecological receptors associated with surface water bodies that interact with the aquifer. Fifteen bores were sampled at various depths. Multiple PFAS were detected in eight bores at ng/L concentrations (maximum ∑<sub>8</sub>PFAS = 78.8 ng/L), while seven bores contained no detectable PFAS. Notable compounds included legacy perfluoroalkyl acids, such as PFOA, PFOS, and PFHxS, as well as the fluorotelomers 6:2 FTS and 6:2 diPAP. Several potential sources were identified, including two local landfills, a wastewater treatment plant, and the use of recycled water for irrigation in local agriculture. The bores with the highest total PFAS concentrations were located near the identified sources, particularly the landfills. No clear source was apparent for several PFOS-contaminated bores. Concentrations of PFOS at six bores were just above the current ecological guideline values for 99% species protection (0.00023 μg/L) but below the value for 95% species protection (0.13 μg/L). The risk to aquatic ecological receptors from contaminant discharge from groundwater into local watercourses is considered low, due to relatively low PFAS concentrations and moderate groundwater velocities; however, the combined total risk from seasonal fluxes and surface water runoff, and other discharges could be higher. Further monitoring and risk assessment are therefore recommended.</div></div>","PeriodicalId":15530,"journal":{"name":"Journal of contaminant hydrology","volume":"277 ","pages":"Article 104861"},"PeriodicalIF":4.4,"publicationDate":"2026-02-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"146022905","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: 2026-01-25DOI: 10.1016/j.jconhyd.2026.104870
Chunlu Jiang , Yuqun Zhang , Qianqian Wang
Groundwater discharge and associated dissolved carbon fluxes are essential parameters in wetland ecosystems of coal mining subsidence lakes. Previous studies have shown that groundwater discharge considerably contributes to isolated coal mining subsidence lakes. However, groundwater discharge and associated dissolved inorganic carbon (DIC) flux into open-type subsidence lakes remain poorly understood. In this study, radioactive (222Rn) and stable water isotopes (18O) were used as tracers to establish isotope mass balance models, and to quantify groundwater discharge into an open-type coal mining subsidence lake. The results showed that the estimated lacustrine groundwater discharge (LGD) rates using the 222Rn and 18O mass balance models were 38.54 ± 21.05 mm/d and 27.89 ± 3.53 mm/d, respectively, which accounted for 15.56% and 12.30% of the total source of lake water. On this basis, combined with a DIC end-member mixing model and CO2 diffusion model, DIC flux from LGD was 70.33 ± 1.41 mmol/(m2·d), accounting for 19.10% of the total lake DIC inventory and 65.60% of the total CO2 evasion from the lake. The results suggest that CO2 escape from freshwater lakes may be an important source of atmospheric carbon, which should be included in the carbon budget of lake budgets. The results provide a theoretical basis for accurate assessment of groundwater discharge and the carbon budget in open-type subsidence lakes. This is important for local water environment protection and the utilization of water resources.
{"title":"Groundwater discharge and dissolved inorganic carbon flux into an open-type coal mining subsidence lake in eastern China","authors":"Chunlu Jiang , Yuqun Zhang , Qianqian Wang","doi":"10.1016/j.jconhyd.2026.104870","DOIUrl":"10.1016/j.jconhyd.2026.104870","url":null,"abstract":"<div><div>Groundwater discharge and associated dissolved carbon fluxes are essential parameters in wetland ecosystems of coal mining subsidence lakes. Previous studies have shown that groundwater discharge considerably contributes to isolated coal mining subsidence lakes. However, groundwater discharge and associated dissolved inorganic carbon (DIC) flux into open-type subsidence lakes remain poorly understood. In this study, radioactive (<sup>222</sup>Rn) and stable water isotopes (<sup>18</sup>O) were used as tracers to establish isotope mass balance models, and to quantify groundwater discharge into an open-type coal mining subsidence lake. The results showed that the estimated lacustrine groundwater discharge (LGD) rates using the <sup>222</sup>Rn and <sup>18</sup>O mass balance models were 38.54 ± 21.05 mm/d and 27.89 ± 3.53 mm/d, respectively, which accounted for 15.56% and 12.30% of the total source of lake water. On this basis, combined with a DIC end-member mixing model and CO<sub>2</sub> diffusion model, DIC flux from LGD was 70.33 ± 1.41 mmol/(m<sup>2</sup>·d), accounting for 19.10% of the total lake DIC inventory and 65.60% of the total CO<sub>2</sub> evasion from the lake. The results suggest that CO<sub>2</sub> escape from freshwater lakes may be an important source of atmospheric carbon, which should be included in the carbon budget of lake budgets. The results provide a theoretical basis for accurate assessment of groundwater discharge and the carbon budget in open-type subsidence lakes. This is important for local water environment protection and the utilization of water resources.</div></div>","PeriodicalId":15530,"journal":{"name":"Journal of contaminant hydrology","volume":"277 ","pages":"Article 104870"},"PeriodicalIF":4.4,"publicationDate":"2026-02-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"146073935","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: 2026-01-25DOI: 10.1016/j.jconhyd.2026.104871
Youxiao Wang , Zhaomin Zhang , Zhonghe Zhao , He Li , Yingjun Sun , Chong Huang , Banghua Zhang , Gaohuan Liu
China has been confronted with severe agricultural nonpoint source pollution (AGNSP) from livestock and poultry, which increases chemical oxygen demand (COD). To explore the sources of COD in surface waters from the perspective of ecosystem processes, taking the coastal watershed of the Yellow River Delta (YRD) of China as a typical study area, we have adopted a method that integrates the scale and positioning of livestock and poultry breeding, a pollutant generation coefficient, and kernel density estimation (KDE) to assess the COD diffusion risk during watershed soil erosion processes. Moreover, verification and analysis were performed by combining soil sampling data with hydrological and water quality monitoring data for the estuary. Additionally, we selected Spearman's coefficient for correlation analysis between surface soil organic matter (SOM) and related natural-anthropogenic factors. The main conclusions are as follows: the terrestrial COD pollution risks generated by livestock and poultry significantly influence SOM (p < 0.001) and are most strongly correlated in non-arable lands, especially saline-alkali land (rs = 0.86) mainly because of natural soil erosion process. Arable land has the highest SOM concentrations but has lower correlations with the COD generation risks obtained by the KDE method, mainly because of cultivation activities. At the watershed scale, surface runoff is the dominant driver of estuarine COD fluxes but has certain dilution effects on COD concentrations. Furthermore, there usually exists the spillover effects of AGNSP from livestock and poultry usually occur due to the imbalanced distributions between the area of arable land and the supply of manure within watersheds. Our study provides an effective and rapid assessment method for determining the AGNSP risk of COD derived from livestock and poultry.
{"title":"Tracing coastal nonpoint sources of agricultural organic pollution based on soil sequestration and retention processes: A case study of the Yellow River Delta, China","authors":"Youxiao Wang , Zhaomin Zhang , Zhonghe Zhao , He Li , Yingjun Sun , Chong Huang , Banghua Zhang , Gaohuan Liu","doi":"10.1016/j.jconhyd.2026.104871","DOIUrl":"10.1016/j.jconhyd.2026.104871","url":null,"abstract":"<div><div>China has been confronted with severe agricultural nonpoint source pollution (AGNSP) from livestock and poultry, which increases chemical oxygen demand (COD). To explore the sources of COD in surface waters from the perspective of ecosystem processes, taking the coastal watershed of the Yellow River Delta (YRD) of China as a typical study area, we have adopted a method that integrates the scale and positioning of livestock and poultry breeding, a pollutant generation coefficient, and kernel density estimation (KDE) to assess the COD diffusion risk during watershed soil erosion processes. Moreover, verification and analysis were performed by combining soil sampling data with hydrological and water quality monitoring data for the estuary. Additionally, we selected <em>Spearman's</em> coefficient for correlation analysis between surface soil organic matter (SOM) and related natural-anthropogenic factors. The main conclusions are as follows: the terrestrial COD pollution risks generated by livestock and poultry significantly influence SOM (<em>p</em> < 0.001) and are most strongly correlated in non-arable lands, especially saline-alkali land (<em>r</em><sub><em>s</em></sub> = 0.86) mainly because of natural soil erosion process. Arable land has the highest SOM concentrations but has lower correlations with the COD generation risks obtained by the KDE method, mainly because of cultivation activities. At the watershed scale, surface runoff is the dominant driver of estuarine COD fluxes but has certain dilution effects on COD concentrations. Furthermore, there usually exists the spillover effects of AGNSP from livestock and poultry usually occur due to the imbalanced distributions between the area of arable land and the supply of manure within watersheds. Our study provides an effective and rapid assessment method for determining the AGNSP risk of COD derived from livestock and poultry.</div></div>","PeriodicalId":15530,"journal":{"name":"Journal of contaminant hydrology","volume":"277 ","pages":"Article 104871"},"PeriodicalIF":4.4,"publicationDate":"2026-02-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"146073937","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: 2026-01-20DOI: 10.1016/j.jconhyd.2026.104865
Yuta Fukatsu , Tomomi Oguri , Takafumi Hamamoto , Keisuke Ishida , Andrew Martin , Yukio Tachi
For long-term safety assessments of deep geological disposal, evaluating effective diffusion coefficients (De) and distribution coefficients (Kd) under in-situ conditions remains a critical yet challenging task due to practical limitations. This study aims to establish a methodology for evaluating these parameters under realistic geological conditions through an integrated analysis of a long-term in-situ diffusion (LTD-II) experiment and complementary laboratory through-diffusion experiments in Grimsel granodiorite. The proposed approach combines (i) post analysis of cored samples to characterize spatial variations in pore connectivity and anisotropic transport, (ii) numerical modeling that accounts for the borehole disturbed zone (BDZ), and (iii) laboratory diffusion experiments to verify the consistency and reliability of in-situ parameter estimation.
The modeling reproduced both the depletion curves and the tracer concentration profiles observed in the LTD-II experiment, particularly the sharp gradients within a few millimeters from the injection hole, which were attributed to BDZ. The derived De and Kd values for sorbing tracers (Na+, Cs+, and Ba2+) were consistent between laboratory and in-situ conditions for transport distances up to several centimeters, confirming the reliability of the parameter derivation approach for sorbing species over short distances. In contrast, non-sorbing tracers (HTO and 36Cl−) exhibited depth-dependent concentration variations extending ∼50 cm from the injection hole. The De values of non-sorbing tracers were two to three times higher than those obtained in laboratory tests, yet remained within the same order of magnitude. These variations of non-sorbing tracers could be qualitatively explained by anisotropic transport along foliation and minor advection over several tens of centimeters, highlighting the importance of accounting for local structural and hydraulic variations when interpreting in-situ diffusion data.
These results demonstrate that integrating in-situ diffusion data with laboratory verification and spatial profiling provides a methodology for deriving diffusion and sorption parameters representative of in-situ conditions, and clarifies the practical limitations and applicable range of transport modeling in crystalline rocks.
{"title":"Methodology for evaluating matrix diffusion and sorption parameters in crystalline rocks: Application to laboratory and in-situ diffusion experiments at the Grimsel Test Site","authors":"Yuta Fukatsu , Tomomi Oguri , Takafumi Hamamoto , Keisuke Ishida , Andrew Martin , Yukio Tachi","doi":"10.1016/j.jconhyd.2026.104865","DOIUrl":"10.1016/j.jconhyd.2026.104865","url":null,"abstract":"<div><div>For long-term safety assessments of deep geological disposal, evaluating effective diffusion coefficients (<em>D</em><sub>e</sub>) and distribution coefficients (<em>K</em><sub>d</sub>) under in-situ conditions remains a critical yet challenging task due to practical limitations. This study aims to establish a methodology for evaluating these parameters under realistic geological conditions through an integrated analysis of a long-term in-situ diffusion (LTD-II) experiment and complementary laboratory through-diffusion experiments in Grimsel granodiorite. The proposed approach combines (i) post analysis of cored samples to characterize spatial variations in pore connectivity and anisotropic transport, (ii) numerical modeling that accounts for the borehole disturbed zone (BDZ), and (iii) laboratory diffusion experiments to verify the consistency and reliability of in-situ parameter estimation.</div><div>The modeling reproduced both the depletion curves and the tracer concentration profiles observed in the LTD-II experiment, particularly the sharp gradients within a few millimeters from the injection hole, which were attributed to BDZ. The derived <em>D</em><sub>e</sub> and <em>K</em><sub>d</sub> values for sorbing tracers (Na<sup>+</sup>, Cs<sup>+</sup>, and Ba<sup>2+</sup>) were consistent between laboratory and in-situ conditions for transport distances up to several centimeters, confirming the reliability of the parameter derivation approach for sorbing species over short distances. In contrast, non-sorbing tracers (HTO and <sup>36</sup>Cl<sup>−</sup>) exhibited depth-dependent concentration variations extending ∼50 cm from the injection hole. The <em>D</em><sub>e</sub> values of non-sorbing tracers were two to three times higher than those obtained in laboratory tests, yet remained within the same order of magnitude. These variations of non-sorbing tracers could be qualitatively explained by anisotropic transport along foliation and minor advection over several tens of centimeters, highlighting the importance of accounting for local structural and hydraulic variations when interpreting in-situ diffusion data.</div><div>These results demonstrate that integrating in-situ diffusion data with laboratory verification and spatial profiling provides a methodology for deriving diffusion and sorption parameters representative of in-situ conditions, and clarifies the practical limitations and applicable range of transport modeling in crystalline rocks.</div></div>","PeriodicalId":15530,"journal":{"name":"Journal of contaminant hydrology","volume":"277 ","pages":"Article 104865"},"PeriodicalIF":4.4,"publicationDate":"2026-02-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"146073940","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: 2026-01-05DOI: 10.1016/j.jconhyd.2026.104844
Xi Jiang , Youxi Cai , Hanwen Deng , Xiaolei Li
Microplastics (MPs) originating from plastic waste in groundwater have attracted much attention worldwide due to their wide distribution, small particle size and high mobility, as well as their potential threat to organisms. In this study, a magnetically modified biochar adsorbent for the removal of microplastics was prepared using KOH-activated industrial hemp straw biochar as a precursor. For polystyrene (PS) microspheres (1 μm, 60 mg/L) in aqueous solution, magnetic biochar (MBC) removed 89.97 %, which was 9.30 times higher removal rate compared to pristine biochar (BC). It is hypothesized that the adsorption process was a result of electrostatic interactions and chemical bonding interactions between microplastics and biochar. The adsorption process was affected by solution pH and interfering ions, and the MBC had good stability, and its removal efficiency of MPs remained above 80 % after 5 cycles. Kinetic, isothermal and thermodynamic modeling analyses showed that the adsorption reaction was spontaneous, higher temperature contributed to the enhancement of adsorption, and the adsorption mechanism involved electrostatic interactions, surface complexation, metal-O-MPs complexation and π-π interactions. These results would provide an idea for obtaining MBC to remove the MPs from aqueous systems.
来源于地下水中塑料垃圾的微塑料因其分布广泛、粒径小、流动性强以及对生物的潜在威胁而受到世界各国的广泛关注。本研究以koh活化的工业大麻秸秆生物炭为前驱体，制备了一种用于去除微塑料的磁性改性生物炭吸附剂。磁性生物炭（MBC）对聚苯乙烯（PS）微球（1 μm, 60 mg/L）的去除率为89.97%，是原始生物炭（BC）的9.30倍。假设吸附过程是微塑料与生物炭之间静电相互作用和化学键相互作用的结果。吸附过程受溶液pH和干扰离子的影响，MBC具有良好的稳定性，循环5次后对MPs的去除率保持在80%以上。动力学、等温和热力学模型分析表明，吸附反应是自发的，温度升高有助于吸附的增强，吸附机理涉及静电相互作用、表面络合作用、金属- o - mps络合作用和π-π相互作用。这些结果将为获得从水体系中去除MPs的MBC提供思路。
{"title":"Adsorption and mechanism of magnetically modified industrial hemp straw biochar on microplastics in aqueous solution","authors":"Xi Jiang , Youxi Cai , Hanwen Deng , Xiaolei Li","doi":"10.1016/j.jconhyd.2026.104844","DOIUrl":"10.1016/j.jconhyd.2026.104844","url":null,"abstract":"<div><div>Microplastics (MPs) originating from plastic waste in groundwater have attracted much attention worldwide due to their wide distribution, small particle size and high mobility, as well as their potential threat to organisms. In this study, a magnetically modified biochar adsorbent for the removal of microplastics was prepared using KOH-activated industrial hemp straw biochar as a precursor. For polystyrene (PS) microspheres (1 μm, 60 mg/L) in aqueous solution, magnetic biochar (MBC) removed 89.97 %, which was 9.30 times higher removal rate compared to pristine biochar (BC). It is hypothesized that the adsorption process was a result of electrostatic interactions and chemical bonding interactions between microplastics and biochar. The adsorption process was affected by solution pH and interfering ions, and the MBC had good stability, and its removal efficiency of MPs remained above 80 % after 5 cycles. Kinetic, isothermal and thermodynamic modeling analyses showed that the adsorption reaction was spontaneous, higher temperature contributed to the enhancement of adsorption, and the adsorption mechanism involved electrostatic interactions, surface complexation, metal-O-MPs complexation and π-π interactions. These results would provide an idea for obtaining MBC to remove the MPs from aqueous systems.</div></div>","PeriodicalId":15530,"journal":{"name":"Journal of contaminant hydrology","volume":"277 ","pages":"Article 104844"},"PeriodicalIF":4.4,"publicationDate":"2026-02-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145917635","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: 2025-12-29DOI: 10.1016/j.jconhyd.2025.104836
Hansell Gonzalez-Raymat , Miles E. Denham , Haruko M. Wainwright , Holly H. VerMeulen , Nathaniel A. Losey , Jeffrey Thibault , Kevin Boerstler , Austin Coleman , Jordan Floyd , Brady D. Lee , Ravi Gudavalli , Carol A. Eddy-Dilek
Wetlands are dynamic ecosystems that can immobilize contaminants for extended periods but can also release them when hydrological and/or biogeochemical conditions change. Although this behavior is well recognized, the field-scale processes controlling the retention and release of certain contaminants such as iodine-129 (129I) remain poorly understood, particularly in a contaminated wetland at the U.S. Department of Energy's Savannah River Site. In this study, we hypothesized that seasonal variations in groundwater flux regulate 129I behavior by altering the biogeochemistry of the wetland seeps and underlying sediments. To test this hypothesis, we combined soil and water sampling, microbial analysis, iodine speciation, and autonomous sensor monitoring. Our results show that 129I is preferentially retained in the organic-rich surface soil, with concentrations peaking at 0.22 Bq g−1 within the upper 0.15 m followed by a decrease with depth. Pronounced seasonal fluctuations in 129I concentrations were observed in surface water, increasing from 0.9–2 Bq L−1 in winter to 3–8 Bq L−1 in summer, while groundwater concentrations remained consistently lower (0.2–0.6 Bq L−1) and exhibited minimal seasonal variability. These variations correspond to seasonal changes in groundwater flux towards the seeps: higher flux during winter flushes the seeps causing 129I concentrations in surface water to be close to groundwater concentrations, while reduced flux during summer promotes stagnant and anoxic conditions that facilitate the release of bound 129I from the organic-rich soil into surface water. Iodine speciation analysis indicates that 78 to 99 % of total iodine in surface water existed as organoiodine, suggesting organic matter degradation drives 129I remobilization. These observations were integrated into a field-scale conceptual site model, linking hydrological and biogeochemical processes to the retention and release of 129I occurring in the wetlands.
{"title":"Seasonal behavior of iodine-129 in a contaminated wetland: A field-scale conceptual site model from the Savannah River Site","authors":"Hansell Gonzalez-Raymat , Miles E. Denham , Haruko M. Wainwright , Holly H. VerMeulen , Nathaniel A. Losey , Jeffrey Thibault , Kevin Boerstler , Austin Coleman , Jordan Floyd , Brady D. Lee , Ravi Gudavalli , Carol A. Eddy-Dilek","doi":"10.1016/j.jconhyd.2025.104836","DOIUrl":"10.1016/j.jconhyd.2025.104836","url":null,"abstract":"<div><div>Wetlands are dynamic ecosystems that can immobilize contaminants for extended periods but can also release them when hydrological and/or biogeochemical conditions change. Although this behavior is well recognized, the field-scale processes controlling the retention and release of certain contaminants such as iodine-129 (<sup>129</sup>I) remain poorly understood, particularly in a contaminated wetland at the U.S. Department of Energy's Savannah River Site. In this study, we hypothesized that seasonal variations in groundwater flux regulate <sup>129</sup>I behavior by altering the biogeochemistry of the wetland seeps and underlying sediments. To test this hypothesis, we combined soil and water sampling, microbial analysis, iodine speciation, and autonomous sensor monitoring. Our results show that <sup>129</sup>I is preferentially retained in the organic-rich surface soil, with concentrations peaking at 0.22 Bq g<sup>−1</sup> within the upper 0.15 m followed by a decrease with depth. Pronounced seasonal fluctuations in <sup>129</sup>I concentrations were observed in surface water, increasing from 0.9–2 Bq L<sup>−1</sup> in winter to 3–8 Bq L<sup>−1</sup> in summer, while groundwater concentrations remained consistently lower (0.2–0.6 Bq L<sup>−1</sup>) and exhibited minimal seasonal variability. These variations correspond to seasonal changes in groundwater flux towards the seeps: higher flux during winter flushes the seeps causing <sup>129</sup>I concentrations in surface water to be close to groundwater concentrations, while reduced flux during summer promotes stagnant and anoxic conditions that facilitate the release of bound <sup>129</sup>I from the organic-rich soil into surface water. Iodine speciation analysis indicates that 78 to 99 % of total iodine in surface water existed as organoiodine, suggesting organic matter degradation drives <sup>129</sup>I remobilization. These observations were integrated into a field-scale conceptual site model, linking hydrological and biogeochemical processes to the retention and release of <sup>129</sup>I occurring in the wetlands.</div></div>","PeriodicalId":15530,"journal":{"name":"Journal of contaminant hydrology","volume":"277 ","pages":"Article 104836"},"PeriodicalIF":4.4,"publicationDate":"2026-02-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145917551","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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