This study evaluated the performance of electrokinetic remediation on multi-metal-contaminated soil based on three electrode configurations: linear (1 anode–2 cathodes), trigonal (1 anode–2 cathodes), and square (1 anode–4 cathodes). The effects of co-contaminants and inter-ionic interferences on metal migration and removal were critically assessed. The findings revealed that the square configuration exhibited better removal efficiencies due to its improved electric field distribution and higher cathode coverage. With the same number of electrodes, the linear arrangement exhibited slightly better removal than the trigonal design, suggesting that spatial arrangement is a key factor in EK performance. The maximum removal was achieved for hexavalent chromium (Cr (VI)), followed by cadmium and lead, mainly because of the high complexation affinity of Cr (VI) for EDTA. Speciation analysis by Visual MINTEQ showed evidence of stable Cr–EDTA complexes being formed, allowing their mobilization. Introduction of EDTA not only enhanced the transport and solubility of target metals but also favoured the migration of natural cations (Na+, K+, Mg2+, Ca2+). In addition, harmful anions, SO42− and Cl− were reduced by 90 % and 80 %, respectively. The economic analysis confirmed the square configuration as the most cost-effective, with specific energy consumption (50 kWh/m3/g) and specific cost (701.5 US$/g). The study highlights the critical role of electrode arrangement in optimizing EKR processes and the mobilization and removal of heavy metals from polluted soils.
{"title":"Effects of electrode geometry on electrokinetic removal of heavy metals and salt ions from co-contaminated soils","authors":"Öznur Karaca , Sonam Taneja , Çetin Kantar , Anil Kumar Haritash","doi":"10.1016/j.apgeochem.2025.106655","DOIUrl":"10.1016/j.apgeochem.2025.106655","url":null,"abstract":"<div><div>This study evaluated the performance of electrokinetic remediation on multi-metal-contaminated soil based on three electrode configurations: linear (1 anode–2 cathodes), trigonal (1 anode–2 cathodes), and square (1 anode–4 cathodes). The effects of co-contaminants and inter-ionic interferences on metal migration and removal were critically assessed. The findings revealed that the square configuration exhibited better removal efficiencies due to its improved electric field distribution and higher cathode coverage. With the same number of electrodes, the linear arrangement exhibited slightly better removal than the trigonal design, suggesting that spatial arrangement is a key factor in EK performance. The maximum removal was achieved for hexavalent chromium (Cr (VI)), followed by cadmium and lead, mainly because of the high complexation affinity of Cr (VI) for EDTA. Speciation analysis by Visual MINTEQ showed evidence of stable Cr–EDTA complexes being formed, allowing their mobilization. Introduction of EDTA not only enhanced the transport and solubility of target metals but also favoured the migration of natural cations (Na<sup>+</sup>, K<sup>+</sup>, Mg<sup>2+</sup>, Ca<sup>2+</sup>). In addition, harmful anions, SO<sub>4</sub><sup>2−</sup> and Cl<sup>−</sup> were reduced by 90 % and 80 %, respectively. The economic analysis confirmed the square configuration as the most cost-effective, with specific energy consumption (50 kWh/m<sup>3</sup>/g) and specific cost (701.5 US$/g). The study highlights the critical role of electrode arrangement in optimizing EKR processes and the mobilization and removal of heavy metals from polluted soils.</div></div>","PeriodicalId":8064,"journal":{"name":"Applied Geochemistry","volume":"197 ","pages":"Article 106655"},"PeriodicalIF":3.4,"publicationDate":"2025-12-16","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145789480","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2025-12-15DOI: 10.1016/j.apgeochem.2025.106656
Xiuying Yang , Hongbing Tan , Zhiwei Shi , Hongkai Zhu , Kang Qiang , Hao Long
The Gudui geothermal field in southern Tibet, China's second-largest non-volcanic high-temperature geothermal system, exhibits vigorous hydrothermal activity, with widespread geothermal springs discharging harmful elements that threaten around environment. However, the enrichment and migration mechanisms of hazardous elements during geothermal spring discharge remain unclear, in particular, the unusual enriched and highly hazardous elements like Tl has not been drawn attention by previous researches. This study focuses on a high-temperature geothermal spring discharge area in Karugou watershed in Gudui and systematically track the distribution and partition law of As, Tl, and B in geothermal deposits, river water, sediments, and around farmland soils. Results indicate that concentrations of As, Tl, and B progressively increase along the river, with corresponding trends observed in sediments. Concentration of these elements exceed basic permission limits by 302.22, 1326.61 and 15.16 times, respectively. In farmland soils irrigated with river water, As and Tl levels at 40 cm depth exceed natural soil by 1.2 times, while surface B concentrations are over 4.2 times. Harmful elements from geothermal discharge exhibit systematic migration-distribution-partition patterns in geothermal deposits, river sediments, and soils, where elements first accumulate in geothermal deposits, with partial partitioning into travertine or sinter. With respect to As and B that enrich more in general travertine, Tl prefers to be enriched in sinter. Irrigation has distinctly introduced these elements into downstream farmland soils (0–40 cm). Such high enrichment poses significant potential environmental risks. Future geological events like tectonic activities, floods, or large-scale development could trigger massive release of these harmful elements from geothermal fluids or remobilization from river sediments, potentially endangering downstream populated areas. This study firstly highlights the uncommon natural hazardous elements like Tl enriched in geothermal spring and provides a reference for environmental impact assessments of geothermal exploitation in Tibet as well as worldwide.
{"title":"Unique migration-distribution processes and pollution risks of typical elements from geothermal spring discharge: A systematic assessment on Gudui geothermal field (southern Tibet)","authors":"Xiuying Yang , Hongbing Tan , Zhiwei Shi , Hongkai Zhu , Kang Qiang , Hao Long","doi":"10.1016/j.apgeochem.2025.106656","DOIUrl":"10.1016/j.apgeochem.2025.106656","url":null,"abstract":"<div><div>The Gudui geothermal field in southern Tibet, China's second-largest non-volcanic high-temperature geothermal system, exhibits vigorous hydrothermal activity, with widespread geothermal springs discharging harmful elements that threaten around environment. However, the enrichment and migration mechanisms of hazardous elements during geothermal spring discharge remain unclear, in particular, the unusual enriched and highly hazardous elements like Tl has not been drawn attention by previous researches. This study focuses on a high-temperature geothermal spring discharge area in Karugou watershed in Gudui and systematically track the distribution and partition law of As, Tl, and B in geothermal deposits, river water, sediments, and around farmland soils. Results indicate that concentrations of As, Tl, and B progressively increase along the river, with corresponding trends observed in sediments. Concentration of these elements exceed basic permission limits by 302.22, 1326.61 and 15.16 times, respectively. In farmland soils irrigated with river water, As and Tl levels at 40 cm depth exceed natural soil by 1.2 times, while surface B concentrations are over 4.2 times. Harmful elements from geothermal discharge exhibit systematic migration-distribution-partition patterns in geothermal deposits, river sediments, and soils, where elements first accumulate in geothermal deposits, with partial partitioning into travertine or sinter. With respect to As and B that enrich more in general travertine, Tl prefers to be enriched in sinter. Irrigation has distinctly introduced these elements into downstream farmland soils (0–40 cm). Such high enrichment poses significant potential environmental risks. Future geological events like tectonic activities, floods, or large-scale development could trigger massive release of these harmful elements from geothermal fluids or remobilization from river sediments, potentially endangering downstream populated areas. This study firstly highlights the uncommon natural hazardous elements like Tl enriched in geothermal spring and provides a reference for environmental impact assessments of geothermal exploitation in Tibet as well as worldwide.</div></div>","PeriodicalId":8064,"journal":{"name":"Applied Geochemistry","volume":"197 ","pages":"Article 106656"},"PeriodicalIF":3.4,"publicationDate":"2025-12-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145789481","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2025-12-13DOI: 10.1016/j.apgeochem.2025.106653
Junkun Yan , Jingjing Hu , Lingyi Li , Wei Cheng
Aluminum (Al) substitution for Fe(III) in iron (oxyhydr)oxides is a widespread phenomenon that significantly modifies the minerals' physicochemical structural properties and reactivity, thereby influencing the environmental behavior of contaminants. Despite the importance of Al-substituted iron (oxyhydr)oxides in geochemical processes, a comprehensive analysis of their structural properties and reactivity has been lacking. This review critically examines the effects of Al substitution on iron (oxyhydr)oxide crystal structure, morphology, surface charge, hydroxyl group characteristics, and recrystallization dynamics. We then elucidate how these structural alterations modulate the adsorption capacity for key environmental contaminants (heavy metals, metalloids, organic compounds, inorganic anions) and influence redox and catalytic processes crucial for contaminant transformation. This work provides essential insights for predicting contaminant behavior in diverse geological settings and inform the design of tailored remediation technologies. Future research directions are proposed to advance understanding of Al-substituted iron (oxyhydr)oxides in critical environmental processes.
{"title":"A review of Al substitution on the structures and properties of iron (oxyhydr)oxides and their environmental implications","authors":"Junkun Yan , Jingjing Hu , Lingyi Li , Wei Cheng","doi":"10.1016/j.apgeochem.2025.106653","DOIUrl":"10.1016/j.apgeochem.2025.106653","url":null,"abstract":"<div><div>Aluminum (Al) substitution for Fe(III) in iron (oxyhydr)oxides is a widespread phenomenon that significantly modifies the minerals' physicochemical structural properties and reactivity, thereby influencing the environmental behavior of contaminants. Despite the importance of Al-substituted iron (oxyhydr)oxides in geochemical processes, a comprehensive analysis of their structural properties and reactivity has been lacking. This review critically examines the effects of Al substitution on iron (oxyhydr)oxide crystal structure, morphology, surface charge, hydroxyl group characteristics, and recrystallization dynamics. We then elucidate how these structural alterations modulate the adsorption capacity for key environmental contaminants (heavy metals, metalloids, organic compounds, inorganic anions) and influence redox and catalytic processes crucial for contaminant transformation. This work provides essential insights for predicting contaminant behavior in diverse geological settings and inform the design of tailored remediation technologies. Future research directions are proposed to advance understanding of Al-substituted iron (oxyhydr)oxides in critical environmental processes.</div></div>","PeriodicalId":8064,"journal":{"name":"Applied Geochemistry","volume":"197 ","pages":"Article 106653"},"PeriodicalIF":3.4,"publicationDate":"2025-12-13","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145789479","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2025-12-13DOI: 10.1016/j.apgeochem.2025.106654
Jin Ma , Thomas Gimmi , Paul Wersin , Daniel Traber , Michael Schnellmann
Analysing and modelling profiles of natural tracers in rock porewater contribute substantially to the understanding of palaeo-transport processes in clay rocks. Following a recent deep-drilling campaign in northern Switzerland, a large dataset from eight boreholes has become available. It reveals detailed rock and porewater characterisation and provides insights into the investigated 600-700 m-thick Mesozoic succession, which includes a large central aquitard sequence with more than 100 m thick Opalinus Clay. The aquitard sequence is sandwiched between the Malm aquifer (towards the east) or the Hauptrogenstein aquifer (HRS, towards the west) at the top and the Keuper or Muschelkalk aquifers at the base. This study aimed to model and reproduce the high-resolution profiles of four different natural tracers (δ18O, δ2H, Cl−, and Br−) from these boreholes using a one-dimensional transport model. The model incorporated diffusion properties dependent on temperature, clay-mineral content, and formation-specific anion-accessible porosities. Good agreements were found between the modelled and measured profiles considering diffusive transport and consistent evolution times (i.e., times when groundwater composition changed) for all four tracers. These times were estimated individually for each borehole, suggesting values between 0.1 and 0.7 Ma for the Keuper aquifer, longer times (mostly several Ma, range of 0.6–3 Ma) for the Malm aquifer, and shortest times (mostly less than 150 ka, range of 0.02–0.3 Ma) for the Muschelkalk aquifer. These estimates are broadly consistent with the current knowledge on the palaeo-hydrogeology of the studied region. Extensive sensitivity analyses were performed to assess the impact of various modelling assumptions and simplifications on the fitting quality and estimated evolution times. Variations with regard to assumed initial conditions (within plausible ranges) and palaeo temperatures had only minor effects, while variations of diffusion coefficients or positions of conductive zones can affect local profile shapes and thus evolution times. Finally, no evidence of potential cross-formation flow between the overlying and underlying aquifers (Malm and Keuper) could be identified from simulations including advective transport.
{"title":"Modelling transport of natural tracers through a Mesozoic aquitard sequence in northern Switzerland","authors":"Jin Ma , Thomas Gimmi , Paul Wersin , Daniel Traber , Michael Schnellmann","doi":"10.1016/j.apgeochem.2025.106654","DOIUrl":"10.1016/j.apgeochem.2025.106654","url":null,"abstract":"<div><div>Analysing and modelling profiles of natural tracers in rock porewater contribute substantially to the understanding of palaeo-transport processes in clay rocks. Following a recent deep-drilling campaign in northern Switzerland, a large dataset from eight boreholes has become available. It reveals detailed rock and porewater characterisation and provides insights into the investigated 600-700 m-thick Mesozoic succession, which includes a large central aquitard sequence with more than 100 m thick Opalinus Clay. The aquitard sequence is sandwiched between the Malm aquifer (towards the east) or the Hauptrogenstein aquifer (HRS, towards the west) at the top and the Keuper or Muschelkalk aquifers at the base. This study aimed to model and reproduce the high-resolution profiles of four different natural tracers (δ<sup>18</sup>O, δ<sup>2</sup>H, Cl<sup>−</sup>, and Br<sup>−</sup>) from these boreholes using a one-dimensional transport model. The model incorporated diffusion properties dependent on temperature, clay-mineral content, and formation-specific anion-accessible porosities. Good agreements were found between the modelled and measured profiles considering diffusive transport and consistent evolution times (i.e., times when groundwater composition changed) for all four tracers. These times were estimated individually for each borehole, suggesting values between 0.1 and 0.7 Ma for the Keuper aquifer, longer times (mostly several Ma, range of 0.6–3 Ma) for the Malm aquifer, and shortest times (mostly less than 150 ka, range of 0.02–0.3 Ma) for the Muschelkalk aquifer. These estimates are broadly consistent with the current knowledge on the palaeo-hydrogeology of the studied region. Extensive sensitivity analyses were performed to assess the impact of various modelling assumptions and simplifications on the fitting quality and estimated evolution times. Variations with regard to assumed initial conditions (within plausible ranges) and palaeo temperatures had only minor effects, while variations of diffusion coefficients or positions of conductive zones can affect local profile shapes and thus evolution times. Finally, no evidence of potential cross-formation flow between the overlying and underlying aquifers (Malm and Keuper) could be identified from simulations including advective transport.</div></div>","PeriodicalId":8064,"journal":{"name":"Applied Geochemistry","volume":"197 ","pages":"Article 106654"},"PeriodicalIF":3.4,"publicationDate":"2025-12-13","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145789482","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2025-12-10DOI: 10.1016/j.apgeochem.2025.106651
Jingjing Gong , Lujun Lin , Jianweng Gao , Yingjie Gao , Hui Wu , Yong Li , Jianzhou Yang , Zhuang Duan , Zuohuai Yang , Shixin Tang
The exploration of critical minerals, such as lithium (Li) and beryllium (Be), plays a vital role in supporting various high-tech industries. The southern margin of Xinjiang, China, which extends from the Western Kunlun to the Altun Mountains, has revealed promising Li–Be rare metal deposits—including the Dahongliutan and Washixianan occurrences—suggesting considerable potential for further discoveries. Regional-scale geochemical surveys (ranging from 1:200,000 to 1:500,000) have provided extensive coverage of this area, yielding abundant geochemical data. While these datasets were originally collected decades ago, their full potential for identifying rare metal deposits via modern compositional data analysis (CoDA) methods has not been fully realized. In this study, we reuse these existing regional geochemical data and apply the isometric log-ratio robust principal component analysis (ilr-RPCA) method to develop a novel composite indicator for effectively delineating pegmatite-type Li–Be deposits. The results indicated that although conventional geochemical anomalies of Li and Be correlate well with known deposits, the intensity and spatial distribution of mineralization-related anomalies vary significantly, potentially leading to the omission of certain mineralized anomalies. Through ilr-RPCA, two distinct element associations were identified: (1) Li, Be, and B, which are closely linked to pegmatite-type Li–Be mineralization, and (2) La, Y, Zr, and Nb, representative of the geochemical background associated with acidic rock formations. Anomaly maps derived from the ratio between these two groups accurately pinpoint the locations of pegmatite-type Li–Be deposits, demonstrating the effectiveness of the CoDA approach in geochemical prospectivity mapping. Based on this approach, four prospective areas for rare metal mineralization have been delineated. This methodology offers practical guidance for mineral exploration companies and government agencies in their decision-making processes.
{"title":"Regional geochemical prospecting for Li–Be rare earth deposits: A case study in Southern Xinjiang, China","authors":"Jingjing Gong , Lujun Lin , Jianweng Gao , Yingjie Gao , Hui Wu , Yong Li , Jianzhou Yang , Zhuang Duan , Zuohuai Yang , Shixin Tang","doi":"10.1016/j.apgeochem.2025.106651","DOIUrl":"10.1016/j.apgeochem.2025.106651","url":null,"abstract":"<div><div>The exploration of critical minerals, such as lithium (Li) and beryllium (Be), plays a vital role in supporting various high-tech industries. The southern margin of Xinjiang, China, which extends from the Western Kunlun to the Altun Mountains, has revealed promising Li–Be rare metal deposits—including the Dahongliutan and Washixianan occurrences—suggesting considerable potential for further discoveries. Regional-scale geochemical surveys (ranging from 1:200,000 to 1:500,000) have provided extensive coverage of this area, yielding abundant geochemical data. While these datasets were originally collected decades ago, their full potential for identifying rare metal deposits via modern compositional data analysis (CoDA) methods has not been fully realized. In this study, we reuse these existing regional geochemical data and apply the isometric log-ratio robust principal component analysis (ilr-RPCA) method to develop a novel composite indicator for effectively delineating pegmatite-type Li–Be deposits. The results indicated that although conventional geochemical anomalies of Li and Be correlate well with known deposits, the intensity and spatial distribution of mineralization-related anomalies vary significantly, potentially leading to the omission of certain mineralized anomalies. Through ilr-RPCA, two distinct element associations were identified: (1) Li, Be, and B, which are closely linked to pegmatite-type Li–Be mineralization, and (2) La, Y, Zr, and Nb, representative of the geochemical background associated with acidic rock formations. Anomaly maps derived from the ratio between these two groups accurately pinpoint the locations of pegmatite-type Li–Be deposits, demonstrating the effectiveness of the CoDA approach in geochemical prospectivity mapping. Based on this approach, four prospective areas for rare metal mineralization have been delineated. This methodology offers practical guidance for mineral exploration companies and government agencies in their decision-making processes.</div></div>","PeriodicalId":8064,"journal":{"name":"Applied Geochemistry","volume":"197 ","pages":"Article 106651"},"PeriodicalIF":3.4,"publicationDate":"2025-12-10","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145736286","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Carbon capture, utilisation and storage is among the key strategies to mitigate the increasing concentration of atmospheric carbon dioxide. Mineral carbonation stands out as a promising solution for long-term carbon sequestration by exploiting Ca–Mg-bearing oxides, hydroxides, and silicate minerals such as olivine and serpentine. Although the reaction occurs spontaneously in nature, it is strongly hindered by mineralogical and structural factors.
In this study, nanocrystalline pure forsterite and Mg- and Ni-endmember serpentines were synthesised as model phases to disentangle the role of composition, crystal structure, and morphology in incipient dissolution and carbonation and to maximise reactivity through increased surface-to-volume ratios. The choice of Ni-serpentine endmember aims to investigate the fate of Ni after dissolution and carbonation, considering that in nature serpentine can incorporate up to 0.5 wt% of nickel oxide. A systematic experimental strategy was designed to investigate their early-stage dissolution and carbonation behaviour under mild hydrothermal conditions (100 °C, pCO2 ≤ 6 bar), using microwave-assisted treatments in a controlled environment. The products were thoroughly characterised, both as solid precipitates and aqueous components, through X-ray Powder Diffraction, Scanning Electron Microscopy, Transmission Electron Microscopy, micro-Raman and Inductively Coupled Plasma – Optical Emission Spectroscopy. This direct, parallel comparison reveals distinct behaviours among the tested materials, with forsterite and Mg-serpentine releasing Mg into solution and promoting the formation of hydrated Mg-carbonates, whereas Ni-serpentine nanocrystals remain largely inert, immobilising Ni within their structure. These findings have potential implications not only for carbon dioxide sequestration but also for critical metal recovery processes.
{"title":"Reactive pathways of synthetic forsterite and Mg/Ni-serpentine: Insights into incipient dissolution and carbonation","authors":"Mattia Corti , Daniela D'Alessio , Mara Murri , Giancarlo Capitani , Marcello Campione , Nadia Malaspina","doi":"10.1016/j.apgeochem.2025.106650","DOIUrl":"10.1016/j.apgeochem.2025.106650","url":null,"abstract":"<div><div>Carbon capture, utilisation and storage is among the key strategies to mitigate the increasing concentration of atmospheric carbon dioxide. Mineral carbonation stands out as a promising solution for long-term carbon sequestration by exploiting Ca–Mg-bearing oxides, hydroxides, and silicate minerals such as olivine and serpentine. Although the reaction occurs spontaneously in nature, it is strongly hindered by mineralogical and structural factors.</div><div>In this study, nanocrystalline pure forsterite and Mg- and Ni-endmember serpentines were synthesised as model phases to disentangle the role of composition, crystal structure, and morphology in incipient dissolution and carbonation and to maximise reactivity through increased surface-to-volume ratios. The choice of Ni-serpentine endmember aims to investigate the fate of Ni after dissolution and carbonation, considering that in nature serpentine can incorporate up to 0.5 wt% of nickel oxide. A systematic experimental strategy was designed to investigate their early-stage dissolution and carbonation behaviour under mild hydrothermal conditions (100 °C, <em>p</em>CO<sub>2</sub> ≤ 6 bar), using microwave-assisted treatments in a controlled environment. The products were thoroughly characterised, both as solid precipitates and aqueous components, through X-ray Powder Diffraction, Scanning Electron Microscopy, Transmission Electron Microscopy, micro-Raman and Inductively Coupled Plasma – Optical Emission Spectroscopy. This direct, parallel comparison reveals distinct behaviours among the tested materials, with forsterite and Mg-serpentine releasing Mg into solution and promoting the formation of hydrated Mg-carbonates, whereas Ni-serpentine nanocrystals remain largely inert, immobilising Ni within their structure. These findings have potential implications not only for carbon dioxide sequestration but also for critical metal recovery processes.</div></div>","PeriodicalId":8064,"journal":{"name":"Applied Geochemistry","volume":"196 ","pages":"Article 106650"},"PeriodicalIF":3.4,"publicationDate":"2025-12-08","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145733229","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2025-12-06DOI: 10.1016/j.apgeochem.2025.106649
Dongfang Ke , Weiqiang Feng , Peng Liao , Rong Li , Ruina Xu , Yu-Min Chou , Peixue Jiang
Underground hydrogen storage (UHS) in porous reservoirs faces biogeochemical challenges such as microbial hydrogen consumption and the generation of secondary gases, which can significantly compromise storage efficiency. To address critical knowledge gaps concerning the interactions between hydrogen, minerals, and microbes under kinetic parameter uncertainty, this study develops a novel co-simulation framework coupling MATLAB with Phreeqc. This integrated model combines kinetic formulations for mineral dissolution and precipitation (e.g., calcite and gypsum), microbial metabolism (e.g., sulfate reduction and methanogenesis), and thermodynamic gas-liquid equilibrium to simulate the complex gas-water-rock interactions during UHS. Simulation results reveal that hydrogen loss (<0.22 %) and purity degradation (<0.0002 %) are negligible under typical anaerobic reservoir conditions, constrained by an intrinsic microbial kinetic threshold. Substantial hydrogen consumption occurs only when the maximum specific reaction rate (Vmax) exceeds 10−4.5 s−1; below this value, hydrogen depletion remains minimal irrespective of variations in mineral reactivity, mineral content, or initial biomass concentration. Abiotic mineral dissolution plays a pivotal role in sustaining microbial activity by supplying essential dissolved inorganic carbon (as a carbon source) and electron acceptors (e.g., SO42−, HCO3−). Furthermore, biomass accumulation exhibits self-limiting behavior due to pore-space constraints, indicating limited effectiveness of post-cycle biomass removal strategies. However, under high-kinetic regimes, severe bioclogging and significant hydrogen loss can occur, highlighting the necessity of proactive microbial metabolic suppression to ensure the long-term viability of UHS operations.
{"title":"Kinetic model reveals microbial-mediated hydrogen consumption and abiotic mineral reactions jointly control hydrogen depletion during geological storage","authors":"Dongfang Ke , Weiqiang Feng , Peng Liao , Rong Li , Ruina Xu , Yu-Min Chou , Peixue Jiang","doi":"10.1016/j.apgeochem.2025.106649","DOIUrl":"10.1016/j.apgeochem.2025.106649","url":null,"abstract":"<div><div>Underground hydrogen storage (UHS) in porous reservoirs faces biogeochemical challenges such as microbial hydrogen consumption and the generation of secondary gases, which can significantly compromise storage efficiency. To address critical knowledge gaps concerning the interactions between hydrogen, minerals, and microbes under kinetic parameter uncertainty, this study develops a novel co-simulation framework coupling MATLAB with Phreeqc. This integrated model combines kinetic formulations for mineral dissolution and precipitation (e.g., calcite and gypsum), microbial metabolism (e.g., sulfate reduction and methanogenesis), and thermodynamic gas-liquid equilibrium to simulate the complex gas-water-rock interactions during UHS. Simulation results reveal that hydrogen loss (<0.22 %) and purity degradation (<0.0002 %) are negligible under typical anaerobic reservoir conditions, constrained by an intrinsic microbial kinetic threshold. Substantial hydrogen consumption occurs only when the maximum specific reaction rate (<em>V</em><sub>max</sub>) exceeds 10<sup>−4.5</sup> s<sup>−1</sup>; below this value, hydrogen depletion remains minimal irrespective of variations in mineral reactivity, mineral content, or initial biomass concentration. Abiotic mineral dissolution plays a pivotal role in sustaining microbial activity by supplying essential dissolved inorganic carbon (as a carbon source) and electron acceptors (e.g., SO<sub>4</sub><sup>2−</sup>, HCO<sub>3</sub><sup>−</sup>). Furthermore, biomass accumulation exhibits self-limiting behavior due to pore-space constraints, indicating limited effectiveness of post-cycle biomass removal strategies. However, under high-kinetic regimes, severe bioclogging and significant hydrogen loss can occur, highlighting the necessity of proactive microbial metabolic suppression to ensure the long-term viability of UHS operations.</div></div>","PeriodicalId":8064,"journal":{"name":"Applied Geochemistry","volume":"196 ","pages":"Article 106649"},"PeriodicalIF":3.4,"publicationDate":"2025-12-06","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145733113","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2025-12-03DOI: 10.1016/j.apgeochem.2025.106648
Erik J.H. Oerter , Miguel Cisneros , Eric Pili , Michael Singleton , Pierre Agrinier , Travis Tenner , Ruth Kips
Determining the origin and history of interdicted nuclear materials is a central challenge in nuclear forensics. The oxygen stable isotope composition of uranium oxide compounds has emerged as a promising forensic signature, attracting increasing attention since the early 2000s. This review examines analytical techniques for measuring oxygen isotope compositions in uranium oxides and evaluates how the nuclear fuel production cycle introduces or modifies these isotopic signatures. The potential for forensic geolocation is explored through workflows that calibrate the relationship between environmental water oxygen isotopes and those found in uranium oxides. Key strengths and limitations of this approach are assessed, including gaps in knowledge related to isotope fractionation during specific stages of the fuel cycle, and processing facility water inputs. The importance of proper sample handling and storage under inert atmospheres, as well as a deeper understanding of both intra-sample oxygen isotope heterogeneity, and hydrous uranium oxide phase formation, is highlighted for improving the reliability of forensic interpretations. The development of uranium oxide standards with well-characterized δ18O values and international collaboration toward consensus on their use are identified as essential steps for advancing the field.
{"title":"Oxygen stable isotopes in the nuclear fuel cycle: Assessment of the potential for determining the fabrication and provenance history of anhydrous and hydrous uranium oxides","authors":"Erik J.H. Oerter , Miguel Cisneros , Eric Pili , Michael Singleton , Pierre Agrinier , Travis Tenner , Ruth Kips","doi":"10.1016/j.apgeochem.2025.106648","DOIUrl":"10.1016/j.apgeochem.2025.106648","url":null,"abstract":"<div><div>Determining the origin and history of interdicted nuclear materials is a central challenge in nuclear forensics. The oxygen stable isotope composition of uranium oxide compounds has emerged as a promising forensic signature, attracting increasing attention since the early 2000s. This review examines analytical techniques for measuring oxygen isotope compositions in uranium oxides and evaluates how the nuclear fuel production cycle introduces or modifies these isotopic signatures. The potential for forensic geolocation is explored through workflows that calibrate the relationship between environmental water oxygen isotopes and those found in uranium oxides. Key strengths and limitations of this approach are assessed, including gaps in knowledge related to isotope fractionation during specific stages of the fuel cycle, and processing facility water inputs. The importance of proper sample handling and storage under inert atmospheres, as well as a deeper understanding of both intra-sample oxygen isotope heterogeneity, and hydrous uranium oxide phase formation, is highlighted for improving the reliability of forensic interpretations. The development of uranium oxide standards with well-characterized δ<sup>18</sup>O values and international collaboration toward consensus on their use are identified as essential steps for advancing the field.</div></div>","PeriodicalId":8064,"journal":{"name":"Applied Geochemistry","volume":"196 ","pages":"Article 106648"},"PeriodicalIF":3.4,"publicationDate":"2025-12-03","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145733228","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2025-12-03DOI: 10.1016/j.apgeochem.2025.106647
Zhenchen Wan , Yuxuan Tan , Yunsong Zheng , Xiuli Li , Songhu Yuan
Dissolved O2 (DO) levels in the shallow subsurface, controlled by both chemical and biological processes, play an important role in contaminant transformation and attenuation. However, methods for tracing chemical and biological DO consumption are not available. Here we show that oxygen isotope enrichment factors (ε) can be used to trace the mechanisms of chemical and biological O2 consumption in the shallow subsurface. In batch solution experiments, the ε values for O2 consumption by dissolved Fe(II), dissolved organic carbon (DOC), and their mixtures at different C/Fe ratios (0.5∼20) were measured to range from -1.74 ‰ to -3.32 ‰. In the oxygenation of reduced clayed sediment suspension, the ε values were relatively small (-6.46 ‰) in the initial 15 h and increased to a large level (-18.14 ‰) afterward; while for the sand sediment suspension, the ε values were always small (ranging from -4.56 ‰ to -4.65 ‰) throughout the duration time of 24 h. Chemical probe and sterilized control experiments proved that the initial stage characterized with small ε values (<-10 ‰) was dominated by chemical O2 consumption and the subsequent stage with large ε values (>-10 ‰) was dominated by biological O2 consumption. As an effective indicator for distinguishing subsurface chemical and biological oxygen consumption pathways, ε will provide a new parameter for exploring carbon and nitrogen cycling and pollution transformation.
{"title":"Tracing chemical and biological O2 consumption in the subsurface by 18O isotope enrichment factors","authors":"Zhenchen Wan , Yuxuan Tan , Yunsong Zheng , Xiuli Li , Songhu Yuan","doi":"10.1016/j.apgeochem.2025.106647","DOIUrl":"10.1016/j.apgeochem.2025.106647","url":null,"abstract":"<div><div>Dissolved O<sub>2</sub> (DO) levels in the shallow subsurface, controlled by both chemical and biological processes, play an important role in contaminant transformation and attenuation. However, methods for tracing chemical and biological DO consumption are not available. Here we show that oxygen isotope enrichment factors (<em>ε</em>) can be used to trace the mechanisms of chemical and biological O<sub>2</sub> consumption in the shallow subsurface. In batch solution experiments, the <em>ε</em> values for O<sub>2</sub> consumption by dissolved Fe(II), dissolved organic carbon (DOC), and their mixtures at different C/Fe ratios (0.5∼20) were measured to range from -1.74 ‰ to -3.32 ‰. In the oxygenation of reduced clayed sediment suspension, the <em>ε</em> values were relatively small (-6.46 ‰) in the initial 15 h and increased to a large level (-18.14 ‰) afterward; while for the sand sediment suspension, the <em>ε</em> values were always small (ranging from -4.56 ‰ to -4.65 ‰) throughout the duration time of 24 h. Chemical probe and sterilized control experiments proved that the initial stage characterized with small <em>ε</em> values (<-10 ‰) was dominated by chemical O<sub>2</sub> consumption and the subsequent stage with large <em>ε</em> values (>-10 ‰) was dominated by biological O<sub>2</sub> consumption. As an effective indicator for distinguishing subsurface chemical and biological oxygen consumption pathways, <em>ε</em> will provide a new parameter for exploring carbon and nitrogen cycling and pollution transformation.</div></div>","PeriodicalId":8064,"journal":{"name":"Applied Geochemistry","volume":"196 ","pages":"Article 106647"},"PeriodicalIF":3.4,"publicationDate":"2025-12-03","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145681777","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2025-11-29DOI: 10.1016/j.apgeochem.2025.106646
Helge C. Moog , Marcus Altmaier , Frank Bok , Vinzenz Brendler , Daniela Freyer , Xavier Gaona , Sven Hagemann , Claudia Joseph , George-Dan Miron , Melanie Pannach , Julia Sohr , Wolfgang Voigt , Marie Voss , Laurin Wissmeier
The Thermodynamic Reference Database (THEREDA) is designed for geochemical calculations in the context of repositories for radioactive waste under high-saline conditions. For this purpose, it adopts the Pitzer ion-interaction approach. THEREDA is currently the only database worldwide that allows comprehensive polythermal calculations (up to at least 100 °C) of the hexary system of the oceanic salts Na-K-Mg-Ca-Cl-SO4-H2O, including acids, bases, and CO2/carbonates. Its validity is documented primarily, yet not exclusively, by application to solubility data. THEREDA's potential to predict the development of the geochemical environment, e.g. in the event of an intrusion of solution, constitutes a prerequisite for the engineering design of a nuclear waste repository with regard to the selection and placement of plug and sealing system components.
The focus of THEREDA lies on the calculation of solubilities of radionuclides (actinides, fission and activation products), chemotoxic and matrix elements e.g., canister materials, and compounds having an impact on the overall geochemical milieu in the near field of a repository under high-saline conditions.
Special features of THEREDA besides its focus on high-saline solutions are procedures for testing prior to any release combined with intercode-comparison, extensive and publicly available validation against published experimental data, and systematic application of a scheme to mark data with regard to quality, reliability, and origin. Traceability of data and validated experimental results to published sources is also emphasised. This documentation is in part realised in ready-to-use parameter files for users, and in part on the website (www.thereda.de). Another feature is the possibility for operation of THEREDA by several institutions in a net-worked manner.
To highlight THEREDA's potential, examples for applications of the database are given. Additionally, ongoing efforts for the further development of THEREDA are described in the outlook at the end of this article.
{"title":"THEREDA: Thermodynamic reference database for geochemical modelling of nuclear waste disposal under saline conditions – Application, overview, and new developments","authors":"Helge C. Moog , Marcus Altmaier , Frank Bok , Vinzenz Brendler , Daniela Freyer , Xavier Gaona , Sven Hagemann , Claudia Joseph , George-Dan Miron , Melanie Pannach , Julia Sohr , Wolfgang Voigt , Marie Voss , Laurin Wissmeier","doi":"10.1016/j.apgeochem.2025.106646","DOIUrl":"10.1016/j.apgeochem.2025.106646","url":null,"abstract":"<div><div>The Thermodynamic Reference Database (THEREDA) is designed for geochemical calculations in the context of repositories for radioactive waste under high-saline conditions. For this purpose, it adopts the Pitzer ion-interaction approach. THEREDA is currently the only database worldwide that allows comprehensive polythermal calculations (up to at least 100 °C) of the hexary system of the oceanic salts Na-K-Mg-Ca-Cl-SO<sub>4</sub>-H<sub>2</sub>O, including acids, bases, and CO<sub>2</sub>/carbonates. Its validity is documented primarily, yet not exclusively, by application to solubility data. THEREDA's potential to predict the development of the geochemical environment, e.g. in the event of an intrusion of solution, constitutes a prerequisite for the engineering design of a nuclear waste repository with regard to the selection and placement of plug and sealing system components.</div><div>The focus of THEREDA lies on the calculation of solubilities of radionuclides (actinides, fission and activation products), chemotoxic and matrix elements e.g., canister materials, and compounds having an impact on the overall geochemical milieu in the near field of a repository under high-saline conditions.</div><div>Special features of THEREDA besides its focus on high-saline solutions are procedures for testing prior to any release combined with intercode-comparison, extensive and publicly available validation against published experimental data, and systematic application of a scheme to mark data with regard to quality, reliability, and origin. Traceability of data and validated experimental results to published sources is also emphasised. This documentation is in part realised in ready-to-use parameter files for users, and in part on the website (<span><span>www.thereda.de</span><svg><path></path></svg></span>). Another feature is the possibility for operation of THEREDA by several institutions in a net-worked manner.</div><div>To highlight THEREDA's potential, examples for applications of the database are given. Additionally, ongoing efforts for the further development of THEREDA are described in the outlook at the end of this article.</div></div>","PeriodicalId":8064,"journal":{"name":"Applied Geochemistry","volume":"196 ","pages":"Article 106646"},"PeriodicalIF":3.4,"publicationDate":"2025-11-29","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145733114","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
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