Applied Geochemistry最新文献

{"title":"A study of palsa bog organic matter stabilization in response to holocene climate change using 13C NMR and FTICR MS","authors":"Roman Vasilevich ,&nbsp;Alexander Zherebker ,&nbsp;Oleg Kuznetsov","doi":"10.1016/j.apgeochem.2025.106417","DOIUrl":"10.1016/j.apgeochem.2025.106417","url":null,"abstract":"<div><div>The ¹³C NMR and high-resolution mass spectrometry (HRMS) methods have been employed to elucidate the principal pathways of soil organic matter (SOM) stabilization in the peat deposit of palsa bogs in the European Arctic. Extremes of labile/condensed constituents and structural moieties have been found to be related to climatic and hydrological conditions during different periods of the Holocene. The initial stage of SOM stabilization includes decomposition of plant residues, formation of (pro)humic substances (HSs) molecules from high-molecular-weight precursors, and primary transformation of HS molecules with degradation of the most labile fragments.</div><div>The more favorable climatic conditions of the Early Holocene (Atlantic Optimum) and Middle Holocene (SB2) determined the botanical composition of the peat, which was dominated by sedge and tree-sedge communities with high contents of lignin components and, as a consequence, a greater proportion of aromatic fragments, characterized by thermo-biodynamic resistance in the humic acids (HAs) of horizons in the lower and central parts of the profile. Older HAs, which underwent intense degradation were enriched in the N,S-containing components as compared to HAs from surface layers. This is in turn accompanied by an overall decrease in the proportion of unoxidised aliphatic and carbohydrate fragments. A substantial proportion of highly condensed fragments were identified in HAs by HRMS. It was suggested that aromatic and condensed HA molecules contain long-chain substituents which contribute to the content of aliphatic carbon. The ratio of pentosans to hexosans in HAs is demonstrated to increase down the peat profile as a consequence of the redistribution of the dominant peat formers. The HA branching indices demonstrate a significant transformation of long-chain structures and an increase in the contribution of substituted aliphatic fragments in the HA structure.</div></div>","PeriodicalId":8064,"journal":{"name":"Applied Geochemistry","volume":"187 ","pages":"Article 106417"},"PeriodicalIF":3.1,"publicationDate":"2025-05-12","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144107806","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}

{"title":"The effect of bentonite colloids on sorption of Eu in crystalline rock and its minerals","authors":"Noora Pakkanen ,&nbsp;Louison Biez ,&nbsp;Ester M. Jolis ,&nbsp;Artem Dziuba ,&nbsp;Xiaodong Li ,&nbsp;Marja Siitari-Kauppi","doi":"10.1016/j.apgeochem.2025.106415","DOIUrl":"10.1016/j.apgeochem.2025.106415","url":null,"abstract":"<div><div>This study examines Eu sorption on two Olkiluoto crystalline rocks and their minerals in low-salinity groundwater conditions. Sorption was studied as a function of ¹⁵¹EuCl₃ molarity and pH. In addition, the competitive effect of MX-80 bentonite colloids on Eu sorption was examined. To understand Eu's behavior in different experimental scenarios, the factors influencing Eu sorption were further investigated by means of CEC, and zeta potential analysis of the materials used. The study revealed that the strongest sorbents for Eu under the defined conditions were biotite and biotite-rich heterogeneous metatexitic gneiss. Depending on the rock matrix used and the colloid concentration of the solution, the introduction of bentonite colloids as a competing agent significantly reduced the sorption of Eu on rock matrix. These findings provide insights into radionuclide mobility in natural and engineered systems.</div></div>","PeriodicalId":8064,"journal":{"name":"Applied Geochemistry","volume":"187 ","pages":"Article 106415"},"PeriodicalIF":3.1,"publicationDate":"2025-05-10","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144099731","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}

{"title":"Accurate prediction of carbon monoxide in aqueous solutions for geological sequestration applications","authors":"Li Sun ,&nbsp;Jierong Liang","doi":"10.1016/j.apgeochem.2025.106414","DOIUrl":"10.1016/j.apgeochem.2025.106414","url":null,"abstract":"<div><div>Accurate prediction of solubilities in aqueous solutions is crucial for the geological sequestration of carbon monoxide (CO). This study utilizes the electrolyte version of the Cubic-Plus-Association (CPA) Equation of State to calculate the saturated properties including saturated vapor pressure, saturated liquid-phase density, and saturated vapor-phase density of pure CO, its solubilities in pure water, and its solubilities in aqueous sodium chloride solutions. The model accuracy is validated against experimental data, showing relative average deviations within 3.0 % for saturated liquid-phase density, within 1.0 % for both saturated vapor pressure and saturated vapor-phase density, 4.7 % for CO solubilities in pure water, and 1.3 % for CO solubilities in aqueous sodium chloride solutions. This work not only analyzes the phase behavior of CO in aqueous solutions but also provides an in-depth discussion on the dissolution mechanisms of CO in these solutions. The results demonstrate that the electrolyte version of the CPA Equation of State is a robust model capable of accurately predicting CO solubilities and the complex phase behavior of CO in aqueous solutions across a wide range of temperatures, pressures, and salt concentrations.</div></div>","PeriodicalId":8064,"journal":{"name":"Applied Geochemistry","volume":"187 ","pages":"Article 106414"},"PeriodicalIF":3.1,"publicationDate":"2025-05-08","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143937062","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}

{"title":"Decadal transport of trace elements in a cave system based on 16 years monitoring data: Implications for paleoclimate reconstruction","authors":"Xin Fu ,&nbsp;Yan Yang ,&nbsp;Jingyao Zhao ,&nbsp;Yidong Li ,&nbsp;Xiaomin Chen ,&nbsp;Zhimao Ye ,&nbsp;Mingyang Li ,&nbsp;Jingfeng Lin ,&nbsp;Yanzhi Xu","doi":"10.1016/j.apgeochem.2025.106413","DOIUrl":"10.1016/j.apgeochem.2025.106413","url":null,"abstract":"<div><div>The trace element ratios (X/Ca, X = Mg, Sr, Ba) of stalagmites are closely correlated with local hydroclimatic changes and are becoming increasingly important proxies for paleoclimate reconstruction. However, it remains unclear whether the decadal variations in the X/Ca ratios can reflect the signals of the Pacific Decadal Oscillation (PDO) and Atlantic Multidecadal Variability (AMV) in East Asia. Here, 16 years (2009–2024) of monitoring data on the trace element composition of cave water in Jiguan Cave, located in the middle and lower reaches of the Yellow River in China, were combined with an analysis of X/Ca ratios in stalagmite DSY1201 from the nearby Dongshiya Cave. The primary objective was to comprehensively explore the intricate relationship between the X/Ca ratios and the regional hydroclimatic variations. Our investigation revealed that the decadal changes in the X/Ca Principal Component 1 (PC1) exhibited a significant negative correlation with the PDO. This correlation was likely predominantly caused by the synergistic effects of prior calcite precipitation (PCP), water–rock interaction (WRI), and other factors. Notably, under drought conditions in Jiguan Cave, WRI dominates the hydro-chemical evolution of the cave water, while the reduction in the recharge flux and the prolongation of the water residence time jointly induce a marked enhancement in the X/Ca ratios. Correlation analysis further demonstrated that the PDO significantly modulates the amplitude of the X/Ca-PC1 variability by regulating the frequency of extreme precipitation or drought events during critical years. In addition, the multi-proxy records (X/Ca-PC1, δ¹³C, and δ¹⁸O) from stalagmite DSY1201 revealed similar relationships and patterns in the AMV and PDO phase transitions during the 1960s and late 1990s. Thus, we ultimately suggest that the AMV and PDO play important roles in the decadal variations in the intensity of the East Asian summer monsoon (EASM) and the spatial pattern of the EASM rainfall, in combination with the AMV-Northern Hemisphere (ANH) teleconnection and the Pacific-East Asia (PEA) teleconnection, respectively. This may be recorded by the X/Ca ratios in the karst cave systems in the EASM area.</div></div>","PeriodicalId":8064,"journal":{"name":"Applied Geochemistry","volume":"187 ","pages":"Article 106413"},"PeriodicalIF":3.1,"publicationDate":"2025-05-08","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143943531","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}

{"title":"Ligand exchange by As(V) enhanced desferrioxamine B-induced goethite dissolution: Insights into As mobilization in groundwater systems","authors":"Simeng Li ,&nbsp;Wei Xiu ,&nbsp;Xin Liu ,&nbsp;Zhixin Fang ,&nbsp;Jonathan R. Lloyd ,&nbsp;Huaming Guo","doi":"10.1016/j.apgeochem.2025.106412","DOIUrl":"10.1016/j.apgeochem.2025.106412","url":null,"abstract":"<div><div>The dissolution of As-bearing Fe(III) (oxyhydr)oxides is the key process leading to arsenic (As) enrichment in groundwater, which can be enhanced by organic ligands secreted by microorganisms, such as siderophores. However, the roles of organic ligand-induced dissolution of Fe(III) (oxyhydr)oxides in As mobilization are poorly understood. To address this issue, we examined the dissolution kinetics of pure goethite, As(V)-bearing goethite, and As(III)-bearing goethite induced by the trihydroxamate siderophore desferrioxamine B (DFOB) under anoxic conditions and the associated impact of As mobility. DFOB-induced goethite dissolution followed classic surface-controlled dissolution kinetics. As(V) promoted DFOB-induced goethite dissolution, which was attributed to the presence of Fe-As(V) complexes acting as ligand shuttles. However, As(III) slightly inhibited DFOB-induced goethite dissolution, due to the smaller surface area of narrow and rounded (021) crystal facets of As(III)-bearing goethite. Moreover, during DFOB-induced dissolution of As-bearing goethite, the percentages of released As to total As adsorption in DFOB-As(V)-Gt series (13.85 ± 1.52%) were significantly higher than those (9.82 ± 4.66%) in DFOB-As(III)-Gt series, which were linearly positively correlated with goethite dissolution. Therefore, the present findings emphasized the importance of organic ligand-induced dissolution of As-bearing Fe(III) (oxyhydr)oxides as a potential pathway for mobilizing As in groundwater systems.</div></div>","PeriodicalId":8064,"journal":{"name":"Applied Geochemistry","volume":"187 ","pages":"Article 106412"},"PeriodicalIF":3.1,"publicationDate":"2025-05-07","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143937063","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}

{"title":"Nitrogen distribution and nitrogen isotope fractionation in synthetic 2:1 phyllosilicates under hydrothermal conditions at 200 °C and saturated vapor pressure","authors":"Jaeguk Jo ,&nbsp;Toshiro Yamanaka ,&nbsp;Youko Miyoshi ,&nbsp;Masaya Suzuki ,&nbsp;Yoshihiro Kuwahara ,&nbsp;Isao Kadota ,&nbsp;Hitoshi Chiba ,&nbsp;Bum Han Lee","doi":"10.1016/j.apgeochem.2025.106403","DOIUrl":"10.1016/j.apgeochem.2025.106403","url":null,"abstract":"<div><div>This study investigates nitrogen distribution and isotope fractionation within synthetic 2:1 phyllosilicates, simulating submarine hydrothermal environments at 200 °C and saturated vapor pressure. XRD and EDS results revealed the potential coexistence of multiple cations in the interlayer of synthetic 2:1 phyllosilicate, concurrently suggesting cation substitution in the tetrahedral and/or octahedral sheets. Meanwhile, the iron-enriched 25-5 sample exhibited restricted interlayer expansibility. NH₄⁺ absorptions were identified in the NH₄-stretching (3200–2800 cm⁻¹) and NH₄-bending (1450–1400 cm⁻¹) regions, with wavenumber shifts indicating the influence of interlayer water removal. At pH 10.56, over 95% of nitrogen was released into the gas phase, while at pH 8.88, nitrogen proportions in the liquid and gas phases were comparable (average 48–49%). Experiments with iron at pH ∼8.80 showed that the nitrogen proportion in the gas phase (average 28%) was more than twofold lower than that in the liquid phase (average 68%). Equilibrium isotope fractionation factors indicated discernible preference for heavier nitrogen isotopes in the solid phase (<em>α</em>_{<em>solid-liquid</em>} = 1.009–1.021 and α_solid-gas = 1.011–1.027). The <em>α</em>_{<em>liquid-gas</em>} range for sample 25–2 was 1.001–1.008, while that for the iron-enriched composite 25–5 was 0.997–1.010. Our experimental studies have confirmed that, in the absence of exchange interactions with external substances possessing different nitrogen isotope ratios, nitrogen isotope fractionation between ammonium and ammonia, controlled by variations in temperature and pH during mineralization, plays a crucial role in the variation of nitrogen isotope ratios. Additionally, we confirmed that metal-amines influence nitrogen isotope fractionation by modulating ammonia gas emission. These findings enhance our understanding of nitrogen cycling across the gas, liquid, and solid phases in submarine hydrothermal systems.</div></div>","PeriodicalId":8064,"journal":{"name":"Applied Geochemistry","volume":"187 ","pages":"Article 106403"},"PeriodicalIF":3.1,"publicationDate":"2025-04-29","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144090135","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}

{"title":"Modelling cadmium binding to plant-based biochars using the three-site NICA-Donnan model","authors":"Yifan Huang ,&nbsp;Gerwin F. Koopmans ,&nbsp;Zhengguo Song ,&nbsp;Rob N.J. Comans ,&nbsp;Liping Weng","doi":"10.1016/j.apgeochem.2025.106404","DOIUrl":"10.1016/j.apgeochem.2025.106404","url":null,"abstract":"<div><div>In this study, generic three-site NICA model parameters for cadmium (Cd) binding to biochars were derived. For this purpose, five biochars prepared from two mixtures of pure cellulose and lignin and maize straw at different pyrolysis temperatures were selected from our previous work to measure Cd binding in batch experiments. This dataset was complemented with data on Cd binding from five other plant-based biochars taken from literature. The three-site NICA model in combination with an electrostatic Donnan model using a constant Donnan volume <span><math><mrow><msub><mi>V</mi><mi>D</mi></msub></mrow></math></span> of 0.1 L kg⁻¹ successfully described the data, covering a wide range in pH and free Cd²⁺ concentration in solution. The model provided quantitative insights into the surface speciation of Cd and the electrostatic interactions between Cd and biochar. Carboxylic- and phenolic-type reactive groups exhibited a lower Cd affinity compared to protons, leading to a strong pH dependency of Cd binding. Cadmium ions bind predominantly as a monodentate complex with carboxylic groups and as mono- and bidentate complexes with phenolic groups on biochar. Although phenolic groups have a higher affinity to bind Cd, carboxylic groups dominate Cd binding due to the smaller difference in the affinity of the latter groups to bind Cd and protons. In addition, the small ionic strength effect on Cd adsorption can be ascribed to the low charge density of biochar and the presence of basic groups (i.e., the third type of sites) on biochar. The basic groups generate positive charge, neutralizing to a certain extent the negative charge generated by the acidic groups, thus weakening the ionic strength effect. Due to this electrostatic effect, ignoring the presence of the basic groups will lead to an overestimation of Cd binding by biochar. In addition to these quantitative mechanistic insights, the derived generic model parameters for the three-site NICA-Donnan model can help to predict Cd binding to unknown biochars over a wide range in pH and ionic strength to support the design of <em>in-situ</em> soil remediation operations.</div></div>","PeriodicalId":8064,"journal":{"name":"Applied Geochemistry","volume":"186 ","pages":"Article 106404"},"PeriodicalIF":3.1,"publicationDate":"2025-04-28","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143887097","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}

{"title":"Bulk rock geochemical and mineralogical characterisation of clay-rich sediments from drill core analysis of the Staffelegg Formation","authors":"Marie Bonitz ,&nbsp;Theresa Hennig ,&nbsp;Anja M. Schleicher ,&nbsp;David Jaeggi ,&nbsp;Jessica A. Stammeier ,&nbsp;Christian Ostertag-Henning ,&nbsp;Michael Kühn","doi":"10.1016/j.apgeochem.2025.106389","DOIUrl":"10.1016/j.apgeochem.2025.106389","url":null,"abstract":"<div><div>The long-term integrity of argillaceous formations as host rocks for deep geological disposal of nuclear waste depends significantly on hydrogeological factors. A 58 m long borehole was drilled at the Mont Terri Rock Laboratory (Switzerland) from the Opalinus Clay through the entire underlying Staffelegg Formation, which includes two water-bearing sections. Groundwater was found locally in the Beggingen and Rietheim Members, otherwise known as Gryphaea Limestone and Posidonia Shale, respectively. We want to identify indicators to determine the impact of groundwater flow in clay- and carbonate-rich sediments by characterising mineralogical and geochemical alteration. The groundwater influence is restricted to the water-bearing zones and can be identified by fractures and calcite veins. Additional indicators like mineral assemblage, rock geochemistry and the combination of different redox proxies, show constrained groundwater influence in the clay-rich areas. To investigate in particular the water-bearing horizons on a smaller scale (mm-<span><math><mi>μ</mi></math></span>m) would help to detect further alteration and mobilisation features.</div></div>","PeriodicalId":8064,"journal":{"name":"Applied Geochemistry","volume":"186 ","pages":"Article 106389"},"PeriodicalIF":3.1,"publicationDate":"2025-04-25","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143877492","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}

{"title":"Mössbauer spectroscopy: a key tool to quantify Fe-speciation and distribution in H2-generating rocks","authors":"U. Geymond ,&nbsp;K. Loiseau ,&nbsp;V. Roche ,&nbsp;G. Pasquet ,&nbsp;S. Revillon ,&nbsp;M. Sougrati ,&nbsp;I. Moretti","doi":"10.1016/j.apgeochem.2025.106399","DOIUrl":"10.1016/j.apgeochem.2025.106399","url":null,"abstract":"<div><div>Oxidation of Fe²⁺ by anoxic water in the subsurface is a key geochemical process, contributing to the formation of natural dihydrogen (H₂). The development and application of effective tools to accurately characterize the content and speciation of iron in samples is thus a major concern for H₂ prospection. Traditionally, the study of iron has been conducted through either time-consuming analyses at the micrometer scale or faster analyses at the bulk rock scale, raising concerns about the accuracy and representativeness of the characterization depending on the chosen approach. Moreover, most techniques are typically limited to determining either Fe distribution or Fe speciation, thus necessitating a full series of analyses to reach a comprehensive understanding of the sample. This approach does not align with the need for rapid and numerous characterizations required in H₂ prospection programs. In this study, we investigated the relevance of using Mössbauer Spectroscopy (MS) on complex mineral assemblage, by characterizing five Fe-rich natural samples. Among others, we conclude, based on the quality of the resulting spectra fitting that room-temperature (295K) data collection is more effective than low-temperature (6K) data collection, due to the challenges in deconvoluting the complex spectra of mixed mineral assemblages at low temperature. Fe²⁺/ΣFe ratios obtained from MS are compared with those derived from conventional Fe²⁺ titration on the same samples. The comparison shows a great correlation between MS and titration results with an average deviation of 0.04 on the Fe²⁺/ΣFe ratio. This confirms the reliability of MS, providing at the same time insights into both Fe distribution (i.e., Fe mineralogy) and Fe speciation, contrary to titration that only gives access to bulk Fe²⁺/ΣFe ratio. Finally, results show that the accuracy of MS spectra fitting is significantly influenced by prior knowledge of the sample mineralogy, which can be easily leveraged by rapid and routinely performed characterization techniques (e.g., multispectral mineral imaging).</div></div>","PeriodicalId":8064,"journal":{"name":"Applied Geochemistry","volume":"187 ","pages":"Article 106399"},"PeriodicalIF":3.1,"publicationDate":"2025-04-23","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144099701","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}

{"title":"Uranium(VI) retention by calcium (alumino)silicate hydrates – Impact of temperature and ionic strength","authors":"Katja Schmeide ,&nbsp;Nina M. Huittinen ,&nbsp;Salim Shams Aldin Azzam ,&nbsp;Frank Bok ,&nbsp;Erica Brendler ,&nbsp;Barbara Lothenbach ,&nbsp;Jerome Kretzschmar","doi":"10.1016/j.apgeochem.2025.106400","DOIUrl":"10.1016/j.apgeochem.2025.106400","url":null,"abstract":"<div><div>Calcium aluminosilicate hydrates (C-A-S-H) are the main hydration products of cement formulations with Al-rich additives such as blast furnace slags, fly ashes or calcined clays. We studied systematically the effect of Al substitution on both the structure of C-A-S-H phases and their U(VI) retention properties in comparison to C-S-H phases. To represent the different stages of cement degradation, three series of samples were synthesized, which included samples with Ca/Si molar ratios of 0.8, 1.2 and 1.6 and different Al/Si molar ratios of 0, 0.06 and 0.18 for each series. Furthermore, the impact of synthesis temperature (room temperature, 100 °C, 200 °C) on the C-(A-)S-H structure was studied. The U(VI) retention, studied either by sorption experiments or by direct synthesis of U(VI)-containing C-(A-)S-H phases, was found to be strong with log <em>R</em>_d between 4.9 and 5.6. Structural characteristics of the cementitious phases were obtained from powder X-ray diffraction (XRD) as well as ²⁹Si and ²⁷Al solid-state magic angle spinning nuclear magnetic resonance (SS MAS NMR) spectroscopy. AlO₄ tetrahedra were identified to occupy bridging positions of the silicate chains, thereby increasing the mean chain length and providing additional sorption sites for U(VI) at room temperature. Elevated temperatures during solid phase formation, however, lead to a stronger cross-linking of the silicate chains with the appearance of neoformed crystalline phases. Luminescence spectroscopy was applied to characterize the U(VI) binding. Various U(VI) species (interlayer or surface sorbed) are formed in different proportions, depending on the composition and structure of the C-(A-)S-H phases, which are partly affected by elevated temperatures. To simulate salinity changes of the pore water, the effect of enhanced ionic strengths and the presence of carbonate on the stability of the U(VI) retention by the C-(A-)S-H phases was studied by sorption and leaching experiments over extended timescales of up to 6 months. For C-(A-)S-H phases previously exposed to temperatures of up to 100 °C, the effect of medium ionic strengths (up to 2.6 M) on U(VI) retention was insignificant.</div></div>","PeriodicalId":8064,"journal":{"name":"Applied Geochemistry","volume":"186 ","pages":"Article 106400"},"PeriodicalIF":3.1,"publicationDate":"2025-04-21","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143898554","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}