Applied Geochemistry最新文献

{"title":"Sorption of Eu(III) on C–S–H phases in the presence of gluconate: A molecular dynamics study","authors":"Iuliia Androniuk,&nbsp;Rosa Ester Guidone,&nbsp;Marcus Altmaier,&nbsp;Xavier Gaona","doi":"10.1016/j.apgeochem.2025.106579","DOIUrl":"10.1016/j.apgeochem.2025.106579","url":null,"abstract":"<div><div>Cement is a key barrier material in radioactive waste repositories, where calcium-silicate-hydrate (C–S–H) phases play a central role in immobilizing cationic radionuclides. However, organic ligands, originating from additives or waste, can enhance radionuclide mobility by forming soluble complexes and competing for surface sorption. In this study, a surface model was developed that combines experimental observations with theoretical insights into C–S–H structure, enabling detailed sampling of the most probable sorption sites. Molecular dynamics (MD) simulations and potential of mean force (PMF) calculations were used to develop molecular-scale understanding of how organic additives influence the adsorption and mobility of trivalent actinides and lanthanides in cementitious materials. Eu(III) was considered as a model of key trivalent radionuclides expected in nuclear waste, <em>i.e.</em> Pu(III) and Am(III), based on their similar charge-to-size (<em>z</em>/<em>d</em>) ratios, and gluconate was chosen as a model organic ligand. The results from the Eu(III)/C–S–H binary system confirmed strong sorption and showed that the most common sorption sites are the deprotonated silanol groups of the surface. Results obtained for the binary system are in line with Time Resolved Laser Fluorescence Spectroscopy data available for Eu(III) and Cm(III). Depending on gluconate concentration, two main effects on Eu(III) uptake on the C–S–H phases have been found: (a) sorption of the 1:1 Eu(III)-GLU complex at low ligand concentration; (b) formation of a stable ternary Ca–Eu(III)-GLU aqueous complex that does not sorb at high ligand concentration. It is important to consider formation of the ternary complex C–S–H/Eu(III)/GLU for the overall interpretation and understanding of the system.</div></div>","PeriodicalId":8064,"journal":{"name":"Applied Geochemistry","volume":"193 ","pages":"Article 106579"},"PeriodicalIF":3.4,"publicationDate":"2025-09-27","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145217437","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":"Characterisation, concentration and acidic reductive leaching of limonitic laterites from New Caledonia","authors":"Agathe Hubau ,&nbsp;Agnieszka Dybowska ,&nbsp;Paul F. Schofield ,&nbsp;Diego Gianolio ,&nbsp;Ana Santos ,&nbsp;Richard J. Herrington ,&nbsp;Douglas Pino-Herrera ,&nbsp;Hafida Tris ,&nbsp;Marion Erard ,&nbsp;Anne-Gwénaëlle Guezennec","doi":"10.1016/j.apgeochem.2025.106569","DOIUrl":"10.1016/j.apgeochem.2025.106569","url":null,"abstract":"<div><div>This study aimed at determining Ni and Co leaching kinetics from a New Caledonian laterite in an acidic medium (H₂SO₄ pH 1.5) and in a reductive environment (addition of SO₃²⁻ or Fe(II)) at 46 °C. The mineralogical study revealed that Co was mainly carried by Mn oxyhydroxides in the limonite sample. Conversely, Ni was hosted by both Fe and Mn oxyhydroxides. In the presence of a reductive reagent, Mn oxyhydroxides dissolved rapidly compared to goethite, the main Fe oxyhydroxide in the sample. Co, Mn and Ni reductive leaching yields reached 79 %, 83 % and 9 % respectively after 2 days. Based on these results, a Mn oxides concentrate was produced in order to efficiently leach Co while limiting Fe oxyhydroxide dissolution. This concentrate resulted from a combination of particle size and gravity separation steps. The volume/mass of sample was drastically decreased since the mass of the final sample was only 3.3 % of the initial one. Co content increased from 0.16 wt% in the limonite to 2.3 wt% in the concentrate, representing an enrichment factor of 13.8 and recovery yield of 60 %. Co, Mn and Ni leaching yields reached 87 %, 95 % and 80 % respectively in the Mn oxides concentrate leaching experiment. The difference in Ni behaviour was consistent with the mineralogical composition: Ni was mainly carried by the goethite in the laterite, while it was hosted mainly by the Mn oxyhydroxides in the Mn oxides concentrate. This study gives a proof of concept for the development a robust pre-concentration process to recover Co.</div></div>","PeriodicalId":8064,"journal":{"name":"Applied Geochemistry","volume":"193 ","pages":"Article 106569"},"PeriodicalIF":3.4,"publicationDate":"2025-09-26","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145217438","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":"Variability of effective diffusivity in fractured and mineralized metamorphic host rock from Bukov URF, Bohemian Massif (CZ)","authors":"Wenyu Zhou ,&nbsp;Johannes Kulenkampff ,&nbsp;Milan Zuna ,&nbsp;Filip Jankovský ,&nbsp;Christoph Butscher ,&nbsp;Robin Kammel ,&nbsp;Thorsten Schäfer ,&nbsp;Cornelius Fischer","doi":"10.1016/j.apgeochem.2025.106574","DOIUrl":"10.1016/j.apgeochem.2025.106574","url":null,"abstract":"<div><div>Crystalline rocks are considered host rocks for high-level radioactive waste (HLW) disposal because of their mechanical, thermal, and chemical properties. However, fractures and associated mineral precipitates, e.g. calcite, introduce significant heterogeneity that complicates predictions of radionuclide (RN) transport in fractured crystalline rock systems. This study combines positron emission tomography (PET) imaging and transport modeling to investigate the effects of calcite-filled fractures on predominantly diffusive transport in crystalline rocks. Diffusion experiments using a conservative iodine tracer (¹²⁴I) were performed on rocks from the BUKOV underground research facility (Czech Republic), and CT-based calcite-filled fracture geometries were incorporated into RTM simulations. The results show two types of transport modifications due to calcite precipitation in fractures: enhanced transport in porous calcite generations and suppressed transport in low-porosity calcite fracture fillings. The spatial distribution of fracture-filling calcite, its porosity, and the porosity of the surrounding matrix materials can lead to heterogeneous or anisotropic diffusion behavior. This suggests that important transport characteristics in heterogeneous systems may be overlooked by conventional modeling using homogenized diffusion coefficients. The apparent diffusivity of the fractured and variously sealed BUKOV rock ranges from 10⁻¹³ to 10⁻¹⁰ m²/s. We conclude that exploiting the variability and anisotropy of diffusive flux behavior is beneficial for improving the accuracy of RN migration predictions in fractured and mineralized crystalline rock systems. This work demonstrates the value of integrating advanced imaging and modeling techniques to better characterize solute transport in fractured crystalline host rocks.</div></div>","PeriodicalId":8064,"journal":{"name":"Applied Geochemistry","volume":"193 ","pages":"Article 106574"},"PeriodicalIF":3.4,"publicationDate":"2025-09-25","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145217541","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":"Mineralogical controls on rare earth element redistribution and enrichment: A study from the Franklin Mining District, New Jersey","authors":"Nathan Roden,&nbsp;Shelby Rader","doi":"10.1016/j.apgeochem.2025.106576","DOIUrl":"10.1016/j.apgeochem.2025.106576","url":null,"abstract":"&lt;div&gt;&lt;div&gt;Rare earth elements (REEs) are in high demand as they are crucial in our transition to renewable, green energy sources. As such, quantifying how REEs may substitute at the trace level (&lt;1000 ppm or &lt;0.1 wt%) and in which minerals will provide a framework for exploration of low concentration deposits where REEs may be a byproduct of primary mineralization, establish more efficient extraction techniques during mining, and help sustain our growing demand for critical elements. This study identifies REE concentrations within key minerals from the Franklin Mining District in Franklin, New Jersey, a locale with more than 400 unique mineral species. The area provides an ideal location to evaluate mineralogical and crystal chemistry controls and how they may influence trace-level REE substitution and partitioning.&lt;/div&gt;&lt;div&gt;Here, we identify silicates that contain VIII- to XII-fold coordination sites and large cations such as calcium (Ca) have enriched concentrations of light REEs (LREE) ([LREE] ranging from 160 to 730 ppm) when compared to the upper continental crust (UCC). In some cases, there is more than five times enrichment; beyond silicates no other mineral group analyzed showed LREE enrichment. On the other hand, heavy REE (HREE) enrichment was observed across multiple mineral groups: silicates (six of 32 minerals, [HREE] ranging from 11 to 110 ppm), carbonates (two of six minerals, [HREE] ranging from 16 to 18 ppm), and an oxide (one of five minerals, [HREE] = 18 ppm) demonstrated HREE enrichment. As of 2025, processing REEs contained within silicates is more costly and has lower recovery efficiencies at an industrial scale when compared to processing REEs from more common REE-bearing phases such as fluorocarbonates (bastanäsite) and phosphates (monazite). Across mineral groups, those that formed as a result of water-rock interactions (hydrothermal alteration and supergene processes) and that contained moderate-to large- (VI to XII) coordination sites were more likely to contain enriched concentrations of HREE compared to the UCC, in some cases being enriched by more than an order of magnitude. Thallium (Tl) isotopes, which are highly sensitive to changes in redox conditions and can reflect water-rock interactions, show no clear correlation with [REE] enrichment, but there is a general trend toward more positive Tl isotope compositions (denoted as ε&lt;sup&gt;205&lt;/sup&gt;Tl) with REE-enriched minerals (ε&lt;sup&gt;205&lt;/sup&gt;Tl ≥ 0 for all enriched samples, ε&lt;sup&gt;205&lt;/sup&gt;Tl ranges from 0.0 to 5.7). However, Tl isotopes may be useful to track processes that remobilize and deplete REE. We show that areas which experienced syn- or post-depositional metamorphism tend to be depleted in REE, likely a reflection of their incompatibility, and have significantly lower ε&lt;sup&gt;205&lt;/sup&gt;Tl values (ε&lt;sup&gt;205&lt;/sup&gt;Tl ranges from −5.2 to −0.1). Coupled mineralogical [REE] and non-traditional stable isotope data demonstrate the need for a firm understanding of b","PeriodicalId":8064,"journal":{"name":"Applied Geochemistry","volume":"193 ","pages":"Article 106576"},"PeriodicalIF":3.4,"publicationDate":"2025-09-24","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145155783","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":"SAFT2 equation of state for the CH4–CO2–H2S–H2O–NaCl quinary system","authors":"Zhida Zuo ,&nbsp;Chen Zhu ,&nbsp;Xiaoyan Ji","doi":"10.1016/j.apgeochem.2025.106573","DOIUrl":"10.1016/j.apgeochem.2025.106573","url":null,"abstract":"<div><div>Understanding the phase equilibria and physicochemical properties of the CH₄–CO₂–H₂S–H₂O–NaCl quinary system and its subsystems is essential for assessing fluid migration and changes in geological formations following CO₂ or acid gas injection. Moreover, this system is closely associated with a large percentage of geological fluids responsible for transport, mass transfer, and the formation of critical mineral ore deposits. In this study, a statistical associating fluid theory (SAFT)-based equation of state (EOS) was developed to investigate phase equilibria and thermodynamic properties of the system over temperatures from 298 to 423 K, pressures up to 600 bar, and NaCl concentration up to 6 mol/kgH₂O. The model incorporated pure component and cross-interaction parameters from previous studies, along with CH₄–H₂S cross-interactions derived from experimental data in this work. The SAFT EOS reliably predicted the phase behavior of the CH₄–CO₂–H₂S and CH₄–CO₂–H₂S–H₂O systems, as validated against experimental data and other thermodynamic models. It also successfully predicted phase equilibria and densities for the CH₄–H₂S–H₂O–NaCl and CH₄–CO₂–H₂S–H₂O–NaCl systems across a NaCl concentration range of 0–6 mol/kgH₂O. This study provides the first systematic development of a SAFT-based model for the CH₄–CO₂–H₂S–H₂O–NaCl system, demonstrating reliable performance in characterizing their phase behavior and thermodynamic properties.</div></div>","PeriodicalId":8064,"journal":{"name":"Applied Geochemistry","volume":"193 ","pages":"Article 106573"},"PeriodicalIF":3.4,"publicationDate":"2025-09-24","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145217439","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":"Roles of natural organic matter in fixing uranium: Evidences from uranium oxidation state and functional groups of organic matter","authors":"Fan Zhang ,&nbsp;Raymond Michels ,&nbsp;Yangquan Jiao ,&nbsp;Liqun Wu ,&nbsp;Hui Rong ,&nbsp;Yang Liu ,&nbsp;Jianying Wang","doi":"10.1016/j.apgeochem.2025.106575","DOIUrl":"10.1016/j.apgeochem.2025.106575","url":null,"abstract":"<div><div>Carbonaceous debris (CD) dispersed in sandstones closely coexists with uranium (U) mineralization in the Diantou-Shuanglong and Dongsheng uranium deposits, Ordos Basin, China. The occurrence states of element U within uranium-rich CD were investigated by using X-ray Photoecectron Spectroscopy (XPS), Scanning Electron Microscope (SEM), Electron Microprobe Analysis (EMPA) and Fourier Transform Infrared Spectrometer (FTIR) analyses. The results show that uranium content is up to 200338 ppm, and bears a positive relationship with total organic carbon (TOC). Moreover, U(Ⅵ) and U(Ⅳ) are both detected, and U(Ⅵ) is dominant, accounting for 76.49 %. Uranium minerals mostly occur in cell pores and fractures of CD in the forms of colloidal or fibrous shapes and microsome. Besides, adsorbed state of uranium is partially dispersed in matrix. According to the correlation of TOC and U(Ⅵ) (R² = 0.7), it is thought that a part of U(Ⅵ) is related to absorption of CD, and another part is associated with uranium minerals, which is also supported by the existences of complex uranium oxide detected by FTIR. Moreover, carboxyl group bears a positive relationship with U(Ⅵ). Besides, pyrites are unevenly altered by uranium minerals. The coexistences of autunite and pyrite support that the pyrites have an enhanced effect on the reduction of U (VI) and microbial activities exist. Hence, it is comprehensively that CD directly contributes to uranium precipitation and enrichment, accompanying with the participation of pyrite and microbial activities. Compared with hydroxyl group, carboxyl groupis more favorable for U(Ⅵ) absorption.</div></div>","PeriodicalId":8064,"journal":{"name":"Applied Geochemistry","volume":"193 ","pages":"Article 106575"},"PeriodicalIF":3.4,"publicationDate":"2025-09-24","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145217441","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":"Groundwater resources assessment in the Mirandiba sedimentary Basin at NE Brazil","authors":"Thyego R. Silva ,&nbsp;Mariucha M. Correia de Lima ,&nbsp;Tiago N. Martins ,&nbsp;Waldir D. Costa ,&nbsp;Mateus S.C. Albuquerque ,&nbsp;Manoel Júlio da T.G. Galvão","doi":"10.1016/j.apgeochem.2025.106572","DOIUrl":"10.1016/j.apgeochem.2025.106572","url":null,"abstract":"<div><div>In semi-arid regions, groundwater is a vital water resource threatened by salinization and contamination. Geophysical and the physicochemical and isotopic compositions (δ¹⁸O and δ²H) are investigated to determine the general geometrical characteristics of a closed basin and identify the origin and main evolutionary processes controlling the groundwater geochemistry and quality to provide reliable information for effective water management. The studied dominantly unconfined Mirandiba Basin lacks evaporitic (halite) deposits but contains comparatively higher chloride concentration, under the role of the semi-arid climate of NE Brazil. Geophysics unravels a shallow basin with a thickness lower than 400 m and a basement morphology suggesting a half-graben structure. Groundwater samples were classified into three groups: 1) cluster 1 samples correspond to more mineralized mixed cations–Cl to Na–Cl slightly acid waters, 2) cluster 2 samples correspond to less mineralized Na–Cl acid waters, and 3) cluster 3 samples correspond to neutral mixed cations-mixed anions waters. The isotopic signatures range from −4.95 to −3.16 ‰ and – 29.74 to −17.50 ‰ for δ¹⁸O and δ²H, respectively, indicating that groundwater is derived from rainwater with some samples suggesting evaporation. The integrated techniques have shown that the main factors controlling groundwater chemistry evolution are related to 1) wetting/evaporation that induced millennial cyclic salt (mainly halite) accumulation and later dissolution and leaching during recharge periods, 2) rock weathering, 3) reverse ion exchange, and 4) anthropogenic nitrate contamination. The physicochemical parameters of ∼90 % of groundwater samples are within the WHO guidelines, and ∼92 % within the good and excellent water quality category for drinking purposes. Similarly, irrigation ion-based indices showed overall suitability for irrigation. The approach followed in this study is useful for recognize the main processes (natural and anthropogenic) operating in groundwater, and was used to build a conceptual hydrogeologic model, for establishing effective management strategies in aquifers in arid to semi-arid areas.</div></div>","PeriodicalId":8064,"journal":{"name":"Applied Geochemistry","volume":"193 ","pages":"Article 106572"},"PeriodicalIF":3.4,"publicationDate":"2025-09-23","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145155782","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":"Compositional analysis of the relationships between the organic matter content and chemical and physical properties of soil","authors":"Matthias Templ ,&nbsp;Christoph Hofer","doi":"10.1016/j.apgeochem.2025.106526","DOIUrl":"10.1016/j.apgeochem.2025.106526","url":null,"abstract":"<div><div>Soil organic matter (SOM) plays a crucial role in soil fertility, carbon sequestration, and ecosystem sustainability, making its accurate analysis essential for environmental and agricultural management. However, studying the relationships between soil organic matter content (SOMC) and its influencing factors remains challenging due to the compositional nature of soil constituents. This study addresses key methodological challenges in analyzing the relationships between SOMC and soil texture, chemical composition, and bulk density using compositional data analysis. Specifically, we solve methodological issues related to integrating compositional and non-compositional variables in regression modeling and apply, for the first time, compositional data analysis to a mix of compositions, including the SOMC composition. The study explores the multivariate dependencies of the log-ratio coordinates—transformations that map compositional data from the constrained simplex space to real space—of major chemical elements in the soil and their relationship to log-ratio coordinates of SOMC. To appropriately account for the compositional nature of both the chemical element composition and soil texture, compositional data analysis methods are employed. Additionally, since outliers are common in soil data, all estimations are carried out using robust estimation methods. The application focuses on topsoil in the canton of Zurich (Switzerland), providing new insights into these relationships. Some findings contrast with previous studies that did not adopt a compositional approach, revealing, for example, a weak positive association between calcium and SOMC, a positive effect of phosphorus, and a decreasing dominance of organic matter in soil texture with increasing bulk density. Furthermore, free and open-source software has been extended to enable linear regression modeling that integrates both compositional and non-compositional explanatory variables, offering a practical solution to these methodological challenges in soil science.</div></div>","PeriodicalId":8064,"journal":{"name":"Applied Geochemistry","volume":"193 ","pages":"Article 106526"},"PeriodicalIF":3.4,"publicationDate":"2025-09-23","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145155781","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":"Radiocarbon age dating and quality evolution of seawater intruding beneath a freshwater lens","authors":"Pieter J. Stuyfzand ,&nbsp;Philip R. Nienhuis ,&nbsp;Vincent E.A. Post","doi":"10.1016/j.apgeochem.2025.106564","DOIUrl":"10.1016/j.apgeochem.2025.106564","url":null,"abstract":"<div><div>Radiocarbon has been used in a number of studies to establish the age of intruded seawater, yet there appears to be a paucity of investigations that has attempted to quantify the processes that influence radiocarbon along the flow path of actively intruding seawater. The present study contributes to filling this research gap using radiocarbon and hydrochemical data of intruding North Sea water along two shore-perpendicular transects across the coastal dune belt of the western Netherlands. The objective is to establish how well radiocarbon can be used to determine the intruding seawater's age, considering the corrections that are required to account for geochemical reactions and mixing.</div><div>The effect of geochemical reactions was quantified for each of the 18 samples of intruded seawater based on a chemical mass balance calculated with a new Excel based code (R + SWi). It considers 20 quality parameters (including δ¹³C_DIC and ¹⁴C_DIC) and 15 reactions and utilizes Excel's Solver routine to calibrate the model parameters. The reactions along the flow path are initially dominated by O₂ and NO₃ reduction by sediment organic matter in seafloor sediment, with little CaCO₃ dissolution. Next, during passage of a Holocene tidal aquitard, Fe(OH)₃ and some SO₄ are reduced, pyrite and CaCO₃ precipitate, and opaline SiO₂ dissolves. In deeper, Pleistocene aquitards and further downgradient in aquifers, cations are exchanged, some CaCO₃ precipitates due to Ca exchange, and siderite dissolves.</div><div>Correcting radiocarbon concentrations for the calculated sedimentary carbon contributions yields ages between 0.37 and 6 ka. Sensitivity analysis reveals that the corrected ¹⁴C age is most sensitive to the assumed ¹⁴C activity of the carbonate and organic matter of the Holocene seabed sediments. The intruded seawater's age appears to be bimodal: Old seawater (3–6 ka) intruded when the coastline was located much further to the east than at present. Younger seawater (&lt;3 ka) started to intrude after the freshwater lens developed when the coastline had reached its present-day position. Groundwater extraction and especially the reclamation of the Haarlemmermeer lake accelerated intrusion rates massively.</div><div>The results of a 3.5 ky numerical model simulation of freshwater lens formation and seawater intrusion are consistent with the radiocarbon age pattern inferred from the samples. The spatial distribution of seawater ages indicates a higher vulnerability to salinization in the northern part of the study area, highlighting the added value of radiocarbon data of saline groundwater for water resource management purposes.</div></div>","PeriodicalId":8064,"journal":{"name":"Applied Geochemistry","volume":"193 ","pages":"Article 106564"},"PeriodicalIF":3.4,"publicationDate":"2025-09-17","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145119343","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":"Coastal SOM degradation regulates the transformation of iron in mangrove sediments and its environmental significance","authors":"Lu Yan ,&nbsp;Jingxian Zhang ,&nbsp;Xianjun Xie ,&nbsp;Kang Peng ,&nbsp;Yamin Deng ,&nbsp;Yiqun Gan ,&nbsp;Qinghua Li ,&nbsp;Yanpeng Zhang","doi":"10.1016/j.apgeochem.2025.106568","DOIUrl":"10.1016/j.apgeochem.2025.106568","url":null,"abstract":"<div><div>Iron (Fe), a key micronutrient, plays a vital role in governing the health and services of mangrove ecosystems. However, the migration and transformation of Fe induced by sedimentary organic matter (SOM) in mangrove wetlands remains unclear. Here, we investigated the Fe biogeochemical processes and effects of SOM components on Fe behaviors in mangrove surface sediments from Dongzhai Harbor, Hainan Island, using sequential extractions of Fe species and spectroscopic techniques. The results showed that most of the Fe species were amorphous oxides (Fe_OX1), crystalline (Fe_OX2), and ferrosilicate (Fe_PRS) in mangrove sediments. The EEM-PARAFAC model successfully identified four fluorescent components: three humic-like components (C1, C2, and C3) and one protein-like component (C4). Terrestrial humic substances have the potential to immobilize Fe_OX1, Fe_OX2, magnetite, and Fe_PRS through adsorption, complexation, and co-precipitation. Microbial degraded humic-like materials may facilitate Fe transformation in the presence of microorganisms while concurrently engaging in the cycling of nitrogen and phosphorus. The processes potentially lead to increased nutrient levels in the overlying water and eutrophication. These findings offer insights into the Fe-SOM couple biogeochemical cycling processes in mangrove sediments, further providing valuable guidance for the ecological conservation of mangrove wetlands.</div></div>","PeriodicalId":8064,"journal":{"name":"Applied Geochemistry","volume":"193 ","pages":"Article 106568"},"PeriodicalIF":3.4,"publicationDate":"2025-09-16","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145099643","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}