Applied Geochemistry最新文献

{"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":"Long-term use of an osmotically pumped fluid sampler at the Torigakubi Spur in the Japan Sea, an active venting field associated with gas hydrates","authors":"Satoko Owari ,&nbsp;Hitoshi Tomaru ,&nbsp;Ryo Matsumoto","doi":"10.1016/j.apgeochem.2025.106578","DOIUrl":"10.1016/j.apgeochem.2025.106578","url":null,"abstract":"<div><div>The combination of CH₄ venting and gas hydrate occurrence on the seafloor was observed by a remotely operated vehicle (ROV) offshore Joetsu, on the eastern margin of the Japan Sea. The intensity and location of venting varied within a few days, suggesting the potential for short-term gas hydrate formation and rapid geochemical changes. To investigate temporal variations in gas hydrate dynamics, we deployed a long-term in situ water sampling system (OsmoSampler), consisting of a pump and a sampling coil, next to the vent to collect interstitial water continuously for a year. However, the volume recovered from the sample was only a quarter of the expected amount. The presence of gas hydrate was confirmed in the OsmoSampler during its recovery by ROV. This unexpected event was attributed to a CH₄ intrusion into the system—either by direct intake through the tip of sampling coil or by a structurally vulnerable connections—followed by gas hydrate formation with the prefilled distilled water. The resulting blockage reduced the rate of sampling.</div><div>Despite this technical limitation, OsmoSampler geochemical data revealed dynamic variations. Cl⁻ concentrations sporadically fluctuated from 50 to 900 mM repeatedly until 40 m of coil length, indicating alternately saline and fresh conditions likely due to repeated cycles of gas hydrate growth and dissociation. At 40 m, a distinct geochemical transition—marked by an increase in Cl⁻ and SO₄^2- concentrations to 440 mM and 26 mM, respectively, and a sharp decline in CH₄ to 0 mM—closely resembled to the composition of surface interstitial water. This suggests that seawater infiltration into the sampling system was likely triggered by the collapse of the gas hydrate due to buoyancy. The topographic depression observed by the ROV during the recovery supports this interpretation. These findings provide new insights into short-term gas hydrate instability near the seafloor and the sudden release of CH₄ from sediments into the overlying water column.</div></div>","PeriodicalId":8064,"journal":{"name":"Applied Geochemistry","volume":"194 ","pages":"Article 106578"},"PeriodicalIF":3.4,"publicationDate":"2025-09-25","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145360154","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":"Changing isotope compositions of Mg, Ca and Sr in bulk crystalline rocks toward the weathering front: Disentangling inputs of geogenic base cations into ecosystems","authors":"Martin Novak ,&nbsp;Yulia V. Erban Kochergina ,&nbsp;Chris Holmden ,&nbsp;Alexandre V. Andronikov ,&nbsp;Vaclav Kachlik ,&nbsp;Jana Kotkova ,&nbsp;Irina E. Andronikova ,&nbsp;James W. Kirchner ,&nbsp;Jakub Hruška ,&nbsp;Frantisek Veselovsky ,&nbsp;Frantisek Laufek ,&nbsp;Ondrej Pour ,&nbsp;Marketa Stepanova ,&nbsp;Ondrej Sebek ,&nbsp;Tomas Paces ,&nbsp;Tereza Grabműllerova ,&nbsp;Jan Curik ,&nbsp;Eva Prechova ,&nbsp;Elena Antalova ,&nbsp;Ivana Vanisova ,&nbsp;Arnost Komarek","doi":"10.1016/j.apgeochem.2025.106577","DOIUrl":"10.1016/j.apgeochem.2025.106577","url":null,"abstract":"<div><div>Quantification of geogenic inputs of magnesium (Mg) and calcium (Ca) as essential nutrients, and strontium (Sr) as a Ca proxy, into biomass and catchment runoff is indispensable for studies of forest sustainability in an era of persisting acidification and climatic change. Supergene processes control the isotope composition of base cations released from bedrock into solution. Isotope signatures of dissolved Mg²⁺, Ca²⁺ and Sr²⁺ are complementary to the isotope composition of weathered rock because both are derived from the same parent material. We investigated shifts in δ²⁶Mg, δ⁴⁴Ca, and ⁸⁷Sr/⁸⁶Sr isotope ratios from fresh bedrock toward the weathering front in six common crystalline lithologies, including leucocratic granite, quartz diorite, melasyenite, melagranite, augen gneiss and amphibolite. About 20 cm below the deepest soil horizon, the isotopic composition of Mg, Ca and Sr in weathered rock differed significantly from that of fresh rock in nine out of 18 cases. Bulk-rock δ²⁶Mg and δ⁴⁴Ca values were less sensitive to partial dissolution of minerals than ⁸⁷Sr/⁸⁶Sr ratios. Statistically significant shifts in ⁸⁷Sr/⁸⁶Sr were observed in all six lithologies. Weathered rock had higher ⁸⁷Sr/⁸⁶Sr ratios than fresh rock in three cases, and lower ⁸⁷Sr/⁸⁶Sr ratios in another three cases. The site-specific ⁸⁷Sr/⁸⁶Sr shift was explained by contrasting weathering rates of Rb-rich and Rb-poor minerals in most rocks. Both lower δ²⁶Mg and higher δ⁴⁴Ca values of weathered amphibolite were likely related to isotope fractionations accompanying <em>in-situ</em> formation of secondary smectite. Continuing mineral dissolution in overlaying soils may cause additional Mg, Ca and Sr isotope effects.</div></div>","PeriodicalId":8064,"journal":{"name":"Applied Geochemistry","volume":"193 ","pages":"Article 106577"},"PeriodicalIF":3.4,"publicationDate":"2025-09-25","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145262926","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":"Sources of element release from acid sulfate soils to the environment: Elemental and mineralogical evidence from Northern Sweden","authors":"Federico Alvarellos,&nbsp;Katerina Rodiouchkina,&nbsp;Sarah Conrad,&nbsp;Björn Öhlander,&nbsp;Lena Alakangas","doi":"10.1016/j.apgeochem.2025.106571","DOIUrl":"10.1016/j.apgeochem.2025.106571","url":null,"abstract":"<div><div>Acid sulfate soils (AS-soils) are sulfide-bearing sediments that remain benign in waterlogged conditions but become environmentally harmful after exposure to oxygen. Sulfide oxidation generates acidity, element mobilization, compositional changes in soils and water bodies, and adverse effects on biota. This study enhances the geochemical and mineralogical understanding of the element source in oxidized and unoxidized AS-soils samples from Luleå, northern Sweden. An adapted sequential extraction scheme was conducted to determine the element distribution in primary and secondary phases. The extraction differentiates the H₂O-soluble from the exchangeable fraction, labile and stable organic fractions, differentiated reducible from oxidisable phases, and residual fractions. Mineralogical changes were monitored at each step of the extraction sequence. Compositional maps obtained through microprobe quantified trace elements within the pyrite structure, which are susceptible to mobilization after weathering. The mineralogical and compositional findings of this study support strategies to mitigate environmental impacts from AS-soils oxidation. It is shown that framboidal pyrites are highly reactive to oxidation, contributing to acidification and releasing elements such as Cu, Mn, Mo, and Ni, highlighting sulfide exposure risk. In unoxidized samples, S is present in primary Fe sulfides and as organic S, while in oxidized samples, S occurs as secondary sulfate minerals. Organic matter strongly associates with Cu, Mo, and S, and is an important source of these elements in the sediments. From the most labile phases and pore water, Cd, Mn, Mo, and S were predominantly leached, indicating their high bioavailability. These findings demonstrate the importance of maintaining AS-soils in waterlogged conditions to prevent acidification and metal mobilization.</div></div>","PeriodicalId":8064,"journal":{"name":"Applied Geochemistry","volume":"193 ","pages":"Article 106571"},"PeriodicalIF":3.4,"publicationDate":"2025-09-23","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145262923","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}