Applied Geochemistry最新文献

{"title":"Sulfate availability affect sulfate reduction pathways and methane consumption in freshwater wetland sediments","authors":"Hao Xue ,&nbsp;Yunchao Lang ,&nbsp;Hu Ding ,&nbsp;Xiaokun Han ,&nbsp;Tiejun Wang ,&nbsp;Zhanhang Liu ,&nbsp;Wei La ,&nbsp;Cong-Qiang Liu","doi":"10.1016/j.apgeochem.2024.106215","DOIUrl":"10.1016/j.apgeochem.2024.106215","url":null,"abstract":"<div><div>Methane (CH₄) emissions from wetlands significantly contribute to global greenhouse gas fluxes, yet the mechanisms regulating CH₄ production and oxidation in freshwater wetlands remain underexplored, particularly in the role of sulfate in the anaerobic oxidation of CH₄. This study investigated the production, consumption, and release of CH₄ in the sediments of the Qilihai wetland, focusing on the roles of hydrogenotrophic methanogenesis and sulfate dynamics across different seasons. CH₄ concentrations ranged from 2.42 to 2290.52 μmol L⁻¹, and δ¹³C–CH₄ values became progressively more negative with depth, ranging from −87.37‰ to −57.18‰. Results indicate that hydrogenotrophic methanogenesis is the dominant pathway for CH₄ production, particularly in sulfate-depleted environments, with CH₄ concentrations in the sulfate-methane transition zone (SMTZ) strongly correlated with sulfate availability. Sulfate consumption through Sulfate Anaerobic Oxidation of Methane (SAOM) and Organoclastic Sulfate Reduction (OSR) demonstrated significant seasonal variation, with OSR accounting for up to 73% of sulfate consumption in the SMTZ. The SMTZ exhibited variations ranging from 2 to 40 cm in October, narrowing to 2–4 cm in July. These findings emphasize the complex interactions between sulfate availability, methanogenic pathways, and CH₄ emissions in freshwater wetlands, highlighting the need for further research on sulfate dynamics and their implications for greenhouse gas emissions in the context of global climate change.</div></div>","PeriodicalId":8064,"journal":{"name":"Applied Geochemistry","volume":"176 ","pages":"Article 106215"},"PeriodicalIF":3.1,"publicationDate":"2024-11-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142578830","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":"Geochemical markers in the detection and identification of fossil fuels in waste material from an illegal landfill fire","authors":"Wojciech Rykała,&nbsp;Monika Fabiańska,&nbsp;Dominika Dąbrowska,&nbsp;Marek Sołtysiak","doi":"10.1016/j.apgeochem.2024.106214","DOIUrl":"10.1016/j.apgeochem.2024.106214","url":null,"abstract":"<div><div>Organic compounds, including <em>n</em>-alkanes, steranes, pentacyclic triterpanes, polycyclic aromatic hydrocarbons (PAHs), and alkyl aromatic hydrocarbons, often originate from industrial activities, vehicle emissions, used transformer oils, biomass combustion, and also natural organic matter. The unprotected surroundings of former industrial sites, especially those affected by fire, pose significant risks to public health and the environment, particularly soil and water. These compounds are also excellent geochemical markers for determining the material that was used to ignite the fire, including petroleum products, oils, greases, and gasoline. This study presents research findings from an illegal landfill in Sosnowiec, Poland, which caught fire in 2020, leading to the combustion of petroleum substances, plastics, and other waste. The study found PAH_sum concentrations ranging from 4.57 to 302.45 ppm in soil samples and from 3.04 to 27211.98 ppm in burnt solid waste samples, indicating significant contamination. The test results confirmed that the main sources of these pollutants in the analyzed research area were, among other things, greases, industrial oils, products from solid fuel processing, and coal waste. The use of pentacyclic triterpanes (hopanes and moretanes) seems to be the most effective diagnostic method to detect the presence of organic fossil fuels in waste samples. This research underscores the critical need to monitor and control illegal landfills to prevent fires and limit the exposure of communities and the environment to toxic pollutants. The methodologies applied here could be adopted globally to address soil and water pollution in similar contexts. By using these techniques, researchers could better interpret and manage environmental data, ultimately improving pollution control strategies worldwide.</div></div>","PeriodicalId":8064,"journal":{"name":"Applied Geochemistry","volume":"176 ","pages":"Article 106214"},"PeriodicalIF":3.1,"publicationDate":"2024-11-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142593086","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":"Magmatic and rock-leaching contributions to the metal load in hydrothermal fluids at þeistareykir, Iceland","authors":"Marion Saby ,&nbsp;Vincent van Hinsberg ,&nbsp;Daniele L. Pinti ,&nbsp;Kim Berlo ,&nbsp;Bjarni Gautason ,&nbsp;Ásgerður Sigurðardóttir ,&nbsp;M. Clara Castro","doi":"10.1016/j.apgeochem.2024.106213","DOIUrl":"10.1016/j.apgeochem.2024.106213","url":null,"abstract":"<div><div>Magmatic-hydrothermal systems are key environments to study the transfer of elements from the deep Earth to the surface and the mobilization and re-distribution of elements within the crust. These systems have been recognized as potential active analogue sites for ore deposition. The source of fluids and their metal load is split between the relative contributions from degassing of underlying magma and interactions between the hydrothermal fluid and the host rock. Here, we combine analyses of noble gases and volatile metals in fluids and rocks from the þeistareykir geothermal field (NE Iceland) to provide constraints on the relative contribution of these two sources. Helium isotope data suggest 80–85% originated from magma degassing. The ³He/⁴He ratio, corrected for atmospheric contamination (Rc/Ra) correlates with volatile metal abundances in surface fluids and indicates that Bi and Hg are predominantly derived from magma degassing. It is also shown that the deep geothermal reservoir fluid is dominated by magmatic input, except for Mn, Fe, Co, Cu, Ti and V, using the elemental signature of magmatic degassing and water-rock interaction. The spatial variations in Rc/Ra and surface fluid volatile metal contents among the wells suggest an impact of the local and regional structures on the fluid's pathway from depth to surface.</div></div>","PeriodicalId":8064,"journal":{"name":"Applied Geochemistry","volume":"176 ","pages":"Article 106213"},"PeriodicalIF":3.1,"publicationDate":"2024-10-31","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142587029","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Sedimentary geochemistry in P-limited freshwater drained marshes (Charente-Maritime, France): Original drivers for phosphorus mobilization","authors":"Raphaël Moncelon ,&nbsp;Christine Dupuy ,&nbsp;Philippe Pineau ,&nbsp;Claire Emery ,&nbsp;Eric Bénéteau ,&nbsp;Olivier Philippine ,&nbsp;François-Xavier Robin ,&nbsp;Edouard Metzger","doi":"10.1016/j.apgeochem.2024.106200","DOIUrl":"10.1016/j.apgeochem.2024.106200","url":null,"abstract":"<div><div>Phosphorus bioavailability is a major issue in aquatic environments, where it generally limits primary production. In this work, the analysis of the pore water and the solid phase of the sediment was carried out over a 9-month monitoring period between February 2020 and April 2021 in two drained marshes (Marans and Genouillé, France) distinct by their uses and management tools. Soluble reactive phosphorus (SRP) enrichment in the sediment was intimately controlled by iron oxide dissolution. The latter seemed highly controlled by seasonal nitrate inputs (winter and early spring) that favoured denitrification as a major benthic mineralization process promoting iron curtain development and stability. Following benthic mitigation of nitrate other anaerobic metabolisms developed such as iron dissolutive reduction promoting P recycling and planktic bioavailability. Surprisingly, sulphur cycle seemed to affect P dynamics, especially in the absence of nitrate. The absence of NO₃⁻ triggered high sulphate reduction rates in the two first centimeters depth, reaching −8.9 E⁻⁰³ ± 0.5 E⁻⁰³ and -5.0 E⁻⁰³ ± 0.2 E⁻⁰³ nmol cm⁻³ s⁻¹ in August and July at Marans and Genouillé respectively. These values placed this process at higher rates than the denitrification (maximum in May at Marans with −5.0 E⁻⁰³ ± 1.1 E⁻⁰³ nmol cm⁻³ s⁻¹) and reduced iron production (maximum in July at Genouillé with 0.5 E⁻⁰³ ± 0.1 E⁻⁰³ nmol cm⁻³ s⁻¹). The rapidity with which process changes occur (monthly scale) testified to the dynamism of these systems. The similarity in geochemical patterns regarding NO₃⁻ pressure at both sites underlines the importance of diffuse pollution in coastal systems for nitrogen mitigation and phosphorus trapping. The results obtained in this study could lead to the development of a generalized diagenetic operating model for temperate systems with high agricultural pressure. This would enable to target management efforts to both optimize the purification function and limit eutrophication risks in these systems.</div></div>","PeriodicalId":8064,"journal":{"name":"Applied Geochemistry","volume":"176 ","pages":"Article 106200"},"PeriodicalIF":3.1,"publicationDate":"2024-10-28","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142663428","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Trace element partitioning between natural barite and deep anoxic groundwaters: Implications for radionuclide retention in host rocks of nuclear waste repositories","authors":"Ferdinand Kirchner ,&nbsp;Martin Kutzschbach ,&nbsp;Henrik Drake ,&nbsp;Vanessa Fichtner ,&nbsp;Piotr M. Kowalski ,&nbsp;Stefan Rudin ,&nbsp;Martin J. Whitehouse ,&nbsp;Mikael Tillberg ,&nbsp;Thomas Neumann","doi":"10.1016/j.apgeochem.2024.106208","DOIUrl":"10.1016/j.apgeochem.2024.106208","url":null,"abstract":"&lt;div&gt;&lt;div&gt;Safety assessments for deep geological repositories involve risk calculations for the release of radionuclides like Ra, U, Pu and trivalent actinides from the storage containers to the groundwater. The retention of radionuclides through water-mineral interaction along the groundwater flow path could be a crucial factor in case of a repository failure. Barite (BaSO&lt;sub&gt;4&lt;/sub&gt;) assumes significance in this context, as it has the potential to (re)crystallize and incorporate significant quantities of radioactive elements under relevant physico-chemical conditions.&lt;/div&gt;&lt;div&gt;The assessment of mineral-fluid partition coefficients provides a means to evaluate the uptake potential of elements into the mineral. Usually, partition coefficients are determined under well-defined and controlled experimental conditions in laboratories. However, these results have shown discrepancies to partitioning coefficients determined from natural systems.&lt;/div&gt;&lt;div&gt;Furthermore, effects like diagenesis or changes in the chemical fluid parameters might lead to a secondary alteration of the phases and affecting the retention ability.&lt;/div&gt;&lt;div&gt;Here we investigate the incorporation of trace elements in natural barite from a borehole at 415 m depth in the Äspö Hard Rock Laboratory (Sweden). High-resolution LA-ICP-MS enables the quantitative determination of field-based partition coefficients through the integrated pixel average of selected zones in element distribution maps, combined with existing fluid concentration data. Similarities between the solid solution systems (Ra,Ba)SO&lt;sub&gt;4&lt;/sub&gt; and (Sr,Ba)SO&lt;sub&gt;4&lt;/sub&gt; allowed the combination of Sr partitioning data with density-functional theory simulations for an estimation of the partition coefficient value for Ra in natural barite. Values in the 10&lt;sup&gt;−2&lt;/sup&gt; range were determined, showing a deviation from those reported in previous experimental studies in the 10° range.&lt;/div&gt;&lt;div&gt;Moreover, lanthanum serves as an analogue element for the radioactive trivalent actinides. The partition coefficient values for La in natural barite were determined in the range of 10&lt;sup&gt;−2&lt;/sup&gt; and 10&lt;sup&gt;−1&lt;/sup&gt;, aligning well with experimental partition coefficients. Although density functional theory simulations cannot directly convert a La partition coefficient into a partition coefficient for trivalent actinides, it is assumed that these elements exhibit comparable behavior. Besides primary growth zonation, La also exhibits strong secondary enrichment, probably resulting from groundwater mixing and late fluid-mediated element transport through connected intracrystalline pore space oriented at cleavage plane systems. Additional SIMS analysis provides insights into the temporal variation of the sulfate source at the sampling site reflecting the influence of different waters during mineral growth.&lt;/div&gt;&lt;div&gt;This study demonstrates a discrepancy between natural and synthetic &lt;em&gt;P&lt;/em&gt;&lt;sub&gt;Ra&lt;/sub&gt; for barite and emphasizes that s","PeriodicalId":8064,"journal":{"name":"Applied Geochemistry","volume":"176 ","pages":"Article 106208"},"PeriodicalIF":3.1,"publicationDate":"2024-10-28","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142553060","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Using hydrochemistry and stable isotopes to character the karst water environment in a cave site, South China","authors":"Fang Guo ,&nbsp;Guanghui Jiang ,&nbsp;Fan Liu ,&nbsp;Baokun Jing ,&nbsp;Peng Zhang","doi":"10.1016/j.apgeochem.2024.106198","DOIUrl":"10.1016/j.apgeochem.2024.106198","url":null,"abstract":"<div><div>For cave sites located within the seasonal fluctuation zone of groundwater, obtaining a comprehensive understanding of the hydrogeological conditions and hydrochemical environment is of utmost importance in assessing the preservation of cultural deposits. However, due to the heterogeneity of karst development, the hydrochemical environment of the overburden karst water-bearing unit may exhibit complex variations. In this study, the characteristics of the water environment in a foot cave system and its surrounding aquifer were investigated at the Zengpiyan site, employing hydrochemistry, hydrogen and oxygen isotope analysis, as well as sulfate isotope analysis, in conjunction with the hydrogeological background. Based on the exposure of the karst cave and the groundwater flow conditions, the water-bearing medium was categorized into five types. The aquifer exhibited either an oxidation or reduction condition, with a distinct “dissolved oxygen hole” observed in the saturated zone of the cave site. Ion concentration analysis revealed that the groundwater was influenced by the prior accumulation of cinders in the upstream region, leading to sulfate contamination within the foot cave system. However, during the groundwater movement from upstream to downstream, the attenuation rate of pollutants displayed significant variations. Notably, the sulfate content was unusually low within the site cave. Hydrogen and oxygen isotopes provided insights into the differing circulation and movement velocities of groundwater within the local environment. Additionally, sulfate isotopes confirmed the sources of sulfate and the occurrence of bacterial sulfate reduction within the site cave. Consequently, an environmental zoning classification was established based on these analyses. Although the concentration of dissolved ions appears low in the anoxic area, it does not imply a diminished environmental risk. Under reducing conditions, these pollutants can be converted into more aggressive gases, posing a substantial threat to the preservation environment of cave sites. Therefore, sufficient attention should be given to this aspect in order to ensure adequate protection.</div></div>","PeriodicalId":8064,"journal":{"name":"Applied Geochemistry","volume":"176 ","pages":"Article 106198"},"PeriodicalIF":3.1,"publicationDate":"2024-10-24","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142553063","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":"Tracing groundwater-surface water sources and transformation processes in the Ba River Basin through dual isotopes and water chemistry","authors":"Weijie Zhao ,&nbsp;Hui Qian ,&nbsp;Panpan Xu ,&nbsp;Shuhan Yang ,&nbsp;Yixin Liu ,&nbsp;Yanjun Shen ,&nbsp;Yongqi Zang ,&nbsp;Qiming Wang ,&nbsp;Zhiming Cao","doi":"10.1016/j.apgeochem.2024.106199","DOIUrl":"10.1016/j.apgeochem.2024.106199","url":null,"abstract":"<div><div>The interactions between groundwater and surface water, including their recharge dynamics and proportional contributions, are crucial for the hydrological cycling, water resource management, and pollution control. This study focused on the Bahe River basin, employing methods such as the Gibbs diagrams, the multivariate statistical analysis, and the MixSIAR model to analyze the hydrochemical parameters and the hydrogen-oxygen isotopes of both groundwater and surface water to quantitatively analyze the transformation relationships between water bodies. The results indicated that both the groundwater and surface water in the research area exhibited weak alkalinity, with the groundwater primarily characterized by HCO₃–Ca·Na and surface water predominantly by HCO₃–Ca. Furthermore, the geochemical evolution was predominantly affected by the rock weathering and the cation exchange processes. The distribution characteristics of hydrogen and oxygen isotopes in groundwater and surface water suggested that the atmospheric precipitation constituted the main source of recharge in the Bahe River basin. According to the MixSIAR model, the upstream groundwater contributed 90.1% to the surface water, with 9.9% attributed to the atmospheric precipitation. In the midstream, the atmospheric precipitation and groundwater contributed 21.9% and 78.1%, respectively, to the surface water. Downstream, the groundwater contributed significantly to the surface water (78.5%), whereas atmospheric precipitation contributed 28.5%. This study could provide a foundation for understanding the sources and evolution of groundwater and surface water, thereby promoting the effective management and utilization of groundwater resources.</div></div>","PeriodicalId":8064,"journal":{"name":"Applied Geochemistry","volume":"176 ","pages":"Article 106199"},"PeriodicalIF":3.1,"publicationDate":"2024-10-22","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142572225","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":"Source identification of nitrate in groundwater of an agro-pastoral ecotone in a semi-arid zone, northern China: Coupled evidences from MixSIAR model and DOM fluorescence","authors":"Anqi Chen ,&nbsp;Yao Du ,&nbsp;Zichen Wang ,&nbsp;Xiaoliang Sun ,&nbsp;Rui Xu ,&nbsp;Yaojin Xiong ,&nbsp;Liangping Yang ,&nbsp;Junting Liu ,&nbsp;Yiqun Gan","doi":"10.1016/j.apgeochem.2024.106197","DOIUrl":"10.1016/j.apgeochem.2024.106197","url":null,"abstract":"<div><div>In the extensive agro-pastoral ecotone of northern China, groundwater is a valuable resource, but it suffers from severe nitrate pollution. However, the extent of the contributions of agricultural and pastoral activities to nitrate accumulation in the groundwater of the region remains unclear. This study aimed to identify the main sources of groundwater nitrate in Chahannur Basin, a typical agro-pastoral ecotone in the semi-arid zone of northern China, using the MixSIAR model based on dual stable isotopes and dissolved organic matter (DOM) fluorescence. The hydrochemical and isotopic results showed that the groundwater has high concentrations of nitrate (up to 208.19 mg/L) with weak denitrification, and nitrate accumulation is mainly driven by mixed input from different sources. The MixSIAR model results indicated that the largest contributors to groundwater nitrate accumulation are manure &amp; sewage, followed by soil nitrogen, chemical fertilizers, and atmospheric deposition. According to the DOM fluorescence characteristics, the groundwater is strongly affected by livestock and poultry waste, followed by soil humic substances. Moreover, the <span>DOM</span> fluorescence results further supported the MixSIAR model results based on the significant correlation between the contributions of nitrate sources and the percentages of fluorescent components, jointly confirming that the main source of nitrate in groundwater is manure and sewage, followed by soil nitrogen. These findings indicate that coupled evidences from the MixSIAR model and DOM fluorescence could be applied to identify the sources of nitrate in groundwater, and this coupling can provide valuable information for local authorities to achieve sustainable groundwater management.</div></div>","PeriodicalId":8064,"journal":{"name":"Applied Geochemistry","volume":"175 ","pages":"Article 106197"},"PeriodicalIF":3.1,"publicationDate":"2024-10-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142533968","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":"Dissolution behavior of calcium uranate under oxidizing and reducing conditions","authors":"Yuto Kato ,&nbsp;Takayuki Sasaki ,&nbsp;Ryutaro Tonna ,&nbsp;Taishi Kobayashi ,&nbsp;Yoshihiro Okamoto","doi":"10.1016/j.apgeochem.2024.106196","DOIUrl":"10.1016/j.apgeochem.2024.106196","url":null,"abstract":"<div><div>Calcium uranate solid phase is a secondary mineral found in geological environments. It may form in the residues of high-level radioactive liquid waste and in the fuel debris of the TEPCO's Fukushima Daiichi Nuclear Power Plant under high-temperature conditions. To assess the chemical stability of CaUO₄ in different aqueous environments, static immersion tests were performed under various redox conditions and carbonate ion concentrations. pH and Eh values, as well as concentrations of uranium, calcium, and total carbonate in the solutions, were measured after the supernatants were filtered through a membrane with a 10 kDa molecular weight cutoff. The components of the solid phase were also evaluated using X-ray diffraction and X-ray absorption fine structure analyses. The dissolution mechanism of CaUO₄ was examined using data from solid and liquid analyses, along with chemical thermodynamic calculations. Under reducing conditions and without carbonate, U(VI) in CaUO₄ was reduced to U(V) and the mineral was converted into non-stoichiometric CaUO_{4−<em>x</em>}. The dissolved uranium was then further reduced to U(IV) in the aqueous media, forming UO₂(am), which controlled the U solubility. Under oxidizing conditions and in the absence of carbonate, dissolved uranium formed metaschoepite ((UO₃)·2H₂O(cr)) at pH ≤ 7 and sodium diuranate (Na₂U₂O₇·H₂O(cr)) at pH &gt; 7, which controlled uranium solubility. In oxidizing conditions with carbonate present, the apparent solubility of U was lower than predicted by the solid-phase solubility calculations. The concentration of U was constrained to levels similar to that of calcium when the calcium concentration reached saturation with CaCO₃. Additionally, the dissolution of calcium from CaUO₄ influenced uranium dissolution.</div></div>","PeriodicalId":8064,"journal":{"name":"Applied Geochemistry","volume":"175 ","pages":"Article 106196"},"PeriodicalIF":3.1,"publicationDate":"2024-10-13","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142533971","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":"Catalytic oxidation of Mn(II) on ferrihydrite and goethite surfaces and the subsequent oxidation and immobilization of coexisting Cr(III)","authors":"Rongrong Su ,&nbsp;Chunhui Li ,&nbsp;Minyu He ,&nbsp;Kangsheng Hu ,&nbsp;Zhangjie Qin ,&nbsp;Shuai Lan","doi":"10.1016/j.apgeochem.2024.106195","DOIUrl":"10.1016/j.apgeochem.2024.106195","url":null,"abstract":"<div><div>Semiconductor iron oxides, which are distributed in soils, always catalyze Mn(II) oxidation to produce various Fe–Mn binary oxides. They affect the migration and transformation of heavy metals, <em>i.e.</em>, Cr(III). However, the specific effect mechanisms of different catalytic oxidation pathways (<em>i.e.</em>, electrochemical or interfacial catalysis) of Mn(II) catalyzed by minerals possessing different characteristics on the oxidation of coexisting Cr(III) remains elusive. Therefore, this study aims to explore different Mn(II) oxidation processes on ferrihydrite and goethite surfaces as well as the subsequent oxidation of coexisting Cr(III) and Cr(VI) immobilization. Herein, long-time aging oxidation tests were performed combined with solution chemical analysis and various spectroscopic techniques such as X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS), to explore the Mn(II) catalytic oxidation behaviors on ferrihydrite and goethite surfaces under different pHs and initial Mn(II) reaction concentrations, as well as the oxidation products of Fe–Mn binary oxides. Subsequently, the oxidation mechanisms of Cr(III) by these different generated Fe–Mn binary oxides were studied. Results indicated that higher pH and initial reaction concentration of Mn(II) were more favorable for Mn(II) oxidation yielding more Mn oxides containing higher valence Mn. Additionally, goethite, which has better conductivity, showed stronger electrochemical catalysis effect for Mn(II) oxidation than ferrihydrite. Thus, more Mn(III) oxides were generated in goethite systems than in ferrihydrite systems. Fe–Mn binary oxides formed from higher Mn(II) oxidation rates and degrees exhibited more improved oxidative properties for Cr(III) and higher Cr(VI) fixation efficiencies than those obtained from lower reactions. These phenomena depended on the stronger oxidation and fixation effect of Mn(II) oxidation products with higher Mn valence states of Mn(III/IV) on Cr(III) and Cr(VI), respectively. Moreover, Mn(III) in Fe–Mn binary oxides exhibited considerably higher oxidation efficiency for Cr(III) than Mn(IV). In summary, high pH, higher initial Mn(II) concentration, and iron oxides with stronger electrochemical catalytic effect are more conducive to the oxidation of Mn(II) as well as the subsequent oxidation of coexisting Cr(III) and the immobilization of formed Cr(IV).</div></div>","PeriodicalId":8064,"journal":{"name":"Applied Geochemistry","volume":"175 ","pages":"Article 106195"},"PeriodicalIF":3.1,"publicationDate":"2024-10-11","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142533969","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}