Applied Geochemistry最新文献

{"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 , Martin Kutzschbach , Henrik Drake , Vanessa Fichtner , Piotr M. Kowalski , Stefan Rudin , Martin J. Whitehouse , Mikael Tillberg , Thomas Neumann","doi":"10.1016/j.apgeochem.2024.106208","DOIUrl":"10.1016/j.apgeochem.2024.106208","url":null,"abstract":"<div><div>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<sub>4</sub>) 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.</div><div>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.</div><div>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.</div><div>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<sub>4</sub> and (Sr,Ba)SO<sub>4</sub> 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<sup>−2</sup> range were determined, showing a deviation from those reported in previous experimental studies in the 10° range.</div><div>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<sup>−2</sup> and 10<sup>−1</sup>, 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.</div><div>This study demonstrates a discrepancy between natural and synthetic <em>P</em><sub>Ra</sub> 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}

{"title":"Investigation of geochemically induced permeability alteration in geothermal reservoirs and its implications for sustainable geothermal energy production","authors":"Taylor Smith ,&nbsp;Adedapo N. Awolayo ,&nbsp;Stephen E. Grasby ,&nbsp;Benjamin M. Tutolo","doi":"10.1016/j.apgeochem.2024.106193","DOIUrl":"10.1016/j.apgeochem.2024.106193","url":null,"abstract":"<div><div>Geothermal resources constitute a significant portion of the world's low-carbon, renewable energy potential, with about 75% classified as low-temperature. One such potential resource exists in Precambrian basement rocks underlying the Williston Basin in southern Saskatchewan, Canada, with a reservoir temperature of 120 °C. However, geochemically induced permeability alteration in these highly reactive low-temperature granitoid resources poses a significant risk to long-term heat production. To assess and potentially mitigate this risk, we conducted a geochemical and mineralogical study of both altered and unaltered samples. Our findings facilitated the parameterization of geochemical simulations of water-rock interactions to predict mineral volume changes and, by extension, draw inferences on porosity and permeability changes resulting from these interactions. The simulations indicate an increased mineral volume in both samples, yet geothermal alteration of the unaltered, and thus more reactive, rocks induced relative mineral volume changes about 30% greater than those in the altered rocks. The resulting absolute change in porosity is 0.5 vol% for the unaltered rocks and 0.35 vol% for the altered rocks. Utilizing an empirical porosity-permeability relationship, the computed change in permeability indicates that the unaltered basement rock experienced a greater change in total permeability than the altered basement rocks. Additional calculations demonstrate the sensitivity of the porosity-permeability equation to critical porosity and power exponent, forecasting various scenarios with permeability changes ranging from 1.0 × 10⁻¹³ to 1 × 10⁻²⁰ m². Consequently, we infer that altered, permeable zones of the examined Precambrian basement rocks are likely to offer favourable conditions for sustained, multi-decade heat production, and thus should be targeted over less altered zones to justify initial capital expenditures. Globally, geothermal heat extraction from these rocks remains an underexplored yet promising resource for generating reliable, low-carbon renewable energy, crucial in our efforts to decarbonize the global economy.</div></div>","PeriodicalId":8064,"journal":{"name":"Applied Geochemistry","volume":"175 ","pages":"Article 106193"},"PeriodicalIF":3.1,"publicationDate":"2024-10-11","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142533970","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":"Selenium interaction with iron minerals: Quantitative comparison of sorption and coprecipitation impacts on mobility","authors":"Enrica Balboni ,&nbsp;Sol-chan Han ,&nbsp;Mavrik Zavarin","doi":"10.1016/j.apgeochem.2024.106194","DOIUrl":"10.1016/j.apgeochem.2024.106194","url":null,"abstract":"<div><div>Given the significance of selenium (Se) as a micronutrient, the radioactive nature of some of its isotopes, and its affinity to iron (Fe) minerals, extensive research has been conducted on the sorption mechanisms between Se and these minerals. Here, we employ sorption data sourced from the L-SCIE database and coprecipitation data from available literature to achieve the following objectives: i) establish coherence between adsorption and coprecipitation processes, ii) quantitatively evaluate the importance of these processes in nuclear waste repository science, and iii) propose a forward-looking approach for integrating coprecipitation into reactive transport models. Our findings indicate that a correlation between Se adsorption and coprecipitation can be established using the <em>λ</em> formalism. The comparable log(λ_Se(IV)/λ_Se(VI)) ratios derived from adsorption and coprecipitation experiments suggest that these processes can be quantitatively compared and evaluated using our numerical approach. Across all iron oxide phases examined, coprecipitation leads to significantly greater immobilization of Se compared to adsorption. Specifically, for hydrous ferric oxide, hematite, and goethite, coprecipitation is predicted to result in 100–1000 times more Se immobilization compared to adsorption, irrespective of the Se oxidation state (Se(IV) or Se(VI)); notably stronger immobilization potential via coprecipitation was observed for magnetite. The modeling approach and quantitative analysis presented herein clearly highlight the importance of including coprecipitation processes when simulating Se (and other elements) transport, particularly under conditions where mineral compositions are transient or evolving with time. Neglecting coprecipitation in models is likely to lead to significant overestimates of migration.</div></div>","PeriodicalId":8064,"journal":{"name":"Applied Geochemistry","volume":"175 ","pages":"Article 106194"},"PeriodicalIF":3.1,"publicationDate":"2024-10-10","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142432384","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":"High resolution concentration-discharge relationships in managed watersheds: A 30+ year analysis","authors":"M.A. Diaz ,&nbsp;S.K. Fortner ,&nbsp;W. Berry Lyons","doi":"10.1016/j.apgeochem.2024.106192","DOIUrl":"10.1016/j.apgeochem.2024.106192","url":null,"abstract":"<div><div>Concentration-discharge (C-Q) relationships provide insight into solute transport and biogeochemical processes for watersheds. A 30+ year, high-resolution dataset from the North Appalachian Experimental Watershed (NAEW) offers an unparalleled opportunity to explore land use and land management impacts on C-Q relationships for small watersheds of varying land management histories (agricultural to forested). The NAEW was among the few hydrologic research sites where storm event runoff was sampled using proportional sampling. This method captures the concentration-discharge behavior associated with land use more effectively than instantaneous sampling, which favors rising limb or falling limb dynamics. In this study, we explore C-Q relationships by investigating baseflow and storm event flow across their total behavior. We also build a systems-understanding by comparing chemostatic behavior to soil geochemistry and land use history. Highly managed agricultural watersheds with no associated stream baseflow demonstrate near-chemostatic behavior for most solutes, while mixed use and forested watersheds with associated streams are more mutable depending on whether primary sources of water were groundwater or surface water. Using this unique high-resolution dataset, we show that concentration-discharge relationships are influenced by soil and baseflow geochemistry, pore fluid concentration, and land type/land use legacy effects.</div></div>","PeriodicalId":8064,"journal":{"name":"Applied Geochemistry","volume":"175 ","pages":"Article 106192"},"PeriodicalIF":3.1,"publicationDate":"2024-10-09","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142432383","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":"Reactive transport model of the long-term geochemical evolution in a HLW repository in granite at the disposal cell scale: Variants, sensitivities, and model simplifications","authors":"Javier Samper,&nbsp;Alba Mon,&nbsp;Luis Montenegro","doi":"10.1016/j.apgeochem.2024.106188","DOIUrl":"10.1016/j.apgeochem.2024.106188","url":null,"abstract":"<div><div>The assessment of the long-term performance of the engineered barrier systems of high-level radioactive waste (HLW) repositories requires the use of reactive transport models. Montenegro et al. (2023) presented a non-isothermal reactive transport model of the long-term geochemical evolution of a HLW disposal cell in a granitic host rock corresponding to a generic reference concept. The model accounted for the vitrified waste, the carbon-steel canister, the bentonite buffer and the reference granitic rock. Here we extend their model by considering model variants (V), sensitivity cases (SC) and model abstractions (MA). Variants V1, V2 and V3 consist of considering MX-80 bentonite instead of FEBEX bentonite (V1), a larger groundwater flux through the granite (V2) and the Czech reference crystalline rock as a host rock (V3). Cases SC1 and SC2 consider a decrease of the silica concentration threshold value in the glass dissolution rate (SC1) and an earlier canister failure time (SC2), respectively. Runs MA1 to MA4 consider smectite as an unreactive mineral phase (MA1), the porosity feedback effect on chemical and transport parameters (MA2), a time-varying corrosion rate (MA3), and a coarser finite element grid (MA4), respectively. Model results of V1 show a larger pH, a smaller precipitation of magnetite, siderite and greenalite and a slightly smaller dissolution of ISG and smectite than the base run of Montenegro et al. (2023). Model predictions are very sensitive to the increase in the groundwater flow through the granitic host rock (V2). However, predictions are not sensitive to the chemical composition of the granite porewater (V3). The decrease in the silica saturation threshold from 1·10⁻³ to 5·10⁻⁴ mol/L in SC1 leads to a significant decrease in glass dissolution. Glass dissolution after 50,000 years in SC2 (earlier canister failure) is much larger than that of the base run. Model results are not sensitive to considering smectite as an unreactive mineral phase (MA1). However, model results are very sensitive to the porosity feedback effect (MA2). A 60% volume fraction of Fe(s) remains uncorroded after 50,000 years when a variable corrosion rate is considered in MA3. In this case the precipitation of corrosion products is much smaller than that of the base run. The general patterns of the numerical results in MA4 (coarser grid) are similar to those of the base case.</div></div>","PeriodicalId":8064,"journal":{"name":"Applied Geochemistry","volume":"175 ","pages":"Article 106188"},"PeriodicalIF":3.1,"publicationDate":"2024-10-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142416495","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}