Applied Geochemistry最新文献

{"title":"Geochemistry and mineralogy of the late Neogene alkaline megalake sediments in the Qaidam Basin (China): Implications for provenance, tectonics, paleoclimate, paleoenvironment and organic matter accumulation","authors":"Jinqi Qiao ,&nbsp;Qingyong Luo ,&nbsp;Xianglu Tang ,&nbsp;Dandan Wang ,&nbsp;Imran Khan ,&nbsp;Ludmila Kopaevich","doi":"10.1016/j.apgeochem.2025.106339","DOIUrl":"10.1016/j.apgeochem.2025.106339","url":null,"abstract":"<div><div>The late Neogene is widely regarded as a suitable analogy for future climate scenarios, but the paleoclimatic conditions of this period on the Qinghai-Tibet Plateau remain poorly understood. This study investigates the mineralogical composition and elemental geochemistry of 24 shale samples from two wells in the Yiliping Depression of the Qaidam Basin to reconstruct the paleodepositional conditions of the sediments and the late Neogene paleoclimate conditions. The results indicate that the chemical composition of the late Neogene alkaline lacustrine sediments was little affected by sediment recycling, sorting, diagenesis and metasomatism. Provenance analysis indicates a predominantly felsic source with minor contributions from intermediate volcanic rocks, formed under a tectonic setting similar to continental island arc tectonic settings in geochemistry. Paleoclimate reconstructions reveal consistently arid and cold conditions on the Qinghai-Tibet Plateau, characterized by weak chemical weathering. These climatic conditions were colder than those achieved in most contemporaneous regions globally, with a distinct cooling trend from the late Neogene to the Pleistocene. The deposition occurred predominantly in hypersaline environments, with localized transitions to brackish conditions. The redox conditions of the water column varied spatially, i.e., oxic waters dominated in the central depression (the H 1 well area), while the margins of the depression (the Y 3 well area) experienced fluctuations between oxic to anoxic conditions. The primary paleoproductivity in the Y 3 well exhibited similarities to that in the Holocene lakes of Peru and Brazil, whereas the H 1 well showed resemblances to most marine sediments. Notably, the primary paleoproductivity of the studied samples was lower than that of typical upwelling systems. Organic matter preservation was principally controlled by depositional conditions, with little effects from primary paleoproductivity and sedimentation rate/detrital input. This work provides valuable insights into the late Neogene climate dynamics on the Qinghai-Tibet Plateau and enhances the understanding of the formation of microbial gas source rocks.</div></div>","PeriodicalId":8064,"journal":{"name":"Applied Geochemistry","volume":"183 ","pages":"Article 106339"},"PeriodicalIF":3.1,"publicationDate":"2025-02-28","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143580465","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":"An experimental and modeling study of CaCO3 nucleation and inhibition by PAPEMP under a regime of increasing oversaturation with implications for crystallization and scale formation","authors":"Amit G. Reiss,&nbsp;Xin Wang,&nbsp;Yuqing Ye,&nbsp;Amy T. Kan,&nbsp;Mason B. Tomson","doi":"10.1016/j.apgeochem.2025.106322","DOIUrl":"10.1016/j.apgeochem.2025.106322","url":null,"abstract":"<div><div>Rising saturation causes nucleation in natural and engineered environments. As the saturation increases, nucleation begins, forming a scale that is detrimental to energy production, desalination, and other industrial procedures. Inhibitor addition for scale prevention is a common practice with significant economic and environmental costs. Traditional experiments to determine induction times (<em>t</em>_<em>ind</em>) and evaluate inhibitor efficiency are performed under constant oversaturation. Similarly, constant oversaturation is used in both the empirical and the classical nucleation theory modeling schemes used for scale prediction. Subsequently, experiments and models do not address the dynamic nature of oversaturation increase during energy production.</div><div>We developed an experimental system for quantitative investigation of nucleation kinetics under a regime of dynamic oversaturation and a simple algorithm for determining <em>t</em>_<em>ind</em> from laser measurements. Using our system, we studied the precipitation kinetics of CaCO₃ minerals at a pH of ∼6.76, ionic strength of I = 1 m, temperature range of 50–90 °C, and varying rates of oversaturation increase (i.e., characteristic times). We quantified the effect of a potent inhibitor (Polyamino Polyether Methylene Phosphonate; PAPEMP) on the <em>t</em>_<em>ind</em> and the forming solid phase. Finally, we show that the characteristic time controls <em>t</em>_<em>ind</em> in systems with rising supersaturation and developed a numerical model that explicitly accounts for this key parameter.</div><div>Here, we present our experimental system, results, and modeling scheme. We show that for a given set of conditions, calcite induction occurs at a similar oversaturation, regardless of the rate at which oversaturation increases. Moreover, we show that PAPEMP retards CaCO₃ nucleation at below ppm levels and that it has a temperature-dependent effect on polymorphism. Lastly, we suggest that expanding existing models such that:</div><div><span><math><mrow><msub><mi>t</mi><mrow><mi>i</mi><mi>n</mi><mi>d</mi></mrow></msub><mo>=</mo><mi>f</mi><mrow><mo>(</mo><mrow><mo>Δ</mo><mi>S</mi><mi>I</mi></mrow><mo>)</mo></mrow><mo>∗</mo><mi>f</mi><mrow><mo>(</mo><msub><mi>t</mi><mrow><mi>i</mi><mi>n</mi><mi>d</mi><mo>,</mo><mi>c</mi><mi>o</mi><mi>n</mi><mi>s</mi><mi>t</mi><mi>a</mi><mi>n</mi><mi>t</mi></mrow></msub><mo>)</mo></mrow></mrow></math></span></div><div>where <em>f(ΔSI)</em> is a function of oversaturation with time and <em>f(t</em>_{<em>ind, constant</em>}<em>)</em> are existing modeling schemes, adequately describe the dynamic nature of oversaturation and show a form of <em>f(ΔSI)</em> that provides an excellent fit with measured <em>t</em>_<em>ind</em>.</div></div>","PeriodicalId":8064,"journal":{"name":"Applied Geochemistry","volume":"183 ","pages":"Article 106322"},"PeriodicalIF":3.1,"publicationDate":"2025-02-25","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143580467","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":"Radiometric dating and biodegradation assessment of Light Non-Aqueous Phase Liquids (LNAPL): Results from two case studies","authors":"A. Briganti ,&nbsp;M. Voltaggio ,&nbsp;M. Resitano ,&nbsp;C. Cruz Viggi ,&nbsp;F. Aulenta ,&nbsp;C. Carusi ,&nbsp;E. Rainaldi","doi":"10.1016/j.apgeochem.2025.106334","DOIUrl":"10.1016/j.apgeochem.2025.106334","url":null,"abstract":"<div><div>This study introduces a comprehensive methodology that integrates radiometric dating with gas chromatographic (GC) analyses of light non-aqueous phase liquids (LNAPL) recovered from monitoring wells at different filling stations. The aim is to evaluate the temporal evolution of LNAPLs in two distinct scenarios: natural attenuation (at site 1) and ongoing remediation activities (at site 2). The study period spans one year and four months, from June 2020 to October 2021. Throughout this time frame, the study monitored the progress of petroleum hydrocarbon biodegradation by analysing selected compounds: Total Petroleum Hydrocarbons (TPH), Σ <em>n</em>-alkanes (C₁₃ to C₁₈), Σ isoprenoids (C₁₅ to C₂₀), C₁₇/Pristane and C₁₈/Phytane ratios, and a specific biodegradation diagnostic index. The age determination provided reliable results for a single-point model release scenario (site 1). However, at site 2, where multiple LNAPL spills occurred, the age determination resulted in only an apparent age, due to the mixing of different fluids. Nevertheless, the unlike spatial distribution of the fluids offers some chances to estimate the age of the end members. The trend of the biodegradation in LNAPLs recovered from the two sites seems similar, pointing to a nearly complete removal of isoprenoids, independent of the initial values and whether or not there is an active remediation process. The main difference between the sites is the apparent tendency to the reduction of the heaviest (TPH) and more persistent compounds (such as pristane and phytane), probably triggered by the electrokinetic oxidation system taking place in the second site. The importance of these initial experimental findings lies in their ability to evaluate the site-specific response to pollutants, thereby enhancing the effectiveness of remediation efforts over time.</div></div>","PeriodicalId":8064,"journal":{"name":"Applied Geochemistry","volume":"183 ","pages":"Article 106334"},"PeriodicalIF":3.1,"publicationDate":"2025-02-25","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143621032","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":"Determination of CO2 and DIC in high-CO2 waters: An application for the analysis of coal mine waters","authors":"Dorothy J. Vesper ,&nbsp;Charles A. Cravotta III ,&nbsp;Lili Lei ,&nbsp;Morgan Wallace ,&nbsp;Camille R. Schaffer","doi":"10.1016/j.apgeochem.2025.106336","DOIUrl":"10.1016/j.apgeochem.2025.106336","url":null,"abstract":"<div><div>The impact of sulfuric-acid weathering on the global carbon cycle is increasingly being recognized as important in both recent and deep time estimates yet remains poorly constrained. Global-scale estimates of CO₂ fluxes are hampered by the lack of data, especially for acidic waters. Mining-impacted groundwaters and associated discharges, which can be acidic and contain CO₂ orders of magnitude greater than atmospheric equilibrium, are chemically unstable at the Earth surface and are often difficult to sample and accurately analyze. The direct CO₂ method used herein is accurate and precise with holding times up to 25 days. This modified method allows for the determination of CO₂ and DIC in samples lacking measurable alkalinity or having high CO₂ pressures; these samples may otherwise be excluded from estimates of regional carbon fluxes. To demonstrate the method, natural and CO₂-treated mine waters with pHs ranging from 3.1 to 7.1 were sampled and found to contain between 2 and 13 mM CO₂ (88–572 mg CO₂/L, 24–154 mg C/L) and 2–21 mM dissolved inorganic carbon, DIC (24–252 mg C/L). In comparison to standard DIC estimation methods, the direct method for analyzing CO₂ and determining corresponding concentrations of DIC is more accurate and reproducible over holding times of several weeks for water samples containing low-to-high CO₂ and with acidic-to-circumneutral pH.</div></div>","PeriodicalId":8064,"journal":{"name":"Applied Geochemistry","volume":"183 ","pages":"Article 106336"},"PeriodicalIF":3.1,"publicationDate":"2025-02-25","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143628109","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":"A 3.5-year rainfall isotope records from northwestern Madagascar featuring 17Oexcess and implication for paleoclimate research","authors":"Ny Riavo G. Voarintsoa","doi":"10.1016/j.apgeochem.2025.106335","DOIUrl":"10.1016/j.apgeochem.2025.106335","url":null,"abstract":"<div><div>The lack of modern rainfall stable isotope datasets can leave a knowledge gap in paleoclimate reconstructions using climate sensitive archivers like stalagmites. This is the case of the growing number of paleoclimate records from Anjohibe Cave, where no local rainfall data has been available. This paper reports the first modern rainfall stable isotopes of hydrogen (δ²H and <em>d-</em>excess) and oxygen (δ¹⁷O and δ¹⁸O), highlighting a novel ¹⁷O_excess proxy, spanning 3.5 years of collection from Mahajanga, the closest city of Anjohibe. These data are compared to the only prior existing rainfall isotope data from Madagascar, which was collected from the capital, Antananarivo. Interpretation of the results was helped with model simulations using ERA5T reanalysis and HYSPLIT back trajectory models. Overall, the rainfall data provide better insights on hydrological processes in Mahajanga, including a better constrain on the latitudinal migration of the Inter-Tropical Convergence Zone (ITCZ) and its impact on the kinetic and equilibrium isotopic effect that is best observed in both <em>d</em>-excess and ¹⁷O_excess.</div><div>Results show that rainfall δ¹⁸O (ranging between −7.9 and + 3.9‰, vs. VSMOW) and δ²H (ranging between −49.8 and + 19.7 ‰, vs. VSMOW) from Mahajanga fit within the Global Meteoric Water Line, and they are best explained by the amount effect. However, both <em>d</em>-excess and ¹⁷O_excess are kinetically affected by evaporation for months receiving &lt;1000 mm of rainfall. These months represents the onset and termination of a rainy summer season, when the ITCZ is positioned further north. Above 1000 mm, both values plateaued at ∼15 ‰ and at ∼20 per meg, respectively, regardless of the amount. These values seem to represent the regional equilibrium value for <em>d</em>-excess and ¹⁷O_excess in Mahajanga, when the air is moist during the southward visit of the ITCZ. It is also noted that Mahajanga ¹⁷O_excess values are at the lower spectrum relative to the global ¹⁷O_excess values (20–30 per meg), which are currently biased toward more northern hemisphere datasets. Anjohibe Cave drip waters (varying between −5.6 and −2.1‰ vs. VSMOW for δ¹⁸O and between −33.9 and −8.3 ‰ vs. VSMOW for δ²H), on the other hand, reflect more mixing of the rainfall values due to epikarst storage effects. Calculation of the isotopic fractionation factor between stalagmite and the drip waters in Anjohibe Cave also suggests a good fit with the global fractionation value, 1000ln¹⁸α = 16.89 ± 0.62 × 10³/T(K) – 27.41 ± 2.14, and serves as an excellent motivation to develop future ¹⁷O_excess records from stalagmites in the region.</div></div>","PeriodicalId":8064,"journal":{"name":"Applied Geochemistry","volume":"184 ","pages":"Article 106335"},"PeriodicalIF":3.1,"publicationDate":"2025-02-24","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143684137","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":"Aqueous solubilities in the apatite solid-solution system with double co-substitution on both Ca–Sr cation and OH–F anion sublattice positions","authors":"Michael Kersten","doi":"10.1016/j.apgeochem.2025.106323","DOIUrl":"10.1016/j.apgeochem.2025.106323","url":null,"abstract":"<div><div>To investigate the potential for Sr-90 radionuclide sequestration by apatite phases in contaminated soils and aquifers, the solubility product constants of solid solutions in the apatite supergroup system (Ca,Sr)₅(PO₄)₃(OH,F) were studied. Binary hydroxyl- and fluorapatite solid solutions of varying compositions were synthesized hydrothermally at 200 °C and characterized by using Rietveld and chemical analysis. The lattice axis lengths and cell volumes exhibited a linear increase with increasing Sr content, adhering to Vegard's law and indicating mixing without mixing gaps in the solid-solution system. Dissolution studies were conducted at 25 °C through aqueous batch equilibrium experiments. Aqueous solubility increased with the mole fraction of Sr. However, batch equilibration over weeks led to a stoichiometric rather than a true equilibrium state. Such stoichiometric dissolution of a solid solution is commonly observed in low-solubility phases such as apatite minerals. Stoichiometric saturation for solid solutions corresponds to equal molar Gibbs energy functions of the solid and aqueous phases, which can be represented by an “equal-G curve” (EGC) in Lippmann diagrams. Stoichiometric solubility product constants <em>K</em>_st were calculated from the solute activities in the dissolution experiments. These constants align along the straight EGC line connecting the endmember solubility product constants. The excess Gibbs energy of mixing in the solid phase is therefore zero indicating formation of an ideal solid solution system. Correct binary Lippmann phase diagrams were successfully plotted for the first time for substituting cations with stoichiometric factors greater than unity. These diagrams allow for the prediction of solubilities across any solid solution composition, including co-substitutions in both the cation and anion sublattices as represented for the first time by a quaternary Lippmann diagram. The results illustrate that substitution of Ca by Sr increases the solubility of the resulting solid solutions under short-term metastable (stoichiometric) solubility conditions and may lead to preferential Sr release under long-term thermodynamic equilibrium conditions. These findings provide significant environmental implications for Sr-90 radionuclide immobilization using apatite-type minerals.</div></div>","PeriodicalId":8064,"journal":{"name":"Applied Geochemistry","volume":"183 ","pages":"Article 106323"},"PeriodicalIF":3.1,"publicationDate":"2025-02-24","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143580466","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":"Mixed nitrogen inputs affected nitrate distribution and biogeochemical processes during ice-covered and ice-free periods in a boreal eutrophic steppe lake basin","authors":"Wenlin Wang ,&nbsp;Jiasen Yang ,&nbsp;Fang Yang ,&nbsp;Liu Yang ,&nbsp;Xiaoguang Xu ,&nbsp;Yulong Tao ,&nbsp;Wen Ao ,&nbsp;Bo Liu ,&nbsp;Qiu Jin ,&nbsp;Guoxiang Wang","doi":"10.1016/j.apgeochem.2025.106333","DOIUrl":"10.1016/j.apgeochem.2025.106333","url":null,"abstract":"<div><div>Nitrogen enrichment from nitrate is a significant contributor to water quality eutrophication in various freshwater basins. However, the input pathways and transformation processes of nitrate remain unclear, particularly during different hydrological processes in boreal eutrophic steppe lake basins that are susceptible to human activity and climate change stressors. In this study, we experimentally investigate the nitrogen sources, transport and transformation in the high-latitude Hulun Lake basin during both ice-covered and ice-free periods using the dual stable isotopes of nitrate (δ¹⁵N–NO₃^- and δ¹⁸O–NO₃^-) with the Stable Isotope Analysis in R (SIAR) model. Our results indicate that nitrate input contributed to water body eutrophication in the Hulun Lake basin, with varying inputs during different hydrological processes. Our quantitative analysis reveals that during the ice-covered period, manure/sewage water (MS) was the dominant nitrate input pathway, accounting for 55.3%, while atmospheric precipitation (AP) contributed the most at 49.8% during the ice-free period. The primary transport and transformation process of nitrate was further identified as nitrification instead of denitrification, as evidenced by the Cl⁻ and NO₃⁻/Cl⁻ levels and redundancy analysis. This study highlights the complexity of nitrate input pathways and transformation processes under different hydrological conditions and emphasizes their significant impact on the nitrogen cycle and ecology of water environments in boreal steppe lake basins.</div></div>","PeriodicalId":8064,"journal":{"name":"Applied Geochemistry","volume":"182 ","pages":"Article 106333"},"PeriodicalIF":3.1,"publicationDate":"2025-02-23","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143479571","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":"Increasing anthropogenic contributions on hydrochemical evolution of groundwater in the Yellow River basin over the past decade","authors":"Feisheng Feng ,&nbsp;Guangyong Chen ,&nbsp;Tingting Yao ,&nbsp;Yu Wei ,&nbsp;Yongping Shan ,&nbsp;Wanli Su","doi":"10.1016/j.apgeochem.2025.106331","DOIUrl":"10.1016/j.apgeochem.2025.106331","url":null,"abstract":"<div><div>The temporal evolution of groundwater chemistry is crucial for guiding sustainable water resource management. In China, the Yellow River Basin features active geological structures, diverse lithology, and significant human impacts, leading to unclear patterns and factors governing groundwater chemistry evolution. In this study, we investigated the characteristics, sources, and controlling factors of groundwater chemistry in the Yellow River Basin during the period of 2011–2022, with a view to providing guidance for water chemistry management in the region. The results indicate that over time, major ions (Na⁺, Mg²⁺, Cl⁻, SO₄²⁻, NO₃⁻, and F⁻) in the Yellow River Basin's groundwater rise then fall, with pH initially increasing before stabilizing at a mild alkaline level. The anions in groundwater chemistry are dominated by HCO₃⁻, which accounts for 38.89–60.78% of the anion concentration equivalent, and cations are dominated by Na⁺, which accounts for 31.43–72.22%. Hydrochemical types shift among HCO₃–Ca, Cl–SO₄–Na, and mixed HCO₃–Ca–Mg, with Cl–SO₄–Na type correlating positively with human activity level. Dissolution of minerals are the primary sources of groundwater chemistry. Hydrochemical evolution is driven by rock weathering alongside human activities such as sewage discharge and fertilizer application. Initially, mineral weathering was the key factor, with the chemical composition becoming dynamically altered as human activity increased. In summary, the groundwater chemistry in the Yellow River Basin mainly stems from mineral reactions, initially by rock weathering and later affected by rising human activities. This study advances knowledge of groundwater geochemical dynamics in the Yellow River Basin, supporting improved management and sustainable water resource use.</div></div>","PeriodicalId":8064,"journal":{"name":"Applied Geochemistry","volume":"183 ","pages":"Article 106331"},"PeriodicalIF":3.1,"publicationDate":"2025-02-22","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143520057","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":"Unraveling hydrogen induced geochemical reaction mechanisms through coupled geochemical modeling and machine learning","authors":"D.L. Driba,&nbsp;Lauren E. Beckingham","doi":"10.1016/j.apgeochem.2025.106330","DOIUrl":"10.1016/j.apgeochem.2025.106330","url":null,"abstract":"<div><div>Underground hydrogen storage (UHS) provides a promising large-scale, long-term energy storage solution. A reasonable recovery of stored hydrogen is critical for a successful storage scheme. However, in subsurface reservoirs hydrogen is subject to active geochemical reactions that might result in hydrogen loss. In this study, we implemented a geochemical modeling approach coupled with an unsupervised machine learning technique called non-negative matrix factorization (NMF) to unravel the complex brine-rock-H₂ geochemical processes responsible for hydrogen losses, with particular focus on sulfate reduction reactions. NMF is applied to modeled mineral evolution and fluid component profiles to retrieve profiles that can be interpreted to more easily assess competing processes. NMF decouples simulated competing equilibrium reactions. This facilitates separation of overlapping reaction profiles from redox processes, dissolution fronts, and secondary precipitation while considering the effects of simulation parameters such as salinity, temperature, and total H₂ pressure. NMF successfully discriminates these competing effects in nonlinear ways, allowing robust interpretation. In addition, NMF reveals subtle coupled mineral associations and reaction fronts that are invisible to conventional model analysis. This integrated approach strengthens the conceptual understanding of complex nonlinear hydrogen-brine-rock interactions and advances geochemical research on UHS systems to resolve complexities in modeled geochemical systems without the need for direct experiments or prior knowledge. This study highlights the efficacy of combining geochemical modeling with machine learning techniques to enhance the interpretability of the intricate geochemical simulation output through deciphering the overlapping reaction path that cannot be achieved only using conventional analysis of geochemical models alone.</div></div>","PeriodicalId":8064,"journal":{"name":"Applied Geochemistry","volume":"183 ","pages":"Article 106330"},"PeriodicalIF":3.1,"publicationDate":"2025-02-22","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143552378","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":"Country-scale lithogeochemical interpretation of stream sediment dataset in central Cameroon: Toward an integrated tool to support national geophysics surveys and geological mapping programs","authors":"G. Vic ,&nbsp;J. Bernard ,&nbsp;M. Chevillard ,&nbsp;L. Bailly ,&nbsp;C. Ndongue ,&nbsp;Y. Itard ,&nbsp;J. Melleton ,&nbsp;G. Martelet ,&nbsp;E. Kouokam ,&nbsp;E. Fournier ,&nbsp;R. Couëffé ,&nbsp;D. Keutia","doi":"10.1016/j.apgeochem.2025.106321","DOIUrl":"10.1016/j.apgeochem.2025.106321","url":null,"abstract":"<div><div>In the frame of a 1:200,000 mapping project of Cameroon coordinated by PRECASEM for the Ministry of Mine, Industry and Technological Development (MINMITD), between 2016 and 2021, and carried out by BRGM-GTK-BEIG3 Consortium, a dataset of nearly 15,500 stream sediment samples were collected, at an average sampling density of 1 sample per 10 km², over an area of some 157,000 km², and analysed for 49 major and traces elements plus gold. The first aim of the geochemical survey was to identify, at the country scale, metallic anomalies and districts to promote the mining potential of Cameroon to mining investors.</div><div>In order to expand the use of this unique geochemical dataset, multivariate geostatistical processing by Principal Component Analysis (PCA) and Agglomerative Hierarchical Clustering (AHC) was performed for lithogeochemical purpose. This processing enabled the identification of several lithogeochemical signatures which match very well with the main geological domains and formations obtained by conventional geological field survey. Moreover, in areas covered by thick lateritic profile like in the Adamawa-Yadé subdomain, the geostatistical processing was able to identify the granitic nature of the bedrock.</div><div>Secondly, the geochemical results obtained for U, K and Th on stream sediments were handled by inverse distance interpolation (IDW), and represented in a ternary combination in the RGB colour space to generate a pseudo-radiometric map to be compared with the high-resolution regional-scale airborne geophysical survey (magnetic and radiometric data) undertaken prior to the beginning of the mapping project. Similarities between both maps are remarkable. Moreover, the pseudo-radiometric map appears also more discriminant in areas covered by thick forest and thick lateritic profile, in humid and swampy environments allowing the identification of structural features and geochemical contrasts unrevealed by the airborne survey.</div><div>This contribution shows that stream sediment regional-to country-scale dataset should not only be used to highlight the mining potential of the studied area, but also represent a powerful tool, once derived in lithogeochemical and pseudo-radiometric interpretative maps, which can be efficiently used to decipher the major geological contrasts and structural feature of the country rocks. This information is of primary importance to define and calibrate the targets, logistics and costs of the geological field survey classically associated with these national programs, especially in areas with poor outcrops and/or not covered by airborne geophysical surveys.</div></div>","PeriodicalId":8064,"journal":{"name":"Applied Geochemistry","volume":"183 ","pages":"Article 106321"},"PeriodicalIF":3.1,"publicationDate":"2025-02-22","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143520056","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}