Pub Date : 2025-10-08DOI: 10.1016/j.apgeochem.2025.106586
Ji Hoon Lee , Ho Young Jo , Jang-Soon Kwon
Understanding the performance of bentonite buffer materials in the presence of cement leachates at > 100°C is required for optimizing the design of deep geological repositories for high-level radioactive wastes. This study investigated the effects of exposure to a Ca(OH)2 saturated solution at 150°C on Ca-bentonite, focusing on how mineralogical changes in the bentonite affect its physicochemical, swelling and hydraulic, and cesium (Cs) retention properties, which are key attributes for buffer materials. Analytical techniques, including X-ray diffraction, nuclear magnetic resonance, thermal gravimetry and differential thermal analyses, indicated calcium silicate hydrate (CSH) formation. Despite this alteration, cation exchange and Cs retention capacities were largely unaffected. Swelling pressure tests on compacted bentonite specimens (dry density: 1.6 Mg/m3) prepared from hydrothermally treated bentonite showed a reduction in swelling pressure. However, no significant difference in the hydraulic conductivity occurred. X-ray photoelectron spectroscopy analysis of the compacted bentonite specimen indicated consistent Cs retention across the specimen with no effluent detected over a one-year permeation period, suggesting that the specimens were still absorbing fluid. Overall, Ca-bentonite treated with a Ca(OH)2 saturated solution at 150°C for up to two years showed minimal CSH formation and minor changes in physicochemical, hydraulic, and Cs retention properties, with a slight reduction in swelling pressure.
{"title":"Physicochemical, hydromechanical, and Cs retention properties of Ca-bentonite treated with Ca(OH)2 saturated solution at 150°C for up to 2 years","authors":"Ji Hoon Lee , Ho Young Jo , Jang-Soon Kwon","doi":"10.1016/j.apgeochem.2025.106586","DOIUrl":"10.1016/j.apgeochem.2025.106586","url":null,"abstract":"<div><div>Understanding the performance of bentonite buffer materials in the presence of cement leachates at > 100°C is required for optimizing the design of deep geological repositories for high-level radioactive wastes. This study investigated the effects of exposure to a Ca(OH)<sub>2</sub> saturated solution at 150°C on Ca-bentonite, focusing on how mineralogical changes in the bentonite affect its physicochemical, swelling and hydraulic, and cesium (Cs) retention properties, which are key attributes for buffer materials. Analytical techniques, including X-ray diffraction, nuclear magnetic resonance, thermal gravimetry and differential thermal analyses, indicated calcium silicate hydrate (CSH) formation. Despite this alteration, cation exchange and Cs retention capacities were largely unaffected. Swelling pressure tests on compacted bentonite specimens (dry density: 1.6 Mg/m<sup>3</sup>) prepared from hydrothermally treated bentonite showed a reduction in swelling pressure. However, no significant difference in the hydraulic conductivity occurred. X-ray photoelectron spectroscopy analysis of the compacted bentonite specimen indicated consistent Cs retention across the specimen with no effluent detected over a one-year permeation period, suggesting that the specimens were still absorbing fluid. Overall, Ca-bentonite treated with a Ca(OH)<sub>2</sub> saturated solution at 150°C for up to two years showed minimal CSH formation and minor changes in physicochemical, hydraulic, and Cs retention properties, with a slight reduction in swelling pressure.</div></div>","PeriodicalId":8064,"journal":{"name":"Applied Geochemistry","volume":"194 ","pages":"Article 106586"},"PeriodicalIF":3.4,"publicationDate":"2025-10-08","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145326436","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}
Pub Date : 2025-10-08DOI: 10.1016/j.apgeochem.2025.106585
Jianzhou Yang , Yong Li , Zhuang Duan , Jianguo Li , Kai Li , Jingjing Gong
This study presents a geochemical analysis of 91 sediment samples from the CZKZ01 borehole in the Huanghua Depression, North China Plain, to explore paleoclimatic evolution and sediment provenance since the Oligocene. Major, trace, and rare earth elements (REEs) were analyzed to assess chemical weathering intensity, provenance characteristics, and paleoenvironmental changes. Results show that the Oligocene sediments experienced intense chemical weathering (CIA = 80.1), which gradually decreased over time (CIA = 67.4 in the Pliocene, 66.4 in the Miocene, and 63.0 in the Quaternary). The primary source of sediments was felsic igneous rocks, with REE patterns indicating contributions from metamorphosed sedimentary-volcanic rocks and Mesozoic acidic igneous rocks of the Taihang Mountains, along with nearby uplifted Mesozoic sedimentary units, resulting in compositions resembling the upper continental crust (UCC). Above 120 m depth, elemental compositions become more homogeneous, reflecting increasing input from the modern Yellow River. Redox-sensitive elemental ratios indicate generally oxic depositional conditions since the Oligocene, with a gradual shift from brackish to freshwater environments beginning in the Miocene. Paleoclimatic proxies suggest a transition from warm, humid conditions in the Oligocene–Pliocene to colder, drier climates in the Quaternary, linked to the uplift of the Tibetan Plateau and global cooling events. This study provides crucial insights into sedimentary processes and climate evolution in the late Cenozoic North China Plain.
{"title":"Geochemical evolution of sediments in Huanghua Depression, North China Plain: Implications for weathering, provenance, and paleoclimate since the Oligocene","authors":"Jianzhou Yang , Yong Li , Zhuang Duan , Jianguo Li , Kai Li , Jingjing Gong","doi":"10.1016/j.apgeochem.2025.106585","DOIUrl":"10.1016/j.apgeochem.2025.106585","url":null,"abstract":"<div><div>This study presents a geochemical analysis of 91 sediment samples from the CZKZ01 borehole in the Huanghua Depression, North China Plain, to explore paleoclimatic evolution and sediment provenance since the Oligocene. Major, trace, and rare earth elements (REEs) were analyzed to assess chemical weathering intensity, provenance characteristics, and paleoenvironmental changes. Results show that the Oligocene sediments experienced intense chemical weathering (CIA = 80.1), which gradually decreased over time (CIA = 67.4 in the Pliocene, 66.4 in the Miocene, and 63.0 in the Quaternary). The primary source of sediments was felsic igneous rocks, with REE patterns indicating contributions from metamorphosed sedimentary-volcanic rocks and Mesozoic acidic igneous rocks of the Taihang Mountains, along with nearby uplifted Mesozoic sedimentary units, resulting in compositions resembling the upper continental crust (UCC). Above 120 m depth, elemental compositions become more homogeneous, reflecting increasing input from the modern Yellow River. Redox-sensitive elemental ratios indicate generally oxic depositional conditions since the Oligocene, with a gradual shift from brackish to freshwater environments beginning in the Miocene. Paleoclimatic proxies suggest a transition from warm, humid conditions in the Oligocene–Pliocene to colder, drier climates in the Quaternary, linked to the uplift of the Tibetan Plateau and global cooling events. This study provides crucial insights into sedimentary processes and climate evolution in the late Cenozoic North China Plain.</div></div>","PeriodicalId":8064,"journal":{"name":"Applied Geochemistry","volume":"194 ","pages":"Article 106585"},"PeriodicalIF":3.4,"publicationDate":"2025-10-08","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145326809","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}
Pub Date : 2025-10-08DOI: 10.1016/j.apgeochem.2025.106587
Lanshi Nie , Hanliang Liu , Xueqiu Wang , Yuntao Song , Shojin Davaa , Qinghua Chi , Dongsheng Liu , Xinbin Cheng , Wei Wang
The Sino-Mongolian border region, which is located on the Mongolian Plateau in the interior of Asia, is a significant metallogenic belt and one of three major porphyry copper, gold, and molybdenum metallogenic belts on the globe. Although Mongolia and China are rich in uranium resources, there is a lack of in-depth research on the overall spatial distribution characteristics, influencing factors, and prospecting areas of single-element uranium in the Sino-Mongolian border area, particularly in this region. This study addresses this research gap by determining the distribution characteristics and metallogenic potential of uranium resources in the region through 1:1,000,000 geochemical mapping. To achieve this goal, 10,453 catchment sediment samples were systematically collected and analyzed geochemically. These analyses clarified the distribution characteristics of uranium in the region and explored its enrichment mechanisms. Results revealed a wide range of uranium concentrations in the samples, from 0.07 to 335.52 ppm, with median and mean values of 2.10 and 2.54 ppm, respectively. Using the geochemical block delineation method, 21 high-uranium-content areas (>1000 km2) were identified as geochemical provinces or higher. In addition, nine uranium geochemical blocks were delineated, one of which reached the size of a geochemical domain (>100,000 km2). Furthermore, a comprehensive analysis of the regional geological and tectonic characteristics, mineral combinations, mineralization conditions, and exploitation potential identified five prospective uranium exploration areas with significant potential. Delineating these prospective areas provides a clear direction for future mineral exploration and offers a reliable geochemical basis for the development and utilization of regional mineral resources.
{"title":"Geochemical survey of uranium in catchment sediments and prediction of mineralization prospects along the Sino-Mongolian border region","authors":"Lanshi Nie , Hanliang Liu , Xueqiu Wang , Yuntao Song , Shojin Davaa , Qinghua Chi , Dongsheng Liu , Xinbin Cheng , Wei Wang","doi":"10.1016/j.apgeochem.2025.106587","DOIUrl":"10.1016/j.apgeochem.2025.106587","url":null,"abstract":"<div><div>The Sino-Mongolian border region, which is located on the Mongolian Plateau in the interior of Asia, is a significant metallogenic belt and one of three major porphyry copper, gold, and molybdenum metallogenic belts on the globe. Although Mongolia and China are rich in uranium resources, there is a lack of in-depth research on the overall spatial distribution characteristics, influencing factors, and prospecting areas of single-element uranium in the Sino-Mongolian border area, particularly in this region. This study addresses this research gap by determining the distribution characteristics and metallogenic potential of uranium resources in the region through 1:1,000,000 geochemical mapping. To achieve this goal, 10,453 catchment sediment samples were systematically collected and analyzed geochemically. These analyses clarified the distribution characteristics of uranium in the region and explored its enrichment mechanisms. Results revealed a wide range of uranium concentrations in the samples, from 0.07 to 335.52 ppm, with median and mean values of 2.10 and 2.54 ppm, respectively. Using the geochemical block delineation method, 21 high-uranium-content areas (>1000 km<sup>2</sup>) were identified as geochemical provinces or higher. In addition, nine uranium geochemical blocks were delineated, one of which reached the size of a geochemical domain (>100,000 km<sup>2</sup>). Furthermore, a comprehensive analysis of the regional geological and tectonic characteristics, mineral combinations, mineralization conditions, and exploitation potential identified five prospective uranium exploration areas with significant potential. Delineating these prospective areas provides a clear direction for future mineral exploration and offers a reliable geochemical basis for the development and utilization of regional mineral resources.</div></div>","PeriodicalId":8064,"journal":{"name":"Applied Geochemistry","volume":"194 ","pages":"Article 106587"},"PeriodicalIF":3.4,"publicationDate":"2025-10-08","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145248005","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}
Pub Date : 2025-10-08DOI: 10.1016/j.apgeochem.2025.106588
Farah Ajami, Domitille Giaume, Grégory Lefèvre
The possibility of extraction of W(VI) as heptatungstate species (W7O246−) from pure scheelite mineral (CaWO4) under mild conditions has been evaluated using an inorganic anion exchanger MgAl–Layered double hydroxide (LDH). An optimal pH of 5 was determined for the dissolution/adsorption step while desorption was carried out using a carbonate solution at pH 11. After a leaching time of 24 h with an LDH/scheelite ratio of 1.8, up to 30 % of tungsten has been extracted while scheelite alone is almost insoluble in these conditions. Two sorption mechanisms have been assumed: exchange of heptatungstate ions with carbonate ions of the LDH and precipitation of W(VI) with aluminum cations released from LDH dissolution. Thus, this work provides a proof of concept for the use of LDH in the extraction and recovery of tungsten from scheelite through a low environmental footprint process.
{"title":"Scheelite (CaWO4) leaching in mild conditions via heptatungstate sorption by MgAl– Layered Double Hydroxide","authors":"Farah Ajami, Domitille Giaume, Grégory Lefèvre","doi":"10.1016/j.apgeochem.2025.106588","DOIUrl":"10.1016/j.apgeochem.2025.106588","url":null,"abstract":"<div><div>The possibility of extraction of W(VI) as heptatungstate species (W<sub>7</sub>O<sub>24</sub><sup>6−</sup>) from pure scheelite mineral (CaWO<sub>4</sub>) under mild conditions has been evaluated using an inorganic anion exchanger MgAl–Layered double hydroxide (LDH). An optimal pH of 5 was determined for the dissolution/adsorption step while desorption was carried out using a carbonate solution at pH 11. After a leaching time of 24 h with an LDH/scheelite ratio of 1.8, up to 30 % of tungsten has been extracted while scheelite alone is almost insoluble in these conditions. Two sorption mechanisms have been assumed: exchange of heptatungstate ions with carbonate ions of the LDH and precipitation of W(VI) with aluminum cations released from LDH dissolution. Thus, this work provides a proof of concept for the use of LDH in the extraction and recovery of tungsten from scheelite through a low environmental footprint process.</div></div>","PeriodicalId":8064,"journal":{"name":"Applied Geochemistry","volume":"194 ","pages":"Article 106588"},"PeriodicalIF":3.4,"publicationDate":"2025-10-08","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145326437","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}
Pub Date : 2025-10-04DOI: 10.1016/j.apgeochem.2025.106584
M. Jim Hendry, Erin Schmeling
Elevated concentrations of nitrate (NO3ˉ) are present in many surface waters associated with coal mining throughout the world. Its presence is generally attributed to blasting using ANFO (NH4NO3 and fuel oil) to access the coal. A recent study conducted by our group shows the nitrification of naturally occurring exchangeable ammonium (NH4+-ex) in waste rock can be a major source of NO3− compared to contributions from NO3− and the nitrification of NH4+ originating from blast products. Here we show that neither the concentrations of nitrogen species nor the δ15N–NO3− and δ15N–NH4+ values can be used to differentiate the sources of NO3−. However, the measured δ18O–NO3ˉ values of NH4NO3 (+24.3 ± 1.7 ‰) and NO3ˉ produced from nitrification of both sources of NH4+ (−4.7 ‰) under oxic laboratory conditions enabled the distinction between these two sources of NO3ˉ. Fitting the results of a simple mixing model to the experimental data allowed the concentrations of NO3ˉ derived from NH4NO3 in fresh-blasted mine rock to be estimated. The results of this study show the application of δ18O–NO3ˉ is a valuable technique to characterize the source(s) and evolution of NO3− draining from mine rock piles.
{"title":"Defining the sources and evolution of nitrate in coal mine rock with stable isotopes of nitrate and ammonium","authors":"M. Jim Hendry, Erin Schmeling","doi":"10.1016/j.apgeochem.2025.106584","DOIUrl":"10.1016/j.apgeochem.2025.106584","url":null,"abstract":"<div><div>Elevated concentrations of nitrate (NO<sub>3</sub>ˉ) are present in many surface waters associated with coal mining throughout the world. Its presence is generally attributed to blasting using ANFO (NH<sub>4</sub>NO<sub>3</sub> and fuel oil) to access the coal. A recent study conducted by our group shows the nitrification of naturally occurring exchangeable ammonium (NH<sub>4</sub><sup>+</sup>-ex) in waste rock can be a major source of NO<sub>3</sub><sup>−</sup> compared to contributions from NO<sub>3</sub><sup>−</sup> and the nitrification of NH<sub>4</sub><sup>+</sup> originating from blast products. Here we show that neither the concentrations of nitrogen species nor the δ<sup>15</sup>N–NO<sub>3</sub><sup>−</sup> and δ<sup>15</sup>N–NH<sub>4</sub><sup>+</sup> values can be used to differentiate the sources of NO<sub>3</sub><sup>−</sup>. However, the measured δ<sup>18</sup>O–NO<sub>3</sub>ˉ values of NH<sub>4</sub>NO<sub>3</sub> (+24.3 ± 1.7 ‰) and NO<sub>3</sub>ˉ produced from nitrification of both sources of NH<sub>4</sub><sup>+</sup> (−4.7 ‰) under oxic laboratory conditions enabled the distinction between these two sources of NO<sub>3</sub>ˉ. Fitting the results of a simple mixing model to the experimental data allowed the concentrations of NO<sub>3</sub>ˉ derived from NH<sub>4</sub>NO<sub>3</sub> in fresh-blasted mine rock to be estimated. The results of this study show the application of δ<sup>18</sup>O–NO<sub>3</sub>ˉ is a valuable technique to characterize the source(s) and evolution of NO<sub>3</sub><sup>−</sup> draining from mine rock piles.</div></div>","PeriodicalId":8064,"journal":{"name":"Applied Geochemistry","volume":"193 ","pages":"Article 106584"},"PeriodicalIF":3.4,"publicationDate":"2025-10-04","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145262924","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}
Pub Date : 2025-10-03DOI: 10.1016/j.apgeochem.2025.106582
Francesco Colombi , Ewen Silvester , Aleicia Holland , Darren Baldwin , Colin MacRae , Nick Wilson , Ian Rutherfurd , James Grove , Jodi Turnbull , Mark Macklin , Peter Davies , Susan Lawrence
The Loddon River floodplains, Victoria, southeast Australia, is contaminated with high levels of As (up to 300 mg kg−1) due to re-deposited mine tailings from historical gold mining (1851–1914). Arsenic concentrations often significantly exceed Australia's sediment guidelines (ISQG-high value of 70 ppm). To determine the potential risk associated with As, this study examined the speciation of As and its mineral phase association in sediments along a 60 km stretch of the river, and investigated how As is released under redox cycling conditions. Sequential extraction procedures (SEP) revealed that As is primarily associated with crystalline Feˡˡˡoxyhydroxides (up to 40 %) and residual phases (up to 70 %). X-ray absorption spectroscopy (XAS) analyses showed that As was predominantly in its pentavalent state, existing mainly as Feˡˡˡoxyhydroxides-sorbed arsenate (Fe–AsO4), with a small amount (up to 18 %) of reduced arsenopyrite (FeAsS) present upstream reaches of the Loddon River. A column experiment simulating flooding-drying cycles was used to assess As mobility. Under reducing conditions, in the presence of a carbon source, As concentrations in the water increased dramatically, reaching up to 1300 μg L−1, far exceeding the WHO drinking water guideline of 10 μg L−1. Microbially-mediated reductive dissolution of Feˡˡˡoxyhydroxides and reduction of As from As(V) to As(III), which has lower affinity for Feˡˡˡoxyhydroxides, was likely responsible for this As release. These findings highlight the enduring presence of As contamination in floodplains impacted by historical gold mining. Furthermore, this study underlines the potential environmental and health risks posed by As in floodplain sediments, particularly as wetting and drying cycles can increase its mobility. Greater efforts are needed to assess the spatial extent of historical pollution in impacted river catchments and develop comprehensive mitigation strategies to address the widespread contamination of floodplain sediments in affected river systems globally.
澳大利亚东南部维多利亚州的洛登河洪泛区由于历史上金矿开采（1851-1914年）的尾矿再沉积而受到高水平砷的污染（高达300 mg kg - 1）。砷浓度经常大大超过澳大利亚沉积物指南（isqg高值70 ppm）。为了确定与砷相关的潜在风险，本研究检查了沿60公里河段沉积物中砷的形态及其矿物相关联，并研究了砷在氧化还原循环条件下的释放方式。顺序萃取程序（SEP）显示，As主要与结晶Fe（高达40%）和残余相（高达70%）相关。x射线吸收光谱（XAS）分析表明，砷主要以五价态存在，主要以Fe - o - o - o -羟基吸附的砷酸盐（Fe - aso4）的形式存在，在Loddon河上游存在少量（高达18%）的还原毒砂（FeAsS）。采用模拟洪水-干燥循环的柱状试验来评价As的迁移率。在还原条件下，在碳源存在的情况下，水中As浓度急剧增加，达到1300 μg L−1，远远超过WHO饮用水标准10 μg L−1。微生物介导的Fe的还原溶解和As从As(V)还原为As(III)，这可能是导致砷释放的原因。As对Fe的亲和力较低。这些发现强调了受历史上金矿开采影响的洪泛区长期存在砷污染。此外，这项研究强调了洪泛区沉积物中砷可能造成的环境和健康风险，特别是干湿循环会增加其流动性。需要作出更大努力，评估受影响河流集水区历史污染的空间程度，并制定全面的缓解战略，以解决全球受影响河流系统泛滥平原沉积物的广泛污染问题。
{"title":"Arsenic speciation and mobility in gold mining-impacted riverine sediments from the Loddon River catchment in Victoria, Australia","authors":"Francesco Colombi , Ewen Silvester , Aleicia Holland , Darren Baldwin , Colin MacRae , Nick Wilson , Ian Rutherfurd , James Grove , Jodi Turnbull , Mark Macklin , Peter Davies , Susan Lawrence","doi":"10.1016/j.apgeochem.2025.106582","DOIUrl":"10.1016/j.apgeochem.2025.106582","url":null,"abstract":"<div><div>The Loddon River floodplains, Victoria, southeast Australia, is contaminated with high levels of As (up to 300 mg kg<sup>−1</sup>) due to re-deposited mine tailings from historical gold mining (1851–1914). Arsenic concentrations often significantly exceed Australia's sediment guidelines (ISQG-high value of 70 ppm). To determine the potential risk associated with As, this study examined the speciation of As and its mineral phase association in sediments along a 60 km stretch of the river, and investigated how As is released under redox cycling conditions. Sequential extraction procedures (SEP) revealed that As is primarily associated with crystalline Feˡˡˡoxyhydroxides (up to 40 %) and residual phases (up to 70 %). X-ray absorption spectroscopy (XAS) analyses showed that As was predominantly in its pentavalent state, existing mainly as Feˡˡˡoxyhydroxides-sorbed arsenate (Fe–AsO<sub>4</sub>), with a small amount (up to 18 %) of reduced arsenopyrite (FeAsS) present upstream reaches of the Loddon River. A column experiment simulating flooding-drying cycles was used to assess As mobility. Under reducing conditions, in the presence of a carbon source, As concentrations in the water increased dramatically, reaching up to 1300 μg L<sup>−1</sup>, far exceeding the WHO drinking water guideline of 10 μg L<sup>−1</sup>. Microbially-mediated reductive dissolution of Feˡˡˡoxyhydroxides and reduction of As from As(V) to As(III), which has lower affinity for Feˡˡˡoxyhydroxides, was likely responsible for this As release. These findings highlight the enduring presence of As contamination in floodplains impacted by historical gold mining. Furthermore, this study underlines the potential environmental and health risks posed by As in floodplain sediments, particularly as wetting and drying cycles can increase its mobility. Greater efforts are needed to assess the spatial extent of historical pollution in impacted river catchments and develop comprehensive mitigation strategies to address the widespread contamination of floodplain sediments in affected river systems globally.</div></div>","PeriodicalId":8064,"journal":{"name":"Applied Geochemistry","volume":"193 ","pages":"Article 106582"},"PeriodicalIF":3.4,"publicationDate":"2025-10-03","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145262927","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}
The Marcellus shale is generally characterized by low to irreducible water saturation, and gas wells in this formation typically produce small volumes of produced water compared to the volume of fracturing fluids injected. However, some Marcellus wells produce larger volumes of high-salinity fluids months or years into production, pointing to the possibility of out-of-zone water production. To identify the origin of these high-salinity fluids, we utilize a combination of 228Ra/226Ra activity and 87Sr/86Sr ratios measured in Marcellus produced water samples. Key findings show that: i) bulk rock Th/U and Rb/Sr mass ratios, in concert with fresh water 87Sr/86Sr leachates, can be used to develop predicted 228Ra/226Ra and 87Sr/86Sr ratios of pore waters within different formations, ii) the 228Ra/226Ra and 87Sr/86Sr ratios of Marcellus produced water are dominated by the Ra2+ and Sr2+ content of downhole formation fluids and water-accessible fractions, and iii) Marcellus wells with higher water-to-gas production ratios (e.g. >1 bbl water/106 ft3 gas, or >5.6 m3 water/106 m3 gas) and elevated TDS (>100,000 mg/L) exhibit lower 87Sr/86Sr ratios, consistent with a significant contribution from exogenous Onondaga pore fluids. The approach developed here has potential utility for identifying out-of-zone water sources in other oil and gas basins.
{"title":"A combined 228Ra/226Ra and 87Sr/86Sr approach to identify the production of out-of-zone formation fluid from Marcellus shale gas wells","authors":"L.J. Molofsky , M.A. Engle , T.W. Wagner , A.S. Wylie , D.P. Fernandez","doi":"10.1016/j.apgeochem.2025.106570","DOIUrl":"10.1016/j.apgeochem.2025.106570","url":null,"abstract":"<div><div>The Marcellus shale is generally characterized by low to irreducible water saturation, and gas wells in this formation typically produce small volumes of produced water compared to the volume of fracturing fluids injected. However, some Marcellus wells produce larger volumes of high-salinity fluids months or years into production, pointing to the possibility of out-of-zone water production. To identify the origin of these high-salinity fluids, we utilize a combination of <sup>228</sup>Ra/<sup>226</sup>Ra activity and <sup>87</sup>Sr/<sup>86</sup>Sr ratios measured in Marcellus produced water samples. Key findings show that: i) bulk rock Th/U and Rb/Sr mass ratios, in concert with fresh water <sup>87</sup>Sr/<sup>86</sup>Sr leachates, can be used to develop predicted <sup>228</sup>Ra/<sup>226</sup>Ra and <sup>87</sup>Sr/<sup>86</sup>Sr ratios of pore waters within different formations, ii) the <sup>228</sup>Ra/<sup>226</sup>Ra and <sup>87</sup>Sr/<sup>86</sup>Sr ratios of Marcellus produced water are dominated by the Ra<sup>2+</sup> and Sr<sup>2+</sup> content of downhole formation fluids and water-accessible fractions, and iii) Marcellus wells with higher water-to-gas production ratios (e.g. >1 bbl water/10<sup>6</sup> ft<sup>3</sup> gas, or >5.6 m<sup>3</sup> water/10<sup>6</sup> m<sup>3</sup> gas) and elevated TDS (>100,000 mg/L) exhibit lower <sup>87</sup>Sr/<sup>86</sup>Sr ratios, consistent with a significant contribution from exogenous Onondaga pore fluids. The approach developed here has potential utility for identifying out-of-zone water sources in other oil and gas basins.</div></div>","PeriodicalId":8064,"journal":{"name":"Applied Geochemistry","volume":"194 ","pages":"Article 106570"},"PeriodicalIF":3.4,"publicationDate":"2025-10-02","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145326435","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}
Pub Date : 2025-10-02DOI: 10.1016/j.apgeochem.2025.106581
Shang Xu , Yunxuan Guo , Bingchang Liu , Haicheng Liu , Yuliang Zhang , Dong Yang
For shale oil and gas in an advanced stage of thermal maturation, defining the phase evolution and delineating phase boundaries is critical for exploration and development. This study targets the lower submember of the third member of the Shahejie Formation (Es3L) in the Zhanhua Depression, which is situated within the Bohai Bay Basin, East China, integrating detailed geological and geochemical analyses of the target stratum. The shale is dominated by carbonate-clastic mixed facies, characterized by high total organic carbon (TOC) content, dominated by Type II kerogen, strong early oil-generation potential, and significant secondary gas generation from oil cracking at high maturity. By integrating gas logging data and gas-oil ratio (GOR) measurements, two key phase boundaries were identified: approximately 4230 m for the transition from volatile oil to condensate gas, and approximately 4550 m for the transition from condensate gas to wet/dry gas. Phase evolution follows a systematic trend: the volatile oil stage is enriched in C2-C5 components, has low GOR, and is oil-phase dominated; the condensate gas stage shows elevated GOR with characteristic oil-gas coexistence; the wet/dry gas stage (Ro > 2.2 %) is methane-dominated with a sharply increasing GOR. Accurate identification of these phase boundaries provides a basis for product-type determination, reservoir stimulation design, and development strategy optimization, and offers transferable implications for phase prediction in shale systems with similar geological settings.
{"title":"Evaluation of phase for shale oil and gas using integrated geological-geochemical methods","authors":"Shang Xu , Yunxuan Guo , Bingchang Liu , Haicheng Liu , Yuliang Zhang , Dong Yang","doi":"10.1016/j.apgeochem.2025.106581","DOIUrl":"10.1016/j.apgeochem.2025.106581","url":null,"abstract":"<div><div>For shale oil and gas in an advanced stage of thermal maturation, defining the phase evolution and delineating phase boundaries is critical for exploration and development. This study targets the lower submember of the third member of the Shahejie Formation (Es3L) in the Zhanhua Depression, which is situated within the Bohai Bay Basin, East China, integrating detailed geological and geochemical analyses of the target stratum. The shale is dominated by carbonate-clastic mixed facies, characterized by high total organic carbon (TOC) content, dominated by Type II kerogen, strong early oil-generation potential, and significant secondary gas generation from oil cracking at high maturity. By integrating gas logging data and gas-oil ratio (GOR) measurements, two key phase boundaries were identified: approximately 4230 m for the transition from volatile oil to condensate gas, and approximately 4550 m for the transition from condensate gas to wet/dry gas. Phase evolution follows a systematic trend: the volatile oil stage is enriched in C<sub>2</sub>-C<sub>5</sub> components, has low GOR, and is oil-phase dominated; the condensate gas stage shows elevated GOR with characteristic oil-gas coexistence; the wet/dry gas stage (Ro > 2.2 %) is methane-dominated with a sharply increasing GOR. Accurate identification of these phase boundaries provides a basis for product-type determination, reservoir stimulation design, and development strategy optimization, and offers transferable implications for phase prediction in shale systems with similar geological settings.</div></div>","PeriodicalId":8064,"journal":{"name":"Applied Geochemistry","volume":"193 ","pages":"Article 106581"},"PeriodicalIF":3.4,"publicationDate":"2025-10-02","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145262986","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}
Pub Date : 2025-10-01DOI: 10.1016/j.apgeochem.2025.106583
Alexandre Raphael Cabral , Runsheng Yin , Di Chen , Stephanie Lohmeier , Tiago Henrique DeFerreira , Francisco Javier Rios , Bernd Lehmann
Mercury isotopes, capable of mass-dependent fractionation (δ202Hg) and mass-independent fractionation (Δ199Hg), are particularly useful in tracing ore-forming sources and metallogenic pathways in mineral deposits. Here, we apply Hg isotopes to elucidate the formation of ferromanganese sedimentary rocks in a Cenozoic, graben-like sedimentary basin. The basin was a historically important Mn supplier within the Archaean–Palaeoproterozoic Quadrilátero Ferrífero of Minas Gerais, Brazil. The rocks are enriched in Hg, up to about 9700 ppb, and have negative Δ199Hg down to −0.39‰. The negative Δ199Hg signals are consistent with the signature of terrestrial reservoirs, suggesting that the ferromanganese enrichment received Hg from terrestrial sediments, in consonance with the intracontinental setting of the basin. Ferromanganese samples with more than 5% Mn show a positive correlation of Fe/Mn vs. δ202Hg, which likely represents intracontinental basinal fluids with positive δ202Hg signals of dissolved Hg(II). Mercury was leached from terrestrial sediments and preferentially sequestered by Fe-oxide precipitates, mostly goethite. The transfer of Hg, traced by its isotopes, to ferromanganese concentrations testifies to metal recycling by Cenozoic basinal fluids within the Archaean–Palaeoproterozoic Quadrilátero Ferrífero.
{"title":"Mercury isotopes from ferromanganese rocks fingerprint metal recycling by intracontinental basinal fluids","authors":"Alexandre Raphael Cabral , Runsheng Yin , Di Chen , Stephanie Lohmeier , Tiago Henrique DeFerreira , Francisco Javier Rios , Bernd Lehmann","doi":"10.1016/j.apgeochem.2025.106583","DOIUrl":"10.1016/j.apgeochem.2025.106583","url":null,"abstract":"<div><div>Mercury isotopes, capable of mass-dependent fractionation (δ<sup>202</sup>Hg) and mass-independent fractionation (Δ<sup>199</sup>Hg), are particularly useful in tracing ore-forming sources and metallogenic pathways in mineral deposits. Here, we apply Hg isotopes to elucidate the formation of ferromanganese sedimentary rocks in a Cenozoic, graben-like sedimentary basin. The basin was a historically important Mn supplier within the Archaean–Palaeoproterozoic Quadrilátero Ferrífero of Minas Gerais, Brazil. The rocks are enriched in Hg, up to about 9700 ppb, and have negative Δ<sup>199</sup>Hg down to −0.39‰. The negative Δ<sup>199</sup>Hg signals are consistent with the signature of terrestrial reservoirs, suggesting that the ferromanganese enrichment received Hg from terrestrial sediments, in consonance with the intracontinental setting of the basin. Ferromanganese samples with more than 5% Mn show a positive correlation of Fe/Mn vs. δ<sup>202</sup>Hg, which likely represents intracontinental basinal fluids with positive δ<sup>202</sup>Hg signals of dissolved Hg(II). Mercury was leached from terrestrial sediments and preferentially sequestered by Fe-oxide precipitates, mostly goethite. The transfer of Hg, traced by its isotopes, to ferromanganese concentrations testifies to metal recycling by Cenozoic basinal fluids within the Archaean–Palaeoproterozoic Quadrilátero Ferrífero.</div></div>","PeriodicalId":8064,"journal":{"name":"Applied Geochemistry","volume":"194 ","pages":"Article 106583"},"PeriodicalIF":3.4,"publicationDate":"2025-10-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145265180","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}
Pub Date : 2025-09-30DOI: 10.1016/j.apgeochem.2025.106580
Birendra Sapkota , Eleanor J. Berryman , Nail Zagrtdenov , Richard R. Goulet
Niobium (Nb) has been identified as a critical metal important in the transition to a low-carbon economy. As the global demand for Nb mining increases, it is important to ensure that Nb mine tailings management facilities are designed to limit leaching of potentially toxic elements. In this study, we combine geochemical and mineralogical analyses to identify elements of concern in the tailings from an active Nb mine in Québec, Canada. The major components of the ten tailings samples characterized include CaO (<37.2 wt%), Fe2O3(total) (<13.7 wt%), MgO (<12.7 wt%), P2O5 (<17.1 wt%), and inorganic carbon (<35.6 wt%). The minor components include Al2O3, K2O, SrO, Nb2O5, BaO, and Na2O, in decreasing order of abundance. Mineralogical observations indicate dolomite (>40 vol%), calcite, apatite, magnetite, and ankerite to be the major (>5 vol%) phases. Nb is primarily hosted by columbite and pyrochlore. Phosphorus (P) is almost entirely hosted by apatite. Lanthanum (La), cerium (Ce), and neodymium (Nd) are also hosted primarily by apatite and to a lesser extent by parisite. The sequential extraction data are generally consistent with their expected mineral-hosts determined by element deportment calculations. Niobium remains in the residual fraction and is considered environmentally immobile. Apatite-hosted elements (mainly P, and lesser amounts of Ce, La, and Nd) are mobilized by the modified aqua regia leach step, reflecting dissolution of apatite under acidic conditions. Of note is a small proportion of Ce (<1 %) associated with weak acid soluble/carbonate fraction. Additionally, aluminum (Al) is an important element of the tailings (up to 0.9 wt%). Acidification and alkalinization of the tailings, along with the presence of complexing ligands, such as F and dissolved organic carbon, could increase Al mobility, leading to its potential toxicity to aquatic organisms. Therefore, we recommend that the design of Nb tailings management facilities is guided by an inventory of Al, P, Ce, La and Nd and their release rates, with these data iteratively applied in risk assessment models. The goal is to achieve predicted impacts consistent with water quality guidelines for the protection of aquatic life, or, if not possible, to reach concentrations that are as low as reasonably achievable.
{"title":"Geochemical and mineralogical investigations of niobium mine tailings in Québec, Canada","authors":"Birendra Sapkota , Eleanor J. Berryman , Nail Zagrtdenov , Richard R. Goulet","doi":"10.1016/j.apgeochem.2025.106580","DOIUrl":"10.1016/j.apgeochem.2025.106580","url":null,"abstract":"<div><div>Niobium (Nb) has been identified as a critical metal important in the transition to a low-carbon economy. As the global demand for Nb mining increases, it is important to ensure that Nb mine tailings management facilities are designed to limit leaching of potentially toxic elements. In this study, we combine geochemical and mineralogical analyses to identify elements of concern in the tailings from an active Nb mine in Québec, Canada. The major components of the ten tailings samples characterized include CaO (<37.2 wt%), Fe<sub>2</sub>O<sub>3(total)</sub> (<13.7 wt%), MgO (<12.7 wt%), P<sub>2</sub>O<sub>5</sub> (<17.1 wt%), and inorganic carbon (<35.6 wt%). The minor components include Al<sub>2</sub>O<sub>3</sub>, K<sub>2</sub>O, SrO, Nb<sub>2</sub>O<sub>5</sub>, BaO, and Na<sub>2</sub>O, in decreasing order of abundance. Mineralogical observations indicate dolomite (>40 vol%), calcite, apatite, magnetite, and ankerite to be the major (>5 vol%) phases. Nb is primarily hosted by columbite and pyrochlore. Phosphorus (P) is almost entirely hosted by apatite. Lanthanum (La), cerium (Ce), and neodymium (Nd) are also hosted primarily by apatite and to a lesser extent by parisite. The sequential extraction data are generally consistent with their expected mineral-hosts determined by element deportment calculations. Niobium remains in the residual fraction and is considered environmentally immobile. Apatite-hosted elements (mainly P, and lesser amounts of Ce, La, and Nd) are mobilized by the modified aqua regia leach step, reflecting dissolution of apatite under acidic conditions. Of note is a small proportion of Ce (<1 %) associated with weak acid soluble/carbonate fraction. Additionally, aluminum (Al) is an important element of the tailings (up to 0.9 wt%). Acidification and alkalinization of the tailings, along with the presence of complexing ligands, such as F and dissolved organic carbon, could increase Al mobility, leading to its potential toxicity to aquatic organisms. Therefore, we recommend that the design of Nb tailings management facilities is guided by an inventory of Al, P, Ce, La and Nd and their release rates, with these data iteratively applied in risk assessment models. The goal is to achieve predicted impacts consistent with water quality guidelines for the protection of aquatic life, or, if not possible, to reach concentrations that are as low as reasonably achievable.</div></div>","PeriodicalId":8064,"journal":{"name":"Applied Geochemistry","volume":"193 ","pages":"Article 106580"},"PeriodicalIF":3.4,"publicationDate":"2025-09-30","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145262928","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}
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