Pub Date : 2025-11-12DOI: 10.1016/j.apgeochem.2025.106626
Amandine Dumas , Laurent De Windt , Ivan Serclerat , David S. Kosson , Bruno Huet , Florence Sanchez , Nouffou Tapsoba
This study introduces iron oxalate dihydrate (FeOx) as an innovative and highly effective treatment for the chemical stabilization of trace levels of Mo and Sb in soils. The effectiveness of the FeOx treatment was evaluated for a Mo-contaminated limestone tunnel sludge (LTS) and Mo/Sb-contaminated industrial wasteland soil (IWS) with organic matter. FeOx reactivity and oxyanion retention were investigated using TGA, XRD, optical microscopy and standardized US/EU leaching tests. Mineralogical changes and the pH-dependence on Mo sorption were further analyzed by geochemical modeling. Under near-neutral pH and oxidizing conditions, FeOx dissociates, releasing Fe2+ and C2O42− ions. The Fe2+ is subsequently oxidized to Fe3+, forming poorly crystallized hydrous ferric oxides (HFOs) that are uniformly distributed. This process induces acidification, partially dissolving calcite and releasing Ca2+, which reacts with C2O42− to form calcium oxalate monohydrate (whewellite). Mo and Sb immobilization occurs through sorption onto HFOs, achieving effective retention at ≥1 wt% FeOx for LTS and ≥5 wt% for IWS, meeting European inert waste standards. The fast transformation of FeOx into HFOs and whewellite enables Mo and Sb retention within 6 h. Overall, leaching decreased by 67 % for Mo in LTS with 2 wt% FeOx, and by 88 % for Sb and 90 % for Mo in IWS with 6 wt% FeOx. Retention stability was observed at pH ≤ 8, with no significant competition with sulfate or acetate ions. These results highlight FeOx as a promising solution for industrial applications requiring rapid chemical stabilization of contaminants. However, further research is needed to assess long-term stability under variable redox conditions.
{"title":"Molybdenum and Antimony immobilization by iron oxalate salt in contaminated soils","authors":"Amandine Dumas , Laurent De Windt , Ivan Serclerat , David S. Kosson , Bruno Huet , Florence Sanchez , Nouffou Tapsoba","doi":"10.1016/j.apgeochem.2025.106626","DOIUrl":"10.1016/j.apgeochem.2025.106626","url":null,"abstract":"<div><div>This study introduces iron oxalate dihydrate (FeOx) as an innovative and highly effective treatment for the chemical stabilization of trace levels of Mo and Sb in soils. The effectiveness of the FeOx treatment was evaluated for a Mo-contaminated limestone tunnel sludge (LTS) and Mo/Sb-contaminated industrial wasteland soil (IWS) with organic matter. FeOx reactivity and oxyanion retention were investigated using TGA, XRD, optical microscopy and standardized US/EU leaching tests. Mineralogical changes and the pH-dependence on Mo sorption were further analyzed by geochemical modeling. Under near-neutral pH and oxidizing conditions, FeOx dissociates, releasing Fe<sup>2+</sup> and C<sub>2</sub>O<sub>4</sub><sup>2−</sup> ions. The Fe<sup>2+</sup> is subsequently oxidized to Fe<sup>3+</sup>, forming poorly crystallized hydrous ferric oxides (HFOs) that are uniformly distributed. This process induces acidification, partially dissolving calcite and releasing Ca<sup>2+</sup>, which reacts with C<sub>2</sub>O<sub>4</sub><sup>2−</sup> to form calcium oxalate monohydrate (whewellite). Mo and Sb immobilization occurs through sorption onto HFOs, achieving effective retention at ≥1 wt% FeOx for LTS and ≥5 wt% for IWS, meeting European inert waste standards. The fast transformation of FeOx into HFOs and whewellite enables Mo and Sb retention within 6 h. Overall, leaching decreased by 67 % for Mo in LTS with 2 wt% FeOx, and by 88 % for Sb and 90 % for Mo in IWS with 6 wt% FeOx. Retention stability was observed at pH ≤ 8, with no significant competition with sulfate or acetate ions. These results highlight FeOx as a promising solution for industrial applications requiring rapid chemical stabilization of contaminants. However, further research is needed to assess long-term stability under variable redox conditions.</div></div>","PeriodicalId":8064,"journal":{"name":"Applied Geochemistry","volume":"195 ","pages":"Article 106626"},"PeriodicalIF":3.4,"publicationDate":"2025-11-12","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145577444","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 : 2025-11-12DOI: 10.1016/j.apgeochem.2025.106622
Kevin Schmidt , Martin Oeser , André Stechern , Christian Ostertag-Henning
<div><div>Lithium (Li) production from brines circulating in deep sedimentary basins as a byproduct of deep geothermal energy use could contribute to cover a significant proportion of the increasing global Li demand. Additionally, co-produced formation waters from the oil and gas industry represent another potential source of Li that could be utilized in a similar manner. Feasibility assessments for these operations require estimates for a possible Li replenishment by the recirculation of the Li-depleted brine after aboveground Li extraction. Currently, information about Li contents in reservoir rocks, the main Li carrier mineral phases of the respective reservoirs and possible Li release reactions are scarce.</div><div>In this study, drill core material from two geothermal wells, Groβ Buchholz Gt1 (Triassic Bunter sandstone) in the North German Basin (NGB) and Soultz-sous-Forêts EPS1 (granitic basement) in the Upper Rhine Graben (URG), as well as from the gas well Unterlüß T1 (Triassic Bunter sandstone) in the NGB, were investigated for both Li contents and Li release behavior. The bulk rock Li concentrations of the sample collection vary slightly in the range of 47–79 ppm. The main Li-bearing minerals were identified to be (i) chlorite (575 ppm) and illite (68 ppm) for Bunter sandstone samples and (ii) biotite for the Soultz sous forêts granite with maximum concentrations of up to 597 ppm. By grain-size fraction analysis phyllosilicates in the clay fraction were confirmed to exhibit the highest Li concentrations for the sandstones. To explore the Li release behavior, hydrothermal experiments were conducted at conditions of low enthalpy geothermal reservoirs (100–160 °C, 370 bar) for 14–60 days. The above described core samples were investigated by using ground rock powder and for one example the clay fraction. These solids were mixed with either bi-dist. H<sub>2</sub>O or synthetic brine in Au capsules or in flexible Au–Ti reaction cells and installed in high pressure reactors. Results of the experiments show that a nearly constant Li concentration was attained after 6–12 days in all experiments with the bi-dist. H<sub>2</sub>O. In these experiments, a total of 0.2–0.7 % of the Li contained in the granitic sample and 0.9–3.2 % of the Li contained in the Bunter sandstone samples were leached into the solution. It was found that different reaction mechanisms involving silicate minerals, as well as halogenide and carbonate minerals, contribute to the Li release. The experiment conducted with a clay fraction consisting mainly of illite and chlorite showed an enhanced leach of 6.9 % Li, indicating that Li is preferentially released by illite and chlorite in all experiments. Variations in temperature point only to a minor influence on the amount of Li released in the experiments. Experiments conducted with a synthetic brine instead of bi-dist. H<sub>2</sub>O stimulated the release of Li by a factor of up to 2 for the Bunter sandstone samples and by a
{"title":"Hydrothermal experiments at in-situ conditions to identify Li release reactions by water-mineral interactions in deep sedimentary basins of the North German Basin and Upper Rhine Graben","authors":"Kevin Schmidt , Martin Oeser , André Stechern , Christian Ostertag-Henning","doi":"10.1016/j.apgeochem.2025.106622","DOIUrl":"10.1016/j.apgeochem.2025.106622","url":null,"abstract":"<div><div>Lithium (Li) production from brines circulating in deep sedimentary basins as a byproduct of deep geothermal energy use could contribute to cover a significant proportion of the increasing global Li demand. Additionally, co-produced formation waters from the oil and gas industry represent another potential source of Li that could be utilized in a similar manner. Feasibility assessments for these operations require estimates for a possible Li replenishment by the recirculation of the Li-depleted brine after aboveground Li extraction. Currently, information about Li contents in reservoir rocks, the main Li carrier mineral phases of the respective reservoirs and possible Li release reactions are scarce.</div><div>In this study, drill core material from two geothermal wells, Groβ Buchholz Gt1 (Triassic Bunter sandstone) in the North German Basin (NGB) and Soultz-sous-Forêts EPS1 (granitic basement) in the Upper Rhine Graben (URG), as well as from the gas well Unterlüß T1 (Triassic Bunter sandstone) in the NGB, were investigated for both Li contents and Li release behavior. The bulk rock Li concentrations of the sample collection vary slightly in the range of 47–79 ppm. The main Li-bearing minerals were identified to be (i) chlorite (575 ppm) and illite (68 ppm) for Bunter sandstone samples and (ii) biotite for the Soultz sous forêts granite with maximum concentrations of up to 597 ppm. By grain-size fraction analysis phyllosilicates in the clay fraction were confirmed to exhibit the highest Li concentrations for the sandstones. To explore the Li release behavior, hydrothermal experiments were conducted at conditions of low enthalpy geothermal reservoirs (100–160 °C, 370 bar) for 14–60 days. The above described core samples were investigated by using ground rock powder and for one example the clay fraction. These solids were mixed with either bi-dist. H<sub>2</sub>O or synthetic brine in Au capsules or in flexible Au–Ti reaction cells and installed in high pressure reactors. Results of the experiments show that a nearly constant Li concentration was attained after 6–12 days in all experiments with the bi-dist. H<sub>2</sub>O. In these experiments, a total of 0.2–0.7 % of the Li contained in the granitic sample and 0.9–3.2 % of the Li contained in the Bunter sandstone samples were leached into the solution. It was found that different reaction mechanisms involving silicate minerals, as well as halogenide and carbonate minerals, contribute to the Li release. The experiment conducted with a clay fraction consisting mainly of illite and chlorite showed an enhanced leach of 6.9 % Li, indicating that Li is preferentially released by illite and chlorite in all experiments. Variations in temperature point only to a minor influence on the amount of Li released in the experiments. Experiments conducted with a synthetic brine instead of bi-dist. H<sub>2</sub>O stimulated the release of Li by a factor of up to 2 for the Bunter sandstone samples and by a","PeriodicalId":8064,"journal":{"name":"Applied Geochemistry","volume":"195 ","pages":"Article 106622"},"PeriodicalIF":3.4,"publicationDate":"2025-11-12","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145577393","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 : 2025-11-11DOI: 10.1016/j.apgeochem.2025.106624
Guojie Feng , Zhiqin Li , Chunli Su , Xianjun Xie , Weili Ge , Yiqun Gan , Zhaohui Luo , Kunfu Pi , Hongjie Pan , Yanhui Gao , Yanmei Yang
Hetao Plain is one of three major agricultural irrigation areas in China, where groundwater salinization and associated high fluoride concentrations (F− >1.5 mg/L) pose serious threats to ecological sustainable development. A total of 487 groundwater samples were collected from the Hetao Plain to explore the spatial variability, sources, and dominant hydrogeochemical processes controlling groundwater F− enrichment. Furthermore, the genetic modes of high F− groundwater occurring in different hydrogeological units were clarified and compared using hydrochemical analysis and factor analysis. The results show groundwater F− concentrations range from <0.05 mg/L (detection limit) to 7.83 mg/L, with 46.6 % and 7.9 % of samples in the Qiantao Plain and Houtao Plain, respectively, having concentrations exceeding 1.5 mg/L. High F- groundwater exhibited high spatial variability and occurred in shallow aquifers with depth less than 60 m, which is mainly regulated by the fluoride sources and hydrogeological conditions. Sediments in the Houtao Plain mainly originate from alluvial deposits of the Yellow River, whereas in the Qiantao Plain originate from fluoride-rich bedrocks/minerals of the eastern Yin Mountains. Different material sources are the primary factor causing spatial variability of groundwater F− concentrations in the two plains. High F− groundwater in the Qiantao Plain is characterized by leaching-enrichment type, while in the Houtao Plain is dominated by leaching-enrichment type in the piedmont alluvial-pluvial fan (Zone C) and a combination of leaching-enrichment type and evaporation-concentration type in the riparian zone of the Yellow River and north margin of the Ordos Plateau (Zone E), respectively. The vital factors responsible for F− enrichment are abundant sources, favorable hydrogeological conditions, alkaline soda water type, and strong evaporation. The study clearly distinguished the difference in sediment material sources between the two adjacent plains, achieving a deepening understanding of the genetic models from the basin to specific hydrogeological units. These findings can provide a theoretical basis for safe groundwater supply in arid regions.
{"title":"Provenance and geogenic modes of high-fluoride groundwater occurred in various sedimentary environments: constraints of hydrogeology and hydrogeochemstry","authors":"Guojie Feng , Zhiqin Li , Chunli Su , Xianjun Xie , Weili Ge , Yiqun Gan , Zhaohui Luo , Kunfu Pi , Hongjie Pan , Yanhui Gao , Yanmei Yang","doi":"10.1016/j.apgeochem.2025.106624","DOIUrl":"10.1016/j.apgeochem.2025.106624","url":null,"abstract":"<div><div>Hetao Plain is one of three major agricultural irrigation areas in China, where groundwater salinization and associated high fluoride concentrations (F<sup>−</sup> >1.5 mg/L) pose serious threats to ecological sustainable development. A total of 487 groundwater samples were collected from the Hetao Plain to explore the spatial variability, sources, and dominant hydrogeochemical processes controlling groundwater F<sup>−</sup> enrichment. Furthermore, the genetic modes of high F<sup>−</sup> groundwater occurring in different hydrogeological units were clarified and compared using hydrochemical analysis and factor analysis. The results show groundwater F<sup>−</sup> concentrations range from <0.05 mg/L (detection limit) to 7.83 mg/L, with 46.6 % and 7.9 % of samples in the Qiantao Plain and Houtao Plain, respectively, having concentrations exceeding 1.5 mg/L. High F- groundwater exhibited high spatial variability and occurred in shallow aquifers with depth less than 60 m, which is mainly regulated by the fluoride sources and hydrogeological conditions. Sediments in the Houtao Plain mainly originate from alluvial deposits of the Yellow River, whereas in the Qiantao Plain originate from fluoride-rich bedrocks/minerals of the eastern Yin Mountains. Different material sources are the primary factor causing spatial variability of groundwater F<sup>−</sup> concentrations in the two plains. High F<sup>−</sup> groundwater in the Qiantao Plain is characterized by leaching-enrichment type, while in the Houtao Plain is dominated by leaching-enrichment type in the piedmont alluvial-pluvial fan (Zone C) and a combination of leaching-enrichment type and evaporation-concentration type in the riparian zone of the Yellow River and north margin of the Ordos Plateau (Zone E), respectively. The vital factors responsible for F<sup>−</sup> enrichment are abundant sources, favorable hydrogeological conditions, alkaline soda water type, and strong evaporation. The study clearly distinguished the difference in sediment material sources between the two adjacent plains, achieving a deepening understanding of the genetic models from the basin to specific hydrogeological units. These findings can provide a theoretical basis for safe groundwater supply in arid regions.</div></div>","PeriodicalId":8064,"journal":{"name":"Applied Geochemistry","volume":"195 ","pages":"Article 106624"},"PeriodicalIF":3.4,"publicationDate":"2025-11-11","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145518707","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 : 2025-11-11DOI: 10.1016/j.apgeochem.2025.106627
Weixin Zhang , Sandong Zhou , Qiaoyun Cheng , Ruibin Chen , Hang Liu , Xinyu Liu , Hongbo Miao , Dameng Liu , Detian Yan , Hua Wang
The Paleogene Hothouse climate significantly affects the paleoenvironment and regional climate of lake basins globally. A Hothouse climate is recorded in the Paleogene Shuangyang Formation within Yitong Basin. The first member of the Shuangyang Formation forms excellent hydrocarbon source rocks. Under the influence of a Hothouse climate state during the Paleogene, the paleoenvironmental controls on organic matter accumulation within the Shuangyang shale remain to be fully understood. This study employs an integrated analysis of mineralogy, lithology, and organic/inorganic geochemistry to divide the Shuangyang shale into three parts: lower, middle, and upper. Paleoenvironmental conditions for each part are reconstructed using diverse geochemical proxies, and the differential accumulation of organic matter is explored. The findings indicate that the Shuangyang shale is rich in quartz mineral (average = 49.35 %), with the proportion of organic-rich shale (total organic carbon, TOC ≥ 2 wt. %) accounting for 60 %. A reducing environment and suitable salinity are the basic conditions for the preservation and accumulation of organic matter. The development of organic-rich shale is driven by a humid paleoclimate, strong terrigenous detrital concentration, and high paleoproductivity. Organic matter accumulation in the lower and upper parts is driven by middle-high paleoproductivity and strong terrigenous detrital concentration, respectively. The stable development of organic-rich shale in the middle part is driven by a humid paleoclimate, moderate terrigenous detrital concentration, and medium paleoproductivity. This study reveals the driving mechanisms behind organic matter differential accumulation in various sedimentary paleoenvironments, providing valuable insights for lacustrine shale oil exploration.
{"title":"Paleoenvironment-driven organic matter differential accumulation: New data from the Paleogene lacustrine shale in Yitong basin, NE China","authors":"Weixin Zhang , Sandong Zhou , Qiaoyun Cheng , Ruibin Chen , Hang Liu , Xinyu Liu , Hongbo Miao , Dameng Liu , Detian Yan , Hua Wang","doi":"10.1016/j.apgeochem.2025.106627","DOIUrl":"10.1016/j.apgeochem.2025.106627","url":null,"abstract":"<div><div>The Paleogene Hothouse climate significantly affects the paleoenvironment and regional climate of lake basins globally. A Hothouse climate is recorded in the Paleogene Shuangyang Formation within Yitong Basin. The first member of the Shuangyang Formation forms excellent hydrocarbon source rocks. Under the influence of a Hothouse climate state during the Paleogene, the paleoenvironmental controls on organic matter accumulation within the Shuangyang shale remain to be fully understood. This study employs an integrated analysis of mineralogy, lithology, and organic/inorganic geochemistry to divide the Shuangyang shale into three parts: lower, middle, and upper. Paleoenvironmental conditions for each part are reconstructed using diverse geochemical proxies, and the differential accumulation of organic matter is explored. The findings indicate that the Shuangyang shale is rich in quartz mineral (average = 49.35 %), with the proportion of organic-rich shale (total organic carbon, TOC ≥ 2 wt. %) accounting for 60 %. A reducing environment and suitable salinity are the basic conditions for the preservation and accumulation of organic matter. The development of organic-rich shale is driven by a humid paleoclimate, strong terrigenous detrital concentration, and high paleoproductivity. Organic matter accumulation in the lower and upper parts is driven by middle-high paleoproductivity and strong terrigenous detrital concentration, respectively. The stable development of organic-rich shale in the middle part is driven by a humid paleoclimate, moderate terrigenous detrital concentration, and medium paleoproductivity. This study reveals the driving mechanisms behind organic matter differential accumulation in various sedimentary paleoenvironments, providing valuable insights for lacustrine shale oil exploration.</div></div>","PeriodicalId":8064,"journal":{"name":"Applied Geochemistry","volume":"195 ","pages":"Article 106627"},"PeriodicalIF":3.4,"publicationDate":"2025-11-11","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145518709","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 : 2025-11-10DOI: 10.1016/j.apgeochem.2025.106623
Chengpeng Sun , Gang Hu , Huawei Wang , Zhiyuan Zhou , Xupeng Hu , Xinxin Li
Sedimentary branched glycerol dialkyl glycerol tetraether (brGDGT) lipids are commonly used to reconstruct continental paleotemperatures. However, the influence of varied terrestrial sources of brGDGTs, either from highland or floodplain, in a river basin on paleotemperature reconstruction has not been addressed. In this study, brGDGT lipids were analyzed in a gravity core taken from the active channel of the Lower Bengal Fan to evaluate the source effect on paleotemperature reconstruction during three distinct stages over the past 15 ka: stage I (15–10 ka), stage II (10–2 ka), and stage III (2–0 ka). The positive correlation between smectite/(illite + chlorite) and methylation index of 5-methyl branched tetraethers (MBT’5ME) (stage I: R2 = 0.64, p < 0.01; stages II and III: R2 = 0.69, p < 0.01) indicated that the reconstructed paleotemperatures were intimately associated with shifts in sediment sources. At stage I, enriched highland sediment sources with low smectite/(illite + chlorite) ratios at the low sea level during the Bølling-Allerød event led to an underestimation of the paleotemperature (15 °C) compared to the Younger Dryas (17 °C) event. During late stage II (6–2 ka), gradually waning highland sediments indicated by the increasing smectite/(illite + chlorite) ratio, along with rising sea level and deltaic subsidence, resulted in a progressive overestimation of the reconstructed temperatures (19–20 °C) than the early stage II (18 °C at 10–6 ka). Stage III (2–0 ka) marked an incrementally increasing contribution from highland sediments due to progressive river relocation, resulting in a cooling paleotemperature reconstruction from 20 °C to 18 °C. All pointed to the importance of distinguishing varied terrestrial sources of branched tetraether lipids in large-elevation river basins to reconstruct paleotemperature by the MBT’5ME proxy.
沉积支链甘油二烷基甘油四醚（brGDGT）脂质通常用于重建大陆古温度。然而，不同陆源（高原或河漫滩）brGDGTs对古地温重建的影响尚未得到解决。本文对下孟加拉扇活动通道重力岩心中的brGDGT脂质进行了分析，评价了在过去15 ka的3个不同阶段(第1阶段（15 - 10 ka）、第2阶段（10-2 ka）和第3阶段（2-0 ka）源对古地温重建的影响。蒙脱石/（伊利石+绿泥石）与5-甲基支化四醚（MBT’5ME）甲基化指数呈正相关（第一阶段：R2 = 0.64, p < 0.01；第二和第三阶段：R2 = 0.69, p < 0.01），表明重建的古温度与沉积物来源的转移密切相关。在第1阶段，b ølling- allero ød事件期间，低海平面上富含蒙脱石/（伊利石+绿泥石）比的高原沉积物源导致古温度（15°C）低于新仙女木事件（17°C）。在第二阶段晚期（6-2 ka），蒙脱石/（伊利石+绿泥石）比值增加，高原沉积物逐渐减弱，加之海平面上升和三角洲沉降，导致重建温度（19-20℃）比第二阶段早期（10-6 ka 18℃）逐渐高估。第三阶段（2 ~ 0 ka）由于河流的逐渐迁移，高原沉积物的贡献逐渐增加，导致古温度从20°C下降到18°C。这些结果都表明，区分高海拔河流流域不同陆源的支链四醚类脂质对于用MBT’5ME代替物重建古地温具有重要意义。
{"title":"Varied terrestrial sources of branched tetraether lipids in sediments of the Lower Bengal Fan affect the temperature reconstruction proxy","authors":"Chengpeng Sun , Gang Hu , Huawei Wang , Zhiyuan Zhou , Xupeng Hu , Xinxin Li","doi":"10.1016/j.apgeochem.2025.106623","DOIUrl":"10.1016/j.apgeochem.2025.106623","url":null,"abstract":"<div><div>Sedimentary branched glycerol dialkyl glycerol tetraether (brGDGT) lipids are commonly used to reconstruct continental paleotemperatures. However, the influence of varied terrestrial sources of brGDGTs, either from highland or floodplain, in a river basin on paleotemperature reconstruction has not been addressed. In this study, brGDGT lipids were analyzed in a gravity core taken from the active channel of the Lower Bengal Fan to evaluate the source effect on paleotemperature reconstruction during three distinct stages over the past 15 ka: stage I (15–10 ka), stage II (10–2 ka), and stage III (2–0 ka). The positive correlation between smectite/(illite + chlorite) and methylation index of 5-methyl branched tetraethers (MBT’<sub>5ME</sub>) (stage I: R<sup>2</sup> = 0.64, <em>p</em> < 0.01; stages II and III: R<sup>2</sup> = 0.69, <em>p</em> < 0.01) indicated that the reconstructed paleotemperatures were intimately associated with shifts in sediment sources. At stage I, enriched highland sediment sources with low smectite/(illite + chlorite) ratios at the low sea level during the Bølling-Allerød event led to an underestimation of the paleotemperature (15 °C) compared to the Younger Dryas (17 °C) event. During late stage II (6–2 ka), gradually waning highland sediments indicated by the increasing smectite/(illite + chlorite) ratio, along with rising sea level and deltaic subsidence, resulted in a progressive overestimation of the reconstructed temperatures (19–20 °C) than the early stage II (18 °C at 10–6 ka). Stage III (2–0 ka) marked an incrementally increasing contribution from highland sediments due to progressive river relocation, resulting in a cooling paleotemperature reconstruction from 20 °C to 18 °C. All pointed to the importance of distinguishing varied terrestrial sources of branched tetraether lipids in large-elevation river basins to reconstruct paleotemperature by the MBT’<sub>5ME</sub> proxy.</div></div>","PeriodicalId":8064,"journal":{"name":"Applied Geochemistry","volume":"195 ","pages":"Article 106623"},"PeriodicalIF":3.4,"publicationDate":"2025-11-10","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145518700","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 : 2025-11-04DOI: 10.1016/j.apgeochem.2025.106613
Olivia Terry , Derek Caro , Tianxiao Shen , Shaina Kelly , Janet Dewey , John P. Kaszuba
Unconventional hydrocarbon reservoirs are commonly hydraulically fractured with acidified fresh water. Most development of unconventional reservoirs occurs in rural environments with little surface water, meaning fresh water is transported from other regions or is extracted from local groundwater and aquifers. Use of formation fluid extracted from active or depleted reservoirs has been proposed, however formation fluid is notoriously high in total dissolved solids, which is thought to be unfavorable for subsurface geochemical reactions. Additionally, some fluid stabilizers, which alter fluid viscosity, are less effective in fluid with high total dissolved solids. Gel-based fluid stabilizers, such as crosslink, are effective in high ionic strength fluids, however viscosity is best maintained at high pH (>8). High-pH fracturing fluid interactions with reservoir rock have not been well studied compared to acidic fluids. Field studies can provide long-term insight into efficiency of high-pH fracturing fluid in reservoir rock, however geochemical reactions between reservoir rock and injected fluid are known to occur on the order of a few days, during well shut-in (days to weeks). Two laboratory experiments were performed to analyze the potential for geochemical reactions between reservoir rock and high-pH fracturing fluid within the shut-in timescale. Core from the Niobrara Formation (marl and chalk), a productive unconventional reservoir in the Denver-Julesburg Basin, Colorado, USA, and high-pH hydraulic fracturing fluid (pH = 10.1) were reacted at reservoir conditions (113 °C, 27.5 MPa) for ∼35 days. Temporal evolution of aqueous geochemistry and thermodynamic analysis of both experiments indicates 1) fluid accesses nanopores; 2) pH decreases to circumneutral values as geochemical reactions shift from fluid-to rock-dominated; and 3) no significant secondary precipitation is observed. The absence of secondary mineralization indicates limited reaction between high-pH hydraulic fracturing fluid and Niobrara Formation marl and chalk and suggests that geochemical fluid-rock interactions will not impact matrix porosity and permeability during extraction of fluids from unconventional reservoirs under similar conditions. Additionally, results are compared to acidic fracturing fluid studies to assess the response of carbonate-bearing reservoir rock to pH and relative concentrations of calcium and magnesium.
{"title":"Geochemical evaluation of fluid-rock interactions between high-pH hydraulic fracturing fluid and carbonate-rich reservoirs: A case study of the Niobrara Formation, Denver-Julesburg Basin, Colorado, USA","authors":"Olivia Terry , Derek Caro , Tianxiao Shen , Shaina Kelly , Janet Dewey , John P. Kaszuba","doi":"10.1016/j.apgeochem.2025.106613","DOIUrl":"10.1016/j.apgeochem.2025.106613","url":null,"abstract":"<div><div>Unconventional hydrocarbon reservoirs are commonly hydraulically fractured with acidified fresh water. Most development of unconventional reservoirs occurs in rural environments with little surface water, meaning fresh water is transported from other regions or is extracted from local groundwater and aquifers. Use of formation fluid extracted from active or depleted reservoirs has been proposed, however formation fluid is notoriously high in total dissolved solids, which is thought to be unfavorable for subsurface geochemical reactions. Additionally, some fluid stabilizers, which alter fluid viscosity, are less effective in fluid with high total dissolved solids. Gel-based fluid stabilizers, such as crosslink, are effective in high ionic strength fluids, however viscosity is best maintained at high pH (>8). High-pH fracturing fluid interactions with reservoir rock have not been well studied compared to acidic fluids. Field studies can provide long-term insight into efficiency of high-pH fracturing fluid in reservoir rock, however geochemical reactions between reservoir rock and injected fluid are known to occur on the order of a few days, during well shut-in (days to weeks). Two laboratory experiments were performed to analyze the potential for geochemical reactions between reservoir rock and high-pH fracturing fluid within the shut-in timescale. Core from the Niobrara Formation (marl and chalk), a productive unconventional reservoir in the Denver-Julesburg Basin, Colorado, USA, and high-pH hydraulic fracturing fluid (pH = 10.1) were reacted at reservoir conditions (113 °C, 27.5 MPa) for ∼35 days. Temporal evolution of aqueous geochemistry and thermodynamic analysis of both experiments indicates 1) fluid accesses nanopores; 2) pH decreases to circumneutral values as geochemical reactions shift from fluid-to rock-dominated; and 3) no significant secondary precipitation is observed. The absence of secondary mineralization indicates limited reaction between high-pH hydraulic fracturing fluid and Niobrara Formation marl and chalk and suggests that geochemical fluid-rock interactions will not impact matrix porosity and permeability during extraction of fluids from unconventional reservoirs under similar conditions. Additionally, results are compared to acidic fracturing fluid studies to assess the response of carbonate-bearing reservoir rock to pH and relative concentrations of calcium and magnesium.</div></div>","PeriodicalId":8064,"journal":{"name":"Applied Geochemistry","volume":"195 ","pages":"Article 106613"},"PeriodicalIF":3.4,"publicationDate":"2025-11-04","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145518708","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 : 2025-11-04DOI: 10.1016/j.apgeochem.2025.106614
Eduard Ghiorghiu , Iulia Ajtai , Ildiko M. Martonos , Mustafa Hmoudah , Alexandra Orban , Alexandru Lupulescu , Liana Spulber , Alexandra I. Cozma , Ștefan Șfabu , Roxana Moga , Călin Baciu , Giuseppe Etiope
Fossil methane and ethane, produced and accumulated in sedimentary basins, enter the atmosphere through both artificial leakage during gas-oil production activity (fugitive emissions) and natural seepage (gas naturally migrating to the surface). Well leaks, such as accidental blowouts during or after drilling, can be easily recognized by direct ground-based observations, and prompt remedial actions render them as short-term gas emission events, with no significant atmospheric impact. We report a complex case of long-term fugitive emission that developed away from the drilling site, with gas exhaling from the ground together with natural gas seepage. The site refers to the first producing gas well in Transylvania, drilled in 1909 in the Sărmăşel microbial gas field. We combined (a) a historical reconstruction of the events, based on early documents of that period, (b) geological setting analysis (stratigraphy and fault locations), and (c) present-day observation of the surface gas manifestations, through measurements of methane and ethane flux from the ground, and their concentration in the soil, shallow aquifer and surface waters. We deduce that after the closure of the well in 1911, due to gas pressure increase, the gas leaked from the well bottom, penetrated anticlinal strata and entered a natural seepage system along a fault. The leaked, stray gas mixed with the gas naturally migrating to the surface from the underlying reservoirs, producing surface craters with burning vents, still active today. It is likely that the natural seepage system amplified and is still sustaining the post-drilling leak. We estimated that, since 1911, the total amounts of methane and ethane injected from the ground to the atmosphere are at least in the order of 104 t and one t, respectively. Sărmăşel gas manifestation, today leaking >20 kg CH4 h−1, is a super-emitter according to the definition used for fugitive emissions in Romania. This study represents an example of the risk of uncontrolled, persistent and elusive fugitive emissions that may occur when drilling is executed within a natural seepage system. The presence of ethane in the aquifer and soil supports the hypothesis that the Transylvanian Basin may host a deep thermogenic system.
沉积盆地生产和积累的化石甲烷和乙烷通过油气开采过程中的人工泄漏（逸散排放）和自然渗流（气体自然迁移到地面）进入大气。油井泄漏，如钻井过程中或钻井后的意外井喷，可以通过直接的地面观测很容易地识别出来，并迅速采取补救措施，使其成为短期气体排放事件，对大气没有重大影响。我们报告了一个复杂的长期无组织排放的案例，从钻井现场发展，气体从地下呼出，同时天然气渗流。该地点指的是1909年在srurrm微生物气田钻探的Transylvania的第一口生产气井。我们结合了(a)基于该时期早期文件的事件的历史重建，(b)地质背景分析（地层和断层位置），以及(c)通过测量来自地面的甲烷和乙烷通量及其在土壤、浅层含水层和地表水中的浓度对地表气体表现的当前观察。1911年关井后，由于瓦斯压力升高，瓦斯从井底泄漏，穿过背斜地层，沿断层进入自然渗流体系。泄漏的散失气体与地下储层的气体混合，自然地迁移到地表，形成了带有燃烧喷口的地表陨石坑，这些火山口至今仍然活跃。自然渗流系统可能扩大，仍在持续钻后泄漏。我们估计，自1911年以来，从地面注入大气的甲烷和乙烷的总量至少分别为104吨和1吨。根据罗马尼亚对无组织排放的定义，今天泄漏20 kg CH4 h - 1的srurrm气体表现为超级排放者。这项研究代表了在自然渗流系统中进行钻井时可能发生的不受控制、持续和难以捉摸的逸散性排放风险的一个例子。含水层和土壤中乙烷的存在支持了特兰西瓦尼亚盆地可能拥有深层产热系统的假设。
{"title":"Long-term emission of methane and ethane to the atmosphere from hybrid natural seepage and well leakage in the Sărmăşel gas field (Romania)","authors":"Eduard Ghiorghiu , Iulia Ajtai , Ildiko M. Martonos , Mustafa Hmoudah , Alexandra Orban , Alexandru Lupulescu , Liana Spulber , Alexandra I. Cozma , Ștefan Șfabu , Roxana Moga , Călin Baciu , Giuseppe Etiope","doi":"10.1016/j.apgeochem.2025.106614","DOIUrl":"10.1016/j.apgeochem.2025.106614","url":null,"abstract":"<div><div>Fossil methane and ethane, produced and accumulated in sedimentary basins, enter the atmosphere through both artificial leakage during gas-oil production activity (fugitive emissions) and natural seepage (gas naturally migrating to the surface). Well leaks, such as accidental blowouts during or after drilling, can be easily recognized by direct ground-based observations, and prompt remedial actions render them as short-term gas emission events, with no significant atmospheric impact. We report a complex case of long-term fugitive emission that developed away from the drilling site, with gas exhaling from the ground together with natural gas seepage. The site refers to the first producing gas well in Transylvania, drilled in 1909 in the Sărmăşel microbial gas field. We combined (a) a historical reconstruction of the events, based on early documents of that period, (b) geological setting analysis (stratigraphy and fault locations), and (c) present-day observation of the surface gas manifestations, through measurements of methane and ethane flux from the ground, and their concentration in the soil, shallow aquifer and surface waters. We deduce that after the closure of the well in 1911, due to gas pressure increase, the gas leaked from the well bottom, penetrated anticlinal strata and entered a natural seepage system along a fault. The leaked, stray gas mixed with the gas naturally migrating to the surface from the underlying reservoirs, producing surface craters with burning vents, still active today. It is likely that the natural seepage system amplified and is still sustaining the post-drilling leak. We estimated that, since 1911, the total amounts of methane and ethane injected from the ground to the atmosphere are at least in the order of 10<sup>4</sup> t and one t, respectively. Sărmăşel gas manifestation, today leaking >20 kg CH<sub>4</sub> h<sup>−1</sup>, is a super-emitter according to the definition used for fugitive emissions in Romania. This study represents an example of the risk of uncontrolled, persistent and elusive fugitive emissions that may occur when drilling is executed within a natural seepage system. The presence of ethane in the aquifer and soil supports the hypothesis that the Transylvanian Basin may host a deep thermogenic system.</div></div>","PeriodicalId":8064,"journal":{"name":"Applied Geochemistry","volume":"195 ","pages":"Article 106614"},"PeriodicalIF":3.4,"publicationDate":"2025-11-04","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145465127","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 : 2025-11-04DOI: 10.1016/j.apgeochem.2025.106612
Victòria Moreno , Joan Bach , Mario Zarroca , Eulàlia Masana , Lluís Font , Rogelio Linares
Radon and CO2 in groundwater, radon and thoron in soil, soil radon exhalation rates, and electrical resistivity imaging were measured in the Alhama de Murcia Fault area. The study aims to (i) characterize radon levels in groundwater and soil and (ii) assess whether variations in gas emissions are related to the presence of an active fault. Forty water sampling points exhibited 222Rn concentrations ranging from 0.4 to 66.8 Bq/L, while 22 soil points along two profiles crossing the fault showed low annual mean values of (8 ± 1) kBq m−3 and (12 ± 2) kBq m−3. Soil radon exhalation rates at the two profiles, (36 ± 8) and (53 ± 12) Bq m−2 h−1, respectively, are consistent with these concentrations. Spatial variability of soil radon along both profiles, [1–22] kBq m−3, appears associated with the main fault location. Temporal variations of 222Rn recorded at a monitoring station from early 2013 to mid-2015 closely match punctual measurements. While fluctuations are largely controlled by barometric pressure and atmospheric temperature, detailed analyses combining multiple radon anomaly detection methods indicate a possible influence of nearby seismic events.
{"title":"Radon levels in soil and in groundwater in the Alhama de Murcia fault area, Spain","authors":"Victòria Moreno , Joan Bach , Mario Zarroca , Eulàlia Masana , Lluís Font , Rogelio Linares","doi":"10.1016/j.apgeochem.2025.106612","DOIUrl":"10.1016/j.apgeochem.2025.106612","url":null,"abstract":"<div><div>Radon and CO<sub>2</sub> in groundwater, radon and thoron in soil, soil radon exhalation rates, and electrical resistivity imaging were measured in the Alhama de Murcia Fault area. The study aims to (i) characterize radon levels in groundwater and soil and (ii) assess whether variations in gas emissions are related to the presence of an active fault. Forty water sampling points exhibited <sup>222</sup>Rn concentrations ranging from 0.4 to 66.8 Bq/L, while 22 soil points along two profiles crossing the fault showed low annual mean values of (8 ± 1) kBq m<sup>−3</sup> and (12 ± 2) kBq m<sup>−3</sup>. Soil radon exhalation rates at the two profiles, (36 ± 8) and (53 ± 12) Bq m<sup>−2</sup> h<sup>−1</sup>, respectively, are consistent with these concentrations. Spatial variability of soil radon along both profiles, [1–22] kBq m<sup>−3</sup>, appears associated with the main fault location. Temporal variations of <sup>222</sup>Rn recorded at a monitoring station from early 2013 to mid-2015 closely match punctual measurements. While fluctuations are largely controlled by barometric pressure and atmospheric temperature, detailed analyses combining multiple radon anomaly detection methods indicate a possible influence of nearby seismic events.</div></div>","PeriodicalId":8064,"journal":{"name":"Applied Geochemistry","volume":"195 ","pages":"Article 106612"},"PeriodicalIF":3.4,"publicationDate":"2025-11-04","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145465125","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 : 2025-11-03DOI: 10.1016/j.apgeochem.2025.106611
Fiona J. Weiss, Leon Keim, Kai Wendel, Holger Class
In reactive transport modeling, an accurate understanding of reaction rates is essential; discrepancies in parameter reporting can greatly affect simulation results. This technical note identifies an issue with the reporting of rate parameters for carbonate mineral dissolution in a widely used database for reactive transport modeling based on Palandri and Kharaka (2004). Specifically, the reaction order was reported with respect to the partial pressure rather than the activity of , causing a considerable overestimation of reaction timescales. We demonstrate the implications of this error by simulating a calcite dissolution batch experiment using Reaktoro and DuMuX and comparing the results to experimental data. By adjusting the parameter to align with established literature, we demonstrate an improved fit between simulated and experimental data. Discrepancies in reaction timescales were reduced by an order of magnitude, emphasizing the importance of regular validation of simulations with experimental data.
{"title":"Implementation Pitfalls for carbonate mineral dissolution — A technical note","authors":"Fiona J. Weiss, Leon Keim, Kai Wendel, Holger Class","doi":"10.1016/j.apgeochem.2025.106611","DOIUrl":"10.1016/j.apgeochem.2025.106611","url":null,"abstract":"<div><div>In reactive transport modeling, an accurate understanding of reaction rates is essential; discrepancies in parameter reporting can greatly affect simulation results. This technical note identifies an issue with the reporting of rate parameters for carbonate mineral dissolution in a widely used database for reactive transport modeling based on Palandri and Kharaka (2004). Specifically, the reaction order was reported with respect to the partial pressure <span><math><mrow><mi>P</mi><mrow><mo>(</mo><msub><mrow><mi>CO</mi></mrow><mrow><mn>2</mn></mrow></msub><mo>)</mo></mrow></mrow></math></span> rather than the activity of <span><math><mrow><msub><mrow><mi>H</mi></mrow><mrow><mn>2</mn></mrow></msub><msubsup><mrow><mi>CO</mi></mrow><mrow><mn>3</mn></mrow><mrow><mo>∗</mo></mrow></msubsup></mrow></math></span>, causing a considerable overestimation of reaction timescales. We demonstrate the implications of this error by simulating a calcite dissolution batch experiment using Reaktoro and DuMuX and comparing the results to experimental data. By adjusting the parameter to align with established literature, we demonstrate an improved fit between simulated and experimental data. Discrepancies in reaction timescales were reduced by an order of magnitude, emphasizing the importance of regular validation of simulations with experimental data.</div></div>","PeriodicalId":8064,"journal":{"name":"Applied Geochemistry","volume":"196 ","pages":"Article 106611"},"PeriodicalIF":3.4,"publicationDate":"2025-11-03","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145555196","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 : 2025-10-31DOI: 10.1016/j.apgeochem.2025.106610
Zhao Wei , Baoying Wang , Longchen Zhu , Yihang Hong , Zhenfei Wang , Hao Yan , Yongbo Peng , Shohei Hattori , Huiming Bao
Phosphate oxygen isotope composition (δ18O(PO43−)) provides critical insights into the sources and transformation processes of phosphorus in aquatic environments. However, the low PO43− concentration (<1 μM) in natural freshwater necessitates large sample volumes (25–100 L) and tedious procedures in the conventional δ18O(PO43−) analysis method that uses thermal conversion/elemental analysis linked to a gas–source isotope-ratio mass spectrometer (TC/EA–IRMS). Here, we report a method for analyzing δ18O(PO43−) using sub-liter volumes (∼1 L) of freshwater. The approach uses a well-established zirconium-oxide-gel method to adsorb dissolved PO43−, followed by purification of PO43− via anion exchange resin and isotope measurement by Electrospray Ionization Orbitrap Mass Spectrometry (ESI–Orbitrap–MS). The whole pretreatment procedure results in a δ18O(PO43−) accuracy of ±0.8 ‰, within the analytical uncertainty of the ESI–Orbitrap–MS measurement. Calibration with TC/EA–IRMS produced nearly a 1:1 regression (slope 0.96, residual <0.9 ‰). Tests on freshwater samples from a natural lake achieved an accuracy of ±0.3 ‰. The method reduces sample volume by three orders of magnitude compared to the TC/EA–IRMS method, opening up opportunities to trace PO43− cycling and source apportionment in an unprecedented temporal and spatial resolution.
{"title":"A sub-liter pretreatment method for Orbitrap–based freshwater phosphate oxygen isotope measurement","authors":"Zhao Wei , Baoying Wang , Longchen Zhu , Yihang Hong , Zhenfei Wang , Hao Yan , Yongbo Peng , Shohei Hattori , Huiming Bao","doi":"10.1016/j.apgeochem.2025.106610","DOIUrl":"10.1016/j.apgeochem.2025.106610","url":null,"abstract":"<div><div>Phosphate oxygen isotope composition (<em>δ</em><sup>18</sup>O(PO<sub>4</sub><sup>3−</sup>)) provides critical insights into the sources and transformation processes of phosphorus in aquatic environments. However, the low PO<sub>4</sub><sup>3−</sup> concentration (<1 μM) in natural freshwater necessitates large sample volumes (25–100 L) and tedious procedures in the conventional <em>δ</em><sup>18</sup>O(PO<sub>4</sub><sup>3−</sup>) analysis method that uses thermal conversion/elemental analysis linked to a gas–source isotope-ratio mass spectrometer (TC/EA–IRMS). Here, we report a method for analyzing <em>δ</em><sup>18</sup>O(PO<sub>4</sub><sup>3−</sup>) using sub-liter volumes (∼1 L) of freshwater. The approach uses a well-established zirconium-oxide-gel method to adsorb dissolved PO<sub>4</sub><sup>3−</sup>, followed by purification of PO<sub>4</sub><sup>3−</sup> via anion exchange resin and isotope measurement by Electrospray Ionization Orbitrap Mass Spectrometry (ESI–Orbitrap–MS). The whole pretreatment procedure results in a <em>δ</em><sup>18</sup>O(PO<sub>4</sub><sup>3−</sup>) accuracy of ±0.8 ‰, within the analytical uncertainty of the ESI–Orbitrap–MS measurement. Calibration with TC/EA–IRMS produced nearly a 1:1 regression (slope 0.96, residual <0.9 ‰). Tests on freshwater samples from a natural lake achieved an accuracy of ±0.3 ‰. The method reduces sample volume by three orders of magnitude compared to the TC/EA–IRMS method, opening up opportunities to trace PO<sub>4</sub><sup>3−</sup> cycling and source apportionment in an unprecedented temporal and spatial resolution.</div></div>","PeriodicalId":8064,"journal":{"name":"Applied Geochemistry","volume":"194 ","pages":"Article 106610"},"PeriodicalIF":3.4,"publicationDate":"2025-10-31","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145463422","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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