Applied Geochemistry最新文献_第9页

Comparative analysis of one-dimensional convolutional neural network and predictive raster averaging for MVT Pb–Zn mineralization using the weighted class distribution evaluation framework 基于加权类分布评价框架的一维卷积神经网络与预测栅格平均在MVT铅锌矿化中的对比分析

IF 3.4 3区地球科学 Q1 GEOCHEMISTRY & GEOPHYSICS

Applied Geochemistry

Pub Date : 2025-10-21 DOI: 10.1016/j.apgeochem.2025.106595

Soran Qaderi, Abbas Maghsoudi

This study explores the use of geochemical and remote sensing data to predict areas with high mineralization potential in Mississippi Valley-Type (MVT) Pb–Zn deposits in western Semnan, Iran. Two methods were applied: 1DCNN (1D Convolutional Neural Network) and PRA (Predictive Raster Averaging). The 1DCNN model, known for its capacity to learn complex spatial patterns from high-dimensional data, was trained on satellite imagery and geochemical data, producing a probability map indicating potential mineralized zones. The simpler PRA method combined multiple raster layers through averaging, providing a computationally efficient alternative for generating prospectivity maps. Evaluation metrics, including Weighted Class Distribution (WCD) Method, ROC-AUC, and Feature Importance, were used to assess the performance of both methods. The WCD method was applied to evaluate the distribution of known mineral deposits across different probability classes, while ROC-AUC was used to measure the 1DCNN model's ability to distinguish between mineralized and non-mineralized areas. Feature Importance analysis helped identify which geochemical and remote sensing features contributed most to the predictions made by the 1DCNN model. Results showed that the 1DCNN model had higher accuracy in identifying the most promising mineralization zones, with 68.75 % of known deposits falling into the highest probability class, occupying 8 % of the study area. The PRA model, though less refined, successfully highlighted regions with mineral potential, albeit with a broader spread across probability classes. This research contributes to understanding the trade-offs between artificial intelligence-based and traditional mapping methods for mineral exploration, providing valuable insights for future studies in resource prospectivity.

利用地球化学和遥感资料对伊朗西Semnan地区密西西比河谷型铅锌矿床进行了高成矿潜力区预测。采用了两种方法：1DCNN （1D卷积神经网络）和PRA（预测光栅平均）。1DCNN模型以其从高维数据中学习复杂空间模式的能力而闻名，该模型在卫星图像和地球化学数据上进行了训练，生成了指示潜在矿化带的概率图。更简单的PRA方法通过平均将多个栅格层组合在一起，为生成远景图提供了一种计算效率更高的替代方法。评估指标，包括加权类分布（WCD）方法、ROC-AUC和特征重要性，用于评估两种方法的性能。WCD方法用于评估已知矿床在不同概率类别中的分布，而ROC-AUC用于衡量1DCNN模型区分矿化区和非矿化区的能力。特征重要性分析有助于确定哪些地球化学和遥感特征对1DCNN模型的预测贡献最大。结果表明，1DCNN模型对最有希望成矿带的识别精度较高，68.75%的已知矿床属于最高概率类，占研究面积的8%。PRA模型虽然不太完善，但成功地突出了具有矿产潜力的区域，尽管在概率类别中有更广泛的分布。该研究有助于理解基于人工智能和传统测绘方法在矿产勘查中的权衡，为未来的资源远景研究提供有价值的见解。

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引用次数: 0

Interactions between basalt and CO2-saturated water at varying temperatures (100°C–300 °C) in a duplex reactor 玄武岩与二氧化碳饱和水在不同温度（100°C - 300°C）下的相互作用

IF 3.4 3区地球科学 Q1 GEOCHEMISTRY & GEOPHYSICS

Applied Geochemistry

Pub Date : 2025-10-17 DOI: 10.1016/j.apgeochem.2025.106593

Heejun Yang , Akira Ueda , Hideki Kuramitz , Amane Terai

This study experimentally investigated basalt–CO₂–water interactions at temperatures between 100 °C and 300 °C through flow-through experiments, with a focus on changes in solution composition and the formation of secondary minerals under varying temperature conditions relevant to enhanced geothermal systems (EGSs). A duplex reactor system was developed for the first time to simulate temperature variations in the reservoir, particularly in the vicinity of caprock.

The Mg²⁺ and Fe²⁺ concentrations were higher at lower temperatures (100 °C and 150 °C), whereas the other major cations exhibited an increasing trend with temperature. In the duplex reactor test (reactor 1 = 100 °C; reactor 2 = 250 °C; Fr6), the Mg²⁺ and Fe²⁺ concentrations were lower, suggesting potential Mg²⁺ and Fe²⁺ precipitation in high-temperature conditions. The SEM-EDS results primarily identified aluminium oxyhydroxide and clay minerals at temperatures above 250 °C, which were mainly oversaturated in beidellite, montmorillonite, illite, kaolinite, and boehmite. Conversely, at temperatures below 150 °C, primarily aluminium oxyhydroxide minerals were identified, which were oversaturated in boehmite. However, among the clay minerals, kaolinite mainly exhibited oversaturation, while the other minerals remained undersaturated.

The results of the duplex reactor test suggest that Mg²⁺ and Fe²⁺, which dissolved under lower-temperature conditions, may lead to the precipitation of clay minerals upon migration to higher-temperature regions within the EGS reservoir. This behavior is attributed to the decreasing solubility constants of these minerals with increasing temperature.

本研究通过流动实验研究了玄武岩-二氧化碳-水在100°C至300°C之间的相互作用，重点研究了与增强型地热系统（EGSs）相关的不同温度条件下溶液成分的变化和次生矿物的形成。首次开发了双反应器系统，以模拟储层中的温度变化，特别是盖层附近的温度变化。Mg2+和Fe2+浓度在较低温度（100°C和150°C）下较高，而其他主要阳离子随温度升高呈上升趋势。在双反应器试验中（反应器1 = 100°C，反应器2 = 250°C, Fr6）， Mg2+和Fe2+浓度较低，表明高温条件下Mg2+和Fe2+可能析出。SEM-EDS结果主要鉴定了250℃以上温度下的氢氧化铝和粘土矿物，其主要过饱和存在于贝德石、蒙脱土、伊利石、高岭石和薄水铝石中。相反，在低于150°C的温度下，发现主要是氢氧化铝矿物，它们在薄铝石中过饱和。而粘土矿物中，高岭石主要表现为过饱和，其他矿物则表现为欠饱和。双反应器试验结果表明，低温条件下溶解的Mg2+和Fe2+可能导致黏土矿物向EGS储层高温区域迁移时析出。这是由于这些矿物的溶解度常数随着温度的升高而降低。

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引用次数: 0

Chemical and isotopic variations of geothermal water record the enhanced water-rock interactions after seismicity in the western capital region of China 地热水化学和同位素变化记录了中国西部首都地区地震活动后水岩相互作用的增强

IF 3.4 3区地球科学 Q1 GEOCHEMISTRY & GEOPHYSICS

Applied Geochemistry

Pub Date : 2025-10-17 DOI: 10.1016/j.apgeochem.2025.106592

Shujuan Su , Chang Lu , Ying Li , Xiaocheng Zhou , Mingbo Yang , Zhaofei Liu , Jia Ren

Earthquake-related hydrochemical and isotopic changes are widely reported in active seismic areas. To investigate the hydrochemical anomalies related to earthquake events in the Beijing region of China (capital area), 960 water samples were collected from the Houhaoyao and Songshan geothermal wells, and the Chicheng spring every three days between 2022 and 2024. Major ion concentrations and stable isotope compositions (δ²H and δ¹⁸O) in the geothermal water were determined. The results showed anomalies in Na⁺, SO₄²⁻ and Cl⁻ concentrations during seismic activity periods. The δ²H and δ¹⁸O values ranged from −95 ‰ to −84 ‰ and from −13.5 ‰ to −11.0 ‰, respectively, indicating a meteoric origin for the sampled water. Variations in δ²H and δ¹⁸O values of 0.2 ‰–0.8 ‰ emerged one or two months before and after low-magnitude seismicity within 50 km of quake epicentres between November 2023 and January 2024. The helium and carbon isotopic compositions of the water samples suggested that He and CO₂ gases released from the geothermal wells mainly originated from the mantle and crustal, indicating a relationship between local deep faults and geothermal water circulation. It was concluded that the variations of the hydrochemical and isotopic compositions in geothermal waters were related to crustal fractures caused by seismic activity. Ground water stored in different reservoirs would flow along active faults, forming a channel system, then mix together. This resulted in changes to the water's chemical composition during earthquakes. By capturing anomalies in long-term geothermal observation wells during seismic evolution, this work provides insights into fault-fluid coupling in the capital area of China and other similar active seismic areas.

地震相关的水化学和同位素变化在地震活动区被广泛报道。为了研究北京地区（首都地区）地震相关的水化学异常，在2022 - 2024年间，每3天采集一次后好窑、松山地热井和赤城泉的960个水样。测定了地热水中主要离子浓度和稳定同位素（δ2H和δ18O）组成。结果表明，Na+、SO42−和Cl−浓度在地震活动期出现异常。δ2H值在- 95‰~ - 84‰之间，δ18O值在- 13.5‰~ - 11.0‰之间，为大气源。2023年11月至2024年1月，震源50 km范围内低震级地震前后1 ~ 2个月，δ2H和δ18O值出现0.2‰~ 0.8‰的变化。水样的氦、碳同位素组成表明，地热井释放的He和CO2气体主要来源于地幔和地壳，表明了局部深断裂与地热水循环的关系。地热水水化学和同位素组成的变化与地震活动引起的地壳断裂有关。储存在不同水库中的地下水将沿着活动断层流动，形成一个水道系统，然后混合在一起。这导致地震期间水的化学成分发生了变化。通过在地震演化过程中捕获长期地热观测井的异常，对中国首都地区和其他类似地震活跃区的断层-流体耦合提供了新的认识。

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引用次数: 0

Petroleum-fuelled methanogenesis and microbial hydrocarbon oxidation at an abandoned oil well 废弃油井中以石油为燃料的甲烷生成与微生物烃类氧化

IF 3.4 3区地球科学 Q1 GEOCHEMISTRY & GEOPHYSICS

Applied Geochemistry

Pub Date : 2025-10-13 DOI: 10.1016/j.apgeochem.2025.106589

Martin Blumenberg, Sebastian Jordan , Georg Scheeder, Martin Krüger, Stefan Schloemer

Here, we present a geochemical study of the soil above a plugged oil well (‘Elwerath’), which was drilled in the early 1920s and is located near Hannover (Germany). At this site ∼40 mg methane per hour is emitted. Geochemical analyses of the soil gas confirm the presence of thermogenic natural gas (with up to 8 % methane and 600 ppm ethane in the soil gas) and the δ¹³C of the methane indicates that most of the emitted methane is thermogenic (δ¹³C −47.1 ‰ VPDB). In addition to natural gas, we also found petroleum in the soil, accounting for up to 80 % of the total soil organic carbon. Detailed soil gas and organic geochemical analyses of extracts from the soil confirm a strong similarity with the old petroleum reservoir. Our data suggest a complex mosaic of gas-altering effects that cannot be explained by admixture with biogenic methane alone, but are rather dominated by microbial degradation of oil and natural gas components (e.g. propane oxidation). Most likely O₂ availability controls the microbial degradation of petroleum close to the ‘Elwerath’ well, because the strongest degree of degradation, with the lowest petroleum content, is found in the upper, well aerated soil horizons. The gas geochemistry and isotopic composition of the soil gases also indicate anaerobic processes, such as methanogenesis, probably with petroleum as carbon source. These processes must have taken place significantly deeper than the top meter sampled, where O₂ was still detectable. CO₂ emissions appear to be negatively affected by the oil contamination, most likely due to the inhibition of natural microbial respiration by toxic effects. While processes in the deeper biosphere appear to play a role here, it is clear that the microbial processes in the soil surrounding the well also regulate the composition and quantity of oil and gas. In conclusion, (i) the high degree of degradation of natural gas and oil in the soil, and (ii) the low methane emissions, indicate that only little hydrocarbon is leaking and that a ‘microbial hydrocarbon filter’ is established and active.

在这里，我们展示了对一口堵塞的油井（“Elwerath”）上方土壤的地球化学研究，该油井位于德国汉诺威附近，于20世纪20年代初钻探。在这个地方，每小时排放约40毫克甲烷。土壤气体的地球化学分析证实了热成因天然气的存在（土壤气体中甲烷含量高达8%，乙烷含量为600 ppm），甲烷的δ13C表明大部分甲烷是热成因的（δ13C−47.1‰VPDB）。除了天然气，我们还在土壤中发现了石油，占土壤有机碳总量的80%。详细的土壤气体分析和土壤萃取物的有机地球化学分析证实了其与古油藏的相似性。我们的数据表明，复杂的气体改变效应不能单独用生物甲烷的混合物来解释，而是由石油和天然气成分的微生物降解（例如丙烷氧化）所主导。最有可能的是，氧的有效性控制着Elwerath井附近石油的微生物降解，因为在通风良好的上层土壤层中，降解程度最强，石油含量最低。土壤气体的地球化学和同位素组成也显示出厌氧过程，如甲烷生成，可能以石油为碳源。这些过程一定发生在比顶部采样更深的地方，那里仍然可以检测到氧气。二氧化碳排放似乎受到石油污染的负面影响，很可能是由于有毒作用抑制了天然微生物的呼吸作用。虽然深层生物圈的过程似乎在这里发挥了作用，但很明显，油井周围土壤中的微生物过程也调节着石油和天然气的组成和数量。综上所述，(i)天然气和石油在土壤中的降解程度高，（ii）甲烷排放量低，表明只有很少的碳氢化合物泄漏，“微生物碳氢化合物过滤器”已经建立并起作用。

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引用次数: 0

Physicochemical, hydromechanical, and Cs retention properties of Ca-bentonite treated with Ca(OH)2 saturated solution at 150°C for up to 2 years Ca(OH)2饱和溶液在150°C下处理长达2年的Ca-膨润土的物理化学、流体力学和Cs保留性能

IF 3.4 3区地球科学 Q1 GEOCHEMISTRY & GEOPHYSICS

Applied Geochemistry

Pub Date : 2025-10-08 DOI: 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.

了解膨润土缓冲材料在100°C下水泥渗滤液存在下的性能，是优化高放射性废物深层地质处置库设计所必需的。本研究研究了Ca(OH)2饱和溶液在150°C下对Ca-膨润土的影响，重点研究了膨润土的矿物学变化对其物理化学、膨胀和水力以及铯（Cs）保留性能的影响，这些性能是缓冲材料的关键属性。包括x射线衍射、核磁共振、热重和差热分析在内的分析技术表明水合硅酸钙（CSH）的形成。尽管发生了这种变化，但阳离子交换和Cs保留能力在很大程度上没有受到影响。经水热处理的膨润土压实试样（干密度：1.6 Mg/m3）的膨胀压力试验表明，膨润土的膨胀压力降低。然而，水力导电性没有显著差异。压实的膨润土样品的x射线光电子能谱分析表明，在一年的渗透期内，样品中没有检测到流出物，因此样品仍在吸收流体。总的来说，Ca(OH)2饱和溶液在150°C下处理两年的Ca-膨润土，CSH的形成很少，物理化学、水力和Cs保留性能的变化很小，膨胀压力略有降低。

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引用次数: 0

Geochemical evolution of sediments in Huanghua Depression, North China Plain: Implications for weathering, provenance, and paleoclimate since the Oligocene 华北平原黄骅坳陷渐新世以来沉积物地球化学演化及其风化、物源和古气候意义

IF 3.4 3区地球科学 Q1 GEOCHEMISTRY & GEOPHYSICS

Applied Geochemistry

Pub Date : 2025-10-08 DOI: 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.

本文对华北平原黄骅坳陷CZKZ01钻孔的91份沉积物样品进行地球化学分析，探讨渐新世以来的古气候演化和沉积物物源。主要元素、痕量元素和稀土元素分析用于评价化学风化强度、物源特征和古环境变化。结果表明，渐新世沉积物经历了强烈的化学风化作用（CIA = 80.1），随着时间的推移，CIA逐渐减小（上新世CIA = 67.4，中新世CIA = 66.4，第四纪CIA = 63.0）。沉积物的主要来源为长英质火成岩，稀土元素分析表明，太行山变质沉积-火山岩和中生代酸性火成岩以及附近隆起的中生代沉积单元对沉积物的贡献，形成了类似于上陆壳（UCC）的成分。在120 m以上深度，元素组成更加均匀，反映了现代黄河输入的增加。氧化还原敏感元素比值表明渐新世以来的沉积环境普遍为含氧环境，中新世开始由微咸环境逐渐转变为淡水环境。该研究为研究晚新生代华北平原的沉积过程和气候演化提供了重要依据。

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引用次数: 0

Geochemical survey of uranium in catchment sediments and prediction of mineralization prospects along the Sino-Mongolian border region 中蒙边境地区汇水沉积物中铀的地球化学测量及成矿远景预测

IF 3.4 3区地球科学 Q1 GEOCHEMISTRY & GEOPHYSICS

Applied Geochemistry

Pub Date : 2025-10-08 DOI: 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.

中蒙边境地区位于亚洲内陆的蒙古高原上，是一个重要的成矿带，是全球斑岩铜、金、钼三大成矿带之一。虽然蒙中两国铀资源丰富，但对中蒙边境地区特别是本地区单元素铀的整体空间分布特征、影响因素及找矿区缺乏深入的研究。本研究通过1:10万地球化学填图，确定了该区铀资源的分布特征和成矿潜力，填补了这一研究空白。为了实现这一目标，系统地收集了10453个流域沉积物样本，并对其进行了地球化学分析。这些分析阐明了该地区铀的分布特征，探讨了铀的富集机制。结果显示，样品中的铀浓度范围很广，从0.07到335.52 ppm，中位数和平均值分别为2.10和2.54 ppm。利用地球化学块圈定法，确定了21个高铀含量区（约1000 km2）为地球化学省及以上。此外，还圈定了9个铀地球化学区块，其中1个区块达到地球化学域大小（10万km2）。在此基础上，综合分析了区域地质构造特征、矿产组合、成矿条件和开采潜力，确定了5个具有较大找矿潜力的铀矿远景区。这些找矿区的圈定为今后找矿指明了方向，为区域矿产资源的开发利用提供了可靠的地球化学依据。

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引用次数: 0

Scheelite (CaWO4) leaching in mild conditions via heptatungstate sorption by MgAl– Layered Double Hydroxide MgAl -层状双氢氧化物吸附七钨酸钠在温和条件下浸出白钨矿（CaWO4）

IF 3.4 3区地球科学 Q1 GEOCHEMISTRY & GEOPHYSICS

Applied Geochemistry

Pub Date : 2025-10-08 DOI: 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.

用无机阴离子交换剂mgal层状双氢氧化物（LDH）从纯白钨矿（CaWO4）中提取七钨酸盐（W7O246−）的可能性进行了研究。溶解/吸附步骤的最佳pH为5，解吸步骤使用pH为11的碳酸盐溶液进行。在LDH/白钨矿比为1.8的条件下，浸出时间为24 h，可提取高达30%的钨，而白钨矿在此条件下几乎不溶。假设了两种吸附机制：七丁二酸盐离子与LDH的碳酸盐离子交换，以及LDH溶解释放的铝离子沉淀W（VI）。因此，这项工作为利用LDH通过低环境足迹工艺从白钨矿中提取和回收钨提供了概念证明。

引用次数: 0

Defining the sources and evolution of nitrate in coal mine rock with stable isotopes of nitrate and ammonium 用硝铵稳定同位素确定煤矿岩石中硝态氮的来源和演化

IF 3.4 3区地球科学 Q1 GEOCHEMISTRY & GEOPHYSICS

Applied Geochemistry

Pub Date : 2025-10-04 DOI: 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.

在世界范围内，与煤炭开采有关的许多地表水中硝酸盐（NO3 - h）浓度升高。它的存在通常归因于使用铵油（NH4NO3和燃料油）爆破以接近煤炭。我们小组最近进行的一项研究表明，与NO3 -和来自爆炸产物的NH4+的硝化作用相比，废石中自然产生的交换性铵（NH4+-ex）的硝化作用可能是NO3 -的主要来源。研究表明，无论是氮种浓度还是δ15N-NO3−和δ15N-NH4 +值都不能用来区分NO3−的来源。然而，在实验室缺氧条件下测定的NH4NO3（+24.3±1.7‰）和两种NH4+源硝化作用产生的NO3 - h的δ18O-NO3 - h的值（−4.7‰）可以区分这两种NO3 - h的来源。将简单混合模型的结果与实验数据拟合，可以估算出新爆矿山岩石中NH4NO3衍生的NO3浓度。研究结果表明，δ18O-NO3 -的应用是表征矿山岩桩NO3−排放源和演化的一种有价值的技术。

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引用次数: 0

Arsenic speciation and mobility in gold mining-impacted riverine sediments from the Loddon River catchment in Victoria, Australia 澳大利亚维多利亚州洛登河流域金矿开采影响的河流沉积物中砷的形态和流动性

IF 3.4 3区地球科学 Q1 GEOCHEMISTRY & GEOPHYSICS

Applied Geochemistry

Pub Date : 2025-10-03 DOI: 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。

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