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Search Results (747)

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Keywords = stable water isotopes

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11 pages, 711 KiB  
Article
Cadmium Accumulation and Regulation in the Freshwater Mussel Anodonta woodiana
by Xiubao Chen, Chao Song, Jiazhen Jiang, Tao Jiang, Junren Xue, Ibrahim Bah, Mengying Gu, Meiyi Wang and Shunlong Meng
Toxics 2025, 13(8), 646; https://doi.org/10.3390/toxics13080646 - 30 Jul 2025
Viewed by 169
Abstract
Cadmium (Cd) pollution poses a serious threat to freshwater ecosystems. The freshwater mussel Anodonta woodiana is increasingly used as a bioindicator for monitoring Cd pollution in aquatic environments. However, the primary routes of Cd accumulation in A. woodiana remain unclear, and the molecular [...] Read more.
Cadmium (Cd) pollution poses a serious threat to freshwater ecosystems. The freshwater mussel Anodonta woodiana is increasingly used as a bioindicator for monitoring Cd pollution in aquatic environments. However, the primary routes of Cd accumulation in A. woodiana remain unclear, and the molecular regulatory mechanisms underlying Cd accumulation are poorly understood. To address these gaps, this study employed a novel stable isotope dual-tracer technique to trace Cd from water (waterborne 112Cd) and the green alga Chlorella vulgaris (dietary 113Cd) during the simultaneous exposure experiment. Comparative transcriptomic analysis was then conducted to characterize molecular responses in A. woodiana following Cd exposure. The results showed that although newly accumulated 112Cd and 113Cd increased with exposure concentration and duration, the relative importance of 112Cd (91.6 ± 2.8%) was significantly higher than that of 113Cd (8.4 ± 2.8%) (p < 0.05). Cd exposure induced differentially expressed genes primarily enriched in the metabolic processes, cellular processes, and/or the ubiquitin-mediated proteolysis pathway. Within the ubiquitin-mediated proteolysis pathway, TRIP12 (E3 ubiquitin-protein ligase TRIP12) and Cul5 (cullin-5) were significantly upregulated. The findings will provide critical insights for interpreting Cd biomonitoring data in freshwater environments using mussels as bioindicators. Full article
(This article belongs to the Special Issue The Impact of Heavy Metals on Aquatic Ecosystems)
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24 pages, 5270 KiB  
Article
Ecophysiological Keys to the Success of a Native-Expansive Mediterranean Species in Threatened Coastal Dune Habitats
by Mario Fernández-Martínez, Carmen Jiménez-Carrasco, Mari Cruz Díaz Barradas, Juan B. Gallego-Fernández and María Zunzunegui
Plants 2025, 14(15), 2342; https://doi.org/10.3390/plants14152342 - 29 Jul 2025
Viewed by 204
Abstract
Range-expanding species, or neonatives, are native plants that spread beyond their original range due to recent climate or human-induced environmental changes. Retama monosperma was initially planted near the Guadalquivir estuary for dune stabilisation. However, changes in the sedimentary regime and animal-mediated dispersal have [...] Read more.
Range-expanding species, or neonatives, are native plants that spread beyond their original range due to recent climate or human-induced environmental changes. Retama monosperma was initially planted near the Guadalquivir estuary for dune stabilisation. However, changes in the sedimentary regime and animal-mediated dispersal have facilitated its exponential expansion, threatening endemic species and critical dune habitats. The main objective of this study was to identify the key functional traits that may explain the competitive advantage and rapid spread of R. monosperma in coastal dune ecosystems. We compared its seasonal responses with those of three co-occurring woody species, two native (Juniperus phoenicea and J. macrocarpa) and one naturalised (Pinus pinea), at two sites differing in groundwater availability within a coastal dune area (Doñana National Park, Spain). We measured water relations, leaf traits, stomatal conductance, photochemical efficiency, stable isotopes, and shoot elongation in 12 individuals per species. Repeated-measures ANOVA showed significant effects of species and species × season interaction for relative water content, shoot elongation, effective photochemical efficiency, and stable isotopes. R. monosperma showed significantly higher shoot elongation, relative water content, and photochemical efficiency in summer compared with the other species. Stable isotope data confirmed its nitrogen-fixing capacity. This characteristic, along with the higher seasonal plasticity, contributes to its competitive advantage. Given the ecological fragility of coastal dunes, understanding the functional traits favouring the success of neonatives such as R. monosperma is essential for biodiversity conservation and ecosystem management. Full article
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21 pages, 4796 KiB  
Article
Hydrogeochemical Characteristics, Formation Mechanisms, and Groundwater Evaluation in the Central Dawen River Basin, Northern China
by Caiping Hu, Kangning Peng, Henghua Zhu, Sen Li, Peng Qin, Yanzhen Hu and Nan Wang
Water 2025, 17(15), 2238; https://doi.org/10.3390/w17152238 - 27 Jul 2025
Viewed by 335
Abstract
Rapid socio-economic development and the impact of human activities have exerted tremendous pressure on the groundwater system of the Dawen River Basin (DRB), the largest tributary in the middle and lower reaches of the Yellow River. Hydrochemical studies on the DRB have largely [...] Read more.
Rapid socio-economic development and the impact of human activities have exerted tremendous pressure on the groundwater system of the Dawen River Basin (DRB), the largest tributary in the middle and lower reaches of the Yellow River. Hydrochemical studies on the DRB have largely centered on the upstream Muwen River catchment and downstream Dongping Lake, with some focusing solely on karst groundwater. Basin-wide evaluations suggest good overall groundwater quality, but moderate to severe contamination is confined to the lower Dongping Lake area. The hydrogeologically complex mid-reach, where the Muwen and Chaiwen rivers merge, warrants specific focus. This region, adjacent to populous areas and industrial/agricultural zones, features diverse aquifer systems, necessitating a thorough analysis of its hydrochemistry and origins. This study presents an integrated hydrochemical, isotopic investigation and EWQI evaluation of groundwater quality and formation mechanisms within the multiple groundwater types of the central DRB. Central DRB groundwater has a pH of 7.5–8.2 (avg. 7.8) and TDSs at 450–2420 mg/L (avg. 1075.4 mg/L) and is mainly brackish, with Ca2+ as the primary cation (68.3% of total cations) and SO42− (33.6%) and NO3 (28.4%) as key anions. The Piper diagram reveals complex hydrochemical types, primarily HCO3·SO4-Ca and SO4·Cl-Ca. Isotopic analysis (δ2H, δ18O) confirms atmospheric precipitation as the principal recharge source, with pore water showing evaporative enrichment due to shallow depths. The Gibbs diagram and ion ratios demonstrate that hydrochemistry is primarily controlled by silicate and carbonate weathering (especially calcite dissolution), active cation exchange, and anthropogenic influences. EWQI assessment (avg. 156.2) indicates generally “good” overall quality but significant spatial variability. Pore water exhibits the highest exceedance rates (50% > Class III), driven by nitrate pollution from intensive vegetable cultivation in eastern areas (Xiyangzhuang–Liangzhuang) and sulfate contamination from gypsum mining (Guojialou–Nanxiyao). Karst water (26.7% > Class III) shows localized pollution belts (Huafeng–Dongzhuang) linked to coal mining and industrial discharges. Compared to basin-wide studies suggesting good quality in mid-upper reaches, this intensive mid-reach sampling identifies critical localized pollution zones within an overall low-EWQI background. The findings highlight the necessity for aquifer-specific and land-use-targeted groundwater protection strategies in this hydrogeologically complex region. Full article
(This article belongs to the Section Hydrogeology)
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17 pages, 4524 KiB  
Article
Growth and Water-Use Efficiency of European Beech and Turkey Oak at Low-Elevation Site
by Negar Rezaie, Ettore D’Andrea, Marco Ciolfi, Enrico Brugnoli and Silvia Portarena
Forests 2025, 16(8), 1210; https://doi.org/10.3390/f16081210 - 23 Jul 2025
Viewed by 759
Abstract
In Italy, beech and Turkey oak are among the most widespread tree species, thriving across various climatic zones. However, rising temperatures and prolonged droughts significantly affect their physiological performance and growth dynamics. To assess their long-term responses to climate change, mature beech and [...] Read more.
In Italy, beech and Turkey oak are among the most widespread tree species, thriving across various climatic zones. However, rising temperatures and prolonged droughts significantly affect their physiological performance and growth dynamics. To assess their long-term responses to climate change, mature beech and Turkey oak trees were studied in Central Italy at an elevation of 450 m. Using dendrochronological and stable isotope analyses (1981–2020), their growth patterns and physiological adaptations were evaluated. Beech exhibited a higher growth rate, with a basal area increment (BAI) of 17.1 ± 1.1 cm2 year−1, compared to Turkey oak, showing a BAI of 12.7 ± 0.96 cm2 year−1. Both species actively responded to increasing atmospheric CO2 levels. Additionally, spring and the previous summer’s climatic conditions played a key role in growth, while summer temperature and precipitation influenced carbon discrimination. For beech, correlations between BAI and iWUE (intrinsic water efficiency, defined as the ratio between photosynthesis and stomatal conductance) were initially weak and not statistically significant. However, the correlation became significant, strengthening steadily into the early 2000s, likely related to thinning of the beech trees. For Turkey oak, the correlation was already significant and strong from the beginning of the analysis period (1981), persisting until the late 1990s. Our findings suggest that both species actively adjust their iWUE in response to an increasing atmospheric CO2 concentration. However, while Turkey oak’s iWUE and BAI relationship remains unaffected by the likely thinning, beech benefits from reduced competition for light, nutrients, and water. Despite climate change’s impact on marginal populations, microclimatic conditions allow beech to outperform Turkey oak, a species typically better suited to drier climates. Full article
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17 pages, 2126 KiB  
Article
Stable Carbon and Nitrogen Isotope Signatures in Three Pondweed Species—A Case Study of Rivers and Lakes in Northern Poland
by Zofia Wrosz, Krzysztof Banaś, Marek Merdalski and Eugeniusz Pronin
Plants 2025, 14(15), 2261; https://doi.org/10.3390/plants14152261 - 22 Jul 2025
Viewed by 200
Abstract
Aquatic plants, as sedentary lifestyle organisms that accumulate chemical substances from their surroundings, can serve as valuable indicators of long-term anthropogenic pressure. In Poland, water monitoring is limited both spatially and temporally, which hampers a comprehensive assessment of water quality. Since the implementation [...] Read more.
Aquatic plants, as sedentary lifestyle organisms that accumulate chemical substances from their surroundings, can serve as valuable indicators of long-term anthropogenic pressure. In Poland, water monitoring is limited both spatially and temporally, which hampers a comprehensive assessment of water quality. Since the implementation of the Water Framework Directive (WFD), biotic elements, including macrophytes, have played an increasingly important role in water monitoring. Moreover, running waters, due to their dynamic nature, are susceptible to episodic pollution inputs that may be difficult to detect during isolated, point-in-time sampling campaigns. The analysis of stable carbon (δ13C) and nitrogen (δ15N) isotope signatures in macrophytes enables the identification of elemental sources, including potential pollutants. Research conducted between 2008 and 2011 encompassed 38 sites along 15 rivers and 108 sites across 21 lakes in northern Poland. This study focused on the isotope signatures of three pondweed species: Stuckenia pectinata, Potamogeton perfoliatus, and Potamogeton crispus. The results revealed statistically significant differences in the δ13C and δ15N values of plant organic matter between river and lake environments. Higher δ15N values were observed in rivers, whereas higher δ13C values were recorded in lakes. Spearman correlation analysis showed a negative relationship between δ13C and δ15N, as well as correlations between δ15N and the concentrations of Ca2+ and HCO3. A positive correlation was also found between δ13C and dissolved oxygen levels. These findings confirm the utility of δ13C and, in particular, δ15N as indicators of anthropogenic eutrophication, including potentially domestic sewage input and its impact on aquatic ecosystems. Full article
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21 pages, 2742 KiB  
Article
Origin Traceability of Chinese Mitten Crab (Eriocheir sinensis) Using Multi-Stable Isotopes and Explainable Machine Learning
by Danhe Wang, Chunxia Yao, Yangyang Lu, Di Huang, Yameng Li, Xugan Wu, Weiguo Song and Qinxiong Rao
Foods 2025, 14(14), 2458; https://doi.org/10.3390/foods14142458 - 13 Jul 2025
Viewed by 347
Abstract
The Chinese mitten crab (Eriocheir sinensis) industry is currently facing the challenges of origin fraud, as well as a lack of precision and interpretability of existing traceability methods. Here, we propose a high-precision origin traceability method based on a combination of [...] Read more.
The Chinese mitten crab (Eriocheir sinensis) industry is currently facing the challenges of origin fraud, as well as a lack of precision and interpretability of existing traceability methods. Here, we propose a high-precision origin traceability method based on a combination of stable isotope analysis and interpretable machine learning. We sampled Chinese mitten crabs from six origins representing diverse aquatic environments and farming practices, and analyzed their δ13C, δ15N, δ2H, and δ18O stable isotope compositions in different sexes and tissues (hepatopancreas, muscle, and gonad). By comparing the classification performance of Random Forest, XGBoost, and Logistic Regression models, we found that the Random Forest model outperformed the others, achieving high accuracy (91.3%) in distinguishing samples from different origins. Interpretation of the optimal Random Forest model, using SHAP (SHapley Additive exPlanations) analysis, identified δ2H in male muscle, δ15N in female hepatopancreas, and δ13C in female hepatopancreas as the most influential features for discriminating geographic origin. This analysis highlighted the crucial role of environmental factors, such as water source, diet, and trophic level, in origin discrimination and demonstrated that isotopic characteristics of different tissues provide unique discriminatory information. This study offers a novel paradigm for stable isotope traceability based on explainable machine learning, significantly enhancing the identification capability and reliability of Chinese mitten crab origin traceability, and holds significant implications for food safety assurance. Full article
(This article belongs to the Section Food Analytical Methods)
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24 pages, 17095 KiB  
Article
Origin of Dolomite in the Majiagou Formation (Ordovician) of the Liujiang Basin, China: Evidence from Crystal Structure, Isotope and Element Geochemistry
by Huaiyu Xue, Jianping Qian and Wentan Xu
Minerals 2025, 15(7), 717; https://doi.org/10.3390/min15070717 - 8 Jul 2025
Viewed by 320
Abstract
Research on dolomite has long been central in geoscience, yet understanding the origin of Middle Ordovician dolomite in the northeast of the North China Platform remains limited. Based on this, this study focuses on dolomite of Majiagou Formation in Liujiang Basin, and analyzes [...] Read more.
Research on dolomite has long been central in geoscience, yet understanding the origin of Middle Ordovician dolomite in the northeast of the North China Platform remains limited. Based on this, this study focuses on dolomite of Majiagou Formation in Liujiang Basin, and analyzes its genetic process. The research is based on the measured geological section and conducts high-precision analysis and testing, encompassing major and trace elements, rare earth elements, stable carbon and oxygen isotopes, strontium isotopes, crystal structure parameters, and micro-area elements of dolomite. Analysis of V/(V + Ni), Th/U, Sr/Ba, Mn/Sr, (Eu/Eu*) N, (Ce/Ce*) N, and the dolomite crystal parameters indicates that the formation of dolomite is related to evaporation. Furthermore, REE and micro-area characteristics of dolomite, as well as the significant negative deviation of δ13C and δ18O, in conjunction with 87Sr/86Sr deviating from the standard values of Ordovician seawater, suggest an origin of the dolomite in this formation with mixed-water dolomitization and burial dolomitization. A comprehensive assessment of dolomite formation suggests three distinct stages: early-stage evaporation dolomitization, subsequent mixed-water dolomitization, and later-stage burial dolomitization. The research further corroborated that dolomite formation is a complex outcome resulting from the interplay of various geological processes over space and time. Full article
(This article belongs to the Section Mineral Geochemistry and Geochronology)
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16 pages, 1176 KiB  
Article
Vertebrate Skeletal Remains as Paleohydrologic Proxies: Complex Hydrologic Setting in the Upper Cretaceous Kaiparowits Formation
by Daigo Yamamura and Celina Suarez
Geosciences 2025, 15(7), 262; https://doi.org/10.3390/geosciences15070262 - 8 Jul 2025
Viewed by 780
Abstract
The Kaiparowits Formation preserves one of the best fossil records of Cretaceous North America, which provides great insight into the paleoecology. In an effort to investigate the paleohydrology of the Kaiparowits Formation, stable isotope compositions (δ13C, δ18O-carbonate, δ18 [...] Read more.
The Kaiparowits Formation preserves one of the best fossil records of Cretaceous North America, which provides great insight into the paleoecology. In an effort to investigate the paleohydrology of the Kaiparowits Formation, stable isotope compositions (δ13C, δ18O-carbonate, δ18O-phosphate) of 41 hadrosaur teeth, 27 crocodile teeth, and 35 turtle shell fragments were analyzed. The mean O-isotope compositions of drinking water (δ18Ow) calculated from the O-isotope of bioapatite (phosphate-δ18Op) are −13.76 ± 2.08‰ (SMOW) for hadrosaur, −8.88 ± 2.76‰ (SMOW) for crocodile, and −10.14 ± 2.62‰ (SMOW) for turtle, which strongly reflect niche partitioning. The Kaiparowits formation does not fit the global trend in isotopic compositions of vertebrate skeletal remains from previous studies, which suggests a unique hydrological setting of the Kaiparowits basin. High-elevation runoff from the Mogollon Highlands and sea level fluctuation may have contributed to such a unique paleohydrology. Full article
(This article belongs to the Section Sedimentology, Stratigraphy and Palaeontology)
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16 pages, 1636 KiB  
Article
Lithological Controls on Chemical Weathering and CO2 Consumption at Small Watershed Scale: Insights from Hydrochemistry and Stable Carbon Isotope
by Yuanzheng Zhang, Wenlong Huang, Zhuohan Zhuang, Jing Hua, Litong Bai, Yi Ding, Ling Zheng, Cheng Wang, Chuang Zhao and Yunde Liu
Water 2025, 17(13), 2008; https://doi.org/10.3390/w17132008 - 4 Jul 2025
Viewed by 331
Abstract
Previous investigations into lithology-driven weathering processes have largely emphasized large-scale spatial assessments, while studies targeting small watershed scales remain scarce. This study investigated two adjacent watersheds (Chengjia: CJ; Datan: DT) under comparable climatic conditions in Guangdong, China, using hydrochemistry and stable carbon isotopes. [...] Read more.
Previous investigations into lithology-driven weathering processes have largely emphasized large-scale spatial assessments, while studies targeting small watershed scales remain scarce. This study investigated two adjacent watersheds (Chengjia: CJ; Datan: DT) under comparable climatic conditions in Guangdong, China, using hydrochemistry and stable carbon isotopes. The CJ watershed exhibited low-TDS (20–66 mg/L) HCO3-Na·Ca-type waters dominated by silicate weathering, whereas the DT watershed displayed high-TDS (70–278 mg/L) HCO3-Ca-type waters, indicative of mixed carbonate–silicate weathering. Results of carbon isotope composition of dissolved inorganic carbon confirmed that H2CO3-driven weathering was the dominant mechanism in both watersheds. In the CJ watershed, 79.5% of dissolved cations in surface water originated from silicate weathering, yielding a CO2 consumption rate (CCR) of 0.28 × 106 mol/km2/yr, while carbonate weathering was negligible. Conversely, in the DT watershed, 86.4% of dissolved cations were derived from carbonate weathering, yielding a CCR of 1.94 × 106 mol/km2/yr, whereas silicate weathering contributed only 10.3% of cations with a CCR of 0.23 × 106 mol/km2/yr. The chemical weathering rate of carbonate can be up to 10 times that of silicate, resulting in a larger CCR. This study demonstrated the key impact of lithology on hydrochemical characteristics and CO2 consumption at small watershed scales. Full article
(This article belongs to the Special Issue Water–Rock Interaction)
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32 pages, 7693 KiB  
Article
Genesis and Evolution of the Qieliekeqi Siderite Deposit in the West Kunlun Orogen: Constraints from Geochemistry, Zircon U–Pb Geochronology, and Carbon–Oxygen Isotopes
by Yue Song, Liang Li, Yuan Gao and Yang Luo
Minerals 2025, 15(7), 699; https://doi.org/10.3390/min15070699 - 30 Jun 2025
Viewed by 340
Abstract
The Qieliekeqi siderite deposit, located in the Tashkurgan block of western Kunlun, is a carbonate-hosted iron deposit with hydrothermal sedimentary features. This study integrates whole-rock geochemistry, stable isotopes, and zircon U–Pb–Hf data to investigate its metallogenic evolution. Coarse-grained siderite samples, formed in deeper [...] Read more.
The Qieliekeqi siderite deposit, located in the Tashkurgan block of western Kunlun, is a carbonate-hosted iron deposit with hydrothermal sedimentary features. This study integrates whole-rock geochemistry, stable isotopes, and zircon U–Pb–Hf data to investigate its metallogenic evolution. Coarse-grained siderite samples, formed in deeper water, exhibit average Al2O3/TiO2 ratios of 29.14, δEu of 2.69, and δCe of 0.83, indicating hydrothermal fluid dominance with limited seawater mixing. Banded samples from shallower settings show an average Al2O3/TiO2 of 17.07, δEu of 3.18, and δCe of 0.94, suggesting stronger seawater interaction under oxidizing conditions. Both types are enriched in Mn, Co, and Ba, with low Ti and Al contents. Stable isotope results (δ13CPDB = −6.0‰ to −4.6‰; δ18OSMOW = 16.0‰ to 16.9‰) point to seawater-dominated fluids with minor magmatic and meteoric contributions, formed under open-system conditions at avg. temperatures of 53 to 58 °C. Zircon U–Pb dating yields an age of 211.01 ± 0.82 Ma, with an average εHf(t) of −3.94, indicating derivation from the partially melted ancient crust. These results support a two-stage model involving Late Cambrian hydrothermal sedimentation and Late Triassic magmatic overprinting. Full article
(This article belongs to the Special Issue Selected Papers from the 7th National Youth Geological Congress)
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20 pages, 3264 KiB  
Article
The Crucial Role of Data Quality Control in Hydrochemical Studies: Reevaluating Groundwater Evolution in the Jiangsu Coastal Plain, China
by Claudio E. Moya, Konstantin W. Scheihing and Mauricio Taulis
Earth 2025, 6(3), 62; https://doi.org/10.3390/earth6030062 - 29 Jun 2025
Viewed by 308
Abstract
A vital step for any hydrochemical assessment is properly carrying out quality assurance and quality control (QA/QC) techniques to evaluate data confidence before performing the assessment. Understanding the processes governing groundwater evolution in coastal aquifers is critical for managing freshwater resources under increasing [...] Read more.
A vital step for any hydrochemical assessment is properly carrying out quality assurance and quality control (QA/QC) techniques to evaluate data confidence before performing the assessment. Understanding the processes governing groundwater evolution in coastal aquifers is critical for managing freshwater resources under increasing anthropogenic and climatic pressures. This study reassesses the hydrochemical and isotopic data from the Deep Confined Aquifer System (DCAS) in the Jiangsu Coastal Plain, China, by firstly applying QA/QC protocols. Anomalously high Fe and Mn concentrations in several samples were identified and excluded, yielding a refined dataset that enabled a more accurate interpretation of hydrogeochemical processes. Using hierarchical cluster analysis (HCA), principal component analysis (PCA), and stable and radioactive isotope data (δ2H, δ18O, 3H, and 14C), we identify three dominant drivers of groundwater evolution: water–rock interaction, evaporation, and seawater intrusion. In contrast to earlier interpretations, we present clear evidence of active seawater intrusion into the DCAS, supported by salinity patterns, isotopic signatures, and local hydrodynamics. Furthermore, inconsistencies between tritium- and radiocarbon-derived residence times—modern recharge indicated by 3H versus Pleistocene ages from 14C—highlight the unreliability of previous paleoclimatic reconstructions based on unvalidated datasets. These findings underscore the crucial role of robust QA/QC and integrated tracer analysis in groundwater studies. Full article
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20 pages, 30581 KiB  
Article
Hydrochemical Characteristics, Controlling Factors, and High Nitrate Hazards of Shallow Groundwater in an Urban Area of Southwestern China
by Chang Yang, Si Chen, Jianhui Dong, Yunhui Zhang, Yangshuang Wang, Wulue Kang, Xingjun Zhang, Yuanyi Liang, Dunkai Fu, Yuting Yan and Shiming Yang
Toxics 2025, 13(6), 516; https://doi.org/10.3390/toxics13060516 - 19 Jun 2025
Viewed by 363
Abstract
Groundwater nitrate (NO3) contamination has emerged as a critical global environmental issue, posing serious human health risks. This study systematically investigated the hydrochemical processes, sources of NO3 pollution, the impact of land use on NO3 pollution, [...] Read more.
Groundwater nitrate (NO3) contamination has emerged as a critical global environmental issue, posing serious human health risks. This study systematically investigated the hydrochemical processes, sources of NO3 pollution, the impact of land use on NO3 pollution, and drinking water safety in an urban area of southwestern China. Thirty-one groundwater samples were collected and analyzed for major hydrochemical parameters and dual isotopic composition of NO315N-NO3 and δ18O-NO3). The groundwater samples were characterized by neutral to slightly alkaline nature, and were dominated by the Ca-HCO3 type. Hydrochemical analysis revealed that water–rock interactions, including carbonate dissolution, silicate weathering, and cation exchange, were the primary natural processes controlling hydrochemistry. Additionally, anthropogenic influences have significantly altered NO3 concentration. A total of 19.35% of the samples exceeded the Chinese guideline limit of 20 mg/L for NO3. Isotopic evidence suggested that primary sources of NO3 in groundwater include NH4+-based fertilizer, soil organic nitrogen, sewage, and manure. Spatial distribution maps indicated that the spatial distribution of NO3 concentration correlated strongly with land use types. Elevated NO3 levels were observed in areas dominated by agriculture and artificial surfaces, while lower concentrations were associated with grass-covered ridge areas. The unabsorbed NH4+ from nitrogen fertilizer entered groundwater along with precipitation and irrigation water infiltration. The direct discharge of domestic sewage and improper disposal of livestock manure contributed substantially to NO3 pollution. The nitrogen fixation capacity of the grassland ecosystem led to a relatively low NO3 concentration in the ridge region. Despite elevated NO3 and F concentrations, the entropy weighted water quality index (EWQI) indicated that all groundwater samples were suitable for drinking. This study provides valuable insights into NO3 source identification and hydrochemical processes across varying land-use types. Full article
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22 pages, 7146 KiB  
Article
Groundwater Recharge Assessment and Recharge Zonation of the Intermontane Groundwater Basin, Chiang Mai, Thailand, Using a Groundwater Flow Model and Stable Isotopes
by Muhammad Zakir Afridi, Nipada Santha, Sutthipong Taweelarp, Nattapol Ploymaklam, Morrakot Khebchareon, Muhammad Shoaib Qamar and Schradh Saenton
Sustainability 2025, 17(12), 5560; https://doi.org/10.3390/su17125560 - 17 Jun 2025
Viewed by 1754
Abstract
Urbanization, escalating agriculture, tourism, and industrial development in the Chiang Mai–Lamphun groundwater basin in northern Thailand have increased water demand, causing widespread groundwater extraction. Over the past few decades, there has been a rapid, unrecoverable steady drop in groundwater levels in several areas [...] Read more.
Urbanization, escalating agriculture, tourism, and industrial development in the Chiang Mai–Lamphun groundwater basin in northern Thailand have increased water demand, causing widespread groundwater extraction. Over the past few decades, there has been a rapid, unrecoverable steady drop in groundwater levels in several areas in Chiang Mai and Lamphun provinces. This study employed hydrogeological investigations, hydrometeorological data analyses, stable isotopic analysis (δ18O and δ2H), and groundwater flow modeling using a 3D groundwater flow model (MODFLOW) to quantify groundwater recharge and delineate important groundwater recharge zones within the basin. The results showed that floodplain deposits exhibited the highest recharge rate, 104.4 mm/y, due to their proximity to rivers and high infiltration capacity. In contrast, younger terrain deposits, covering the largest area of 1314 km2, contributed the most to total recharge volume with an average recharge rate of 99.8 mm/y. Seven significant recharge zones within the basin, where annual recharge rates exceeded 105 mm/y (average recharge of the entire basin), were also delineated. Zone 4, covering parts of densely populated Muaeng Lamphun, Ban Thi, and Saraphi districts, had the largest area of 330 km2 and a recharge rate of 130.2 mm/y. Zone 6, encompassing Wiang Nong Long, Bai Hong, and Pa Sang districts, exhibited the highest recharge rate of 134.6 mm/y but covered a smaller area of 67 km2. Stable isotopic data verified that recent precipitation predominantly recharged shallow groundwater, with minimal evaporation or isotopic exchange. The basin-wide average recharge rate was 104 mm/y, reflecting the combined influence of geology, permeability, and spatial distribution. These findings provide critical insights for sustainable groundwater management in the region, particularly in the context of climate change and increasing water demand. Full article
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18 pages, 4318 KiB  
Article
The Genesis and Hydrochemical Formation Mechanism of Karst Springs in the Central Region of Shandong Province, China
by Yuanqing Liu, Le Zhou, Xuejun Ma, Dongguang Wen, Wei Li and Zheming Shi
Water 2025, 17(12), 1805; https://doi.org/10.3390/w17121805 - 17 Jun 2025
Viewed by 346
Abstract
With the intensification of human activities, the water resource environment in the karst mountainous area of central Shandong has undergone significant changes, directly manifested in the cessation of karst spring flows and the occurrence of karst collapses within the spring basin in the [...] Read more.
With the intensification of human activities, the water resource environment in the karst mountainous area of central Shandong has undergone significant changes, directly manifested in the cessation of karst spring flows and the occurrence of karst collapses within the spring basin in the Laiwu Basin. To support the scientific development and management of karst water, this study utilizes comprehensive analysis and deuterium-oxygen isotope test data from surveys and sampling of 20 typical karst springs conducted between 2016 and 2018. By integrating mathematical statistics, correlation analysis, and ion component ratio methods, the study analyzes the genesis, hydrochemical ion component sources, and controlling factors of typical karst springs in the Laiwu Basin. The results indicate that the genesis of karst springs in the Laiwu Basin is controlled by three factors: faults, rock masses, and lithology, and can be classified into four types: water resistance controlled by lithology, by faults, by basement, and by rock mass. The karst springs are generally weakly alkaline freshwater, with the main ion components being HCO3 and Ca2+, accounting for approximately 55.02% and 71.52% of the anion and cation components, respectively; about 50% of the sampling points have a hydrochemical type of HCO3·SO4-Ca·Mg. Stable isotope (δ18O and δD) results show that atmospheric precipitation is the primary recharge source for karst springs in the Laiwu Basin. There are varying degrees of evaporative fractionation and water–rock interaction during the groundwater flow process, resulting in significantly higher deuterium excess (d-excess) in the sampling points on the southern side of the basin compared to the northern side, indicating clear differentiation. The hydrochemical composition of the karst groundwater system is predominantly governed by water–rock interactions during flow processes and anthropogenic influences. Carbonate dissolution (primarily calcite) serves as the principal source of HCO3, SO42−, Ca2+, and Mg2+, while evaporite dissolution and reverse cation exchange contribute to the slight enrichment of Ca2+ and Mg2+ alongside depletion of Na+ and K+ in spring waters. Saturation indices (SI) reveal that spring waters are saturated with respect to gypsum, aragonite, calcite, and dolomite, but undersaturated for halite. The mixing of urban domestic sewage, agricultural planting activities, and the use of manure also contributes to the formation of Cl and NO3 ions in karst springs. Full article
(This article belongs to the Topic Human Impact on Groundwater Environment, 2nd Edition)
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25 pages, 10720 KiB  
Article
Responses of Water Use Strategies to Seasonal Drought Stress Differed Among Eucalyptus urophylla S.T.Blake × E. grandis Plantations Along with Stand Ages
by Zhichao Wang, Yuxing Xu, Wankuan Zhu, Runxia Huang, Apeng Du, Haoyang Cao and Wenhua Xiang
Forests 2025, 16(6), 962; https://doi.org/10.3390/f16060962 - 6 Jun 2025
Viewed by 390
Abstract
Water use strategies reflect the ability of plants to adapt to drought caused by climate change. However, how these strategies change with stand development and seasonal drought is not fully understood. This study used stable isotope techniques (δD, δ18O, and δ [...] Read more.
Water use strategies reflect the ability of plants to adapt to drought caused by climate change. However, how these strategies change with stand development and seasonal drought is not fully understood. This study used stable isotope techniques (δD, δ18O, and δ13C) combined with the MixSIAR model to quantify the seasonal changes in water use sources and water use efficiency (WUE) of Eucalyptus urophylla S.T.Blake × E. grandis (E. urophylla × E. grandis) at four stand ages (2-, 4-, 9- and 14-year-old) and to identify their influencing factors. Our results showed that the young (2-year-old) and middle-aged (4-year-old) stands primarily relied on shallow soil water throughout the growing season due to the limitations of a shallow root system. In contrast, the mature (9-year-old) and overmature (14-year-old) stands, influenced by the synergistic effects of larger and deeper root systems and relative extractable water (REW), exhibited more flexibility in water use, mainly relying on shallow soil water in wet months, but shifting to using middle and deep soil layer water in dry months, and quickly returning to mainly using shallow soil water in the episodic wet month of the dry season. The WUE of E. urophylla × E. grandis was affected by the combined effect of air temperature (T), vapor pressure deficit (VPD), and REW. WUE was consistent across the stand ages in the wet season but decreased significantly with stand age in the dry season. This suggests that mature and overmature stands depend more on shifting their water source, while young and middle-aged stands rely more on enhanced WUE to cope with seasonal drought stress, resulting in young and middle-aged stands being more vulnerable to drought stress. These findings offer valuable insights for managing water resources in eucalyptus plantations, particularly as drought frequency and intensity continue to rise. Full article
(This article belongs to the Special Issue Advances in Forest Carbon, Water Use and Growth Under Climate Change)
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