Search Results (1,907)

The comprehensive analysis of stable carbon isotopes in dissolved organic carbon (δ¹³C-DOC) and dissolved inorganic carbon (δ¹³C-DIC) is essential for understanding carbon cycling in groundwater systems. This study evaluated the performance, stability, and accuracy of a Total Organic Carbon analyzer coupled with Cavity Ring-Down Spectroscopy (TOC-CRDS) for the determination of δ¹³C-DOC and δ¹³C-DIC. Long-term stability tests using solid standards (acetanilide) demonstrated an average precision of 0.21‰ over five days, though initial instrument stabilization was found to be critical. Systematic sensitivity experiments revealed a strong dependence of isotopic accuracy on carbon mass. For liquid samples, a minimum carbon threshold of 50 μg C (equivalent to 6.25 mg/L DOC in an 8 mL injection) was established; above this threshold, analytical precision consistently remained better than 0.3‰. Validation using synthetic samples showed excellent agreement between measured and calculated values for both DOC and DIC. Furthermore, comparative analysis of natural groundwater samples revealed that TOC-CRDS results were highly consistent with those obtained by GasBench–Isotope Ratio Mass Spectrometry, with relative deviations within 5% for DOC and 6% for DIC. The study confirms that TOC-CRDS provides a robust, high-precision (<0.3‰), and cost-effective alternative to mass spectrometry for analyzing groundwater carbon isotopes, provided that sample carbon content exceeds the determined thresholds and appropriate calibration strategies are employed. Full article

The northern Vietnam shelf, particularly the area adjacent to the Red River Fault Zone, is characterized by complex geology and active neotectonics. However, the patterns of degassing and the origins of hydrocarbon gases in this region remain poorly understood. In particular, the potential links between deep-seated fluid migration, fault systems, and gas anomalies in island groundwater systems have not been systematically investigated. This study presents preliminary results of dissolved methane, its homologues (C₂–C₅), helium, hydrogen, and carbon dioxide measurements in groundwater from Co To Island (Northern Vietnam), with the aim of identifying gas origins and assessing structural controls on fluid migration. A significant methane anomaly was discovered, with concentrations reaching up to 10% by volume in the northwestern part of the island. The hydrocarbon homologous series is traced up to pentane (C₅), and CO₂ content is also elevated, with a maximum of 5.4%. The average He concentration of 10.8 ppm significantly exceeds atmospheric equilibrium values, with maximum recorded concentrations of 18 ppm for He and 34.5 ppm for H₂. Stable carbon isotope analysis of methane (δ¹³C-CH₄ values ranging from −50.2‰ to −49.7‰ VPDB), combined with the presence of a complete C₁–C₅ hydrocarbon series and elevated mantle/crustal tracers (He, H₂), indicates a predominantly thermogenic/metamorphogenic origin for the gases, ruling out a purely biogenic source. The spatial distribution of anomalies is structurally controlled, closely associated with the NE-SW trending Co To Fault system and its intersections with subsidiary faults, as corroborated by recent electrical resistivity tomography data. These findings indicate intensive, focused gas leakage from a deep-seated source, likely related to thermogenic/metamorphic processes and active fault-mediated degassing. The results highlight the significant hydrocarbon potential of the region and underscore the critical role of neotectonic activity in controlling fluid migration pathways in island aquifer systems. Full article

Total body water (TBW) undergoes substantial physiological expansion during pregnancy, reflecting coordinated cardiovascular, renal, and endocrine adaptations required to support maternal metabolism, uteroplacental perfusion, and fetal growth. These changes involve not only an overall increase in body water but also shifts in the distribution of extracellular water (ECW) and intracellular water (ICW), which influence maternal body composition, the interpretation of biochemical biomarkers affected by hemodilution, and pregnancy-related clinical outcomes. Despite its physiological and clinical relevance, the regulation and assessment of body-water compartments during pregnancy remain insufficiently integrated within nutritional and clinical research. This narrative review synthesizes current knowledge on the physiological regulation of TBW and its compartments across gestation and provides a critical analysis of the methodological approaches used to assess body-water distribution in pregnant populations. We review the mechanisms underlying plasma volume expansion, interstitial fluid accumulation, and tissue hydration, and discuss their implications for fetal growth, hypertensive disorders of pregnancy, and gestational diabetes mellitus. We also examine the principles, strengths, and limitations of the main techniques used to assess TBW and body-water compartments during pregnancy. Isotope dilution using stable isotopes (²H₂O and H₂¹⁸O) remains the reference method for TBW assessment, whereas bioelectrical impedance-based approaches, including bioelectrical impedance analysis (BIA), bioelectrical impedance spectroscopy (BIS), and bioelectrical impedance vector analysis (BIVA), offer practical alternatives for longitudinal monitoring of fluid redistribution during gestation. By integrating physiological and methodological perspectives, this review provides a framework for understanding body-water dynamics during pregnancy and for selecting appropriate approaches to assess maternal body composition and hydration. Full article

The development of sustainable and environmentally benign N-methylation methodologies is essential for enhancing sustainable synthetic practice in pharmaceutical manufacturing. In this study, we demonstrate that microwave heating (MWH) markedly enhanced the efficiency of cobalt-catalyzed N-methylation using methanol or methanol-d₄ as green C1 sources. Compared with conventional heating (CH), MWH enabled highly efficient syntheses of key pharmaceutical intermediates—including 6-dimethylamino-1-hexanol, imipramine hydrochloride, and butenafine hydrochloride—under milder conditions and shorter reaction times and without generating hazardous halogen-containing waste. UV–vis spectroscopic analysis revealed that MWH accelerated the transformation of Co(acac)₂ into catalytically active Co species by approximately four-fold, providing a mechanistic basis for the enhanced reactivity. We hypothesized that this effect was caused by the selective microwave heating of the catalyst, which in turn promoted the rapid generation of catalytically active species. Notably, MWH also significantly improved the N-trideuteromethylation of amines using methanol-d₄, achieving a 95% yield for imipramine-d₃ hydrochloride versus 32% under CH. Molecular dynamics simulations indicated that methanol-d₄ exhibited slower dipole relaxation and enhanced cluster fragmentation under microwave fields, improving catalyst–substrate contact, while kinetic isotope effects stabilized reactive intermediates. These synergistic effects account for the pronounced microwave promotion observed in deuterated systems. Overall, the combination of MWH and cobalt catalysis offers an energy-efficient, waste-minimizing, and environmentally benign strategy for the scalable synthesis of both methylated and deuterated amines. Full article

Monitoring of stable isotopes in throughfall (δ¹⁸O, δ²H) and meteorological parameters is a valuable tool for researching forest hydrology, particularly during extreme events like droughts and floods. This study presents the first systematic analysis of air temperature and precipitation changes over the past 65 years in two Slovenian lowland forests: Murska šuma and Krakovski gozd, in combination with isotopic composition research of throughfall. The observed rising air temperatures and altered precipitation patterns are reflected in the isotopic composition of throughfall. Over the last 65 years, air temperature has increased by approximately 2.5 °C. Although total annual precipitation amounts have remained relatively stable, in the last 35 years there is a notable decrease in precipitation in growing season and an increase during the dormant season, influenced by air masses of Mediterranean origin. Extreme drought in 2022 and flood in 2023 are confirmed by the Standardized Precipitation Index and isotopic variations in throughfall due to fractionation processes. Annual variability appears as seasonal changes, with sine-curve amplitudes of 3.71‰ in Krakovski gozd and 3.61‰ in Murska šuma. Together with the Local Meteoric Water Lines, these patterns support estimates of groundwater mean residence time and the origin of water used by trees. Full article

Background: Accurate axillary staging is vital in breast cancer. While dual tracers (Tc-99m + methylene blue dye) are standard for sentinel lymph node biopsy (SLNB), indocyanine green (ICG) offers a cost-effective, safe alternative, especially where nuclear medicine access is limited. Despite growing global use, data from low- and middle-income countries (LMICs) remain scarce. This study presents India’s largest cohort using ICG in SLNB. Methods: We analyzed data from 678 breast cancer patients (2013–2023), of whom 609 underwent SLNB. For analysis, patients were grouped into: isotope + blue dye (control), ICG + blue dye (study group), and ICG alone. False-negative rate (FNR) was evaluated in cases where SLNB was followed by axillary lymph node dissection (ALND). All other outcomes were assessed across the SLNB cohort. Results: In upfront surgery, the study group had an identification rate (IR) of 95.6%, an FNR of 5%, and a median node yield of four, compared to the control group (IR 94.1%, FNR 0%, median of three). Post-neoadjuvant systemic therapy (NAST), the study group outperformed the control (IR 92% vs. 88.2%; both FNR 10%), with higher node yield (three vs. two). From 2021, ICG alone showed 100% IR, 0% FNR (upfront), and 95.6% IR (post-NACT), with high median node retrieval. Overall recurrence was 7.8%; loco-regional recurrence was 3.09%. Conclusions: ICG offers high efficacy, safety, and feasibility as a sole tracer, especially in LMICs. Its integration into SLNB and oncoplastic workflows supports its broader adoption as a practical alternative to radioisotopes in breast cancer surgery. Full article

Surface water–groundwater interactions within oasis–desert ecotones of arid regions play a pivotal role in sustaining regional water security and ecological stability. Taking the Niya River Basin in Xinjiang, Northwest China, as a representative inland watershed, this study systematically elucidates the mechanisms and seasonal dynamics of surface water–groundwater coupling under the combined influences of natural processes and anthropogenic activities. A total of 68 surface water and groundwater samples were collected during the dry, normal, and wet hydrological periods. Integrated hydrochemical characterization, mineral saturation index analysis, and stable isotope (δ²H and δ¹⁸O) mass balance modeling were employed to quantify recharge contributions and unravel hydrogeochemical evolution pathways. Results indicate that the waters in the study area are predominantly brackish to saline, with consistent dominant ionic assemblages (SO₄²⁻ and Na⁺) across all hydrological periods, highlighting evaporite dissolution as the primary control on solute composition. Hydrochemical evolution is jointly regulated by evaporation concentration, water–rock interactions, and cation exchange processes. Surface water chemistry reflects the combined effects of silicate weathering and evaporite dissolution, whereas groundwater chemistry is mainly governed by evaporite dissolution coupled with pronounced cation exchange. Stable isotope signatures reveal substantial secondary evaporation of regional precipitation prior to recharge. Frequent bidirectional recharge between surface water and groundwater was observed, exhibiting distinct seasonal transitions. During the dry period, groundwater provides significant baseflow support to surface water (48.6% in the oasis zone and 54.3% in the desert zone). In the normal period, recharge direction reverses, with surface water becoming the dominant source of groundwater recharge (99.0% in the oasis zone and 76.6% in the desert zone). In the wet period, spatial heterogeneity becomes evident: surface water continues to dominate groundwater recharge in the oasis zone (92.7%), whereas groundwater recharge to surface water prevails in the desert zone (50.5%). This study identifies a seasonally dynamic “discharge–infiltration–zonal regulation” bidirectional recharge pattern in arid inland river systems. The findings advance the mechanistic understanding of hydrological connectivity reconstruction within oasis–desert ecotones and provide a scientific basis for optimized regional water resource allocation and groundwater salinization risk mitigation. Full article

Accurately tracing the geographical origin of Zanthoxylum schinifolium Sieb. et Zucc. is important for brand authentication, quality control, and food safety assurance. In this study, the stable isotope ratios (δ¹³C, δ¹⁵N, δ²H, δ¹⁸O) and the contents of 20 elements were analyzed in samples from three major production regions. Significant differences (p < 0.05) were observed in δ¹³C, δ²H, δ¹⁸O and most elemental profiles across origins. Chemometric methods—including principal component analysis (PCA), orthogonal partial least squares-discriminant analysis (OPLS-DA), and linear discriminant analysis (LDA)—were applied to classify samples by geographical origin. OPLS-DA identified key discriminators (VIP > 1) such as Ca, δ¹³C, Mg, δ²H, B, δ¹⁸O, Cr, Ni, Na, Pb, As, Co, Se, and Zn, achieving a classification accuracy of 96.8%. LDA based on the combined isotope and element datasets showed even higher performance, with an original discrimination rate of 98.4% and a cross-validated rate of 92.8%. The results demonstrate that integrating stable isotope and multi-element fingerprints with supervised classification models provides a reliable and effective approach for verifying the geographical origin of Zanthoxylum schinifolium, supporting its use in traceability systems and fair trade practices. Full article

Kelp transplantation is a nature-based strategy aimed at restoring coastal habitat integrity and marine biodiversity. However, its functional consequences for trophic integration within benthic food webs remain poorly understood. Using δ¹³C and δ¹⁵N stable isotope analyses, we evaluated how Undaria pinnatifida transplantation alters consumer trophic structures and isotopic niche characteristics in Oeyeondo, South Korea. While basal source remained isotopically uniform across sites, the introduction of U. pinnatifida triggered significant isotopic shifts in consumers, reflecting a reorganization of carbon assimilation pathways. At the transplanted site, herbivores exhibited significantly enriched δ¹³C values (−14.7 ± 2.0‰ to −13.2 ± 0.3‰) compared to the control site (−19.3 ± 1.2‰), indicating direct assimilation of kelp-derived carbon. Conversely, grazers showed depleted δ¹³C values (−20.6 ± 0.6‰) reflecting a shift toward alternative benthic resources. Isotopic niche metrics revealed a broader community-level niche width at the transplanted site, driven by increased resource diversity and niche partitioning. These findings demonstrate that kelp transplantation effectively restructures benthic food web dynamics by providing new energy pathways, offering a robust functional framework for evaluating marine forest restoration success. Full article

The Aksu River Basin, the main headwater of the Tarim River, contributes more than 70% of the main stream’s runoff and is therefore critical in maintaining hydrological stability in this arid river system. In recent decades, rapid oasis expansion and growing agricultural water withdrawals have intensified competition for surface and groundwater, posing increasing ecological risks to the downstream Tarim River Basin. To quantitatively characterize river–groundwater hydrological responses under intensive water use, we combined statistical analysis, field observations, and distributed hydrological modeling within a basin-scale conceptual framework. Multiple lines of evidence—water level monitoring, hydrochemical tracers, stable isotopes, and the integrated surface–groundwater model MIKE SHE—were used to identify river–groundwater interaction mechanisms in the Aksu alluvial plain. Results reveal a typical three-stage spatial exchange pattern: river recharge to groundwater in the upstream reach, groundwater discharge to the river in the midstream, and renewed river infiltration to groundwater downstream. The patterns inferred from water levels, hydrochemistry, and isotopes are broadly consistent, while water-level data better resolve left–right bank asymmetry. The MIKE SHE model supports the seasonal bidirectional exchange dynamics and reproduces runoff behavior with acceptable performance (RMSE and residual standard deviation within 20% of observed means and R² > 0.7 during both calibration (2010–2017) and validation (2018–2021)). The proposed multi-evidence framework captures the spatio-temporal variability of river–groundwater interactions in arid regions and provides spatially differentiated guidance for conjunctive surface–groundwater regulation and integrated water resources management in the Tarim River Basin. Full article

Groundwater used for drinking in settlements located near decommissioned uranium mining facilities may contain elevated naturally occurring radioactive materials, posing long-term public-health concerns. The purpose of this study was to evaluate the radiological quality of groundwater used for drinking in the Saumalkol settlement by applying gross alpha–beta screening and isotope-specific analysis of ²²⁶Ra and ²²⁸Ra to identify the main contributors to groundwater radioactivity and estimate the associated radiation dose from water consumption. Groundwater samples were analyzed using gross alpha–beta screening and isotope-specific determination of ²²⁶Ra and ²²⁸Ra by radiochemical separation and low-background counting, and ingestion doses were estimated using international dose coefficients. Gross alpha activity averaged 2.26 ± 0.96 Bq/L, with most samples exceeding the WHO screening value of 0.5 Bq/L, while gross beta activity averaged 0.65 ± 0.17 Bq/L. Mean activity concentrations of ²²⁶Ra and ²²⁸Ra were 0.17 ± 0.03 Bq/L and 1.47 ± 0.9 Bq/L, respectively, with significantly higher ²²⁸Ra in deep boreholes and a systematic predominance of ²²⁸Ra over ²²⁶Ra (p < 0.05), indicating a thorium-controlled geochemical signature in fractured crystalline aquifers. The estimated annual committed effective ingestion dose from radium isotopes was 0.46 mSv, exceeding the reference level of 0.1 mSv for drinking-water exposure. These findings demonstrate that groundwater radioactivity in Saumalkol is dominated by radium from the thorium series and highlight the need for sustained radionuclide-specific monitoring and targeted water management strategies in uranium-affected regions. Full article

Late Early Jurassic continental arc magmatism in the northern Greater Khingan Range enables the investigation of complicated tectonic processes associated with the subduction and closure of the Mongol–Okhotsk Ocean. To further clarify the timing, genesis, and geodynamic mechanisms driving the magmatic activity during this period, the present study addresses these critical questions by integrating zircon U–Pb geochronological, geochemical, and isotopic analyses of a wide variety of igneous rocks, including gabbro, gabbro-diorite, granodiorite, porphyritic monzogranite, and biotite-bearing monzogranite from the Fushan region. Zircon U–Pb geochronology constrains the timing of magmatic activity to 184–179 Ma, coinciding with active subduction phases. Geochemical data reveal arc-like signatures characterized by enrichment in light rare-earth elements (LREEs) and large-ion lithophile elements (LILEs), together with pronounced depletion in high field strength elements (HFSEs). A comprehensive analysis of geochemical and Sr–Nd–Hf isotopic signatures suggests that the mafic rocks originated from an enriched lithospheric mantle modified by subduction-related fluids and sediment-derived melts. By contrast, the granodiorite and porphyritic monzonite exhibit adakitic characteristics, indicating partial melting of the thickened Mesoproterozoic lower crust with contributions from mantle-derived or newly formed crustal material. The biotite-bearing monzogranite, with its pronounced Eu anomaly and lower zircon saturation temperatures, reflects advanced magmatic differentiation from a shallower source. These findings indicate extensive crust–mantle interactions during the southward subduction of the Mongol–Okhotsk Ocean, driven by high-angle subduction and slab rollback. Full article

Groundwater is a critical resource in the arid Chili River sub-basin (3246 km²) in Arequipa, southern Peru, yet the aquifer systems, their recharge mechanisms, and chemical evolution remain poorly characterized. This study integrates hydrogeological mapping, major-ion hydrochemistry (31 samples from springs and wells), and stable-isotope tracing (δ¹⁸O and δ²H, 11 sources) to delineate aquifer types, groundwater flow systems, and recharge dynamics across an elevation gradient of 2000–4000 m a.s.l. Three principal aquifer groups were identified: unconsolidated porous aquifers beneath the Arequipa urban area, fracture-controlled volcanic aquifers associated with the Chachani, Misti, and Pichupichu volcanic complexes, and sedimentary fractured aquifers of the Yura Group. Piper and Stiff diagrams reveal a chemical evolution from calcium-bicarbonate waters at high elevations to sodium-chloride waters in the lowlands, while scatter-plot analysis distinguishes local, intermediate, and regional flow systems. Elevated boron concentrations linked to borate deposits on Pichupichu volcano pose a potential health risk in supply springs such as La Bedoya. Isotopic signatures confirm that wells are recharged predominantly by high-altitude rainfall (>4000 m a.s.l.), whereas springs integrate water from multiple elevations through fractured volcanic formations. These findings provide a scientific basis for recharge-zone protection, abstraction planning, and water-quality monitoring to sustain groundwater supply under increasing urbanization and climatic variability. Full article

Monofloral honeys are widely recognized for their distinct chemical characteristics which are largely influenced by botanical origin. This study aimed to compare the physicochemical and functional properties of monofloral honeys produced in South Korea. Five monofloral honey types, Castanea crenata, Robinia pseudoacacia, Toxicodendron spp., Hovenia dulcis, and Styrax japonicus, were analyzed, and their floral origins were confirmed through melissopalynological analysis. Physicochemical parameters (moisture content, total soluble solids, hydroxymethylfurfural content, stable carbon isotope ratio, free acidity, pH, color, and sugar composition), along with amino acid profiles, predicted glycemic index (GI), and antioxidant activity, were determined. Most physicochemical parameters showed statistically significant differences among honey types. Amino acid composition differed markedly among honey types, with Castanea honey exhibiting higher levels of proline, phenylalanine, and leucine compared to Robinia and Styrax honeys. Predicted GI values were predominantly within the low-GI range, with no statistically significant differences observed among floral origins. Antioxidant activity showed a similar trend to amino acid content, with Castanea honey displaying the highest antioxidant values. These findings demonstrate that botanical origin is a key determinant of the physicochemical and in vitro functional attributes of honey, including antioxidant activity and predicted GI, and provide a scientific basis for the characterization of South Korean monofloral honeys. Full article

This study examines the marble resources of the Mani peninsula, southern Greece, a region that has long been known for its white, gray-black (bigio antico), green (cipollino verde Tenario), and particularly red (rosso antico or lapis Taenarium) and dark (nero antico) marbles. Based on extensive fieldwork, more than 90 quarrying sites were documented, several of which were recorded for the first time. This study provides a systematic characterization of these stones through combined mineralogical, petrographic, and stable isotopic (δ¹⁸O, δ¹³C) analyses of 27 representative samples. The results confirm the presence of calcitic marbles, which vary in color due to hematite in the red varieties, graphite and organic matter in the gray-black and black types, and chlorite in the green marbles. The isotopic results demonstrate a generally high degree of homogeneity, although the red marbles display greater variability, complicating their distinction from analogous stones in Asia Minor, such as those from Iasos and Milas. Quarrying of Mani marbles began in the Bronze Age and reached its peak during Roman times. It continued into the Byzantine period, with renewed exploitation in the 19th and 20th centuries. This study highlights the significant role of Mani in the ancient marble trade and contributes to ongoing debates about the provenance of famous red, white, and black marbles across the Mediterranean. Furthermore, it establishes a strong reference framework, integrating new analytical results with the existing literature, providing an updated mineralogical, petrographic, and isotopic database for provenance studies of marble artifacts. Full article