Search Results (878)

Abandoned floodplains are complex landscapes in boreal permafrost regions due to diverse biogeomorphic effects that are highly modified by permafrost aggradation and degradation. We compiled biophysical properties for 150 cores at 135 sites with depths up to ~4 m on the Tanana Flats in central Alaska and developed depth profiles for bulk density, moisture, organic carbon, pH, stable isotopes, radiocarbon age, and thaw strain. We found strong associations among biophysical components but also highly variable soil properties and ecological histories. We developed a conceptual model of the transition pathways and biophysical drivers among ecosystem types. Across sites, fluvial deposition was active from 9820 to 4290 ¹⁴C YBP, eolian silt and sand deposition prevalent from 3780 to 1890 YBP, and peat accumulation from 5330 YBP to present. Due to flat topography, water impoundment in depressions, groundwater, and ecological feedbacks, ecosystem-driven permafrost has a complex history of repeated aggradation and degradation resulting in highly fragmented landscapes. Recent thermokarst features had ages ranging from 20 to 920 YBP in collapse-scar bogs and from 50 to 250 YBP in collapse-scar fens. Abandoned floodplains with rapid thermokarst provide saturated environments for robust organic accumulation, with mean soil carbon stocks in the top 3 m being similar among thermokarst bogs (133 kg/m²), fens (108 kg/m²) and permafrost plateaus (115 kg/m²). This study contributes needed information on how permafrost dynamics and ground-ice characteristics influence landscape evolution and on the vulnerability of villages built on abandoned floodplains, infrastructure, and military use of training lands in boreal lowlands. Landscape fragmentation, complex palaeoecological histories, high spatial variability, and limited deep sampling of thermokarst features, however, restrict interpretation of how permafrost loss is affecting the soil carbon balance in an area where most permafrost will disappear in this century. Full article

Anadromous and freshwater-resident Coilia nasus frequently share spawning grounds, yet exhibit distinct feeding habits during migration; therefore, we hypothesized that the isotopic profiles of mature eggs from these two ecotypes would differ. In the present study, a total of 102 C. nasus individuals were collected from a spawning ground in Poyang Lake, China; among them, 20 mature females with intact ovaries were selected for further analysis. Their migratory history was confirmed by otolith microchemistry, and carbon (δ¹³C) and nitrogen (δ¹⁵N) stable isotope ratios of mature eggs were analyzed. Otolith microchemical results showed that some of the 20 females exhibited three Sr/Ca stages (1.51 ± 0.46, 4.79 ± 1.00, and 2.09 ± 0.79), identifying them as anadromous, whereas the remaining females showed stable low Sr/Ca ratios (1.49 ± 0.45), indicating freshwater residency. Both δ¹³C and δ¹⁵N values of mature eggs from the anadromous individuals were significantly higher than those from the freshwater-resident individuals (p < 0.01, Mann–Whitney U test). And the results of linear discriminant analysis (LDA) showed no misclassification. These results demonstrated that δ¹³C and δ¹⁵N showed strong discriminatory performance for mature eggs from anadromous and freshwater-resident C. nasus within the present dataset. However, because all analyses were performed on mature eggs collected directly from ovaries, this method has not yet been tested on naturally spawned or fertilized eggs in the field. Therefore, future studies should first validate this method on field-collected fertilized eggs to determine its practical efficacy for locating spawning grounds. Full article

The Yinchuan Basin is situated at the leading edge of the latest northeastward expansion of the northeastern Tibetan Plateau. Sedimentary sequences at basin margins are crucial for understanding basin–mountain coupling relationships, yet systematic studies remain scarce. Here, we present a comprehensive sedimentological, paleomagnetic, whole-rock major and trace element, carbon–oxygen isotope, and detrital zircon U–Pb geochronological analysis of ZK01 Borehole (203 m) from the Kushui River area in the southern basin. Multi-proxy reconstruction reveals that Quaternary climate evolution can be divided into five stages: (1) Early Pleistocene (~2.58–1.77 Ma) alluvial fan-lacustrine alternations with high-amplitude climatic fluctuations, responding to orbitally-driven monsoon precipitation changes; (2) late Early Pleistocene (~1.77–0.78 Ma) stable lacustrine environment with sustained warm–humid conditions and subdued wet–dry oscillations; (3) Middle Pleistocene Climate Transition (MPT, ~0.9–0.6 Ma), marked by positive δ¹³C shifts, heavier δ¹⁸O values, and peak CIA values, indicating intensified chemical weathering in the catchment despite regional warming–drying; (4) Late Pleistocene (~0.16–0.12 Ma) extreme arid alluvial fan phase, with decreased CIA, recording a major dry event; and (5) post-last interglacial (~0.12 Ma–present) shallow lake recovery, with gradual enrichment of all proxies. Detrital zircon U–Pb age spectra show multi-peak characteristics (200–300 Ma, 400–500 Ma, etc.), consistent with upper Yellow River sediments. From the Late Pliocene to the Quaternary, the 200–300 Ma component increased while Precambrian components decreased. Provenance evolution indicates the Yellow River has been the primary sediment carrier, with increasing young components linked to the far-field effects of the Kunlun-Huanghe Movement, revealing tectonic uplift-driven headward erosion and provenance changes. We conclude that Quaternary environmental evolution of the Yinchuan Basin was jointly controlled by orbital-scale monsoon climate and episodic tectonic uplift of the northeastern Tibetan Plateau margin, with Yellow River integration further reshaping the basin’s drainage pattern. Full article

Mudstone caprocks are important sealing formations for geological CO₂ storage, but the extent and mineralogical response of CO₂-induced alteration within mudstone caprocks remain poorly constrained. This study examines a Paleocene mudstone caprock from the Mingyuefeng Formation in the Lishui Sag, East China Sea Basin, where natural CO₂ charging has occurred. Mineralogical and geochemical analyses, including X-ray diffraction (XRD), rare earth elements (REE), and carbon–oxygen isotopes, were used to characterize CO₂–water–rock interaction at the reservoir–caprock transition. The studied caprock is dominated by quartz and clay minerals, with mineralogical characteristics favorable for caprock sealing. REE signatures indicate a felsic source and limited vertical REE redistribution within the studied interval. Carbonate minerals display distinct vertical variations across the sandstone–mudstone interface, with localized carbonate redistribution near the transition and carbonate depletion accompanied by clay-mineral alteration above it. Most samples retain δ¹³C values close to background levels, whereas a decimeter-scale interval adjacent to the interface exhibits depleted δ¹³C values accompanied by localized δ¹⁸O variations, consistent with the localized influence of CO₂-bearing fluids. The altered zone is restricted to a decimeter-scale interval above the reservoir–caprock transition, suggesting that CO₂-related alteration was spatially restricted within the studied interval. Carbonate redistribution and clay-mineral transformation may have contributed to geochemical buffering during CO₂–water–rock interaction, although their quantitative effects on pore structure and sealing performance require further petrophysical investigation. These results provide a natural analogue for understanding localized CO₂-induced alteration and potential geochemical self-sealing processes at reservoir–caprock interfaces. Full article

The Ordovician strata in Northern Tarim host extensively developed carbonate karst reservoirs that contain abundant hydrocarbon resources. However, owing to extreme burial depths, pronounced heterogeneity, and limited seismic resolution within the Tarim Basin, the diagenetic fluid types and their specific influences on reservoir development remain poorly understood. Consequently, this study integrates core observation, thin-section identification (TSI), cathodoluminescence (CL), scanning electron microscopy (SEM), X-ray diffraction (XRD), stable isotopes (C, O, Sr), trace and rare earth elements (REE), fluid inclusion analysis (FIA), and in situ laser U-Pb dating (U-Pb). This multifaceted petrographic and geochemical approach characterizes the macro- and microscopic geological features of these karst reservoirs. By elucidating the types, timing, and phases of diagenetic fluids, this research evaluates fluid-driven impacts on reservoir quality and establishes a comprehensive genetic model for reservoir evolution. Results identify five distinct tectonic fracturing phases. Phases 1, 2, and 4 involved calcite infilling precipitated from seawater and meteoric freshwater, with fluid inclusion homogenization temperatures of 62–87 °C, 57–91 °C, and 94–126 °C, formed during the Caledonian–Hercynian, Early Hercynian, and Indosinian–Yanshanian periods, respectively. Phase 3 featured hydrothermal dolomite infilling during the Hercynian, with fluid inclusion homogenization temperatures ranging from 128 to 163 °C, whereas Phase 5 remained unfilled during the Himalayan. Constrained by the U–Pb age interval of 445.2–436.5 Ma acquired from vug-filling calcite together with cross-cutting petrographic relationships, multi-stage meteoric freshwater dissolution mainly occurred from Middle Caledonian Episode III (447–443.7 Ma) to the Early Hercynian (460–359 Ma). Reservoirs within the Penglaiba–Lower Yingshan Formations underwent a complex evolution comprising syngenetic-to-early diagenetic pore development, Middle Caledonian–Early Hercynian weathering crust karstification and dedolomitization, and Late Hercynian hydrothermal dissolution-infilling, ultimately resulting in the formation of tectonic-karst composite reservoirs. Full article

Permian sedimentary manganese carbonate deposits in the Qiling Basin exhibit substantial resource potential, yet their depositional environments and precipitation pathways remain insufficiently constrained. This study integrates petrographic, mineralogical, whole-rock geochemical, and carbonate C–O isotope data from the Shuibutou Mn deposit in southern Hunan. We compare this deposit with the coeval Dongxiangqiao deposit and other Permian marine sedimentary Mn deposits to constrain its depositional setting, Mn-carbonate precipitation mechanisms, and potential Mn sources. The Shuibutou ores contain 10.88–17.18 wt.% MnO and are characterized by spherulitic–oolitic textures, abundant bioclasts, and framboidal pyrite. Mo–U enrichment indicates anoxic bottom waters, whereas the near-marine δ¹³C_carb values of ore carbonates (−0.24‰ to 1.28‰) are consistent with precipitation within a marine carbonate system and suggest direct precipitation of Mn(II) carbonates from dissolved Mn²⁺ under anoxic conditions. In this setting, dissolved Mn²⁺ accumulated below the chemocline. Partial dissolution of platform-derived calcite grains near the chemocline increased local dissolved inorganic carbon and alkalinity, driving Mn-carbonate supersaturation and the authigenic precipitation of manganoan calcite, ultimately forming manganese carbonate ores. The low Al/(Al + Fe + Mn) ratios, high Fe/Ti ratios, and Co–Ni–Zn and REY geochemical characteristics are consistent with a possible contribution from Mn-rich deep fluids to the dissolved Mn²⁺ inventory of the basin waters. Similarities in mineralogy, geochemistry, and depositional setting between Shuibutou and Dongxiangqiao point to a possible regional role for the direct precipitation of Mn(II) carbonates under anoxic conditions in the Middle Permian Qiling Basin. Relatively deep intraplatform basins may therefore represent favorable targets for manganese carbonate exploration and provide a reference for exploration targeting of Permian sedimentary Mn deposits within the Qiling Basin. Full article

The Dafosi well field is a typical Huang-Long Jurassic low-rank coalbed methane (CBM) field. Clarifying its CBM geochemical characteristics and the mechanisms of its formation is of significant importance for deepening the understanding of the formation mechanisms of low-rank CBM in China and for the scientific assessment of its resource potential. A total of eight gas emission samples from six coalbed methane wells in the Dafosi coalfield were collected, along with 22 coal samples from the 4^# coal seam. Detailed analyses of microscopic coal petrographic components, gas chemical compositions, and carbon isotopes were performed. By integrating data from the 20 relevant literature sources on coalbed gas composition and isotopic characteristics within the study area, a comprehensive dataset comprising 28 sets was utilized to examine the carbon isotope characteristics and genesis types of both CH₄ and CO₂ in the coalbeds, as well as elucidate the mechanism behind CH₄ carbon isotope depletion. The findings indicate that in the primary 4^# coal seam’s microscopic petrographic composition, the organic matter content is considerably higher, averaging 93.2%. Among these, the inertinite group is dominant, averaging 68.2%; the vitrinite group is the next most abundant, averaging 22.8%. The CBM composition is predominantly CH₄, with concentrations varying from 68.753% to 98.006%, averaging 80.276%. N₂ concentrations range from 1.259% to 29.926%, averaging 17.476%. CO₂ concentrations vary from 0.04% to 2.380%, averaging 1.032%. The average concentration of heavier hydrocarbons C₂ and above is less than 0.078%, indicative of typical dry gas characteristics, C₁/C_1~n > 0.999. The concentration of CH₄ and N₂ was negatively correlated. δ¹³C₁ ranges from −87.200‰ to −62.400‰, averaging −75.802‰. CH₄ is composed of secondary biogenic gas with dominant content and a small amount of thermogenic gas. δ¹³C_CO2 ranges from −41.693‰ to −7.065‰, averaging −20.016‰. CO₂ is an organic gas, mainly derived from thermal degradation and microbial degradation of organic matter. The mechanism responsible for the light carbon isotopic composition of δ¹³C₁ lies in the fact that most of CH₄ is produced by CO₂ reduction, and a small amount is produced by acetic acid fermentation. In the gas generation process of these two pathways, biogenic methane will eventually enrich light carbon isotopes, resulting in light δ¹³C₁. Full article

To elucidate the formation mechanisms of carbonate cement in the Chang 8 tight sandstone reservoir of the Upper Triassic Yanchang Formation (Jiyuan Area), the types, paragenetic stages, and genesis of the cement were investigated via thin-section petrography, carbon–oxygen isotope analysis, and fluid inclusion microthermometry. Results indicate two distinct generations of carbonate cement within the Chang 8 reservoir: early micritic calcite cement and late sparry to coarsely crystalline ferroan calcite cement. The late ferroan calcite cement exhibits δ¹³C_PDB values spanning from −7.02‰ to −12.51‰ and δ¹⁸O_PDB values ranging from −18.81‰ to −30.24‰. The early micritic calcite cement is interpreted to have precipitated from supersaturated alkaline pore fluids during the shallow burial stage (Stage A of early diagenesis) at the close of the Late Triassic. Conversely, the late ferroan calcite cement formed during the Early Cretaceous at temperatures between 100 °C and 110 °C, and its genesis is closely linked to organic-acid-related fluids. These findings elucidate the characteristics of carbonate cements across different stages and have significant implications for predicting the distribution of high-quality reservoirs and for providing guidance for future exploration and development. Full article

The Çıralı (Yanartaş) gas seepage system in the Tekirova Peridotite, SW Türkiye, is an ophiolitic H₂–CH₄ system associated with serpentinized ultramafic rocks and fault-controlled pathways. This study evaluates molecular compositions, C₁–C₃ compound-specific carbon isotope data, and methane hydrogen isotope compositions from four newly sampled gas outlets together with previously published data for which the full parameter set is available. The new samples contain 85.5–91.6% CH₄ and 2.6–5.3% H₂, with δ¹³C-CH₄ values of −7.3 to −4.4‰ and δ²H-CH₄ values of −121 to −104‰. The C₁–C₂ isotope reversal index (RI₁₂) ranges from +13.6 to +14.5‰, whereas the C₂–C₃ isotope proximity index (PI₂₃) ranges from 0.2 to 1.3‰. These values indicate the clear isotopic decoupling of methane from ethane and propane, whereas the C₂–C₃ pair shows comparatively small isotopic differences. The same relative pattern occurs at all four outlets, indicating consistency between samples. The results are consistent with a multistage model in which C₂+ components are compatible with a thermogenic contribution, whereas methane may have been affected by serpentinization-related H₂ input, fracture-controlled flow, and shallow ophiolitic modification. Catalytic CO₂ hydrogenation is evaluated not as a demonstrated field-scale process but as a hypothesis requiring testing in chromitite–serpentinite-related microenvironments. Full article

Measurements of charge-changing cross-sections were developed as a method for determining proton radii, particularly for unstable, short-lived nuclei. Such cross-sections must be measured with high precision to determine the precise charge radii. However, there are complexities in the experimental method leading to uncertainties in determining precise nuclear radii. Therefore, good models describing the complex physics of charged particle interactions are needed in order to validate the experimental method and to estimate the contribution of systematic uncertainties. GEANT4 is a Monte Carlo simulation code widely used to describe interactions in heavy-ion collisions over a broad energy range, ranging from atomic physics to cosmic-ray energies. Experimental measurements of charge-changing reactions for carbon isotopes ^10,12C on different secondary targets were performed. In the present work, the experimental detector geometry, beam profile, and detector configuration were implemented in GEANT4 simulations in order to reproduce the experimental conditions as closely as possible. The experimentally obtained spectra are compared with the corresponding GEANT4 simulations to validate the interpretation of the measured spectra and assess systematic effects. Also, the secondary particle yield ratio is deduced and compared with GEANT4 results. Full article

Carbonate jade has emerged as a recently recognized commercial variety in the Chinese gemstone market. Systematic gemological and mineralogical investigations on carbonate jade, however, remain very scarce. Three Xinjiang calcite-dominated jade samples were investigated by using Fourier-transform infrared (FTIR) spectroscopy, Raman spectroscopy, ultraviolet-visible (UV-Vis) absorption spectroscopy, microbeam X-ray fluorescence (Micro-XRF) spectrometry, trace element analysis, in situ U-Pb dating, and C-O isotope analysis. The orange-red color originates from staining by hematite and magnetite inclusions, while the green color is produced by d-d electronic transitions of lattice-bound Fe³⁺ and Mn²⁺. The provenance comparison reveals systematic differences in trace element compositions between the Xinjiang carbonate jade and Pakistani Lvwen stone: the Xinjiang samples are characterized by extremely low Cu and Sr contents, whereas the Pakistani Lvwen stone has high Cu, Mn and Sr contents, and low Fe content. The U-Pb age obtained for the Xinjiang carbonate jade sample coincides with a Late Cretaceous rapid cooling event. Enriched light rare earth element (LREE) and C-O isotope (δ¹³C_V-PDB = −1.19–2.21‰, δ¹⁸O_V-SMOW = 15.00–20.01‰) signatures indicate that the carbonate-precipitating fluids were derived from marine carbonate wall rocks. These findings provide new mineralogical and geochemical constraints on the coloration mechanism, provenance, and fluid evolution of carbonate jade from Xinjiang. Full article

Solid electrolyte interphase (SEI) characterization is needed to interpret the performance, degradation, and lifetime of graphite and Si-containing carbon-based negative electrodes in lithium-ion batteries. However, SEI claims are often difficult to compare because measured signals, inferred assignments, sample history, and electrode architecture are not always clearly separated. This review presents a claim-bounded framework for SEI characterization that distinguishes direct observables from inferred chemical, molecular, structural, morphological, and functional information. Photoelectron spectroscopy methods provide chemical-state and relative-depth-sensitivity constraints; secondary-ion mass spectrometry methods provide fragment and isotope distributions; vibrational spectroscopies support functional-group and local vibrational evidence; nuclear magnetic resonance and molecular mass spectrometry provide molecular or product-level constraints; and microscopy, tomography, and atomic force microscopy provide morphology, architecture, local thickness, topography, and mechanical response. Across these methods, rinsing, drying, sputtering, beam exposure, extraction, and limited sampling can alter the observable and therefore the defensible claim. The review emphasizes the distinction between native electrode-associated SEI features and extracted, soluble, or electrolyte-phase products, and between morphology-only evidence and chemically assigned morphology. It concludes by proposing claim-driven correlative workflows and reporting guidance for reproducible interpretation on graphite, Si/graphite, Si/C, and carbon-coated Si architectures where directly studied or present. Full article

Lethal foodborne illness outbreaks represent a critical intersection of public health surveillance, environmental health, and forensic toxicology. When acute gastrointestinal syndromes lead to sudden death, traditional postmortem investigation techniques are often hindered by tissue autolysis and the overgrowth of putrefactive microflora, which complicate conventional microbiological assays. This review establishes a comprehensive framework for chemical forensics by evaluating the utility of stable isotope analysis (SIA) as a supportive, probabilistic chemical proxy to complement traditional epidemiological investigations of postmortem food contamination sources. Following JBI scoping review guidelines and the PRISMA-ScR reporting framework, data from 42 peer-reviewed articles (2000–2026) were charted and synthesized to map natural isotopic variations (δ¹³C, δ¹⁵N, δ¹⁸O, δ²H and δ³⁴S) across both forensic decedents and environmental reservoirs. The findings outline a structured, multi-tissue diagnostic cascade governed by biological metabolic turnover rates: unabsorbed gastric chyme provides a direct chemical match to contaminated source food items within a hyper-acute 0–6 h window; high-turnover visceral matrices (liver, blood plasma) shift to reflect acute exposure profiles within 1–7 days; and continuously fixed keratinized matrices (hair, nails) archive multi-month dietary and transcontinental transit histories. Furthermore, compound-specific isotope analysis (CSIA) of individual amino acids offers unprecedented structural resolution, utilizing the carbon discrimination metric (Δ¹³C_glu-phe) to differentiate pristine agricultural signatures from endogenous metabolic distortions while biochemically verifying pre-mortem physiological stress and hyper-catabolic muscle wasting. Taphonomic thresholds were explicitly defined, establishing that bulk visceral soft tissues remain isotopically stable (±0.3‰) for up to 48 h at room temperature (~21 °C) before microbially induced nitrogen enrichment (δ¹⁵N > +2.8‰) alters native profiles, whereas hair and nail keratin maintain absolute isotopic stability for over 180 days postmortem. When pristine multi-isotope signatures are coupled with mandatory chloroform–methanol lipid extraction and processed through spatial Bayesian assignment models, geographic provenance tracking via environmental isoscapes achieves a predictive accuracy of 97%. This review introduces a standardized environmental health protocol designed to harmonize field environmental sampling with medical autopsies. This protocol provides a legally robust strategy for investigating unresolved lethal foodborne illness case-outbreaks, particularly those involving pediatric mortalities linked to the consumption of counterfeit or fraudulent food products in low- and middle-income countries. Furthermore, it aims to strengthen national and municipal legal frameworks and international biosecurity enforcement. Full article

Hydrothermal systems contain diverse alkanes derived from biological and geological processes, providing potential carbon and energy sources for microorganisms. However, cultivated thermophilic alkane-utilizing bacteria from hydrothermal environments remain poorly characterized. In this study, a strain L01 was isolated from a deep-sea hydrothermal vent and identified as an alkane-degrading bacterium. The strain L01 grew at 55 °C and pH 7.0 in medium supplemented with n-hexadecane under microoxic conditions. Cells were elongated rods approximately 10–20 μm long and ~0.2 μm wide. Phylogenetic analyses based on 16S rRNA gene sequence similarity (93.11% to the closest described relative), average amino acid identity (AAI, 66.27–66.58%), average nucleotide identity (ANI, 80.80–83.05%), and digital DNA-DNA hybridization (dDDH, 12.5–20.8%) demonstrated that strain L01 represents a previously unrecognized genus within the family Symbiobacteriaceae, for which the provisional name “Thermalkanevorax longiformis” is proposed. An isotope tracing experiment together with genomics and transcriptomics revealed coordinated physiological and metabolic responses associated with n-hexadecane utilization by strain L01. These findings provide a cultivated representative of the family Symbiobacteriaceae with physiological and metabolic responses to n-hexadecane, thereby providing a basis for further investigation of hydrocarbon metabolism. Full article

Norway spruce (Picea abies L.) growing in mountain forests is a sensitive indicator of environmental change, but its growth response may be strongly modified by local site conditions, which is important for sustainable forest management under climate change. This study examined two spruce populations in the upper montane zone of the Śnieżnik Massif, Eastern Sudetes, southwestern Poland: one growing on a raised bog (Sadzonki—TS) and the other on mineral soil (Owczarnia—OW). Tree-ring width (TRW) chronologies were developed from 59 sampled trees represented by increment cores and stem discs, covering 1781–2023 for TS and 1800–2023 for OW. Annual δ¹³C analysis was performed for a selected TS tree, and decadal wood geochemistry was analyzed for a selected disc. Spruces growing on the raised bog showed tree-ring widths that were less than half those of trees growing on mineral soil. TRW was mainly controlled by summer or spring–summer temperature, while precipitation had a stronger positive effect at the mineral-soil site. δ¹³C showed weak relationships with TRW but negative correlations with mean annual and summer temperature. Elevated concentrations of Na, K, Ca, Mg, Fe, Mn, Cu, Zn, and Pb occurred mainly in 1941–1950 and 1971–1980, indicating the influence of historical air pollution. The contrasting growth trends and health status of the two populations demonstrate that local habitat conditions strongly shape spruce responses to environmental change and should be considered in sustainable mountain forest conservation and adaptation strategies. Full article