Abstract A precise methodology for determining the growth mode of oxide layers on metallic materials at high temperatures is proposed. The approach combines sequential isotopic oxidation tests (using 16 O and 18 O isotopes) with secondary ion mass spectrometry (SIMS and nanoSIMS) analyses. NanoSIMS provides high-resolution localisation of oxygen diffusion pathways and oxide growth zones. However, its limited accessibility and specialised instrumentation can pose practical constraints. In contrast, dynamic SIMS offers broader accessibility and the ability to directly quantify oxygen isotope ratios across depth profiles. The detection of both conventional atomic (O − ) and diatomic (O 2 − ) oxygen signals in dynamic SIMS analysis proved highly effective in offering insights on oxide growth mode, closely replicating nanoSIMS results. The diatomic signal analysis complements the atomic signal data by improving the understanding of oxidant transport within the oxide layer. The methodology was validated through its application to a Co-10Cr alloy oxidised at 900 °C in O 2 , under sequential exposures to 16 O and 18 O isotopes. Both SIMS and nanoSIMS revealed the formation of a duplex oxide layer, consisting of an outer layer formed by outward Co cation diffusion and an inner layer growing by inward oxygen penetration, particularly in the grain-boundary regions of the outer oxide layer. The alloy is proposed to oxidise according to the Available Space Model.

ABSTRACTRationaleIncreasingly, more laboratories are measuring the triple oxygen isotope values of phosphate. Standardization is key to having good interlaboratory results. Here, we present the triple oxygen isotope values of a suite of standards using fluorination and compare them with previously reported triple oxygen isotope values.MethodsSilver phosphate (~2–3 mg) was fluorinated in nickel reaction vessels, and the resulting O2 was analyzed on a Thermo MAT 253 for the paired δ17O‐δ18O value (Δ′17O). Although the δ18O and δ17O values were variable, the fluorination reaction progresses along a slope of ~0.528, indicating that the Δ′17O is constant when calculated using a λref = 0.528. The 18O/16O ratio was obtained using a TC/EA, and the δ17O value was corrected based on the measured Δ′17O value from fluorination and the δ18O values obtained on the TC/EA.ResultsWe provide δ17O, δ18O, and Δ′17O values for the following silver phosphate standards: NBS120c, USGS80, USGS81, AGLox, and B2207. Two new standards are also reported and available for distribution. To report our values on the VSMOW2‐SLAP2 scale, we measured common silicate standards: San Carlos Olivine, NBS28, NMQ, and SKFS that have been calibrated to VSMOW2‐SLAP2. Our reported Δ′17O error for silver phosphate is 10 per meg, calculated using the average long‐term standard deviation of our two most replicated standards.ConclusionsWe report the δ17O, δ18O, and Δ′17O values for a large suite of silver phosphate standards and present two new standards that can be used for interlaboratory calibration. Our results are reported on the VSMOW2‐SLAP2 scale by measuring silicates on the same instrument with the same reference gas. The fluorination method in nickel reaction vessels is easily adapted to other laboratories that have fluorination lines. Only 2–3 mg of silver phosphate is needed for Δ′17O measurements when paired with δ18O values using the TC‐EA technique.

Integrated isotopic and molecular insights reveal agricultural legacy phosphorus driving Nanyihu Lake eutrophication.

Several chemical and isotopic methods have been suggested for tracing the wine origin in relation to the climate/meteorological conditions of the vineyard areas. IRMS (Isotope Ratio Mass Spectrometer) is one of these tools. In the Oltrepò Pavese (Lombardia Region, Pavia Province, Italy) and in the Illasi/Mezzane areas (Veneto Region, Verona Province, Italy), for the harvests of 2021 and 2022, a linear correlation between δ18O of the grape must water (δ18Om) and the potential evapotranspiration (ETO) and crop evapotranspiration (ETC) has been found. ETO and ETC were calculated according to the FAO‐56 model using meteorological data from the meteorological stations located close to the vineyards studied. We can state that the intercept obtained for the linear correlation δ18Om on ETC is an estimate of the isotopic features of the water absorbed by plants during the late stage of the grape ripening. The obtained data allowed us to estimate the isotopic enrichment factor ε18Om−PW (m = grape must water and PW = precipitation water), which depends on climatic/meteorological conditions. Subsequently, the climatic parameters that mostly influence the oxygen isotope variation in grape must water have been identified using a correlation coefficient.

Tracing nitrate sources and transformations using nitrogen and oxygen isotopes in the second largest freshwater lake of China

Purification techniques for oxygen isotope analysis of inorganic phosphate across environmental matrices: A cross-discipline review.

Optimization of gas chromatography-isotope ratio mass spectrometry oxygen isotope analysis method and recommendations for precision control.

Quantification of runoff composition of Aksu River basin in the Tianshan Mountains, northwest China, indicated by stable hydrogen and oxygen isotopes

Nitrogen and oxygen isotopes in nitrate and nitrite in the polluted surface waters from the Arno River Basin (Central Italy).

Understanding the influence of landcover on spring dynamics and evaporation, in Himalayan region, using stable isotope and discharge.

Theoretical evaluation of kinetic triple oxygen isotope fractionation during sulfite oxidation by atmospheric oxygen

Tritium baseline concentration and the origins of water and solute in precipitation elucidated from monthly data in Osaka, Japan.

Abstract The altitude effect (AE) of stable isotopes in meteoric water ( δ 18 O and δ 2 H), that is, the depletion of water isotopes with increasing altitude, is an important theoretical assumption of isotope‐based paleoaltimetry. However, this assumption has recently been challenged, as many in situ observations fail to consistently demonstrate the expected negative correlation between altitude and isotope values. Here we used 1,255 records of surface water isotopes to investigate AE and inverse altitude effect (IAE) and their mechanisms in arid Central Asia. The results show that isotope altitude gradients across Central Asia are weaker than the global average. Comparisons of the gradients for both the mountain‐basin system and mountain system reveal that the windward and leeward slopes of the westerlies consistently exhibit opposite gradients: AE on the windward side and IAE on the leeward. The observed IAE on the leeward slope across all basins is influenced by topography and local circulation. The orientation of mountain ranges perpendicular to large‐scale westerly circulation blocks eastward transport of westerly moisture, and the resulting longer moisture pathways weaken AE. Stronger local circulation and sub‐cloud evaporation processes enrich water isotopes in the leeward mountain regions, diminishing AE and even leading to the emergence of IAE. Our results highlight the impact of local circulation on water isotopes during different uplift phases when using stable hydrogen and oxygen isotopes to reconstruct paleoelevation.

Despite the closure of the Semipalatinsk nuclear test site (STS) more than 30 years ago, water continues to transport radioactive contamination beyond the boundaries of the “Degelen” test site. Therefore, assessing the formation of water resources at this test site is highly relevant, particularly in terms of forecasting the development of radioactive contamination at the STS. In this case, isotope hydrology is the most promising method for understanding these processes. The aquatic environment at the “Degelen” test site consists of radioactively contaminated tunnel water, streams, and groundwater. This paper presents the research results regarding the determination of stable isotopes of hydrogen and oxygen for the aquatic environment of the “Degelen” test site. 3H concentrations and the chemical composition of water at the site were also determined. Analysis of the water’s isotopic composition (δ2H and δ18O) showed that the tunnel and stream water are formed by precipitation (snowmelt and rain). In summer, when precipitation is low, atmospheric condensation contributes significantly to recharge at the “Degelen” test site. The high radionuclide content of tunnel water leads to the contamination of stream water, and, to a lesser extent, groundwater. The 3H content of tunnel water can reach 260 kBq/L, and that of stream water can reach 58 kBq/L, both of which exceed the established standards in the Republic of Kazakhstan.

Northern Vietnam’s karst landscapes offer an untapped potential for paleo-monsoon research, complementing the extensive speleothem records of Southwest China. Here, we surveyed 51 caves across seven provinces, targeting those with humidity exceeding 95% from 2017 to 2024, and collected 127 broken stalagmites to evaluate their stable-isotope potential (δ18O, δ13C) as paleoclimate proxies. Focusing on caves in Hoa Binh and nearby karst-rich regions, we applied Hendy tests to 56 subsamples of eight layers on four stalagmites, NS3, HS3, HS7, and HS16, to assess the isotopic equilibrium conditions. The deposition intervals of the four stalagmites, determined using U/Th dating, range from 36 to 60 thousand years ago (ka). Small 1-sigma variations of ±0.04−0.20‰ in coeval δ18O values across all eight layers suggest deposition under near oxygen isotope equilibrium. Combined with fast growth rates exceeding 0.09 mm/year, this evidence suggests high-resolution potential for paleohydroclimate reconstruction using stalagmite δ18O data. However, one-sigma variations of ±0.04−0.71‰ of coeval δ13C data reflect relatively large carbon isotopic fractionation during the degassing process. It suggests that stalagmite δ13C records from these caves should be carefully evaluated before use in paleoclimate reconstructions.

The Eastern Zhou period (771-221 BC), characterized by social stratification, was marked by important inequality. Here the authors analyse 32 skeletons from Songzhuang Cemetery in Henan Province using sex-specific peptides, ancient DNA and isotopes to explore multidimensional inequality in sexes, diet and mobility. DNA and proteomic analyses show that young women were marginalized as sacrificial victims (22 out of 26 human sacrifices were female). Carbon and nitrogen isotopic analyses suggest dietary differences by social class, with the nobility consuming more high-protein and millet-based diets than sacrificial companions, who themselves show intra-group dietary variation (δ13Cbone,nobles = -8.6‰; δ13Cbone,human sacrifice group one = -10.9‰; δ13Cbone,human sacrifice group two = -14.1‰; δ15Nbone,nobles = 11.6‰; δ15Nbone,human sacrifice group one = 8.5‰; δ15Nbone,human sacrifice group two = 7.7‰). Enamel and dentin isotope data indicate that these dietary inequalities were established from childhood (δ13Cenamel,nobles = -1.5‰; δ13Cenamel,human sacrifice group one = -3.8‰; δ13Cenamel,human sacrifice group two = -6.9‰). Strontium and oxygen isotope evidence shows that a high proportion of the nobles were non-local migrants. Genetic analysis reveals a genealogy linking four noblewomen to a sacrificial victim, highlighting the importance of kinship and marital alliances in maintaining social status. Despite class rigidity, dental isotope sequences in M18 reveal that two individuals experienced childhood dietary shifts, indicating rare class mobility.

The isotopic composition of glucose carries the signature of the environmental and metabolic processes that act on it, but most conventional isotope analytical methods cannot resolve its intramolecular isotopic structure. Here, we present a new method for position-specific isotope analysis (PSIA) of carbon in glucose using electrospray ionization-Orbitrap (ESI-Orbitrap) mass spectrometry. This method measures δ13C values at five unique intramolecular sites in glucose at natural isotope abundance and requires <50 μg of glucose per sample, over 3 orders of magnitude less than similar measurements by nuclear magnetic resonance (NMR). By oxidizing glucose to gluconate to improve both ionization yield and fragmentation behavior and measuring with ESI-Orbitrap, we resolve the isotopic composition of the molecular ion and four fragment ions with analytical precision of 0.5-0.8‰ (2 SE). Using a positionally labeled glucose standard, we demonstrate the accuracy of the measurement for both molecular average and position-specific carbon isotope composition. Our method reproduces intramolecular δ13C patterns previously demonstrated for natural sugars formed through C3 and C4 photosynthetic pathways while enabling substantially higher throughput and sensitivity. This is the first application of Orbitrap-PSIA to a carbohydrate, and it enables the tracing of sugar fluxes in environmental, biomedical, and ecological systems. Future developments could extend the method to include oxygen and hydrogen isotopes, further enhancing its value for investigating glucose dynamics across many natural settings.

The 190 Pt‐ 186 Os isotope system has unique potential in tracing planetary and geological processes. Elaborate efforts have been made to improve the accuracy and precision of 190 Pt‐ 186 Os isotope measurements over the past decades, which include investigating Pt‐W‐Re oxides and oxygen isotope interferences in Os isotope measurements and employing amplifiers with higher resistance to achieve higher signal voltages. However, several problems still limit the accuracy and precision of 186 Os/ 188 Os ratios. We examine key factors that may affect Os isotope measurement results. Baseline drift during measurement contributes to deviations in isotopic ratios, resulting in a bias from the reference value. While it is debated whether W oxide interferences are present, our findings show that potential real W oxide interferences may exist, which can significantly disturb results. In addition, incorporating oxygen isotope monitoring before and after each measurement lowers the measurement uncertainty. Under the influence of W oxide interferences and baseline drift, significant residual correlations between 186 Os/ 188 Os and 184 Os/ 188 Os are observed. We advocate a residual correction approach to correct these residual correlations, which can effectively reduce the uncertainty of 186 Os/ 188 Os ratios. Corrected isotope ratios for the same reference materials show slight discrepancies from published values, which may be ascribed to differences in Faraday cup efficiency. Hence, we recommend a standardising procedure to regulate Os isotope ratio results across reference materials, enabling direct comparison of data from different laboratories and different time periods. At least two reference materials should be used to monitor the consistency of instrument and the reliability of measurement results. Based on this enhanced method, we present high‐precision Os isotope ratios for our newly prepared reference material CUGB: 184 Os/ 188 Os = 0.0013036 ± 0.0000007, 186 Os/ 188 Os = 0.1199711 ± 0.0000060, 187 Os/ 188 Os = 0.1739252 ± 0.0000141, 189 Os/ 188 Os = 1.219709 ± 0.000010, 190 Os/ 188 Os = 1.983793 ± 0.000011 (2 s ).

Stable isotopes of carbon, oxygen and hydrogen in tree rings provide a record of plant physiological processes and environmental variability. Although an increasing number of studies now apply triple-isotope approaches, no investigation has yet tested their temporal stability over millennial timescales or assessed the relative impacts of physiology versus climate on long-term isotopic signals. Here, we used 9000 years of multi-isotope records from co-occurring deciduous larch (Larix decidua) and evergreen cembra pine (Pinus cembra) at the Alpine treeline. We found a high interspecies coherence for δ18O throughout the Holocene with a robust summer hydroclimate sensitivity, confirming its dominance by environmental drivers. In contrast, δ13C and δ2H show weaker and less stable coherence, reflecting species-specific physiology. Larch exhibits tight δ2H-δ18O and δ2H-δ13C correlations and stronger climate sensitivity, consistent with its reliance on freshly assimilated carbon. Pine, by contrast, shows weaker δ2H-climate relationships and frequent decoupling from δ13C and δ18O, reflecting potential storage use and metabolic fractionations. Thus, inter-isotope relationships reveal that δ18O is a robust long-term climate proxy, while δ13C and δ2H encode contrasting carbon-use strategies and metabolic processes across species that may vary over time. Together, these findings demonstrate that multi-isotope, multi-species approaches not only strengthen climate reconstructions but also provide a physiological dimension to long-term isotope records.

Abstract Hematite is a resilient iron oxide that can persists on the surfaces of terrestrial planets for billions of years, preserving the isotopic signature of past water-rock interaction. Its oxygen isotopic composition can be determined by bulk and in-situ methods. However, in-situ oxygen isotope analysis of hematite by secondary ion mass spectrometry (SIMS) is complicated by instrument induced crystal orientation effects and crystallochemical zoning within the sample. In this study, we applied a multi-method approach to deconvolve these effects in naturally occurring single hematite crystals from recrystallized Precambrian banded iron-formations. Three well-formed hematite crystals, sourced from the Hamersley Province, Australia, and the Quadrilátero Ferrífero (QF), Brazil, were analyzed using a combination of electron back-scattered diffraction (EBSD), laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS) elemental mapping, laser fluorination (δ18OLF), and Sensitive High Resolution Ion Microprobe – Stable Isotopes (SHRIMP-SI) oxygen isotope analysis. Although these hematite crystals appeared macroscopically pristine and homogeneous, they exhibit complex internal textures that include growth zoning, twining, fracturing, and re-healing, which are not visible optically. Consequently, measured hematite isotopic composition varies widely across a single crystal, making it difficult to determine the isotopic composition of the solution from which the mineral precipitated. This study illustrates how a combination of high-spatial resolution tools provides an effective approach to characterize the oxygen isotope compositions of mineralizing solutions that precipitated or altered a hematite crystal. Our results, in a small number of samples, reveal that enrichment processes affecting Precambrian banded iron-formations in Australia and Brazil involved interaction with isotopically distinct fluids, despite similarities in starting materials and final products.