Isotope Ratio Measurements Research Articles

Lead geochemistry of sediments in Galveston Bay, Texas

The geochemical behavior of Pb in terrestrial and coastal water systems significantly influences Pb biogeochemical cycling and pollutant exchange at the land-sea continuum. An ideal case study of Pb environmental geochemistry is Galveston Bay, an anthropogenic estuary exposed to industrial runoff, wastewater and shipping vessel spills but also fed by natural rivers. Here, sediments from Galveston Bay were measured for Pb isotope ratios and abundances to constrain Pb sources and fluxes and understand Pb pollution history in the bay. Lead isotopes have been established as source tracers of environmental pollution and allow Pb sources to be reliably fingerprinted and identified. Sediments were leached to distinguish authigenic sediment coatings from lithogenic residual sediments, in addition to bulk sediment digestions. Total Pb concentrations ranged from 1.76 µg/g–29.19 µg/g in bulk digests, which are below federal toxicity thresholds and aligns well with prior measurements of Pb in Galveston Bay sediments in the 20th century. Lead concentrations are spatially constrained by flocculation in eastern bay areas where the Trinity River enters the bay and positively temporally correlated to freshwater discharge. Sediment 206Pb/204Pb, 207Pb/204Pb, and 208Pb/204Pb ratios range between 18.338–19.777±0.002, 15.557–15.755±0.002 and 37.913–43.340±0.005, respectively, and were used in an advanced Bayesian isotope mixing model to identify Pb sources in the Galveston Bay sediment fractions analyzed. Anthropogenic sources supply approximately 83.8%, 16.6% and 25.5% of Pb to the leachates, residues and bulk sediments, respectively. This study showcases the importance of estuaries in moderating terrestrial and marine Pb distribution and provides insight for future contaminant studies in Galveston Bay and other estuarine systems around the world.MAIN FINDINGS Pb isotope ratio and abundance measurements of Galveston Bay sediments demonstrate significant anthropogenic Pb inputs to the estuary despite low Pb levels.

Characterization of Four Copper Materials for Application as Reference Materials for High Precision Copper Isotope Analysis by Laser Ablation Inductively Coupled Plasma Multi-Collector Mass Spectrometry

Laser ablation inductively coupled plasma multi-collector mass spectrometry (LA-MC-ICP-MS) allows rapid, in situ, highly precise measurements of Cu isotope ratios of native Cu and Cu-bearing minerals. However, the National Institute of Standards and Technology Cu-metal isotope standard NIST SRM976 that is commonly used to calibrate LA-MC-ICP-MS Cu isotope measurements of native Cu is no longer available. We have investigated the suitability of four Cu metal materials, SSC-1, SSC-3 and SSC-4 (cathode Cu metal rods) and CUPD-1 (Cu anode sawings), originally developed by the Canada Centre for Mineral and Energy Technology (CANMET) as certified reference materials for trace element analysis, as Cu isotope reference materials for LA-MC-ICP-MS analysis and solution nebulization (SN) of Cu. The Cu isotopic composition and homogeneity of these four materials were characterised by SN- and LA-MC-ICP-MS, and are reported for the first time. The bulk Cu isotopic compositions, expressed as δ65CuSRM976 in per mil (‰) relative to NIST SRM976 with combined uncertainties (U, k = 2), of SSC-1, SSC-3 and SSC-4, determined utilizing SN-MC-ICP-MS, are identical within analytical uncertainty at 0.03 ± 0.07‰ (n = 29), 0.04 ± 0.04‰ (n = 28), and 0.05 ± 0.08‰ (n = 29), respectively; the composition of CUPD-1 is 2.14 ± 0.08‰ (n = 28). The compositions are 0.01 ± 0.07‰ (n = 29), 0.04 ± 0.06‰ (n = 29), 0.03 ± 0.06‰ (n = 28) and 2.15 ± 0.06‰ (n = 28), respectively, relative to the European Reference Material ERM®-AE633 Cu isotope standard. The Cu isotope homogeneity of the four new reference materials was assessed by determining whether multiple individual in situ Cu isotope measurements made by LA-MC-ICP-MS analysis (43 µm spot size), using each of the other three reference materials as a calibrator, approximate a single normal distribution. We also investigate whether there are statistically significant differences between the mean δ65Cu values of three independent data sets for each of the Cu isotope reference materials using one-way analysis of variance (ANOVA). Normality tests (graphical assessment of normal distribution quantile-quantile plots, and the Shapiro-Wilk, Jarque-Bera and reduced chi-squared statistic tests) show that: 1) the Cu isotope data acquired on SSC-1, SSC-3, SSC-4 and CUPD-1 do not depart significantly from a normal distribution, 2) the scatter of the Cu isotope data is due to analytical uncertainty with 95% confidence, and 3) there are no other significant sources of scatter; e.g. heterogeneity of the reference materials. The results of one-way ANOVA reveal that the mean difference of the δ65Cu value for each of the reference materials SSC-1, SSC-3, SSC-4 and CUPD-1 is statistically not significant at the 0.05 level. The mean δ65CuSRM976 values with combined uncertainties (U, k = 2) of SSC-1, SSC-3, SSC-4 and CUPD-1, determined by LA-MC-ICP-MS using each of the other three reference materials as a calibration standard, are 0.03 ± 0.09‰ (n = 132), 0.05 ± 0.09‰ (n = 154), 0.03 ± 0.09‰ (n = 144) and 2.14 ± 0.10‰ (n = 106), respectively. These values are in agreement with those determined by SN-MC-ICP-MS analysis at the 95% confidence level and have excellent precision (2 s.d. ≤ 0.10‰). These results suggest that SSC-1, SSC-3, SSC-4 and CUPD-1 can be considered isotopically homogeneous at a spatial resolution of 43 μm, and they are suitable reference materials for calibration and quality control of in situ and solution nebulization Cu isotope analyses of Cu.

Determination of minor isotope ratios of individual uranium particles by accelerator mass spectrometry.

The determination of uranium isotope ratios in uranium particle is an essential technique in the analysis of environmental samples for nuclear safeguards. At present, mass spectrometry has been widely used to measure isotope ratios of uranium particles. We developed a new analytical method for measuring minor isotope ratios of individual uranium particles directly. The technique includes single particle identification by energy dispersive X-ray spectrometer (EDX), transfer by scanning electron microscope (SEM) combined with micromanipulator and isotope ratios analysis with accelerator mass spectrometry (AMS). The minor isotope ratios of individual uranium particles with four isotopic abundances and different sizes from certified reference materials were measured by AMS. The results show that the relative error (RE, i.e., the deviation of measured value from the certified value) of 234 U/235 U and 234 U/236 U isotope ratios was 9.0% and 19.3%, respectively, and the relative standard deviation (RSD) was within 9.9% and 16%, respectively. The minimum particle determined was about 2 μm. The method was found to be an alternative analytical means for nuclear safeguards.

Optically Switched Dual-Wavelength Cavity Ring-Down Spectrometer for High-Precision Isotope Ratio Measurements of Methane δD in the Near Infrared.

We report a spectrometer employing optically switched dual-wavelength cavity ring-down spectroscopy (OSDW-CRDS) for high-precision measurements of methane isotope ratios. A waveguide optical switch rapidly alternated between two wavelengths to detect absorption by two isotopologues using near-infrared CRDS. This approach alleviated common-mode noise that originated primarily from temperature and frequency fluctuations. We demonstrated the measurement of δD in natural abundance methane to a precision of 2.3 ‰, despite the lack of active temperature or frequency stabilization of the cavity. The ability of alternating OSDW-CRDS to improve the isotope precision in the absence of cavity stabilization were measured by comparing the Allan deviation with that obtained when frequency-stabilizing the cavity length. The system can be extended to a wide variety of applications such as isotope analysis of other species, kinetic isotope effects, ortho-para ratio measurements, and isomer abundance measurements. Furthermore, our technique can be extended to multiple isotope analysis or two species involved in kinetics studies through the use of multiport or high-speed optical switches, respectively.

Single‐Rate Dual‐Domain Mass Transfer Model: Elucidating Temperature Effects

AbstractIn this study, the influence of varying temperatures on the transport behavior of conservative solutes in heterogeneous porous media has been investigated. Column flow experiments employing potassium bromide as tracer were conducted at four temperature levels (3°C, 10°C, 20°C, and 30°C) and the measured electrical conductivity (EC) signal was interpreted through inverse modeling. Additional experiments were performed with deuterium‐enriched water at 10°C and 30°C. For those experiments, deuterium isotope ratios were analyzed alongside anion and cation concentrations. Obtained EC‐based breakthrough curves showed measurable differences in both the observed peak values and tailing intensities that could be clearly attributed to variations in the experimental temperatures. The EC‐based results were further corroborated by the measured isotope ratios and corresponding anion/cation concentrations, although measured differences were less pronounced. The model‐based interpretation of the results employed the standard advection‐dispersion equation as well as three alternative variants that were all based on the single‐rate dual‐domain mass transfer (DDMT) approach, but embracing varying coupling intensities between the experiments. For all variants transport parameters were determined for EC, bromide, and deuterium, respectively. The estimated ranges of the transport parameters all point toward a direct correlation between the effective DDMT rates and the experimental temperature. The observed correlation directly follows the Arrhenius relationship, but is weaker than the one describing the temperature dependence of the molecular diffusion coefficients, therefore pointing to a contribution of non‐diffusive components.

Assessing the potential of online ICP\u2013MS analysis to optimize Ca/matrix separation using DGA Resin for subsequent isotopic analysis

Ca isotopes have gained increasing interest as a diagnostic tool for bone diseases due to the variations in abundances as a consequence of changes in bone-mineral balance. Optimized Ca/matrix separation prior to analysis is a prerequisite for reliable isotope ratio measurements in complex biological matrices such as blood, serum, or urine. The online analysis of analyte/matrix separation by ICP-MS enables direct assessment of elution profiles supporting the optimization process. The integration of transient signals and signal suppression challenge the quantification and interpretation of the elution profiles. Mn and Co remain unretained by the DGA Resin (TrisKem International) from nitric acid. Hence, in the present study, these elements were investigated for their application as standards to monitor signal suppression. Successful analyte quantification was accomplished using a dynamic correction strategy applying a linear gradient of a suppression factor based on Mn and Co intensities. An optimized Ca/matrix separation procedure using DGA Resin is proposed based on the results during online ICP-MS analysis.Graphic abstract

Investigating the feasibility of ICP-MS/MS for differentiating NIST salmon reference materials through determination of Sr and S isotope ratios

Inductively coupled plasma tandem mass spectrometry (ICP-MS/MS) was investigated for possible use in food fraud studies through the measurement of strontium and sulfur isotope ratios. Oxygen mass shift mode was applied to shift 87Sr/86Sr and 34S/32S isotope ratios to their respective oxides, 87Sr16O+/86Sr16O+ and 34S16O+/32S16O+, effecting a gas-phase chemical separation of the elements from Rb and Kr (for Sr) and molecular N and O species, along with P- and S-hydrides (for S). A total least squares regression approach was employed to generate the isotope ratio data from time-resolved analyses, and method uncertainties and accuracies were determined. The utility of the approach was shown by using the Sr and S isotope ratios together to differentiate between NIST RM 8256 Wild-Caught Coho Salmon and NIST RM 8257 Aquacultured Coho Salmon. These materials are currently under development at NIST as certified food fraud standards and method evaluation materials for comprehensive chemical analysis.

A Significant Japanese Coffer: A Multi-disciplinary Approach to Examining Late Sixteenth- — Early Seventeen-Century Export Urushi Ware

ABSTRACT A significant coffer in the Royal Swedish collection, inventory number HGK 406, is examined. The aim is to confirm or add new data concerning its age, provenance, and components of manufacture. The scientific analyses include microscopy of cross and thin sections, wood species identification, scanning electron microscopy with energy-dispersive X-ray spectroscopy, X−ray fluorescence microscopy, pyrolysis-gas chromatography-mass spectrometry, strontium isotope ratio measurement, and radiocarbon dating. To a lesser degree, the investigation also includes excerpting and examining historical documents. The results show that the body wood is Thujopsis dolabrata BUN 1248, a strong indication for a Japanese origin of the coffer. The urushi coating is made with sap harvested in Japan from the species Toxicodendron vernicifluum. The decorations include gold powder, red iron oxide, and cinnabar pigments. Radiocarbon dating supports dating of the coffer, also based on its style, as late sixteenth or early seventeenth century. While all the results may not stand alone, the study shows that a methodology with a multidisciplinary approach can produce new knowledge, as well as support or reject hypotheses arrived at from other kinds of sources.

Vanadium Stable Isotopes in Biota of Terrestrial and Aquatic Food Chains.

Vanadium, a potentially toxic metal, is enriched in the environment from anthropogenic releases, particularly during fossil fuel production and use and steel manufacturing. Metal stable isotopes are sophisticated tools to trace pollution; however, only recent analytical advances have allowed for the accurate and precise measurement of vanadium isotope ratios (δ51V). To examine its potential as a tracer in terrestrial and aquatic ecosystems, δ51V was measured in soil, plant, lichen, marten, and lake sediment from sites near vanadium emissions at oil sands mines (Alberta, Canada) and in the sediment and biota (algae, zooplankton, fish) from a remote subarctic lake (Northwest Territories, Canada). Samples from Alberta had distinct δ51V values with marten liver the lowest (-1.7 ± 0.3‰), followed by lichen (-0.9 ± 0.1‰), soil (-0.7 ± 0.1‰), sediment (-0.5 ± 0.2‰), and plant root (-0.3 ± 0.2‰). Average values were lower than Alberta bitumen and petroleum coke (-0.1 ± 0.1‰). Plant roots had systematically higher δ51V than the soil from which they grew (Δ51Vplant-soil = 0.4 ± 0.1‰), while δ51V of lichen and aquatic biota were lower (0.1-0.3‰) than likely crustal sources. These δ51V measurements in terrestrial and aquatic biota demonstrate promise for tracer applications, although further study of its biological fractionation is needed.

Measurement of uranium isotope ratios in Fukushima-accident contaminated soil samples using multi collector inductively coupled plasma mass spectrometry

In the present study, 137Cs and 238U activity concentrations, 234U/238U activity ratio, and 235U/238U isotope ratio were measured in fifteen soil samples collected from the exclusion zone around the Fukushima Daiichi Nuclear Power Station (FDNPS). The 137Cs activity concentrations of Fukushima-accident contaminated soil samples ranged from 29.9 to 4780 kBq kg−1 with a mean of 2007 kBq kg−1. On the other hand, the 238U activity concentrations of these soil samples ranged from 5.2 to 22.4 Bq kg−1 with a mean of 13.2 Bq kg−1. The activity ratios of 234U/238U ranged from 0.973 to 1.023. The 235U/238U isotope ratios of these exclusion zone soil samples varied from 0.007246 to 0.007260, and they were similar to the natural terrestrial ratio confirming the natural origin. Using isotope dilution technique, the 235U/137Cs activity ratio was theoretically estimated for highly 137Cs contaminated soil samples from Fukushima exclusion zone ranged from 5.01 × 10−8 - 6.16 × 10−7 with a mean value of 2.51 × 10−7.

Roles of collisional dissociation modalities on spectral composition and isotope ratio measurement performance of the liquid sampling – atmospheric pressure glow discharge / orbitrap mass spectrometer coupling

Coupling of the liquid sampling – atmospheric pressure glow discharge (LS-APGD) ionization source with Orbitrap mass spectrometers has demonstrated tremendous success in regards to isotope ratio (IR) measurements. Isotope ratios from a wide variety of analytes have been measured, with a primary focus on the 235U/238U measurement, yielding IR measurement accuracy and precision that meets international targets. Orbitrap mass spectrometers are not commonly associated with either elemental analysis or isotope ratio measurements. Understanding sources of IR errors and imprecision which arise from both the LS-APGD ionization source and the Orbitrap system itself can assist with enhancing measurement figures of merit. Because a variety of solvent related species are generated in the LS-APGD, the preponderance of those species in the orbitrap analyzer affects the recoveries and IR qualities for target analytes. In this work, the effects of the collisional dissociation of solvent-related species are investigated as a source of variability in IR measurements. Additionally, the quadrupole band-pass filter used in the ThermoScientific Q Exactive Focus is investigated for its transmission properties along with the effects of the transmission window on IR accuracy and precision. With these considerations, updated IR measurements are presented for a few analytes, with measurement precision never exceeding 0.71% RSD, and going down to a level of 0.05% for diverse species. It is expected that these considerations will inform how IR measurements should be taken on this platform, with lessons that may be applicable to other instruments.

Effect of weighing uncertainty on assay values by isotope dilution mass spectrometry

Isotope dilution mass spectrometry using traceable standards as spikes coupled with isotope ratio measurements by thermal ionization or inductively coupled plasma mass spectrometer instruments is the preferred methodology for element content determinations and isotopic composition measurements in a variety of applications, especially those involving highly radioactive isotopes like the actinide elements. This assay measurement technique takes advantage of the sensitivity of modern mass spectrometry instrumentation to minimize the amount of material utilized for the measurement and enables the measurement sequence to be automated, with minimal intervention from analyst during the measurement process. LA-UR-20-28878.

Disentangle Kinetic From Equilibrium Fractionation Using Primary (δ17O, δ18O, δD) and Secondary (Δ17O, dex) Stable Isotope Parameters on Samples From the Swiss Precipitation Network

Since 1971 water isotope measurements are being conducted by the Climate and Environmental Physics Division at the University of Bern on precipitation, river- and groundwater collected at several places within Switzerland. The water samples were stored in glass flasks for later analyses with improved instrumentation. Conventional isotope ratio measurements on precipitated water from all stations of the network are well correlated as expected. However, Δ17O as well as dex is anticorrelated to these isotope ratio. The combination of these parameters allow to investigate dependencies on temperature, turbulence factor, and humidity of these values as well as to look into the importance and relative contributions of kinetic to equilibrium fractionations. We used published temperature dependent fractionation factors in combination with a simple Rayleigh model approach to investigate the importance of the meteorological parameters on the isotope ratios. A direct comparison of measured and modeled isotope ratios for primary (δ17O, δ18O and (δD) as well as secondary isotope parameters (Δ17O and dex) is shown.

Precise measurement of 234U/238U, 235U/238U and 236U/238U isotope ratios in Fukushima soils using thermal ionization mass spectrometry

Precise and accurate isotope ratio measurements of 234U/238U, 235U/238U and 236U/238U were performed simultaneously in Fukushima contaminated soil samples using thermal ionization mass spectrometry (TIMS). 234U, 235U and 236U isotopes were measured by Daly ion counting system whereas 238U was measured by Faraday collector using mass peak jumping method. Fukushima radio‑cesium contaminated soil samples were digested using microwave oven for complete decomposition. A combined AER-UTEVA separation scheme was applied for purification of U and its accurate isotope ratios measurement in Fukushima soils rich with Fe. Analytical validation of the modified U separation method was tested with certified reference material (CRM) JSd-2. The analytical precision (RSD%) of 234U/238U, 235U/238U and 236U/238U isotope ratios obtained by long-term repeatability for CRM NBL U010 was 0.288% (2σ), 0.017% (2σ) and 0.235% (2σ), respectively. Validation of accurate U isotope ratios measurement was checked with a CRM IRMM-184. This procedure was applied successfully to CRM JSd-2, SRM NIST 4354 and Fukushima soil samples. The concentration of 236U in Fukushima contaminated soils varied from 21.7–194.7 fg/g which showed the mixing effect of global fallout and Fukushima Dai-ichi Nuclear Power Station (FDNPS) accident fallout.

U-series and Sr isotopes as tracers of mineral weathering and water routing from the deep Critical Zone to streamflow in a high-elevation volcanic catchment

Tracing water routing and groundwater contribution to streamflow is a key tool for better understanding limited water resources. Measurements of U-series activity ratios and radiogenic Sr isotope ratios in drill cores, streams, and groundwater samples were employed to investigate weathering controls and better understand hydrologic flow paths and evolution through the heterogenous subsurface of a montane catchment. Situated within the semi-arid geologically complex volcanic setting of the Valles Caldera National Preserve in northern NM, this study focuses on streams draining the tallest (3432 masl) resurgent dome (Redondo Peak). Recent drilling of groundwater monitoring wells allowed for the collection and isotopic analysis of intact continuous cores and groundwater collected from similar depths, a unique and valuable contribution to U-series studies, within a high elevation headwater catchment focusing on two hillslopes with contrasting Critical Zone (CZ) structure and several distinct groundwater stores.U-series composition of core samples identified UTh fractionation from recent (< 1.25 Ma) disturbance in both hillslopes; however, (234U/238U) and (230Th/238U) disequilibria and 87Sr/86Sr values indicated more intense weathering and lithologic complexity in the hillslope underlain by volcanic breccia over vesicular tuff compared to the hillslope underlain by fractured tuff. The weathering profile of the site composed of breccia overlying vesicular tuff was influenced by the presence of shallow groundwater situated above deeper groundwater stores, which have distinctively higher (234U/238U) activity ratios and 87Sr/86Sr signatures than those of the deep groundwater stores in the fractured tuff site. The combination of U-series and Sr isotopes across time and in isotope mixing analysis highlights the utility of pairing these two isotope tracers that pinpoint distinct groundwater stores and help to isolate controls on U-series isotopes. Time series of U and Sr isotope signatures of groundwater and surface water suggest small seasonal changes in composition of streamflow while USr isotope mixing analysis suggests that deep groundwater from the fractured tuff aquifer system generates more than 90% of streamflow to the greater catchment whereas shallow groundwater and soil water contribute less than 10% to streamflow, primarily following spring snowmelt. Importantly, constraining streamflow sources using isotope mixing analysis highlights that deep groundwater from fractured bedrock within the CZ sustains streamflow here and emphasizes the need to consider deep groundwater in future studies of fractured bedrock systems.

Calibration Strategies for Detecting Macroscale Patterns in NEON Atmospheric Carbon Isotope Observations

AbstractCarbon fluxes in terrestrial ecosystems and their response to environmental change are a major source of uncertainty in the modern carbon cycle. The National Ecological Observatory Network (NEON) presents the opportunity to merge eddy covariance (EC)‐derived fluxes with CO2 isotope ratio measurements to gain insights into carbon cycle processes. Collected continuously and consistently across &gt;40 sites, NEON EC and isotope data facilitate novel integrative analyses. However, currently provisioned atmospheric isotope data are uncalibrated, greatly limiting ability to perform cross‐site analyses. Here, we present two approaches to calibrating NEON CO2 isotope ratios, along with an R package to calibrate NEON data. We find that calibrating CO2 isotopologues independently yields a lower δ13C bias (&lt;0.05‰) and higher precision (&lt;0.40‰) than directly correcting δ13C with linear regression (bias: &lt;0.11‰, precision: 0.42‰), but with slightly higher error and lower precision in calibrated CO2 mole fraction. The magnitude of the corrections to δ13C and CO2 mole fractions vary substantially by site, underscoring the need for users to apply a consistent calibration framework to data in the NEON archive. Post‐calibration data sets show that site mean annual δ13C correlates negatively with precipitation, temperature, and aridity, but positively with elevation. Forested and agricultural ecosystems exhibit larger gradients in CO2 and δ13C than other sites, particularly during the summer and at night. The overview and analysis tools developed here will facilitate cross‐site analysis using NEON data, provide a model for other continental‐scale observational networks, and enable new advances leveraging the isotope ratios of specific carbon fluxes.

다검출기 유도결합 플라즈마 질량분석기를 이용한 미량시료의 황 동위원소 분석

황은 다양한 생지구화학 반응에 전자 수용체 혹은 공여체로 참여하며, 그 과정에서 발생하는 안정 동위원소 비의 변화는 지구물질 순환을 이해하기 위한 도구로 폭넓게 이용된다. 황 동위원소 분석에는 기체 시료를 이용한 측정이 주류를 이뤄왔으나 최근 다검출기 유도결합 플라즈마 질량분석기(MC-ICP-MS)가 액상 혹은 고체상 미량시료 분석을 중심으로 주목받고 있는데, 현재까지 국내에서 관련 분석 사례는 보고되지 않았다. 이번 연구에서는 서울대학교 공동기기원에 운영 중인 MC-ICP-MS를 이용해 황 동위원소 분석을 수행하였다. 시료 내 황산이온은 음이온 교환수지를 이용해 분리하였으며, 분자이온의 교란효과를 줄이고자 탈용매화장치를 통해 MC-ICP-MS에 주입하였다. 황 동위원소는 질량간섭의 영향을 받지 않는 SSUP+/SUP 피크의 가벼운 질량 말단부에서 측정되었으며, 표준물질과 시료의 교차분석을 통한 보정이 이루어졌다. 자체 표준물질의 동위원소 조성은 IAEA-SO-5와 비교를 통해 결정하였고, 이를 이용해 측정한 IAEA-SO-6와 NBS-127의 동위원소 조성은 보고된 값과 오차범위 내에서 일치하였다. 이번 연구를 통해 확인한 δSUP34/SUPS와 ΔSUP33/SUPS 분석의 재현성은 각각 0.44‰과 0.52‰ 이하였으며, 최소 14 nmol의 황을 함유하고 있는 시료에서 안정적인 결과를 획득할 수 있었다. 미량시료의 황 동위원소 분석이 국내에서 가능해짐에 따라, 전통적인 분석을 위한 시료 확보에 어려움이 있었던 빙하나 미세먼지 등에 대한 국내 황 동위원소 연구가 활발해질 것으로 기대된다.

Carbonate Precipitation Methods for the Measurement of Stable Isotope Ratio of Dissolved Inorganic Carbon

Carbonate Precipitation Methods for the Measurement of Stable Isotope Ratio of Dissolved Inorganic Carbon

Large sulfur isotope fractionation in lunar volcanic glasses reveals the magmatic differentiation and degassing of the Moon.

Sulfur isotope variations in mantle-derived lavas provide important constraints on the evolution of planetary bodies. Here, we report the first in situ measurements of sulfur isotope ratios dissolved in primitive volcanic glasses and olivine-hosted melt inclusions recovered from the Moon by the Apollo 15 and 17 missions. The new data reveal large variations in 34S/32S ratios, which positively correlates with sulfur and titanium contents within and between the distinct compositional groups of volcanic glasses analyzed. Our results uncover several magmatic events that fractionated the primordial sulfur isotope composition of the Moon: the segregation of the lunar core and the crystallization of the lunar magma ocean, which led to the formation of the heterogeneous sources of the lunar magmatism, followed by magma degassing during generation, transport, and eruption of the lunar lavas. Whether the Earth's and Moon's interiors share a common 34S/32S ratio remains a matter of debate.

Development and verification of a novel isotopic N2 O measurement technique for discrete static chamber samples using cavity ring-down spectroscopy.

N2 O isotopomers are a useful tool to study soil N cycling processes. The reliability of such measurements requires a consistent set of international N2 O isotope reference materials to improve inter-laboratory and inter-instrument comparability and avoid reporting inaccurate results. All these are the more important given the role of N2 O in anthropogenic climate change and the pressing need to develop our understanding of soil N cycling and N2 O emission to mitigate such emissions. Cavity ring-down spectroscopy (CRDS) could potentially overcome resource requirements and technical challenges, making N2 O isotopomer measurements more feasible and less expensive than previous approaches (e.g., gas chromatography [GC] and isotope ratio mass spectrometry [IRMS]). A combined laser spectrometer and small sample isotope module (CRDS & SSIM) method enabled N2 O concentration, δ15 Nbulk , δ15 Nα , δ15 Nβ and site preference (SP) measurements of sample volumes <20 mL, such as static chamber samples. Sample dilution and isotopic mixing as well as N2 O concentration dependence were corrected numerically. A two-point calibration procedure normalised δ values to the international isotope-ratio scales. The CRDS & SSIM repeatability was determined using a reference gas (Ref Gas). CRDS & SSIM concentration measurements were compared with those obtained by GC, and the isotope ratio measurements from two different mass spectrometers were compared. The repeatability (mean ± 1σ; n = 10) of the CRDS & SSIM measurements of the Ref Gas was 710.64 ppb (± 8.64), 2.82‰ (± 0.91), 5.41‰ (± 2.00), 0.23‰ (± 0.22) and 5.18‰ (± 2.18) for N2 O concentration, δ15 Nbulk , δ15 Nα , δ15 Nβ and SP, respectively. The CRDS & SSIM concentration measurements were strongly correlated with GC (r = 0.99), and they were more precise than those obtained using GC except when the N2 O concentrations exceeded the specified operating range. Normalising CRDS & SSIM δ values to the international isotope-ratio scales using isotopic N2 O standards (AK1 and Mix1) produced accurate results when the samples were bracketed within the range of the δ values of the standards. The CRDS & SSIM δ15 Nbulk and SP precision was approximately one order of magnitude less than the typical IRMS precision. CRDS & SSIM is a promising approach that enables N2 O concentrations and isotope ratios to be measured by CRDS for samples <20 mL. The CRDS & SSIM repeatability makes this approach suitable for N2 O "isotopomer mapping" to distinguish dominant source pathways, such as nitrification and denitrification, and requires less extensive lab resources than the traditionally used GC/IRMS. Current study limitations highlighted potential improvements for future users of this approach to consider, such as automation and physical removal of interfering trace gases before sample analysis.