Stable Isotope Ratio Mass Spectrometer Research Articles

Mineralogical Characteristics Study of Calcite from the Fujian Province, China

With mineral in situ testing technology and ore deposit geochemistry development, calcite has become a hot topic in studying carbonate minerals. Four large-grain calcite crystals from Fujian, China, were used for a detailed study. This study provides a comprehensive data set through mineralogical standard properties and spectral characteristics, including Fourier transform infrared, X-ray fluorescence spectrum, and Raman spectroscopy. Major elements were analyzed using X-ray fluorescence (XRF) and Micro-XRF. A high-resolution gas-source stable isotope ratio mass spectrometer was used to test C-O isotope characteristics. The four samples’ spectral characteristics and phase composition show excellent uniformity, all with the same characteristic peaks, indicating that they are pure calcite without other impurity minerals. C-O isotope characteristics indicate that Fujian calcite has mantle genetic characteristics, which may be affected by marine carbonate dissolution or sedimentary rock contamination. The variation of Fe and Mn contents may indicate that the four samples formed at different metallogenic stages.

Contribution of Spring Snowmelt Water to Soil Water in Northeast China and Its Dynamic Changes

Snowmelt water in spring is an important source of soil water, which is critical to supporting crop growth. Quantifying the contribution of snowmelt water to soil water and its dynamic changes is essential for evaluating soil moisture and allocating agricultural water resources. In this paper, through controlled outdoor experiments, different snow depths and soil depth gradients were set; and snow, precipitation, and soil samples were collected regularly. To analyze the contribution of snowmelt water to soil water and its dynamic changes, the MAT-253 stable isotope ratio mass spectrometer was adopted for hydrogen and oxygen isotope analyses. The results showed that the snowmelt water for snow depths of 10 cm, 30 cm, and 50 cm all contributed to the 0–30 cm soil layer. The contribution increased with soil depth, contributing 8.13%, 8.55%, and 11.24%, respectively. The contribution of the snow cover at the same depth to the soil moisture at different depths also varied, i.e., the contribution increased with increasing soil depth. The snowmelt water retention time at depths of 10 cm, 30 cm, and 50 cm was inconsistent, i.e., it was the longest at 0–10 cm (average of 69 days), followed by 20–30 cm (average of 59 days), and the shortest at 10–20 cm (average of 54 days). The greater the snow depth, the shorter the retention time of the snowmelt water in the different soil layers. For surface soil, the contribution of the snowmelt water at greater depths was significantly different; while for deep soil, the contribution was more sensitive to the snow depth. Regardless of snow depth, soil contributions at different depths were significantly different. Precipitation also affected the contribution of the snowmelt water to the soil water, exhibiting different effects at different depths.

Authentication of Geographical Origin in Hainan Partridge Tea (Mallotus obongifolius) by Stable Isotope and Targeted Metabolomics Combined with Chemometrics.

Partridge tea (Mallotus oblongifolius (Miq.) Müll.Arg.) is a local characteristic tea in Hainan, the southernmost province of China, and the quality of partridge tea may be affected by the producing areas. In this study, stable isotope and targeted metabolomics combined chemometrics were used as potential tools for analyzing and identifying partridge tea from different origins. Elemental analysis—stable isotope ratio mass spectrometer and liquid chromatography-tandem mass spectrometrywas used to analyze the characteristics of C/N/O/H stable isotopes and 54 chemical components, including polyphenols and alkaloids in partridge tea samples from four regions in Hainan (Wanning, Wenchang, Sanya and Baoting). The results showed that there were significant differences in the stable isotope ratios and polyphenol and alkaloid contents of partridge tea from different origins, and both could accurately classify partridge tea from different origins. The correct separation and clustering of the samples were observed by principal component analysis and the cross-validated Q2 values by orthogonal partial least squares discriminant analysis (OPLS-DA) were 0.949 (based on stable isotope) and 0.974 (based on polyphenol and alkaloid), respectively. Potential significance indicators for origin identification were screened out by OPLS-DA and random forest algorithm, including three stable isotopes (δ13C, δ D, and δ18O) and four polyphenols (luteolin, protocatechuic acid, astragalin, and naringenin). This study can provide a preliminary guide for the origin identification of Hainan partridge tea.

The preparation and characterization of chemically deuterium incorporated cotton fibers

Preparation of deuterium incorporated cellulose is a vital tool to investigate cellulose internal structure and to expand the application fields of cellulose materials. In this study, cellulosic cotton fibers with anti-rehydration (exchange-resistant) deuterium incorporated in cellulose were prepared by chemical hydrogen–deuterium exchange treatment. The chemical hydrogen–deuterium exchange process, along with exchange time, were characterized by nuclear magnetic resonance hydrogen spectroscopy (1H-NMR). The anti-rehydration deuterium incorporation was determined by Fourier Transform infrared spectroscopy (FTIR) and Stable Isotope Ratio Mass Spectrometer (IRSM). The effect of the deuterium hydroxyl substitution on cotton fiber’s spectral data, microstructure, crystalline information, degree of polymerization, as well as it’s thermogravimetric analysis (charcoalization and combustion) are explored. Analysis of the chemical exchange process indicated that the hydrogen–deuterium exchange occurred preferentially in the amorphous cellulose component over the first several minutes. Deuterium exchange in the anti-rehydration crystalline phase took several hours. Increasing the treatment time, enhanced exchange-resistant deuterium incorporation to as high as about 60% of the cotton fibers’ cellulose hydroxyl groups was achieved. The characterization of FTIR, Fourier transform Raman (FT-Raman), and near-infrared spectra (NIR) all exhibited the deuterium spectral isotope effect on cellulose hydroxl groups. While, apart from the effect of reaction temperature, deuterium incorporation isotope effect did not affect the cellulose microstructure, crystalline index and the degree of polymerization properties. Furthermore, the thermogravimetric analysis of deuterated cotton fibers under N2 and air atmosphere were both altered due to the thermodynamic isotope effect. These observations revealed the hydrogen–deuterium exchange treatment process and impacts on cellulose fiber properties, which helped us to better understand the cellulose internal structure and may facilitate the potential utilization of deuterated cellulosic materials.

Chemometric Discrimination of the Geographical Origin of Three Greek Cultivars of Olive Oils by Stable Isotope Ratio Analysis.

Α stable isotope ratio mass spectrometer was used for stable isotope ratio (i.e., δ13C, δ18O, and δ2H) measurements, achieving geographical discrimination using orthogonal projections to latent structures discriminant analysis. A total of 100 Greek monovarietal olive oil samples from three different olive cultivars (cv. Koroneiki, cv. Lianolia Kerkyras, and cv. Maurolia), derived from Central Greece and Peloponnese, were collected during the 2019–2020 harvest year aiming to investigate the effect of botanical and geographical origin on their discrimination through isotopic data. The selection of these samples was made from traditionally olive-growing areas in which no significant research has been done so far. Samples were discriminated mainly by olive cultivar and, partially, by geographical origin, which is congruent with other authors. Based on this model, correct recognition of 93.75% in the training samples and correct prediction of 100% in the test set were achieved. The overall correct classification of the model was 91%. The predictability based on the externally validated method of discrimination was good (Q2 (cum) = 0.681) and illustrated that δ18O and δ2H were the most important isotope markers for the discrimination of olive oil samples. The authenticity of olive oil based on the examined olive varieties can be determined using this technique.

Determination of 17O Anomaly in Atmospheric Aerosol Nitrate

通过改造稳定同位素比质谱仪外设设备、优化系统参数、优化细菌反硝化方法等方法，建立了一种高灵敏度高精度的大气气溶胶硝酸盐氧同位素异常值快速测定方法。本方法的检出限为0.4 μg N，在最佳进样量为0.8 μg N时，测定精度可达到0.19‰。 A novel method for rapid determination of oxygen isotope anomaly (Δ 17 O) in atmospheric aerosol samples was developed. With this method, the measurement was completed in 15 min with a relatively high analytical precision and a low determination limit. To achieve an analytical precision of 0.6‰, this method required a minimum nitrate content of 29 nmol (0.4 μg N). The analytical precision was optimum with a nitrate content of 57 nmol (0.8 μg N). The nitrate in atmospheric aerosol samples was converted to nitrous oxide by optimized bacterial denitrification process within 4 hs. After that, a thermal decomposition of nitrous oxide in sample gas was carried out in a gold tube at 800 °C after separation and purification, followed by gas chromatographic separation and isotope analysis of oxygen. The experiment results showed that the analytical precision of Δ 17 O in this method could reach 0.19‰ with a sample content of 57 nmol NO 3 − , and the analytical precision of δ 15 N could reach 0.15‰. This method was not only suitable for oxygen isotope anomaly determination in atmospheric aerosol samples, but also for the other atmospheric environmental samples such as rain and snow samples with low concentrations. This research establishes a rapid determination method which can determinate the 17 O anomaly in atmospheric aerosol samples by transforming the peripheral equipment of stable isotope ratio mass spectrometer, optimizing the system parameters and the bacterial anti-nitrification method. This method requires a minimum of 0.4 μg N, and analytical precision could reach 0.19 ‰ at a sample content of 0.8 μg N.

Geographical origin traceability and identification of refined sugar using UPLC-QTof-MS analysis

Authentication of geographical origin is essential to the food safety of refined sugar. This study aimed to determine the geographical origin traceability and authenticity of refined sugar in China. Ultra performance liquid chromatography-quadrupole time-of-flight Mass Spectrometry (UPLC-QTof-MS), instead of conventional stable isotope ratio mass spectrometer (IRMS), was used to detect the mass fragment ratios (Rδ-sucrose and Rδ-glucose) of refined sugar. These ratios could reflect the cultivation practice and environmental conditions. A total of 108 batches of samples were collected from six regions in China, and additional 72 samples were verified with support vector machines (SVM) model, in order to evaluate the accuracy of origin identification and composition prediction. Our results showed that 83.3% of the refined sugar was correctly classified based on the geographical region of origin under different environmental conditions. These findings indicate that the specified mass fragment ratio may be a promising approach for assessing the traceability and authenticity of refined sugar.

C/N/H/O stable isotope analysis for determining the geographical origin of American ginseng (Panax quinquefolius)

A total of 44 root samples of American ginseng (Panax quinquefolius) originating from five different geographical areas (America = 6, Canada = 10, Beijing = 8, Jilin = 8, and Shandong = 12) were collected from specialty wholesalers in China. The C/N/H/O stable isotope ratios were determined using an elemental analyzer coupled with a stable isotope ratio mass spectrometer. Our results revealed that a single variable was unable to clearly discriminate between the various geographical origins of American ginseng, whereas the combination of δ18O and δ15N and the combination of δ13C, δ15N, and δ18O provided useful information for the identification of American ginseng from the five regions. Moreover, the application of different multivariate statistical approaches, including the one-way analysis of variance and linear discriminant analysis (LDA), to further explore the ability of C/N/H/O stable isotopes for determining the geographical origins of American ginseng identified a significant difference (P < 0.05) in the stable isotope ratios from different regions, and high recognition (90.9 %) and satisfactory predictive ability (86.4 %) were achieved with the LDA. The present findings suggest that the C/N/H/O stable isotopes can be potentially applied in the authentication of different geographical origins of American ginseng.

Stable carbon isotope diagnostics of mammalian metabolism, a high-resolution isotomics approach using amino acid carboxyl groups.

The carbon isotopic compositions of amino acids are increasingly measured to characterize diets and metabolic response to diets. We report a new high-resolution system to measure the stable carbon isotopic composition of carboxyl atoms within amino acids. The automated system used HPLC to separate amino acids followed by addition of ninhydrin for decarboxylation and transfer of the evolved CO2 to a stable isotope ratio mass spectrometer for δ13CCARBOXYL measurement. The ninhydrin reaction was conducted at acidic pH (1.5) and elevated temperature (160 oC) giving yields close to 100% for most common amino acids. Eight mammalian keratin samples from herbivores (kudu and caribou), omnivores (humans) and carnivores (bowhead and humpback zooplanktivorous whales) were analysed with this new system. The data provide an initial calibration of reference materials to be used in studies of this type and is the first report of carboxyl carbon isotope distributions in mammals. Results showed widespread 13C enrichments in both essential and non-essential amino acid carboxyl groups, likely linked to decarboxylation of amino acids during normal metabolism. Analyses of non-essential amino acid isotope profiles showed (1) consistent and general taxon-level metabolic differences between the herbivore, human and whale samples, (2) marked differences among individual humans, ruminants and whales (3) evidence for gluconeogenesis in the wildlife samples, and (4) extensive 13C enrichment likely associated with fasting in the humpback whale sample. Future mammalian research related to the metabolism of growth, reproduction, aging and disease may benefit from using this technique. Values obtained for internationally available samples USGS42 and USGS43 (Tibetan and Indian human hair) provide a first characterization of reference materials for δ13CCARBOXYL profiles.

A case study for geographical indication of organic milk in Korea using stable isotope ratios-based chemometric analysis

This study aimed to examine regional δ13C, δ15N, δ18O, and δ34S variations of organic milk in Korea and to develop a differentiation model to identify isotope markers. Herein, δ13C, δ15N, δ18O, and δ34S were quantified in organic milk, using a stable isotope ratio mass spectrometer and developed differentiation models through pairwise comparisons using orthogonal projection to latent structure-discriminant analysis, which displayed excellent predictability (Q2cum ≥ 0.828) among Boryeong, Gochang, and Jeju regions and good predictability (Q2cum ≥ 0.503) for Hoengseong-related regions. The δ13C value was the most important influencer, and the prediction plots by an external validation among Boryeong, Gochang, and Jeju regions accurately predicted the geographical origin of the test milk samples with below 5% of probability of wrong classification. Our results show regional δ13C, δ15N, δ18O, and δ34S signatures in Korea, thereby potentially expanding global isotope ratio databases for reliable geographical indication of organic milk.

Potential geo-discriminative tools to trace the origins of the dried slices of shiitake (Lentinula edodes) using stable isotope ratios and OPLS-DA

The Lentinus edodes species, known as shiitake, has a history of extensive use in many cuisines in several East Asian countries owing to its unique and pleasant flavor and texture. As international food trade increases, reliable discrimination of geographical origin is becoming increasingly crucial in Korea to identify cheaper imported Chinese shiitake. Herein, stable isotope ratios (i.e., δ13C, δ15N, δ18O, and δ34S) were measured with a stable isotope ratio mass spectrometer, and a geographical discrimination method using orthogonal projection to latent structure-discriminant analysis was developed. The externally validated discrimination method showed excellent predictability (Q2cum = 0.881) and illustrated that δ18O and δ15N were important isotope markers for the geographical discrimination of dried shiitake slices. This study extends the knowledge of geographical differences between China and Korea evidenced by the shiitake isotope signatures, thereby contributing to potential geographical authentication with broader applications for international shiitake markets.

Measurement of 18 O18 O and 17 O18 O in atmospheric O2 using the 253 Ultra mass spectrometer and applications to stratospheric and tropospheric air samples.

RationaleThe doubly substituted isotopologues (e.g., 18O18O, 17O18O) in atmospheric O2 are potential tracers for ozone photochemistry and atmospheric temperatures. Their low abundances and isobaric interference are the major analytical challenges. The 253 Ultra high‐resolution stable isotope ratio mass spectrometer is suitable for resolving isobaric interferences.MethodsO2 from air is purified using gas chromatography on a packed column filled with molecular sieve 5 Å and cooled to −78°C. The δ17O, δ18O, Δ17O, Δ35 and Δ36 values are measured on the extracted O2 with the 253 Ultra at medium mass resolution (M/ΔM ~10000) using Faraday detectors for the singly substituted isotopologues and ion counters for the doubly substituted isotopologues.ResultsInterferences from isobars, mainly 35Cl for 17O18O and H35Cl and 36Ar for 18O18O, are sufficiently resolved to enable high‐precision determination of Δ35 and Δ36. The Δ35 and Δ36 values of O2 after photochemical isotope equilibration at −63°C and heating to 850°C agree with the theoretical prediction. The stratospheric Δ35 and Δ36 values are close to isotopic equilibrium at the ambient temperatures. However, the values for tropospheric O2 differ from those expected at equilibrium.ConclusionsThe 253 Ultra allows interference‐free clumped isotope measurements of O2 at medium mass resolution. The Δ35 and Δ36 signatures in atmospheric O2 are mainly governed by O3 photochemistry, temperature and atmospheric transport. Tropospheric O2 is isotopically well mixed and retains a significant stratospheric signature.

Regional discrimination of Agaricus bisporus mushroom using the natural stable isotope ratios

This study was aimed to verify the regional traceability of Agaricus bisporus mushroom using unique δ13C, δ15N, δ18O, and δ34S features combined with chemometric approaches. Ten cultivars from 15 mushroom farms in six regions of Korea were measured their isotopic signatures by stable isotope ratio mass spectrometer. The δ13C, δ15N, δ18O, and δ34S values were significantly different among mushrooms collected from six cultivation regions (P < 0.05). Multi-dimensional plots including the δ15N and δ34S values demonstrated clear regional discrimination of the Saedo and Saehan cultivars produced from Buyeo, Nonsan, Eumseong, Boryeong, or Gyeongju. Partial least-squares discriminate analysis models showed good discrimination for Saedo (Rx2 = 0.798 and Q2 = 0.563) and Saehan (Rx2 = 0.819 and Q2 = 0.894). These preliminary results can extend knowledge of regional isotope signatures in A. bisporus mushroom produced in Korea, contributing to accurate geographical authenticity with potential broader applications for the international mushroom market.

Measurements and modeling of 16O12C17O spectroscopic parameters at 2 µm

The lack of spectroscopic measurements for rare CO2 isotopologues was the main motivation of this work. In our present study we report line intensity measurements for 16O12C17O made with a high resolution Fourier transform spectrometer (Bruker IFS-125HR) and a 21 m path cryogenic Herriott cell at Jet Propulsion Laboratory. For this, a 17O-enriched CO2 gas sample was used, which comes as a mixture of primary and several minor CO2 isotopologues. The mole fraction of the 16O12C17O isotopologue in the mixture was determined to be 0.3991 by mass spectrometry from a Stable Isotope Ratio Mass Spectrometer (SIRMS) under stochastic distribution assumption at thermal equilibrium. Since the collisional narrowing effect was observed, the Rautian molecular line shape profile was systematically adopted instead of the Voigt profile. Absolute line positions were also investigated by performing a wavenumber calibration based on CO, HCl and a few well-known 16O12C16O transitions. Finally, around 1000 transitions were studied between 4604 and 5126cm−1 involving 15 bands of the 16O12C17O isotopologue. All the measured line intensities were renormalized to be the values for 100% pure isotopologue sample. Transition dipole moments and Herman-Wallis factors were derived enabling a global comparison with theoretical calculations and predictions for the 15 bands of the 16O12C17O isotopologue. For the measured line positions, the absolute accuracy is around 2×10−4cm−1. The accuracies of retrieved line intensities are 2 – 5% for five cold and two hot bands, and 6–30% for eight other weaker hot bands. Results from this work were in a good agreement with HITRAN 2012 for positions, but showed rather significant discrepancies for line intensities. An extensive line list was generated from new experimental measurements in order to improve and validate spectroscopic knowledge of 12C16O17O isotopologue in support of atmospheric remote sensing for the Earth (e.g., OCO-2 mission), Mars and Venus.

Stable Carbon Isotope Ratio (δ13C) Measurement of Graphite Using EA-IRMS System

δ 13 C values in non-irradiated natural graphite were measured. The measurements were carried out using an elemental analyzer combined with stable isotope ratio mass spectrometer (EA-IRMS). The samples were prepared with ground and non-ground graphite, the part of which was mixed with Mg (ClO 4 ) 2 . The best combustion of graphite in the oxidation furnace of the elemental analyzer was achieved when the amount of pulverized graphite ranged from 200 to 490 µg and the mass ratio C:Mg(ClO 4 ) 2 was approximately 1:10. The method for the graphite burning avoiding the isotope fractionation is proposed. DOI: http://dx.doi.org/10.5755/j01.ms.21.2.6873

A Laser Based Fluorination (BrF5) System for the Extraction of Oxygen (O2) from Silicate Rocks of Himalaya and δ18O Measurements: Method Establishment and Implications

Oxygen forms the majority of minerals constituting the terrestrial and planetary objects. Its chemical and isotopic compositions often bear signatures of the processes occurring within these objects on different time scales. Silicates are the common rocks in the Himalaya, the major feature on the Earth, which has witnessed different stages of metamorphism and got reworked during its evolution. Therefore, oxygen isotopes in silicate rocks can be used to reveal the processes pertaining to the Himalayan orogeny. These processes include petrogenesis, metamorphism, subduction and associated magmatic events, etc. Oxygen isotopic composition (δ18O) is needed to be measured in silicate rocks which require special arrangements. Towards this, a vacuum line of stainless steel coupled with a computer controlled CO2 laser system was fabricated, for the first time in India, to extract oxygen (O2) from rock forming mineral in the BrF5 environment. The line is equipped with suitable valves and traps for the efficient recovery of oxygen from the silicate minerals and reliable handling of hazardous oxidants (i.e., BrF5, etc.) that are used as fluorination agents to break Si=O bonds. This extraction system is interfaced with a continuous flow stable isotope ratio mass spectrometer and is being used successfully for the oxygen isotopic (δ18O) measurements in silicate and oxide minerals. Here we report the δ18O results on a set of silicate rocks and standard reference materials including Norway olivine, Gee Whiz Garnet standard from University of New Mexico, olivine from Norway Fan (Lab Standard), silicate rocks from North West Himalaya (India) and NBS-28 quartz a standard reference material from International Atomic Energy Agency, Vienna. The average δ18O values (relative to Vienna standard mean ocean water) and 2SD are 6.4 ± 0.3 ‰ (N = 17) for Norway olivine, 12.7 ± 0.2 ‰ (N = 10) for Gee Whiz Garnet and 9.5 ± 0.3 ‰ (N = 12) for NBS-28 quartz. In addition, some of the quartz vein and quartzites from the Garhwal Himalaya were also measured to establish the measurement protocols and procedures. Silicate rocks from the Himalaya near the main central thrust zone were tried to fix the end-member composition for oxygen isotopes (δ18O). Such information is helpful to infer about the origin of quartzite and their relationship with possible protoliths in the region. Further, this technique finds applications in the analysis of biogenic silica (diatoms and phytoliths, etc.) for paleoclimatic reconstruction.

Large-scale plant growth chamber design for elevated pCO2 and δ13C studies.

Throughout at least the next century, CO(2) fertilization and environmental stresses (e.g. nutrient, moisture, insect herbivory) are predicted to affect yields of economically important crop species. Stable isotopes of carbon are used to study plant stresses, which affect yields, but a growth chamber design that can be used to isolate the effects of environmental stresses on crop-sized species through precise maintenance of pCO(2) levels and the δ(13)C values of atmospheric CO(2) (δ(13) C(CO2)) is lacking. We designed and built low-cost plant growth chambers for growing staple crop species under precise pCO(2) and δ(13) C(CO2) conditions. Over the course of 14 hours, we assessed for pCO(2) stability at two targeted levels (ambient, ~400 ppm; and 2×, ~800 ppm) and measured the δ(13) C(CO2) value within the two chambers using a stable isotope ratio mass spectrometer. We also compared the temperature and relative humidity conditions within the two growth chambers, and in the ambient, outside air. Across our experimental period, we achieved δ(13) C(CO2) stability (ambient: -8.05 ± 0.17‰; elevated: -12.99 ± 0.29‰) that showed nearly half the variability of any previously reported values for other chamber designs. The stability of the pCO(2) conditions (ambient: 406 ± 3 ppm; elevated: 793 ± 54 ppm) was comparable with that in previous studies, but our design provided ~8 times more growing space than previous chamber designs. We also measured nearly identical temperature and relative humidity conditions for the two chambers throughout the experiment. Our growth chamber design marks a significant improvement in our ability to test for plant stress across a range of future pCO(2) scenarios. Through significant improvement in δ(13) C(CO2) stability and increased chamber size, small changes in carbon isotope fractionation can be used to assess stress in crop species under specific environmental (temperature, relative humidity, pCO(2)) conditions.

Experimental Setup and Standardization of a Continuous Flow Stable Isotope Mass Spectrometer for Measuring Stable Isotopes of Carbon, Nitrogen and Sulfur in Environmental Samples

We present here the experimental setup and standardization of a newly acquired stable isotope ratio mass-spectrometer (Isoprime 100, Isoprime® UK) coupled with elemental analyzer (Pyrocube, Elementar®-Germany) in a continuous flow mode, for the measurements of C, N and S isotopes in a variety of natural as well as synthetic organics and sulfur containing solid samples. We have calibrated our instrument using a suite of certified international standards supplied by International Atomic Energy Agency Vienna and cross-checked against several in-house laboratory standards used by other institutions of international repute. A synthetic organic compound Sulfanilamide was continuously used along with international standards to develop an in-house internal laboratory standard for the accurate and precise isotopic measurements. Important components contributing to the overall uncertainty of the isotopic measurements such as blank contributions, amount effect and response of mass-spectrometric current against thermal conductivity detector were performed using several aliquots of ε-Amino-n-caproic acid and sulfanilamide (in-house) standards. Both short and long term variabilities in the measure isotopic data were assessed using our in-house laboratory standard Sulfanilamide. Overall estimated uncertainties of C, N and S isotopic measurements are better than 0.2, 0.2 and 0.3 ‰, respectively; which are well within the recommended limits of aforementioned isotopic data.

Growth-rate induced disequilibrium of oxygen isotopes in aragonite: An in situ study

Oxygen isotope compositions (δ18O) of biogenic and inorganically precipitated calcium carbonate minerals are being used to reveal marine and terrestrial temperatures from the past. However, experimental and natural observations show factors other than temperature control δ18O in CaCO3via disequilibrium fractionation. Crystallization rate is among these factors, and therefore, its effect on fractionation process has been studied during the last 30years. However, most previous experimental assessments measured δ18O in polycrystalline precipitates using bulk analytical techniques and defined growth rate as the total amount of CaCO3 crystallized during the period of time. Because of this, inter- and intra-crystal isotopic variability has remained poorly constrained. In order to evaluate the effect of crystal extension rate (V) on 18O fractionation between aragonite and fluid an alternative analytical approach was used. Hemispherical bundles of aragonite crystals (spherulites) were measured for δ18O in situ with Secondary Ion Mass Spectrometry (SIMS) at lateral spatial resolution of 10–20μm. The change in V over time was monitored by addition of multiple rare earth element (REE) spikes into the fluid from which the aragonite grew. δ18O in fluid was analyzed with stable isotope ratio mass spectrometer. Results show a decrease in the oxygen isotope fractionation factor (α18O) by 2.4‰ with increasing growth rate of aragonite spherulites from 0.064 to 0.88nm/s (5.5–76μm/day). Crystal growth rate is therefore potentially an important consideration when using δ18O in natural carbonates as a proxy for ocean and terrestrial climate. Growth entrapment model (GEM) was applied to explain experimentally determined α18O-V relationships, assuming lattice-fluid equilibrium α18O values (0% of growth entrapment) at slow growth rates and complete disequilibrium fractionation (100% of growth entrapment) during fast crystallization. Although V values obtained experimentally do not fully cover the V range used in GEM, the combination of experiment and simulations suggests depletion of 18O in the near-surface region of aragonite relative to the bulk crystal lattice. This 18O-depleted zone can be “captured” during rapid (non-equilibrium) crystal growth.

환상박피 처리에 의한 일본잎갈나무의 착과유도 효과와 질소 화합물 함량의 증가

낙엽송(Larix kaempferi) 채종원의 종자생산을 증진하기 위하여 접목 32년생의 채종목에 환상박피 처리를 하였다. 환상박피처리에 의하여 무처리보다 4배에 이르는 착과량 증가 효과가 있어 환상박피 처리의 효과가 뚜렷하게 나타났다. 환상박피 처리에 의한 낙엽송 주간 수피조직내의 대사물질의 변화를 IR-MS, GC-MS 및 HPLC로 분석하여 무처리와 비교한 결과 전질소 함량, sucrose 함량 및 전체 유리 아미노산의 함량이 무처리에 비해 유의적(p<0.05)으로 증가되었다. 또한 유리아미노산의 경우 화아원기가 형성되는 8월의 aspartic acid, glutamic acd, glycine, serine, cysteine, threonine 및 alanine이 환상박피 처리에서 무처리에 비해 유의적으로 높게 함유된 것으로 나타났다. 대사물질과 착과량간에 상관관계를 분석한 결과 착과량과 수피조직내의 전질소 함량(r=0.765, p<0.01)과 전체 유리 아미노산 함량(r=0.802, p<0.01)간에 고도의 정의 상관관계가 있었다. 특히, 화아원기 형성기인 7월 및 8월의 수피조직내의 aspartic acid, glutamic acd, glycine, serine 및 cysteine이 착과량과 정의 상관관계(p<0.05)가 있어, 아미노산의 질소화합물 인자가 낙엽송 화아원기 유도에 직, 간접적으로 관련이 있을 것으로 추정되었다. Japanese larch (Larix leptolepis) has been extensively planted in Korea as a reforestation species but their supply has been a major bottleneck due to sporadic natural seed production. In this study, stem girdling was applied to 32-year-old grafted Japanese larches, resulting in significantly enhanced seed production compared to the controls. Stem girdling induced about 4 times higher cone production than that of controls in the Japanese larch seed orchard. Time-dependent metabolic alterations after girdling were investigated by stable isotope ratio mass spectrometer, HPLC, and GC-MS analysis. In girdled trees, the contents of total nitrogen, sucrose, and total free amino acids were significantly higher than the non-girdled trees at the flowering differentiation season (from July to August). Moreover, the numbers of female strobilus per tree were positively correlated with the contents of both total nitrogen (r=0.765, p<0.01) and total amino acids (r=0.802, p<0.01) in the bark being collected at the flowering differentiation time (August 20). Interestingly, the levels of various individual amino acids at the flowering differentiation times, such as aspartic acid, glutamic acid, glycine, serine, and cysteine, were also significantly correlated (p<0.05) with the numbers of strobilus, suggesting that those amino acids might be involved in the induction of female strobilus formation of Japanese larches.