First real-time measurement of the evolving 2H/1H ratio during water evaporation from plant leaves

We have studied the temporal behaviour of the deuterium isotope ratio of water vapour emerging from a freshly cut plant leaf placed in a dry nitrogen atmosphere. The leaf material was placed directly inside the sample gas cell of the stable isotope ratio infrared spectrometer. At the reduced pressure (～40 mbar) inside the cell, the appearance of water evaporating from the leaf is easily probed by the spectrometer, as well as the evolving isotope ratios, with a precision of about 1 ‰. The demonstration experiment we describe measures the ²H/¹H isotope ratio only, but the experiment can be easily extended to include the ¹⁸O/¹⁶O and ¹⁷O/¹⁶O isotope ratios. Plant leaf water isotope ratios provide important information towards quantification of the different components in the ecosystem water and carbon dioxide exchange.     

Using the 13C/12C carbon isotope ratio to characterise the emission sources of airborne particulate matter: a review of literature

ABSTRACT

Particulate matter (PM) from atmospheric aerosols contains carbons that are harmful for living organisms and the environment. PM can originate from vehicle emissions, wearing of vehicle components, and dust. Size and composition determine PM transport and penetration depth into the respiratory system. Understanding PM emission characteristics is essential for developing strategies to improve air quality. The number of studies on carbon isotope composition (¹³C/¹²C) of PM samples to characterise emission factors has increased. The goal of this review is to integrate and interpret the findings from ¹³C/¹²C carbon isotope ratio (δ¹³C, ‰) analyses for the most common types of emission sources. The review integrates data from 25 studies in 13 countries. The range of δ¹³C of PM from vehicle emissions was from ?28.3 to ?24.5?‰ and for non-vehicle anthropogenic emissions from ?27.4 to ?23.3?‰. In contrast, PM ranges for δ¹³C from biomass burning sources differed markedly. For C₃ plants, δ¹³C ranged from ?34.7 to ?25.4?‰ and for C₄ plants from ?22.2 to ?13.0?‰. The ¹³C/¹²C isotope analysis of PM is valuable for understanding the sources of pollutants and distinguishing vehicle emissions from biomass burning. However, additional markers are needed to further distinguish other anthropogenic sources.     

PreCon: A Fully Automated Interface for the Pre-Gc Concentration of Trace Gases on Air for Isotopic Analysis

Abstract

For the high precision isotope analysis of atmospheric trace gases a computer controlled concentration interface has been developed. From small air samples it collects either N₂O or CO₂ derived from CH₄ at their respective concentrations (0.3 ppm for N₂O, 1.7 ppm for CH₄) into a small diameter cold trap (?196°C) and interfaces via GC and open split to an isotope ratio mass spectrometer (Finnigan MAT 252) for on-line isotope evaluation. External reproducibilities for repeated measurements of 100 ml air samples from the same source of < 0.2° (δ-notation) have been achieved for ¹³C/¹²C from CH₄ and for ¹⁵N/¹⁴N and ¹⁸O/¹⁶O from N₂O. The precision is adequate to monitor the isotopic changes in these gases during a day's course.     

Isotopengeochemische Charakterisierung kohlenwasserstoffbildender organischer Substanzen

Within the framework of a larger research project on contributions of isotope investigations to natural gas and crude oil exploration, the following publication is a first part of research reports from the author's laboratory.

The isotopic composition of carbon in fossil organic matter is primarily determined by the type of biological precursors. The main constituents forming organic matter in sediments are higher plants and microorganisms (algae, bacteria). These precursors contain a great number of organic compounds with corresponding isotope signatures. Hydrocarbons and lignin e.g., are enriched in carbon 13, while lipids in most cases are depleted.

Semi-empirical calculations on a thermodynamic basis are used to precalculate isotopic compositions of components or single compounds, applying the so-called β-factor method. The results are compared with numerous data from references about isotopic compositions of higher plants, algae and plant components. Also environmental conditions of plant growing-including paleoenvironment-have been taken into consideration.

The δ¹³C values of more than 150 types of organic substances in sediments of several geological formations have been measured in our isotope geochemical department.

The results allow a characterization and classification of organic matter: humic and sapropelitic organic substances can in many cases be distinguished by their isotopic signatures taking into account exceptions of e.g., regional origins. Influences of maturity (characterized by vitrinite reflectance) and especially of macerale composition of organic matter on it's isotope values and on the formation of hydrocarbons including their isotopic compositions are elucidated. The interpretation concept is also assured using special examples of drilling sites in Germany. The obtained results and proposed interpretation concept can contribute to further development in the understanding of hydrocarbon formation and natural gas exploration.     

1H and 13C NMR Spectral Study of Some 2r-Aryl-6c-phenylthian-4-ones,Their 1-Oxides and 1,1-Dioxides

ABSTRACT

Four 2r-aryl-6c-phenylthian-4-ones 1b?1e and their 1-oxides 2b?2e and 1,1-dioxides 3b?3e have been newly synthesized. ¹H and ¹³C NMR spectra have been recorded for all these compounds and 2r,6c-diphenylthian-4-one 1-oxide 2a. ¹³C NMR spectrum has been recorded for the sulfone 3a of 1a. For selected compounds ¹H-¹H COSY, HSQC, HMBC, and NOESY spectra have been recorded. The vicinal proton–proton coupling constants suggest that in all these compounds, the heterocyclic ring adopts chair conformation with equatorial orientations of the aryl and phenyl groups. Proton and carbon chemical shifts suggest that in the sulfoxides, the S=O bond is axial and enhances the J _aa value by some special effect. The S = O bond causes a significant upfield shift even on carbons without hydrogens. Significant solvent shifts also were observed.     

Microcombustion of ng Amounts of Carbon in Non-Volatile Materials for isotope Ratio Evaluation

Abstract

A novel microcombustion technique for carbon isotopic analysis of nanogram amounts of carbon in non-volatile materials based on isotope ratio monitoring (irm) mass spectrometry is described. Liquid or solid samples placed in a quartz sleeve are combusted at 1000°C in a continuous stream of helium and oxygen. CO₂ removed from the carrier gas stream by cryogenic trapping is transferred onto a GC column. Following GC separation, the CO₂ is transferred via an open split to the ion source of a gas isotope ratio mass spectrometer. Reproducibility for samples >25 nmol carbon is <1‰. Problems associated with blanks from various sources and with reproducible deposition of small sample amounts led to variable accuracy, which was dependent on the compound class being analysed. Minimum sample size was in the range from 5 to 10 nmol carbon. Measurements of dissolved organic carbon (DOC) of groundwater from Germany yielded consistent values of δ¹³C = -28.8‰.     

Systematic and Regularities in the Origin of 2H Patterns in Natural Compounds

Abstract

Deuterium patterns of natural compounds and their synthetic analogues, preferably obtained by NMR-measurements, are routinely determined in context with authenticity checks and origin assignments. So far, the use of the data is nearly exclusively empirically, and systematic correlations between the patterns and isotope effects on or mechanisms of the reactions involved have not yet been established.     

Prospects and Limitations of an Isotope Tracer Technique for Understanding Sulfur Cycling in Forested and Agro-Ecosystems

Abstract

Applications of isotopically distinct sulfur compounds have recently been used for tracing the fate of added sulfur in whole catchments or sub-compartments therein. Basic principles, the analytical methodology, and data evaluation for this isotope tracer technique are briefly described. We recommend that δ³⁴S-values of applied and natural sulfur compounds in the investigated ecosystem should differ by more than 20‰ in order to successfully ascertain sulfur fluxes. Where possible, a high ratio of applied sulfur loads versus sulfur pool sizes in the ecosystem should also be realized in order to allow the assessment of sulfur transformations in the study area. Prospects and limitations of this isotope tracer technique are critically discussed by reviewing results from recently or currently conducted lysimeter and field experiments.     

Determination of 13C Enrichment by Conventional GC-MS and GC-(MS)-C-IRMS

Abstract

Isotopic enrichment of branched-chain L-amino acids (BCAA) and branched-chain 2-oxo acids (BCOA) in standard preparations and in human plasma samples withdrawn after oral loads with 1-¹³C labelled BCAA were measured on a conventional GC-MS system and an on-line GC-C-IRMS employing O-TMS quinoxalinol derivatives. It was concluded that the recently introduced GC-C-IRMS, owing to its high sensitivity, is the adequate analytical tool when tracer doses of stable isotope labelled compounds of low enrichment are to be used in biomedical in vivo studies.     

Laser spectroscopic monitoring of gas emission and measurements of the C/C isotope ratio in CO2 from a wood-based combustion

We report on the application of a compact and field-deployable instrument, based on a continuous-wave fiber-coupled Telecom external cavity diode laser, to measure the ¹³C/¹²C isotope ratio in CO₂ from a wood-based combustion. Carbon dioxide, the most important greenhouse gas, is a major product of combustion. The measurements of the ¹³C/¹²C isotopic ratio in CO₂ from combustion emission permit one to identify the CO₂ source and to study the temporal and spatial variations of pollution in the atmosphere. The average value of the ¹³CO₂/¹²CO₂ ratio is found to be (1.1011±0.0024)%. The corresponding δ-value relative to PDB standard is (−20.17±2.14)‰, which is in good agreement with the typical value of (−25±2)‰ for wood. Simultaneous monitoring of multiple species from gas emission has been performed using direct-absorption spectroscopy. The concentrations of C₂H₂, CO, CO₂ and H₂O were determined on the basis of integrated absorbance measured by least-squares fitting a Voigt lineshape to experimental absorption spectra.     

TEA CO2 laser induced breakdown versus selective photochemistry in C2F5H and C2F5H/C2F5T mixtures

In the context of laser separation of tritium isotope using C₂F₅T in mixtures with C₂F₅H, we have studied the laser induced dielectric breakdown (LIDB) as a function of the system pressure using 10.6 μm radiation of a TEA CO₂ laser. By taking also into account our isotope selective results, we have found that LIDB does not imply difficulties by affecting the laser selective process. Analysis of the experimental results shows that LIDB works by cascade ionization and the recombination constitutes the major loss process. The LIDB threshold fluence Φ_th for the tritiated mixture was found to be lower than the corresponding value in pure C₂F₅H indicating preionization in the medium due to β emission of tritium.     

基于傅里叶变换红外光谱法CO2气体碳同位素比检测研究

介绍了基于傅里叶变换红外技术检测CO₂气体碳同位素比的新方法, 详细介绍了如何从HITRAN红外数据库中提取气体标准吸收截面; 介绍了基于非线性最小二乘法反演CO₂气体碳同位素比和整套实验装置的组成及实验步骤. 从理论和实验分析两方面讨论了温度和气压变化对δ¹³CO₂值的影响规律. 对于同一CO₂标准气体, 采用FTIR和同位素质谱法两种技术进行了δ¹³CO₂值对比检测, 两种测量技术的平均值差异仅为0.25%. 从实验结果可以看出, FTIR技术可以实现对CO₂气体碳同位素比的检测.     

C3 or C4 Macrophytes: A Specific Carbon Source for the Development of Semi-Aquatic and Terrestrial Arthropods in Central Amazonian River-Floodplains According to δ13C Values

Abstract

C₄ plant species were proposed to generally represent inferior food sources compared to C₃ plants thus are avoided by herbivores, particularly insects. This was tested in semi-aquatic and terrestrial arthropods from Amazonian river-floodplains by carbon isotope discrimination (δ¹³C). Two semi-aquatic grasshopper species (Stenacris f. fissicauda, Tucayaca gracilis—Acrididae) obtain their carbon during development from specific C₄ macrophytes and two semi-aquatic species (Cornops aquaticum—Acrididae, Paulinia acuminata—Pauliniidae) from specific C₃ macrophytes. The terrestrial millipede Mestosoma hylaeicum (Paradoxosomatidae) obtains about 45% of its carbon from roots of one C₄ macrophyte during the development of immatures whereas adults use other food sources, including C₃ trees. Results suggest, that (1) both C₄ and C₃ plants represent distinct hosts for terrestrial arthropods in Amazonia; (2) immatures may use plant species with a different photosynthetic pathway than adults.     

First real-time measurement of the evolving 2H/1H ratio during water evaporation from plant leaves

We have studied the temporal behaviour of the deuterium isotope ratio of water vapour emerging from a freshly cut plant leaf placed in a dry nitrogen atmosphere. The leaf material was placed directly inside the sample gas cell of the stable isotope ratio infrared spectrometer. At the reduced pressure ( approximately 40 mbar) inside the cell, the appearance of water evaporating from the leaf is easily probed by the spectrometer, as well as the evolving isotope ratios, with a precision of about 1 per thousand. The demonstration experiment we describe measures the 2H/1H isotope ratio only, but the experiment can be easily extended to include the 18O/16O and 17O/16O isotope ratios. Plant leaf water isotope ratios provide important information towards quantification of the different components in the ecosystem water and carbon dioxide exchange.     

Infrared Spectroscopic Study of Td‐Type Piperazinemetal(II) Tetracyanometallate(II) Benzene(1/1) Clathrates: Cd(C4H10N2)Cd(CN)4·C6H6 and Cd(C4H10N2)Hg(CN)4·1,25 C6H6

Abstract

The title compounds have been prepared in powder form. Their spectral data have been compared with those of the corresponding host complexes and found to be consistent with the host structure found in T_d‐type clathrates.     

Low-temperature sealed tube combustion of gaseous,liquid and solid organic compounds for 13C/12C and 14C analysis

A new, low-temperature sealed tube technique for combustion of organic carbon prior to subsequent off-line isotope analysis is proposed. Complete oxidation is achieved with potassium peroxodisulfate and silver permanganate as oxidants at temperatures not exceeding 500 °C. The combustion of gaseous (methane), solid (cane sugar, vanilla, N-thiazolyl-2-sulfamide, ascorbic acid, phenanthrene, thiourea, polyethylenefilm, tetrafluoropolyethylene, polyetheretherketone, graphite, and Suwannee River Fulvic Acid), and liquid (tetrachloroethene, toluene, and oil) model compounds and international standards was tested. A 24 h combustion at 500 °C was sufficient for complete oxidation in all cases. The time required for complete oxidation of Suwannee River Fulvic Acid, typical of refractory freshwater dissolved organic carbon, as a function of combustion temperature was 2 h at 500 °C, 6 h at 400 °C, and 24 h at 300 °C. Preparation of saline solution parallels of cane sugar, vanilla, N-thiazolyl-2-sulfanilamide, and ascorbic acid gave consistent results. For reproducible δ¹³C analyses using a Thermoquest MAT 252 MS, a minimum of 5 µg C had to be combusted. Reliable ¹⁴C results, measured at an accelerator mass spectrometer facility, were obtained from coal and from cane sugar combusted for 24 h at 500 °C by the proposed method.     

A Dual 13C and 15N Long Term Labelling Technique to Investigate Uptake and Translocation of C and N in Beech (Fagus sylvatica L.)

Abstract

A continuous dual ¹³CO₂ and ¹⁵NH₄ ¹⁵NO₃ labelling experimental set-up is presented that was used to investigate the C and N uptake and allocation within 3-year old beech (Fagus sylvatica L.) during one growing season. The C and N allocation pattern was determined after six, twelve and eighteen weeks of growth. The carbon uptake was distinctly different in the three phases examined: The first six weeks after budbreak were dedicated to leaf growth with a R/S (root to shoot) ratio of 0.14 for the new carbon. The second growth phase showed a balanced R/S ratio of C allocation and after week 13, the root compartment was the main carbon sink (R/S = 6.97).

Nitrogen allocation was more basipetal as compared to carbon. In the second growth phase, R/S of N_new was 5.57 but fell to 3.54 for the third growth phase probably due to formation of reserves in buds and stem.     

H/D isotope effect for solubility of hydrogen in doped perovskites

A novel method for studying the H/D isotope separation effect in the “nonstoichiometric oxide-gas” system is suggested. The theoretical scheme of this method is represented for doped perovskites of the ABO₃ family, but this approach is also applicable to other compounds where the solubility of hydrogen is determined by the content of oxygen vacancies. The suggested approach is used to determine the H/D isotope effect in hydrogen solubility from the experimental data for proton-conducting oxides. The measurements have been taken using the nuclear microanalysis of fine-grain BaZr_0.9Y_0.1O_{3 − y} powders. The method is based on the study of the products of the ²H(d, p)³H nuclear reaction. The observed pronounced isotope effect is in quantitative agreement with our theoretical predictions.     

Qualitative sims analysis of<Superscript>28,29,30</Superscript>Si isotope concentration in silicon using a Tof.Sims-5 Setup

The possibility of quantitative SIMS determination of^28-30Si isotope concentrations in silicon samples using a TOF.SIMS-5 spectrometer is shown. Th e isotope composition of a large number of Si samples, namely epitaxial Si layers with a natural isotope ratio, amorphous Si films depleted of²⁸Si isotope (deposited on natural Si substrates), and samples enriched with ²⁸Si isotope (manufactured by VITCON) is investigated. Substantial variations in the ²⁹Si/³⁰Si isotope ratio (from 1.51 for the natural content up to 25 in the case of limiting enrichment with ²⁸Si isotope) are revealed.