Gas Isotope Ratio Research Articles

Measurement of carbon-13 dioxide/carbon-12 dioxide abundance by nondispersive infrared heterodyne ratiometry as an alternative to gas isotope ratio mass spectrometry

La teneur en 13 C dans le gaz respiratoire peut etre determinee avec une precision suffisante pour des etudes cliniques

13C]Acetate Oxidation in Infants After Oral Versus Rectal Administration

Summary:To study the fate of volatile fatty acids (VFA) in the large bowel, we compared the rate of oxidation of 13C‐labeled VFA administered rectally with that of the orally administered substrate. On two different days, 1‐[13C]acetate was administered rectally or orally to five infants recovering from diarrhea. Breath samples were collected over 4 h and analyzed for 13C enrichment of breath CO2 by gas isotope ratio mass spectrometry. The percent dose recoveries of 13C in breath were fitted to multicom‐partmental models using the SAAM‐27 program. Following model development procedures, the oral acetate breath test curves could be accounted for only by a compartmental model in which labeled acetate underwent absorption into and mixed with a systemic pool before oxidation took place. The rectal acetate breath test curves could be accounted for by a simpler model in which oxidation occurred directly in the compartment in which the rectal acetate was administered, and required no rate‐limiting absorptive process. Our results indicate that the labeled acetate was oxidized more rapidly when the substrate was administered rectally than orally. This observation points to the direct utilization of volatile fatty acids within the colon.

Noble gas systematics for coexisting glass and olivine crystals in basalts and dunite xenoliths from Loihi Seamount

Noble gas isotopes including 3He/ 4He, 40Ar/ 36Ar and Xe isotope ratios were determined for coexisting glass and olivine crystals in tholeiitic and alkalic basalts and dunite xenoliths from Loihi Seamount. Glass and coexisting olivine crystals have similar 3He/ 4He ratios (2.8–3.4) × 10 −5, 20 to 24 times the atmospheric ratio ( R A), but different 40Ar/ 36Ar ratios (400–1000). Based on the results of noble gas isotope ratios and microscopic observation, some olivine crystals are xenocrysts. We conclude that He is equilibrated between glass and olivine xenocrysts, but Ar is not. The apparent high 3He/ 4He ratio (3 × 10 −5; = 21 R A) coupled with a relatively high 40Ar/ 36Ar ratio (4200) for dunite xenoliths (KK 17-5) may be explained by equilibration of He between MORB-type cumulates and the host magma. Except for the dunite xenoliths, noble gas data for these Loihi samples are compatible with a model in which samples from hot spot areas may be explained by mixing between P (plume)-type and M (MORB)-type components with the addition of A (atmosphere)-type component. Excess 129Xe has not been observed due to apparent large mass fractionation among Xe isotopes.

Noble gases in submarine pillow volcanic glasses

Fifteen submarine glasses from the East Pacific Rise (CYAMEX), the Kyushu-Palau Ridge (DSDP Leg 59) and the Nauru Basin (DSDP Leg 61) were analysed for noble gas contents and isotopic ratios. Both the East Pacific Rise and Kyushu-Palau Ridge samples showed Ne excess relative to Ar and a monotonic decrease from Xe to Ar when compared with air noble gas abundance. This characteristic noble gas abundance pattern (type 2, classified by Ozima and Alexander) is interpreted to be due to a two-stage degassing from a noble gas reservoir with originally atmospheric abundance. In the Kyushu-Palau Ridge sample, noble gases are nearly ten times more abundant than in the East Pacific Rise samples. This may be attributed to an oceanic crust contamination in the former mantle source. There is no correlation between the He content and that of the other noble gas in the CYAMEX samples. This suggests that He was derived from a larger region, independent from the other noble gases. Except where radiogenic isotopes are involved, all other noble gas isotopic ratios were indistinguishable from air noble gas isotopic ratios. The 3He/ 4He in the East Pacific Rise shows a remarkably uniform ratio of (1.21±0.07)×10 −5, while the 40Ar/ 36Ar ranges from 700 to 5600.

Noble gas composition and isotopic ratios in mantle materials(Abstracts of Papers Presented at the Spring Meeting of the Society, 1982)

Noble gas composition and isotopic ratios in mantle materials(Abstracts of Papers Presented at the Spring Meeting of the Society, 1982)

Neon composition in solar flares

To examine whether the long‐term averaged solar flare Ne is "planetary" type, as observed in contemporary solar flares, we have studied etched feldspar separates of several lunar soils and three samples from different depths of two well‐documented lunar rocks. Our results of noble gas elemental and isotopic ratios suggest that the long‐term average solar flare Ne composition is more similar to "solar" type than the "planetary" type.

Noble Gases in Stratospheric Dust Particles: Confirmation of Extraterrestrial Origin

Noble gas elemental and isotopic ratios were measured in a group of 13 "chondritic" stratospheric dust particles. Neon and argon are present in "solar" proportions; xenon appears to be dominated by contributions from "planetary" sources. The apparent xenon concentration is higher than that measured in any bulk meteorite, approaching the concentration found in the noble gas-rich, acid-insoluble residues from carbonaceous chondrites.

Rare Gas Isotopes in Hawaiian Ultramafic Nodules and Volcanic Rocks: Constraint on Genetic Relationships

Differences in the rare gas isotopic ratios, especially the ratios of helium-3 to helium-4 and of argon-40 to argon-36, in Hawaiian ultramafic nodules and phenocrysts in volcanic rocks indicate that the nodules and phenocrysts were derived from different sources. The isotopic ratios in ultramafic nodules are similar to those in oceanic tholeiites. The phenocrysts seem to have formed in equilibrium with source materials richer in primordial components than those of the oceanic tholeiites. Mixing between the sources is quite likely.

Rare gas isotopes in Hawaiian ultramafic nodules and volcanic rocks: constraint on genetic relationships : Kaneoka, Ichiro and Nobuo Takaoka, 1980. Science, 208(4450): 1366–1368

Differences in the rare gas isotopic ratios, especially the ratios of helium-3 to helium-4 and of argon-40 to argon-36, in Hawaiian ultramafic nodules and phenocrysts in volcanic rocks indicate that the nodules and phenocrysts were derived from different sources. The isotopic ratios in ultramafic nodules are similar to those in oceanic tholeiites. The phenocrysts seem to have formed in equilibrium with source materials richer in primordial components than those of the oceanic tholeiites. Mixing between the sources is quite likely.

Protein amino acid analysis by an isotope ratio gas chromatography mass spectrometry computer technique.

A method for quantitative analysis of protein amino acids by a gas chromatography mass spectrometry computer system is described. Amino acids were analysed as their N-trifluoroacetyl n-butyl ester derivatives. Isotope ratio determination was used as the quantitating technique via multiple internal standards. The exact composition of a deuterated amino acid mixture was determined against a standard amino acid calibration mixture and in turn the protein amino acid composition was determined against the deuterated amino acid mixture. The amount of protein taken for analysis was 100 micrograms and the procedure, excluding hydrolysis, could be performed with 2 1/2 hours. The introduction of the internal standards prior to protein hydrolysis provides a method with good precision (mean coefficient of variation less than 5%). The method, tested on insulin, gave results which agreed well with the known composition of the protein and with simultaneous analysis on ion exchangers.

Origin of Gases Adsorbed in Near-Surface Sediment Identified by Carbon Isotopes: ABSTRACT

Carbon isotope ratios of gases desorbed from nearshore sediment samples collected from the Anadarko basin and from the North Sea have been determined by a technique recently developed in the Hannover laboratories. The results show a relation to geochemical data of the deep pooled hydrocarbons in both areas. Because of this relation, isotope analyses of adsorbed gases are of great interest in crude oil exploration. End_of_Article - Last_Page 701------------

Helium isotope ratios in Yellowstone and Lassen Park volcanic gases

Helium isotope ratios (³He/4He) in Lassen Park and Yellowstone Park volcanic gases show large ³He enrichments relative to atmospheric and crustal helium indicating the presence of a dominant mantle‐helium component. The ratios in Lassen helium are 8 times atmospheric in acid hot spring gases, and about 3 times atmospheric in the gas phase in near‐neutral high‐temperature waters; the acid‐spring helium is thus isotopically similar to helium in island‐arc and other continental‐margin orogenic areas. At Yellowstone, however, the isotopic ratio in helium from the Mud Volcano area, in the eastern part of Yellowstone caldera, is 15.6 times atmospheric, similar to the ratio in helium from Kilauea and Iceland. These high ratios, 15 times atmospheric or greater, are probably distinctively associated with deep‐mantle plumes under hot‐spots, while ratios about 10 times atmospheric characterize mantle helium in basalt glasses at the crests of mid‐ocean rises. The presence of “Kilauea‐type” helium at Yellowstone indicates that at least in certain areas the continental crust is essentially transparent to mantle volatiles.

Rare gas isotopic compositions in diamonds

RARE gas isotopic compositions such as 40Ar/36Ar, 3He/4He and 129Xe/132Xe in the Earth have provided a powerful tool for understanding the origin and evolution of the terrestrial atmosphere1–4. The isotopic information may be obtained from rare gases trapped in some mantle-derived materials such as volcanic rocks, volcanic xenoliths or volcanic gases. Among these mantle-derived materials, diamond seems to be unique due to its almost complete inertness to any known chemical and to its enormous stability against high temperature. Although the presence of O2, H2, CH4, H2O, CO, N2, Ar and CO2 in diamonds has been reported5,6. No previous measurement has been made either on elemental compositions or on isotopic ratios of rare gases in diamonds. Here we report on rare gas elemental composition and isotopic ratios in diamond. We found that 3He/4He ratio is more than an order of magnitude larger than the atmospheric value and also 40Ar/36Ar ratio is significantly higher.

Mass spectrometric analysis of gas inclusions in Muong Nong glass and Libyan Desert glass

Noble and non-noble gases in bubbles of Muong Nong- and Libyan Desert glass were released by vacuum crushing at room temperature and measured by high sensitivity mass spectrometry. The N 2:Ar:Kr:Xe ratio as well as the rare gas isotope ratios were found to be atmospheric, indicating the terrestrial origin of these glasses. The concentrations of the active gases O 2, CO 2, CO and SO 2 vary highly between adjacent bubbles. Total gas pressure in the bubbles of the glasses is in the 100 mm range, much higher than that found for other types of tektites.