Hydrogen isotope fractionation factors for N,N-dimethylbenzylammonium ion and some related species: an unusually strong preference for deuterium over protium

1997 ◽  
pp. 295-298
Author(s):  
Hong-Xun Guo ◽  
A. Jerry Kresge
Keyword(s):  
Related Species ◽  
Hydrogen Isotope ◽  
Isotope Fractionation ◽  
Strong Preference ◽  
Fractionation Factors

scholarly journals Equilibrium oxygen- and hydrogen-isotope fractionation between ice and water

1991 ◽  
Vol 37 (125) ◽  
pp. 23-26 ◽  
Author(s):  
M. Lehmann ◽  
U. Siegenthaler
Keyword(s):  
Sea Ice ◽  
Hydrogen Isotope ◽  
Isotope Fractionation ◽  
Water Mass ◽  
Precision Measurements ◽  
Deuterium Excess ◽  
Water Ice ◽  
Equilibrium Oxygen ◽  
Fractionation Factors ◽  
Equilibrium Fractionation

Abstract We have performed high-precision measurements of the isotope-fractionation factors between ice and water. Ice was grown from a stirred water mass on a cooling plate. The freezing velocity was varied, keeping the stirring rate of the water constant, so that the equilibrium fractionation factors could be determined by extrapolating to zero freezing velocity. The resulting values are ∝ (18O/16O) = 1.00291 ± 0.00003 and ∝ (D/H) = 1.0212 ± 0.0004. Non-equilibrium freezing of lake and sea ice is briefly discussed as well as the significance of our results for the deuterium excess in polar precipitation.

Hydrogen isotope fractionation between methanol and diphenylphosphine or dimethylphosphine in the gas phase and in aprotic solvents

1996 ◽  
Vol 74 (8) ◽  
pp. 1465-1469
Author(s):  
Andrzej Wawer ◽  
Jerzy Szydtlowski
Keyword(s):  
Interaction Energy ◽  
Gas Phase ◽  
Hydrogen Isotope ◽  
Isotope Fractionation ◽  
Isotope Effects ◽  
Solvent Polarity ◽  
Exchange Reactions ◽  
Fractionation Factor ◽  
The Given ◽  
Fractionation Factors

D/H fractionation factors between MeOH and Ph2PH in dilute solutions of tetrachloroethylene, benzene, tetrahydrofuran, pyridine, and acetonitrile and T/H fractionation factors between MeOH and Me2PH vapors were measured. The experimental results agree very well with values calculated from the statistical theory of isotope effects formulated by Bigeleisen and Mayer. There are correlations between observed fractionation factors and solvent polarity, and the interaction energy of methanol with the given solvent. Another correlation has been found between enthalpy of the exchange reactions and the interaction energy between methanol and the given solvent. Key words: isotope effects, fractionation factor, diphenylphosphine, methanol.

scholarly journals Equilibrium oxygen- and hydrogen-isotope fractionation between ice and water

1991 ◽  
Vol 37 (125) ◽  
pp. 23-26 ◽  
Author(s):  
M. Lehmann ◽  
U. Siegenthaler
Keyword(s):  
Sea Ice ◽  
Hydrogen Isotope ◽  
Isotope Fractionation ◽  
Water Mass ◽  
Precision Measurements ◽  
Deuterium Excess ◽  
Water Ice ◽  
Equilibrium Oxygen ◽  
Fractionation Factors ◽  
Equilibrium Fractionation

AbstractWe have performed high-precision measurements of the isotope-fractionation factors between ice and water. Ice was grown from a stirred water mass on a cooling plate. The freezing velocity was varied, keeping the stirring rate of the water constant, so that the equilibrium fractionation factors could be determined by extrapolating to zero freezing velocity. The resulting values are∝ (18O/16O) = 1.00291 ± 0.00003 and∝ (D/H) = 1.0212 ± 0.0004.Non-equilibrium freezing of lake and sea ice is briefly discussed as well as the significance of our results for the deuterium excess in polar precipitation.

scholarly journals Unravelling the process of petroleum hydrocarbon biodegradation in different filter materials of constructed wetlands by stable isotope fractionation and labelling studies

2021 ◽  
Author(s):  
Andrea Watzinger ◽  
Melanie Hager ◽  
Thomas Reichenauer ◽  
Gerhard Soja ◽  
Paul Kinner
Keyword(s):  
Stable Isotope ◽  
Constructed Wetlands ◽  
Hydrogen Isotope ◽  
Petroleum Hydrocarbon ◽  
Isotope Fractionation ◽  
Isotope Effects ◽  
Filter Material ◽  
Hydrocarbon Biodegradation ◽  
Stable Isotope Fractionation ◽  
Filter Materials

AbstractMaintaining and supporting complete biodegradation during remediation of petroleum hydrocarbon contaminated groundwater in constructed wetlands is vital for the final destruction and removal of contaminants. We aimed to compare and gain insight into biodegradation and explore possible limitations in different filter materials (sand, sand amended with biochar, expanded clay). These filters were collected from constructed wetlands after two years of operation and batch experiments were conducted using two stable isotope techniques; (i) carbon isotope labelling of hexadecane and (ii) hydrogen isotope fractionation of decane. Both hydrocarbon compounds hexadecane and decane were biodegraded. The mineralization rate of hexadecane was higher in the sandy filter material (3.6 µg CO2 g−1 day−1) than in the expanded clay (1.0 µg CO2 g−1 day−1). The microbial community of the constructed wetland microcosms was dominated by Gram negative bacteria and fungi and was specific for the different filter materials while hexadecane was primarily anabolized by bacteria. Adsorption / desorption of petroleum hydrocarbons in expanded clay was observed, which might not hinder but delay biodegradation. Very few cases of hydrogen isotope fractionation were recorded in expanded clay and sand & biochar filters during decane biodegradation. In sand filters, decane was biodegraded more slowly and hydrogen isotope fractionation was visible. Still, the range of observed apparent kinetic hydrogen isotope effects (AKIEH = 1.072–1.500) and apparent decane biodegradation rates (k = − 0.017 to − 0.067 day−1) of the sand filter were low. To conclude, low biodegradation rates, small hydrogen isotope fractionation, zero order mineralization kinetics and lack of microbial biomass growth indicated that mass transfer controlled biodegradation.

scholarly journals Measurement on Diffusion Coefficients and Isotope Fractionation Factors by a Through-Diffusion Experiment

Minerals ◽  
2021 ◽  
Vol 11 (2) ◽  
pp. 208
Author(s):  
Takuma Hasegawa ◽  
Kotaro Nakata ◽  
Rhys Gwynne
Keyword(s):  
Groundwater Flow ◽  
Diffusion Coefficients ◽  
Isotope Fractionation ◽  
Free Water ◽  
Effective Porosity ◽  
Diffusion Experiment ◽  
Fractionation Factor ◽  
Through Diffusion ◽  
Geological Formations ◽  
Fractionation Factors

For radioactive waste disposal, it is important that local groundwater flow is slow as groundwater flow is the main transport medium for radioactive nuclides in geological formations. When the groundwater flow is very slow, diffusion is the dominant transport mechanism (diffusion-dominant domain). Key pieces of evidence indicating a diffusion-dominant domain are the separation of components and the fractionation of isotopes by diffusion. To prove this, it is necessary to investigate the different diffusion coefficients for each component and the related stable isotope fractionation factors. Thus, in this study, through-diffusion and effective-porosity experiments were conducted on selected artificial materials and natural rocks. We also undertook measurements relating to the isotope fractionation factors of Cl and Br isotopes for natural samples. For natural rock samples, the diffusion coefficients of water isotopes (HDO and H218O) were three to four times higher than those of monovalent anions (Cl−, Br- and NO3−), and the isotope fractionation factor of 37Cl (1.0017–1.0021) was slightly higher than that of free water. It was experimentally confirmed that the isotope fractionation factor of 81Br was approximately 1.0007–1.0010, which is equivalent to that of free water. The enrichment factor of 81Br was almost half that of 37Cl. The effective porosity ratios of HDO and Cl were slightly different, but the difference was not significant compared to the ratio of their diffusion coefficients. As a result, component separation was dominated by diffusion. For artificial samples, the diffusion coefficients and effective porosities of HDO and Cl were almost the same; it was thus difficult to assess the component separation by diffusion. However, isotope fractionation of Cl and Br was confirmed using a through-diffusion experiment. The results show that HDO and Cl separation and isotope fractionation of Cl and Br can be expected in diffusion-dominant domains in geological formations.

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