scholarly journals Mass spectrometric measurement of hydrogen isotope fractionation for the reactions of chloromethane with OH and Cl

2018 ◽  
Author(s):  
Frank Keppler ◽  
Enno Bahlmann ◽  
Markus Greule ◽  
Heinz Friedrich Schöler ◽  
Julian Wittmer ◽  
...  
Keyword(s):  
Hydrogen Isotope ◽  
Isotope Fractionation ◽  
Isotope Effects ◽  
Isotope Analysis ◽  
Isotope Ratio Mass Spectrometry ◽  
Detailed Knowledge ◽  
Mass Spectrometric Measurement ◽  
Isotopic Analyses ◽  
Chlorine Radicals ◽  
Stable Hydrogen Isotope

Abstract. Chloromethane (CH3Cl) is an important provider of chlorine to the stratosphere but yet lacks detailed knowledge of its budget. Stable isotope analysis is potentially a powerful tool to constrain CH3Cl flux estimates. The largest degree of isotope fractionation is expected to occur for deuterium in CH3Cl in the hydrogen abstraction reactions with its main sink reactant tropospheric OH and its minor sink reactant Cl atoms. We determined the isotope fractionation by stable hydrogen isotope analysis of the fraction of CH3Cl remaining after reaction with hydroxyl and chlorine radicals in a 3.5 m3 Teflon smog-chamber at 293 ± 1 K. We measured the increasing stable hydrogen isotope values of the unreacted CH3Cl using compound specific thermal conversion isotope ratio mass spectrometry. The isotope fractionations of CH3Cl for the reactions with hydroxyl and chlorine radicals were found to be −242 ± 7 mUr (or ‰) and −280 ± 11 mUr, respectively. For comparison, we performed similar experiments using methane (CH4) as the target compound with OH and obtained a fractionation constant of −205 ± 6 mUr which is in good agreement with values previously reported. The observed large kinetic isotope effects are helpful when employing isotopic analyses of CH3Cl in the atmosphere to improve our knowledge of its atmospheric budget.

scholarly journals Mass spectrometric measurement of hydrogen isotope fractionation for the reactions of chloromethane with OH and Cl

2018 ◽  
Vol 18 (9) ◽  
pp. 6625-6635 ◽  
Author(s):  
Frank Keppler ◽  
Enno Bahlmann ◽  
Markus Greule ◽  
Heinz Friedrich Schöler ◽  
Julian Wittmer ◽  
...  
Keyword(s):  
Hydrogen Isotope ◽  
Isotope Fractionation ◽  
Isotope Effects ◽  
Isotope Analysis ◽  
Isotope Ratio Mass Spectrometry ◽  
Detailed Knowledge ◽  
Mass Spectrometric Measurement ◽  
Isotopic Analyses ◽  
Chlorine Radicals ◽  
Stable Hydrogen Isotope

Abstract. Chloromethane (CH3Cl) is an important provider of chlorine to the stratosphere but detailed knowledge of its budget is missing. Stable isotope analysis is a potentially powerful tool to constrain CH3Cl flux estimates. The largest degree of isotope fractionation is expected to occur for deuterium in CH3Cl in the hydrogen abstraction reactions with its main sink reactant tropospheric OH and its minor sink reactant Cl atoms. We determined the isotope fractionation by stable hydrogen isotope analysis of the fraction of CH3Cl remaining after reaction with hydroxyl and chlorine radicals in a 3.5 m3 Teflon smog chamber at 293 ± 1 K. We measured the stable hydrogen isotope values of the unreacted CH3Cl using compound-specific thermal conversion isotope ratio mass spectrometry. The isotope fractionations of CH3Cl for the reactions with hydroxyl and chlorine radicals were found to be -264±45 and -280±11 ‰, respectively. For comparison, we performed similar experiments using methane (CH4) as the target compound with OH and obtained a fractionation constant of -205±6 ‰ which is in good agreement with values previously reported. The observed large kinetic isotope effects are helpful when employing isotopic analyses of CH3Cl in the atmosphere to improve our knowledge of its atmospheric budget.

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 On the interference of Kr during carbon isotope analysis of methane using continuous-flow combustion–isotope ratio mass spectrometry

2013 ◽  
Vol 6 (5) ◽  
pp. 1425-1445 ◽  
Author(s):  
J. Schmitt ◽  
B. Seth ◽  
M. Bock ◽  
C. van der Veen ◽  
L. Möller ◽  
...  
Keyword(s):  
Mass Spectrometry ◽  
Carbon Isotope ◽  
Isotope Ratio ◽  
Stable Carbon Isotope ◽  
Isotope Analysis ◽  
Isotope Ratio Mass Spectrometry ◽  
Mass Spectrometric Measurement ◽  
Broad Signal ◽  
Carbon Isotope Analysis ◽  
Singly Charged

Abstract. Stable carbon isotope analysis of methane (δ13C of CH4) on atmospheric samples is one key method to constrain the current and past atmospheric CH4 budget. A frequently applied measurement technique is gas chromatography (GC) isotope ratio mass spectrometry (IRMS) coupled to a combustion-preconcentration unit. This report shows that the atmospheric trace gas krypton (Kr) can severely interfere during the mass spectrometric measurement, leading to significant biases in δ13C of CH4, if krypton is not sufficiently separated during the analysis. According to our experiments, the krypton interference is likely composed of two individual effects, with the lateral tailing of the doubly charged 86Kr peak affecting the neighbouring m/z 44 and partially the m/z 45 Faraday cups. Additionally, a broad signal affecting m/z 45 and especially m/z 46 is assumed to result from scattered ions of singly charged krypton. The introduced bias in the measured isotope ratios is dependent on the chromatographic separation, the krypton-to-CH4 mixing ratio in the sample, the focusing of the mass spectrometer as well as the detector configuration and can amount to up to several per mil in δ13C. Apart from technical solutions to avoid this interference, we present correction routines to a posteriori remove the bias.

scholarly journals Using stable isotopes to estimate migratory connectivity for a patchily distributed, wetland-associated Neotropical migrant

The Condor ◽  
2019 ◽  
Vol 121 (4) ◽  
Author(s):  
Jessie Reese ◽  
Catherine Viverette ◽  
Christopher M Tonra ◽  
Nicholas J Bayly ◽  
Than J Boves ◽  
...  
Keyword(s):  
Hydrogen Isotope ◽  
Isotope Analysis ◽  
Distribution Model ◽  
Migratory Connectivity ◽  
Calibration Equation ◽  
Abundance Data ◽  
Assignment Model ◽  
Breeding Distribution ◽  
Stable Hydrogen Isotope ◽  
Species Specific

Abstract Estimates of migratory connectivity are needed for full annual cycle population models of migratory bird species experiencing rapid declines in abundance. One technique to determine migratory connectivity is through stable isotope analysis. This low-resolution method may be influenced by how data are calibrated between isotopes measured in precipitation and those measured in feathers, and can be informed by incorporating relative abundance into the assignment model. eBird abundance maps are a new tool combining citizen science data into a predictive species distribution model. In the Prothonotary Warbler (Protonotaria citrea), a wetland-associated songbird with a patchy breeding distribution, we sought to use stable-hydrogen isotope analysis informed by a species-specific calibration equation and eBird abundance data to determine the strength of migratory connectivity. We developed a species-specific calibration equation using known-origin samples from the breeding grounds and found that stable-hydrogen isotope values measured in precipitation explained 50% of the variation in stable-hydrogen isotope values among feathers. We found that the assignment model incorporating eBird abundance data correctly identified the true origins of 66% of individuals, and that the average assignment area (as a measure of precision) was 64% of the breeding distribution. These results represented a 7% increase in precision and a 3% decrease in accuracy when compared to a model that was not informed by abundance. Based on these models, wintering populations from 6 countries represented a mix of likely breeding origins, suggesting low migratory connectivity for Prothonotary Warblers. We found evidence that wintering latitude was related to likely breeding origin, with individuals at western wintering locations more likely to have southern breeding origins, but this relationship was weak. These results corroborate studies using archival light-level geolocators and high-resolution genetic markers, which also demonstrated weak migratory connectivity in this species. For patchily distributed species, eBird abundance data may not provide a useful increase in precision and accuracy for isotope assignments.

Using Stable Hydrogen Isotope Analysis of Feathers to Delineate Origins of Harvested Sandhill Cranes in the Central Flyway of North America

Waterbirds ◽  
2006 ◽  
Vol 29 (2) ◽  
pp. 137-147 ◽  
Author(s):  
Keith A. Hobson ◽  
Steven Van Wilgenburg ◽  
Leonard I. Wassenaar ◽  
Helen Hands ◽  
William P. Johnson ◽  
...  
Keyword(s):  
North America ◽  
Hydrogen Isotope ◽  
Isotope Analysis ◽  
Stable Hydrogen Isotope ◽  
Sandhill Cranes ◽  
Central Flyway
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