Determination of deuterated methanes for use as atmospheric tracers

Alei, Mohammed; Cappis, J.H.; Fowler, Μ. M.; Frank, Donald J.; Goldblatt, Maxwell; Guthals, P.R.; Mason, Allen S.; Mills, T. R.; Mroz, E. J.; Norris, T. L.; Perrin, R.E.; Poths, J.; Rokop, D.J.; Shields, William R.

doi:10.1016/0004-6981(87)90087-4

Cited by 16 publications

(8 citation statements)

References 6 publications

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“…The sample preparation procedure followed the standard method described by Stevens and Rust [ 1982]. The concentration procedures necessary for D/H determinations have been described by Wahlen et al [1989] and Alei et al [1987]. The air sample was pulled through a "Russian doll" trap at-196øC on a vacuum extraction line to remove CO2, H20, N20, and some nonmethane hydrocarbons [Brenninkmeo'er, 1991] and then through a trap containing 100 g charcoal (SK-4 Carbon, 40/60 mesh, Alltech Associates, Inc., Deerfield, Illinois) at -196øC to concentrate the CH4.…”

Section: Isotopic Analysis Of Cit4 In Air Samples the Preparation Ofmentioning

confidence: 99%

The D/H content of methane emitted from biomass burning

Snover¹,

Quay²,

Hao³

2000

Global Biogeochemical Cycles

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Section: Isotopic Analysis Of Cit4 In Air Samples the Preparation Ofmentioning

confidence: 99%

The D/H content of methane emitted from biomass burning

Snover¹,

Quay²,

Hao³

2000

Global Biogeochemical Cycles

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“…Methane for 14C analysis was concentrated onto charcoal at-196øC from the large-volume air samples [Alei et al, 1987]. The sample was metered through the charcoal bed at about 11 L min-• such that the pressure upstream of the liquid nitrogen trap was below 220 mm Hg to limit the condensation of oxygen.…”

Section: Measurements Ofmentioning

confidence: 99%

Carbon isotopic composition of atmospheric CH₄: Fossil and biomass burning source strengths

Quay¹,

King²,

Stutsman³

et al. 1991

Global Biogeochemical Cycles

228

115

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The 13C/12C of atmospheric methane (CH4) was measured at Point Barrow (71°N, 156°W), Olympic Peninsula (48°N, 126°W), Mauna Loa (19°N, 155°W), and Cape Grim (41°S, 144°E) between 1987 and 1989. The global average δ13CPDB from these measurements (n = 208) was −47.20 ± 0.13%o. The lowest mean annual δ13C value of‐47.61 ± 0.14‰ was measured at Point Barrow with values increasing to ‐47.03 ± 0.14‰ at Cape Grim. The seasonal cycle in the δ13C of CH4 was greatest at Point Barrow, with an amplitude of 0.5‰, and varied inversely with concentration. The isotopic fractionation during CH4 oxidation is calculated to be 0.993 ± 0.002 based on the measured CH4 concentration and δ13C values. The 14C content of atmospheric CH4, measured at monthly intervals at the Olympic Peninsula site between 1987 and 1989, is increasing at 1.4 ± 0.5 pM yr−1, primarily owing to 14CH4 release from nuclear reactors. The global average 14C content of 122 pM for CH4 implies a fossil methane source strength that is 16% of the total source. The global mean δ13C of −47.2‰, when coupled with the 14C results, implies that ∼11% of the total CH4 release rate is derived from biomass burning. These results indicate for a total CH4 source of ∼550 Tg yr−1 that natural gas release accounts for ∼90 Tg yr−1 and biomass burning yields ∼60 Tg yr−1. Preliminary analyses of the δ13C data using a three‐dimensional chemical tracer model indicate that the observed meridional gradients in the annual average δ13C and concentration of CH4 are most closely matched with a CH4 source scenario in which 11% of the CH4 is derived from biomass burning.

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“…To extract methane quantitatively from gas samples, we applied a preparative-gas chromatography technique modified from Alei et al (1987). In brief, a sample is introduced into a stream of helium.…”

Section: Sample Purification Proceduresmentioning

confidence: 99%

The geochemistry of methane isotopologues

Wang¹

2017

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This thesis documents the origin, distribution, and fate of methane and several of its isotopic forms on Earth. Using observational, experimental, and theoretical approaches, I illustrate how the relative abundances of 12 CH 4 , 13 CH 4 , 12 CH 3 D, and 13 CH 3 D record the formation, transport, and breakdown of methane in selected settings.Chapter 2 reports precise determinations of 13 CH 3 D, a "clumped" isotopologue of methane, in samples collected from various settings representing many of the major sources and reservoirs of methane on Earth. The results show that the information encoded by the abundance of 13 CH 3 D enables differentiation of methane generated by microbial, thermogenic, and abiogenic processes. A strong correlation between clumped-and hydrogen-isotope signatures in microbial methane is identified and quantitatively linked to the availability of H 2 and the reversibility of microbially-mediated methanogenesis in the environment. Determination of 13 CH 3 D in combination with hydrogen-isotope ratios of methane and water provides a sensitive indicator of the extent of C-H bond equilibration, enables fingerprinting of methane-generating mechanisms, and in some cases, supplies direct constraints for locating the waters from which migrated gases were sourced. Chapter 3 applies this concept to constrain the origin of methane in hydrothermal fluids from sediment-poor vent fields hosted in mafic and ultramafic rocks on slow-and ultraslow-spreading mid-ocean ridges. The data support a hypogene model whereby methane forms abiotically within plutonic rocks of the oceanic crust at temperatures above ca. 300• C during respeciation of magmatic volatiles, and is subsequently extracted during active, convective hydrothermal circulation. Chapter 4 presents the results of culture experiments in which methane is oxidized in the presence of O 2 by the bacterium Methylococcus capsulatus strain Bath. The results show that the clumped isotopologue abundances of partially-oxidized methane can be predicted from knowledge of 13 C/ 12 C and D/H isotope fractionation factors alone.: Shuhei Ono, Ph.D. Acknowledgments I fear that this section will not do justice to the people I have not the space to thank individually. Alas, here goes. To those whose names are not specifically listed here, thank you too. I wish first to thank Shuhei Ono. The work this thesis represents could not have happened without his bold vision and the license to explore and question that working in his lab afforded. His unbridled optimism, breadth of scientific curiosity, personal integrity, and accessibility to his personnel are traits I one day hope to emulate. I thank him for his nonjudgmental yet appropriately measured support of many of my ideas-even those that led nowhere-, for believing in me even when I found it difficult to do so myself, and for teaching me to change pump oil, build vacuum lines, and drink Icelandic vodka.I also wish to thank my thesis committee members Jeff Seewald, Roger Summons, and John Pohlman, for their in...

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Determination of deuterated methanes for use as atmospheric tracers

Cited by 16 publications

References 6 publications

The D/H content of methane emitted from biomass burning

The D/H content of methane emitted from biomass burning

Carbon isotopic composition of atmospheric CH₄: Fossil and biomass burning source strengths

The geochemistry of methane isotopologues

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Determination of deuterated methanes for use as atmospheric tracers

Cited by 16 publications

References 6 publications

The D/H content of methane emitted from biomass burning

The D/H content of methane emitted from biomass burning

Carbon isotopic composition of atmospheric CH4: Fossil and biomass burning source strengths

The geochemistry of methane isotopologues

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Carbon isotopic composition of atmospheric CH₄: Fossil and biomass burning source strengths