skip to main content
OSTI.GOV title logo U.S. Department of Energy
Office of Scientific and Technical Information

Title: Dual stable isotopes of CH 4 from Yellowstone hot-springs suggest hydrothermal processes involving magmatic CO 2

Abstract

Volcanism and post-magmatism contribute both significant annual CH 4 fluxes to the atmosphere (on par with other natural sources such as forest fire and wild animal emissions) and have been implicated in past climate-change events. The Yellowstone hot spot is one of the largest volcanic systems on Earth and is known to emit methane in addition to other greenhouse gases (e.g. carbon dioxide) but the ultimate source of this methane flux has not been elucidated. Here we use dual stable isotope analysis (δ 2H and δ 13C) of CH 4(g) sampled from ten high-temperature geothermal pools in Yellowstone National Park to show that the predominant flux of CH4(g) is abiotic. The average δ 13C and δ 2H values of CH 4(g) emitted from hot springs (-26.7 (±2.4) and -236.9 (±12.0) ‰, respectively) are not consistent with biotic (microbial or thermogenic) methane sources, but are within previously reported ranges for abiotic methane production. Correlation between δ 13C CH4 and δ 13C-dissolved inorganic C (DIC) also suggests that CO 2 is a parent C source for the observed CH 4(g). Moreover, CH 4-CO 2 isotopic geothermometry was used to estimate CH 4(g) formation temperatures ranging from ~ 250 - 350°C, which ismore » just below the temperature estimated for the hydrothermal reservoir and consistent with the hypothesis that subsurface, rock-water interactions are responsible for large methane fluxes from this volcanic system. An understanding of conditions leading to the abiotic production of methane and associated isotopic signatures are central to understanding the evolutionary history of deep carbon sources on Earth.« less

Authors:
ORCiD logo; ; ; ; ; ;
Publication Date:
Research Org.:
Pacific Northwest National Lab. (PNNL), Richland, WA (United States)
Sponsoring Org.:
USDOE
OSTI Identifier:
1378022
Report Number(s):
PNNL-SA-121866
Journal ID: ISSN 0377-0273; KP1601010
DOE Contract Number:
AC05-76RL01830
Resource Type:
Journal Article
Resource Relation:
Journal Name: Journal of Volcanology and Geothermal Research; Journal Volume: 341; Journal Issue: C
Country of Publication:
United States
Language:
English
Subject:
58 GEOSCIENCES; stable isotopes; hydrothermal; Yellowstone National Park; deep carbon; me; greenhouse gas

Citation Formats

Moran, James J., Whitmore, Laura M., Jay, Zackary J., Jennings, Ryan deM., Beam, Jacob P., Kreuzer, Helen W., and Inskeep, William P.. Dual stable isotopes of CH 4 from Yellowstone hot-springs suggest hydrothermal processes involving magmatic CO 2. United States: N. p., 2017. Web. doi:10.1016/j.jvolgeores.2017.05.011.
Moran, James J., Whitmore, Laura M., Jay, Zackary J., Jennings, Ryan deM., Beam, Jacob P., Kreuzer, Helen W., & Inskeep, William P.. Dual stable isotopes of CH 4 from Yellowstone hot-springs suggest hydrothermal processes involving magmatic CO 2. United States. doi:10.1016/j.jvolgeores.2017.05.011.
Moran, James J., Whitmore, Laura M., Jay, Zackary J., Jennings, Ryan deM., Beam, Jacob P., Kreuzer, Helen W., and Inskeep, William P.. Sat . "Dual stable isotopes of CH 4 from Yellowstone hot-springs suggest hydrothermal processes involving magmatic CO 2". United States. doi:10.1016/j.jvolgeores.2017.05.011.
@article{osti_1378022,
title = {Dual stable isotopes of CH 4 from Yellowstone hot-springs suggest hydrothermal processes involving magmatic CO 2},
author = {Moran, James J. and Whitmore, Laura M. and Jay, Zackary J. and Jennings, Ryan deM. and Beam, Jacob P. and Kreuzer, Helen W. and Inskeep, William P.},
abstractNote = {Volcanism and post-magmatism contribute both significant annual CH4 fluxes to the atmosphere (on par with other natural sources such as forest fire and wild animal emissions) and have been implicated in past climate-change events. The Yellowstone hot spot is one of the largest volcanic systems on Earth and is known to emit methane in addition to other greenhouse gases (e.g. carbon dioxide) but the ultimate source of this methane flux has not been elucidated. Here we use dual stable isotope analysis (δ2H and δ13C) of CH4(g) sampled from ten high-temperature geothermal pools in Yellowstone National Park to show that the predominant flux of CH4(g) is abiotic. The average δ13C and δ2H values of CH4(g) emitted from hot springs (-26.7 (±2.4) and -236.9 (±12.0) ‰, respectively) are not consistent with biotic (microbial or thermogenic) methane sources, but are within previously reported ranges for abiotic methane production. Correlation between δ13CCH4 and δ13C-dissolved inorganic C (DIC) also suggests that CO2 is a parent C source for the observed CH4(g). Moreover, CH4-CO2 isotopic geothermometry was used to estimate CH4(g) formation temperatures ranging from ~ 250 - 350°C, which is just below the temperature estimated for the hydrothermal reservoir and consistent with the hypothesis that subsurface, rock-water interactions are responsible for large methane fluxes from this volcanic system. An understanding of conditions leading to the abiotic production of methane and associated isotopic signatures are central to understanding the evolutionary history of deep carbon sources on Earth.},
doi = {10.1016/j.jvolgeores.2017.05.011},
journal = {Journal of Volcanology and Geothermal Research},
number = C,
volume = 341,
place = {United States},
year = {Sat Jul 01 00:00:00 EDT 2017},
month = {Sat Jul 01 00:00:00 EDT 2017}
}
  • Volcanism and post-magmatism contribute significant annual methane (CH 4) fluxes to the atmosphere (on par with other natural sources such as forest fire and wild animal emissions) and have been implicated in past climate-change events. The Yellowstone hot spot is one of the largest volcanic systems on Earth and is known to emit CH 4 (as well as carbon dioxide (CO 2) and other gases), but the ultimate sources of this CH 4 flux have not been elucidated. In this paper, we use dual stable isotope analysis (δ 2H and δ 13C) of CH 4 sampled from ten high-temperature geothermalmore » pools in Yellowstone National Park along with other isotopic and gas analyses to evaluate potential sources of methane. The average δ 13C and δ 2H values of CH 4 emitted from hot springs ( 26.7 (± 2.4) and - 236.9 (± 12.0) ‰, respectively) are inconsistent with microbial methanogenesis but do not allow distinction between thermogenic and abiotic sources. Correlation between δ 13C CH4 and δ 13C of dissolved inorganic C (DIC) is consistent with DIC as the parent C source for the observed CH 4, or with equilibration of CH 4 and DIC. Methane formation temperatures estimated by isotopic geothermometry based on δ 13C CH4 and δ 13C CO2 ranged from ~ 250–350 °C, which is just below previous temperature estimates for the hydrothermal reservoir. Further, the δ 2H H2O of the thermal springs and the measured δ 2H CH4 values are consistent with equilibration between the source water and the CH 4 at the formation temperatures. Though the ultimate origin of the CH 4 could be attributed to either abiotic of themorgenic processes with subsequent isotopic equilibration, the C 1/C 2+ composition of the gases is more consistent with abiotic origins for most of the samples. Finally, our data support the hypothesis that subsurface rock-water interactions are responsible for at least a significant fraction of the CH 4 flux from the Yellowstone National Park volcanic system.« less
  • The ..mu..-methylene cluster Ru/sub 3/(CO)/sub 7/(..mu..-CH)/..mu../sub 3/-eta/sup 3/-CH/sub 2/=C=C(i-Pr))/(..mu..-PPh/sub 2/) (2) synthesized from Ru/sub 3/-(CO)/sub 8//..mu..=eta/sup 3/-CH/sub 2/=C=C(i-Pr)/(..mu..-PPh/sub 2/) (1) via reaction with diazomethane, CH/sub 2/N/sub 2/, displays a remarkable reactivity associated with the ..mu..-CH/sub 2/ group under mild conditions. Slow isomerization of 2 to the 2-isopropyl-1,3-butadienediyl cluster (..mu..-H)Ru/sub 3/(CO)/sub 7//..mu../sub 3/-eta/sup 4/-CH=C(i-Pr)C=CH/sub 2//(..mu..-PPh/sub 2/) (3) (crystal data: triclinic, space group P anti 1, a = 9.333 (2) A, b = 10.200 (1) A, c = 16.297 (2) A, ..cap alpha.. = 87.25 (1)/sup 0/, ..beta.. = 83.26 (1)/sup 0/, ..gamma.. = 64.29 (1)/sup 0/, Z = 2, R =more » 0.25, R/sub w/ = 0.029 on 5899 observed reflections) occurs under nitrogen. Cluster 3 contains a triangular Ru/sub 3/ core with ..mu..-PPh/sub 2/ and ..mu..-H groups on one edge and a four-carbon hydrocarbyl ligand derived from a CH fragment of the ..mu..-methylene bride and the allenyl ligand of 2. Under an atmosphere of CO and in the presence of methanol complex 2 yields the open allenyl cluster Ru/sub 3/(CO)/sub 9//..mu../sub 3/-eta/sup 3/-CH/sub 2/=C=C(i-Pr)/(..mu..-PPh/sub 2/) (5) and methyl acetate, both of which were characterized spectroscopically.« less
  • Quantifying rates of microbial carbon transformation in peatlands is essential for gaining mechanistic understanding of the factors that influence methane emissions from these systems, and for predicting how emissions will respond to climate change and other disturbances. In this study, we used porewater stable isotopes collected from both the edge and center of a thermokarst bog in Interior Alaska to estimate in situ microbial reaction rates. We expected that near the edge of the thaw feature, actively thawing permafrost and greater abundance of sedges would increase carbon, oxygen and nutrient availability, enabling faster microbial rates relative to the center ofmore » the thaw feature. We developed three different conceptual reaction networks that explained the temporal change in porewater CO2, CH4, δ13C-CO2 and δ13C-CH4. All three reaction-network models included methane production, methane oxidation and CO2 production, and two of the models included homoacetogenesis — a reaction not previously included in isotope-based porewater models. All three models fit the data equally well, but rates resulting from the models differed. Most notably, inclusion of homoacetogenesis altered the modeled pathways of methane production when the reaction was directly coupled to methanogenesis, and it decreased gross methane production rates by up to a factor of five when it remained decoupled from methanogenesis. The ability of all three conceptual reaction networks to successfully match the measured data indicate that this technique for estimating in-situ reaction rates requires other data and information from the site to confirm the considered set of microbial reactions. Despite these differences, all models indicated that, as expected, rates were greater at the edge than in the center of the thaw bog, that rates at the edge increased more during the growing season than did rates in the center, and that the ratio of acetoclastic to hydrogenotrophic methanogenesis was greater at the edge than in the center. In both locations, modeled rates (excluding methane oxidation) increased with depth. A puzzling outcome from the effort was that none of the models could fit the porewater dataset without generating “fugitive” carbon (i.e., methane or acetate generated by the models but not detected at the field site), indicating that either our conceptualization of the reactions occurring at the site remains incomplete or our site measurements are missing important carbon transformations and/or carbon fluxes. This model–data discrepancy will motivate and inform future research efforts focused on improving our understanding of carbon cycling in permafrost wetlands.« less
  • The complexes (/sup +/-H)/sub 4/Ru/sub 4/(CO)/sub 10/(..mu..-)Ph/sub 2/P(CH/sub 2/)/sub n/PPh/sub 2/)) (n=1(1), 3 (3), 4 (4)), (..mu..-H)/sub 4/Ru/sub 4/(CO)/sub 10/(..mu..-)Ph/sub 2/PCH/sub 2/CH(CH/sub 3/)PPh/sub 2/)) (2a), (/sup +/-H)/sub 4/Ru/sub 4/(CO)/sub 10/)Ph/sub 2/PCH/sub 2/CH(CH/sub 3/)PPh/sub 2/) (2b), and ((..mu..-H)/sub 4/Ru/sub 4/(CO)/sub 11/)/sub 2/)Ph/sub 2/P(CH/sub 7/)/sub 5/PPh/sub 2/) (5a) have been characterized by IR, /sup 1/H NMR, and /sup 31/P NMR spectroscopy. The structures of compounds 1, 2a, 2b, 3, and 4 have been determined by single-crystal X-ray diffractometry. The diphosphine ligands are seen to bridge a Ru-Ru bond of the tetrahedral Ru/sub 4/ cluster in 1, 2a, 3, and 4, while themore » diphosphine ligand adopts a chelating mode of bonding in 2b. The hydride atoms in each of the structures were not located but were inferred from Ru-Ru bond lengths. They take up the same distribution of idealized C/sub s/ symmetry in all four structures. Where an asymmetric carbon atom is present (2a and 2b) only one of the two possible diastereoisomeric forms is found in the solid. Crystal data for the complexes are presented. 15 references, 4 figures, 8 tables.« less
  • Equations derived from a quadratic virial equation in pressure, with virial coefficients expressed as a function of temperature, are fitted to published P-V-T and solubility data to yield values of second and third virial coefficients for pure and mixed gases. These coefficients are not virial coefficients sensu stricto and are used to compute fugacity coefficients of pure H{sub 2}, H{sub 2}O, CO{sub 2} and CH{sub 4}, and of mixed H{sub 2}O, CO{sub 2} and CH{sub 4}, and to estimate enthalpies for these gases. For H{sub 2}, the P-T range of application is from 25 to 600 C and up tomore » 3,000 bars, and for CH{sub 4}, from 16 to 350 C and up to 500 bars. For H{sub 2}O and CO{sub 2}, two P-T ranges are considered: below 350C, up to 500 bars, and from 450 to 1,000 C, up to 1,000 bars. The method presented here is limited to the P-T range of the fitted experimental data, and cannot represent accurately P-V-T data close to the critical region. This virial equation treatment yields simple analytical expressions that are suitable for multicomponent equilibrium calculations. Examples of equilibrium calculations between aqueous and gas phases show that ideal mixing of real gases is a sufficient approximation for modeling boiling in geothermal and epithermal systems. However, non-ideal mixing has to be considered for aqueous-gas systems at pressures much higher than the saturation pressure of pure water.« less