title: Hydrogen Isotopic Composition of Arctic and Atmospheric CH4Determined by a Portable Near-Infrared Cavity Ring-Down Spectrometer with a Cryogenic Pre-Concentrator.
abstract: In this study, near-infrared continuous wave cavity ring-down spectroscopy was applied to the measurement of the δ2H of methane (CH4). The cavity ring-down spectrometer (CRDS) system consisted of multiple DFB laser diodes to optimize selection of spectral line pairs. By rapidly switching measurements between spectral line peaks and the baseline regions, the long-term instrumental drift was minimized, substantially increasing measurement precision. The CRDS system coupled with a cryogenic pre-concentrator measured the δ2H of terrestrial atmospheric CH4from 3 standard liters of air with a precision of ±1.7‰. The rapidity with which both C and H isotopic measurements of CH4can be made with the CRDS will enable hourly monitoring of diurnal variations in terrestrial atmospheric CH4signatures that can be used to increase the resolution of global climate models for the CH4cycle. Although the current instrument is not capable of measuring the δ2H of 10 ppbv of martian CH4, current technology does exist that could make this feasible for future spaceflight missions. As biological and abiotic CH4sources have overlapping carbon isotope signatures, dual-element (C and H) analysis is key to reliable differentiation of these sources. Such an instrument package would therefore offer improved ability to determine whether or not the CH4recently detected in the martian atmosphere is biogenic in origin. Key Words: Arctic-Hydrogen isotopes-Atmospheric CH4-CRDS-Laser. Astrobiology 16, 787-797.
authors.affiliation: Department of Geosciences, Princeton University , Princeton, New Jersey, USA.
authors.forename: Y
authors.initials: Y
authors.lastname: Chen
authors.affiliation: Department of Chemistry, University of Virginia , Charlottesville, Virginia, USA.
authors.forename: Kevin K
authors.initials: KK
authors.lastname: Lehmann
authors.affiliation: Department of Geological Sciences, Indiana University , Bloomington, Indiana, USA.
authors.forename: Y
authors.initials: Y
authors.lastname: Peng
authors.affiliation: Department of Geological Sciences, Indiana University , Bloomington, Indiana, USA.
authors.forename: L M
authors.initials: LM
authors.lastname: Pratt
authors.affiliation: School of Public and Environmental Affairs, Indiana University , Bloomington, Indiana, USA.
authors.forename: J R
authors.initials: JR
authors.lastname: White
authors.affiliation: Department of Geological Sciences, Indiana University , Bloomington, Indiana, USA.
authors.forename: S B
authors.initials: SB
authors.lastname: Cadieux
authors.affiliation: Department of Earth Sciences, University of Toronto , Toronto, Canada .
authors.forename: B
authors.initials: B
authors.lastname: Sherwood Lollar
authors.affiliation: Department of Earth Sciences, University of Toronto , Toronto, Canada .
authors.forename: G
authors.initials: G
authors.lastname: Lacrampe-Couloume
authors.affiliation: Department of Geosciences, Princeton University , Princeton, New Jersey, USA.
authors.forename: T C
authors.initials: TC
authors.lastname: Onstott
mesh_terms: D001110:Arctic Regions; D001272:Atmosphere / Q000737:chemistry*; D002247:Carbon Isotopes / Q000737:chemistry*; D005240:Feasibility Studies; D005615:Freezing; D006859:Hydrogen / Q000032:analysis*; D007834:Lasers; D008697:Methane / Q000737:chemistry*; D019265:Spectroscopy, Near-Infrared / Q000295:instrumentation* / Q000379:methods
chemical_list: D002247:Carbon Isotopes; D006859:Hydrogen; D008697:Methane