title: Airborne Ethane Observations in the Barnett Shale: Quantification of Ethane Flux and Attribution of Methane Emissions.
abstract: We present high time resolution airborne ethane (C2H6) and methane (CH4) measurements made in March and October 2013 as part of the Barnett Coordinated Campaign over the Barnett Shale formation in Texas. Ethane fluxes are quantified using a downwind flight strategy, a first demonstration of this approach for C2H6. Additionally, ethane-to-methane emissions ratios (C2H6:CH4) of point sources were observationally determined from simultaneous airborne C2H6 and CH4 measurements during a survey flight over the source region. Distinct C2H6:CH4 × 100% molar ratios of 0.0%, 1.8%, and 9.6%, indicative of microbial, low-C2H6 fossil, and high-C2H6 fossil sources, respectively, emerged in observations over the emissions source region of the Barnett Shale. Ethane-to-methane correlations were used in conjunction with C2H6 and CH4 fluxes to quantify the fraction of CH4 emissions derived from fossil and microbial sources. On the basis of two analyses, we find 71-85% of the observed methane emissions quantified in the Barnett Shale are derived from fossil sources. The average ethane flux observed from the studied region of the Barnett Shale was 6.6 ± 0.2 × 10(3) kg hr(-1) and consistent across six days in spring and fall of 2013.
authors.affiliation: †Atmospheric, Oceanic, and Space Sciences, University of Michigan, Ann Arbor, Michigan 48109, United States.
authors.forename: Mackenzie L
authors.initials: ML
authors.lastname: Smith
authors.affiliation: †Atmospheric, Oceanic, and Space Sciences, University of Michigan, Ann Arbor, Michigan 48109, United States.
authors.forename: Eric A
authors.initials: EA
authors.lastname: Kort
authors.affiliation: ‡CIRES, University of Colorado, Boulder, Colorado 80309, United States.|§NOAA Earth System Research Laboratory, Boulder, Colorado 80305, United States.
authors.forename: Anna
authors.initials: A
authors.lastname: Karion
authors.affiliation: ‡CIRES, University of Colorado, Boulder, Colorado 80309, United States.|§NOAA Earth System Research Laboratory, Boulder, Colorado 80305, United States.
authors.forename: Colm
authors.initials: C
authors.lastname: Sweeney
authors.affiliation: ∥Aerodyne Research, Inc., Billerica, Massachusetts 01821, United States.
authors.forename: Scott C
authors.initials: SC
authors.lastname: Herndon
authors.affiliation: ∥Aerodyne Research, Inc., Billerica, Massachusetts 01821, United States.
authors.forename: Tara I
authors.initials: TI
authors.lastname: Yacovitch
mesh_terms: D000393:Air Pollutants / Q000032:analysis*; D003198:Computer Simulation; D004980:Ethane / Q000032:analysis*; D005579:Fossil Fuels; D019015:Geologic Sediments / Q000737:chemistry*; D008697:Methane / Q000032:analysis*; D013781:Texas
chemical_list: D000393:Air Pollutants; D005579:Fossil Fuels; D004980:Ethane; D008697:Methane