title: Direct and Indirect Measurements and Modeling of Methane Emissions in Indianapolis, Indiana.
abstract: This paper describes process-based estimation of CH4 emissions from sources in Indianapolis, IN and compares these with atmospheric inferences of whole city emissions. Emissions from the natural gas distribution system were estimated from measurements at metering and regulating stations and from pipeline leaks. Tracer methods and inverse plume modeling were used to estimate emissions from the major landfill and wastewater treatment plant. These direct source measurements informed the compilation of a methane emission inventory for the city equal to 29 Gg/yr (5% to 95% confidence limits, 15 to 54 Gg/yr). Emission estimates for the whole city based on an aircraft mass balance method and from inverse modeling of CH4 tower observations were 41 ± 12 Gg/yr and 81 ± 11 Gg/yr, respectively. Footprint modeling using 11 days of ethane/methane tower data indicated that landfills, wastewater treatment, wetlands, and other biological sources contribute 48% while natural gas usage and other fossil fuel sources contribute 52% of the city total. With the biogenic CH4 emissions omitted, the top-down estimates are 3.5-6.9 times the nonbiogenic city inventory. Mobile mapping of CH4 concentrations showed low level enhancement of CH4 throughout the city reflecting diffuse natural gas leakage and downstream usage as possible sources for the missing residual in the inventory.
authors.affiliation: Laboratory for Atmospheric Research, Washington State University , Pullman, Washington 99164, United States.
authors.forename: Brian K
authors.initials: BK
authors.lastname: Lamb
authors.affiliation: Departments of Chemistry, and Earth, Atmospheric and Planetary Sciences, Purdue University , West Lafayette, Indiana 47907, United States.
authors.forename: Maria O L
authors.initials: MO
authors.lastname: Cambaliza
authors.affiliation: Department of Meteorology, The Pennsylvania State University , University Park, Pennsylvania 16802, United States.
authors.forename: Kenneth J
authors.initials: KJ
authors.lastname: Davis
authors.affiliation: Laboratory for Atmospheric Research, Washington State University , Pullman, Washington 99164, United States.
authors.forename: Steven L
authors.initials: SL
authors.lastname: Edburg
authors.affiliation: GHD, Niagara Falls, New York 14304, United States.
authors.forename: Thomas W
authors.initials: TW
authors.lastname: Ferrara
authors.affiliation: Aerodyne Research, Inc., Billerica, Massachusetts 01821, United States.
authors.forename: Cody
authors.initials: C
authors.lastname: Floerchinger
authors.affiliation: Departments of Chemistry, and Earth, Atmospheric and Planetary Sciences, Purdue University , West Lafayette, Indiana 47907, United States.
authors.forename: Alexie M F
authors.initials: AM
authors.lastname: Heimburger
authors.affiliation: Aerodyne Research, Inc., Billerica, Massachusetts 01821, United States.
authors.forename: Scott
authors.initials: S
authors.lastname: Herndon
authors.affiliation: Department of Meteorology, The Pennsylvania State University , University Park, Pennsylvania 16802, United States.
authors.forename: Thomas
authors.initials: T
authors.lastname: Lauvaux
authors.affiliation: Departments of Chemistry, and Earth, Atmospheric and Planetary Sciences, Purdue University , West Lafayette, Indiana 47907, United States.
authors.forename: Tegan
authors.initials: T
authors.lastname: Lavoie
authors.affiliation: Environmental Defense Fund, Austin, Texas 78701, United States.
authors.forename: David R
authors.initials: DR
authors.lastname: Lyon
authors.affiliation: Department of Meteorology, The Pennsylvania State University , University Park, Pennsylvania 16802, United States.
authors.forename: Natasha
authors.initials: N
authors.lastname: Miles
authors.affiliation: National Institute for Standards and Technology, Gaithersburg, Maryland 20899, United States.
authors.forename: Kuldeep R
authors.initials: KR
authors.lastname: Prasad
authors.affiliation: Department of Meteorology, The Pennsylvania State University , University Park, Pennsylvania 16802, United States.
authors.forename: Scott
authors.initials: S
authors.lastname: Richardson
authors.affiliation: Aerodyne Research, Inc., Billerica, Massachusetts 01821, United States.
authors.forename: Joseph Robert
authors.initials: JR
authors.lastname: Roscioli
authors.affiliation: Departments of Chemistry, and Earth, Atmospheric and Planetary Sciences, Purdue University , West Lafayette, Indiana 47907, United States.
authors.forename: Olivia E
authors.initials: OE
authors.lastname: Salmon
authors.affiliation: Departments of Chemistry, and Earth, Atmospheric and Planetary Sciences, Purdue University , West Lafayette, Indiana 47907, United States.
authors.forename: Paul B
authors.initials: PB
authors.lastname: Shepson
authors.affiliation: School of Aviation & Transportation Technology, Purdue University , West Lafayette, Indiana 47907, United States.
authors.forename: Brian H
authors.initials: BH
authors.lastname: Stirm
authors.affiliation: National Institute for Standards and Technology, Gaithersburg, Maryland 20899, United States.
authors.forename: James
authors.initials: J
authors.lastname: Whetstone
mesh_terms: D000393:Air Pollutants; D007196:Indiana; D008697:Methane; D059206:Natural Gas; D064091:Waste Disposal Facilities
chemical_list: D000393:Air Pollutants; D059206:Natural Gas; D008697:Methane