title: Vehicle Emissions as an Important Urban Ammonia Source in the United States and China.
abstract: Ammoniated aerosols are important for urban air quality, but emissions of the key precursor NH3are not well quantified. Mobile laboratory observations are used to characterize fleet-integrated NH3emissions in six cities in the U.S. and China. Vehicle NH3:CO2emission ratios in the U.S. are similar between cities (0.33-0.40 ppbv/ppmv, 15% uncertainty) despite differences in fleet composition, climate, and fuel composition. While Beijing, China has a comparable emission ratio (0.36 ppbv/ppmv) to the U.S. cities, less developed Chinese cities show higher emission ratios (0.44 and 0.55 ppbv/ppmv). If the vehicle CO2inventories are accurate, NH3emissions from U.S. vehicles (0.26 ± 0.07 Tg/yr) are more than twice those of the National Emission Inventory (0.12 Tg/yr), while Chinese NH3vehicle emissions (0.09 ± 0.02 Tg/yr) are similar to a bottom-up inventory. Vehicle NH3emissions are greater than agricultural emissions in counties containing near half of the U.S. population and require reconsideration in urban air quality models due to their colocation with other aerosol precursors and the uncertainties regarding NH3losses from upwind agricultural sources. Ammonia emissions in developing cities are especially important because of their high emission ratios and rapid motorizations.
authors.affiliation: Department of Civil and Environmental Engineering, Princeton University , Princeton, New Jersey 08544, United States.|Center for Mid-Infrared Technologies for Health and the Environment, NSF-ERC, Princeton, New Jersey 08544, United States.
authors.forename: Kang
authors.initials: K
authors.lastname: Sun
authors.affiliation: Department of Civil and Environmental Engineering, Princeton University , Princeton, New Jersey 08544, United States.|Center for Mid-Infrared Technologies for Health and the Environment, NSF-ERC, Princeton, New Jersey 08544, United States.
authors.forename: Lei
authors.initials: L
authors.lastname: Tao
authors.affiliation: Department of Civil and Environmental Engineering, Princeton University , Princeton, New Jersey 08544, United States.|Center for Mid-Infrared Technologies for Health and the Environment, NSF-ERC, Princeton, New Jersey 08544, United States.
authors.forename: David J
authors.initials: DJ
authors.lastname: Miller
authors.affiliation: Department of Civil and Environmental Engineering, Princeton University , Princeton, New Jersey 08544, United States.|Center for Mid-Infrared Technologies for Health and the Environment, NSF-ERC, Princeton, New Jersey 08544, United States.
authors.forename: Da
authors.initials: D
authors.lastname: Pan
authors.affiliation: Department of Civil and Environmental Engineering, Princeton University , Princeton, New Jersey 08544, United States.|Center for Mid-Infrared Technologies for Health and the Environment, NSF-ERC, Princeton, New Jersey 08544, United States.
authors.forename: Levi M
authors.initials: LM
authors.lastname: Golston
authors.affiliation: Department of Civil and Environmental Engineering, Princeton University , Princeton, New Jersey 08544, United States.|Center for Mid-Infrared Technologies for Health and the Environment, NSF-ERC, Princeton, New Jersey 08544, United States.
authors.forename: Mark A
authors.identifier: 0000-0003-2302-9554
authors.initials: MA
authors.lastname: Zondlo
authors.affiliation: Department of Civil and Environmental Engineering, Rice University , Houston, Texas 77005, United States.
authors.forename: Robert J
authors.initials: RJ
authors.lastname: Griffin
authors.affiliation: Department of Civil and Environmental Engineering, Rice University , Houston, Texas 77005, United States.
authors.forename: H W
authors.initials: HW
authors.lastname: Wallace
authors.affiliation: Department of Civil and Environmental Engineering, Rice University , Houston, Texas 77005, United States.
authors.forename: Yu Jun
authors.initials: YJ
authors.lastname: Leong
authors.affiliation: Chemistry and Dynamics Branch, NASA Langley Research Center, Hampton, Virginia 23681, United States.
authors.forename: M Melissa
authors.initials: MM
authors.lastname: Yang
authors.affiliation: Nanjing P&Y Environmental Technology Co., Ltd., Nanjing, Jiangsu 210014, China.
authors.forename: Yan
authors.initials: Y
authors.lastname: Zhang
authors.affiliation: Department of Civil and Environmental Engineering, Princeton University , Princeton, New Jersey 08544, United States.|Woodrow Wilson School of Public and International Affairs, Princeton University , Princeton, New Jersey 08544, United States.
authors.forename: Denise L
authors.identifier: 0000-0003-3479-1798
authors.initials: DL
authors.lastname: Mauzerall
authors.affiliation: State Key Laboratory for Environmental Simulation and Pollution Control, College of Environmental Sciences and Engineering, Peking University , Beijing 100871, China.
authors.forename: Tong
authors.initials: T
authors.lastname: Zhu
mesh_terms: D000336:Aerosols; D000393:Air Pollutants; D000641:Ammonia; D002681:China; D002947:Cities; D004784:Environmental Monitoring; D014481:United States; D001335:Vehicle Emissions
chemical_list: D000336:Aerosols; D000393:Air Pollutants; D001335:Vehicle Emissions; D000641:Ammonia