title: Ethylene glycol emissions from on-road vehicles.
abstract: Ethylene glycol (HOCH2CH2OH), used as engine coolant for most on-road vehicles, is an intermediate volatility organic compound (IVOC) with a high Henry's law coefficient. We present measurements of ethylene glycol (EG) vapor in the Caldecott Tunnel near San Francisco, using a proton transfer reaction mass spectrometer (PTR-MS). Ethylene glycol was detected at mass-to-charge ratio 45, usually interpreted as solely coming from acetaldehyde. EG concentrations in bore 1 of the Caldecott Tunnel, which has a 4% uphill grade, were characterized by infrequent (approximately once per day) events with concentrations exceeding 10 times the average concentration, likely from vehicles with malfunctioning engine coolant systems. Limited measurements in tunnels near Houston and Boston are not conclusive regarding the presence of EG in sampled air. Previous PTR-MS measurements in urban areas may have overestimated acetaldehyde concentrations at times due to this interference by ethylene glycol. Estimates of EG emission rates from the Caldecott Tunnel data are unrealistically high, suggesting that the Caldecott data are not representative of emissions on a national or global scale. EG emissions are potentially important because they can lead to the formation of secondary organic aerosol following oxidation in the atmospheric aqueous phase.
authors.affiliation: †Department of Chemistry, University of Massachusetts, Amherst, Massachusetts 01003, United States.
authors.forename: Ezra C
authors.initials: EC
authors.lastname: Wood
authors.affiliation: ‡Department of Chemistry and Biochemistry, Montana State University, Bozeman, Montana 59717, United States.
authors.forename: W Berk
authors.initials: WB
authors.lastname: Knighton
authors.affiliation: §Aerodyne Research, Inc., Billerica, Massachusetts 01821, United States.
authors.forename: Ed C
authors.initials: EC
authors.lastname: Fortner
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: Timothy B
authors.initials: TB
authors.lastname: Onasch
authors.affiliation: §Aerodyne Research, Inc., Billerica, Massachusetts 01821, United States.
authors.forename: Jonathan P
authors.initials: JP
authors.lastname: Franklin
authors.affiliation: §Aerodyne Research, Inc., Billerica, Massachusetts 01821, United States.
authors.forename: Douglas R
authors.initials: DR
authors.lastname: Worsnop
authors.forename: Timothy R
authors.initials: TR
authors.lastname: Dallmann
authors.forename: Drew R
authors.initials: DR
authors.lastname: Gentner
authors.forename: Allen H
authors.initials: AH
authors.lastname: Goldstein
authors.forename: Robert A
authors.initials: RA
authors.lastname: Harley
mesh_terms: D000336:Aerosols / Q000032:analysis; D000393:Air Pollutants / Q000032:analysis*; D001900:Boston; D004784:Environmental Monitoring / Q000379:methods*; D019855:Ethylene Glycol / Q000032:analysis*; D018986:Motor Vehicles; D012495:San Francisco; D013781:Texas; D001335:Vehicle Emissions / Q000032:analysis*; D055549:Volatile Organic Compounds / Q000032:analysis
chemical_list: D000336:Aerosols; D000393:Air Pollutants; D001335:Vehicle Emissions; D055549:Volatile Organic Compounds; D019855:Ethylene Glycol