title: Effect of Ambient Temperature on Total Organic Gas Speciation Profiles from Light-Duty Gasoline Vehicle Exhaust.
abstract: Total organic gases (TOG) emissions from motor vehicles include air toxic compounds and contribute to formation of ground-level ozone and secondary organic aerosol (SOA). These emissions are known to be affected by temperature; however previous studies have typically focused only on the temperature dependence of total emission factors and select toxic compounds. This study builds on the previous research by performing an evaluation of a comprehensive set of gas-phase organic compounds present in gasoline motor vehicle exhaust. A fleet of five vehicles using port fuel injection engine technology and running on E10 fuel was tested. Overall, three temperatures (0, 20, and 75 °F; or -18, -7, and 24 °C), two driving conditions (urban-FTP75 and aggressive driving-US06) and 161 compounds were evaluated; the emissions distributions were used to construct speciation profiles for each driving cycle and temperature. Overall, the speciation results indicated a significant increase in alkane and methane content, and decrease in alcohol, aldehyde and ketone content with decreasing temperature. These were verified using a statistical significance test. The fraction and composition of Mobile Source Air Toxics (MSATs) were significantly affected by temperature for both driving cycles. The ozone forming potentials of these profiles were evaluated using the maximum incremental reactivity (MIR) scale. Aromatic content was predicted to be a major driver behind the ozone forming potentials. Additionally, the decreasing ozone potential could be attributed to increased methane fractions with increasing temperature.
authors.affiliation: Department of Earth and Atmospheric Sciences, University of Houston , Houston, Texas 77004, United States.
authors.forename: Anirban
authors.initials: A
authors.lastname: Roy
authors.affiliation: United States Environmental Protection Agency's Office of Transportation and Air Quality, Ann Arbor, Michigan 48105, United States.
authors.forename: Darrell
authors.initials: D
authors.lastname: Sonntag
authors.affiliation: United States Environmental Protection Agency's Office of Transportation and Air Quality, Ann Arbor, Michigan 48105, United States.
authors.forename: Richard
authors.initials: R
authors.lastname: Cook
authors.affiliation: United States Environmental Protection Agency's Office of Transportation and Air Quality, Ann Arbor, Michigan 48105, United States.
authors.forename: Catherine
authors.initials: C
authors.lastname: Yanca
authors.affiliation: United States Environmental Protection Agency's Office of Transportation and Air Quality, Ann Arbor, Michigan 48105, United States.
authors.forename: Charles
authors.initials: C
authors.lastname: Schenk
authors.affiliation: Department of Earth and Atmospheric Sciences, University of Houston , Houston, Texas 77004, United States.
authors.forename: Yunsoo
authors.initials: Y
authors.lastname: Choi
mesh_terms: D000336:Aerosols; D000393:Air Pollutants; D005742:Gasoline; D018986:Motor Vehicles; D013696:Temperature; D001335:Vehicle Emissions
chemical_list: D000336:Aerosols; D000393:Air Pollutants; D005742:Gasoline; D001335:Vehicle Emissions