title: Primary gas- and particle-phase emissions and secondary organic aerosol production from gasoline and diesel off-road engines.
abstract: Dilution and smog chamber experiments were performed to characterize the primary emissions and secondary organic aerosol (SOA) formation from gasoline and diesel small off-road engines (SOREs). These engines are high emitters of primary gas- and particle-phase pollutants relative to their fuel consumption. Two- and 4-stroke gasoline SOREs emit much more (up to 3 orders of magnitude more) nonmethane organic gases (NMOGs), primary PM and organic carbon than newer on-road gasoline vehicles (per kg of fuel burned). The primary emissions from a diesel transportation refrigeration unit were similar to those of older, uncontrolled diesel engines used in on-road vehicles (e.g., premodel year 2007 heavy-duty diesel trucks). Two-strokes emitted the largest fractional (and absolute) amount of SOA precursors compared to diesel and 4-stroke gasoline SOREs; however, 35-80% of the NMOG emissions from the engines could not be speciated using traditional gas chromatography or high-performance liquid chromatography. After 3 h of photo-oxidation in a smog chamber, dilute emissions from both 2- and 4-stroke gasoline SOREs produced large amounts of semivolatile SOA. The effective SOA yield (defined as the ratio of SOA mass to estimated mass of reacted precursors) was 2-4% for 2- and 4-stroke SOREs, which is comparable to yields from dilute exhaust from older passenger cars and unburned gasoline. This suggests that much of the SOA production was due to unburned fuel and/or lubrication oil. The total PM contribution of different mobile source categories to the ambient PM burden was calculated by combining primary emission, SOA production and fuel consumption data. Relative to their fuel consumption, SOREs are disproportionately high total PM sources; however, the vastly greater fuel consumption of on-road vehicles renders them (on-road vehicles) the dominant mobile source of ambient PM in the Los Angeles area.
authors.affiliation: Center for Atmospheric Particle Studies, Carnegie Mellon University , Pittsburgh, Pennsylvania 15213, United States.
authors.forename: Timothy D
authors.initials: TD
authors.lastname: Gordon
authors.forename: Daniel S
authors.initials: DS
authors.lastname: Tkacik
authors.forename: Albert A
authors.initials: AA
authors.lastname: Presto
authors.forename: Mang
authors.initials: M
authors.lastname: Zhang
authors.forename: Shantanu H
authors.initials: SH
authors.lastname: Jathar
authors.forename: Ngoc T
authors.initials: NT
authors.lastname: Nguyen
authors.forename: John
authors.initials: J
authors.lastname: Massetti
authors.forename: Tin
authors.initials: T
authors.lastname: Truong
authors.forename: Pablo
authors.initials: P
authors.lastname: Cicero-Fernandez
authors.forename: Christine
authors.initials: C
authors.lastname: Maddox
authors.forename: Paul
authors.initials: P
authors.lastname: Rieger
authors.forename: Sulekha
authors.initials: S
authors.lastname: Chattopadhyay
authors.forename: Hector
authors.initials: H
authors.lastname: Maldonado
authors.forename: M Matti
authors.initials: MM
authors.lastname: Maricq
authors.forename: Allen L
authors.initials: AL
authors.lastname: Robinson
mesh_terms: D000336:Aerosols / Q000032:analysis*; D005740:Gases / Q000737:chemistry*; D005742:Gasoline / Q000032:analysis*; D015141:Los Angeles; D008697:Methane / Q000032:analysis; D015541:Off-Road Motor Vehicles; D009930:Organic Chemicals / Q000032:analysis*; D052638:Particulate Matter / Q000737:chemistry*; D012905:Smog / Q000032:analysis; D001335:Vehicle Emissions / Q000032:analysis
chemical_list: D000336:Aerosols; D005740:Gases; D005742:Gasoline; D009930:Organic Chemicals; D052638:Particulate Matter; D012905:Smog; D001335:Vehicle Emissions; D008697:Methane