Gas- and particle-phase primary emissions from in-use, on-road gasoline and diesel vehicles

Andrew A. May, Ngoc T. Nguyen, Albert A. Presto, Timothy D. Gordon, Eric M. Lipsky, Mrunmayi Karve, Alváro Gutierrez, William H. Robertson, Mang Zhang, Christopher Brandow, Oliver Chang, Shiyan Chen, Pablo Cicero-Fernandez, Lyman Dinkins, Mark Fuentes, Shiou Mei Huang, Richard Ling, Jeff Long, Christine Maddox, John MassettiEileen McCauley, Antonio Miguel, Kwangsam Na, Richard Ong, Yanbo Pang, Paul Rieger, Todd Sax, Tin Truong, Thu Vo, Sulekha Chattopadhyay, Hector Maldonado, M. Matti Maricq, Allen L. Robinson

Research output: Contribution to journalArticlepeer-review

197 Scopus citations


Tailpipe emissions from sixty-four unique light-duty gasoline vehicles (LDGVs) spanning model years 1987-2012, two medium-duty diesel vehicles and three heavy-duty diesel vehicles with varying levels of aftertreatment were characterized at the California Air Resources Board Haagen-Smit and Heavy-Duty Engine Testing Laboratories. Each vehicle was tested on a chassis dynamometer using a constant volume sampler, commercial fuels and standard duty cycles. Measurements included regulated pollutants such as carbon monoxide (CO), total hydrocarbons (THC), nitrogen oxides (NOx), and particulate matter (PM). Off-line analyses were performed to speciate gas- and particle-phase emissions. The data were used to investigate trends in emissions with vehicle age and to quantify the effects of different aftertreatment technologies on diesel vehicle emissions (e.g., with and without a diesel particulate filter). On average, newer LDGVs that met the most recent emissions standards had substantially lower emissions of regulated gaseous pollutants (CO, THC and NOx) than older vehicles. For example, THC emissions from the median LDGV that met the LEV2 standard was roughly a factor of 10 lower than the median pre-LEV vehicle; there were also substantial reductions in NOx (factor of ~100) and CO (factor of ~10) emissions from pre-LEV to LEV2 vehicles. However, reductions in LDGV PM mass emissions were much more modest. For example, PM emission from the median LEV2 vehicle was only a factor of three lower than the median pre-LEV vehicle, mainly due to the reductions in organic carbon emissions. In addition, LEV1 and LEV2 LDGVs had similar PM emissions. Catalyzed diesel particulate filters reduced CO, THC and PM emissions from HDDVs by one to two orders of magnitude. Comprehensive organic speciation was performed to quantify priority air toxic emissions and to estimate the secondary organic aerosol (SOA) formation potential. The data suggest that the SOA production from cold-start LDGVs exhaust will likely exceed primary PM emissions from LDGVs and could potentially exceed SOA formation from on-road diesel vehicles.

Original languageEnglish (US)
Pages (from-to)247-260
Number of pages14
JournalAtmospheric Environment
StatePublished - May 2014

All Science Journal Classification (ASJC) codes

  • General Environmental Science
  • Atmospheric Science


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