Emissions from motor vehicles are a significant source of fine particulate matter (PM) and gaseous pollutants in urban environments. Few studies have characterized both gaseous and PM emissions from individual in-use vehicles under real-world driving conditions. Here we describe chase vehicle studies in which Received 27 February 2003; accepted 29 March 2004. This work was supported in part by the New York State Energy Research and Development Authority (NYSERDA), contract # 4918ERT-ERES99; the US Environmental Protection Agency (EPA), cooperative agreement # R828060010; and New York State Department of Environmental Conservation (NYS DEC), contract # C004210. Although the research described in this article has been funded in part by US EPA, it has not been subjected to the Agency's required peer and policy review and therefore does not necessary reflect the views of the Agency, and no official endorsement should be inferred. The authors thank the MTA for their cooperation, including Chris Bush for providing bus fleet information and Dana Lowell for help in organizing the logistics of the Fall 2000 campaign, the NYS DEC for providing drivers during the chase experiments, and Queens College for logistical support during the Summer 2001 campaign. The TILDAS scientists on-board the mobile laboratory, particularly Joanne Shorter and Mark Zahniser, are acknowledged for their assistance throughout the two phases of this study. Thanks also go to Jay Slowik and Leah Williams for help with laboratory soot experiments, Tim Onasch for assistance with the development of data analysis programs, and Paul Ziemann for useful discussions about organic mass spectral analysis. P. J. Silva thanks the Camille and Henry Dreyfus Foundation for Support. D. A. Ghertner thanks Robert Harriss for providing funding for his involvement in this project.Address correspondence to Manjula R. Canagaratna, Center for Aerosol and Cloud Chemistry and Center for Atmospheric and Environmental Chemistry, Aerodyne Research Inc., 45 Manning Road, Billerica, MA 01821, USA. E-mail: mrcana@aerodyne.com on-road emissions from individual vehicles were measured in real time within seconds of their emission. This work uses an Aerodyne aerosol mass spectrometer (AMS) to provide size-resolved and chemically resolved characterization of the nonrefractory portion of the emitted PM; refractory materials such as elemental carbon (EC) were not measured in this study. The AMS, together with other gas-phase and particle instrumentation, was deployed on the Aerodyne Research Inc. (ARI) mobile laboratory, which was used to "chase" the target vehicles. Tailpipe emission indices of the targeted vehicles were obtained by referencing the measured nonrefractory particulate mass loading to the instantaneous CO 2 measured simultaneously in the plume. During these studies, nonrefractory PM 1.0 (NRPM 1 ) emission indices for a representative fraction of the New York City Metropolitan Transit Authority (MTA) bus fleet were determined. Diesel bus emissions ranged from 0.10 g NRPM 1...

In August 2001, the Aerodyne Mobile Laboratory simultaneously measured NO, NO2, and CO2 within 350 m of a taxiway and 550 m of a runway at John F. Kennedy Airport. The meteorological conditions were such that taxi and takeoff plumes from individual aircraft were clearly resolved against background levels. NO and NO2 concentrations were measured with 1 s time resolution using a dual tunable infrared laser differential absorption spectroscopy instrument, utilizing an astigmatic multipass Herriott cell. The CO2 measurements were also obtained at 1 s time resolution using a commercial non-dispersive infrared absorption instrument. Plumes were measured from over 30 individual planes, ranging from turbo props to jumbo jets. NOx emission indices were determined by examining the correlation between NOx (NO + NO2) and CO2 during the plume measurements. Several aircraft tail numbers were unambiguously identified, allowing those specific airframe/engine combinations to be determined. The resulting NOx emission indices from positively identified in-service operating airplanes are compared with the published International Civil Aviation Organization engine certification test database collected on new engines in certification test cells.