Research Projects

Project at a Glance

Title: Determination of the contributions of light duty and heavy duty vehicle emissions to ambient particles in California.

Principal Investigator / Author(s): Prather, Kimberly A

Contractor: UC San Diego

Contract Number: 00-331

Research Program Area: Atmospheric Processes, Emissions Monitoring & Control

Topic Areas: Field Studies, Mobile Sources & Fuels


A new approach for PM source apportionment has been developed and successfully tested, using meteorological, gas phase, and single particle source signatures to identify and apportion ambient particles in California. A central component of these studies involves using aerosol time-of-flight mass spectrometry (ATOFMS), a technique which analyzes the size and chemical composition of single particles in real-time, to determine the size-resolved mass spectral source signatures of the particulate exhaust emissions from heavy duty diesel vehicles (HDDV) and gasoline powered light duty vehicles (LDV) that can be used for ambient source apportionment. The source signatures were measured by directly sampling PM emissions from multiple vehicles operating on different driving cycles while on a chassis dynamometer. Differences between HDDV and LDV source seeds are discussed. The second and final phase of this project involved sampling ambient particles inside a tunnel and alongside a major freeway. In the freeway study, a high fraction (70-85%) of ambient particles were shown to match the dynamometer source seeds, showing the dynamometer seeds are indeed representative of “real-world” emissions. The difference signatures from LDV and HDDV allow for differentiation of ambient particles from multiple sources including vehicles, biomass, and meat cooking. The established ATOFMS signature libraries for HDDV and LDV exhaust particles will be used in future ATOFMS apportionment studies which will detail the fraction of vehicle emissions in particulate matter in ambient air throughout California.


For questions regarding this research project, including available data and progress status, contact: Heather Choi at (916) 322-3893

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