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Title: Investigating semi-volatile organic compound emissions from light-duty vehicles

Principal Investigator / Author(s): Goldstein, Allen

Contractor: UC Berkeley

Contract Number: 12-318

Research Program Area: Emissions Monitoring & Control

Topic Areas: Mobile Sources & Fuels


The formation of secondary organic aerosol (SOA) in the atmosphere is a complex and relatively poorly understood subject that is the subject much research. Recent research suggested that emissions from late model light-duty gasoline vehicles (LDGVs) might be disproportionate contributors to SOA formation because of differences in SOA yields compared to older model year vehicles. The objective of this project was to investigate the SOA formation from a small test fleet of forward-looking late model LDGVs by conducting vehicle emissions testing in conjunction with smog chamber experiments and data analysis. Results from this project indicate that contrary to earlier conclusions/assumptions, emissions from later model year LDGVs do not contain a more potent mix of SOA precursors compared to older model year vehicles, when smog chamber experiments are conducted under similar ratios of volatile organic compounds and oxides of nitrogen (VOCs- NOX ratios), and, that SOA formation will be reduced as the fleet turns over to newer model year LDGVs. However, results also indicate that SOA production is influenced by VOC:NOX ratios, and this suggests that SOA formation may actually increase in future years as NOX emissions are reduced, and some regions shift from being high NOX regions to low NOX regions.

In a follow-up study (14-345, see link in the upper right reports box), SOA formation from LDGV exhaust was investigated using a Potential Aerosol Mass (PAM) oxidation flow reactor. If one accounts variable gas/particle partitioning, our results indicate similar effective SOA yields across different vehicle classes, consistent with results of smog chamber experiments. Therefore, the tightening of emissions standards effectively reduces SOA production from gasoline vehicle exhaust.


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

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