American Association for Aerosol Research - Abstract Submission

AAAR 32nd Annual Conference
September 30 - October 4, 2013
Oregon Convention Center
Portland, Oregon, USA

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Secondary Aerosol Production from Modern Diesel and Gasoline Light Duty Vehicles

Stephen Platt, Imad El Haddad, Simone Pieber, Alessandro Zardini, Ricardo Suarez-Bertoa, Jay Slowik, Ru-Jin Huang, Stig Hellebust, Brice Temime-Roussel, Nicolas Marchand, Luka Drinovec, Grisa Mocnik, Covadonga Astorga, Urs Baltensperger, ANDRE PRÉVÔT, Paul Scherrer Institute

     Abstract Number: 93
     Working Group: Aerosol Chemistry

Abstract
On road vehicles are a significant source of particulate matter (PM), particularly in urban areas where population densities therefore and health impacts are higher. Under ambient conditions, most vehicular PM is likely secondary, produced via atmospheric reactions of volatile organic compounds (VOCs) from the exhaust. How this secondary PM production varies by vehicle type (e.g. diesel or gasoline, vehicle legislative standards etc) must be understood to improve atmospheric model predictions, inform policymakers and the general public, and ultimately reduce the health impacts of internal combustion vehicles.

Unfortunately very little information on the secondary aerosol production potential (SAPP) of vehicle exhaust is available. Meanwhile, recent ambient measurements combined with fuel consumption data (Bahreini et al., 2012) and estimations using raw fuels (Gentner et al., 2012), gave conflicting results as to whether diesel or gasoline vehicle emissions have a higher SAPP. Furthermore, the effect of low temperature ambient conditions (already known to increase primary PM and VOC emissions), or ambient relative humidity on vehicular SAPP is poorly constrained.

We report results from novel smog chamber experiments characterizing primary and secondary exhaust emissions from diesel and gasoline passenger cars (Euro 5) during the New European Driving Cycle. Primary emissions were diluted to atmospherically-relevant concentrations and injected into the chamber. Formation and aging of secondary products was initiated by OH photochemistry. Experiments were performed at 263K and 288K and at 40% and >90% relative humidity (RH).

VOC emission was generally lower for diesel vehicles, resulting in lower SAPP. Cold ambient conditions increased VOC emission and SAPP significantly for the gasoline vehicles studied but not for diesel vehicles. Increasing RH was also observed to increase SAPP.