AAAR 32nd Annual Conference
September 30 - October 4, 2013
Oregon Convention Center
Portland, Oregon, USA
Abstract View
Secondary Organic Aerosol Formation from Gasoline and Diesel Vehicle Emissions Using a New Flow Reactor
JAY SLOWIK, Ru-Jin Huang, Stephen Platt, Simone Pieber, Imad El Haddad, Alessandro Zardini, Ricardo Suarez-Bertoa, Stig Hellebust, Brice Temime-Roussel, Nicolas Marchand, Urs Baltensperger, Covadonga Astorga, Andre Prévôt, Paul Scherrer Institute
Abstract Number: 493 Working Group: Urban Aerosols
Abstract Vehicle emissions significantly impact air quality, especially in urban areas with high traffic flow. Many previous studies have investigated direct emissions of vehicle trace gases and particulate matter (PM), although recent studies indicate that the secondary organic aerosol (SOA) formation dominates the total vehicle PM burden. Nevertheless, relevant studies of SOA formation from vehicle emissions remain very scarce. Flow reactor systems provide a highly oxidizing environment that simulates atmospheric oxidation processes occurring on the order of one to several days using a reaction time of only a few minutes. This provides time-resolved measurements of the secondary aerosol production potential that is particularly useful for assessing vehicle emissions as a function of engine load.
Here we present initial measurements of SOA formation potential from modern (Euro 5) gasoline and diesel cars using a new flow reactor system conducted at the vehicle test facilities at the European Commission Joint Research Centre (Ispra, Italy). Vehicle exhaust emissions from a New European Driving Cycle were sampled either i) directly into the flow tube from a constant volume sampler (CVS) or ii) first into a smog chamber and then through the flow reactor. Within the reactor, emissions are exposed to OH radicals generated from either ozone or HONO-based sources. The reactor output is sampled by a movable sampling probe, enabling OH concentration and reaction time to be varied independently while maintaining the same OH exposure (OH exposure = concentration x time). Particle and gas-phase composition were quantified using a high-resolution time-of-flight aerosol mass spectrometer (HR-ToF-AMS) and a time-of-flight proton transfer reaction mass spectrometer (PTRTOF-MS), respectively. The amount and composition of SOA was observed to depend on both vehicle type and driving cycle phase.