AAAR 31st Annual Conference
October 8-12, 2012
Hyatt Regency Minneapolis
Minneapolis, Minnesota, USA
Abstract View
Comparing Primary and Secondary Particulate Matter from On-Road Sources: Gasoline vs. Diesel Vehicles
TIMOTHY GORDON, Albert A. Presto, Ngoc T. Nguyen, Allen Robinson, Hector Maldonado, Sulekha Chattopadhyay, Alvaro Gutierrez, William Robertson, Mang Zhang, Matti Maricq, Eric Lipsky, Carnegie Mellon University
Abstract Number: 641 Working Group: Urban Aerosols
Abstract Bahreini et al. (2012) recently reported that gasoline vehicle emissions are responsible for a much greater fraction of the secondary organic aerosol (SOA) in Los Angeles than diesel emissions. This conclusion was based on airborne and ground-based ambient measurements, and while the data are suggestive, it is difficult to link ambient conditions to specific sources without direct measurements of the emissions from those sources. Synthesizing the results from a large, multi-year study, our report compares the measured primary and secondary particulate matter (PM) from heavy-duty and light duty diesel vehicles (HDDV and LDDV) with that from light duty gasoline vehicles (LDGV).
Three different HDDV with and without aftertreatment were operated on a chassis dynamometer at the California Air Resources Board over a range of driving cycles and fuels. LDDV and LDGV were driven on a chassis dynamometer following the California Unified Cycle. The two LDDV were fueled with ULSD and biodiesel. Fifteen LDGV were tested, spanning a range of model years and emissions control standards (pre-LEV, LEV I and LEV II).
The gas- and particulate-phase emissions were characterized by collecting samples from a constant volume sampling system. Tenax sorbent samples were collected to characterize the emissions of semivolatile and intermediate volatility organic compounds. The dilute emissions were injected into a smog chamber and then photochemically aged, and the SOA production was quantified. Although BC and POA emissions varied significantly for HDDV, LDGV and LDDV, the amount of SOA per mass of fuel burned was comparable. Since fuel consumption is dominated by gasoline vehicles, the data suggest that gasoline vehicles are the greater on-road source of SOA. When the dramatic reduction in primary PM observed with aftertreatment-equipped HDDV is factored into the analysis of the net (primary + secondary) PM emissions, newer HDDV stand out as remarkably clean vehicles.