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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Characterization of Mixed Diesel and Gasoline Exhaust by High-Resolution Aerosol Mass Spectrometry under Varied Engine Load and Dilution Conditions

COURTNEY L. HERRING, Matthew H. Erickson, Mylene Gueneron, Jacob D. McDonald, B. Thomas Jobson, Timothy M. VanReken, Washington State University

     Abstract Number: 688
     Working Group: Combustion

We present the results of a series of experiments conducted at the Lovelace Respiratory Research Institute (LRRI) to investigate the gas- and particle-phase properties of mixed exhaust from diesel and gasoline engines. Approximately 25 tests were conducted across a range of gas/diesel mixing ratios, engine loads, and particle concentrations to examine how these factors affect chemical composition and phase partitioning of the exhaust. The organic aerosol composition was characterized and measured using an Aerodyne High-Resolution Time-of-Flight Aerosol Mass Spectrometer (HR-ToF-AMS). Gas-phase organics were measured with a Proton Transfer Reaction Mass Spectrometer (PTR-MS) fitted with an IVOC sampler. Supporting measurements include the particle size distribution, black carbon mass, and carbon dioxide mixing ratio.

Analyses of HR-AMS data for the diesel and diesel/gasoline mixtures show several interesting patterns potentially associated with differences in particle mass loadings and engine operating conditions. Strong signals have been identified associated with a wide range of polycyclic-aromatic-hydrocarbons (PAHs), including those that can partition between the gas and particle phases. Additionally, differences in relative abundances at some unit-resolution ion masses suggest significant differences in exhaust chemical processing under varying conditions, some resulting in nitrogen-containing organic species. Further analysis and investigation into the particle phase data along with the gas phase measurements is ongoing with the goal of better understanding the gas/particle partitioning behavior of gas/diesel mixtures and the potential for this partitioning to affect aerosol toxicity.