AAAR 35th Annual Conference October 17 - October 21, 2016 Oregon Convention Center Portland, Oregon, USA
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Primary and Secondary Organic Functional Groups in Vehicle Emissions by Mobile Sources Testing
LYNN RUSSELL, Fabian Hagen, Elizabeth Singh, Jun Liu, Yunliang Zhao, Rawad Saleh, Greg Drozd, Allen H. Goldstein, Allen Robinson, Scripps Institution of Oceanography
Abstract Number: 150 Working Group: Carbonaceous Aerosols in the Atmosphere
Abstract Fourier Transform Infrared (FTIR) spectroscopy of organic mass collected on Teflon filters sampled from primary and photochemically-aged vehicle emissions was used to characterize the amount and organic functional group (OFG) composition of particle organic mass (OM). The vehicle emission types tested met the following emission standards: Partial Zero Emissions Vehicle (PZEV), Super-Ultra-Low-Emission Vehicle (SULEV), Ultra-Low-Emission Vehicle (ULEV), Pre-Low Emission Vehicles (LEV) (prior to 1994), LEV1 (1994-2003), and LEV2 (2004-2012). Vehicle emission categories showed differences in amount and composition of emissions, with low primary OM concentrations and emission factors characterizing the newer vehicle categories (PZEV, ULEV, SULEV). For all vehicle emission categories, we found the OFG composition was clearly distinguished for primary and secondary samples: primary emissions (sampled directly from a Constant Volume Sampler, CVS) had alkane and amine groups but no oxidized groups; secondary OM was approximately half oxidized groups with one-third alcohol and two-thirds acid groups in the Potential Aerosol Mass (PAM) chamber and more than two-thirds oxidized groups (mostly acid) in the mobile photochemical (SMOG) chamber. Comparing the compositions measured during this vehicle testing with atmospheric measurements reveals that PAM and SMOG chamber samples are very similar to vehicle-related emission factors identified in Bakersfield and elsewhere. The low OM in the CVS samples is consistent with a small primary contribution, and their amine group fraction indicates that vehicle emissions provide primary amine groups in the non-volatile fraction of primary emissions. Comparisons to FTIR OFG composition from laboratory smog experiments with individual hydrocarbon precursors indicate that the PAM and SMOG chamber samples collected here are similar to the secondary OM composition produced by very high oxidant exposures of both aromatic and alkane precursors.