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Volume 18, issue 13 | Copyright
Atmos. Chem. Phys., 18, 9929-9954, 2018
© Author(s) 2018. This work is distributed under
the Creative Commons Attribution 4.0 License.

Research article 13 Jul 2018

Research article | 13 Jul 2018

Gas-phase composition and secondary organic aerosol formation from standard and particle filter-retrofitted gasoline direct injection vehicles investigated in a batch and flow reactor

Simone M. Pieber1,4, Nivedita K. Kumar1, Felix Klein1, Pierre Comte2, Deepika Bhattu1, Josef Dommen1, Emily A. Bruns1, Doǧuşhan Kılıç1,a, Imad El Haddad1, Alejandro Keller3, Jan Czerwinski2, Norbert Heeb5, Urs Baltensperger1, Jay G. Slowik1, and André S. H. Prévôt1 Simone M. Pieber et al.
  • 1Paul Scherrer Institute, Laboratory of Atmospheric Chemistry, 5232 Villigen, Switzerland
  • 2Bern University of Applied Sciences, 2560 Nidau, Switzerland
  • 3University of Applied Sciences Northwestern Switzerland, 5210 Windisch, Switzerland
  • 4Empa – Swiss Federal Laboratories for Materials Science and Technology, Laboratory for Air Pollution/Environmental Technology, 8600 Dübendorf, Switzerland
  • 5Empa – Swiss Federal Laboratories for Materials Science and Technology, Laboratory for Advanced Analytical Technologies, 8600 Dübendorf, Switzerland
  • anow at: Istanbul Technical University, Eurasia Institute of Earth Sciences, 34467 Sarıyer, Turkey

Abstract. Gasoline direct injection (GDI) vehicles have recently been identified as a significant source of carbonaceous aerosol, of both primary and secondary origin. Here we investigated primary emissions and secondary organic aerosol (SOA) from four GDI vehicles, two of which were also retrofitted with a prototype gasoline particulate filter (GPF). We studied two driving test cycles under cold- and hot-engine conditions. Emissions were characterized by proton transfer reaction time-of-flight mass spectrometry (gaseous non-methane organic compounds, NMOCs), aerosol mass spectrometry (sub-micron non-refractory particles) and light attenuation measurements (equivalent black carbon (eBC) determination using Aethalometers) together with supporting instrumentation. Atmospheric processing was simulated using the PSI mobile smog chamber (SC) and the potential aerosol mass oxidation flow reactor (OFR). Overall, primary and secondary particulate matter (PM) and NMOC emissions were dominated by the engine cold start, i.e., before thermal activation of the catalytic after-treatment system. Trends in the SOA oxygen to carbon ratio (O:C) for OFR and SC were related to different OH exposures, but divergences in the H:C remained unexplained. SOA yields agreed within experimental variability between the two systems, with a tendency for higher values in the OFR than in the SC (or, vice versa, lower values in the SC). A few aromatic compounds dominated the NMOC emissions, primarily benzene, toluene, xylene isomers/ethylbenzene and C3-benzene. A significant fraction of the SOA was explained by those compounds, based on comparison of effective SOA yield curves with those of toluene, o-xylene and 1,2,4-trimethylbenzene determined in our OFR, as well as others from literature. Remaining discrepancies, which were smaller in the SC and larger in the OFR, were up to a factor of 2 and may have resulted from diverse reasons including unaccounted precursors and matrix effects. GPF retrofitting significantly reduced primary PM through removal of refractory eBC and partially removed the minor POA fraction. At cold-started conditions it did not affect hydrocarbon emission factors, relative chemical composition of NMOCs or SOA formation, and likewise SOA yields and bulk composition remained unaffected. GPF-induced effects at hot-engine conditions deserve attention in further studies.

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Short summary
We studied primary emissions and secondary organic aerosol (SOA) from gasoline direct injection (GDI) vehicles including GDIs retrofitted with gasoline particle filters (GPF). GPF retrofitting significantly decreased the primary particulate matter, particularly through removal of refractory black carbon and, to a lesser extent, of non-refractory organic particulates. SOA experiments were conducted in a batch and flow reactor. GPF retrofitting did not significantly affect precursors or yields.
We studied primary emissions and secondary organic aerosol (SOA) from gasoline direct injection...