Gas phase composition and secondary organic aerosol formation from gasoline direct injection vehicles investigated in batch and flow reactors: effects of prototype gasoline particle filters

Abstract

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) formation from GDI vehicle exhaust for multiple vehicles and driving test cycles, and novel GDI after-treatment systems.Emissions were characterized by proton transfer reaction time-of-flight mass spectrometry (gaseous non-methane organic 15 compounds, NMOCs), aerosol mass spectrometry (sub-micron non-refractory particles), and light attenuation measurements (equivalent black carbon (eBC) determination using Aethalometer measurements) together with supporting instrumentation.We evaluated the effect of retrofitted prototype gasoline particle filters (GPFs) on primary eBC, organic aerosol (OA), NMOCs, as well as SOA formation. Two regulatory driving test cycles were investigated, and the importance of distinct phases within these cycles (e.g. cold engine start, hot engine start, high speed driving) to primary emissions and secondary 20 products was evaluated. Atmospheric processing was simulated using both the PSI mobile smog chamber (SC) and the potential aerosol mass oxidation flow reactor (OFR). GPF retrofitting was found to greatly decrease primary particulate matter (PM) through removal of eBC, but showed limited partial removal of the minor POA fraction, and had no detectable effect on either NMOC emissions (absolute emission factors or relative composition) or SOA production. In all tests, overall primary and secondary PM and NMOC emissions were dominated by the engine cold start, i.e. before thermal activation of 25 the catalytic after-treatment system. Differences were found in the bulk compositional properties of SOA produced by the OFR and the SC (O:C and H:C ratios), while the SOA yields agree within our uncertainties, with a tendency for lower SOA yields in SC experiments. A few aromatic compounds are found to dominate the NMOC emissions (primarily benzene, toluene, xylene isomers and C3-benzenes). A large fraction (> 0.5) of the SOA production was explained by those compounds, based on investigation of reacted NMOC mass and comparison with SOA yield curves of toluene, o-xylene and 30 1,2,4-trimethylbenzene determined in our OFR within this study. Remaining differences in the obtained SOA yields may Atmos. Chem. Phys. Discuss., https://doi.org/10.5194/acp-2017-942 Manuscript under review for journal Atmos. Chem. Phys. Atmos. Chem. Phys. Discuss., https://doi

Catalyzed Gasoline Particulate Filters Reduce Secondary Organic Aerosol Production from Gasoline Direct Injection Vehicles

“…In this study, we investigated the SOA production from two current GDI vehicles with and without a catalyzed GPF. To the best of our knowledge, only Pieber et al 36 evaluated SOA production from GDI vehicles equipped with prototype GPFs using a batch and a flow reactor. While the authors did not find differences in SOA formation with the tested noncatalyzed and catalytically coated GPFs, they suggested that the catalyzed GPFs could be installed at the same position as the underfloor TWC, and that this should be investigated in future work.…”

Identification of secondary aerosol precursors emitted by an aircraft turbofan

“…Single-ring aromatics are traditionally thought to be the most important secondary organic aerosol (SOA) precursors from combustion emissions. While this has been shown to be the case for some emissions, e.g., from twostroke engines (Platt et al, 2014), in other cases nontraditional precursors were assessed to be responsible for the bulk of the SOA mass formed, e.g., for biomass smoke (Bruns et al, 2016) or on-road vehicles (Platt et al, 2013(Platt et al, , 2017Pieber et al, 2017). Similar to these emissions, aging of aircraft emissions studied by Miracolo et al (2011Miracolo et al ( , 2012 in a smog chamber produced substantial amounts of secondary PM exceeding primary PM emissions severalfold.…”

“…Single-ring aromatics, such as xylenes, methylbenzenes, toluene, and benzene, were previously linked with SOA formation (e.g., Odum et al, 1997;Ng et al, 2007). These aromatic gases are important contributors in the emissions from combustion sources such as two-stroke scooters (Platt et al, 2013) or wood burning (Bruns et al, 2016). Idling exhaust contained 20 % (mass weighted) of aromatic HCs.…”

Response to Reviews

“…Single-ring aromatics, such as xylenes, methylbenzenes, toluene, and benzene, were previously linked with SOA formation (e.g., Odum et al, 1997;Ng et al, 2007). These aromatic gases are important contributors in the emissions from combustion sources such as two-stroke scooters (Platt et al, 2013) or wood burning . Idling exhaust contained 20 % (mass weighted) of aromatic HCs.…”

“…Single-ring aromatics are traditionally thought to be the most important secondary organic aerosol (SOA) precursors from combustion emissions. While this has been shown to be the case for some emissions, e.g., from twostroke engines (Platt et al, 2014), in other cases nontraditional precursors were assessed to be responsible for the bulk of the SOA mass formed, e.g., for biomass smoke or on-road vehicles (Platt et al, 2013Pieber et al, 2017). Similar to these emissions, aging of aircraft emissions studied by Miracolo et al (2011Miracolo et al ( , 2012 in a smog chamber produced substantial amounts of secondary PM exceeding primary PM emissions severalfold.…”