Aerosol and trace gas vehicle emission factors measured in a tunnel using an Aerosol Mass Spectrometer and other on-line instrumentation

Roberto Chirico, Andre S.H. Prevot, Peter F. DeCarlo, Maarten F. Heringa, Rene Richter, Ernest Weingartner, Urs Baltensperger

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Abstract

In this study we present measurements of gas and aerosol phase composition for a mixed vehicle fleet in the Gubrist tunnel (Switzerland) in June 2008. PM1composition measurements were made with a High-Resolution Time-of-Flight Aerosol Mass Spectrometer (AMS) and a Multi Angle Absorption Photometer (MAAP). Gas-phase measurements of CO, CO2, NOxand total hydrocarbons (THC) were performed with standard instrumentation. Weekdays had a characteristic diurnal pattern with 2 peaks in concentrations for all traffic related species corresponding to high vehicle density (~300±30 vehicles per 5min) in the morning rush hour between 06:00 and 09:00 and in the afternoon rush hours from approximately 15:30 to 18:30.The emission factors (EF) of OA were heavily influenced by the OA mass loading. To exclude this partitioning effect, only organic aerosol mass concentrations from 60μgm-3to 90μgm-3were considered and for these conditions the EF(OA) value for HDV was 33.7±2.3mgkm-1for a temperature inside the tunnel of 20-25°C. This value is not directly applicable to ambient conditions because it is derived from OA mass concentrations that are roughly a factor of 10 higher than typical ambient concentrations. An even higher EF(OA)HDVvalue of 47.4±1.6mgkm-1was obtained when the linear fit was applied to all data points including OA concentrations up to 120μgm-3.Similar to the increasing EF, the OA/BC ratio in the tunnel was also affected by the organic loading and it increased by a factor of ~3 over the OA range 10-120μgm-3. This means that also the OA emission factors at ambient concentrations of around 5-10μgm-3would be 2-3 times lower than the emission factor given above. For OA concentrations lower than 40μgm-3the OA/BC mass ratio was below 1, while at an OA concentration of 100-120μgm-3the OA/BC ratio was ~1.5. The AMS mass spectra (MS) acquired in the tunnel were highly correlated with the primary organic aerosol (POA) MS from a EURO 3 diesel vehicle with a speed similar to the average tunnel speed. © 2011 Elsevier Ltd.
Original languageEnglish
Pages (from-to)2182 - 2192
Number of pages11
JournalAtmospheric Environment
Volume45
Issue number13
DOIs
Publication statusPublished - Apr 2011
Externally publishedYes

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All Science Journal Classification (ASJC) codes

  • Environmental Science(all)
  • Atmospheric Science

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