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| Titel |
Secondary organic aerosol production from diesel vehicle exhaust: impact of aftertreatment, fuel chemistry and driving cycle |
| VerfasserIn |
T. D. Gordon, A. A. Presto, N. T. Nguyen, W. H. Robertson, K. Na, K. N. Sahay, M. Zhang, C. Maddox, P. Rieger, S. Chattopadhyay, H. Maldonado, M. M. Maricq, A. L. Robinson |
| Medientyp |
Artikel
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| Sprache |
Englisch
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| ISSN |
1680-7316
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| Digitales Dokument |
URL |
| Erschienen |
In: Atmospheric Chemistry and Physics ; 14, no. 9 ; Nr. 14, no. 9 (2014-05-13), S.4643-4659 |
| Datensatznummer |
250118694
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| Publikation (Nr.) |
 copernicus.org/acp-14-4643-2014.pdf |
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| Zusammenfassung |
| Environmental chamber ("smog chamber") experiments were conducted to
investigate secondary organic aerosol (SOA) production from dilute emissions
from two medium-duty diesel vehicles (MDDVs) and three heavy-duty diesel
vehicles (HDDVs) under urban-like conditions. Some of the vehicles were
equipped with emission control aftertreatment devices, including diesel
particulate filters (DPFs), selective catalytic reduction (SCR) and diesel
oxidation catalysts (DOCs). Experiments were also performed with different
fuels (100% biodiesel and low-, medium- or high-aromatic ultralow sulfur
diesel) and driving cycles (Unified Cycle,~Urban Dynamometer Driving
Schedule, and creep + idle). During normal operation, vehicles with a
catalyzed DPF emitted very little primary particulate matter (PM).
Furthermore, photooxidation of dilute emissions from these vehicles produced
essentially no SOA (below detection limit). However, significant primary PM
emissions and SOA production were measured during active DPF regeneration
experiments. Nevertheless, under reasonable assumptions about DPF
regeneration frequency, the contribution of regeneration emissions to the
total vehicle emissions is negligible, reducing PM trapping efficiency by
less than 2%. Therefore, catalyzed DPFs appear to be very effective in
reducing both primary PM emissions and SOA production from diesel vehicles.
For both MDDVs and HDDVs without aftertreatment substantial SOA formed in the
smog chamber – with the emissions from some vehicles generating twice as
much SOA as primary organic aerosol after 3 h of oxidation at typical
urban VOC / NOx ratios (3 : 1). Comprehensive organic gas
speciation was performed on these emissions, but less than half of the
measured SOA could be explained by traditional (speciated) SOA precursors.
The remainder presumably originates from the large fraction (~30%) of
the nonmethane organic gas emissions that could not be speciated using
traditional one-dimensional gas chromatography. The unspeciated organics –
likely comprising less volatile species such as intermediate volatility
organic compounds – appear to be important SOA precursors; we estimate that
the effective SOA yield (defined as the ratio of SOA mass to reacted
precursor mass) was 9 ± 6% if both speciated SOA precursors and
unspeciated organics are included in the analysis. SOA production from creep
+ idle operation was 3–4 times larger than SOA production from the same
vehicle operated over the Urban Dynamometer Driving Schedule (UDDS). Fuel
properties had little or no effect on primary PM emissions or SOA formation. |
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