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| Titel |
The relationship between 0.25–2.5 μm aerosol and CO2 emissions over a city |
| VerfasserIn |
M. Vogt, E. D. Nilsson, L. Ahlm, E. M. Mårtensson, C. Johansson |
| 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 ; 11, no. 10 ; Nr. 11, no. 10 (2011-05-24), S.4851-4859 |
| Datensatznummer |
250009760
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| Publikation (Nr.) |
 copernicus.org/acp-11-4851-2011.pdf |
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| Zusammenfassung |
| Unlike exhaust emissions, non-exhaust traffic emissions are completely
unregulated and in addition, there are large uncertainties in the non-exhaust
emission factors required to estimate the emissions of these aerosols. This
study provides the first published results of direct measurements of size
resolved emission factors for particles in the size range
0.25–2.5 μm using a new approach to derive aerosol emission
factors based on carbon dioxide (CO2) emission fluxes. Aerosol fluxes
were measured over one year using the eddy covariance method at the top of a
105 m high communication tower in Stockholm, Sweden. Maximum CO2 and
particle fluxes were found when the wind direction coincided with the area of
densest traffic within the footprint area. Negative fluxes (uptake of
CO2 and deposition of particles) coincided with periods of sampling from
an urban forest area. The fluxes of CO2 were used to obtain emission
factors for particles by assuming that the CO2 fluxes could be directly
related to the amount of fuel burnt by vehicles in the footprint area. The
estimated emission factor for the fleet mix in the measurement area was, in
number 1.8 × 1011 particle veh−1 km−1 (for
0.25–2.5 μm size range). Assuming spherical particles of density
1600 kg m−3 this corresponds to 27.5 mg veh−1 km−1. For
particles (0.8–2.5 μm) the emission factors were
5.1 × 109 veh−1 km−1 for number and
11.5 mg veh−1 km−1 for mass. But a wind speed dependence was
noted for high wind speeds. Thus, for wind speeds larger than 9 m s−1,
as measured in the tower at 105 m (U105), the emission factor for
particle number and mass was parameterised as: Ef (Number, 0.8–2.5 μm) = (6.1 ± 1.7)109 U105 −50 ± 188
and Ef (Mass, 0.8–2.5 μm) = (20 ± 12) U105 − 171 ±122. |
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