 |
| Titel |
Physical–chemical characterisation of the particulate matter inside two road tunnels in the São Paulo Metropolitan Area |
| VerfasserIn |
J. Brito, L. V. Rizzo, P. Herckes, P. C. Vasconcellos, S. E. S. Caumo, A. Fornaro, R. Y. Ynoue, P. Artaxo, M. F. Andrade |
| Medientyp |
Artikel
|
| Sprache |
Englisch
|
| ISSN |
1680-7316
|
| Digitales Dokument |
URL |
| Erschienen |
In: Atmospheric Chemistry and Physics ; 13, no. 24 ; Nr. 13, no. 24 (2013-12-17), S.12199-12213 |
| Datensatznummer |
250085884
|
| Publikation (Nr.) |
 copernicus.org/acp-13-12199-2013.pdf |
|
|
|
|
|
| Zusammenfassung |
The notable increase in biofuel usage by the road transportation sector in
Brazil during recent years has significantly altered the vehicular fuel
composition. Consequently, many uncertainties are currently found in
particulate matter vehicular emission profiles. In an effort to better
characterise the emitted particulate matter, measurements of aerosol physical
and chemical properties were undertaken inside two tunnels located in the
São Paulo Metropolitan Area (SPMA). The tunnels show very distinct fleet
profiles: in the J-nio Quadros (JQ) tunnel, the vast majority of the
circulating fleet are light duty vehicles (LDVs), fuelled on average with the
same amount of ethanol as gasoline. In the Rodoanel (RA) tunnel, the
particulate emission is dominated by heavy duty vehicles (HDVs) fuelled with
diesel (5% biodiesel). In the JQ tunnel, PM2.5 concentration was on
average 52 μg m−3, with the largest contribution of organic
mass (OM, 42%), followed by elemental carbon (EC, 17%) and crustal
elements (13%). Sulphate accounted for 7% of PM2.5 and the sum of
other trace elements was 10%. In the RA tunnel, PM2.5 was on average
233 μg m−3, mostly composed of EC (52%) and OM (39%).
Sulphate, crustal and the trace elements showed a minor contribution with
5%, 1%, and 1%, respectively. The average OC : EC ratio in the JQ
tunnel was 1.59 ± 0.09, indicating an important contribution of EC despite
the high ethanol fraction in the fuel composition. In the RA tunnel, the
OC : EC ratio was 0.49 ± 0.12, consistent with previous measurements of
diesel-fuelled HDVs. Besides bulk carbonaceous aerosol measurement,
polycyclic aromatic hydrocarbons (PAHs) were quantified. The sum of the PAHs
concentration was 56 ± 5 ng m−3 and 45 ± 9 ng m−3
in the RA and JQ tunnel, respectively. In the JQ tunnel, benzo(a)pyrene (BaP)
ranged from 0.9 to 6.7 ng m−3 (0.02–0.1‰ of
PM2.5) whereas in the RA tunnel BaP ranged from 0.9 to
4.9 ng m−3 (0.004–0. 02‰ of PM2.5),
indicating an important relative contribution of LDVs emission to atmospheric
BaP.
Real-time measurements performed in both tunnels provided aerosol size
distributions and optical properties. The average particle count yielded
73 000 cm−3 in the JQ tunnel and 366 000 cm−3 in the
RA tunnel, with an average diameter of 48 nm in the former and
39 nm in the latter. Aerosol single scattering albedo, calculated
from scattering and absorption observations in the JQ tunnel, indicates a
value of 0.5 associated with LDVs. Such single scattering albedo is 20–50%
higher than observed in previous tunnel studies, possibly as a result of the
large biofuel usage. Given the exceedingly high equivalent black carbon
loadings in the RA tunnel, real time light absorption measurements were
possible only in the JQ tunnel. Nevertheless, using EC measured from the
filters, a single scattering albedo of 0.31 for the RA tunnel has been
estimated. The results presented here characterise particulate matter emitted
from nearly 1 million vehicles fuelled with a considerable amount of
biofuel, providing a unique experimental site worldwide. |
| |
|
| Teil von |
|
|
|
|
|
|
|
|