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| Titel |
Sensitivity of the Single Particle Soot Photometer to different black carbon types |
| VerfasserIn |
M. Laborde, P. Mertes, P. Zieger, J. Dommen, U. Baltensperger, M. Gysel |
| Medientyp |
Artikel
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| Sprache |
Englisch
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| ISSN |
1867-1381
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| Digitales Dokument |
URL |
| Erschienen |
In: Atmospheric Measurement Techniques ; 5, no. 5 ; Nr. 5, no. 5 (2012-05-11), S.1031-1043 |
| Datensatznummer |
250002863
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| Publikation (Nr.) |
 copernicus.org/amt-5-1031-2012.pdf |
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| Zusammenfassung |
Black carbon (BC) is now mainly of anthropogenic origin. It is the dominant
light absorbing component of atmospheric aerosols, playing an important role
in the earth's radiative balance and therefore relevant to climate change
studies. In addition, BC is known to be harmful to human beings making it
relevant to policy makers. Nevertheless, the measurement of BC remains biased
by the instrument-based definition of BC. The Single Particle Soot Photometer
(SP2), allows the measurement of the refractory BC (rBC) mass of individual
particles using laser-induced incandescence. However, the SP2 needs an
empirical calibration to retrieve the rBC mass from the incandescence signal
and the sensitivity of the SP2 differs between different BC types. Ideally,
for atmospheric studies, the SP2 should be calibrated using ambient particles
containing a known mass of ambient rBC. However, such "ambient BC"
calibration particles cannot easily be obtained and thus commercially
available BC particles are commonly used for SP2 calibration instead. In this
study we tested the sensitivity of the SP2 to different BC types in order to
characterize the potential error introduced by using non-ambient BC for
calibration. The sensitivity of the SP2 was determined, using an aerosol
particle mass analyzer, for rBC from thermodenuded diesel exhaust, wood
burning exhaust and ambient particles as well as for commercially available
products: Aquadag® and fullerene soot.
Thermodenuded, fresh diesel exhaust has been found to be ideal for SP2
calibration for two reasons. First, the small amount of non-BC matter upon
emission reduces the risk of bias due to incomplete removal of non-BC matter
and second, it is considered to represent atmospheric rBC in urban locations
where diesel exhaust is the main source of BC. The SP2 was found to be up to
16% less sensitive to rBC from thermodenuded ambient particles
(≤15 fg) than rBC from diesel exhaust, however, at least part of this
difference can be explained by incomplete removal of non-refractory
components in the thermodenuder. The amount of remaining non-refractory
matter was estimated to be below 30% by mass, according to a comparison of
the scattering cross sections of the whole particles with that of the pure BC
cores. The SP2 sensitivity to rBC from wood burning exhaust agrees with the
SP2 sensitivity to rBC from diesel exhaust within an error of less than
14% (≤40 fg).
If, due to experimental restrictions, diesel exhaust cannot be used,
untreated fullerene soot was found to give an SP2 calibration curve similar to
diesel exhaust and ambient rBC (within ±10% for a rBC mass
≤15 fg) and is therefore recommended although two different batches
differed by ~14% between themselves. In addition, the SP2 was found
to be up to 40% more sensitive to Aquadag® than to
diesel exhaust rBC. Therefore Aquadag® cannot be
recommended for atmospheric application without accounting for the
sensitivity difference. These findings for fullerene soot and
Aquadag® confirm results from previous literature. |
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