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| Titel |
Black carbon concentrations and mixing state in the Finnish Arctic |
| VerfasserIn |
T. Raatikainen, D. Brus, A.-P. Hyvärinen, J. Svensson, E. Asmi, H. Lihavainen |
| 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 ; 15, no. 17 ; Nr. 15, no. 17 (2015-09-09), S.10057-10070 |
| Datensatznummer |
250120022
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| Publikation (Nr.) |
 copernicus.org/acp-15-10057-2015.pdf |
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| Zusammenfassung |
| Atmospheric aerosol composition was measured using a Single Particle Soot
Photometer (SP2) in the Finnish Arctic during winter 2011–2012. The
Sammaltunturi measurement site at the Pallas GAW (Global Atmosphere Watch)
station receives air masses from different source regions including the
Arctic Ocean and continental Europe. The SP2 provides detailed information
about mass distributions and mixing state of refractory black carbon (rBC).
The measurements showed widely varying rBC mass concentrations
(0–120 ng m−3), which were related to varying contributions of
different source regions and aerosol removal processes. The rBC mass was
log-normally distributed showing a relatively constant rBC core mass mean
diameter with an average of 194 nm (75–655 nm sizing range).
On average, the number fraction of particles containing rBC was 0.24 (integrated
over 350–450 nm particle diameter range) and the average particle diameter
to rBC core volume equivalent diameter ratio was 2.0 (averaged over particles
with 150–200 nm rBC core volume equivalent diameters). These average
numbers mean that the observed rBC core mass mean diameter is similar to
those of aged particles, but the observed particles seem to have unusually
high particle to rBC core diameter ratios. Comparison of the measured rBC
mass concentration with that of the optically detected equivalent black
carbon (eBC) using an Aethalometer and a MAAP showed that eBC was larger by a
factor of five. The difference could not be fully explained without assuming
that only a part of the optically detected light absorbing material is
refractory and absorbs light at the wavelength used by the SP2. Finally,
climate implications of five different black carbon mixing state
representations were compared using the Mie approximation and simple direct
radiative forcing efficiency calculations. These calculations showed that the
observed mixing state means significantly lower warming effect or even a net
cooling effect when compared with that of a homogenous aerosol containing
the same amounts of black carbon and non-absorbing material. |
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