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| Titel |
Black carbon surface oxidation and organic composition of beech-wood soot aerosols |
| VerfasserIn |
J. C. Corbin, U. Lohmann, B. Sierau, A. Keller, H. Burtscher, A. A. Mensah |
| 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. 20 ; Nr. 15, no. 20 (2015-10-26), S.11885-11907 |
| Datensatznummer |
250120121
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| Publikation (Nr.) |
 copernicus.org/acp-15-11885-2015.pdf |
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| Zusammenfassung |
Soot particles are the most strongly light-absorbing particles
commonly found in the atmosphere. They are major contributors
to the radiative budget of the Earth and to the toxicity of
atmospheric pollution. Atmospheric aging of soot may change
its health- and climate-relevant properties by oxidizing the
primary black carbon (BC) or organic particulate matter (OM)
which, together with ash, comprise soot. This atmospheric
aging, which entails the condensation of secondary particulate
matter as well as the oxidation of the primary OM and BC
emissions, is currently poorly understood.
In this study, atmospheric aging of wood-stove soot aerosols
was simulated in a continuous-flow reactor. The composition of
fresh and aged soot particles was measured in real time by a
dual-vaporizer aerosol-particle mass spectrometer (SP-AMS).
The dual-vaporizer SP-AMS provided information on the OM and BC components
of the soot as well as on refractory components internally mixed with BC.
By switching the
SP-AMS laser vaporizer off and using only the AMS thermal vaporizer (at
600 °C), information on the OM component only was obtained.
In both modes, OM appeared to be generated
largely by cellulose and/or hemicellulose pyrolysis and was
only present in large amounts when new wood was added to the
stove.
In SP-AMS mode, BC signals otherwise dominated the mass spectrum. These
signals consisted of ions related to refractory BC (rBC, C1-5+),
oxygenated carbonaceous ions
(CO1-2+), potassium (K+), and water
(H2O+ and related fragments). The
C4+ : C3+ ratio, but not the
C1+ : C3+ ratio, was consistent with the
BC-structure trends of Corbin et al. (2015c). The
CO1-2+ signals likely originated from BC surface
groups: upon aging, both CO+ and CO2+
increased relative to C1-3+ while
CO2+ simultaneously increased relative to
CO+. Factor analysis (positive matrix factorization) of SP-AMS and AMS data,
using a modified error model to address peak-integration
uncertainties, indicated that the surface composition of the BC
was approximately constant across all stages of combustion for
both fresh and aged samples. These results represent the first
time-resolved measurements of in situ BC surface aging and
suggest that the surface of beech-wood BC may be modelled as a
single chemical species. |
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