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| Titel |
The effect of metal salts on quantification of elemental and organic carbon in diesel exhaust particles using thermal-optical evolved gas analysis |
| VerfasserIn |
Y. Wang, A. Chung, S. E. Paulson |
| 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 ; 10, no. 23 ; Nr. 10, no. 23 (2010-12-03), S.11447-11457 |
| Datensatznummer |
250008932
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| Publikation (Nr.) |
 copernicus.org/acp-10-11447-2010.pdf |
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| Zusammenfassung |
| Thermal-optical evolved gas analysis (TOEGA) is a conventional method for
classifying carbonaceous aerosols as organic carbon (OC) and elemental
carbon (EC). Its main source of uncertainty arises from accounting for
pyrolized OC (char), which has similar behavior to the EC originally present
on the filter. Sample composition can also cause error, at least partly by
complicating the charred carbon correction. In this study, lab generated
metal salt particles, including alkali (NaCl, KCl, Na2SO4),
alkaline-earth (MgCl2, CaCl2) and transition metal salts
(CuCl2, FeCl2, FeCl3, CuCl, ZnCl2, MnCl2,
CuSO4, Fe2(SO4)3), were deposited on a layer of diesel
particles to investigate their effect on EC and OC quantification with
TOEGA. Measurements show that metals reduce the oxidation temperature of EC
and enhance the charring of OC. The split point used to determine
classification of EC vs. OC is more dependent on changes in EC oxidation
temperature than it is on charring. The resulting EC/OC ratio is reduced by
0–80% in the presence of most of the salts, although some metal salts
increase reported EC/OC at low metal to carbon ratios. The results imply
that EC/OC ratios of ambient aerosols quantified with TOEGA have variable
low biases due to the presence of metals. In general, transition metals are
more active than alkali and alkaline-earth metals; copper is the most
active. Copper and iron chlorides are more active than sulfates. The melting
point of metal salts is strongly correlated with the increase of OC
charring, but not with the reduction of EC oxidation temperature. Other
chemistry, such as redox reactions, may affect the EC oxidation. A brief
discussion of possible catalytic mechanisms for the metals is provided. |
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