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| Titel |
A modeling approach to evaluate the uncertainty in estimating the evaporation behaviour and volatility of organic aerosols |
| VerfasserIn |
E. Fuentes, G. McFiggans |
| 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. 4 ; Nr. 5, no. 4 (2012-04-18), S.735-757 |
| Datensatznummer |
250002776
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| Publikation (Nr.) |
 copernicus.org/amt-5-735-2012.pdf |
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| Zusammenfassung |
The uncertainty in determining the volatility behaviour of organic particles
from thermograms using calibration curves and a kinetic model has been
evaluated. In the analysis, factors such as re-condensation, departure from
equilibrium and analysis methodology were considered as potential sources of
uncertainty in deriving volatility distribution from thermograms obtained
with currently used thermodenuder designs.
The previously found empirical relationship between C* (saturation
concentration) and T50 (temperature at which 50% of aerosol mass
evaporates) was theoretically interpreted and tested to infer volatility
distributions from experimental thermograms. The presented theoretical
analysis shows that this empirical equation is in fact an equilibrium
formulation, whose applicability is lessened as measurements deviate from
equilibrium. While using a calibration curve between C* and
T50 to estimate volatility properties was found to hold at
equilibrium, significant underestimation was obtained under
kinetically-controlled evaporation conditions. Because thermograms obtained
at ambient aerosol loading levels are most likely to show departure from
equilibrium, the application of a kinetic evaporation model is more suitable
for inferring volatility properties of atmospheric samples than the
calibration curve approach; however, the kinetic model analysis implies
significant uncertainty, due to its sensitivity to the assumption of
"effective" net kinetic evaporation and condensation coefficients. The
influence of re-condensation on thermograms from the thermodenuder designs
under study was found to be highly dependent on the particular experimental
condition, with a significant potential to affect volatility estimations for
aerosol mass loadings >50 μg m−3 and with increasing effective
kinetic coefficient for condensation and decreasing particle size. These
results show that the geometry of current thermodenuder systems should be
modified to prevent re-condensation. |
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