 |
| Titel |
Relative humidity-dependent viscosities of isoprene-derived secondary organic material and atmospheric implications for isoprene-dominant forests |
| VerfasserIn |
M. Song, P. F. Liu, S. J. Hanna, Y. J. Li, S. T. Martin, A. K. Bertram |
| Medientyp |
Artikel
|
| Sprache |
Englisch
|
| ISSN |
1680-7316
|
| Digitales Dokument |
URL |
| Erschienen |
In: Atmospheric Chemistry and Physics ; 15, no. 9 ; Nr. 15, no. 9 (2015-05-08), S.5145-5159 |
| Datensatznummer |
250119700
|
| Publikation (Nr.) |
 copernicus.org/acp-15-5145-2015.pdf |
|
|
|
|
|
| Zusammenfassung |
| Oxidation of isoprene is an important source of secondary organic material
(SOM) in atmospheric particles, especially in areas such as the Amazon Basin.
Information on the viscosities, diffusion rates, and mixing times within
isoprene-derived SOM is needed for accurate predictions of air quality,
visibility, and climate. Currently, however, this information is not
available. Using a bead-mobility technique and a poke-flow technique combined
with fluid simulations, the relative humidity (RH)-dependent viscosities of
SOM produced from isoprene photo-oxidation were quantified for
20–60 μm particles at 295 ± 1 K. From 84.5 to 0% RH,
the viscosities for isoprene-derived SOM varied from
~ 2 × 10−1 to ~ 3 × 105 Pa s,
implying that isoprene-derived SOM ranges from a liquid to a semisolid over
this RH range. These viscosities correspond to diffusion coefficients of
~ 2 × 10−8 to
~ 2 × 10−14 cm2 s−1 for large organic
molecules that follow the Stokes–Einstein relation. Based on the diffusion
coefficients, the mixing time of large organic molecules within 200 nm
isoprene-derived SOM particles ranges from approximately 0.1 h to less than
1 s. To illustrate the atmospheric implications of this study's results, the
Amazon Basin is used as a case study for an isoprene-dominant forest.
Considering the RH and temperature range observed in the Amazon Basin and
with some assumptions about the dominant chemical compositions of SOM
particles in the region, it is likely that SOM particles in this area are
liquid and reach equilibrium with large gas-phase organic molecules on short
time scales, less than or equal to approximately 0.1 h. |
| |
|
| Teil von |
|
|
|
|
|
|
|
|