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| Titel |
Optical properties of humic-like substances (HULIS) in biomass-burning aerosols |
| VerfasserIn |
A. Hoffer, A. Gelencsér, P. Guyon, G. Kiss, O. Schmid, G. P. Frank, P. Artaxo, M. O. Andreae |
| 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 ; 6, no. 11 ; Nr. 6, no. 11 (2006-08-30), S.3563-3570 |
| Datensatznummer |
250004072
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| Publikation (Nr.) |
 copernicus.org/acp-6-3563-2006.pdf |
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| Zusammenfassung |
| We present here the optical properties of humic-like substances (HULIS)
isolated from the fine fraction of biomass-burning aerosol collected in the
Amazon basin during the LBA-SMOCC (Large scale Biosphere atmosphere
experiment in Amazonia – SMOke aerosols, Clouds, rainfall and Climate)
experiment in September 2002. From the isolated HULIS, aerosol particles
were generated and their scattering and absorption coefficients measured.
The size distribution and mass of the particles were also recorded. The
value of the index of refraction was derived from "closure" calculations
based on particle size, scattering and absorption measurements. On average,
the complex index of refraction at 532 nm of HULIS collected during day and
nighttime was 1.65–0.0019i and 1.69–0.0016i, respectively. In addition, the
imaginary part of the complex index of refraction was calculated using the
measured absorption coefficient of the bulk HULIS.
The mass absorption coefficient of the HULIS at 532 nm was found to be quite
low (0.031 and 0.029 m2 g−1 for the day and night samples,
respectively). However, due to the high absorption Ångström exponent
(6–7) of HULIS, the specific absorption increases substantially towards
shorter wavelengths (~2–3 m2 g−1 at 300 nm), causing a
relatively high (up to 50%) contribution to the light absorption of our
Amazonian aerosol at 300 nm. For the relative contribution of HULIS to light
absorption in the entire solar spectrum, lower values (6.4–8.6%) are
obtained, but those are still not negligible. |
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