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| Titel |
Phase transitions and hygroscopic growth of aerosol particles containing humic acid and mixtures of humic acid and ammonium sulphate |
| VerfasserIn |
C. L. Badger, I. George, P. T. Griffiths, C. F. Braban, R. A. Cox, J. P. D. Abbatt |
| 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. 3 ; Nr. 6, no. 3 (2006-03-06), S.755-768 |
| Datensatznummer |
250003520
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| Publikation (Nr.) |
 copernicus.org/acp-6-755-2006.pdf |
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| Zusammenfassung |
| The phase transitions and hygroscopic growth of two humic acid aerosols
(Aldrich sodium salt and Leonardite Standard (IHSS)) and
their mixtures with ammonium sulphate have been investigated using a
combination of two techniques, Fourier transform infra-red (FTIR) spectroscopy
and tandem differential mobility analysis (TDMA). A growth factor of 1.16 at 85% relative humidity (RH)
was found for the Aldrich humic acid which can be regarded as an upper limit for
growth factors of humic-like substances (HULIS)
found in atmospheric aerosol and is
significantly smaller than that of typical atmospheric
inorganics. We find that the humic acid aerosols exhibit water uptake over
all relative humidities with no apparent phase changes, suggesting that
these aerosols readily form supersaturated droplets. In the mixed
particles, the humic acid component decreases the deliquescence
relative humidity (DRH) and increases the efflorescence relative humidity
(ERH) of the ammonium sulphate component, and there is some degree of
water uptake prior to ammonium sulphate deliquescence. In addition, at low
RH, the FTIR spectra show
that the ammonium is present in a different chemical
environment in the mixed aerosols than in crystalline ammonium sulphate,
perhaps existing as a complex with the humic materials. The growth factors
of the mixed aerosols are intermediate between those of the
single-component aerosols and can be predicted assuming that the inorganic
and organic fractions take up water independently. |
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