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| Titel |
Properties of atmospheric humic-like substances – water system |
| VerfasserIn |
I. Salma, R. Ocskay, G. G. Láng |
| 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 ; 8, no. 8 ; Nr. 8, no. 8 (2008-04-24), S.2243-2254 |
| Datensatznummer |
250006063
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| Publikation (Nr.) |
 copernicus.org/acp-8-2243-2008.pdf |
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| Zusammenfassung |
| Urban-type PM2.5-fraction aerosol samples were collected and samples of pure
atmospheric humic-like substances (HULIS) were isolated from them.
Atmospheric concentrations of organic carbon (OC), water soluble organic
carbon (WSOC) and HULIS were determined, and UV/Vis spectroscopic
properties, solubility and conductivity of HULIS in aqueous samples were
investigated. Atmospheric concentrations of OC and WSOC were 8.5 and 4.6 μg m−3, respectively. Hydrophilic WSOC accounted for 39% of
WSOC, carbon in HULIS made up 47% of WSOC, and 14% of WSOC was
retained on the separation column by irreversible adsorption. Overall
average molecular mass and aromatic carbon abundance of HULIS were estimated
from molar absorptivity to be 556 Da and 12%, respectively. Both results
are substantially smaller than for standard reference fulvic acids, which
imply different mechanisms for the formation processes of atmospheric HULIS
and aquatic or terrestrial humic matter. HULIS were found to be water
soluble as ionic unimers with a saturation concentration of 2–3 g l−1.
Their solubility increased again with total HULIS concentration being above
approximately 4 g l−1, which was most likely explained by the formation
of HULIS aggregates. Solubility increased linearly from approximately 5 up
to 20 g l−1 of dissolved HULIS concentration. The ionic dissolution was
confirmed by electrochemical conductivity in the investigated concentration
interval. Limiting molar conductivity was extrapolated and this was utilized
to determine the apparent dissociation degree of HULIS for different
concentrations. The dissociation degree was further applied to derive the
concentration dependence of the van't Hoff factor of HULIS. The van't Hoff
factor decreased monotonically with HULIS concentration; the decrease was
substantial for dilute solutions and the relationship became weak for rather
concentrated solutions. |
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