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| Titel |
Functional characterization of the water-soluble organic carbon of size-fractionated aerosol in the southern Mississippi Valley |
| VerfasserIn |
M.-C. G. Chalbot, J. Brown, P. Chitranshi, G. Gamboa da Costa, E. D. Pollock, I. G. Kavouras |
| 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 ; 14, no. 12 ; Nr. 14, no. 12 (2014-06-20), S.6075-6088 |
| Datensatznummer |
250118821
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| Publikation (Nr.) |
 copernicus.org/acp-14-6075-2014.pdf |
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| Zusammenfassung |
| The chemical content of water-soluble organic carbon (WSOC) as a function of
particle size was characterized in Little Rock, Arkansas in winter and spring
2013. The objectives of this study were to (i) compare the functional
characteristics of coarse, fine and ultrafine WSOC and (ii) reconcile the
sources of WSOC for periods when carbonaceous aerosol was the most abundant
particulate component. The WSOC accounted for 5% of particle mass for
particles with dp > 0.96 μm and 10%
of particle mass for particles with
dp < 0.96 μm. Non-exchangeable aliphatic
(H–C), unsaturated aliphatic (H–C–C=), oxygenated saturated aliphatic
(H–C–O), acetalic (O–CH–O) and aromatic (Ar–H) protons were determined
by proton nuclear magnetic resonance (1H-NMR). The total
non-exchangeable organic hydrogen concentrations varied from
4.1 ± 0.1 nmol m−3 for particles with
1.5 < dp < 3.0 μm to
73.9 ± 12.3 nmol m−3 for particles with
dp < 0.49 μm. The molar H / C ratios varied
from 0.48 ± 0.05 to 0.92 ± 0.09, which were comparable to those
observed for combustion-related organic aerosol. The R–H was the most
abundant group, representing about 45% of measured total
non-exchangeable organic hydrogen concentrations, followed by H–C–O
(27%) and H–C–C= (26%). Levoglucosan, amines, ammonium and
methanesulfonate were identified in NMR fingerprints of fine particles.
Sucrose, fructose, glucose, formate and acetate were associated with coarse
particles. These qualitative differences of 1H-NMR profiles for
different particle sizes indicated the possible contribution of biological
aerosols and a mixture of aliphatic and oxygenated compounds from biomass
burning and traffic exhausts. The concurrent presence of ammonium and amines
also suggested the presence of ammonium/aminium nitrate and sulfate secondary
aerosol. The size-dependent origin of WSOC was further corroborated by the
increasing δ13C abundance from −26.81 ± 0.18‰ for
the smallest particles to −25.93 ± 0.31‰ for the largest
particles and the relative distribution of the functional groups as compared
to those previously observed for marine, biomass burning and secondary
organic aerosol. The latter also allowed for the differentiation of urban
combustion-related aerosol and biological particles. The five types of
organic hydrogen accounted for the majority of WSOC for particles with
dp > 3.0 μm and
dp < 0.96 μm. |
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