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| Titel |
Characterization of the size-segregated water-soluble inorganic ions at eight Canadian rural sites |
| VerfasserIn |
L. Zhang, R. Vet, A. Wiebe, C. Mihele, B. Sukloff, E. Chan, M. D. Moran, S. Iqbal |
| 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. 23 ; Nr. 8, no. 23 (2008-12-09), S.7133-7151 |
| Datensatznummer |
250006486
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| Publikation (Nr.) |
 copernicus.org/acp-8-7133-2008.pdf |
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| Zusammenfassung |
Size-segregated water-soluble inorganic ions, including
particulate sulphate (SO42-), nitrate (NO3-), ammonium
(NH4+), chloride (Cl-), and base cations (K+, Na+,
Mg2+, Ca2+), were measured using a Micro-Orifice Uniform Deposit
Impactor (MOUDI) during fourteen short-term field campaigns at eight
locations in both polluted and remote regions of eastern and central Canada.
The size distributions of SO42- and NH4+ were unimodal,
peaking at 0.3–0.6 µm in diameter, during most of the campaigns,
although a bimodal distribution was found during one campaign and a trimodal
distribution was found during another campaign made at a coastal site.
SO42- peaked at slightly larger sizes in the cold seasons (0.5–0.6 µm)
compared to the hot seasons (0.3–0.4 µm) due to the higher
relative humidity in the cold seasons. The size distributions of
NO3- were unimodal, peaking at 4.0–7.0 µm during the
warm-season campaigns, and bimodal, with one peak at 0.3–0.6 µm and
another at 4–7 µm during the cold-season campaigns. A unimodal size
distribution, peaking at 4–6 µm, was found for Cl-, Na+,
Mg2+, and Ca2+ during approximately half of the campaigns and a
bimodal distribution, with one peak at 2 µm and the other at 6 µm,
was found during the rest of the campaigns. For K+, a bimodal
distribution, with one peak at 0.3 µm and the other at 4 µm, was
observed during most of the campaigns. Seasonal contrasts in the
size-distribution profiles suggest that emission sources and air mass
origins were the major factors controlling the size distributions of the
primary aerosols while meteorological conditions were more important for the
secondary aerosols.
The dependence of the particle acidity on the particle size from the
nucleation mode to the accumulation mode was not consistent from site to
site or from season to season. Particles in the accumulation mode were more
acidic than those in the nucleation mode when submicron particles were in
the state of strong acidity; however, when submicron particles were neutral
or weakly acidic, particles in the nucleation mode could sometimes be more
acidic. The inconsistency of the dependence of the particle acidity on the
particle size should have been caused by the different emission sources of
all the related species and the different meteorological conditions during
the different campaigns. The results presented here at least partially
explain the controversial phenomenon found in previous studies on this
topic. |
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