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| Titel |
New particle formation events in semi-clean South African savannah |
| VerfasserIn |
V. Vakkari, H. Laakso  , M. Kulmala , A. Laaksonen, D. Mabaso, M. Molefe, N. Kgabi, L. Laakso |
| 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 ; 11, no. 7 ; Nr. 11, no. 7 (2011-04-07), S.3333-3346 |
| Datensatznummer |
250009596
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| Publikation (Nr.) |
 copernicus.org/acp-11-3333-2011.pdf |
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| Zusammenfassung |
| This study is based on 18 months (20 July 2006–5 February 2008) of
continuous measurements of aerosol particle size distributions, air ion size
distributions, trace gas concentrations and basic meteorology in a
semi-clean savannah environment in Republic of South Africa. New particle
formation and growth was observed on 69% of the days and bursts of
non-growing ions/sub-10 nm particles on additional 14% of the days. This
new particle formation frequency is the highest reported from boundary layer
so far. Also the new particle formation and growth rates were among the
highest reported in the literature for continental boundary layer locations;
median 10 nm formation rate was 2.2 cm−3 s−1 and median 10–30 nm
growth rate 8.9 nm h−1. The median 2 nm ion formation rate was 0.5 cm−3 s−1 and the median ion growth rates were 6.2, 8.0 and 8.1 nm h−1
for size ranges 1.5–3 nm, 3–7 nm and 7–20 nm, respectively. The
growth rates had a clear seasonal dependency with minimum during winter and
maxima in spring and late summer. The relative contribution of estimated
sulphuric acid to the growth rate was decreasing with increasing particle
size and could explain more than 20% of the observed growth rate only for
the 1.5–3 nm size range. Also the air mass history analysis indicated the
highest formation and growth rates to be associated with the area of highest
VOC (Volatile Organic Compounds) emissions following from biological
activity rather than the highest estimated sulphuric acid concentrations.
The frequency of new particle formation, however, increased nearly
monotonously with the estimated sulphuric acid reaching 100% at
H2SO4 concentration of 6 · 107 cm−3, which
suggests the formation and growth to be independent of each other. |
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