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| Titel |
Seasonal cycles of fluorescent biological aerosol particles in boreal and semi-arid forests of Finland and Colorado |
| VerfasserIn |
C. J. Schumacher, C. Pöhlker, P. Aalto, V. Hiltunen, T. Petäjä, M. Kulmala  , U. Pöschl, J. A. Huffman |
| 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 ; 13, no. 23 ; Nr. 13, no. 23 (2013-12-11), S.11987-12001 |
| Datensatznummer |
250085870
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| Publikation (Nr.) |
 copernicus.org/acp-13-11987-2013.pdf |
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| Zusammenfassung |
| Biological aerosol particles have become increasingly important for
atmospheric study, but continuous measurements at high time and size
resolution have not been available until recently. Here we report seasonal
cycles of fluorescent biological aerosol particles (FBAP) from the boreal
forest in Hyytiälä, Finland (18 months) and the semi-arid Manitou
Experimental Forest, Colorado (10 months). FBAP at both locations were
observed to be highest in summer and lowest in winter, increasing by factors
of 12 and 5 between these seasons, respectively. In addition to the low
temperatures and reduced sunlight during winter, we suggest that snow cover
inhibited FBAP release from local terrestrial surfaces and that more
extensive snow cover at the Finland site contributed to lower winter FBAP
concentrations. Average size distributions at each site exhibited peaks
between 1.5 and 6 μm in aerodynamic diameter. The Finland site
consistently showed a dominant, narrow FBAP peak at ~ 3 μm in addition to discreet modes at
~ 1.5 and ~ 5 μm, whereas the Colorado site showed broader peaks at 1.5 and 5 μm, suggesting different modes of biological particles at the two sites.
FBAP concentrations in both locations were shown to correlate with daily
patterns of relative humidity (RH) during each season. Also during summer at
each site, average FBAP concentration scaled with RH, but at the Finland
site RH values above ~ 82% led to a significant decrease in
FBAP concentration. We hypothesize that this is due to dew formation that
inhibits bioparticle release. Lastly we show that rain during summer at each
location led to pronounced increases in both fluorescent and total particle
concentrations with FBAP peak particle size at ~ 2 μm and
concentration scaling with rain intensity. We suggest that these particles
are primarily fungal spores and other bioparticles lofted from splashing of
rain droplets hitting soil and leaf surfaces. During the summer at the
Colorado site we consistently observed a mode of ~ 4 μm
particles appearing several hours after rain events that we suggest are
fungal spores actively emitted when ambient conditions are most advantageous
for spread and germination. The pronounced patterns of fluorescent
bioparticles observed here suggest that parameterizations of both daily and
seasonal cycles will be important to accurately reflect bioparticle
emissions in future studies of atmospheric bioaerosols and their potential
effects on clouds and precipitation. |
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