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| Titel |
Observations of fluorescent and biological aerosol at a high-altitude site in central France |
| VerfasserIn |
A. M. Gabey, M. Vaïtilingom, E. Freney, J. Boulon, K. Sellegri, M. W. Gallagher, I. P. Crawford, N. H. Robinson, W. R. Stanley, P. H. Kaye |
| 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. 15 ; Nr. 13, no. 15 (2013-08-02), S.7415-7428 |
| Datensatznummer |
250018801
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| Publikation (Nr.) |
 copernicus.org/acp-13-7415-2013.pdf |
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| Zusammenfassung |
Total bacteria, fungal spore and yeast counts were compared with
ultraviolet-light-induced fluorescence (UV-LIF) measurements of ambient
aerosol at the summit of the Puy de Dôme (PdD) mountain in central France
(1465 m a.s.l), which represents a background elevated site. Bacteria,
fungal spores and yeast were enumerated by epifluorescence microscopy (EFM)
and found to number 2.2 to 23 L−1 and 0.8 to 2 L−1, respectively.
Bacteria counts on two successive nights were an order of magnitude larger
than in the intervening day.
A wide issue bioaerosol spectrometer, version 3 (WIBS-3) was used to perform
UV-LIF measurements on ambient aerosol sized 0.8 to 20 μm. Mean
total number concentration was 270 L−1 (σ = 66 L−1), found
predominantly in a size mode at 2 μm for most of the campaign.
Total concentration (fluorescent + non-fluorescent aerosol) peaked at
500 L−1 with a size mode at 1 μm because of a change in air
mass origin lasting around 48 h. The WIBS-3 features two excitation and
fluorescence detection wavelengths corresponding to different biological
molecules, although non-biological interferents also contribute. The mean
fluorescent particle concentration after short-wave (280 nm; associated with
tryptophan) excitation was 12 L−1 (σ = 6 L−1), and did not
vary much throughout the campaign. In contrast, the mean concentration of
particles fluorescent after long-wave (370 nm; associated with NADH)
excitation was 95 L−1 (σ = 25 L−1), and a nightly rise and
subsequent fall of up to 100 L−1 formed a strong diurnal cycle in the
latter. The two fluorescent populations exhibited size
modes at 3 μm and 2 to 3 μm, respectively. A hierarchical
agglomerative cluster analysis algorithm was applied to the data and used to
extract different particle factors. A cluster concentration time series
representative of bacteria was identified. This was found to exhibit a
diurnal cycle with a maximum peak appearing during the day.
Analysis of organic mass spectra recorded using an aerosol mass spectrometer
(AMS; Aerodyne Inc.) suggests that aerosol reaching the site at night was
more aged than that during the day, indicative of sampling the residual layer
at night. Supplementary meteorological data and previous work also show that
PdD lies in the residual layer/free troposphere at night, and this is thought
to cause the observed diurnal cycles in organic-type and fluorescent aerosol
particles.
Based on the observed disparity between bacteria and fluorescent particle
concentrations, fluorescent non-PBA is likely to be important in the WIBS-3
data and the surprisingly high fluorescent concentration in the residual
layer/free troposphere raises questions about a ubiquitous background in
continental air during the summer. |
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