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| Titel |
The fluorescence properties of aerosol larger than 0.8 μm in urban and tropical rainforest locations |
| VerfasserIn |
A. M. Gabey, W. R. Stanley, M. W. Gallagher, 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 ; 11, no. 11 ; Nr. 11, no. 11 (2011-06-15), S.5491-5504 |
| Datensatznummer |
250009815
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| Publikation (Nr.) |
 copernicus.org/acp-11-5491-2011.pdf |
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| Zusammenfassung |
UV-LIF measurements were performed on ambient aerosol in Manchester, UK
(urban city centre, winter) and Borneo, Malaysia (remote, tropical) using a
Wide Issue Bioaerosol Spectrometer, version 3 (WIBS3). These sites are taken
to represent environments with minor and significant primary biological
aerosol (PBA) influences respectively, and the urban dataset describes the
fluorescent background aerosol against which PBA must be identified by
researchers using LIF. The ensemble aerosol at both sites was characterised
over 2–3 weeks by measuring the fluorescence intensity and optical
equivalent diameter (DP) of single particles sized 0.8 ≤ DP ≤ 20 μm. Filter samples were also collected for a subset of the
Manchester campaign and analysed using energy dispersive X-Ray (EDX)
spectroscopy and environmental scanning electron microscopy (ESEM), which
revealed mostly non-PBA at D ≤ 1 μm.
The WIBS3 features three fluorescence channels: the emission following a
280 nm excitation is recorded at 310–400 nm (channel F1) and
400–600 nm (F2), and fluorescence excited at 350 nm is detected at
400–600 nm (F3). In Manchester the primary size mode of fluorescent and
non-fluorescent material was present at 0.8–1.2 μm, with a secondary
fluorescent mode at 2–4 μm. In Borneo non-fluorescent material peaked
at 0.8–1.2 μm and fluorescent at 3–4 μm. Agreement between
fluorescent number concentrations in each channel differed at the two sites,
with F1 and F3 reporting similar concentrations in Borneo but F3
outnumbering F1 by a factor of 2–3 across the size spectrum in Manchester.
The fluorescence intensity in each channel generally rose with DP at
both sites with the exception of F1 intensity in Manchester, which peaked at
DP = 4 μm, causing a divergence between F1 and F3 intensity at
larger DP. This divergence and the differing fluorescent particle
concentrations demonstrate the additional discrimination provided by the F1
channel in Manchester. The relationships between fluorescence intensities in
different pairs of channels were also investigated as a function of DP.
Differences between these metrics were apparent at each site and provide
some distinction between the two datasets. Finally, particle selection
criteria based on the Borneo dataset were applied to identify a median
concentration of 10 "Borneo-like" fluorescent particles per litre in
Manchester. |
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