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| Titel |
Bioaerosol Analysis by Online Fluorescence Detection and Fluorescence Microscopy |
| VerfasserIn |
Alex Huffman, Christopher Pöhlker, Bärbel Treutlein, Ulrich Pöschl |
| Konferenz |
EGU General Assembly 2010
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| Medientyp |
Artikel
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| Sprache |
Englisch
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 12 (2010) |
| Datensatznummer |
250042839
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| Zusammenfassung |
| Primary biological aerosol particles (PBAPs), including bacteria, spores and pollen, are
essential for the spread of organisms and disease in the biosphere, and numerous studies have
suggested that they may be important for atmospheric processes, including the formation of
clouds and precipitation. The atmospheric abundance and size distribution of PBAPs,
however, are largely unknown. At a semi-urban site in Mainz, Germany, we used an
ultraviolet aerodynamic particle sizer (UV-APS) to measure fluorescent biological aerosol
particles (FBAPs), which can be regarded as viable bioaerosol particles representing a lower
limit for the actual abundance of PBAPs. Fluorescence of non-biological aerosol
components are likely to influence the measurement results obtained for fine particles
(< 1 μm), but not for coarse particles (1 – 20 μm). Microscopy studies were later
performed at the same location to more directly investigate and identify biological
particles.
Averaged over the four-month measurement period (August – December 2006), the mean
number concentration of coarse FBAPs was  3x10-2 cm-3, corresponding to  4% of total
coarse particle number [1]. The mean mass concentration of FBAPs was  1 μg
m-3, corresponding to  20% of total coarse particle mass. The FBAP number size
distributions exhibited alternating patterns with peaks at various diameters, though a
pronounced peak at  3 μm was essentially always observed. This peak is likely due to
fungal spores or agglomerated bacteria, and it exhibited a pronounced diel cycle with
maximum intensity during early/mid-morning. FBAP peaks around  1.5 μm,  5
μm, and  13 μm were also observed, but less pronounced and less frequent. These
may be explained by single bacterial cells, larger fungal spores, and pollen grains,
respectively.
The observed number concentrations and characteristic sizes of FBAPs are consistent
with microscopic, biological and chemical analyses of PBAPs in aerosol filter samples. To
our knowledge, however, this is the first study reporting continuous online measurements of
bioaerosol particles over several months, a range of characteristic size distribution patterns,
and a persistent bioaerosol peak at  3 μm. The measurement results confirm that PBAPs
account for a substantial proportion of coarse aerosol particle number and mass in continental
boundary layer air. Moreover, they suggest that the number concentration of viable
bioparticles is dominated by fungal spores or agglomerated bacteria with aerodynamic
diameters around 3 μm rather than single bacterial cells with diameters around 1
μm.
Filter samples were later collected at the same sampling location and analyzed with a
fluorescence microscope. By observing collected particles both with transmitted white light
and with fluorescent emission from near-UV excitation, the technique provides
information about whether individual particles are biological and regarding their
viability. Characteristic images of FBAPs are shown. Further goals are to correlate size
distributions from the UV-APS with size information gained from microscopy, and also to
constrain uncertainties that arise from non-biological particles that also exhibit
fluorescence.
[1] Huffman et al. (2009) Atmos. Chem. Phys. Discuss., 9, 17705 – 17751. |
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