Fluorescent biological aerosol particle concentrations and size distributions measured with an Ultraviolet Aerodynamic Particle Sizer (UV-APS) in Central Europe 1Max Planck Institute for Chemistry, Biogeochemistry Department, Becherweg 27, Mainz, 55128, Germany
2now at: Ludwig Maximilians University, Institute for Physical Chemistry, Munich, Germany
Received: 24 Jul 2009 – Published in Atmos. Chem. Phys. Discuss.: 28 Aug 2009 Abstract. 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 provide an estimate of viable
bioaerosol particles and can be regarded as an approximate 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).
Revised: 05 Mar 2010 – Accepted: 16 Mar 2010 – Published: 06 Apr 2010
Averaged over the four-month measurement period (August–December 2006),
the mean number concentration of coarse FBAPs was ~3×10−2 cm−3,
corresponding to ~4% of total coarse particle number.
The mean mass concentration of FBAPs was ~1μg m−3,
corresponding to ~20% of total coarse particle mass. The FBAP
number size distributions exhibited alternating patterns with peaks at
various diameters. A pronounced peak at ~3 μm was essentially
always observed and can be described by the following campaign-average lognormal fit
parameters: geometric mean diameter 3.2 μm, geometric standard
deviation 1.3, number concentration 1.6×10−2 cm−3. This peak is
likely due to fungal spores or agglomerated bacteria, and it exhibited a
pronounced diel cycle (24-h) 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 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
exploratory study reporting continuous online measurements of bioaerosol
particles over several months and a range of characteristic size
distribution patterns with 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.
Citation: Huffman, J. A., Treutlein, B., and Pöschl, U.: Fluorescent biological aerosol particle concentrations and size distributions measured with an Ultraviolet Aerodynamic Particle Sizer (UV-APS) in Central Europe, Atmos. Chem. Phys., 10, 3215-3233, doi:10.5194/acp-10-3215-2010, 2010.