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キーワード:
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要旨:
Atmospheric particles of biological origin, also re-
ferred to as bioaerosols or primary biological aerosol parti-
cles (PBAP), are important to various human health and en-
vironmental systems. There has been a recent steep increase
in the frequency of published studies utilizing commercial
instrumentation based on ultraviolet laser/light-induced flu-
orescence (UV-LIF), such as the WIBS (wideband inte-
grated bioaerosol sensor) or UV-APS (ultraviolet aerody-
namic particle sizer), for bioaerosol detection both outdoors
and in the built environment. Significant work over several
decades supported the development of the general technolo-
gies, but efforts to systematically characterize the operation
of new commercial sensors have remained lacking. Specif-
ically, there have been gaps in the understanding of how
different classes of biological and non-biological particles
can influence the detection ability of LIF instrumentation.
Here we present a systematic characterization of the WIBS-
4A instrument using 69 types of aerosol materials, includ-
ing a representative list of pollen, fungal spores, and bacte-
ria as well as the most important groups of non-biological
materials reported to exhibit interfering fluorescent proper-
ties. Broad separation can be seen between the biological and
non-biological particles directly using the five WIBS output
parameters and by taking advantage of the particle classifi-
cation analysis introduced by Perring et al. (2015). We high-
light the importance that particle size plays on observed fluo-
rescence properties and thus in the Perring-style particle clas-
sification. We also discuss several particle analysis strategies,
including the commonly used fluorescence threshold defined
as the mean instrument background (forced trigger; FT) plus
3 standard deviations (
σ)
of the measurement. Changing the
particle fluorescence threshold was shown to have a signifi-
cant impact on fluorescence fraction and particle type classi-
fication. We conclude that raising the fluorescence threshold
from FT
+
3
σ
to FT
+
9
σ
does little to reduce the rela-
tive fraction of biological material considered fluorescent but
can significantly reduce the interference from mineral dust
and other non-biological aerosols. We discuss examples of
highly fluorescent interfering particles, such as brown car-
bon, diesel soot, and cotton fibers, and how these may im-
pact WIBS analysis and data interpretation in various indoor
and outdoor environments. The performance of the particle
asymmetry factor (AF) reported by the instrument was as-
sessed across particle types as a function of particle size,
and comments on the reliability of this parameter are given.
A comprehensive online supplement is provided, which in-
cludes size distributions broken down by fluorescent parti-
cle type for all 69 aerosol materials and comparing threshold
strategies. Lastly, the study was designed to propose analy-
sis strategies that may be useful to the broader community
of UV-LIF instrumentation users in order to promote deeper
discussions about how best to continue improving UV-LIF
instrumentation and results.
