Ambient measurements of biological aerosol particles near Killarney, Ireland: a comparison between real-time fluorescence and microscopy techniques

Abstract

Abstract. Primary biological aerosol particles (PBAPs) can contribute significantly to the coarse particle burden in many environments. PBAPs can thus influence climate and precipitation systems as cloud nuclei and can spread disease to humans, animals, and plants. Measurement data and techniques for PBAPs in natural environments at high time-and size resolution are, however, sparse, and so large uncertainties remain in the role that biological particles play in the Earth system. In this study two commercial real-time fluorescence particle sensors and a Sporewatch single-stage particle impactor were operated continuously from 2 August to 2 September 2010 at a rural sampling location in Killarney National Park in southwestern Ireland. A cascade impactor was operated periodically to collect size-resolved particles during exemplary periods. Here we report the first ambient comparison of a waveband integrated bioaerosol sensor (WIBS-4) with a ultraviolet aerodynamic particle sizer (UV-APS) and also compare these real-time fluorescence techniques with results of fluorescence and optical microscopy of impacted samples. Both real-time instruments showed qualitatively similar behavior, with increased fluorescent bioparticle concentrations at night, when relative humidity was highest and temperature was lowest.The fluorescent particle number from the FL3 channel of the WIBS-4 and from the UV-APS were strongly correlated and dominated by a 3 µm mode in the particle size distribution. The WIBS FL2 channel exhibited particle modes at approx. 1 and 3 µm, and each was correlated with the concentration of fungal spores commonly observed in air samples collected at the site (ascospores, basidiospores, Ganoderma spp.). The WIBS FL1 channel exhibited variable multimodal distributions turning into a broad featureless single mode after averaging, and exhibited poor correlation with fungal spore concentrations, which may be due to the detection of bacterial and non-biological fluorescent particles. Cladosporium spp., which are among the most abundant fungal spores in many terrestrial environments, were not correlated with any of the real-time fluorescence channels, suggesting that the real-time fluorescence instruments are relatively insensitive to PBAP classes with dark, highly absorptive cell walls.Fluorescence microscopy images of cascade impactor plates showed large numbers of coarse-mode particles consistent with the morphology and weak fluorescence expected of sea salt. Some of these particles were attached to biological cells, suggesting that a marine source influenced the PBAPs observed at the site and that the ocean may be an important contributor to PBAP loadings in coastal environments.

Systematic characterization and fluorescence threshold strategies for the wideband integrated bioaerosol sensor (WIBS) using size-resolved biological and interfering particles

“…Ultimately, further analysis methods, including clustering techniques (e.g., Crawford et al, 2015Crawford et al, , 2016Ruske et al, 2017), will likely need to employed to further improve discrimination between ambient particles and to reduce the relative rate of misidentification. It should also be noted, however, that a number of ambient studies have compared results of UV-LIF instruments with complementary techniques for bioaerosol detection and have reported favorable comparisons (Healy et al, 2014;Gosselin et al, 2016;. So while uncertainties remain, increasing anecdotal evidence supports the careful use of UV-LIF technology for bioaerosol detection.…”

“…Both the WIBS and UV-APS, in various version updates, have been applied to many types of studies regarding outdoor aerosol characterization. For example, they have been important instruments: in the study of ice nuclei Mason et al, 2015;Twohy et al, 2016), toward the understanding of outdoor fungal spore concentrations (Gosselin et al, 2016;Saari et al, 2015a;O'Connor et al, 2015b), to investigate the concentration and properties of bioaerosols from long-range transport (Hallar et al, 2011), in tropical aerosol Whitehead et al, 2010Whitehead et al, , 2016Huffman et al, 2012;Valsan et al, 2016), in urban aerosol Saari et al, 2015b;Yu et al, 2016), from composting centers (O'Connor et al, 2015b), at high altitude Gabey et al, 2013;Perring et al, 2015;Ziemba et al, 2016), and in many other environments (Healy et al, 2014;Li et al, 2016;O'Connor et al, 2015a). The same instrumentation has been utilized for a number of studies involving the built, or indoor, environment as well (Wu et al, 2016).…”

Regional-scale simulations of fungal spore aerosols using an emission parameterization adapted to local measurements of fluorescent biological aerosol particles

“…Virtually every ambient measurement study performed with the WIBS or UV-APS to date has shown a dominant FBAP mode peaking at 2-4 µm in size Gabey et al, 2010;Toprak and Schnaiter, 2013;Healy et al, 2014). For example, the FBAP size distributions measured at each of the four sampling locations discussed here is shown in Fig.…”

“…fungal spores, bacteria, and leaf fragments). Detected particles are categorized as fluorescent biological aerosol particles (FBAP), which may broadly be considered a lower limit for the abundance of PBAP Pöhlker et al, 2012;Healy et al, 2014). FBAP were measured at four different locations (Table 1) concurrently during three focus periods in summer 2010 and fall 2010.…”

Evaluation of machine learning algorithms for classification of primary biological aerosol using a new UV-LIF spectrometer

“…Nonetheless, the practicality of long-term, continuous, real-time monitoring and discrimination of at least some of these properties for the more common types has already been demonstrated, e.g. at rural and semi-rural background sites in Germany, Ireland and Finland (Healy et al, 2014;Toprak and Schnaiter, 2013;Schumacher et al, 2013).…”