Abstract
Abstract. Bioaerosols pose risks to human health and agriculture and may influence the evolution of mixed-phase clouds and the hydrological cycle on local and regional scales. The availability and reliability of methods and data on the abundance and properties of atmospheric bioaerosols, however, are rather limited. Here we analyze and compare data from different real-time ultraviolet laser/light-induced fluorescence (UV-LIF) instruments with results from a culture-based spore sampler and offline molecular tracers for airborne fungal spores in a semi-arid forest in the southern Rocky Mountains of Colorado. Commercial UV-APS (ultraviolet aerodynamic particle sizer) and WIBS-3 (wideband integrated bioaerosol sensor, version 3) instruments with different excitation and emission wavelengths were utilized to measure fluorescent aerosol particles (FAPs) during both dry weather conditions and periods heavily influenced by rain. Seven molecular tracers of bioaerosols were quantified by analysis of total suspended particle (TSP) high-volume filter samples using a high-performance anion-exchange chromatography system with pulsed amperometric detection (HPAEC-PAD). From the same measurement campaign, Huffman et al. (2013) previously reported dramatic increases in total and fluorescent particle concentrations during and immediately after rainfall and also showed a strong relationship between the concentrations of FAPs and ice nuclei (Huffman et al., 2013; Prenni et al., 2013). Here we investigate molecular tracers and show that during rainy periods the atmospheric concentrations of arabitol (35.2 ± 10.5 ng m−3) and mannitol (44.9 ± 13.8 ng m−3) were 3–4 times higher than during dry periods. During and after rain, the correlations between FAP and tracer mass concentrations were also significantly improved. Fungal spore number concentrations on the order of 104 m−3, accounting for 2–5 % of TSP mass during dry periods and 17–23 % during rainy periods, were obtained from scaling the tracer measurements and from multiple analysis methods applied to the UV-LIF data. Endotoxin concentrations were also enhanced during rainy periods, but showed no correlation with FAP concentrations. Average mass concentrations of erythritol, levoglucosan, glucose, and (1 → 3)-β-D-glucan in TSP samples are reported separately for dry and rainy weather conditions. Overall, the results indicate that UV-LIF measurements can be used to infer fungal spore concentrations, but substantial development of instrumental and data analysis methods appears to be required for improved quantification.
Highlights
Primary biological aerosols particles (PBAPs) are of keen interest within the scientific community, partially because methods for their quantification and characterization are advancing rapidly (Huffman and Santarpia, 2017; Sodeau and O’Connor, 2016)
It was shown that the concentration of fluorescent aerosol particles (FAPs) measured during BEACHON-RoMBAS increased dramatically during and after periods of rain (Crawford et al, 2014; Huffman et al, 2013; Schumacher et al, 2013) and that these particles were associated with high concentrations of ice nucleating particles that could influence the formation and evolution of mixed-phase clouds (Huffman et al, 2013; Prenni et al, 2013; Tobo et al, 2013)
Increased concentrations of fluorescent aerosol particles and ice nuclei attributed to having a biological origin were observed during and immediately after rain events throughout the BEACHON-RoMBAS study in 2011 (Huffman et al, 2013; Prenni et al, 2013; Schumacher et al, 2013)
Summary
Primary biological aerosols particles (PBAPs) are of keen interest within the scientific community, partially because methods for their quantification and characterization are advancing rapidly (Huffman and Santarpia, 2017; Sodeau and O’Connor, 2016). The term PBAPs, or equivalently bioaerosols, generally comprises several classes of airborne biological particles including viruses, bacteria, fungal spores, pollen, and their fragments (Després et al, 2012; FröhlichNowoisky et al, 2016). Fungal spores are of particular atmospheric interest because they can cause a variety of deleterious health effects in humans, animals, and agriculture, and it has been shown that they can represent a significant fraction of total organic aerosol emissions (Deguillaume et al, 2008; Gilardoni et al, 2011; Madelin, 1994), especially in tropical regions (Elbert et al, 2007; Huffman et al, 2012; Pöschl et al, 2010; Zhang et al, 2010). Asthma and allergies have shown notable increases during thunderstorms due to elevated bioaerosol concentrations (Taylor and Jonsson, 2004) especially when attributed to fungal spores (Allitt, 2000; Dales et al, 2003)
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