Abstract
Abstract. Primary biological aerosol particles (PBAP) are important factors in atmospheric cycling, climate, and public health. Pollen is a major fraction of PBAP and is receiving increasing attention due to its high allergenic potential and the associated impacts on personal life quality and economy. Recently, autofluorescence-based techniques have proven to be valuable tools for real time, in situ quantification and classification of PBAP. First studies suggest that the autofluorescence of pollen may be sufficiently selective to be utilized for an automated and real-time monitoring of pollen in ambient air. However, the degree of selectivity autofluorescence can provide is still in question and actively debated. This study addresses the origin, properties, and selectivity of autofluorescence from natural pollen by fluorescence microscopy and spectroscopy measurements along with a systematic synthesis of related literature. We show that dry pollen reveals characteristic and reproducible autofluorescence signatures which are shaped by cell wall associated fluorophores, such as phenolic compounds and carotenoid pigments. In addition, fluorescence signals from proteins and chlorophyll a were observed in some species. The abundance and intensity of the individual fluorescence signals show certain taxonomic trends and allow systematic differentiation from bacteria and fungal spores due to the lack of proteins on the grain surface. Principal component analysis was used to explore the discrimination potential of pollen autofluorescence, in combination with size and shape, revealing a differentiation of pollen on family level. Our results help explore the levels of selectivity that autofluorescence-based techniques can provide to PBAP analysis and will support the development and application of autofluorescence-based detectors for monitoring of allergenic pollen in the atmosphere.
Highlights
1.1 Primary biological aerosol particles and atmospheric relevancePrimary biological aerosol particles (PBAP)1, called bioaerosols, consist of a complex mixture of small biogenic particles, which are directly released from the biosphere into the atmosphere (Després et al, 2012)
Pollen grains exhibit strong emission of autofluorescent light originating from both their cytosol and their complex, multilayered cell wall (e.g., Asbeck, 1955; Driessen et al, 1989; Castro et al, 2010)
The natural fluorescence of pollen has been used as a valuable tool for quick and noninvasive in situ analyses of fresh and fossil pollen in diverse scientific fields, such as atmospheric science (e.g., Ronneberger et al, 2002; Mitsumoto et al, 2010; Pan et al, 2011), geology and palynology (e.g., Phillips, 1972; Yeloff and Hunt, 2005), as well as plant physiology and botany (e.g., Roshchina, 2003, 2008, 2012; Grienenberger et al, 2009)
Summary
1.1 Primary biological aerosol particles and atmospheric relevance. Primary biological aerosol particles (PBAP), called bioaerosols, consist of a complex mixture of small biogenic particles, which are directly released from the biosphere into the atmosphere (Després et al, 2012). Bioaerosols are globally ubiquitous and can dominate the coarse aerosol burden in certain ecosystems (e.g., Pöschl et al, 2010). PBAP have received increased attention in atmospheric science due to their impact on atmospheric chemistry and physics (Pöschl, 2005; Möhler et al, 2007; Deguillaume et al, 2008), their important role in biogeochemical (Gorbushina and Broughton, 2009; Mahowald et al, 2011) and hydrological cycling (Morris et al, 2008; Huffman et al, 2013; Prenni et al, 2013; Tobo et al, 2013), as well as their influence on public and agricultural health (D’Amato, 2000; Bernstein et al, 2004).
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