Autofluorescence of atmospheric bioaerosols: spectral fingerprints and taxonomic trends of pollen

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.www.atmos-meas-tech.net/6/3369/2013/ Atmos. Meas. Tech., 6, 3369-3392, 2013

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

“…Supermicron particles of these pure materials would not be expected in a real-world environment but are present as dilute components of complex biological material and are useful here for comparison. In general, the spectral properties sum- marized here match well with fluorescence excitation emission matrices presented by Pöhlker et al (2012Pöhlker et al ( , 2013 In contrast to the particles of biological origin, a variety of non-biological particles were aerosolized in order to elucidate important trends and possible interferences. The majority of non-biological particles shown in the bottom row of Fig.…”

Characterisation of bioaerosol emissions from a Colorado pine forest: results from the BEACHON-RoMBAS experiment

“…Further, some types of non-biological material (e.g. certain polycyclic aromatic hydrocarbons and light-absorbing SOA compounds) can fluoresce at wavelengths used by the UV-LIF instruments including WIBS, introducing interference and uncertainty (Gabey et al, 2013;Pöhlker et al, 2013). These interferences, however, can be mitigated in measurement locations that are not heavily impacted by pollution sources and where biofluorescent particles are expected to dominate.…”

Photophoretic trapping-Raman spectroscopy for single pollens and fungal spores trapped in air

“…Light at 488 nm is known to excite relatively strong fluorescence in bacteria and tree leaves [8]. Sporopollenin in pollens and fungal spores is reported to fluoresce in the 400-650 nm range with high fluorescence intensity when excited at 300-550 nm [56,57]. Flavins are likely to be a main contributor to the fluorescence in the 500-580 nm range in bacteria, but probably contribute a much smaller fraction of the fluorescence in this range in pollens and fungal spores because they have many other fluorescent molecules [56,57].…”