Abstract
Abstract. Primary biological aerosol particles (PBAPs) in the atmosphere are highly relevant for the Earth system, climate, and public health. The analysis of PBAPs, however, remains challenging due to their high diversity and large spatiotemporal variability. For real-time PBAP analysis, light-induced fluorescence (LIF) instruments have been developed and widely used in laboratory and ambient studies. The interpretation of fluorescence data from these instruments, however, is often limited by a lack of spectroscopic information. This study introduces an instrument – the Spectral Intensity Bioaerosol Sensor (SIBS; Droplet Measurement Technologies (DMT), Longmont, CO, USA) – that resolves fluorescence spectra for single particles and thus promises to expand the scope of fluorescent PBAP quantification and classification. The SIBS shares key design components with the latest versions of the Wideband Integrated Bioaerosol Sensor (WIBS) and the findings presented here are also relevant for the widely deployed WIBS-4A and WIBS-NEO as well as other LIF instruments. The key features of the SIBS and the findings of this study can be summarized as follows. Particle sizing yields reproducible linear responses for particles in the range of 300 nm to 20 µm. The lower sizing limit is significantly smaller than for earlier commercial LIF instruments (e.g., WIBS-4A and the Ultraviolet Aerodynamic Particle Sizer; UV-APS), expanding the analytical scope into the accumulation-mode size range. Fluorescence spectra are recorded for two excitation wavelengths (λex=285 and 370 nm) and a wide range of emission wavelengths (λmean=302–721 nm) with a resolution of 16 detection channels, which is higher than for most other commercially available LIF bioaerosol sensors. Fluorescence spectra obtained for 16 reference compounds confirm that the SIBS provides sufficient spectral resolution to distinguish major modes of molecular fluorescence. For example, the SIBS resolves the spectral difference between bacteriochlorophyll and chlorophyll a and b. A spectral correction of the instrument-specific detector response is essential to use the full fluorescence emission range. Asymmetry factor (AF) data were assessed and were found to provide only limited analytical information. In test measurements with ambient air, the SIBS worked reliably and yielded characteristically different spectra for single particles in the coarse mode with an overall fluorescent particle fraction of ∼4 % (3σ threshold), which is consistent with earlier studies in comparable environments.
Highlights
This study introduces an instrument – the Spectral Intensity Bioaerosol Sensor (SIBS; Droplet Measurement Technologies (DMT), Longmont, CO, USA) – that resolves fluorescence spectra for single particles and promises to expand the scope of fluorescent Primary biological aerosol particles (PBAPs) quantification and classification
The SIBS shares key design components with the latest versions of the Wideband Integrated Bioaerosol Sensor (WIBS) and the findings presented here are relevant for the widely deployed WIBS-4A and WIBS-NEO as well as other lightinduced fluorescence (LIF) instruments
The results shown here are comparable to multiple WIBS studies (e.g., Hernandez et al, 2016; Perring et al, 2015; Savage et al, 2017), in which fluorescence emission intensities at λex = 280 nm show a tendency to be higher than those at λex = 370 nm
Summary
Aerosol particles are omnipresent in the atmosphere, where they are involved in many environmental and biogeochemical processes (e.g., Baron and Willeke, 2001; Després et al, 2012; Fuzzi et al, 2006; Hinds, 1999; Pöschl, 2005; Pöschl and Shiraiwa, 2015). Primary biological aerosol particles (PBAPs), termed bioaerosols, represent a diverse group of airborne particles consisting of whole or fragmented organisms including, e.g., bacteria, viruses, archaea, algae, and reproductive units (pollen and fungal spores), as well as decaying biomass (e.g., Deepak and Vali, 1991; Després et al, 2012; Fröhlich-Nowoisky et al, 2016; Jaenicke, 2005; Madelin, 1994; Pöschl, 2005) and can span sizes from a few nanometers up to ∼ 100 μm (Hinds, 1999; Schmauss and Wigand, 1929). Detailed information on biological fluorophores can be found elsewhere (Pöhlker et al, 2012, and references therein)
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
