Continuous Fluorescent Bioaerosol Measurements for 18 Months Combined with Filter Sampling Validation

MADELEINE PETERSSON SJÖGREN, Jonas Jakobsson, Malin Alsved, Thomas Bjerring Kristensen, Tina Santl-Temkiv, Jakob Löndahl, Lund University, Sweden

     Abstract Number: 184
     Working Group: Bioaerosols

Abstract
Bioaerosols make up a diverse set of particles that are essential for reproduction of organisms, can transmit diseases, and have been proposed as important agents in atmospheric processes. However, the abundance and temporal and spatial variability of bioaerosols remain to be understood. The aim of this study was to do continuous bioaerosol measurements and compare these to meteorological factors and bioaerosol concentrations derived from filter sampling. To our knowledge, this is one of the longest continuous ambient bioaerosol measurements and the first long-term bioaerosol study in Sweden.

We used a real-time viable particle counter (BioTrak, TSI Inc.) for continuous detection and sizing of fluorescent biological aerosol particles (FBAP) in the range 1-12 µm at the Hyltemossa Aerosols, Clouds, and Trace gases Research Infrastructure (ACTRIS) station in the south of Sweden for 18 months (October 2020 to April 2022). In parallel with real time FBAP counting, a PM₁₀ filter sampler (Leckel SEQ47/50-RV) was operated. Each filter sampled 3-24 m³ of air and 112 filters were stained with acid gel stain (SYBR Green I) for identification and counting of bioaerosols with fluorescence microscopy.

The FBAP number concentrations were dominated by particles in the size range 1-3 µm and were significantly higher in the summer, with an average FBAP number concentration of 0.020 cm^-3, compared to all other seasons (P<0.0001). Lower concentrations were measured with real-time counting than with the filter collection and staining method. The filter counts showed that particles in the size range 1-3 µm only contained a low number of single bacteria but were dominated by aggregates of bacteria and fungal spores. The FBAP number concentrations correlated with air temperature (P<0.0001), relative humidity (P<0.01) and wind speed (P<0.05).