Experimental campaign on bioaerosols in the atmosphere at two sites in Northern Europe in spring 2021. Bioaerosol_campaign_2021

A coordinated observational and modelling campaign targeting the biogenic aerosols in the air was performed during spring 2021 in two locations in Northern Europe: Helsinki (Finland) and Siauliai (Lithuania), approximately 500 km from each other in north-south direction. The campaign started on 1 March 2021 in Siauliai (15 March in Helsinki) and continued till end of April in Siauliai (end of May in Helsinki), thus recording the transition of the atmospheric biogenic aerosols profile from winter to summer. The observations included a variety of samplers working on different principles. The core of the program was based on 2- and 2.4--hourly sampling in Helsinki Siauliai, respectively, with sticky slides (Hirst 24-hours trap in Helsinki, Rapid-E slides in Siauliai). The slides were subsequently processed extracting the DNA from the collected aerosols, which was further sequenced using the 3-rd generation sequencing technology. The core sampling was accompanied with daily and daytime sampling using standard filter collectors. The hourly aerosol concentrations at the Helsinki monitoring site were obtained with the Poleno flow cytometer, which could recognize some of the aerosol types. The sampling campaign was supported by numerical modelling. For every sample, the SILAM model was applied to calculate its footprint and to predict the anthropogenic and natural aerosol concentrations, at both observation sites. The analysis of the campaign results is on-going. Its first conclusions confirmed the feasibility of the DNA collection by the applied techniques: most of them delivered substantial amount of DNA, in about-half of the cases sufficient for direct DNA sequencing without the PCR step. We also noticed very substantial variability of the DNA yield, generally not following the diurnal variations of the total-aerosol concentrations, which themselves showed very substantial variability not related to daytime. An expected upward trend of the biological material amount towards summer was indeed observed but the day-to-day variability was very large. Understanding the causes for the variability and in-depth analysis of the biological species identified by the DNA sequencing is the main goal of the analysis. Key words: bioaerosols, pollen, fungi spores, automatic pollen monitoring, metabarcoding, eDNA, 3rd generation DNA sequencing.