High levels of primary biogenic organic aerosols in the atmosphere in summer are driven by only a few microbial taxa from the leaves of surrounding plants

Abstract. Primary biogenic organic aerosols (PBOA) represent a major fraction of coarse organic matter (OM) in air. Despite their implication in many atmospheric processes and human health problems, we surprisingly know little about PBOA characteristics (i.e., composition, dominant sources, and contribution to airborne-particles). In addition, specific primary sugar compounds (SCs) are generally used as markers of PBOA associated with Bacteria and Fungi but our knowledge of microbial communities associated with atmospheric particulate matter (PM) remains incomplete. This work aimed at providing a comprehensive understanding of the microbial fingerprints associated with SCs in PM10 (particles smaller than 10 µm) and their main sources in the surrounding environment (soils and vegetation). An intensive study was conducted on PM10 collected at rural background site located in an agricultural area in France. We combined high-throughput sequencing of Bacteria and Fungi with detailed physicochemical characterization of PM10, soils and plant samples, and monitored meteorology and agricultural activities throughout the sampling period. Results shows that in summer SCs in PM10 are a major contributor of OM in air, representing 0.8 to 13.5 % of OM mass. SCs concentrations are clearly determined by the abundance of only a few specific airborne Fungi and Bacteria Taxa. These microbial are significantly enhanced in leaf over soil samples. Interestingly, the overall community structure of Bacteria and Fungi are similar within PM10 and leaf samples and significantly distinct between PM10 and soil samples, indicating that surrounding vegetation are the major source of SC-associated microbial taxa in PM10 in rural area.