Bioaerosol’s contribution to the atmospheric Phosphorus in Athens, Greece

Phosphorus (P) is a key macronutrient vital for all organisms, and it undergoes redistribution between terrestrial and oceanic systems through processes such as atmospheric emission, transport, transformation, and deposition. P is a limiting factor for primary productivity in the east Mediterranean Sea and the atmosphere is an important source of P for the marine ecosystems. Atmospheric P is present as both organic and inorganic species in dissolved and particulate forms and originates from both natural and anthropogenic sources. However, its sources remain uncertain since observational data show that the prevailing fraction of soluble, bioavailable, atmospheric P cannot be attributed to desert dust. Bioaerosols have been proposed as important carriers of nutrients and especially of bioavailable P to the marine ecosystems, potentially contributing to the missing sources of atmospheric P in the Mediterranean. In this study, a large number (234) of ambient PM_2.5 24-h samples that were collected over a multi-yearlong sampling campaign (Dec. 2018 – Jul. 2021) conducted in Athens, one of the largest urban centres in south eastern Mediterranean, were analysed for total phosphorus (TP). In addition to P, chemical components, such as saccharides that are used as proxies of bioaerosols, but also organic carbon (OC), elemental carbon (EC), water-soluble OC, major inorganic anions and cations, elements of crustal origin and trace elements were determined. Preliminary results show the highest concentrations of TP and organic phosphorus (OP) in spring. Inorganic phosphorus exhibits similar levels throughout the seasons, with a small increase in spring. The observed concentrations of anhydro sugars were higher in winter and autumn than in summer due to biomass burning processes, while primary sugars and sugar alcohols indicative of bioaerosols increased throughout the growing season, peaking in spring as found also for total phosphorus concentrations. Positive Matrix Factorization analysis (PMF) is employed to identify the individual sources that affected the air samples and in particular P. Thus, the fraction of P in aerosols attributed to bioaerosol has been estimated. Aerosol sampling has been performed in the frame of the ERC PyroTRACH grant #726165. This work has been supported by the HFRI grant # 4050 BIOCAN.