Airborne Quercus Pollen in SW Spain: Identifying Favourable Conditions for Atmospheric Transport and Potential Source Areas

The pollen grains of Quercus spp. (oak trees) are allergenic. This study investigates airborne Quercus pollen in SW Spain with the aim identifying favourable conditions for atmospheric transport and potential sources areas. Two types of Quercus distribution maps were produced. Airborne Quercus pollen concentrations were measured at three sites located in the Extremadura region (SW Spain) for 3 consecutive years. The seasonal occurrence of Quercus pollen in the air was investigated, as well as days with pollen concentrations ≥ 80 P m− 3. The distance that Quercus pollen can be transported in appreciable numbers was calculated using clusters of back trajectories representing the air mass movement above the source areas (oak woodlands), and by using a state-of-the-art dispersion model. The two main potential sources of Quercus airborne pollen captured in SW Spain are Q. ilex subsp. ballota and Q. suber. The minimum distances between aerobiological stations and Quercus woodlands have been estimated as: 40 km (Plasencia), 66 km (Don Benito), 62 km (Zafra) from the context of this study. Daily mean Quercus pollen concentration can exceed 1,700 P m− 3, levels reached not less than 24 days in a single year. High Quercus pollen concentration were mostly associated with moderate wind speed events (6–10 m s− 1), whereas that a high wind speed (16–20 m s− 1) seems to be associated with low concentrations.