Contribution of land cover and wind to the airborne pollen recorded in a South European urban area

Airborne pollen assemblage depends on the land cover of the area surrounding the volumetric trap and the flow of air masses. In urban contexts, the amount of airborne pollen is the result of the contribution of both local green areas and extra-urban vegetation, in addition to wind direction and speed. The present study focused on the combined effects of land cover and wind on the airborne pollen recorded in Florence over a 5-year period, in order to identify the area from where most of the pollen comes to the city. The study revealed that Cupressaceae, Olea and Quercus pollen display a positive correlation among their pollen concentrations and the geographical distribution of their sources. The overall influence of maximum wind speed is greater than the number of calm wind days. The latter is appreciable only for the pollen of Cupressaceae and Olea, whose trees are located in the proximity of the urban area, in the southern part of the city. The results showed that the land cover configuration strongly influences the airborne pollen captured by volumetric traps; despite the prevalent wind directions, the vegetation of the reliefs surrounding the city can be considered as the greatest area of pollen contribution.