Variations of pollen concentration in urban alleys of park city and the transmission pattern during the period of high allergenic risk: Taking Qingyang District of Chengdu City as an example.

Pollen (spores and pollen) allergy caused by green areas is one of the most serious environmental epidemics endangering urban public health. The pollen allergy rate in China reached 17.8% in 2022, characterized by a wide age range of onset, severity and diversity of symptoms. The aims of this study were to verify the consistency of the prediction results of pollen concentration and the index of allergenicity of urban green zones () equation, and to clarify the dispersal pattern of tree pollen in the urban alleys of cities with high density of static wind. We selected representative high, medium and low allergenic areas based on the allergenic stress in urban alleys of Qingyang District, Chengdu calculated by equation, and monitored the pollen concentrations by selecting points and indicator species within the three allergenic areas. There was a consistency in the variation of pollen concentration in urban alleys of the three areas, with the highest pollen concentration in March. Mean pollen concentration showed a pattern of spring > autumn > summer > winter. The main pollen sources belonged to , , and , accounting for 42.4%, 16.3%, 9.0% and 6.5% of the total pollen, respectively. Wind speed had the greatest effect on pollen concentration and its dispersal distance in the urban alley. The horizontal dispersal distance of pollen was up to 260 m, and the number of pollen showed a significant negative linear correlation with the distance away from the pollen sources. The concentration of exotic pollen collected at the high site (4.5 m above ground) was much lower than that at the near-ground site (1.5 m above ground), but without difference in the types of pollen. The results of allergenic risk predicted by the equation were consistent with the actual measured pollen concentration, which could be used in high-density static wind city.