Assessment of seasonal variations in concentration, particle-size distribution, and taxonomic composition of airborne fungi in a courtyard space

Abstract As people desire contact with the natural environment and comfortable living, modern buildings are increasingly incorporating the design of courtyard spaces. Hence, it is of interest to investigate the fungal air quality of courtyard spaces. This study aimed to investigate seasonal patterns of airborne fungal concentration, particle-size distribution, and taxonomic composition by using air microbial samplers and combining culture and molecular techniques. The results indicated that fungal concentration varied between seasons, peaking in autumn (825 ± 260 CFU/m3) and being the lowest in winter (617 ± 197 CFU/m3). Spearman's correlation analysis showed that fungal concentrations were positively correlated with relative humidity and wind speed. The relative humidity and wind speed supported fungal dispersion, whereas temperature negatively affected fungal dispersion in a multiple linear regression model. The fungal concentrations corresponding to “not excellent” in the Air Quality Index (AQI: >50) were higher than those corresponding to “excellent” (AQI: 0–50). The airborne fungal particle sizes in the range 1.1–3.3 μm (>58%) were predominant in all four seasons. In all four seasons, the airborne fungi had count median diameters ranging from 1.60 μm to 1.80 μm, allowing the fungi to penetrate the terminal bronchi. Verticillium (75.9%) and Cladosporium (27.4%) were the most abundant fungal genera in spring and summer, respectively. Flammulina was predominant in autumn and winter, accounting for 35.2% and 31.3%, respectively. Moreover, 14 fungal genera that contained allergenic or pathogenic species were identified in all four seasons. The highest mean average daily dose rates of airborne fungi was found in autumn. These findings will provide information for creating a more reasonable, comfortable, and healthier courtyard space air environment.