The spatio-temporal distribution characteristics and influencing factors of airborne microbial components in ambient PM within a city scale.

PM-carried microorganisms, widely dispersed in the atmosphere, have garnered significant attention for their potential health impacts. However, the impact of spatio-temporal variations on bioaerosol distribution remains unclear. In this study, we collected PM samples across all seasons from industrial, urban, and rural areas of Nanjing, a Chinese megacity, and analyzed the spatio-temporal distribution of microorganisms and their influencing factors. Results revealed significant spatio-temporal variations in microbial diversity and abundance. Bacterial diversity and abundance were higher in autumn and winter, with notable seasonal differences in industrial and rural areas. Fungi exhibited regional variations, with higher diversity and abundance in industrial areas during spring and autumn, and peak abundance in urban and rural areas in winter. Additionally, key genera responded variably to spatio-temporal changes. Broadly adapted genera, such as Achromobacter (bacterium) and Cladosporium (fungus) remained stable across seasons, while taxa like Chloroplast and Epicoccum showed significant abundance fluctuations with environmental changes. Multifactorial analyses revealed bacterial communities were primarily influenced by temperature, wind speed, and air quality index (AQI), while fungi were also significantly impacted by humidity and population density. Correlation network analyses linked metals, carbon and nitrogen contents in PM to microbial abundance. Most bacterial genera were negatively correlated with chemical constituents, while fungi were more adaptive to these constituents and were positively correlated. This study offers insights into the spatio-temporal distribution of PM microbial components and the influence of environmental factors and aerosol chemistry on microbial communities, highlighting implications for air quality and pollution management in public health.