RESUMEN
To explore the bioaerosol composition characteristics and sources in urban areas and mountains, three sample sites were selected in urban (urban, suburban) and southern mountainous areas in Xi'an, and air, soil, and leaf samples were simultaneously collected. The fungi and bacteria community structures at different sampling sites were analyzed through a high-throughput sequencing method, and their spatio-temporal variations were also examined. Moreover, a source track technique was used to identify the source of microorganisms in the air. The results showed that the fungi and bacteria at different sampling sites were significantly different, indicating that the geographical location has a significant influence on the community structure of microorganisms in the air. In winter, more potential fungal pathogens and bacterial pathogens were detected in urban areas with high relative abundance and diversity. In addition, the results showed that the main local source of fungi and bacteria was the leaf surface, of which the contribution rate of bacteria in the air fine particles was up to (55±30)%. This study can provide a scientific basis for understanding the characteristics of microbial pollution in the atmosphere, and for air environment quality evaluation and disease prevention in China.