The composition, physical and chemical properties, sources, and temporal and spatial changes in airborne particulate matter have been extensively investigated in previous studies. However, less is known about bioaerosols, which are mainly composed of bacteria and fungi and constitute up to 25% of the total airborne particulate matter. In this study, we used inductively coupled plasma mass spectrometry and ion chromatography to determine the concentrations of trace elements and water-soluble ions in atmospheric particulates, respectively. These analyses were combined with high-throughput sequencing methods and real-time quantitative polymerase chain reaction to analyze the microbial compositions in PM1.0, PM2.5, and PM10 samples, which were collected from July to September in Hefei City. The results showed that there were no significant differences in the bacterial community diversity across the three size fractions (analysis of variance (ANOVA), P>0.05). The bacterial and fungal community diversities on sunny days were lower than those on rainy days, and the bacterial community diversity in all samples was significantly higher than the fungal community diversity (ANOVA, P<0.01). The predominant bacterial phyla were Proteobacteria (46.19%), Firmicutes (33.42%), Bacteroidetes (10.99%), Cyanobacteria (3.33%), and Actinobacteria (2.11%). Ascomycota (73.23%), Basidiomycota (5.78%), Mortierellomycota (3.41%), and Mucoromycota (0.10%) were the dominant fungal phyla. Our results indicated that soils, plant leaves, and animal feces were the dominant sources of airborne bacterial communities in Hefei City, and the main sources of the fungal communities were plant leaves and soils. The bacterial community was mainly affected by K, Pb, Al, Fe, Mg, Ca, Na+, NO2-, and wind speed, and the main influencing factors of the fungal community were V, Mn, Sr, NO2-, NO3-, Na+, Cl-, the air quality index, and PM10. In addition, nine specific bacteria and fungi that are linked to human health risks were identified, including Acinetobacter, Streptococcus, Enterobacter, Pseudomonas, Delftia, Serratia, Trichoderma, Alternaria, and Aspergillus, which can lead to a wide range of diseases in humans and other organisms. The research results are helpful for revealing the various characteristics of airborne microbial communities, their influencing factors, and their impacts on human health, and are an important reference for subsequent research and the formulation of government policies.
Keywords: Hefei; high-throughput sequencing; microbial community; particulate matter; pathogen.