Bacterial community structure in atmospheric particulate matters of different sizes during the haze days in Xi'an, China

Highlights: • Bacteria community structures in PM_2.5, PM₁₀ and TSP on hazy days were examined. • High-throughput sequencing method was used for bacterial community profiles. • Source tracking analysis was used to explore sources of airborne microbes. • The bacterial abundance and diversity in different particle sizes are different. • Haze pollution had no significant effects on bacterial community structures. Serious air pollution events have frequently occurred in China associated with the acceleration of urbanization and industrialization in recent years. Exposure to atmospheric particulate matter (PM) of high concentration can lead to adverse effects on human health. Airborne bacteria are important constituents of microbial aerosols and contain lots of pathogens. However, variations in bacterial community structure in atmospheric PM of different sizes (PM_2.5, PM₁₀ and TSP) have not yet been explored. In this study, PM samples of different sizes were collected during the hazy days from Jul.2016 to Apr.2017 to determine bacterial diversity and community structure. Samples from soils and leaf surfaces were also collected to determine potential sources of bacterial aerosols. High-throughput sequencing technology was used generate bacterial community profiles, where we determined their diversity and abundances in the samples. Results showed that the dominant bacterial community structures in PM_2.5, PM₁₀ and TSP were strongly similar. Compared with non-haze days, the relative abundances of most bacterial pathogens on the haze days did not increase. Meanwhile, temperature, O₃ and NO₂ had more significant effects on bacterial community than the other environmental factors. Source tracking analysis indicated that the airborne bacteria might be not from local environment. It may come from the entire city or other regions by long distance airflow transport. Results of this study improved our understanding of the influence of bioaerosols on human health and the potential sources of airborne microbes.