A large amount of fluffy caktins appears in spring in Xi'an that may cause air pollution and lead to health risks such as asthma. In this study, bioaerosol, PM2.5, and fluffy catkins were collected from different sample points (traffic site and campus site) in Xi'an in spring. The variations in bioaerosol, fluffy catkins, and the bacterial community structure were investigated using culture-dependent and high-throughput sequencing methods. The results showed that the concentration of culturable bacteria was significantly higher (P=0.027) at the traffic site. The concentration of culturable bacteria at the traffic site was 2.7 times that of fungi, whereas the concentration of culturable fungi at the campus site was 1.4 times higher than that of bacteria. The peak concentrations of culturable bacteria and fungi appeared at 08:00 a.m. The size distribution of culturable bacteria showed a bimodal pattern, whereas that of culturable fungi showed a unimodal distribution. Soil and vegetation were the main sources of atmospheric microorganisms (85.9%), and Proteobacteria was the most abundant phylum in both fluffy catkins and PM2.5, accounting for 91.3% (traffic site) and 99.1% (campus site) of the fluffy catkins. Actinobacteria, Firmicutes, Bacteroidetes, Cyanobacteria, and Deinococcus-Thermus were the dominant phyla in PM2.5. Some genera were opportunistic pathogen bacteria in the fluffy catkins, such as Enterobacter and Pseudomonas, which can lead to infection and diarrhea risks. These results could provide fundamental data on potential health risks of spring-borne bioaerosols.
Keywords: community structure; culturable microorganisms; fluffy catkins; health effects; intraday changes.