Bioaerosol Concentrtion And Bacterial Community Structure In Atmospheric Fine Particulate Matters In Xi'an

Recently,serious air pollution events frequently happen in China.Xi'an,the national center city of the northwest,is also experiencing heavy haze pollution.Atmospheric fine particulate matter?particulate matter with nominal mean aerodynamic diameters of?2.5?m?,as the primary pollutant of air pollution,has adverse effects on human health and environment.In this study,to better understand the relationship between fine particulate matter and environmental factors,airborne microbial samples were collected by an air sampler?ZR-3930,Qingdao,China?in Xi'an from September 2016 to October 2017,and then use Fluorescent Microscopic analysis and High-throughput sequencing technology to identify airborne microbes concentrations and bacterial communities.The concentration of airborne microbes and bacterial communities structure were comparably investigated in different seasons,haze and non-haze days and at various air quality levels.Correlations of bioaerosol levels with meteorological factors and pollution factors were also examined.The results are as follows:?1?The concentrations of airborne microbes in different seasons were significantly different.The concentrations of airborne microbes were highest in winter(1.8355×10⁵ cells·m^-3),followed by autumn and spring(1.0415×10⁵ cells·m^-3,1.1160×10⁵ cells·m^-3),and lowest in the summer(5.1500×10⁴ cells·m^-3);The Multiple liner regressions results of concentration and environment factors show that PM and temperature has major influence on airborne microbes concentration in each season.?2?The concentrations of airborne microbes on haze days(1.7065×10⁵ cells·m^-3)were significantly higher than those on non-haze days(8.0560×10⁴ cells·m^-3)?P<0.01?.Fine particulate matter has significantly affected the concentration in these two weather conditions.In addition,the concentrations of airborne microbes increased with air pollution levels.However,the concentration of airborne microbes on unit fine particulate matter was stable in each air quality level.?3?Results from principal component analysis?PCA?indicate that the concentrations of airborne microbes were mainly influenced by haze and meteorological factors.The effect of haze was more obvious than meteorological factors.?4?The abundance and diversity of bacterial community show significant difference?P<0.05?in different seasons.The diversity of bacterial communities in spring and summer were higher than autumn and winter.The dominant bacterial communities in phylum level in different seasons were similar,but the top genus under different seasons were different.?5?The abundance and diversity of bacterial communities on haze and non-haze days show no significant difference?P<0.05?.The bacterial communities in phylum and genus level also has no significant difference,but the abundance of bacterial communities were different.?6?A redundancy discriminant analysis?RDA?was used to explore the relationship between environment factors and bacterial communities.The result shows that all the environmental variables together can explain 86.96%of the variation in bacterial communities between samples.In addition,the Variation partition analysis?VPA?of meteorological factors and pollution factors show that both factors were shaping microbial communities?46.23%?,but the dominant factor was meteorological factors in all samples.The studies on the variation in concentration levels and community structure and composition of microorganisms in bioaerosols can better understand the component of microbes in the atmosphere.It can also be used as a biological indicator to assess air pollution levels and air quality.It is of great significance to control the air pollution,prevent epidemics and improve the quality of environment.