Distribution Characteristics Of Airborne Microbes Over Northern China And Its Influencing Factors

The environmental and health effects of atmospheric microorganisms are the current research hotspots.Quantitative assessment of the effects requires an accurate understanding of the distribution characteristics of atmospheric microorganisms.Studies mainly focused on the changes of microbial concentrations and community structure characteristics in different seasons or pollution events.There were few systematic studies on the distribution characteristics of atmospheric microorganisms.Although atmospheric microorganism observation experiments have been carried out in many cities in China,but the research results could not be compared directly due to the different observation and analysis methods.In this study,the microorganisms were collected from the ground atmosphere in Inner Mongolia Autonomous Region,Qinghai Province,and Xinjiang Uygur Autonomous Region,and the upper atmosphere in Dunhuang,Gansu Province,By means of DAPI staining and 16S r DNA sequencing,we analyzed the distribution characteristics of microbial number concentration and bacterial communities in atmosphere,and discussed the effects of NDVI(Normalized Difference Vegetation Index)and meteorological factors(temperature,relative humidity and common pollutants)at the sampling sites on the distribution characteristics.The main conclusions were as follows:(1)The atmospheric microbial number concentration was 10~5-10~6particles/m~3in northern China,and the percentage of microbial number in the total number of particulate matters was about 1.5%-12.5%.The microbial number concentration is was central Inner Mongolia>eastern Inner Mongolia>around Qinghai Lake>western Taklamakan Desert>Dunhuang high altitude;the ratio of microorganisms are eastern Inner Mongolia>central Inner Mongolia>around Qinghai Lake>western Taklamakan Desert>Dunhuang high altitude,and the ground atmospheric microbial concentration and ratio were higher in relatively humid areas(Inner Mongolia region and around Qinghai Lake).(2)The results of Pearson correlation analysis showed that the microbial number concentration in the ground and upper atmosphere was positively correlated with the concentration of organic matter particles and mineral particles;except for the western Taklamakan Desert,the proportion of microbial number in the total number of particles was negatively correlated with the proportion of mineral particles in the ground atmosphere,but positively correlated in the upper atmosphere.(3)Proteobacteria,Firmicutes,Actinobacteria,and Bacteroidetes are the dominant bacterial phyla in the atmosphere and Gammaproteobacteria,Bacilli and Bacteroidia were the dominant bacterial classes,the dominant bacterial phyla(classes)were more abundant in the ground atmosphere than in the upper atmosphere.Wilcoxon rank sum test showed that there was no significant difference in the relative abundance of Firmicutes and Bacillus in ground atmospheric of different areas;The relative abundance of Halobacteria in Minfeng and Tazhong was significantly higher in the nighttime than in the daytime.(4)Comparing atmospheric bacterial community diversity indices(Shannon,Simpson and Chao1 indices)in different regions,we found that the diversity of bacterial communities in desert areas(Minfeng,Tazhong and western Taklamakan Desert)was higher than that in relatively humid areas(eastern Inner Mongolia and around Qinghai Lake);the diversity of bacterial communities in the desert edge(Minfeng)was significantly higher than that in the desert hinterland(Tazhong)).(5)We found that the microbial concentration in ground atmospheric was positively correlated with relative humidity,and the proportion of microbial count in the total number of particles was positively correlated with NDVI and relative humidity;the microbial concentration and proportion in ground and high-altitude atmospheric was negatively correlated with temperature;the diversity of bacterial community in ground atmospheric tended to decrease as NDVI increased;the Simpson and Shannon indices of airborne bacterial communities increased as temperature increased.