Study On The Distribution Characteristics Of Atmospheric Microbes In Typical Arid And Semi-Arid Regions Of China Based On Fluorescence Method

Atmospheric microbes are widely distributed and have important environmental,climatic,and health effects.China has a large area of arid land,with a fragile ecological environment and severe land desertification.Under the influence of global warming,frequent sand and dust events have intensified land desertification,and the area of arid and semi-arid regions is constantly expanding.Arid and semi-arid regions are important sources of dust emissions and their atmospheric microbes may be a potential threat to ecosystems and human health in downstream areas.However,the characteristics of aerosols and their microbes in arid and semi-arid regions have not been fully studied,and furthermore,how temperature,a known important driver,will affect airborne microbial concentrations and bacterial abundances has not been studied in this region.Therefore,using fluorescence spectroscopy,fluorescence microscopy and 16 S rRNA high-throughput sequencing,we studied aerosol samples from typical arid and semiarid regions of China(Inner Mongolia(IM),Namco(NMC),Yuzhong(YZ)),analyzed their fluorescence characteristics and spatial-temporal distribution characteristics of atmospheric microbial number concentration,and discussed the impact of temperature on aerosol microorganisms in semi-arid region.The main conclusions are as follows:(1)Aerosol samples from IM and NMC contain four fluorescent components:tyrosine,tryptophan,phenylalanine and humic substances,while aerosol samples from YZ have three fluorescent components: tyrosine,tryptophan and phenylalanine.The relative concentrations of these substances have significant spatial and temporal differences.There are significant spatial and temporal differences in the fluorescence parameters of aerosol samples,and the organic matter in aerosols in typical arid and semi-arid regions of China is largely derived from microbes,while the degree of humification is low.The daily variation of fluorescence parameters of aerosol samples inside and outside the sampling box in Yuzhong area showed that aerosols under natural conditions are mainly influenced by atmospheric oxidation and photochemical processes,and microbial activities are more active at noon,while microbes and their metabolites in the atmosphere at open places will escape rapidly.(2)Atmospheric microbial count concentrations show significant spatial and temporal differences.Atmospheric microbial concentrations between regions in order from high to low for IM(6.334 × 10~5 particles/m~3),YZ(1.813 × 10~5 particles/m~3),NMC(0.652 × 10~5 particles/m~3),may come from the regional differences in microbial emissions from surface vegetation and in air quality.The number concentration of atmospheric microorganisms in IM during the day is significantly higher than that at night,which may be attributed to higher daytime temperature,causing stronger groundair exchange and more active plant metabolism,resulting in more microbes emitted into the air from the land and plant surfaces.(3)Aerosol fluorescence component content and atmospheric microbial concentration were correlated.The regression analysis of aerosol fluorescence characteristics and atmospheric microbial number concentration showed that fluorescence excitation-emission matrix(EEM)has the ability to characterize the microbial content of aerosols,which provides the possibility of using EEM for the detection of atmospheric microbes.(4)Microbial concentrations in the air increased significantly with the increase of temperature,and each increase of one degree Celsius would be accompanied by an increase of 5.9 × 10~4 microbial particles/m~3,whose reason may be that the increase of temperature is conducive to the release of microbes from the soil into the air,ae well as promoting the growth of microorganisms.The increase in airborne microbial concentrations with increasing temperatures may lead to serious public health risks,which warrants concern and alarm.With rising temperature,relative abundance of Firmicutes decreases;and relative abundances of Enhydrobacter,Massilia,Pediococcus,Pseudomonas,and Blastococcus,all of which are bacteria that may have complex environmental,climatic,and human health impacts,increase.Such alterations may pose a threat to human health and increase public health risks,while having complex effects on weather and,to some extent,influencing and altering regional climate.