| The sand dust process can release dust particles into the upper atmosphere,and these dust particles can be transported over a long distance with air mass.The components of biological aerosols attached to particulate matter during transportation have essential impact on the ecological environment,human health,and climate of the downstream region.Currently,relevant research on biological aerosol transport during sandstorms are limited,and lack of in-depth investigation and research on the soil and atmosphere in the dust source areas.The correlation of microbial community between dust source areas and the downstream atmosphere further needs clarify.In the present study,the soil and air bacteria in sand dust source areas in desert and microbial communities in downstream cities were investigated.The characteristics and potential correlations of the soil,atmosphere and downwind urban microbial communities in the Asian dust source area(The Tengger Desert,the fourth largest desert in China)and the downwind city(Jinan City)were analyzed,and the potential impact of sand dust transport on downwind atmospheric bacterial communities was preliminary discussed.From March 30,2021 to April 24,2021,soil and ambient air samples were collected in the east of Tengger Desert,and ambient air samples were collected in Jinan.The composition and abundance of bacterial communities were revealed using 16S r RNA gene sequencing and q PCR.By identifying the composition and differences of bacterial communities,the Bug Base phenotype,and the FAPROTAX function,the similarity and differences of bacterial communities in sand and dust source areas and downstream cities,their physiological phenotypes,and the ecological function of airborne bacteria were clarified.The regional transport characteristics and correlations of typical sand and dust process were discussed.The main results were as follows.(1)Soil samples at the southeast of the Tengger Desert including sand,bush,grass lake and salt lakes were collected.Totally,40 samples including surface soil(0-1cm)and subsoil(1-5cm)were obtained,which showed obvious difference in physical and chemical properties,microbial quantity and community structure of different soil types in Tengger Desert.The surface soil nitrogen concentration was 0.4-0.6 g/kg and deep soil nitrogen concentration was 0.2-0.3 g/kg.The difference in soil phosphorus concentration under different depths was similar,with surface soil phosphorus concentration of 0.3-0.6 g/kg and deep soil phosphorus concentration of 0.3-0.5g/kg.Nitrogen concentration among different soil types showed that the bush>grass＿lake>sand>salt lakes in surface soil;In deep soil,that was salt lakes>grass＿lake>sand.There was no significant difference in phosphorus concentration among different soil types.The soil bacterial concentration is similar in surface and subsoil,with the total bacterial concentration of about 10~7copies/g and the nitrite reducing bacteria of about 10~5copies/g.Total bacteria and nitrite reducing bacteria in different soil types varied significantly,with a pattern of bush≈grass＿lake>sand>salt lakes is presented.At the phylum level,the dominant microorganisms in desert soil were Actinobacteria and Proteobacteria.At the genus level,the abundance of Planococcus in salt lake samples was higher than that of other soil types.The abundance of Nocardioides in sand samples is higher than that in other soil types.The microbial species in the samples of bush and grass＿lake are very similar.The abundance of salt tolerant bacteria in salt lakes was high.The soil source fineness and abundance are higher in sand.The abundance of photosynthetic related bacteria and rhizobia in soils with more plants in bush and grass＿lake is higher.(2)At the phylum level,Firmicutes and Proteobacteria were the dominant bacteria of air microorganisms in the Tengger Desert.At the genus level,Pseudomonas and Delftia were the dominant bacteria.Sanddust events had a significant impact on air microorganisms,and the airborne bacterial community varied greatly under different wind directions.In sand dust samples,the abundance of Bacteroidota and Cyanobacteria increased compared to clean samples,while the abundance of Campylobacter decreased compared to clean samples.During sand dust,some microorganisms in the surface of soil may be carried into the atmosphere by the wind,resulting in an increase in the abundance of soil bacteria in the atmosphere,while the abundance of bacteria related to human activities and grazing was reduced through dilution and diffusion by strong winds.Under the prevailing north wind,the abundance of soil bacteria(Cyanobacteria)from desert background areas increased.Under the prevailing south wind,the abundance of intestinal bacteria and bacteria(Fusobacteria)from human activity and grazing areas increased.Bacterial community during three typical sanddust events revealed significant differences than none dust samples.The representative bacteria of dust event 1 were Proteobacteria,which have a wide source and detected in water,soil,and human bodies.The representative bacteria,e.g.,Cyanobacteria in dust event 2 were mainly from the soil.The representative bacteria,e.g.,Fusobacteria,were mainly from humans and animals.(3)At the phylum level,Proteobacteria and Firmicutes were the dominant microorganisms in the atmosphere of Jinan.At the generic level,Delftia and Pseudomonas were the dominant bacteria.The dust event had obvious impact on the composition and abundance of airborne microorganisms in Jinan.At the phylum level,the abundance of Actinobacteria was higher in sand dust samples,while the abundance of Fusobacteria was higher in non-dust samples.At the genus level,during sandstorm,Bacillus and Pseudomonas,Hypnocyclicus,and Tolumonas have higher abundances in non-dust samples.During the observation period,bacterial community showed obvious different in dust and non-dust events.At the phylum level,the abundance of Campylobacter and Fusobacterium in Dust event 1 was high.At the genus level,the abundance of Delftia,Lactobacillus,and Helicobacter was high.At the phylum level,the abundance of Actinobacteria,Bacteroidota,and Cyanobacteria in dustevent 2 was high.At the genus level,the relative abundance of Bacillus and Chloroplast was relatively high.The transmission of local air mass of dust event 1 brought local bacteria related to human activities,while the long transmission of dust event 2 brought the dominant bacteria from desert areas.Different air mass had different impact on the composition and abundance of microorganisms in the atmosphere in the downstream area(Jinan).(4)There were significant differences between dominant and functional bacteria in soil and atmosphere.At the phylum level,Actinobacteria and Proteobacteria were the dominant bacteria in desert soil.Firmicutes and Proteobacteria were the dominant bacteria in the atmosphere.At the genus level,Arthrobacter was the dominant bacterium in desert soil,Chloroplast and Barnesiella were dominant bacteria in the desert atmosphere,Pseudomonas was the dominant atmospheric bacterium in Jinan.Physiological and ecotype functional analysis showed that the majority of microorganisms in sand samples were photosynthetic and chemotactic bacteria from soil,while the majority of airborne bacteria were parasitic or symbiotic bacteria from animals or plants,intestinal bacteria(mainly anaerobic bacteria),and saprophytic bacteria.Certain bacteria(Nocardoides and Microvigra)in desert soil had been detected in the air,indicating that microorganisms in soil can be dispersed into the desert atmosphere and may have potential impact on the airborne bacteria composition.For instance,Bacillus,Chloroplast bacteria can be transported over a long distance to the downstream,e.g.,Jinan,and further changing the bacterial community. |
