Research On The Characteristics Of Microbial Pollution In Public Indoor Air Of Summer Campus

Due to the outbreak of the COVID-19,the research on the pollution characteristics of air microorganisms has become more and more important and urgent,which is of great significance to improve the air quality of the campus,prevent and control diseases,and establish the evaluation system of indoor air microbial pollution in the future.In this paper,through the six level air microbial sampler,the air microorganisms and particles in the three main functional areas of the classroom,dormitory and canteen in summer are sampled,cultivated and analyzed by high-throughput sequencing,so as to explore the temporal and spatial variation of indoor air microbial concentration in different functional areas of campus in summer,the distribution characteristics and enrichment of microorganisms on particles with different particle size ranges,and the composition and diversity characteristics of bacterial communities in each region.The results are as follows:In summer,the average concentration of total microorganisms in the air of each functional area of the campus is 1507.76±660.43 CFU/m~3in the canteen,1495.18±1002.23 CFU/m~3in the classroom and 566.84±312.17 CFU/m~3in the dormitory.The changes of total microbial concentrations in classrooms,dormitories and canteens were consistent in the three periods of early summer,midsummer and late summer.They all increased first and then decreased,and reached the maximum value in midsummer,which were 1845.13±1420.24 CFU/m~3,796.34±233.08 CFU/m~3,1564.51±622.18 CFU/m~3,respectively.The air microbial concentration in the classroom area during the class period is always lower than that in the unoccupied period.The results in dormitories and canteens are just the opposite of those in classrooms.The concentration of airborne microorganisms is usually higher in the period of personnel activity than in the period of no one.According to the air microbial evaluation standard developed by the ecological center of the Chinese Academy of Sciences,the indoor air quality of our school is in good condition in summer.In summer,indoor air microorganisms in campus are mainly distributed on particles with particle size of 1.1～3.3μm,accounting for 45%,56%and 61%of the total microorganisms in classrooms,dormitories and canteens respectively.Personnel activities in the classroom area basically did not affect the distribution of microorganisms on particles with different particle sizes.In the dormitory area,the air microorganisms are mainly distributed on the particles with particle size of 1.1～4.7μm in the unattended period,and the air microorganisms are mainly distributed on the particles with particle size of 1.1～3.3μm in the manned period.Microorganisms in the canteen area are always concentrated on particles with particle size of 1.1～3.3μm.In summer,the amount of microorganisms enriched in indoor air particles in different functional areas of campus,classroom>canteen>dormitory,the specific values are 3832.80 Piece/mg,2968.36 Piece/mg and 2292.58 Piece/mg respectively.The amount of microorganisms enriched by airborne particulate matter in the classroom area in the period of no man was much higher than that in the period of man,which were 5672.88 Piece/mg and 1992.71 Piece/mg respectively.The amount of airborne particulate matter enriched microorganisms in the dormitory and canteen area during the manned period is greater than that during the unmanned period.The number of airborne particulate matter enriched microorganisms in the dormitory area is 2883.36 Piece/mg and 1701.80 Piece/mg respectively,and that in the canteen area is 3575.55 Piece/mg and 2361.16 Piece/mg respectively.In summer,the 8 main species of indoor air microorganisms at the phylum level are Bacteroidetes、Firmicutes、Proteobacteria、Actinobacteria、Acidobacteria、Verrucomicrobia、Chloroflexi、Fusobacteria.The 10 major species at the genus level are Bacteroides、Lactobacillus、Bradyrhizobium、Escherichia-Shigella、Rhizobium-Neorhizobium-Pararhizobium-Rhizobium、Lachnospiraceae NK4A136group、Sphingomonas、Lachnospiraceae UCG-008、Streptococcus、Pseudomonas.The similarity of bacterial community composition in different periods in each functional area is canteen>classroom>dormitory.The alpha diversity of each region is canteen>dormitory>classroom.The diversity of three functional areas in different periods is manned period>unmanned period.