Study On Indoor And Outdoor Microbiological Composition Characteristics And Propagation Law Of Atmospheric Fine Particulate Matter In Severe Cold Region

In recent years,with the rapid development of Chinese modernization process,regional outdoor poor air quality phenomenon frequently appears,especially in the northeast severe cold region of China,where due to industrial construction and seasonal heating mode,indoor and outdoor air pollution is more severe.Considering that microorganisms attached to atmospheric fine particles in indoor and outdoor air to propagate.Therefore,it is necessary to study on indoor and outdoor microbiological composition characteristics and propagation law of atmospheric fine particulate matter in severe cold region of Northeast China.In this study,the three typical cities?"Oil City"Daqing,industrial integrated city Harbin,and agricultural city Mudanjiang?in Heilongjiang Province of severe cold region,as northeast China during non-heating and heating season for offices,classrooms and residences,a total of three types of buildings indoor and outdoor atmospheric particulate matter pollutants were measured,and then analyzed the relationship between indoor and outdoor atmospheric particulate pollutants under different cities,seasons and building types,revealing the types of microorganisms and their proportion,and further researched on the environmental source of microbial colonies on it by BLAST?Basic Local Alignment Search Tool?.Based on the actual measurement of particulate pollutants in northeast severe cold region,it was clarified by CFD?Computational Fluid Dynamics?numerical simulation to study the propagation law of microbial aerosol particles under indoor and outdoor conditions.The results showed that there was a certain difference on the correlation content between indoor and outdoor PM_2.5.5 pollutants concentration of different building types in different cities during non-heating and heating season in Heilongjiang Province,Northeast China.As for office,average infiltration indexes of indoor and outdoor atmospheric PM_2.5during non-heating season in Daqing,Harbin and Mudanjiang were similar.During heating season,the average infiltration index of indoor and outdoor PM_2.5.5 in Daqing was the smallest?0.2886?and the largest in Mudanjiang?0.5992?;As for office,average infiltration index of indoor and outdoor PM_2.5.5 during non-heating season in Daqing was the largest?0.9320?and the smallest in Mudanjiang?0.8444?.Average infiltration index of indoor and outdoor PM_2.5was the largest in Harbin?0.6310?and the smallest in Mudanjiang?0.5692?;As for residence,average infiltration index of indoor and outdoor PM_2.5.5 in Daqing,Harbin and Mudanjiang during non-heating season were similar.Average infiltration index of indoor and outdoor PM_2.5.5 for urban residences in Harbin?0.5325?during heating season was lower than that of Mudanjiang?0.6918?.But on the whole,their average infiltration indexes were mostly concentrated between 0.5 and 0.9,which was mainly related to factors such as building envelope,personnel activity pattern and geographical location,etc.Under different seasonal conditions,there were four dominant bacterial phyla on indoor and outdoor PM_2.5.5 in"oil city"Daqing,industrial integrated city Harbin and agricultural city Mudanjiang for offices,classrooms and residences,among them which Proteobacteria and Firmicutes were at top2,also including Actinomycetes and Bacteroidetes,etc.However,the proportion of each bacterial phylum was different under different environmental conditions.The reason may be that the degree of correlation between indoor and outdoor fine particles concentration,intensity of ultraviolet rays,and temperature were different under different conditions.Through the BLAST source analysis technology,the environmental sources of bacteria on PM_2.5.5 pollutants were known.The main environmental sources of indoor and outdoor PM_2.5.5 bacteria for three building types in three cities under different seasonal conditions included soil,human,water,faeces,and rotten organic,etc.,but the proportion of environmental sources for microorganisms under different conditions varied to varying degrees.The abundance of microbial population during heating season was larger than that during non-heating season.No matter which city or building type during non-heating season or heating season,indoor bacterial microorganisms were more from human,and the corresponding outdoors was soil.The established bacterial aerosol growth and decay model was used as an unsteady-state pollution source combined with aerodynamic theory through computational fluid mechanic.It numerically simulated on the proliferation and diffusion law of bacteria on fine particles inside and outside the building?complex?.From the simulation results,it can be seen that:Through the simulation results of indoor propagation of pollutants,the ventilation can weaken or even block the movement of bacterial aerosol particles to surrounding to a certain extent.Taking the location of pollution source as a starting point,the concentration of pollutants gradually becomes smaller.It can be obtained from the simulation results of outdoor propagation of pollutants that the unsteady changes of pollution sources had a lagging effect on discrete phases in the flow field.And the closer to the location where the pollution source releases the pollutant,the higher the pollution risk.For the"?"shaped building complex,eddy currents of different sizes formed on the leeward side will lead to a higher concentration of pollutants at height of building enclosure and a larger gradient of change.The concentration of Pollutants would be greatly reduced and fluctuation range was small.