PM_2.5 Concentration Distribution In Indoor Environment And Numerical Simulation Study

Fine particulate matter(PM_2.5)is a kind of pollutant existing in urban environment.PM_2.5has great harm to human health.With the continuous increase of urban population,and most of the time urban residents spend in the indoor environment,the indoor environment has a direct impact on the human body.The results show that the inflow of outdoor PM_2.5,together with the internal sources?such as indoor combustion and particle resuspension?,can cause the I/O ratio to be higher than 1 and the indoor air quality to be lower than outdoor.In the outdoor environment,the biggest impact on urban PM_2.5is traffic and combustion,and the collection mode of PM_2.5is precipitation and wind.No matter outdoor or indoor environment,short-term or long-term exposure to PM_2.5will lead to respiratory and cardiovascular diseases,pose a threat to human health,and bring economic burden to society.Who sets annual and short-term exposure limits?10 and 25?g/m³,respectively?to reduce the impact of continuous exposure to PM_2.5.This paper has a thorough understanding of the source of PM_2.5and the interaction between residential buildings and the surrounding environment.This paper describes the impact of PM_2.5on human body in indoor environment,the main sources of PM_2.5in outdoor and indoor urban environment,the currently applicable PM_2.5exposure limit in the world,the impact of PM_2.5on social economy,and how to reduce the concentration of PM_2.5in indoor environment,and how to reduce the contact with PM_2.5.In order to determine the indoor and external sources that affect the indoor PM_2.5of 32 residential buildings in Zhuzhou City,this paper collected indoor PM_2.5samples in three seasons?autumn,winter and spring?from 2018 to 2019.At the same time,outdoor PM_2.5samples are collected at the central monitoring point 4974 meters?1065-11592 meters?away from the residential building every day.The results show that indoor PM_2.5concentration?5.2?g/m³on average?is lower than outdoor PM_2.5concentration?6.5?g/m³on average?,which is in a lower range compared with other indoor PM_2.5research results.The usepa-pmf model is applied to the simultaneous measurement of PM_2.5components inside and outside the house,and the distribution of pollution sources is estimated.The main sources of indoor PM_2.5were secondary pollution?41%?and motor vehicles?17%?,followed by calcium rich particles?12%?,biomass combustion?15%?,soil dust?6%?and aerosol?4%?.Similarly,the main sources of outdoor PM2.5 in four seasons were secondary pollution?41%?and motor vehicles?26%?,followed by biomass combustion?17%?,soil dust?7%?,road dust?3%?and aerosol?1%?.In the three seasons,the contribution of secondary pollution to indoor and outdoor PM_2.5is the largest,and in spring,the contribution rate of indoor PM_2.5is 53%,and that of outdoor PM_2.5is 45%.In autumn and winter,the contribution of this source is low,which is likely due to less indoor infiltration.In contrast,the indoor contribution of vehicle sources was the highest in autumn?29%?and winter?25%?.At the same time,according to the relationship between indoor and outdoor sulfur ratio and the contribution of each source,the influence of local and regional factors on indoor PM_2.5concentration was estimated.In order to study the distribution of PM_2.5in the indoor air,the paper established the indoor air PM_2.5distribution model,and used CFD to simulate the indoor PM_2.5distribution under the conditions of natural ventilation and air conditioning ventilation.The influence of different ventilation modes on indoor PM_2.5distribution was analyzed.The results show that PM_2.5is mainly concentrated near the entrance,exit and wall.The distribution of PM_2.5is directly affected by ventilation mode.The concentration of PM_2.5in natural ventilation is lower than that in air conditioning ventilation.