Analysis of influencing factors of microbial aerosol concentration in centralized air conditioning and ventilation system of subway platforms
Objective To characterize the microbial aerosols in the centralized air conditioning and ventilation system of urban subway stations,and to explore the influencing factors of microbial aerosol concentration in the centralized air conditioning and ventilation system of subway stations in mega cities,and conduct analysis on fungal aerosol concentration and related influencing factors.Methods Applying random sampling strategy,this study selected 120 subway stations across 15 subway lines in a mega city.For each station,Andersen stage impactors were used to collect aerosol samples,covering 6 particle size segments(≥7.00 µm,4.70-＜7.00 µm,3.30-＜4.70 µm,2.10-＜3.30 µm,1.10-＜2.10 μm,0.65-＜1.10 µm).The concentration of bacterial and fungal aerosols was detected using culture method.Spearman rank correlation analysis,Mann Whitney U test,and Kruskal Wallis test were conducted to identify the potential influencing factors of microbial aerosol concentration.Results The median concentrations(interquartile range,IQR)of bacterial and fungal aerosols in the centralized air conditioning and ventilation system were 163(148)CFU/m3 and 346(205)CFU/m3,respectively.The results of the Spearman rank correlation analysis indicated that the correlation between different influencing factors and microbial aerosol concentration varied.For instance,we found a significant positive correlation of temperature with total bacteria aerosol concentration(r=0.22,P＜0.001)and total fungal aerosol concentration(r=0.17,P＜0.001).Inhalable particulate matter(PM10)mass concentration was significantly and positively correlated with total bacterial aerosol concentration(r=0.10,P＜0.05);however,its correlation with total fungal aerosol concentration was weak and did not reach statistical significance(r=0.06,P＞0.05).The results of Spearman rank correlation analysis showed that factors such as station type,platform opening year,season,and meteorological conditions might significantly affect the microbial aerosol concentration of the station's centralized air conditioning and ventilation system.Conclusions Temperature,relative humidity,PM10 mass concentration,cleaning interval,number of people passing through during sampling,station type,meteorological conditions may significantly affect the microbial aerosol concentration in the centralized air conditioning and ventilation system of subway stations.In the future,it is urgent to pay attention to these factors.Our findings may support the microbial risk prevention and control for subway stations.
MicroorganismsAerosolInfluencing factorsSubwayCentralized air conditioning and ventilation system
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