Field measurement of PM25 concentrations in key areas of Nanning Metro station

 In this paper, the concentration of PM25 in the station hall, platform and interval tunnel of an underground station of Nanning Metro with platform screen door in the early stage of operation is continuously monitored for 6 months. The test results show that the number of days when the concentration of PM25 in the station hall, platform and tunnel does not meet the daily average of class Ⅱ concentration in the GB 3095-2012Ambient air quality standards accounts for 3%, 10% and 23%, respectively. The variation trend of PM25 concentration in the station hall, platform and tunnel has a strong positive correlation with the outdoor PM25 concentration. The effect of the outdoor air ratio on the concentration of PM25 in the station hall, platform and tunnel is not significant. The concentration levels of PM25 in the station hall, platform and tunnel are about 0.9, 11 and 15 times that of outdoor, respectively. The PM25 concentration in the tunnel is sensitive to the fluctuation of outdoor PM25 concentration, and when the outdoor concentration increases or decreases, the PM25 concentration in the tunnel will quickly show a greater increase or decrease. The passenger flow has a certain impact on the PM25 concentration in the station.