Impact of Subway Platform Screen Door Opening and Closing on Particulate Matter Concentration Distribution at Different Locations and Times: The Case of Xi’an

To explore how the opening and closing of subway platform screen doors (PSD) affect particulate matter concentrations (PM10, PM2.5, and PM1.0) across different times (morning peak, off-peak, evening peak), and three key locations (subway tunnels, platforms, and waiting areas), we studied the Xi’an subway using a systematic monitoring approach, and a total of 6 monitoring points were monitored at 3 locations for 60 consecutive days of testing. The sampling time for each measurement point was 20 min, and a total of three groups were tested. The relationship between the opening/closing status of PSD and changes in particulate matter concentrations was then analyzed using statistical methods. The results showed that the particulate matter concentrations followed a sequential pattern: tunnel concentrations were higher than those in the waiting area, which in turn were higher than those at the platform center. PM10 concentrations exceeded China’s standards for indoor air quality (GB/T 18883-2022) at all three locations. For PM2.5, concentrations in the tunnel and waiting area exceeded the standard, while those at the platform center remained within the limit. Particles smaller than 1.0 μm constituted the dominant fraction of particulate matter in the tunnel, waiting area, and platform center. After the PSD opened, the peak average concentrations of PM10, PM2.5, and PM1.0 in the waiting area increased by 70.53%, 55.81%, and 42.41%, respectively, compared to the average concentrations before the train entered the station. PSD had a significant impact on fine particulate matter concentrations on the platform during the evening peak: PM10 concentrations in the front and rear of the waiting area were 37.85% and 57.61% higher than those in the middle, while PM2.5 concentrations in these two areas were 39.81% and 50.23% higher than in the middle. No obvious distribution pattern was observed for PM1.0. These results provide reference data for optimizing indoor air quality in the Xi’an subway and regulating the operation of platform screen doors.