A model for simulating PM2.5 concentration in subway systems

Due to adverse effects on health, the PM2.5 of subway systems is increasingly attracting people's attention. Although scholars have conducted many experimental studies on the characteristics of PM2.5 in subway stations, theoretical research on the propagation law of PM2.5 in subway systems is still lacking. In this study, we established a mathematical model for the PM2.5 concentration in the subway system based on the principle of mass conservation, including a PM2.5 generation model for trains operating in tunnels and a network model for calculating the ventilation rate, to simulate the variation of PM2.5 concentration in various areas of the subway system. The model was used to simulate the PM2.5 concentration of a subway line in Nanjing, China and on-site testing was conducted to verify the simulation results, with an error was within 10%. The simulation results quantitatively illustrate the influence of train density and ambient concentrations on PM2.5 variation in the subway system and the comparison with studies in other countries has also verified the applicability. This model could be used based on actual subway lines to simulate the PM2.5 concentration at any time during subway operation, thereby providing effective guidance for improving the environmental air quality of subway stations and optimizing the design of environmental control systems.