The distribution and influential factors of PM_(2.5) and CO_2 in urban rail carriages

摘要

The promotion of 'Green Transport' has increased the importance of urban rail transit in China. Increased passenger flow and longer travel time have led to increased attention to in-carriage air quality in trains. In this study, CO2 and PM2.5 monitoring were conducted in subway train carriages in a city in northern China. The study accounts for a variety of factors both inside and outside of the train carriages, such as passenger volume and exterior environment. The results reveal that good air quality outside of the train, an above ground location and the use of platform screen doors could aid in the attainment of acceptable PM2.5 concentrations. In addition, linear models of CO2 and PM2.5 concentrations were established based on passenger density. The nonlinear recursive models were constructed using time-series analysis to reflect the cumulative effects of the amounts of CO2 and PM2.5. The spatial and temporal distributions show that, given a constant passenger density, the PM2.5 concentration is higher near the door area than in the seating area. CO2 concentrations varied in three stages, consistent with the change of local passenger load. Finally, a real-time optimized control method for fresh air volume and some suggestions are proposed to improve the in-carriage air quality of subway trains.