中文摘要：

目的在不同浓度大气PM_（2.5）水平下,比较不同出行方式的PM_（2.5）个体暴露水平,并进一步比较地铁站不同位置的PM_（2.5）浓度,以期为城市居民选择适宜的出行方式提供科学依据。方法于2015年12月30日至2016年1月4日,选择北京市城区的某条路线作为研究地点,使用便携式PM_（2.5）监测仪同时测量步行、乘坐公交车和地铁3种出行方式的PM_（2.5）个体暴露水平;对地铁站台、安检处和地铁车厢内的PM_（2.5）浓度进行同步监测并比较。结果在同一研究时期,步行、乘坐公交车和地铁测得的PM_（2.5）个体暴露浓度均值分别为219.34、209.61、167.56μg/m3。当大气PM_（2.5）浓度较低时（≤60μg/m3）,乘坐地铁的PM_（2.5）个体暴露水平高于步行和乘坐公交车;当大气PM_（2.5）浓度较高时（〉100μg/m3）,乘坐地铁的个体PM_（2.5）暴露水平明显低于步行和公交车,差异均有统计学意义（P〈0.05）。监测期间地铁站台、安检处和车厢内的PM_（2.5）浓度均值分别为196.90、170.20、136.82μg/m3。结论在不同的大气PM_（2.5）污染水平下,不同出行方式的人群PM_（2.5）个体暴露水平不同。

英文摘要：

Objective To compare personal exposure to air particulate matter（PM_（2.5）） by three commuting modes under different levels of ambient PM_（2.5）. Furthermore, PM_（2.5）concentrations at three places in subway station were compared. Methods A route at urban area in Beijing was chosen. Personal PM_（2.5）exposures by three commuting modes including walking, bus and subway were measured at the same time by using portable PM_（2.5）monitors, between December 30, 2015 and January 4, 2016. PM_（2.5）concentrations at three places in subway station, including security checkpoint, platform and subway car were measured and compared. Results During the same study period, means of personal PM_（2.5）exposures were 219.34 μg/m3, 209.61 μg/m3and167.56 μg/m3 for walking, bus and subway respectively. Further comparison showed that subway commuter had higher exposure compared with walker and bus commuter under low ambient PM_（2.5）concentration（≤60 μg/m3）; While subway commuter had the lowest exposure under high ambient PM_（2.5）concentration（〉100 μg/m3）. During the study period, means of PM_（2.5）concentrations were 196.90 μg/m3, 170.20 μg/m3, 136.82 μg/m3 at platform, security checkpoint and subway car respectively. Conclusion Commuters using three transport modes have different personal PM_（2.5）exposure under different ambient PM_（2.5）concentrations.These results will be helpful for citizens to choose commuting mode scientifically.