WANG Kai, ZHANG Xia, ZHANG Lin, SU Jin. Spatio-temporal distribution characteristics of PM2.5 and PM10 in metro stations in a city[J]. Journal of Environmental and Occupational Medicine, 2020, 37(9): 853-857. DOI: 10.13213/j.cnki.jeom.2020.20193
Citation: WANG Kai, ZHANG Xia, ZHANG Lin, SU Jin. Spatio-temporal distribution characteristics of PM2.5 and PM10 in metro stations in a city[J]. Journal of Environmental and Occupational Medicine, 2020, 37(9): 853-857. DOI: 10.13213/j.cnki.jeom.2020.20193

Spatio-temporal distribution characteristics of PM2.5 and PM10 in metro stations in a city

  • Background Accumulation of various pollutants in confined and crowded metro stations will deteriorate the air quality and affect passengers' health. Sanitary standards for metro carriages have not been established in China.
    Objective The study is designed to investigate the concentrations of PM2.5 and PM10 in metro stations, and to provide evidence for proposing sanitary control strategies and standard limits for the metro system.
    Methods PM2.5 and PM10 concentrations at underground platforms, in tunnels, and outdoors of 19 selected metro stations in a city were measured for continuously 4 h at the same time during 7:00-11:00 (including 2 h of morning rush and 2 h of non-rush) or 15:00-19:00 (including 2 h of evening rush and 2 h of non-rush) of any one workday in summer (August 2018), autumn (November 2018), and winter (January 2019). The height of monitoring points was 1.0-1.5 m from the floor. Continuous monitoring of the pollutants was conducted with a dust concentration detector which recorded one data point per 5 min, and an average concentration was calculated. The results were compared by different locations, seasons, operation hours, and concentration intervals; the 15min time-weighted concentration was calculated.
    Results The concentration of PM2.5 ranged from 25 to 275 μg·m-3 at underground platforms, and the median (P25, P75) concentration was 71 (54, 97) μg·m-3; while the concentration of PM10 at underground platforms ranged from 40 to 582 μg·m-3, and the median (P25, P75) concentration was 112 (87, 151) μg·m-3. The concentrations of PM2.5 and PM10 in tunnels were 1.42 times and 1.69 times higher than those outdoors, while the concentrations at underground platforms were 1.34 times and 1.58 times higher than those outdoors (P < 0.05). The concentration of PM2.5 at underground platforms in summer were 1.16 times and 1.03 times higher than those in autumn and winter, respectively (P < 0.05); the concentration of PM10 at underground platforms in summer were 1.20 times and 1.02 times higher than those in autumn and winter, respectively (P < 0.05). The concentrations of PM2.5 and PM10 in morning rush hours were the highest (P < 0.05), and the median (P25, P75) values were 84 (61, 114) μg·m-3 and 128 (98, 174) μg·m-3, respectively. As estimated by 15 min exposure, the PM2.5 and PM10 concentrations at underground platforms in morning rush hours were 8.0 μg·m-3 and 40.5 μg·m-3 higher than those outdoors at the same time. The concentration of PM2.5 at underground platforms was largely distributed from 0 to 100 μg·m-3, which accounted for 78.0% of total samples, while the concentration of PM10 was mainly distributed from 0 to 150 μg·m-3, which accounted for 74.7%. A strong correlation between PM2.5 and PM10 at underground platforms was observed (r=0.927, P < 0.001), and the PM2.5/PM10 ratio was 0.63.
    Conclusion The concentrations of PM2.5 and PM10 measured in selected metro stations are higher than those outdoors. PM2.5 and PM10 pollution in tunnels are most serious, which might be caused by the emissions from the metro train system and could adversely affect the platform environment.
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