Characteristics of PM2.5, CO2and particle-number concentration in mass transit railway carriages in Hong Kong.
Fine particulate matter (PM2.5) levels, carbon dioxide (CO2) levels and particle-number concentrations (PNC) were monitored in train carriages on seven routes of the mass transit railway in Hong Kong between March and May 2014, using real-time monitoring instruments. The 8-h average PM2.5levels in carriages on the seven routes ranged from 24.1 to 49.8 µg/m3, higher than levels in Finland and similar to those in New York, and in most cases exceeding the standard set by the World Health Organisation (25 µg/m3). The CO2concentration ranged from 714 to 1801 ppm on four of the routes, generally exceeding indoor air quality guidelines (1000 ppm over 8 h) and reaching levels as high as those in Beijing. PNC ranged from 1506 to 11,570 particles/cm3, lower than readings in Sydney and higher than readings in Taipei. Correlation analysis indicated that the number of passengers in a given carriage did not affect the PM2.5concentration or PNC in the carriage. However, a significant positive correlation (p < 0.001, R2= 0.834) was observed between passenger numbers and CO2levels, with each passenger contributing approximately 7.7-9.8 ppm of CO2. The real-time measurements of PM2.5and PNC varied considerably, rising when carriage doors opened on arrival at a station and when passengers inside the carriage were more active. This suggests that air pollutants outside the train and passenger movements may contribute to PM2.5levels and PNC. Assessment of the risk associated with PM2.5exposure revealed that children are most severely affected by PM2.5pollution, followed in order by juveniles, adults and the elderly. In addition, females were found to be more vulnerable to PM2.5pollution than males (p < 0.001), and different subway lines were associated with different levels of risk.
Department of Science and Environmental Studies, The Education University of Hong Kong, Tai Po, Hong Kong, China.
Hai-Long
HL
Zheng
Department of Science and Environmental Studies, The Education University of Hong Kong, Tai Po, Hong Kong, China. wdeng@ied.edu.hk.
Wen-Jing
WJ
Deng
School of Human Settlements and Civil Engineering, Xi'an Jiaotong University, Xi'an, China.
Yan
Y
Cheng
School of Human Settlements and Civil Engineering, Xi'an Jiaotong University, Xi'an, China.
Wei
W
Guo
D002245:Carbon Dioxide / Q000032:analysis*; D004784:Environmental Monitoring / Q000379:methods; D006723:Hong Kong; D006801:Humans; D010316:Particle Size; D052638:Particulate Matter / Q000032:analysis*; D011156:Population Density; D011890:Railroads; D012016:Reference Values
D052638:Particulate Matter; D002245:Carbon Dioxide
CO2; Hong Kong; Mass transit railway (MTR); PM2.5; Particle-number concentration (PNC)