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Almost five million citizens a day are using subways as a means of traffic communication in the Seoul metropolitan. As the subway system is typically a closed environment, indoor air pollution problems frequently occurs and passengers complain of mal-health impact. Especially PM 10 is well known as one of the major pollutants in subway indoor environments. The purpose of this study was to compare the indoor air quality in terms of PM 10 and to quantitatively compare its source contributions in a Seoul subway platform before and after installing platform screen doors (PSD).PM 10 samples were collected on the J station platform of Subway Line 7 in Seoul metropolitan area from Jun. 12, 2008 to Jan. 12, 2009. The samples collected on membrane filters using PM 10 mini-volume portable samplers were then analyzed for trace metals and soluble ions. A total of 18 chemical species (Ba, Mn, Cr, Cd, Si, Fe, Ni, Al, Cu, Pb, Ti, Na-, and SO 4 2-) were analyzed by using an ICP-AES and an IC after performing proper pre-treatments of each sample filter. Based on the chemical information, positive matrix factorization (PMF) model was applied to identify the source of particulate matters. PM 10 for the station was characterized by three sources such as ferrous related source, soil and road dust related source, and fine secondary aerosol source. After installing PSD, the average PM 10 concentration was decreased by 20.5% during the study periods. Especially the contribution of the ferrous related source emitted during train service in a tunnel route was decreased from 59.1%

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Seoul subway plays an important part for the public transportation service in Seoul metropolitan area. As the subway system is typically a closed environment, frequent air pollution problems occurred and passengers get malhealth impact. Especially particulate matters (PM) is well known as one of the major pollutants in subway environments. The purpose of this study was to compare the concentrations of PM 10 and PM 2.5 in the Seoul subway system and to provide fundamental data in order to management of subway system. PM 10 and PM 2.5 samples were collected in the M station platform and tunnel of Subway Line 4 in Seoul metropolitan and in an outdoor location close to it from Apr. 21, 2010~Oct. 27, 2013. The samples collected on teflon filters using PM 10 and PM 2.5 mini-volume portable samplers and PM sequential sampler. The PM contributions were 48.6 μg/m 3 (outdoor), 84.6 μg/m 3 (platform) and 204.8 μg/m 3 (tunnel) for PM 10 , and 34.6 μg/m 3 (outdoor), 49.7 μg/m 3 (platform) and 83.1 μg/m 3 (tunnel) for PM 2.5 . The PM 10 levels inside stations and outdoors are poorly correlated, indicating that PM 10 levels in the metro system are mainly influenced by internal sources. In this study, we compared PM concentrations before and after operation of ventilation and Electrostatic Precipitator (EP). Despite the increased PM concentration at outdoor, PM 10 concentration at platform and tunnel showed the 31.2% and 32.3% reduction efficiency after operation the reduction system. The overall results of this study suggest that the installation and operation of the ventilating system and EP should have served as one of the important components for maintaining the air quality in the subway system.

Air quality in a subway tunnel has been crucial in most of the subway environments where IAQ could be affected by many factors such as the number of passengers, the amount and types of ventilation, train operation factors and other facilities. A modeling approach has been introduced to manage the general IAQ in a subway station. Field surveys and CO 2 measurements were initially conducted to analyze and understand the relationship between indoor and outdoor air quality while considering internal pollution sources, such as passengers and subway trains, etc. The measurement data were then employed for the model development with other statistical information. For the model development, the algorithm of simple continuity was set up and applied to model the subway IAQ concerned, while considering the major air transport through staircases and tunnels. Monitored CO 2 concentration on the concourse and platform were correlated with modeling results where the correlation values for the concourse and platform were R 2 =0.96 and R 2 =0.75, respectively. It implies that the box modeling approach introduced in this study would be beneficial to predict and control the indoor air quality in subway environments.