Chemical compositions of subway particles in Seoul, Korea determined by a quantitative single particle analysis.
A novel single particle analytical technique, low-Z particle electron probe X-ray microanalysis, was applied to characterize seasonal subway samples collected at a subway station in Seoul, Korea. For all 8 samples collected twice in each season, 4 major types of subway particles, based on their chemical compositions, are significantly encountered: Fe-containing; soil-derived; carbonaceous; and secondary nitrate and/or sulfate particles. Fe-containing particles are generated indoors from wear processes at rail-wheel-brake interfaces while the others may be introduced mostly from the outdoor urban atmosphere. Fe-containing particles are the most frequently encountered with relative abundances in the range of 61-79%. In this study, it is shown that Fe-containing subway particles almost always exist either as partially or fully oxidized forms in underground subway microenvironments. Their relative abundances of Fe-containing particles increase as particle sizes decrease. Relative abundances of Fe-containing particles are higher in morning samples than in afternoon samples because of heavier train traffic in the morning. In the summertime samples, Fe-containing particles are the most abundantly encountered, whereas soil-derived and nitrate/sulfate particles are the least encountered, indicating the air-exchange between indoor and outdoor environments is limited in the summer, owing to the air-conditioning in the subway system. In our work, it was observed that the relative abundances of the particles of outdoor origin vary somewhat among seasonal samples to a lesser degree, reflecting that indoor emission sources predominate.
Kang
Sunni
S
Department of Chemistry, Inha University, 253, Yonghyun-dong, Nam-gu, Incheon 402-751, Korea.
Hwang
HeeJin
H
Park
YooMyung
Y
Kim
HyeKyoung
H
Ro
Chul-Un
CU
D000393:Air Pollutants / Q000737:chemistry*; D004577:Electron Probe Microanalysis / Q000379:methods*; D007501:Iron / Q000737:chemistry; D007723:Korea; D052638:Particulate Matter / Q000737:chemistry*; D011890:Railroads
D000393:Air Pollutants; D052638:Particulate Matter; D007501:Iron