Identification of the sources of PM_(10) in a subway tunnel using positive matrix factorization

摘要

The level of particulate matter of less than 10 μm diameter (PM_(10)) at subway platforms can be significantly reduced by installing a platform screen-door system. However, both workers and passengers might be exposed to higher PM_(10) levels while the cars are within the tunnel because it is a more confined environment. This study determined the PM_(10) levels in a subway tunnel, and identified the sources ofPM_(10) using elemental analysis and receptor modeling. Forty-four PM_(10) samples were collected in the tunnel between the Gireum and Mia stations on Line 4 in metropolitan Seoul and analyzed using inductively coupled plasma-atomic emission spectrometry and ion chromatography. The major PM_(10) sources were identified using positive matrix factorization (PMF). The average PM_(10) concentration in the tunnels was 200.8 ± 22.μg/m~3. Elemental analysis indicated that the PM_(10) consisted of 40.4% inorganic species, 9.1% anions, 4.9% cations, and 45.6% other materials. Iron was the most abundant element, with an average concentration of 72.5 ± 10.4 μg/m~3. The PM_(10) sources characterized by PMF included rail, wheel, and brake wear (59.6%), soil combustion (17.0%), secondary aerosols (10.0%), electric cable wear (8.1%), and soil and road dust (5.4%). Internal sources comprising rail, wheel, brake, and electric cable wear made the greatest contribution to the PM_(10) (67.7%) in tunnel air. Implications: With installation of a platform screen door, PM_(10) levels in subway tunnels were higher than those on platforms. Tunnel PM_(10) levels exceeded 150 μg/m~3 of the Korean standard for subway platform. Elemental analysis of PM_(10) in a tunnel showed that Fe was the most abundant element. Five PM_(10) sources in tunnel were identified by positive matrix factorization. Railroad-related sources contributed 68% of PM_(10) in the subway tunnel.