Characteristics and source identification of fine particles in the Nanchang subway, China

Abstract

To investigate the pollution level and sources, atmospheric fine particles (PM2.5) were collected in five stations of the Nanchang subway in central China throughout 2019. PM2.5 was highly variable across sampling sites, subway stations and seasons. The mean (±standard deviation) concentration of PM2.5 was 178.92 ± 47.69 μg/m3 in the carriage, 95.97 ± 22.94 μg/m3 in the ticket counter, 122.43 ± 21.77 μg/m3 in the platform, and 175.89 ± 30.43 μg/m3 in the above-ground entrance. PM2.5 contamination was higher in the October holidays, followed by January, May, November, and June. Overall the highest PM2.5 level occurred in station D, followed by stations B, E, A, and C. The analysis indicated that the PM2.5 consists of 23.7% inorganic species, 29.6% ions, 11.8% carbon compounds, and 34.9% other materials. The most abundant element in the PM2.5 was Fe at a concentration range from 5.3 ± 5.04 μg/m3 to 14.97 ± 12.96 μg/m3 among sampling sites. Other common elements found were Pb, Mn, Co and Cu. Among anions and carbon compounds, NO3− showed the highest concentration with 19.14 ± 23.29 μg/m3, followed by SO42−, OC, Cl−, and EC. Source apportionment by Positive Matrix Factorization (PMF) identified six sources for the studied species: wheel/rail system (29.90%), brake and catenary (4.30%), vehicle traffic (25.40%), coal combustion (19.70%), secondary sources (13.20%), and industrial emissions (7.50%). To reduce PM2.5 contamination, source control and mitigation measures should be considered in the Nanchang subway.