Trace element characterization and source identification of particulate matter of different sizes in Hanoi, Vietnam

Particulate matter (PM) with aerodynamic diameters of <1 mu m (PM1), 2.5 mu m (PM2.5), and 10 mu m (PM10) were investigated and analyzed for 15 trace elements in the center of Hanoi, Vietnam during April-September 2018. The mean concentrations were 40 +/- 11, 53 +/- 17, and 132 +/- 39 mu g/m3 for PM1, PM2.5, and PM10, respectively, indicating that PM pollution was severe in Hanoi. During the sampling period, the PM concentrations were little affected by local meteorological conditions. The severe PM pollution in Hanoi was significantly influenced by long-range atmo-spheric transport from northern and northeastern regions, with higher potential source areas for PM1. The total mean concentrations of 15 elements were 1417 +/- 141, 1624 +/- 159, and 2652 +/- 251 ng/m3 in PM1, PM2.5, and PM10, respectively, with Al, Zn, K, Cr, and Ni as the most abundant elements. The particle-size distribution of PM and elements showed a distinct peak in PM1. The metallurgy industry, coal combustion, traffic emission, biomass burning, and soil dust were identified as major contributors of elements in three-size PM. This study implies that PM1 pollution should gain more attention regarding its level and chemical composition.