Size Distribution of Airborne Particulate Matter and Associated Metallic Elements in an Urban Area of an Industrial City in Korea

This study analyzed the size distribution of airborne particulate matter (PM) and 13 metallic elements associated with it. PM samples were collected using an eight-stage cascade impactor in a busy urban area of an industrial city, Korea during four seasons. Most of the fine and coarse particle mass was concentrated in the size range of 0.7–1.1 μm and 9–10 μm, respectively. PM mass showed two peaks in spring: The first peak was observed for the smallest particles (< 0.7 μm) and the second one was found in the coarse particles (2.1–10 μm). However, fine particles (0.7–2.1 μm) showed the highest PM concentrations in winter. In the distribution analysis of 13 metals in PM, three main groups were determined: (i) heavy metals (Cd, Zn, Mn, Ni and Cr) which were present in high concentrations in fine particles (< 2.1 μm) particularly at the size of 0.4–0.7 μm, (ii) light metals (Na, Ca, K, Al) and Fe which had high concentrations in coarse particles, and (iii) other heavy metals (Pb, Mg and Cu) showing high concentrations at sizes larger than 5.8 μm. The concentrations of Cd, Mn and Ni in the size range of 0.4–0.7 μm of the airborne particles and their total levels obtained by summing up the concentrations of the 8 classified size groups were exceeded the proposed thresholds or tolerance levels of the toxic heavy metals. The mass concentrations of Cd, Mn and Ni decreased with increasing particle size, except the size range of 9–10 μm, in PM10. The levels of Pb in PM10 did not show the size characteristics shown in Cd, Mn and Ni and also was below its tolerance level. Principal sources of 13 metallic elements in PM included natural sources and local anthropogenic sources such as non-ferrous metal smelting, oil combustion, welding, vehicular traffic and road dust.