Seasonal ion characteristics of fine and coarse particles from an urban residential area in a typical industrial city

This study investigated seasonal ion variation and correlation characteristics in size-fractionated particles collected for four seasons using an eight-stage cascade impactor sampler from an urban residential area in the largest industrial city, Korea. The identified ionic species accounted for 47.4, 52.5, 35.8, and 44.5% of PM1.1, PM2.1, PM10 − 2.1, and PM10 (PM2.1 + PM10 − 2.1), respectively. Sulfate (SO42 −) was the most abundant species and had the highest relative concentrations of both fine and coarse particles in summer. However, nitrate (NO3−) and ammonium (NH4+) showed the highest fractions in fine particle mass concentration in winter. NH4+ showed the highest mass fraction in coarse particles in spring. The highest ratio of NO3/SO42 − in fine particle in winter was due to the decreased sulfate and increased nitrate formation by low winter temperature. Most ions, such as SO42 −, NH4+, K+, Cl− and NO3−, accumulate in fine particles (PM2.1); while the concentrations of Na+, Ca2 + and Mg2 + were greater in the coarse particles (PM10 − 2.1). In the cluster analyses of the ion components, road and soil dust, secondary aerosols and sea salt were shown to be possible major airborne PM sources in residential areas of the industrial city.

► This study investigated seasonal size distribution of ionic species in fine and coarse particles. ► Sulfate peaked in summer with regard to both fine and coarse particles. ► Nitrate and ammonium peaked in winter for fine particles and in spring for coarse particles.