Day-night variations and size distributions of water-soluble inorganic ions in atmospheric aerosols in Ulsan, Kore

Water-soluble inorganic ions (WSIIs) in 11 size-segregated aerosol particles (n=154) were collected in Ulsan during wintertime of 2019 to better understand the size distributions and their day-night variations. In order to quantify day-night variations, the coefficient of divergence (COD), which was a self-normalizing parameter, was presented. For the sampling period, the average total concentration of WSIIs in fine and coarse particles were 5.54 ?? 2.27 ??g/m3 and 1.30 ?? 0.58 ??g/m3 , constituting 22.3% and 6.53% of the different size particle mass, respectively. In this study, about 80% of the detected WSIIs were accumulated in fine particles. Ca2+, Na+ , and NO3??? were the dominant compositions in coarse mode, whereas SO4 2???, NO3???, and NH4+ (SNA) were the largest contributors to fine particles. In addition, the calculated CODs for individual WSIIs were not less than 0.30 exhibited significant difference between day- and nighttime, reflecting their different sources. The size distributions of NO3???, Cl???, Na+ , and K + exhibited bimodal types. Meanwhile, SO4 2???, F ???, Ca2+, Mg2+, and NH4+ were found to be single shapes. The peaks were generally observed at 0.18???0.56 ??m and 1.80???5.60 ??m in the fine and coarse particles, respectively. Comparisons of the quivalent concentrations of SNA suggested that in NH4+-rich samples with [NH4+]/[SO42???] > 2, the existing forms of secondary inorganic aerosols were probably (NH4)2SO4 andNH4NO3. Finally, the potential sources of individual WSIIs were also discussed