광주 지역에서 늦가을 황사 발생 시 대기 에어로졸 입자의 크기 분포 변화

The Korean peninsula was affected by dust storms (DSs) originated in an inner Mongolia region in China at the end of November, 2018. DS event occurred between November 28 and 30, 2018 in Gwangju. In this study, 24-hr integrated size-resolved ambient aerosols were measured from November 26 to December 01, 2018 at an urban site of Gwangju to explore the change in size distributions and chemical processes of ambient aerosol particles and their water-soluble ionic species before, during, and after DS event. Due to the long-range transport of air pollutants and meteorological conditions such as high pressure system developed around the Korean peninsula, air stagnation, and high relative humidity (RH), ambient aerosol particles and secondary ionic species before DS event exhibited tri-modal size distributions with a predominant droplet mode at a particle size of 1.0 μm and a moderate condensation mode at a particle size of 0.32 μm. While, on November 27~28 when DS event occurred along with long-range transport and local pollution, bi-modal size distributions were observed for ambient aerosols. In particular, secondary NO3-, SO₄2-, and NH4+ showed very outstanding droplet mode distributions at 1.0 μm. Moreover, existence of noticeable coarse mode during DS event was associated with increased NO3-, Ca2+, Mg2+, Na+, and Cl- concentrations. Coarse mode NO3- was likely produced through heterogeneous reaction of gaseous HNO₃ with CaCO₃ in dust particles. However, on November 28~29 when influence of local pollution dominated with low RH and favorable dispersion conditions, secondary NO3-, SO₄2-, and NH4+ in accumulation mode exhibited a condensation mode distribution at a particle size of 0.32 μm, without a droplet mode.