2018년 11월 광주 지역에서 발생한 미세먼지 고농도 사례 시 수용성 성분의 크기 분포 조사

Abstract

In this study, mass size distributions of ambient aerosol particles and their water-soluble organic and inorganic species were investigated under high pollution episode. To achieve the aim of this study, 24-hr integrated size-segregated aerosol samples were collected at an ubran site of Gwangju between November 02 and 16, 2018, and analyzed for mass, water-soluble organic carbon (WSOC), and ionic species. During study period, a high pollution episode of fine particulate matter (PM) occurred between November 02 and 07, possibly due to high pressure developed around Korean peninsula, extremely stable air conditions, and long-range transportation of aerosol particles from North Korea and northeastern China region. On November 02~03 when influence of local pollution dominated, ambient aerosol particles, WSOC, NO3-, SO₄2-, and NH4+ exhibited bi-modal size distributions with a condensation mode at a particle size of 0.32 μm and a droplet mode at a particle size of 1.0 μm in PM1.8. While, between November 05 and 07 when long-range transportation of PM was mixed with locally-produced pollution, they showed very pronounced droplet mode size distributions at 1.0 μm, without a condensation mode. NO3- concentration in PM1.8 during pollution episode increased significantly from 5.9 μg/m³ on November 02 to 21.5μg/m³ on November 06, while SO₄2- in PM1.8 increased from 1.6 to 5.8 μg/m³, indicating the dominance of local pollution during pollution episode. Furthermore, for WSOC, NO3-, SO₄2-, and NH4+, fraction of droplet mode size (PM0.55-1.8) to PM1.8 increased gradually as PM pollution got increased, while the condensation mode (PM0.17-0.32) contribution decreased. In addition, it was demonstrated that relative humidity could be an important factor promoting formation of droplet mode WSOC, NO3-, and SO₄2-.