광주지역 PM 2.5 의 고농도 오염현상 조사

24-hr integrated PM 2.5 measurements were performed between December 2013 and October 2014 at an urban site in Gwangju and the collected samples were analyzed for organic carbon (OC), elemental carbon (EC), ionic species, and elemental species. Objectives of this study were to identify PM 2.5 pollution episodes, to characterize their chemical components, and to examine their probable origins. Over the course of the study period, average PM 2.5 concentration was 37.7±23.6 (6.0~ 121.5) μg/m³. Concentrations of secondary ionic species; NH₄+, NO₃-, and SO₄ 2- was on average 5.54 μg/m³ (0.28~ 20.86), 7.60 μg/m³ (0.45~ 33.53), and 9.05 μg/m³ (0.50~ 34.98), accounting for 13.7% (4.6~ 22.7), 18.6% (2.9~ 44.8), and 22.9% (4.9~ 55.1) of the PM 2.5 concentration, respectively. Average OC and EC concentrations were 5.22 μgC/m³ and 1.54 μgC/m³, taking possession of 4.6 and 22.2% (as organic mass) of the PM 2.5 , respectively. Frequencies at which 24-hr averaged PM 2.5 exceeded a 24-hr averaged Korean PM 2.5 standard of 50 μg/m³ (termed as an “episode” in this study) were 30, accounting for 21.3% of total 141 measurements. These pollution episodes were mostly associated with haze phenomenon and weak surface wind speed. It is suggested that secondary formation of aerosol was one important formation mechanism of the episodes. The episodes were associated with enhancements of organic mass, NO₃- and SO₄ 2- in winter, of NO₃- and SO₄ 2- in spring, and of SO₄ 2- in summer. Potential source contribution function results indicate also that PM 2.5 episodes were likely attributed to local and regional haze pollution transported from northeastern China in winter, to atmospheric processing of local emissions rather than long-range transport of air pollutants in spring, and to the SO₄ 2- driven by photochemistry of SO2 in summer.