초록 열기/닫기 버튼
Daily PM2.5 was collected during summer period in 2020 in Gwangju to investigate its chemical and light absorption properties. In addition, real-time light absorption coefficients were observed using a dual-spot 7-wavelength aethalometer. During the study period, SO42- was the most important contributor to PM2.5, accounting for on average 33% (10-64%) of PM2.5. The chemical form of SO42- was appeared to be combination of 70% (NH4)2SO4 and 30% NH4HSO4. Concentration-weighted trajectory (CWT) analysis indicated that SO42- particles were dominated by local pollution, rather than regional transport from China. A combination of aethalometer-based and water-extracted brown carbon (BrC) absorption indicated that light absorption of BrC due to aerosol particles was 1.6 times higher than that due to water-soluble BrC, but the opposite result was found in absorption Ångström exponent (AAE) values. Lower AAE value by aerosol BrC particles was due to the light absorption of aerosol BrC by both water-soluble and insoluble organic aerosols. The BrC light absorption was also influenced by both primary sources (e.g., traffic and biomass burning emissions) and secondary organic aerosol formation. Finally the ATR-FTIR analysis confirmed the presence of NH4+, C-H groups, SO42-, and HSO42-. The presence of HSO42- supports the result of the estimated composition ratio of inorganic sulfate ((NH4)2SO4) and bisulfate (NH4HSO4).
