Characteristics of Visibility Impairment by Semi-Continuous Optical and Chemical Property Monitoring of Aerosols in Seoul

The characteristics of aerosol light extinction were investigated by comparing measured and calculated extinction coefficient to understand the contribution of air pollutants on visibility impairment for data during 4 months (Jan similar to April), 2014. The integrated nephelometer and aethalometer system were installed to measure the scattering and absorption coefficients of aerosol as well as BAM 1020, MARGA, semi- continuous OCEC analyzer, and online- XRF to calculate the extinction coefficient. The IMPROVE_ 2005 equation was used to determine the contributions of different chemical components on visibility impairment in PM2.5 and PM10 due to highest correlation with measured data. Sulfate, nitrate, and organic mass by carbon (OMC) of fine aerosol were the major contributors affecting on visibility impairment. Total contributions to light extinction were calculated as 631.0 Mm(-1) for the worst- case and 64.4 Mm(-1) for the best- case. The concentrations of aerosol component for the worst- case were 38.4 times and 45.5 times larger than those of the best- case for (NH4) 2SO(4) and NH4NO3, respectively. At lower visibility condition, in which extinction coefficient was higher than 400 Mm(-1), extinction coefficient varied according to the relative humidity variation regardless of PM2.5.