The contributions of long range transported aerosol in East Asia to carbonaceous aerosol and particulate matter (PM) concentrations in Seoul, Korea were estimated with potential source contribution function (PSCF) calculations. Carbonaceous aerosol (organic carbon (OC) and elemental carbon (EC)), PM_2.5, and PM₁₀ concentrations were measured from April 2007 to March 2008 in Seoul, Korea. The PSCF and concentration weighted trajectory (CWT) receptor models were used to identify the spatial source distributions of OC, EC, PM_2.5, and coarse particles. Heavily industrialized areas in Northeast China such as Harbin and Changchun and East China including the Pearl River Delta region, the Yangtze River Delta region, and the Beijing–Tianjin region were identified as high OC, EC and PM_2.5 source areas. The conditional PSCF analysis was introduced so as to distinguish the influence of aerosol transported from heavily polluted source areas on a receptor site from that transported from relatively clean areas. The source contributions estimated using the conditional PSCF analysis account for not only the aerosol concentrations of long range transported aerosols but also the number of transport days effective on the measurement site. Based on the proposed algorithm, the condition of airmass pathways was classified into two types: one condition where airmass passed over the source region (PS) and another condition where airmass did not pass over the source region (NPS). For most of the seasons during the measurement period, 249.5–366.2% higher OC, EC, PM_2.5, and coarse particle concentrations were observed at the measurement site under PS conditions than under NPS conditions. Seasonal variations in the concentrations of OC, EC, PM_2.5, and coarse particles under PS, NPS, and background aerosol conditions were quantified. The contributions of long range transported aerosols on the OC, EC, PM_2.5, and coarse particle concentrations during several Asian dust events were also estimated. We also investigated the performance of the PSCF results obtained from combining highly time resolved measurement data and backward trajectory calculations via comparison with those from data in low resolutions. Reduced tailing effects and the larger coverage over the area of interest were observed in the PSCF results obtained from using the highly time resolved data and trajectories.

In order to investigate the optical properties of atmospheric aerosol in the urban area of Beijing, in situ and remote measurements of particulate pollutants were conducted at an urban site (39.98°N, 116.35°E, ∼20 m above ground level) in Beijing during the Campaign of Air Quality Research in Beijing (CAREBeijing) campaign from 16 August to 10 September 2006. During the intensive measurement period, average PM_2.5 mass concentration and light extinction coefficient (b_ext) were measured to be 102.1 ± 55.0 μg m⁻³ and 880.7 ± 685.9 Mm⁻¹, respectively. Average mass scattering efficiency of PM₁₀ and PM_2.5 particle were found to be 2.5 ± 1.1 and 3.4 ± 1.2 m² g⁻¹, respectively. Average single scattering albedo (SSA) of dry PM₁₀ was characterized to be 0.82 ± 0.09. It was found that SSA decreased to lower values of ∼0.75 during the relatively clean condition while it increased up to ∼0.86 during polluted condition mainly owing to the increases of ammonium sulfate, ammonium nitrate, and organic mass by carbon's contributions to PM mass concentrations. Pollution episodes in Beijing were strongly related to wind speed and wind direction. Stagnant weather conditions with southerly wind and low wind speed accelerated the accumulation of the pollutants in Beijing, which led to severe haze. It has been found that high PM_2.5/AOT (aerosol optical thickness) ratio of 228.2 μg m⁻³ was observed when air mass was transported from western or northern China while significantly lower PM_2.5/AOT of 107.6 μg m⁻³ was observed when it was affected mostly by local air pollutants in Beijing.