| Popis: |
An intensive field campaign was conducted in a downwind area of the Asian continental outflow (Daejeon, Korea) during winter 2014 to characterize the spectral optical properties of severe haze and Asian dust episodes. High concentrations of PM10 (particulate matter with a diameter ≤ 10 µm) and light scattering coefficients at 550 nm, σs,550, were observed during a long-range transport (LRT) haze episode (PM10 = 163.9 ± 25.0 μg/m3; σs,550 = 503.4 ± 60.5 Mm−1) and Asian dust episode (PM10 = 211.3 ± 57.5 μg/m3; σs,550 = 560.9 ± 151 Mm−1). During the LRT haze episode, no significant change in the relative contribution of PM2.5 (particulate matter with a diameter ≤ 2.5 µm) chemical components was observed as particles accumulated under stagnant atmospheric conditions (January 13−17, 2014), suggesting that the increase in PM2.5 mass concentration was caused mainly by the accumulation of LRT pollutants. On the other hand, a gradual decrease in Ångström exponent (Å), gradual increase in single scattering albedo (ω) and mass scattering efficiency (MSE) were observed during the stagnant period, possibly due to an increase in particle size. During the Asian dust episode, a low PM2.5/PM10 ratio and Å(450/700) were observed with average values of 0.59 ± 0.06 and 1.08 ± 0.14, respectively, which were higher than those during the LRT haze episode (0.75 ± 0.06 and 1.39 ± 0.05, respectively), indicating that PM2.5/PM10 mass ratios and Å(450/700) can be used as tracers to distinguish aged LRT haze and Asian dust under the Asian continental outflow. |
