Physicochemical evolution of dust particles observed in March 2007, Seoul, Korea

From 26 March to 2 April 2007, two dust episodes were reported in Korea. One is 27-28 March and the other is 31 March-1 April which could be classified into weak and heavy Asian dust events, respectively, based on their PM10 intensities. To examine chemical and physical processes controlling compositions of Asian dust particles, PM10 aerosol samples were collected using PM10 cyclone with teflon filters on the roof of the sixth floor in the Asan science building located in Korea University. PM10 samples were analyzed for water soluble ions including 5 cation species and 3 anion species using ion chromatography. During the heavy Asian dust period, the mass concentration of PM10 reached the maximum value of 637.1 μg/m³ on 1 April 9-15h and the second maximum value of 412.0μg/m³ on 31 March 21h-1 April 9h, which can be classified into the relatively strong and the strongest dust storms, respectively. During the strongest dust storm, Ca²⁺ and Mg²⁺ showed a drastic increase of their levels up to 6.01 μg/m³ and 0.81 μg/m³, respectively, suggesting their role as soil dust tracers. In contrast, concentrations of Cl^-, K⁺ and Na⁺ were the highest, 4.59 μg/m³, 3.20 μg/m³ and 2.22 μg/m³ respectively, during the relatively strong dust storm. During the weak Asian dust period, PM10 mass concentration was 165.5 μg/m³ and elevated levels of SO₄^2-, NO₃^- and NH₄⁺ in PM10 were observed indicating the significant role of dust particles acting as an effective sink for acidic pollution gases. Detailed discussion including analyses of SEM/EDX, XRF and XRD will be presented in the meeting.