PHYSICAL AND CHEMICAL PROPERTIES OF A WINTER-TIME YELLOW SAND EVENT IN NORTHEAST ASIA

The long range transport of mineral dust such as Yellow Sand (YS) is not restricted to the springtime periods in Northeast Asia. A YS phenomenon was observed during 25~27 January 1999, which was a remarkably distinctive episode in the occurrence time and intensity that had ever been observed in the wintertime in Korea.<BR> This YS event had a bi-modal temporal structure with the daily average concentrations of 210~349 ㎍m?³. The long-lasted second one followed the first arriving short and strong dust pulse. The dominant ion components were SO₄²?, NO₃?, Ca²? and Na? with the concentration of 11.3, 7.6, 6.1 and 4.2 ㎍ m?³, respectively during the passage of YS, compared to the corresponding concentrations of 4.1, 4.6, 0.4, and 1.2 ㎍ m?³ after the passage of YS (AYS) over Korea. The mode diameter of these compounds of YS was around 4 ㎛, compared to 0.4~0.9 ㎛ of AYS. Concentrations of SO₄²? and NO₃? were found to be highly correlated with that of Ca²? in the coarse mode during the YS event, whereas they were well correlated with NH₄? during the non-YS period.