Particles Concentration in Air Masses from the Asian Continent: Comparison of Qingdao and Amakusa

In this study, the number concentrations of airborne particles in Asian dust plumes when they passed Qingdao (36.07 degrees N, 120.43 degrees E), a coastal city in East China, and Amakusa (32.19 degrees N, 129.59 degrees E), the western coast of Kyushu, Japan were compared. The number concentrations were continuously monitored at the two sites in spring 2010 by using two optical particle counters. Backward trajectory analysis was used to identify dust plumes which left the continent from Qingdao and passed Amakusa after one or two days. In total, four dust events were found to passed both Qingdao and Amakusa in spring 2010 and we used these four cases to investigate the evolution of number size distributions of particles in the plumes when they passed the two sites. Particles were separated into two groups according to size mode: fine mode particles of diameter<1.0 mu m and coarse mode particles of diameter >= 1.0 mu m. Results show that dust plumes and anthropogenic pollutants were isolated in Qingdao while to some extent mixed after passing the marine air between Qingdao and Amakusa. In addition, sea salt was suggested to be responsible for the increase of coarse mode particles in the dust plumes at Amakusa.