Abstract
In order to elucidate the variation and characterization of dust particles that originate in the arid and semi-arid regions of inland Asia and are transported to Japan, we established a sampling network system in east China and Japan and collected aeolian dust under the Japan-China joint project “ADEC”. Monitoring of the total suspended particle (TSP) and size-segregated dust concentrations were carried out in Beijing, Qingdao and Hefei in China, and Fukuoka, Nagoya, Tsukuba and Naha in Japan. The seasonal variations showed the general trend that the aerosol concentration was high in spring and low in summer, though it sometimes became high in winter in Qingdao. The aerosol size distribution was bimodal. One peak at around 0.5 μm diameter corresponds to panicles of anthropogenic origin, in which the main components are black carbon, NH4+ and SO42−, and some elements such as Pb, Cd, Sn, Sb and Bi are abundant. The other peak at around 4-5 μm diameter corresponds to mineral dust of soil origin, in which the main soluble components are Na+, Ca2+, NO3− and Cl−. The coarser particles increased when a dust event occurred. The IOP program was conducted in the spring of 2002 (IOP-1) and 2003 (IOP-2). The dust concentration during IOP-1 was high in China, particularly in Beijing. The average dust concentration during a dust event decreased in the order of Beijing > Qingdao > Hefei and Beijing > Fukuoka > Nagoya > Tsukuba > Naha. However, there were few observable dust events during IOP-2. From the results of continuous monitoring, the dust concentration during periods without dust events seemed to be almost equal at all monitoring locations in Japan. This suggests that the segregation of dust occurs in China and fine dust particles are transported to Japan. Seasonal variations of TSP, PM11 (paniculate size is less than 11 μm), PM2.1 (less than 2.1 μm) and mineral matter (larger than 2.1 μm) contents were studied. It was shown that these values decrease with distance from the source area.
