Recent Results of Individual Asian Dust Particle Analysis Daizhou Zhang Prefectural University of Kumamoto, Japan Yasunobu Iwasaka, et al. Nagoya University, Japan Guangyu Shi, et al. Institute of Atmospheric Physics, Chinese Academy of Science, China

Our observation sites

1. At the source region (Dunhuang) Results by balloon observation A dust layer at 3~5 km over the desert areas in summer 2002 when no dust events were reported or recorded. A similar layer was found in another balloon mission on March 24, 2003 (spring). The layer was confirmed by the onboard particle counter and LIDAR observations. Source was not identified and there isn’t further information about the layer except some LIDAR observation.

2. Over the Sea of Japan (Wakasa Bay) Results by aircraft observation A dust layer was found above 4 km over the Sea of Japan by two flight missions in July 2000 and July 2001 when no dust events were reported or recorded. The layer was confirmed by the onboard particle counter and LIDAR observations. The particles were likely from the arid areas of China and Mongolia. Does it mean the constant summer contribution of mineral to the ocean? Is this layer related to the layer observed at Dunhuang?

3. At a coastal site of China (Qingdao) Results by surface observation Anthropogenic mineral particles: In the pre-frontal air, high concentration of mineral particles were observed. Most of them contained anthropogenic pollutants such as sulfur. They were from East China. Asian dust particles: Mineral particles in the post-frontal air rarely contained pollutants such as sulfur. They were from the arid areas in West China and were the so-called Asian dust particles.

3. At a coastal site of China (Qingdao) Results by surface observation In the investigation of the chemical composition of Asian dust particles in the continental atmosphere, the pre- and post-frontal mineral particles should be considered separately. In particular, we must be careful when using results of the analysis of integrated filter samples.

4. At southwest Japan (Kumamoto) Results by surface observation ・ More than 60% of dust particles mixed with sea salt during their dispersion from China to Japan. Comparisons to results at Qingdao: ・ The distributions showed similar patterns with peaks around 3  m while the dominant particles were absolutely different.

4. At southwest Japan (Kumamoto) ・ Dust particle size increased due to the combination with sea salt. Where were the particles whose diameter became larger than 3  m?  Most of them must have been removed, otherwise the distributions should have shifted to larger ranges. Distributions segregated by the mixture levels of mineral and sea salt. ・ The distribution patterns were independent from mixture levels.

4. At southwest Japan (Kumamoto) Our suggestions for the interpretation of the distribution consistence of dust storm particles at different sites along the transport routes. The size distributions of dust storm particles observed at downstream areas should not be conserved by the original dust particles. They should be the results of growth of smaller particles and removal of larger particles.

5: At southwestern Japan (Kumamoto) on Cl loss from sea salt ・ Dust particles modify the chlorine chemistry in marine atmosphere through adsorbing HCl and restraint of HCl release from sea salt components in mixture particles. ・ Cl deposition onto dust particles is not ignorant compared to S deposition in marine atmosphere.

Summary: 1. There were dust layers in the free troposphere over East Asia in summer. 2. At the coastal area of China, Asian dust particles were in the post-frontal air and rarely contained anthropogenic pollutants. The pollutants were found on anthropogenic mineral particles in the pre-frontal air. 3. The size distributions of dust storm particles observed at downstream areas should be the results of growth of smaller particles and removal of larger particles. 4. Dust particles modify the chlorine chemistry in marine atmosphere through adsorbing HCl and restraint of HCl release from sea salt components in mixture particles.