Abstract
Aerial observations of atmospheric pollutants over the main land China and ground-based observations of long-range trans-boundary pollutants at a newly built observation site, CHAAMS (Cape Hedo Atmosphere and Aerosol Monitoring Station) were reviewed. Aerosols collected over the main land China were usually well neutralized contrary to our expectation. Sulfate exceeded ammonium in the western part but ammonium exceeded sulfate in the eastern part. It was speculated that the emission of ammonia gas in eastern China is much larger than SO2 emission. Nitrate in aerosols was mainly contained in coarse particles at Cape Hedo, Okinawa. It was quite different from the situation observed in China, where most of nitrate was contained in fine particles. The most important reason for this is thermal instability of ammonium nitrate during the long-range transport. Ammonium nitrate formed in China as fine particles decomposed again to ammonia gas and nitric acid gas. Then, nitric acid gas must have deposited onto coarse particles such as sea salts and/or dust particles.
