Ground-based Observations of the Chemical Composition of Asian Outflow Aerosols

To improve our understandings of the characteristics and environmental impacts of the aerosols transported from the Asian Continent to the western North Pacific region, an aerosol observation network has been established on Taiwan and PengHu Islands since the spring of 2002. Aerosol sampling is conducted regularly in the last week of each month. Mass concentration, size distribution, and chemical composition of aerosol samples are measured with a resolution of 12 h. From the measurements of 2003–2005, it was found that the aerosol concentrations and compositions at rural and off-coast stations are rather consistent with each other in the winter monsoon periods. Furthermore they are much higher than those of remote areas, apparently due to long-range transport of air pollutants and dust from the Asian Continent. This is supported by the high percentages of sulfate, ammonium ions and organic carbon which are mostly from anthropogenic sources. It was also found that the Asian outflow aerosols were transformed chemically as they mixing with air pollutants originating from Taiwan. This finding indicates that the Asian outflow aerosols can be important carriers of reactive gases, particularly nitric acid and ammonia, from Taiwan to the downwind areas of the Asian winter monsoons.