Abstract
Atmospheric particles were collected at two sites, Amami (28°31'N, 129°41'E) and Amakusa (32°21N, 129°59E), which are approximately at the same longitude and 420 km apart in southwestern Japan, on March 18, 2005, during an Asian dust event. The particles were individually analyzed with a scanning electron microscope. Elemental compositions of dust particles at the two sites were compared according to their contents of silicon (Si), aluminum (Al), iron (Fe), potassium (K) and calcium (Ca). Modifications of the particles by mixing with sea salt and aging processes relevant to sulfur chemistry were compared according to their contents of sodium (Na), chlorine (Cl) and sulfur (S). Among Amami's dust particles, Fe and K abundant ones were about 67% and 15%, respectively, while those among Amakusa's were 32% and 8%, indicating that the dust particles at Amami were more abundant in Fe and K than those at Amakusa. The average size of the analyzed particles was larger at Amakusa than at Amami. The particles were significantly changed by the coagulation with sea salt and by surface reactions, resulting in the frequent presence of Na, Cl and S. Weather and backward trajectory analyses revealed that air parcels carrying the particles to the two sites passed different dust source areas in the Asian continent and advectively approached the sites without mutual mixing. Therefore, even within the same dust event, particles at different locations might exhibit different properties due to their origins and experiences in the air.
