Single-particle characterization of aerosol samples collected before and during an Asian dust storm in Chuncheon, Korea

Low-Z particle electron probe X-ray microanalysis, a single-particle analysis method, was used to characterize aerosol samples collected in Chuncheon, Korea, before and during a dust storm that occurred between 10 and 12 March, 2004. Four different samples were analyzed: just before the storm, peak time of the storm, late stage of the storm, and end of the storm. All four of the samples were found to have experienced chemical modifications during long-range transport due to elevated levels of nitrate and sulfate that resulted from atmospheric reactions with CaCO3 and sea-salt particles. The sample collected just before the storm underwent the most extensive chemical modification during transport. For this particular sample, the overall relative abundances of reacted CaCO3 and sea-salt particles were 9.8% and 44.2%, respectively. The sample collected at the peak time of the storm also experienced extensive chemical modification with overall relative abundances of reacted CaCO3 and sea-salt particles at 4.3% and 23.3%, respectively. The backward trajectory analysis for this particular sample revealed two different types of air-masses arriving at the sampling site in Korea; one is high-altitude air-masses moving rapidly and carrying Asian dust particles and the other a slow-moving low-altitude air-mass from eastern China coastal areas. The single-particle characterization of this same sample showed that the Asian dust particles were mixed with sea-salts entrained over the Yellow Sea, as well as air pollutants from the eastern China coastal areas. However, as the Asian dust storm continued, soil-derived mineral particles became dominant in the samples that were collected at the late stage of the storm and at the end. For this specific Asian dust storm, the mixing of sea-salts and pollution with Asian dust particles was observed to occur just at the early stage of the storm.