Physicochemical Characterization and Origin of the 20 March 2002 Heavy Dust Storm in Beijing

This study characterized the profiles of particles collected during a dust-storm (DS) period in Beijing on 19-21 March 2002, which was one of the heaviest episodes in the previous decade. Several determinations of particle measurements were observed, including total mass concentrations, particle size distributions, dry deposition flux, and chemical ions concentrations. The TSP concentrations reached an extremely high peak value of 12 mg/m^3 in DS period, and especially showed a characteristic increase in the size range of coarse particles (＞2.0 μm). The mass concentrations of coarse particles during DS period accounted for 91% of total particles, compared to 61% on non-DS days. The dry deposition mass flux of the dust storm reached 17.5 g/m^2-d on 20 March in Beijing. Additionally, the transported pathway of the pollutants was investigated by using backward trajectory analysis. The result of analysis indicated that the high level of dust sand originated from the arid regions of southern Mongolia, passing through central Inner Mongolia, Shanxi Province, and then to Beijing. Concentrations of Cl(superscript -), NO3(superscript -), and SO4(superscript 2-) in TSP were about 10 times higher in DS period than non-DS, probably because of some atmospheric processes enhancing chemical accumulation in the transported aerosols.