Characteristics of dust particles from the desert/Gobi area of northwestern China during dust-storm periods

The total suspended particle (TSP) samples were collected from seven urban cities in Gansu province in the periods of dust storms from January to April 2001. These dust events were characterized by about 1-3 days duration, NNW-, NW-, WNW-dominant wind directions, ~15.0 m/s 1-h average wind speeds and ~62.53 mg/m³ TSP levels. In the January-April period, the dust events in northwestern China were mainly induced by the high pressures over Xinjiang or over northwestern Mongolia and by depressions over eastern Asia. TSP samples were analyzed using a JSM-5600LV scanning electron microscope (SEM) equipped with a KEVEX EDX and inductively coupled plasma atomic emission spectrometry for examining morphologies and major components. In addition, soil samples, collected from 11different sites, were analyzed using X-ray fluorescence for their chemical components. The morphology of the dust particles showed a wide variety of types such as spherical shapes, irregular and sharp-edged shapes, etc., and contained crustal element oxides such as SiO₂, Al₂O₃, Fe₂O₃, CaO, MgO, K₂O, Na₂O, and TiO₂, similar to the chemical components in the desert/Gobi areas. However, the concentrations of elements such as Cu, V, Pb, Zn and As were wider and higher than those in the soils of the desert/Gobi areas, and their ratios for TSP/desert and TSP/Gobi were about 3~14. The levels of these elements in the urban cities may not be influenced by the dust storms in the desert/Gobi areas, but may be contributed to by anthropogenic sources such as industrial tailings and some polluted materials.