The elemental and organic characteristics of PM2.5 in Asian dust episodes in Qingdao, China, 2002

Eighteen PM2.5 samples that included three episodes were collected in Qingdao, China in spring 2002. Simultaneous total suspended particulate samples were also collected during two of the episodes for comparisons. Meteorological data along the back trajectories suggested that two of the episodes may have been the consequence of Asian dust storms. The chemical characteristics of selected elements and solvent-extractable organic compounds (SEOC) were determined to identify the origin of these materials. The elements Fe, Mg, Ca, Al, Ti, Mn and V in the dust samples were found to be of crustal origin and were transported to Qingdao from outside the area, while Pb and Zn were attributed to local (regional) emissions. Small variations in the distribution patterns and compositions were observed in the SEOC from the PM2.5 samples collected during the two dust episodes although there was a significant increase in total loading. The results suggest that the dust episodic aerosols possess strong local characteristics superimposed with a heavy crustal and possibly pollution influx transported with the dust particles during the storms. Because the sources of the aerosols were different, high pollutant concentrations were observed at Qingdao in two waves: the locally emitted aerosols such as vehicular exhaust rose first before the long-distance transported materials arrived and the locally emitted pollutants tended to stay in the atmosphere for a longer time. (C) 2003 Elsevier Ltd. All rights reserved.