2016 Volume 51 Issue 5 Pages 218-229
The chemical composition of the Asian mineral dusts (kosa aerosols) will reflect the mineral composition of the surface soil from which they originate, as well as any subsequent reactions with anthropogenic material occurring during transport. This study was undertaken to identify suitable indicator elements for distinguishing kosa aerosols from mixtures of kosa and materials of other origin, and to investigate the mixing of kosa and anthropogenic substances in the air-mass during transport. Sixteen samples of significant kosa aerosols, minimally contaminated by kosa aerosols of different origin and containing approximately 200 μg/m3, were collected during an 11 year period starting in 2001. A backward trajectory analysis of the air masses associated with kosa events showed that, in all but two cases, they corresponded to sandstorm areas reported by the meteorological observatory. The concentrations of 15 elements, namely, Al, Ba, Ca, Cr, Fe, K, La, Mg, Mn, Na, Ni, P, Sr, Ti and V showed good correlations (r>0.7) with aerosol mass concentrations, resulting from crustal origin of these elements. The relative standard deviation (RSD) of the concentration ratios of Ba, Fe and Mn to the concentration of Al in all 16 samples was small (<10%) indicating that the proportions of these elements differed little in the sample from several different sources. In contrast, the concentrations of SO42-, NO3-, Zn and Pb showed no correlation with the aerosol mass concentration, but showed good correlations (r>0.7 in each case) with each other. The concentrations of SO42-, NO3-, Pb and Zn in one sample with low concentrations of these chemical species showed a correlation with the minimum height of the air mass estimated by a backward trajectory analysis to have passed over Chinese coastal industrial areas.
