Lanzhou sha chen bao yang pin ci xue xing zhi yu li du fen xi ji qi yu Sydney yang pin de dui bi

Measurements of magnetic properties and particle size were carried out for sand-storm samples collected in Sydney on September 23, 2009 and in Lanzhou in April 2010. The results showed that the magnetic content of Lanzhou sample was much higher than that of Sydney sample. Both samples differed slightly in mineralogy. Lanzhou sample contained maghemite, hematite and possibly hematite. Besides these minerals, Sydney sample likely contained goethite. The magnetic grain size of Sydney sample was finer than that of Lanzhou sample. As to particle-size distribution, Sydney sample showed a wide and flat curve with four peaks, while Lanzhou sample displayed a narrow curve with three peaks. The great difference in magnetic properties between storm samples and source samples and the multi-peak particle-size distribution curves were all indicative of multisource storms. Furthermore, a comparison of particle size between Lanzhou storm sample and Jiuzhoutai loess samples was made. The results showed that the increase of 1-10 μm component and the decrease of 10-20 μm component were caused by the physical and chemical weathering of unstable minerals, while the increase of 0.02-1 μm component was mainly contributed to the formation of new minerals and the weathering of unstable minerals. The certain similarity of particle size distribution curves between Lanzhou sand-storm sample and loess-paloesol sample, implied a linkage between modern storm events and geological eolian activities.