Spring Dust Particles in Beijing: Mineralogy and Sources
Speaker:Prof. Shao Long Yi
Chairman of Deaprtment of Resources and earth Sciences
China University of Mining and Technology, Beijing, China
Date & Time:25 Jul 2008 (Friday) 16:30 - 17:30
Venue:N401

Abstract

A severe Asian Dust Storm (ADS) event occurred on April 16-17th, 2006 in northern China. The mineral compositions of dust samples were analyzed using X-ray diffraction (XRD). The results indicated that dust particles of the "2006.4.17" dust storm were dominated by quartz (37.4%) and clay (32.9%), followed by plagioclase (13.7%), with small amounts of calcite, K-feldspar, dolomite, hornblende and gypsum (all less than 10%). The clay fractions with diameter less than 2µm were separated from the dust storm particles and were further analyzed by XRD. The result revealed that the clay species were mainly illite/smectite mixed layers (49%) and illite (34%), with small amount of kaolinite (8%) and chlorite (9%).

In order to evaluate feasibility of using the mineralogy to trace sources of dust particles, the XRD results of the ?006.4.17?dustfall particles were compared with the dust particles over past years. The results confirmed that the finer dust particles represented by the ADS PM10 displayed a smaller quartz:clay ratio than the dustfall particles. The dust storm particles, either from the ADS PM10 or from the "2006.4.17" dustfall, showed a lower level of gypsum (0.3%) and a lower gypsum:clay ratio (0.09), compared with the non-dust storm dustfall particles. Similar trends were found for the dolomite and the dolomite:clay ratios, implying that dolomite could be used to distinguish between the dust contributions from local and non-local sources. Moreover, the two dustfall samples had a relatively lower level of illite/smectite mixed layers (I/S) and a relatively higher level of illite than airborne PM10s, implying that the clay fraction of dustfall particles tend to be enriched with illite.