| Atmospheric dust particles link the atmosphere with the lithosphere and hydrosphere in a variety of complex and interacting ways, therefore, study on atmospheric dust contribute much to environment. It is suggested that the effects of atmospheric dust are controlled not only by the process related to climate but also by the source region. Recently, a new-type dust storm (so-called alkaline dust-storm or ADS) was recognized in the wide areas of North-eastern (NE) China with link to such a special type of geography source as saline land area. The alkaline dust is potentially transported to broad areas in East Asia, but the impacts on environment and public society have not been recognized because few researches on the special harmful dust are conducted. Actually, ADS has been mentioned since 1970s, in such areas as Owens Lake, Aral Sea, Sahara Desert etc., but little work on it has been done up to now. Anyway, the impacts resulted from alkaline dust have been repeatedly reported. Anticipated acid precipitation favors neutralization of alkaline dust and tends to normal or alkali in north China, Sahara Desert etc.; it is also mentioned in some researches that the alkaline dust is harmful to plants. In order to study the behaviors of ADS in Northeast Asia, monitoring and sampling works in NE China have been carried on from 2002, mainly distributed in western Songnen Plain. There are 3.73×106hm2 saline land in western Songnen Plain as one of the three widest saline lands around the world. Two types of source regions are selected as sampling sites, namely Jiangjiadian Grassland which represent degraded grassland, and Dabusu Lake which represent shrinking saline lake. Geometric size (or particle size), mineral and elemental compositions of alkaline dust aerosols collecting from two experimental sites in western Songnen Plain are investigated, employed SEM-EDX and ICP systems. The results of the measurements are positive accounting for the special behaviors of ADS by comparing its characters with normal dust storm (NDS). And convincing evidences are found mainly as follows. Correlation analysis between wind power and mass concentration suggested that alkaline dust is active even when wind power is less than 3 grade, but ADS can form only when wind power is stronger than 5 grade (29~38km/h, NDS can form also at 5 grade-wind). The seasonal variation of mass concentration suggested that ADS is easy to occur in early spring (Mar.). Unexpectedly, alkaline dust is active in summer. It is found that mass concentration of alkaline dust is effected not only by wind power, sunshine and temperature but also by source region and human. The bimodal particle size distribution of alkaline dust aerosol is mainly in ranges of 1-9μm with mode at 3 and 7μm, and it is also effected by wind condition. Normally, particle size of alkaline dust aerosol is smaller than normal dust aerosol but bigger than urban aerosol. The results of mineral and element compositions are highly compatible and both of them are help to understand the alkaline dust. Quartz, feldspar, carbonate and halite are identified as the most important minerals with the proportion of 54%, 28.3%, 4.4% and 2.7% respectively. The major elements are Ca, Na with a decreasing sequence of the main elements as Na (12.19μg/m3), Ca(4.73μg/m3), Al (4.11μg/m3), Fe(4.08μg/m3), Mg (1.59μg/m3), K(1.12μg/m3), Ba(0.33μg/m3), Zn(0.12μg/m3), Ti(0.11μg/m3), and it is compatible with the element composition of local surface soil but different from the normal dust. The relation between wind and element composition confirm that critical wind power is 5 grade. As one simple means to define the source areas and evaluate metal pollution of the alkaline dust, Enrichment Factor (EF) can be employed. It is seen that element Na has a remarkable high value during ADS (20 times of background dust conditions) and can be an index element of ADS, in contrary to decreasing of Zn, B, Cu B etc. The computation of EF indicated that the magnitude of EF values for most hazardous metals during ADS period were even smaller than none ADS counterpart. The lower EF values of these hazardous metals during ADS period may be ascribable to the excessive input of saline components like Na, Ca. EFvalue of Ca, Fe, K, Mg, Mn, Sr, V is around 1~4. As EF value of major element is almost same between two sampling sites, B, Ba, Cu and V should be considered to distinguish the two source regions for favorable difference exists between the two sampling sites. In order to understand the seasonal variation of ADS, four typical periods are found as early spring (Mar.), late spring (Apr. and May), summer (Jun. And Jul.), and autumn (Oct.). The alkaline dust aerosol mass concentration characterized for a highest peak value in March. A little different to the anticipation, another peak value is found in July and August and is compatible to the high EF value of Na in summer, which indicate that summer can form alkaline dust. Evidence is also provided from element composition as proportion of Na, K, Ca in summer is even more than in April, May and October. Obviously, high content of all elements is in samples of March, together with highest concentration of Na, well Compatible with particulate mass concentration. However, negative aspect of alkaline dust activity is deduced as relative strong influence from normal dust is there In April, May and October. As an index element to alkaline dust, Na play and most important role in early spring, then Ca take the place of it in other periods. The major elements of alkaline dust are much higher than others during all the four typical periods. The largest EF value of Na is found in early spring, then summer, autumn and late spring, with EF values as 14, 3, 2, 1 respectively. EF value of Zn, B, Ba, Cu are smaller in early spring than other periods, but B has an remarkable EF value in all periods. It is strongly suggested that wind, precipitation, temperature, moisture, sunshine should be counted in the formation of alkaline dust but contribution are different in relation to different periods. In March, it is the wind which controlled the form of alkaline dust, but temperature and sunshine take it place in July and August, then in October, low temperature, precipitation and wind result in a relatively low intensity of alkaline dust. In conclusion, the paper discussed source regions, compositions, controlling factors and seasonal variation of ADS, based on analysis of TSP mass concentration, particle size...
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