Abstract
Characteristics of individual particles from a super dust storm (DS) on 20 March 2002, and those of non dust storm aerosols for Beijing (NDS) and Duolun (DL) (a desert area) are deter mined using a variety of methods. In China, typically the source of aerosols in dust storms is thought to be deserts with aluminosilicates being the main constituent particles; how ever, this does not reflect a complete analysis with our evidence indicating potential alternate dust sources along the storm's transport path. Individual particle analysis of aero sols collected from a super dust storm on 20 March 2002 in Beijing shows that among all the 14 elements measured, only S and C1 have remark able positive correlation. 82.5% of all particles measured contained both S and C1, and the relative mass percent age of S and C1 in these particles is much higher than the aver age of all particles. 62.0% of all particles contained S, C1, and Na, in which the concentration of Na is 1.4 times higher than average. PMF (Positive Matrix Factorization) analysis indicates that NaC1 and Na2SO4 are major components of these particles with S and C1 showing significant positive correlation. More over, SO4(superscript 2-) and Cl(superscript -) also show significant positive correlation in bulk aerosol analysis. XPS (X-ray Photoelectron Spectroscopy) analysis of the surface of aerosols demonstrates that concentrations of Na and S on particles from the dust storm are higher than those from non-dust storm particles in Beijing and also for particles from. It is very likely that particles enriched with S, C1, and Na is from the surface soils of dried salt-lakes and saline soils enriched with chloride and sulfate. This evidence demonstrates that besides deserts, surface soils from dry salt-lakes and saline soils of arid and semi-arid areas are also sources of particulates in dust storms over Beijing.
Highlights
Dust storms, which arise in desert and loess areas of northwestern China and sweep over the major cities of Northern China, such as Beijing, each spring, have become increasingly intense over the past few years (Cyranoski 2003).Dusts driven by strong westerly winds accompanying cold fronts are transported long distances to Korea, Japan, the Pacific Ocean, and even as far as North America (Duce et al 1983; Gao et al 1992; Mori et al 2002 etc.)
Many scientists have paid a good deal of attention to the characterization of bulk aerosols in dust storms (Zhuang et al 2001; Sun et al 2004, etc.), while few have carried out individual particle analysis, which can give much more information on heterogeneous reactions, morphometrics, and transformation during long-range transport
Where n is the atom number over the aerosol surface, I is the intensity of X-Ray Photoelectron Spectroscopy (XPS), s is the area of the element in some energy level, and Ek is the kinetic energy of the photoelectron
Summary
Dust storms, which arise in desert and loess areas of northwestern China and sweep over the major cities of Northern China, such as Beijing, each spring, have become increasingly intense over the past few years (Cyranoski 2003). Many scientists have paid a good deal of attention to the characterization of bulk aerosols in dust storms (Zhuang et al 2001; Sun et al 2004, etc.), while few have carried out individual particle analysis, which can give much more information on heterogeneous reactions, morphometrics, and transformation during long-range transport. Gao and Anderson (2001) analyzed single aerosol particles (using automated SEM) collected from Beijing, Qingdao, and Waliguan during April 1999 and revealed that the particulate matter of each region are complex, heterogeneous mixtures of soil dust with anthropogenic particles from various sources. Using image analysis Whittaker et al (2003) found that particles in dust storm samples of PM10 at Beijing are a mixture of soot, smelter pollutants, loess and gypsum. The results demonstrate that besides deserts, particulate matter was generated from the surface soils of dry salt-lakes and the saline soils of arid and semi-arid areas
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