Distribution of chemical elements and chemical states of sulfur on kosa particles fallen in Asian industrialized cities

Abstract

Sand particles of Taklamakan Desert, China loess sample CJ-1 prepared by NIES and kosa particles that had fallen in the cities of Harbin and Shenyang were characterized in terms of the distribution of contained elements by the "synchrotron EDX" method at SPring-8, in addition to the familiar SEM-EDX method. To examine the chemical valence state of sulfur on these particles, the X-ray absorption spectra were measured at the KEK-PF in Tsukuba. The kosa particles of Harbin and Shenyang were contaminated with sulfur, chlorine, phosphor or titanium, although the major components of silicon, aluminum and iron were similar to the reference samples of Taklamakan desert and CJ-1. All of the kosa particles in which sulfur or chlorine were detected contained calcium. A comparison of synchrotron- and electron-excited spectra revealed that heavy metals of Cr, Mn, Fe, Ni are very sensitively detectable in synchrotron radiation, in contrast to the fact that EPMA seems to have a superiority in the detection of light elements: Mg, Al, Si. Sulfur on the particles of Harbin or Shenyang is mainly in the form of the 6+ valence; the 4+ valence state of sulfur was also found on a sample of Shenyang. Sulfur of the 6+ valence state was weakly detected in the sand of Taklamakan desert maybe in the adsorbed form on the surface of particles.