Photon Factory Activity Report 2004 #22 Part B (2005)
Surface and Interface

11B/2003G231

Chemical States of Sulfur on Kosa Aerosol Particles in East Asia
Yoichi TANAKA1, Hideshi ISHII1, Teruo TANABE*1, Jun KAWAI1, Yoshinori KITAJIMA2
1
Dept. of Materials Sci. & Eng., Kyoto Univ., Yoshida, Sakyo-ku, Kyoto 606-8501, Japan
2
KEK-PF, Tsukuba, Ibaraki 305-0801, Japan
Introduction
Kosa (yellow sand) is transported in form of aerosol by
the westerlies from the desert and loess areas of interior
China to eastern Asia or the Pacific region. Heavy metalsand various toxic materials such as sulfuric acid areadsorbed on the aerosol particles during the flight andcause damage on human health, animals or vegetation. Toelucidate the chemical states of sulfur adsorbed on theKosa aerosol particles, it was intended in this study toperform XAFS spectrometry of the aerosol particles withsimultaneous measurements of total electron yield (TEY)and X-ray fluorescence yield (XFY).

to adhesion of atmospheric pollutants during thetransportation over the industrialized area in China.

Experimental
Two types of free-fall Kosa aerosol particles wereobtained at Shenyang and Harbin of China in 2003 and2004. Two standard Kosa samples CJ-1 and CJ-2, whichwere prepared by NIES, Tsukuba, Japan, were used as
reference samples, in addition to the sand particles ofTaklamakan Desert. Measurements of XAFS spectra werecarried out at BL-11B of Photon Factory. The beamenergy ranged from 2450 to 2550 eV, by 0.2 eV steps, 1
sec per step, using a Ge (111) monochromator crystal.
-4
The pressure in the sample chamber was kept at 10 Pa
during the measurement.
Results and Discussion
The obtained spectra of samples are shown in Fig. 1(TEY) and (XFY). It should be noted that the intensities
were divided by the incident beam intensity, which wasdetected as drain current when penetrating the Ni mesh,to avoid the spectral peak emergence due to fluctuation ofincident beam intensity. Spectral peaks in Fig. 1 indicate
absorption spectra profiles of the representative sulfur
222derivatives, determining S , SO3 , SO4 absorption edges
as 2470.6, 2477.1, 2481.4 eV respectively. The spectrumof Harbin aerosol has a distinct absorption peak near 2481
eV for both TEY and XFY, indicating that sulfur mainly
2exists in form of SO4 for both nano- to micrometer-depth
from the particle surface. The spectrum of the Shenyang
aerosol also exhibits peaks near 2481 eV in both TEY andXFY but a relatively small peak is additionally observedin the TEY spectrum near 2477 eV, which indicates that
2the distribution of SO3 is limited only in nanometerdepth. On the other hand, spectra of Taklamakan and CJ2 samples have a smaller peak near 2481 eV in TEY
2diagram, indicating the existence of SO4 at the nanometer level surface. No peaks were found for CJ-1. Thus
it was concluded that sulfur in Kosa aerosol mainly exists
2in form of SO4 , one of the most oxidized condition, due

Figure 1:XAFS spectra of Kosa aerosol samples; XFY(upper) and TEY(lower).
References[1] J.Kawai et al. Spectrochim. Acta B 49, 739 (1994).
[2] J.Kawai et al., Anal. Chem. 67, 1526 (1995).
* teruo.tanabe@materials.mbox.media.kyoto-u.ac.jp

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