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

中国のタクラマカン砂漠において採取した粒子,国立環境研究所の黄土標準試料CJ-1,及びハルピン・瀋陽において採取した黄砂降下物粒子について,通常の走査型電子顕微鏡-エネルギー分散X線分光法とともにSPring-8のシンクロトロン放射光を用いて個別粒子の元素分析を行った.また,硫黄の化学状態を明らかにするため,放射光施設KEK-PFでX線吸収スペクトルを測定した.ハルピン・瀋陽での降下物粒子は砂漠の砂粒子や黄土標準試料と同じ土壌起源の粒子であるが,SやClとともにPやTiなども検出された.SやClが検出された粒子ではすべてCaが共存していた.放射光による分析ではFe以外にCr,Mn,Niなどの重金属が感度よく検出されたが,逆に電子線プローブマイクロアナリシスでは感度よく検出されたAl,Siなど軽元素の検出感度は低かった.また工業都市の試料では硫黄はほとんど6価で,一部4価も存在した.なお,タクラマカン砂漠の表層粒子に6価の硫黄が少し検出された.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