• XAFS spectroscopy;
  • selenium;
  • arsenic;
  • coal combustion;
  • fly ash;
  • X-ray-induced oxidation

Systematic changes observed in consecutive XANES spectra of selenium in samples of fly ash from a power plant in Alberta, Canada, burning subbituminous coal have been interpreted as arising from synchrotron-radiation-induced oxidation of a selenite species to selenate. It was estimated that about 15–20% of the selenite was oxidized to selenate during the 2 h exposure of the fly ash to the synchrotron beam. In contrast, the XANES spectra of arsenic (and other trace elements not documented herein) showed no variation. It is believed that this is the first time that radiation-induced changes have been observed for an element in coal-derived fly ash.