Speciation of copper in the incineration waste heat boiler (HB) and the down stream electrostatic precipitator (EP) fly ashes during the flue gas cooling down (1123 -> 473 K) has been studied by X-ray absorption near edge structural (XANES) spectroscopy in the present work. Copper species such as Cu(OH)(2) (59-67%), CUCl2 (5-12%), CuO (24-26%), and a small amount of CuS (3-4%) in fly ashes were determined by semi-quantitative analyses of the XANES spectra. In the toxicity characteristics leaching procedure (TCLP) tests, about 83 and 20% of copper were leached from the EP and HB fly ashes, respectively. The relatively high leachability of copper for the EP fly ash might be due to the fact that CuCl2 was enriched on the surfaces as observed by X-ray photoelectron spectroscopy (XPS). On the contrary, CuCl2 was mainly encapsulated in the HB fly ashes. (c) 2006 Elsevier B.V. All rights reserved.