Chemical speciation and mobility of heavy metals in municipal solid waste incinerator fly ash

摘要

Chemical speciation is a significant factor that governs the toxicity and mobility of heavy metals in municipal solid waste incinerator fly ash. Sequential extraction procedure is applied to fractionate heavy metals (Pb, Zn, Cd, Cu, and Cr) into five defined groups: exchangeable, carbonate, Fe-Mn oxide, organic, and residual fractions. The mobility of heavy metals is also investigated with the aid of toxicity characteristic leaching procedure. In the fly ash sample, Pb is primarily presented in the carbonate (51 percent) and exchangeable(20 percent) fractions; Cd and Zn mainly exist as the exchangeable(83 percent and 49 percent respectively); Cu is mostly contained in the last three fractions(totally 87 percent ); and Cr is mainly contained in the residual fraction(62 percent). Pb, Zn and Cd showed the high mobility in the investigation, thus might be of risk to the natural environment when municipal solid waste incinerator fly ash is landfilled or reutilized.