The distribution in different particle size of municipal solid waste incinerator fly ash were studied by sieve method, and the heavy metal content and speciation of Pb, Cd, Zn, Cu, Mn, Ni and Cr in different particles were analyzed by Tessier's sequential chemical extraction procedure. The results showed that more than 90% of fly ash's particle size was less than 250µm, while particles of 150~250µm accounted for about 50%. Content of heavy metals were decreased first and then increased with decreasing particle sizes except Ni. Concentration of heavy metals in fractions of <250µm takes up 90% of the total. With the changing of the fractions of fly ash particles, the content of speciation varies from different types of heavy metals. It was also found that the elements such as Zn, Cd, Pb and Cu have exhibited a remarkable content in the form of exchangeable cations. They would be released into the environment under acid rains especially in Chongqing, which would result in a potential risk to the environment.
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