PARTICLE SIZE DISTRIBUTION AND SPECIATION ANALYSIS OF HEAVY METALS IN MUNICIPAL SOLID WASTE INCINERATION FLY ASH IN CHONGQING,CHINA

The distribution of particle size in municipal solid waste incinerator (MSWI) fly ash was analyzed by sieve method,and the heavy metal content and speciation of Pb,Cd,Zn,Cu,Mn,Ni and Cr in different size particles were analyzed by Tessier's sequential chemical extraction procedure.The results showed that more than 90% of fly ash particles were smaller than 250μm,while particles of 150—250μm accounted for about 50%. Content of heavy metals 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.The dependance of metal speciation on particle size differs among heavy metals. It was also found that the exchangeable cations of Zn,Cd,Pb and Cu were comparably high. They would be released into the environment under acid rains especially in Chongqing,which has potential risk to the environment.