重庆市垃圾焚烧飞灰粒径分布及重金属形态分析

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

采用筛分法研究了重庆市生活垃圾焚烧飞灰中的粒径分布,分析了各粒径颗粒中Pb、Cd、Zn、Cu、Mn、Ni和Cr等重金属的总量,并利用Tessier五步连续提取法对不同粒径飞灰中各重金属的化学形态进行了分析.结果表明,90%以上的飞灰粒径小于250μm,其中粒径为149—250μm的颗粒最多,约占总量的50%.除Ni之外,其它重金属的含量随粒径的减小呈先减小后增大的趋势.粒径小于250μm颗粒中的重金属含量对飞灰中重金属含量的贡献率达到90%.飞灰中各重金属的形态分布随粒径变化规律不同,Zn、Cd、Pb、Cu的碳酸盐结合态含量略高,在重庆地区酸雨的淋溶下极易释放出来,对周围环境存在潜在威胁.

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.