垃圾焚烧飞灰中重金属的污染特性

以广西和重庆某生活垃圾焚烧厂的焚烧飞灰为研究对象,研究了飞灰中重金属的化学形态、不同粒径下飞灰中重金属含量及浸出毒性。结果表明:广西垃圾焚烧飞灰中含有5种重金属,且都是以残渣态为主要存在形态;重庆垃圾焚烧飞灰中Cr以残渣态为主要存在形态,Zn、Cu和Cd以醋酸可提取态为主要存在形态,具有较大的潜在毒性,毒性较强的Pb只以醋酸可提取态和可还原提取态两种形态存在,危险性非常高,Mn以可还原提取态为主要存在形态。两地飞灰中含量较高的重金属元素都表现出向小颗粒富集趋势。随飞灰颗粒粒径的减小,各重金属浸出量基本呈增加趋势。相比之下,重庆的垃圾焚烧飞灰中Zn、Cu、Pb和Cd的含量和浸出量都高于广西飞灰。广西飞灰中各粒级的飞灰中各元素浸出量均不超标,而重庆飞灰各粒级的飞灰中Zn、Pb和Cd的浸出量严重超标,表明重庆飞灰属于典型危险废物。

Pollution Characteristics of Heavy Metals in MSWI Fly Ash

Speciation of heavy metal,heavy metal content and heavy metal leaching toxicity under various size fractions of Guangxi and Chongqing municipal solid waste incineration(MSWI)fly ash were studied.Results showed that all 5 kinds of heavy metals in Guangxi MSWI fly ash were mainly in the residual form.Among the samples of Chongqing,Cr was mainly in the residual form,while Zn,Cu and Cd were mainly in the form of acetic acid extractable.Pb was only in the form of acetic acid extractable and reduction extractable,and Mn could be mainly in the form of reduction extractable.The heavy metal elements all have showed a tendency to the concentration of small particles.With the decrease of particle size,the leaching of heavy metals tended to increase.Amount of Zn,Cu,Pb and Cd leaching in Chongqing MSWI fly ash were higher than that of Guangxi.Leaching toxicity in various size fractions of fly ash didn’t exceed the standard in Guangxi,while those of Zn,Pb and Cd in Chongqing were seriously beyond the standard,which indicated that MSWI fly ash of Chongqing was typical hazardous waste.