Keywords: 
• MSWI fly ash /
• heavy metals /
• particle size distribution /
• leaching behavior

Abstract: In order to investigate characteristics and leaching behavior of heavy metals from municipal solid wastes incineration (MSWI) fly ash in Chongqing， China， grain size analysis and pH/liquid solid ratio/leaching time dependent experiments were conducted based on GB5085.3-2007 and USEPA-TCLP. Results indicated that the average particle size of the fly ash was 36.4 μm， the total fraction of the main heavy metals was about 1.04% in the fly ash， with Pb and Zn accounting for the highest fractions and environmental risks. Leaching toxicity of heavy metals in fly ash was investigated using the sulphuric acid and nitric acid method (GB5085.3-2007)， the results indicate that the heavy metals leaching toxicity of the fly ash was safe. However， the leaching toxicity exceeded the limited standard by USEPA-TCLP method with Pb and Cr leaching concentration of 5.750 mg/L and 1.890 mg/L， respectively. The leaching concentration increased when the leaching acid was stronger， but decreased markedly when pH>2. While the liquid solid ratio was less than 40， the leaching of the heavy metals was ascribed to the surface dissolved into the aquatic， and when the liquid solid ratio exceeded 40，it was ascribed to the dilution by the solution. The relationship between the leaching heavy metals concentration and leaching time were the remarkably positive logarithmic correlativity， and the leaching heavy metals concentration increased gradually even when the leaching time was more than 240 h. After the forecasting under the GB5085.3-2007 procedure， the result showed that the leaching concentration of Pb will reach the limit standard concentration when the leaching time was up to 35 days.