| Three levels of class F fly ash and slag of thermal power plant were digested with EPA Method 3051 and microwave,and extracted with three solutions of different pH to simulate the landfill leachate,the neutral and acid rain.The contents of heavy metals (Cr,Mn,Ni,Cu,Zn,Cd and Pb) were determined by the inductively coupled plasma mass spectrometry (ICP-MS) to analyze their distribution characteristics and leaching toxicity.The results showed that the mean contents of Cr,Mn,Ni,Cu,Zn and Pb in three levels of fly ash were 35.75, 148.06, 19.64, 17.95, 32.95 and 14.95 μg·g-1,respectively,which were lower than Tianjin soil environmental background value.However,Cd content(0.182 μg·g-1) exceeded the background value.There were no significant difference in the distribution of three levels of fly ash,but the concentrations were higher than those of heavy metals in slag.On the contrary,the content of Mn showed the obvious distribution characteristics (fly ash Ⅰ < fly ash Ⅱ < fly ash Ⅲ< slag),and it increased as the particle size increased.Simulation results of neutral and acid rain on the fly ash and slag extraction showed that extractability of Mn,Ni,Cu,Zn and Pb were quite low(<0.11%),but Cr and Cd showed higher extractability.In the simulation experiment of landfill leachate extraction,the extractability of Cd increased significantly,the leaching rate of Cd in fly ash Ⅰ,Ⅱ,Ⅲ and slag were 26.6%, 17.7%, 14.4% and 8.3%,respectively.The wet ash and slag removal can induce the leaching of Cd,which had some environmental risks. |
