Abstract:In China, the main pathway for the consumption of municipal solid waste (MSW) incineration fly ash has long been through stabilization pre-treatment followed by landfill disposal in MSW landfill sites. The potential environmental risk of heavy metals contained in stabilized fly ash, which has a long span of landfill years and a huge stock, under the influence of complex landfill environments, is a prominent challenge that future landfill management needs to face. Based on the background of "non-standard co-landfill of fly ash and raw MSW", this paper focuses on analyzing the effects of external environmental factors such as pH, DOM, ORP, salinity, CO2 atmosphere and stabilizing agents, particle size on the leaching of heavy metals in landfill fly ash. The impact patterns of different influencing factors and the interaction effects between each factor were discussed, and their potential environmental risks were evaluated. It can be pointed out that the interaction between the landfill leachate qualities and internal environmental factors on the long-term leaching behavior and environmental risks of heavy metals in the stock fly ash in landfill sites deserves further research. Therefore, the implementation of the "exemption clause" in the historical landfill disposal of MSW incineration fly ash in China has not changed the hazardous waste attributes of fly ash itself. In the future, it is necessary to strengthen the collaborative attention to the hazardous and resource attributes of a large amount of stabilized fly ash stored in landfills.