Long‐Term Dynamics and Risk Assessment of Leachate Leakage From Municipal Landfill With Low Alkaline Fly Ash

ABSTRACT During the long‐term landfill disposal of low‐alkaline fly ash, the risk of heavy metal release increases due to carbon dioxide influence, threatening groundwater and human health. This study simulated landfill conditions using accelerated carbonation experiments and the LandSim–HELP model to evaluate the environmental risk of leachate leakage. The findings indicate that the process of carbonation notably enhanced the release of heavy metals from fly ash. Post‐carbonation, the emergence of flaky or spherical forms (such as CaCO 3 , CaSO 4 ) on the fly ash surface was observed, alongside a marked escalation in the quantity of components soluble in acid. Specifically, the concentration of Cd in the CS2 sample escalated from 0.01 to 0.55 mg/L, surpassing the permissible limit by a factor of 3.67, while the level of Pb climbed to 0.24 mg/L. Under single artificial composite liner conditions, Zn, Cd, and Pb concentrations in several samples surpassed Class III groundwater standards, with Cd's carcinogenic risk in CS2 being 45.5 times the acceptable level. Upgrading to a double liner reduced heavy metal concentrations and risks to acceptable levels. This study emphasizes the importance of enhanced impermeability measures in reducing environmental risks from stabilized fly ash disposal, offering technical support for safe landfill practices.