100-year simulation of mercury emissions from landfilled stabilized mercury waste

Owing to Minamata Convention on mercury, the final disposal of mercury in environmentally safe manners will be required. Mercury disposal in landfill sites will be one of the feasible options but its environmental risk has been strongly concerned. This study built a model including hydraulic flows of rain infiltration from the top surface, unsaturated percolation in the landfill body, leachate discharge from the collection pipe, mercury transfer including diffusion and sorption, and chemical/biological reactions of mercury species to simulate mercury emissions from a mercury landfill site. Mercury emissions via landfill leachate and landfill gas to the atmosphere were simulated. The model was validated using lab-scale lysimeter experiment data. The model predicted that the major emission pathway of mercury to the environment is landfill leachate, which accounted for 99.8% of the total emissions. 83% of mercury in the leachate was estimated to be inorganic form and the rest 17% was methylmercury. The simulation suggested that mercury emission exceeds the environmental standard after the 16th year. Long-term monitoring of the leachate is necessary even when no mercury detection continues for 16 years. The model proposed that rainwater infiltration control on the top surface is very effective to reduce mercury emissions.