Attenuation of landfill leachate by UK Triassic sandstone aquifer materials 1. Fate of inorganic pollutants in laboratory columns

摘要

The attenuation of inorganic contaminants in acetogenic and methanogenic landfill leachate by calcareous and carbonate-deficient, oxide--rich Triassic sandstone aquifer materials from the English Midlands was examined in laboratory columns. Aqueous equilibrium speciation mod- elling, simple transport modelling and chemical mass balance approaches are used to evaluate the key processes and aquifer geochemical properties controlling contaminant fate. The results indicate that leachate-rock interactions are dominated by ion--exchange processes, acid-base and redox reactions and sorption/precipitation of metal species. Leachate NH_4 is attenuated by cation exchange with the aquifer sediments; however, NH# migration could be described with a simple model using retardation factors. Organic acids in the acetogenic leachate buffered the system pH at low levels during flushing of the calcareous aquifer material. In contrast, equilibrium with Al oxyhydroxide phases initially buffered pH (～ 4.5) during flushing of the carbonate-deficient sandstone with methanogenic leachate.