Comparison of hydrogeologic and hydrochemical conditions between two uncontrolled landfills

Abstract

Hydrogeologic and hydrochemical conditions of two uncontrolled landfills without underlying liners, leachate collection and treatment systems in Korea were compared. The landfills are located in Cheonan and Wonju cities. With similar weather conditions, spatial distribution and temporal variations of contaminants of concern and redox parameters were largely different for the two landfills. These differences are highly associated with ages and hydrogeologic settings of the landfills. Groundwater flow diverges from the Cheonan landfill while it converges to downgradient area in the Wonju landfill. Less permeable clayey silt layer or silty soil in the subsurface limited dispersion of leachate plume in the former landfill but highly permeable sandy soil with good lateral extent facilitated rapid plume dispersion in the latter landfill. In addition, hydraulic properties of the cover soil played a role in the different development of redox conditions, which resulted in significantly different concentrations of nitrates. Most problematic contaminants at downgradient wells of the landfills are ammonia and nitrate. Especially in Wonju area, high concentrations of nitrates in downgradient groundwaters exceeding the Korean drinking water standard of 10 mg/L (as NO3‐N), essentially required a mitigation measure.