The leachate generation of uncontrolled landfill site (Nanji-Do) is affected by the water content of unsaturated zone in waste layer, and it variates by intermittent precipitation.
To predict the water content change in waste zone, A MOC(The Method of Characteristics) model under the intermittent precipitation condition is developed, and SCS (U.S. Soil Conservation Service) method is used for the calculation of infiltration rate and runoff. Volumetric water content in unsaturated landfill predicted by MOC curve variate a little around 0.16 of porosity.
Groundwater has been monthly sampled at 13 points of Nanji-Do, and their chemical composition is analyzed. The major inorganic ions in groundwater, subsurface water and leachate are $Na^+$, $NH_4^+$, $Ca^{2+}$, $Cl^-, HCO_3^-$ and $SO_4^{2-}$.
Using a chemical equilibrium model (MINTEQA2), the chemical speciation is analyzed. The spatial change of charge composition, and the identification of chemical precipitations is studied. Major precipitations occure as the form of $MgCO_{3(S)}$. $CaCO_{3(S)}$ and $FeCO_{3(S)}$.
Considering subsurface water and runoff flow, the loading of inorganic ions to Han-River is estimated, and it turn out increase. The inorganic ion contribution to Han-River at normal water level is 0.09 and 1.37mg/L for $Ca^{2+}$ and $HCO_{3^-}$, respectively.
