Abstract: The worsening groundwater pollution, particularly polluted by landfill leachate  has been receiving wide concerns from the society. The movement of leachate from Songshuling landfill was simulated with groundwater numerical simulation software GMS(Groundwater Modeling System). Based on leachate sampling results, chloridion was determined as the main  component of the pollutant which moves and spreads in the simulation. With the regional geology and hydro-geological conditions of the studied area, the sensitivity of chloridion to three main parameters, namely horizontal K, vertical K and porosity are analyzed. The results show that when the three parameters are all reduced by 50%, the chloridion concentration barely changed；while when the three parameters are magnified 2 times, the chloridion concentration are much more obviously affected by horizontal K than by vertical K and porosity. The results also proved that the models of groundwater flow and leachate movement are rational and reliable.

Key words: landfill, numerical modeling, parameter sensitivity