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Leachate from municipal solid waste landfill contains a variety of contaminants including organic acids. The subsequent vertical movement of organic acids from the landfill may reach and pollute the groundwater. Hence, the prediction of vertical movement in the unsaturated sub-surface system is essential to monitor the groundwater contamination. To achieve this, a one-dimensional numerical model has been developed to understand and forecast the transport of organic acids in unsaturated soil using a finite difference technique. This study considers acetic acid as a representative organic compound in the landfill leachate. The Richards equation is used to simulate the water content in the unsaturated soil and advection–dispersion equation is used to predict the transport of organic acid. Moreover, first-order decay coefficient is also considered during the migration of organic acid. The numerical results suggest that the transport of organic acid is strongly influenced by water content variation in the unsaturated subsurface. Further, it is also observed that the soil distribution coefficient was found to be one of the most influencing parameters, which is significantly affecting the organic acid concentration profile in the unsaturated soil. Moreover, the decay coefficient is also affecting the distribution of organic acid in the vadose zone. Overall, the numerical results show that the higher simulation time allows the concentration of organic acid to reach larger depth. Hence, there is a high probability of groundwater contamination by organic acid concentration. |
