Investigation of preferential flow and leakage location in landfill: A field tracer test and numerical analysis

A field tracer test was carried out in an uncontrolled valley-type landfill. Fluorobenzoic acid (FBA) was firstly used in the landfill to study the preferential flow. A two-dimensional advection-diffusion dual-porosity model coupled with indirect streamline and terrain conditions was developed to analyze the breakthrough curves. The leakage location method was proposed based on the volume proportion of fracture domain in the total domain w_f distribution. The results show that FBA is an excellent tracer due to its lower dosage, high peak concentration and long residence time at monitoring wells. The tracer transport depth and length can reach up to 15 m and 86.3 m, respectively. Diffusion drive the tracer flow to upstream with high velocity. The anisotropy value is mainly influenced by the effect of compression rather than the waste age. The horizontal preferential flows dominate in the landfill. The preferential flow is observed to be more obvious with the increasement of the depth due to the increasement of the content of 2D particles. The leakage probability of different part in the landfill is determined by the proposed dual-porosity model and leakage location method. The proposed leakage detection method can be used for active landfills, especially those with thick layers of wastes. It can also provide scientific guidance for the design of subsequent vertical barrier for the landfills.