A two-dimensional semi-analytical model for tracer gas injection and transport in a landfill system

Abstract

Identifying the location of a leakage is the very first basic step for preventing the escape of landfill gas and leachate from defects. A two-dimensional semi-analytical model is presented for the transport of tracer gas injection in landfills. Tracer gas transport in the landfill cover, liner and waste body is considered. Constant concentration and flux boundary conditions for the injection well are adopted. The proposed approach can be used for leakage detection of the barrier systems in landfills. It is shown that the air-filled porosities of the waste body and the upper cover have a great influence on the tracer gas emission flux on the cover system while the effect of air-filled porosity of the bottom liner can be neglected. The transport mechanism of the tracer gas in the waste body can have a significant impact on the behaviour of the tracer gas in the upper cover and the bottom liner. SF6 emission flux increases with decreasing of the thickness of the upper cover and increasing thickness of the waste body. It is proposed that a constant flux injection boundary should be adopted in the field for leakage detection. The analytical model presented here is a relatively simplified model, which can be used for the validation and guidance of field tracer test.