Transport of BTEX Vapours Through Granular Soils with Different Moisture Contents in the Vadose Zone

The single-ring aromatic hydrocarbons benzene, toluene, ethylbenzene and m-xylene (BTEX) are common and dangerous pollutants in subsurface environments. The diffusive transport of BTEX vapours through the unsaturated zone of the ground is a potential health hazard to humans, living in the vicinity of petroleum fuel contaminated sites. Past studies have shown that gas transport through the vadose zone can be influenced by moisture content due to variations in gaseous permeability, phase partitioning and aerobic biodegradation. In this particular study laboratory soil column experiments were employed to compare the diffusive transport of BTEX vapours through a sand layer of high moisture content, where biodegradation of BTEX compounds occurred, with diffusion through air-dried sand. The presence of a thin soil layer of high moisture content reduced the gaseous concentrations of benzene and toluene and stopped the migration of ethylbenzene and m-xylene vapours, demonstrating its efficiency as a barrier on the diffusive transport of BTEX vapours in unsaturated soil.