Abstract: A novel method that promotes upward mobilization of dense nonaqueous-phase liquid contaminants. In one embodiment, the method comprises the steps of: (1) injecting a treating agent (e.g., a polyaphron solution) comprising a light organic-phase fluid (e.g., kerosene, xylene, octane, hexane, etc.) into the Earth's subsurface, targeted within or adjacent to the dense contaminant source zone; and (2) injecting a post-flush agent comprising a polyvalent cation (e.g., Al3+, Fe3+, etc.), or similar species, once the treating agent is displaced throughout the source zone. The treating agent converts the contaminant to a density less than the density of groundwater by inducing in-situ mixing. The post-flush agent destabilizes the polyaphrons thus allowing the contaminant and the treating agent to mix.