Non aqueous phase liquid

Non-aqueous phase liquids or NAPLs are liquid solution contaminants that do not dissolve in or easily mix with water, like oil, gasoline and petroleum products.

NAPLs tend to contaminate soil and ground waters. Many common ground water contaminants such as chlorinated solvents and many petroleum products enter the subsurface in nonaqueous-phase solutions. They do not mix readily with water and therefore flow separately from ground water.

If the NAPL is denser than water, like trichloroethylene, it is called DNAPL and will tend to sink once it reaches the water table. If it is lighter, like gasoline, it is called LNAPL and will tend to float on the water table. DNAPL penetrates below the water table like ice cubes in a glass of water.